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Sample records for al-doped zno thin

  1. Elaboration and characterization of Al doped ZnO nanorod thin films annealed in hydrogen

    International Nuclear Information System (INIS)

    Research highlights: → High transparent and conductive Al doped ZnO nanorod thin films were synthesized using sol-gel spin-coating method. → Al doped ZnO nanorod thin films can be got by annealing in hydrogen rather than in air. → Crystal orientation of Al doped ZnO thin film has been raised. → Resistivity of films has been remarkably reduced by annealing in hydrogen. - Abstract: ZnO thin films doped with Al concentrations of 1.0, 2.0, 3.0, 4.0, 5.0 at% were prepared by a sol-gel spin-coating method on glass substrates and respectively annealed at 550 deg. C for 2 h in hydrogen and air. The X-ray diffraction and selected-area electron diffraction results confirm that the Al doped ZnO thin films are of wurtzite hexagonal ZnO. The scanning electron microscope results indicate that the Al doped ZnO nanorod thin films can be got by annealing in hydrogen rather than in air. The optical properties reveal that the Al doped ZnO thin films have obviously enhanced transmittance in the visible region. The electrical properties show that the resistivity of 1.0 at% Al doped ZnO thin films has been remarkably reduced from 0.73 Ω m by annealing in air to 3.2 x 10-5 Ω m by annealing in hydrogen. It is originated that the Al doped ZnO nanorod thin films annealed in hydrogen increased in electron concentration and mobility due to the elimination of adsorbed oxygen species, and multicoordinated hydrogen.

  2. Pulsed laser deposited Al-doped ZnO thin films for optical applications

    OpenAIRE

    Gurpreet Kaur; Anirban Mitra; K.L. Yadav

    2015-01-01

    Highly transparent and conducting Al-doped ZnO (Al:ZnO) thin films were grown on glass substrates using pulsed laser deposition technique. The profound effect of film thickness on the structural, optical and electrical properties of Al:ZnO thin films was observed. The X-ray diffraction depicts c-axis, plane (002) oriented thin films with hexagonal wurtzite crystal structure. Al-doping in ZnO introduces a compressive stress in the films which increase with the film thickness. AFM images reveal...

  3. Formation of Al-doped ZnO thin films on glass by sol-gel process and characterization

    Science.gov (United States)

    Shahid, M. U.; Deen, K. M.; Ahmad, A.; Akram, M. A.; Aslam, M.; Akhtar, W.

    2016-02-01

    In this study, pure ZnO and Al-doped ZnO thin films were developed on glass by sol-gel process followed by drying and annealing in air at 170 and 400 °C, respectively. The surface morphology and structural characteristics were determined through scanning electron microscopy, atomic force microscopy and X-ray diffraction. The Fourier transform infrared spectroscopy validated the formation of Al-doped ZnO film on glass substrate. It was evaluated that 1 at% aluminum (Al) doping in ZnO film showed low electrical resistivity and higher charge carrier concentration due to uniformly dispersed regular shape crystallites as compared to pure ZnO and 2 at% `Al'-doped thin films.

  4. Pulsed laser deposited Al-doped ZnO thin films for optical applications

    Directory of Open Access Journals (Sweden)

    Gurpreet Kaur

    2015-02-01

    Full Text Available Highly transparent and conducting Al-doped ZnO (Al:ZnO thin films were grown on glass substrates using pulsed laser deposition technique. The profound effect of film thickness on the structural, optical and electrical properties of Al:ZnO thin films was observed. The X-ray diffraction depicts c-axis, plane (002 oriented thin films with hexagonal wurtzite crystal structure. Al-doping in ZnO introduces a compressive stress in the films which increase with the film thickness. AFM images reveal the columnar grain formation with low surface roughness. The versatile optical properties of Al:ZnO thin films are important for applications such as transparent electromagnetic interference (EMI shielding materials and solar cells. The obtained optical band gap (3.2–3.08 eV was found to be less than pure ZnO (3.37 eV films. The lowering in the band gap in Al:ZnO thin films could be attributed to band edge bending phenomena. The photoluminescence spectra gives sharp visible emission peaks, enables Al:ZnO thin films for light emitting devices (LEDs applications. The current–voltage (I–V measurements show the ohmic behavior of the films with resistivity (ρ~10−3 Ω cm.

  5. Characteristics of Al-doped ZnO thin films obtained by ultrasonic spray pyrolysis: effects of Al doping and an annealing treatment

    International Nuclear Information System (INIS)

    Transparent conducting Al-doped ZnO thin films were prepared on silica glass substrates by an ultrasonic spray pyrolysis method. The effects of Al doping and an annealing treatment on electrical and optical properties of ZnO thin films were investigated. Zinc acetate dihydrate, 2-methoxyethanol and aluminum chloride were used as a starting material, a solvent and a dopant source, respectively. The electrical conductivity of ZnO films was improved by Al doping and by annealing in a reducing atmosphere. The minimum electrical resistivity was obtained in the 3 at.% Al-doped film annealed at 500 deg. C in nitrogen with 5% hydrogen and its value was 1.71x10-2 Ω cm. The average optical transmittance of all films, regardless of a doping concentration and an annealing condition, was higher than 80% in the visible range. The optical direct band gap of films was dependent on the amount of a dopant and the annealing treatment in a reducing atmosphere. The optical direct band gap value of 3 at.% Al-doped films annealed at 500 deg. C in nitrogen were 3.33 eV

  6. Ultraviolet Sensing by Al-doped ZnO Thin Films

    International Nuclear Information System (INIS)

    We report the fabrication and characterization of an ultraviolet photoconductive sensing by using Al-doped ZnO films. Undoped ZnO, 1 at.% and 2 at% of Al were prepared on quartz glass by sol gel method with annealing temperature of 500 degree Celsius for 1 hour. The presence of spherical shaped nanoparticles were detected for undoped ZnO by using FESEM. The absorption edge shifted to a lower wavelength by doping with Al and excitonic peak can be observed. The band gap values increased by adding Al. I-V curves reveal an improvement in electrical properties when the samples are illuminated by ultraviolet (UV) light with a wavelength of 365 nm. At 1 at.% of Al, the film have a larger increment in photocurrent response when illuminated with UV light compared to undoped ZnO and 2 at.% Al. The thin films have a longer recovery time than response time. (author)

  7. Laser induced photoconductivity in sol–gel derived Al doped ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Eskandari, F.; Ranjbar, M., E-mail: ranjbar@cc.iut.ac.ir; Kameli, P.; Salamati, H.

    2015-11-15

    In this paper Al doped ZnO (AZO) thin films with 0, 3, 6 and 12 at. % Al concentration were prepared by sol–gel method on glass substrates. The deposited films were annealed at different temperatures of 300, 350, 400, 450 and 500 °C for 1 h in air. X-ray diffraction (XRD) showed wurtzite crystalline structure for the films annealed above 400 °C. The films were subsequently irradiated by beams of excimer (KrF, λ = 248 nm) laser. The evolution of crystal structure, surface morphology and optical properties were studied using XRD, filed emission scanning electron microscope (FE-SEM) and UV–Vis spectrophotometer, respectively. Real-time measurement of electrical conductivity during laser irradiation showed a transient or persistent photoconductivity effect. The effect of laser energy on this photoconductivity was also investigated. Based on the observed photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS), the observed photoconductivity effect was described. - Highlights: • AZO (0–12 at. % Al) films were prepared by sol–gel method and annealed at different temperatures. • Excimer laser (λ = 248 nm) irradiation leads to improvement of crystalline structure. • Average optical transmission doesn't change and optical gap decreases by irradiation. • Photoconductivity was investigated by real-time measurement of electrical resistance. • Sample of 6% Al annealed at 450–500 °C showed the best photoconductivity effect.

  8. Amorphous-nanocrystalline Al doped ZnO transparent conducting thin films

    Energy Technology Data Exchange (ETDEWEB)

    Diez-Betriu, X., E-mail: xdiezbetriu@icmm.csic.es [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Cantoblanco 28049 Madrid (Spain); Jimenez-Rioboo, R.; Marcos, J. Sanchez-; Cespedes, E.; Espinosa, A.; Andres, A. de [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Cantoblanco 28049 Madrid (Spain)

    2012-09-25

    Highlights: Black-Right-Pointing-Pointer Al- doped ZnO films by RF- sputtering as amorphous TCO. Black-Right-Pointing-Pointer Structural characterization confirms amorphous-nanocrystalline nature of samples. Black-Right-Pointing-Pointer Optical gap dependence on substrate and grain size. Black-Right-Pointing-Pointer Resistivity correlates to the optical bandgap. - Abstract: Al-doped ZnO films have been deposited at room temperature by means of RF sputtering under different conditions and subjected to annealing treatments looking for amorphous Transparent Conducting Oxide (TCO) films in the search for their integration into the emerging area of the flexible electronics. Structural studies have been performed as well as optical and electrical characterization. Spectroscopic ellipsometry has been used for the determination of the optical gap for films grown on Si and the films thickness. The amorphous fraction of the films (up to 86%) depends on the substrate and RF power but not on the annealing temperature up to 600 Degree-Sign C for glass substrates. The resistivity is found to be independent of the amorphous degree and correlates to the optical bandgap which presents three regimes depending on the annealing temperature.

  9. Structures and properties of the Al-doped ZnO thin films prepared by radio frequency magnetron sputtering

    International Nuclear Information System (INIS)

    Al-doped ZnO thin films were deposited by radio frequency magnetron sputtering using a ZnO target with 2 wt.% Al2O3. The structures and properties of the films were characterized by the thin film X-ray diffraction, high resolution transmission electron microscopy, Hall system and ultraviolet/visible/near-infrared spectrophotometer. The Al-doped ZnO film with high crystalline quality and good properties was obtained at the sputtering power of 100 W, working pressure of 0.3 Pa and substrate temperature of 250 deg. C. The results of further structure analysis show that the interplanar spacings d are enlarged in other directions besides the direction perpendicular to the substrate. Apart from the film stress, the doping concentration and the doping site of Al play an important role in the variation of lattice parameters. When the doping concentration of Al is more than 1.5 wt.%, part of Al atoms are incorporated in the interstitial site, which leads to the increase of lattice parameters. This viewpoint is also proved by the first principle calculations.

  10. Crystal Structure and Optical Properties of Al-Doped ZnO Large-Area Thin Films Using 1500 mm Dual Cylindrical Cathodes.

    Science.gov (United States)

    Lee, JinJu; Ha, Jong-Yoon; Yim, Haena; Choi, Won-Kook; Choi, Ji-Won

    2015-11-01

    The large-area Al-doped ZnO thin films are successfully deposited at room temperature on polycarbonate substrate using a 1500 mm dual cylindrical cathodes sputtering system. Those thin films have smooth surfaces (RMS: 9.6 nm) and lower thicknesses deviation (Uniformity: 98.6%) despite of high RF power. The optical transmittance properties of 3.13 wt% Al doped ZnO thin films have above 85% in visible region. A dual cylindrical cathodes sputtering system can fabricate transparent electrode on flexible electronic devices at room temperature for mass production of 6th generation solar cell and display industry. PMID:26726519

  11. Sputtered Al-doped ZnO transparent conducting thin films suitable for silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Ben Ayadi, Z., E-mail: Zouhaier.BenAyadi@fsg.rnu.tn [Laboratoire de Physique des Matériaux et des Nanomatériaux appliquée à l' Environnement, Université de Gabès, Faculté des Sciences de Gabès, Cité Erriadh Manara Zrig, 6072 Gabès (Tunisia); Mahdhi, H. [Laboratoire de Physique des Matériaux et des Nanomatériaux appliquée à l' Environnement, Université de Gabès, Faculté des Sciences de Gabès, Cité Erriadh Manara Zrig, 6072 Gabès (Tunisia); Djessas, K. [Laboratoire Procédés, Matériaux et Energie Solaire (PROMES-CNRS), TECNOSUD, Rambla de la Thermodynamique, 66100 Perpignan (France); Université de Perpignan Via Domitia, 52 Avenue Paul Alduy, 68860, Perpignan Cedex9 (France); Gauffier, J.L. [Département de Génie Physique, INSA de Toulouse, 135 Avenue de Rangueil, 31077 Toulouse cedex 4 (France); and others

    2014-02-28

    Highly transparent conducting Al-doped zinc oxide (AZO) thin films have been grown onto p-type porous silicon substrates by RF-magnetron sputtering at room temperature using aluminum doped nanocrystalline powder. The obtained AZO films were polycrystalline with a hexagonal wurtzite structure and preferentially oriented in the (002) crystallographic direction. The films are highly transparent in the visible wavelength region with a transmittance higher than 85% and an electrical resistivity of 1.56 × 10{sup −4} Ω·cm was obtained at room temperature. On the other hand, we have studied the position of the p–n junction involved in the In{sub 2}O{sub 3}:SnO{sub 2}/(n)AZO/Si(p) structure, by electron-beam induced current technique. Current density–voltage characterizations in dark and under illumination were also investigated. The cell exhibits an efficiency of 5%. - Highlights: • Al-doped zinc oxide (AZO) thin films were grown by RF-magnetron sputtering. • AZO nanopowder compacted target was prepared by a sol–gel method. • AZO thin films are polycrystalline and have preferred orientation along c-axis. • We report a photovoltaic effect in Si(p)/porous silicon/AZO heterostructure. • The cell exhibits an efficiency of 5%.

  12. Chemical and electronic interface structure of spray pyrolysis deposited undoped and Al-doped ZnO thin films on a commercial Cz-Si solar cell substrate

    Energy Technology Data Exchange (ETDEWEB)

    Gabas, M.; Ramos-Barrado, J.R. [Dpto. de Fisica Aplicada I, Lab. de Materiales y Superficies, Universidad de Malaga 29071 Malaga (Spain); Barrett, N.T. [CEA DSM/IRAMIS/SPCSI, CEA Saclay, 91191 Gif sur Yvette (France); Gota, S. [Laboratoire Leon Brillouin, UMR 012 CEA-CNRS CEA Saclay, 91191 Gif sur Yvette (France); Rojas, T.C. [Instituto de Ciencia de Materiales de Sevilla, CSIC, Americo Vespucio 49, 41092 Sevilla (Spain); Lopez-Escalante, M.C. [Isofoton S.A., Parque Tecnologico de Andalucia, Severo Ochoa, 50, 29590 Malaga (Spain)

    2009-08-15

    We have studied differences in the interface between undoped and Al-doped ZnO thin films deposited on commercial Si solar cell substrates. The undoped ZnO film is significantly thicker than the Al-doped film for the same deposition time. An extended silicate-like interface is present in both samples. Transmission electron microscopy (TEM) and photoelectron spectroscopy (PES) probe the presence of a zinc silicate and several Si oxides in both cases. Although Al doping improves the conductivity of ZnO, we present evidence for Al segregation at the interface during deposition on the Si substrate and suggest the presence of considerable fixed charge near the oxidized Si interface layer. The induced distortion in the valence band, compared to that of undoped ZnO, could be responsible for considerable reduction in the solar cell performance. (author)

  13. Improving the uncommon (110) growing orientation of Al-doped ZnO thin films through sequential pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Coman, Tudor [Faculty of Physics, “Al. I. Cuza” University, 11 Carol I Blvd., Iasi 700506 (Romania); Ursu, Elena Laura [Centre of Advanced Research in Bionanoconjugates and Biopolymers, “Petru Poni” Institute of Macromolecular Chemistry, 41 A Grigore Ghica Voda Alley, Iasi 700487 (Romania); Nica, Valentin; Tiron, Vasile [Faculty of Physics, “Al. I. Cuza” University, 11 Carol I Blvd., Iasi 700506 (Romania); Olaru, Mihaela; Cotofana, Corneliu [Polymer Materials Physics Laboratory, “Petru Poni” Institute of Macromolecular Chemistry, 41 A Gr. Ghica Voda Alley, Iasi 700487 (Romania); Dobromir, Marius [Faculty of Physics, “Al. I. Cuza” University, 11 Carol I Blvd., Iasi 700506 (Romania); Coroaba, Adina [Centre of Advanced Research in Bionanoconjugates and Biopolymers, “Petru Poni” Institute of Macromolecular Chemistry, 41 A Grigore Ghica Voda Alley, Iasi 700487 (Romania); Dragos, Oana-Georgiana; Lupu, Nicoleta [National Institute of Research and Development for Technical Physics, 47 Mangeron Blvd., Iasi 700050 (Romania); Caltun, Ovidiu Florin [Faculty of Physics, “Al. I. Cuza” University, 11 Carol I Blvd., Iasi 700506 (Romania); Ursu, Cristian, E-mail: cristian.ursu@icmpp.ro [Polymer Materials Physics Laboratory, “Petru Poni” Institute of Macromolecular Chemistry, 41 A Gr. Ghica Voda Alley, Iasi 700487 (Romania)

    2014-11-28

    High quality Al-doped ZnO (AZO) films with uncommon (110) orientation are obtained on amorphous substrate by using Sequential Pulsed Laser Deposition technique. The dependence of the structural, optical and electrical properties with dopant concentration and oxygen deposition pressure was investigated systematically. We note a transition from the (002) preferential orientation of crystallites to an uncommon (110) orientation due to a combined effect of doping concentration and deposition pressure decreasing. For constant deposition pressure of 5 Pa the film crystallinity is changed from preferential (002) to polycrystalline when increasing dopant concentration. For the maximum dopant concentration that we have investigated (i.e., 4.4% at.) structural properties of AZO films are changed from a polycrystalline phase to a (110) preferential orientation when the deposition pressure decreases. This uncommon growth mode is accompanied by a change of the morphology from a densely packed granular structure to a more rarefied one. Moreover, the band gap widens up to 3.88 eV and the electrical resistivity drops to 5.4 × 10{sup −2} Ω cm. The structural changes were attributed to two mechanisms: a first one, responsible for the (002) phase suppression as a consequence of aluminum ion bombardment during the doping process and, a second one, in charge with (110) phase growth as the diffusion rates of zinc and oxygen atoms are affected by the dopant incorporation and by the decrease of deposition pressure. - Highlights: • Sequential PLD (SPLD) of (110) Al-doped ZnO thin films on amorphous substrate • Highly c-axis oriented films with high transparency and low resistivity • Fine tuning of the dopant concentration through SPLD method.

  14. Improving the uncommon (110) growing orientation of Al-doped ZnO thin films through sequential pulsed laser deposition

    International Nuclear Information System (INIS)

    High quality Al-doped ZnO (AZO) films with uncommon (110) orientation are obtained on amorphous substrate by using Sequential Pulsed Laser Deposition technique. The dependence of the structural, optical and electrical properties with dopant concentration and oxygen deposition pressure was investigated systematically. We note a transition from the (002) preferential orientation of crystallites to an uncommon (110) orientation due to a combined effect of doping concentration and deposition pressure decreasing. For constant deposition pressure of 5 Pa the film crystallinity is changed from preferential (002) to polycrystalline when increasing dopant concentration. For the maximum dopant concentration that we have investigated (i.e., 4.4% at.) structural properties of AZO films are changed from a polycrystalline phase to a (110) preferential orientation when the deposition pressure decreases. This uncommon growth mode is accompanied by a change of the morphology from a densely packed granular structure to a more rarefied one. Moreover, the band gap widens up to 3.88 eV and the electrical resistivity drops to 5.4 × 10−2 Ω cm. The structural changes were attributed to two mechanisms: a first one, responsible for the (002) phase suppression as a consequence of aluminum ion bombardment during the doping process and, a second one, in charge with (110) phase growth as the diffusion rates of zinc and oxygen atoms are affected by the dopant incorporation and by the decrease of deposition pressure. - Highlights: • Sequential PLD (SPLD) of (110) Al-doped ZnO thin films on amorphous substrate • Highly c-axis oriented films with high transparency and low resistivity • Fine tuning of the dopant concentration through SPLD method

  15. Highly transparent and conductive Al-doped ZnO nanoparticulate thin films using direct write processing.

    Science.gov (United States)

    Vunnam, S; Ankireddy, K; Kellar, J; Cross, W

    2014-05-16

    Solution processable Al-doped ZnO (AZO) thin films are attractive candidates for low cost transparent electrodes. We demonstrate here an optimized nanoparticulate ink for the fabrication of AZO thin films using scalable, low-cost direct write processing (ultrasonic spray deposition) in air at atmospheric pressure. The thin films were made via thermal processing of as-deposited films. AZO films deposited using the proposed nanoparticulate ink with further reducing in vacuum and rf plasma of forming gas exhibited optical transparency greater than 95% across the visible spectrum, and electrical resistivity of 0.5 Ω cm and it drops down to 7.0 × 10(-2) Ω cm after illuminating with UV light, which is comparable to commercially available tin doped indium oxide colloidal coatings. Various structural analyses were performed to investigate the influence of ink chemistry, deposition parameters, and annealing temperatures on the structural, optical, and electrical characteristics of the spray deposited AZO thin films. Optical micrographs confirmed the presence of surface defects and cracks using the AZO NPs ink without any additives. After adding N-(2-Aminoethyl)-3-aminopropylmethyldimethoxy silane to the ink, AZO films exhibited an optical transparency which was virtually identical to that of the plain glass substrate. PMID:24763438

  16. Highly transparent and conductive Al-doped ZnO nanoparticulate thin films using direct write processing

    International Nuclear Information System (INIS)

    Solution processable Al-doped ZnO (AZO) thin films are attractive candidates for low cost transparent electrodes. We demonstrate here an optimized nanoparticulate ink for the fabrication of AZO thin films using scalable, low-cost direct write processing (ultrasonic spray deposition) in air at atmospheric pressure. The thin films were made via thermal processing of as-deposited films. AZO films deposited using the proposed nanoparticulate ink with further reducing in vacuum and rf plasma of forming gas exhibited optical transparency greater than 95% across the visible spectrum, and electrical resistivity of 0.5 Ω cm and it drops down to 7.0 × 10−2 Ω cm after illuminating with UV light, which is comparable to commercially available tin doped indium oxide colloidal coatings. Various structural analyses were performed to investigate the influence of ink chemistry, deposition parameters, and annealing temperatures on the structural, optical, and electrical characteristics of the spray deposited AZO thin films. Optical micrographs confirmed the presence of surface defects and cracks using the AZO NPs ink without any additives. After adding N-(2-Aminoethyl)-3-aminopropylmethyldimethoxy silane to the ink, AZO films exhibited an optical transparency which was virtually identical to that of the plain glass substrate. (papers)

  17. Highly transparent and conductive Al-doped ZnO nanoparticulate thin films using direct write processing

    Science.gov (United States)

    Vunnam, S.; Ankireddy, K.; Kellar, J.; Cross, W.

    2014-05-01

    Solution processable Al-doped ZnO (AZO) thin films are attractive candidates for low cost transparent electrodes. We demonstrate here an optimized nanoparticulate ink for the fabrication of AZO thin films using scalable, low-cost direct write processing (ultrasonic spray deposition) in air at atmospheric pressure. The thin films were made via thermal processing of as-deposited films. AZO films deposited using the proposed nanoparticulate ink with further reducing in vacuum and rf plasma of forming gas exhibited optical transparency greater than 95% across the visible spectrum, and electrical resistivity of 0.5 Ω cm and it drops down to 7.0 × 10-2 Ω cm after illuminating with UV light, which is comparable to commercially available tin doped indium oxide colloidal coatings. Various structural analyses were performed to investigate the influence of ink chemistry, deposition parameters, and annealing temperatures on the structural, optical, and electrical characteristics of the spray deposited AZO thin films. Optical micrographs confirmed the presence of surface defects and cracks using the AZO NPs ink without any additives. After adding N-(2-Aminoethyl)-3-aminopropylmethyldimethoxy silane to the ink, AZO films exhibited an optical transparency which was virtually identical to that of the plain glass substrate.

  18. Effect of Al Doping on Structural, Electrical, Optical and Photoluminescence Properties of Nano-Structural ZnO Thin Films

    Institute of Scientific and Technical Information of China (English)

    M. Mozibur Rahman; M.K.R. Khan; M. Rafiqul Islam; M.A. Halim; M. Shahjahan; M.A. Hakim; Dilip Kumar Saha; Jasim Uddin Khan

    2012-01-01

    The nano-structural Al-doped ZnO thin films of different morphologies deposited on glass substrate were successfully fabricated at substrate temperature of 350 ℃ by an inexpensive spray pyrolysis method. The structural, electrical, optical and photoluminescence properties were investigated. X-ray diffraction study revealed the crystalline wurtzite (hexagonal) structure of the films with nano-grains. Scanning electron microscopy (SEM) micrographs indicated the formation of a large variety of nano-structures during film growth. The spectral absorption of the films occurred at the absorption edge of -410 nm. In the present study, the optical band gap energy 3.28 eV of ZnO decreased gradually to 3.05 eV for 4 mol% of AI doping. The deep level activation energy decreased and carrier concentrations increased substantially with increasing doping. Exciting with the energy 3.543 eV (A=350 nm), a narrow and a broad characteristic photoluminescence peaks that correspond to the near band edge (NBE) and deep level emissions (DLE), respectively emerged.

  19. Transparent conductive Al-doped ZnO thin films grown at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Wang Yuping; Lu Jianguo; Bie Xun; Gong Li; Li Xiang; Song Da; Zhao Xuyang; Ye Wenyi; Ye Zhizhen [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)

    2011-05-15

    Aluminum-doped ZnO (ZnO:Al, AZO) thin films were prepared on glass substrates by dc reactive magnetron sputtering from a Zn-Al alloy target at room temperature. The effects of the Ar-to-O{sub 2} partial pressure ratios on the structural, electrical, and optical properties of AZO films were studied in detail. AZO films grown using 100:4 to 100:8 Ar-to-O{sub 2} ratio result in acceptable quality films with c-axis orientated crystals, uniform grains, 10{sup -3} {Omega} cm resistivity, greater than 10{sup 20} cm{sup -3} electron concentration, and high transmittance, 90%, in the visible region. The lowest resistivity of 4.11x10{sup -3} {Omega} cm was obtained under the Ar-to-O{sub 2} partial pressure ratio of 100:4. A relatively strong UV emission at {approx}3.26 eV was observed in the room-temperature photoluminescence spectrum. X-ray photoelectron spectroscopy analysis confirmed that Al was introduced into ZnO and substitutes for Zn and doped the film n-type.

  20. Environmental stability of solution processed Al-doped ZnO naoparticulate thin films using surface modification technique

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • AZO nanoparticulate films were deposited using ultrasonic spray deposition. • Functionalization of solution processed AZO thin films was carried out. • Contact angles and QNM AFM results confirmed the existence of molecular layers. • Environmental stability of AZO films greatly increased with surface modification. - Abstract: The environmental stability of solution processed Al-doped ZnO (AZO) thin films was enhanced by functionalizing the film surface with a thin self-assembled molecular layer. Functionalization of AZO films was performed using two types of molecules having identical 12-carbon alkyl chain termination but different functional groups: dodecanethiol (DDT) and dodecanoic acid (DDA). Surface modified AZO films were examined using electrical resistivity measurements, contact angle measurements and quantitative nanomechanical property mapping atomic force microscopy. The hydrophobic layer inhibits the penetration of oxygen and water into the AZO's grain boundaries thus significantly increasing the environmental stability over unmodified AZO. Surface modified AZO films using DDT exhibited lower electrical resistivity compared to DDA functionalized AZO films. Our study demonstrates a new approach for improving the physical properties of oxide based nanoparticulate films for device applications

  1. Environmental stability of solution processed Al-doped ZnO naoparticulate thin films using surface modification technique

    Energy Technology Data Exchange (ETDEWEB)

    Vunnam, Swathi, E-mail: swathivunnam@gmail.com [Program of Nanoscience and Nanoengineering, South Dakota School of Mines and Technology, Rapid City, SD 57701 (United States); Ankireddy, Krishnamraju; Kellar, Jon [Program of Materials Engineering and Science, South Dakota School of Mines and Technology, Rapid City, SD 57701 (United States); Cross, William, E-mail: William.Cross@sdsmt.edu [Program of Materials Engineering and Science, South Dakota School of Mines and Technology, Rapid City, SD 57701 (United States)

    2014-12-15

    Graphical abstract: - Highlights: • AZO nanoparticulate films were deposited using ultrasonic spray deposition. • Functionalization of solution processed AZO thin films was carried out. • Contact angles and QNM AFM results confirmed the existence of molecular layers. • Environmental stability of AZO films greatly increased with surface modification. - Abstract: The environmental stability of solution processed Al-doped ZnO (AZO) thin films was enhanced by functionalizing the film surface with a thin self-assembled molecular layer. Functionalization of AZO films was performed using two types of molecules having identical 12-carbon alkyl chain termination but different functional groups: dodecanethiol (DDT) and dodecanoic acid (DDA). Surface modified AZO films were examined using electrical resistivity measurements, contact angle measurements and quantitative nanomechanical property mapping atomic force microscopy. The hydrophobic layer inhibits the penetration of oxygen and water into the AZO's grain boundaries thus significantly increasing the environmental stability over unmodified AZO. Surface modified AZO films using DDT exhibited lower electrical resistivity compared to DDA functionalized AZO films. Our study demonstrates a new approach for improving the physical properties of oxide based nanoparticulate films for device applications.

  2. Fabrication of high infrared reflective Al-doped ZnO thin films through electropulsing treatment for solar control

    Energy Technology Data Exchange (ETDEWEB)

    Miao, Dagang, E-mail: chinesemdg@163.com; Hu, Huawen; Gan, Lu

    2015-08-05

    Highlights: • Rapid electropulsing treatment (EPT) was applied on AZO thin films. • AZO film presented electrical resistivity of 9.03 × 10{sup −4} Ω cm after 4.5 min of EPT. • AZO film presented high infrared reflection rate of 80–85% after 4.5 min of EPT. • The prepared AZO film can be used as solar control film. - Abstract: In this study, Al-doped ZnO (AZO) thin films were finished by low-energy consumed electropulsing treatment (EPT) in a short time. The EPT effect on the resulting AZO films was investigated by X-ray Diffraction (XRD), Hall Effect measurement, UV–visible transmittance spectra, Scanning Electron Microscope (SEM), Atomic Force Microscopy (AFM) and Fourier Transform Infrared Spectroscopy. As compared with the other EPT-treated AZO films, the prepared AZO films corresponding to 4.5 min EPT exhibited higher degree of crystallization, higher visible transmittance with blue shift, smoother surface, lower electrical resistivity of 9.03 × 10{sup −4} Ω cm, and higher infrared reflection rate of 80–85%. By the 4.5 min of EPT, the electrical conductivity of the resulting AZO thin film was increased by approximately 82.3%. Moreover, it was also found that prolonged EPT would degrade the film properties. These results indicate that the fast and low-energy consumed EPT might be a promising substitution for traditional heat annealing, and the prepared high infrared reflective AZO films make them promising candidates for being applied as solar control films.

  3. Effect of laser irradiation on gas sensing properties of sol–gel derived nanocrystalline Al-doped ZnO thin films

    International Nuclear Information System (INIS)

    The effect of laser irradiation on the performance of gas sensor made with sol–gel derived Al-doped ZnO thin films was investigated. The films with desired thicknesses were deposited on the alkali-free glass substrates by a sol–gel process. A pulsed laser system with a wavelength of 532 nm, a pulsed duration of 8 ns, pulsed frequency of 5 kHz and the laser fluence in the range of 1.06–3.58 J/cm2 was used as the irradiation source. The microstructure, optical transmittance, surface morphology, electrical conductivity and gas sensor performance of the as-deposited and laser-irradiated Al-doped ZnO films were studied as a function of laser energy level. The X-ray diffraction results indicated that low laser energy significantly enhanced the crystallinity and promoted grain growth, whereas high laser energy irradiation resulted in deterioration of crystalline quality. It was also found that the laser irradiation affected the surface morphology and electrical conductivity of ZnO films. The gas sensor performance of Al-doped ZnO sensors was examined in terms of ZnO film thicknesses and H2 concentrations in the air at an operating temperature of 130 °C. It was found that the sensing response of Al-doped ZnO sensors varied depending on the film thickness as well as the laser energy level. An optimum laser energy level resulted in high and rapid response characteristics of gas sensors for the detection of H2. The results also suggested that the crystallinity was critical to achieve the optimum sensor performance. - Highlights: • Aluminum was doped in ZnO thin films via a sol–gel coating process. • Laser irradiation was employed to improve the effect of doping. • The properties of ZnO were investigated as a function of laser energy. • We found that the laser irradiation enhances the gas sensor performance

  4. Effects of Al Concentration on Structural and Optical Properties of Al-doped ZnO Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min Su; Yim, Kwang Gug; Leem, Jae Young [Inje University, Gimhae (Korea, Republic of); Son, Jeong Sik [Kyungwoon University, Gumi (Korea, Republic of)

    2012-04-15

    Aluminium (Al)-doped zinc oxide (AZO) thin films with different Al concentrations were prepared by the solgel spin-coating method. Optical parameters such as the optical band gap, absorption coefficient, refractive index, dispersion parameter, and optical conductivity were studied in order to investigate the effects of the Al concentration on the optical properties of AZO thin films. The dispersion energy, single-oscillator energy, average oscillator wavelength, average oscillator strength, and refractive index at infinite wavelength of the AZO thin films were found to be affected by Al incorporation. The optical conductivity of the AZO thin films also increases with increasing photon energy

  5. Investigation of the biaxial stress of Al-doped ZnO thin films on a flexible substrate with RF magnetron sputtering

    Science.gov (United States)

    Huang, Kuo-Ting; Chen, Hsi-Chao; Cheng, Po-Wei; Chang, Jhe-Ming

    2016-01-01

    Transparent conductive Al-doped ZnO (AZO) thin films were deposited onto poly(ethylene terephthalate) (PET) substrate, using the radio frequency (RF) magnetron sputtering method. The residual stress of flexible electronics was investigated by a double beam shadow moiré interferometer with phase shifting interferometry (PSI). Moreover, the biaxial stress of AZO thin films can be graphically represented by using Mohr’s circle of stress. The residual stress of AZO thin films becomes more compressive with the increase in sputtering power. The maximum residual stress is -1115.74 MPa, and the shearing stress is 490.57 MPa at a sputtering power of 200 W. The trends of residual stress were evidenced by the X-ray diffraction (XRD) patterns and optical properties of AZO thin films. According to the evaluation results of the refractive index and the extinction coefficient, the AZO thin films have better quality when the sputtering power less than 100 W.

  6. Effect of the RF sputtering power on microstructural, optical and electrical properties of Al doped ZnO thin films

    International Nuclear Information System (INIS)

    ZnO:Al (AZO) thin films have been deposited by radio frequency (RF) magnetron sputtering and RF power applied to the target has been varied in the range 600–1200 W. RF power effect on structural, electrical and optical properties was investigated and the relationship existing between these properties and the film lattice defect distribution was discussed. At the increasing of the RF power it was found that AZO films, having a preferential growth orientation along (002) direction, showed a decrease of the lattice distance indicating a less defected structure. Furthermore, at the increase of the RF power a higher optical absorption by free carriers, coupled with an increase of the band gap value, was observed. Resistivity varied from 1.1 × 10−3 Ω cm at 600 W down to a minimum value of 5.6 × 10−4 Ω cm at 1200 W, whereas the carrier density increased up to 1 × 1021 cm−3. Lattice defect variation of AZO films was analyzed by photoluminescence (PL) measurements. Presence and amount of different lattice defects were evaluated for AZO films deposited at different RF powers. At 600 W the film structure was dominated by zinc vacancies (VZn), whereas for higher RF power the PL band associated with VZn decreased and interstitial oxygen (Oi) band remarkably increased. PL analysis revealed that extrinsic Al doping is the dominant effect on the conductivity enhancement. It was hypothesized that at higher RF power a more effective diffusion phenomenon can give more effective Al doping and less amount of zinc vacancies. As a consequence, Al atoms are more effectively trapped into the structure. - Highlights: • ZnO:Al thin films have been deposited by RF sputtering technique. • The effect of the sputtering power on film properties has been investigated. • Electrical, optical and structural characterization has been carried out. • PL analysis revealed lattice defect chemistry variation at the increase of RF power. • At high RF power VZn defects decrease and

  7. Effect of the RF sputtering power on microstructural, optical and electrical properties of Al doped ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Spadoni, A.; Addonizio, M.L., E-mail: marialuisa.addonizio@enea.it

    2015-08-31

    ZnO:Al (AZO) thin films have been deposited by radio frequency (RF) magnetron sputtering and RF power applied to the target has been varied in the range 600–1200 W. RF power effect on structural, electrical and optical properties was investigated and the relationship existing between these properties and the film lattice defect distribution was discussed. At the increasing of the RF power it was found that AZO films, having a preferential growth orientation along (002) direction, showed a decrease of the lattice distance indicating a less defected structure. Furthermore, at the increase of the RF power a higher optical absorption by free carriers, coupled with an increase of the band gap value, was observed. Resistivity varied from 1.1 × 10{sup −3} Ω cm at 600 W down to a minimum value of 5.6 × 10{sup −4} Ω cm at 1200 W, whereas the carrier density increased up to 1 × 10{sup 21} cm{sup −3}. Lattice defect variation of AZO films was analyzed by photoluminescence (PL) measurements. Presence and amount of different lattice defects were evaluated for AZO films deposited at different RF powers. At 600 W the film structure was dominated by zinc vacancies (V{sub Zn}), whereas for higher RF power the PL band associated with V{sub Zn} decreased and interstitial oxygen (O{sub i}) band remarkably increased. PL analysis revealed that extrinsic Al doping is the dominant effect on the conductivity enhancement. It was hypothesized that at higher RF power a more effective diffusion phenomenon can give more effective Al doping and less amount of zinc vacancies. As a consequence, Al atoms are more effectively trapped into the structure. - Highlights: • ZnO:Al thin films have been deposited by RF sputtering technique. • The effect of the sputtering power on film properties has been investigated. • Electrical, optical and structural characterization has been carried out. • PL analysis revealed lattice defect chemistry variation at the increase of RF power.

  8. Study on structural and electrical properties of Al-doped ZnO thin films prepared by sol-gel method

    Energy Technology Data Exchange (ETDEWEB)

    Nasr, Babak; Dasgupta, Subho; Kruk, Robert; Hahn, Horst [Forschungszentrum Karlsruhe, Institute for Nanotechnology, D-76344 Eggenstein-Leopoldshafen (Germany)

    2009-07-01

    The screening length of the external field is one of the critical parameters to tune the transport properties of a material. Therefore, the systems of interest are those with carrier concentrations in the same order as the induced maximum surface charge density achievable. In view of this criterion we choose Al-doped ZnO (AZO) oxides with a near metallic conductivity, and a carrier density easily controllable via Al doping. This study is an attempt to optimize conductivity of the nanocrystalline films through the Al concentration and morphology modifications. The AZO thin films were prepared by the sol-gel process. The thin film deposition was carried out by spin-coating technique on high quality float glass substrates. The film structure and morphology were characterized by profilometer, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The transport properties were measured with the four point resistance and Hall-effect measurements using standard van der Pauw geometry. The effects of precursor concentrations, annealing temperature on the structural and electrical properties are discussed.

  9. Effect of Al doping on microstructure and optical band gap of ZnO thin film synthesized by successive ion layer adsorption and reaction

    Indian Academy of Sciences (India)

    S Mondal; S R Bhattacharyya; P Mitra

    2013-02-01

    Thin films of pure and aluminum-doped zinc oxide (AZO) were deposited on glass substrates from ammonium zincate bath following a chemical dipping technique called successive ion layer adsorption and reaction (SILAR). Characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-rays (EDX) were used to investigate the effect of Al doping on the microstructure of AZO films. Particle size analysis using X-ray line broadening shows marginally increasing trend with increasing Al impurity. The average particle size for pure ZnO is 22.75 nm. It increases to 24.26 nm for 1% AZO film and 25.13 nm for 2% AZO film. Incorporation of Al was confirmed from elemental analysis using EDX. SEM micrograph shows that pure ZnO particles are spherical shaped. However, AZO films show particles with off-spherical shape with compact interconnected grains. The value of band gap for pure ZnO is 3.229 eV and it increases to 3.29 eV for 1% AZO indicating a blue-shift for 1% AZO film. However, for 2% AZO film, a decrease in band gap compared to pure ZnO is observed indicating a red-shift of fundamental absorption edge. Electrical resistance shows an initial decrease with increasing Al content. With further enhancement of Al incorporation, the resistance increases.

  10. Al-doped ZnO nanofilms: Synthesis and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Huczko, A.; Dabrowska, A. [Department of Chemistry, Warsaw University, Warsaw (Poland); Madhup, D.K. [Department of Physics, Kathmandu University, Dhulikhel (Nepal); College of Biomedical Engineering and Applied Sciences, Hadigaun, Kathmandu (Nepal); Subedi, D.P.; Chimouriya, S.P. [Department of Physics, Kathmandu University, Dhulikhel (Nepal)

    2010-12-15

    Al-doped and un-doped ZnO nanofilms on quartz substrate were obtained by ultrasonic spray pyrolysis of salt solutions (mole concentration of Al within 0-10%). The films were characterized by Scanning electron microscopy (SEM), X-ray diffraction (XRD), Atomic force microscopy (AFM) and UV spectroscopy to study the morphology and optical properties. The optical studies showed that the increase in Al within ZnO thin layer increases its band gap energy. The obtained value of band gap energy is very close to the determined oscillation energy. However, the dispersion energy is nearly half of band gap energy value. (Copyright copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. Enhanced photovoltaic performance of quantum dot-sensitized solar cell fabricated using Al-doped ZnO nanorod electrode

    Science.gov (United States)

    Raja, M.; Muthukumarasamy, N.; Velauthapillai, Dhayalan; Balasundrapraphu, R.; Senthil, T. S.; Agilan, S.

    2015-04-01

    ZnO and Al doped ZnO nanorods have been successfully synthesized on ITO substrate via solgel dip coating method without using any catalyst. The X-ray diffraction studies showed that the Al doped ZnO samples are of hexagonal wurtzite structure. The Al ions were successfully incorporated into the ZnO lattice. Scanning electron microscopy images reveal that the average diameter of ZnO nanorods and Al doped ZnO nanorods are ∼300 nm and ∼200 nm respectively. The energy dispersive X-ray (EDS) analysis confirmed the presence Al in the ZnO thin films. The CdS quantum dot sensitized Al doped ZnO solar cell exhibited a power conversion efficiency of 1.5%.

  12. Characteristics of the electromagnetic interference shielding effectiveness of Al-doped ZnO thin films deposited by atomic layer deposition

    Science.gov (United States)

    Choi, Yong-June; Gong, Su Cheol; Johnson, David C.; Golledge, Stephen; Yeom, Geun Young; Park, Hyung-Ho

    2013-03-01

    The structural, optical, and electrical properties of Al-doped ZnO (ZnO:Al) thin films deposited by atomic layer deposition (ALD) with a modified precursor pulse sequence were investigated to evaluate the electromagnetic interference shielding effectiveness (EMI-SE). A Zn-Al-O precursor exposure sequence was used in a modified ALD procedure to result in better distribution of Al3+ ions in the ZnO matrix with the aim of reducing the formation of complete nano-laminated structures that may form in the typical alternating ZnO and Al2O3 deposition procedure. The ALD dopant concentration of the ZnO:Al films was varied by adjusting the dopant deposition intervals of the ZnO:Znsbnd Alsbnd O precursor pulse cycle ratios among 24:1, 19:1, 14:1, and 9:1. The lowest obtained resistivity and average transmittance in the visible region (380-780 nm) were 5.876 × 10-4 Ω cm (carrier concentration of 6.02 × 1020 cm-3 and Hall mobility of 17.65 cm2/V s) and 85.93% in the 131 nm thick ZnO:Al(19:1) film, respectively. The average value of the EMI-SE in the range of 30 MHz to 1.5 GHz increased from 1.1 dB for the 121 nm thick undoped ZnO film to 6.5 dB for the 131 nm thick ZnO:Al(19:1) film.

  13. Decoration of PbS nanoparticles on Al-doped ZnO nanorod array thin film with hydrogen treatment as a photoelectrode for solar water splitting

    International Nuclear Information System (INIS)

    Highlights: ► AZO nanorod array thin film is used as a photoanode for solar water splitting. ► Hydrogen treatment and sensitization by PbS nanoparticles enhance photocurrent. ► A novel ITO/FTO-free composite photoelectrode is developed. ► The pre-fabrication and use of an extra TCO thin film substrate is unnecessary. -- Abstract: Al-doped ZnO (AZO) nanorod arrays thin film with hydrogen treatment is directly used as a photoelectrode for solar water splitting without an extra transparent conducting oxide (TCO) thin film because it possesses the functions of TCO thin film and photoactive 1-dimensional nanostructured semiconductor simultaneously. To enhance the absorption in the visible region, PbS nanoparticles decorated the AZO nanorods via successive ionic layer adsorption and reaction route. The PbS nanoparticles have a face-centered cubic structure and their decoration does not destroy the 1-dimensional morphology of AZO nanorod arrays. With increasing the cycle number of PbS nanoparticles decoration, the grain size and loading of PbS nanoparticles become larger gradually which leads to lower energy bandgap and stronger absorption. A maximum photocurrent density of 1.65 mW cm−2 is obtained when the cycle number is 20, which is much higher than those without PbS nanoparticles sensitization or hydrogen treatment. This demonstrates that the AZO nanorod array thin film with hydrogen treatment can be directly used as a photoelectrode without an extra TCO thin film. Because the use of expensive metals can be avoided and the pre-fabrication of TCO thin film substrate is necessary no more, the fabrication of such a composite photoelectrode becomes simple and low-cost. So, it has great potentials in solar water splitting after sensitization by quantum dots capable of visible light absorption

  14. Advanced properties of Al-doped ZnO films with a seed layer approach for industrial thin film photovoltaic application

    International Nuclear Information System (INIS)

    Currently sputtered Al-doped ZnO films are transferred to industry for the application in thin film silicon solar modules. These films are known to easily form light trapping structures upon etching which are necessary for absorbers with low absorbance such as μc-Si. Up to now the best structures for high efficiency thin film silicon solar cells were obtained by low rate radio frequency (r.f.) sputtering of ceramic targets. However, for industrial application a high rate process is essential. Therefore a seed layer approach was developed to increase the deposition rate while keeping the desired etch morphology and electrical properties. Aluminum doped ZnO films were deposited dynamically by direct current (d.c.) magnetron sputtering from a ceramic ZnO:Al2O3 target (1 wt.%) onto an additional seed layer prepared by r.f. sputtering. ZnO:Al films were investigated with respect to their optical and electrical properties as well as the morphology created after etching for a-Si/μc-Si solar cells. Additionally atomic force microscopy, scanning electron microscopy, X-ray diffraction and Hall measurements were performed, comparing purely r.f. or d.c. sputtered films with d.c. sputtered films on seed layers. With the seed layer approach it was possible to deposit ZnO:Al films with a visual transmittance of 83.5%, resistivity of 295 μΩ cm, electron mobility of 48.9 cm2/Vs and electron density of 4.3 · 1020 cm−3 from a ceramic target at 330 °C. Etch morphologies with 1 μm lateral structure size were achieved. - Highlights: ► Seed layer approach for dynamic sputter deposition of enhanced quality ZnO:Al. ► A thin radio frequency sputtered ZnO:Al layer assists film nucleation on glass. ► Electron mobility was increased up to 49 cm2/Vs due to quasi-epitaxial film growth. ► Etch morphology exhibits 1 μm wide craters for light trapping in solar cells. ► The concept was transferred to a seed layer sputtered with direct current

  15. Microstructure and micromorphology of ZnO thin films: Case study on Al doping and annealing effects

    Science.gov (United States)

    Ţălu, Ştefan; Bramowicz, Miroslaw; Kulesza, Slawomir; Solaymani, Shahram; Ghaderi, Atefeh; Dejam, Laya; Elahi, Seyed Mohammad; Boochani, Arash

    2016-05-01

    The aim of this work is to investigate the three-dimensional (3-D) surface texture of Aliminium doped Zinc Oxide (AZO) thin films deposited by Radio Frequency sputtering method on the quartz substrates. Deposited samples were annealed under argon flux at three different temperatures: 400 °C, 500 °C, and 600 °C, followed by gradual cooling down to room temperature. To characterize the structure of samples X-ray diffraction (XRD) patterns and Rutherford Back Scattering (RBS) spectra were applied. The Scanning electron microscope (SEM) and the atomic force microscope (AFM) were applied to study the samples' surface morphology. Then statistical, fractal and functional surface characteristics were computed. The analysis of 3-D surface texture of AZO thin films is crucial to control the 3-D surface topography features and to correct interpretate the surface topographic parameters. It also allows understanding the relationship between 3-D the surface topography and the functional (physical, chemical and mechanical) properties of AZO thin films.

  16. A study on the Al doping behavior with sol aging time and its effect on structural and optical properties of sol–gel prepared ZnO thin films

    International Nuclear Information System (INIS)

    A series of aluminum doped zinc oxide (AZO) thin films were prepared by sol–gel method on glass substrates to investigate the behavior of Al doping with sol aging time (as-prepared to 2 weeks). X-ray diffraction analysis revealed a considerable shift in (002) diffraction peak towards higher diffraction angles with increasing sol aging time from as-prepared to 24 h which was found to be reverse with further aging. X-ray photoelectron spectroscopy and UV–vis spectroscopy were performed to investigate the change in chemical states of Al/Zn/O atoms and band gap fluctuations respectively. It was found that more Al atoms were doped into ZnO lattice with the increment of sol aging time and saturated level was achieved for ∼ 20–24 h. Field emission scanning electron microscope and atomic force microscope characterization showed dense and homogeneous film morphology with decreasing relative surface roughness with sol aging time. Photoluminescence analysis and UV–vis spectroscopy revealed defect free films by exhibiting high optical transmission in the visible regime and found to improve with sol aging time. It could be concluded that solution aging time clearly influence the doping behavior and a suitable aging provides more stability which results into more Al atoms substitution for Zn in ZnO crystal lattice that affect the structural, morphological and optical properties of AZO thin films. - Highlights: • Effects of sol aging-time on the properties of Al-doped ZnO thin films. • Al atoms doping in to ZnO lattice increased with sol aging up to a certain time. • Films prepared from 20-24-h aged sol showed minimum surface roughness. • Optical transmittance of thin films was found sensitive to sol aging time

  17. Influence of negative ion resputtering on Al-doped ZnO thin films prepared by mid-frequency magnetron sputtering

    International Nuclear Information System (INIS)

    Al-doped ZnO (AZO) films were deposited on glass substrates by mid-frequency magnetron sputtering with a ceramic ZnO:Al2O3 (98 wt%:2 wt%) target. The origin of the high resistivity of the films at the substrate position facing the erosion area of the target was investigated. The results indicate a preferential resputtering of Zn atoms caused by the negative ions, which leads to an increase of the oxygen/metal ratio in the films. Then more Al oxides form and result in the decrease of AlZn (the main donor in the films) concentration in the films. Thus the free carrier concentration decreases badly. This is the main mechanism responsible for the high resistivity.

  18. Microstructural and surface property variations due to the amorphous region formed by thermal annealing in Al-doped ZnO thin films grown on n-Si (1 0 0) substrates

    International Nuclear Information System (INIS)

    X-ray diffraction (XRD) patterns revealed that the as-grown and annealed Al-doped ZnO (AZO) films grown on the n-Si (1 0 0) substrates were polycrystalline. Transmission electron microscopy (TEM) images showed that bright-contrast regions existed in the grain boundary, and high-resolution TEM (HRTEM) images showed that the bright-contrast regions with an amorphous phase were embedded in the ZnO grains. While the surface roughness of the AZO film annealed at 800 deg. C became smoother, those of the AZO films annealed at 900 and 1000 deg. C became rougher. XRD patterns, TEM images, selected-area electron diffraction patterns, HRTEM images, and atomic force microscopy (AFM) images showed that the crystallinity in the AZO thin films grown on the n-Si (1 0 0) substrates was enhanced resulting from the release in the strain energy for the AZO thin films due to thermal annealing at 800 deg. C. XRD patterns and AFM images show that the crystallinity of the AZO thin films annealed at 1000 deg. C deteriorated due to the formation of the amorphous phase in the ZnO thin films.

  19. Defects generated by MF magnetron sputtering and their influences on the electrical and optical properties of Al doped ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Changshan; Shirolkar, Mandar M.; Li, Jieni [Hefei National Laboratory for Physical Science at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Wu, Binjun [Hefei National Laboratory for Physical Science at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); QinZhou College, QinZhou, Guangxi 535000 (China); Yin, Shiliu; Li, Ming [Hefei National Laboratory for Physical Science at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Wang, Haiqian, E-mail: hqwang@ustc.edu.cn [Hefei National Laboratory for Physical Science at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China)

    2015-10-01

    Highlights: • Oxygen interstitial dominates the carrier concentration of sputtered films. • Chemisorbed oxygen decreases the mobility of sputtered films. • Hydrogen annealing can remove oxygen interstitials and chemisorbed oxygen. • High and low resistivity states (HRS and LRS) are observed under hydrogen atmosphere. • Defect configurations of (H{sub 2}){sub i} and H{sub O} + H{sub i} are assigned to HRS and LRS. - Abstract: In this paper, the defects of Al doped ZnO films generated by magnetron sputtering in the deposition processes are comprehensively investigated. It is found that oxygen ion bombardment deteriorates the crystallinity and generates oxygen related defects, such as oxygen interstitials (O{sub i}), chemisorbed oxygen at the grain boundaries (O{sub GB}), and oxygen vacancies (V{sub O}). O{sub i} and O{sub GB} decrease the carrier concentration and mobility of the pristine films remarkably, but they can be removed by hydrogen annealing. However, the grain boundary scattering originated from poor crystallinity cannot be reduced by the annealing below 450 °C. Moreover, the in-situ temperature-dependent resistivity measurement under hydrogen atmosphere suggests that hydrogen atoms are incorporated into the ZnO: Al films and interact with V{sub O}. We propose that there are two energetically favorable states for the incorporated hydrogen. The defect configurations of (H{sub 2}){sub i} and H{sub O} + H{sub i} are assigned to the high resistivity state (HRS) and low resistivity state (LRS) respectively and the switching between these two states is activated by V{sub O} and mediated by a metastable state (H{sub 2}){sup *}{sub O}. The transformation between these two resistivity states leads to a hysteresis loop during the heating and cooling process.

  20. The effect of dopant concentration on properties of transparent conducting Al-doped ZnO thin films for efficient Cu2ZnSnS4 thin-film solar cells prepared by electrodeposition method

    Science.gov (United States)

    Mkawi, E. M.; Ibrahim, K.; Ali, M. K. M.; Farrukh, M. A.; Mohamed, A. S.

    2015-11-01

    Al-doped ZnO (AZO) thin films were potentiostatically deposited on indium tin oxide substrates. The influence of the doping level of the ZnO:Al films was investigated. The results of the X-ray diffraction and scanning electron microscopy analysis revealed that the structural properties of the AZO films were found polycrystalline with a hexagonal wurtzite-type structure along the (002) plane. The grain size of the AZO films was observed as approximately 3 μm in the film doping with 4 mol% ZnO:Al concentration. The thin films also exhibited an optical transmittance as high as 90 % in the wavelength range of 100-1,000 nm. The optical band gap increased from 3.33 to 3.45 eV. Based on the Hall studies, the lowest resistivity (4.78 × 10-3 Ω cm) was observed in the film doping with 3 mol% ZnO:Al concentration. The sheet resistant, carrier concentration and Hall mobility values were found as 10.78 Ω/ square, 9.03 × 1018 cm-3 and 22.01 cm2/v s, respectively, which showed improvements in the properties of AZO thin films. The ZnO:Al thin films were used as a buffer layer in thin-film solar cells with the structure of soda-lime glass/Mo/Cu2ZnSnS4/ZnS/ZnO/Al grid. The best solar cell efficiency was 2.3 % with V OC of 0.430 V, J SC of 8.24 mA cm-2 and FF of 68.1 %.

  1. Characteristics of Al-doped ZnO thin films prepared in Ar + H2 atmosphere and their vacuum annealing behavior

    International Nuclear Information System (INIS)

    The microstructure and electrical–optical properties of Al-doped ZnO (AZO) films have been studied as a function of H2 flux in the magnetron sputtering process at 150 °C and postannealing temperature in vacuum. As H2 flux increases in the sputtering gas, the AZO films deposited have a (002) preferred orientation rather than the mixed (100) and (002) orientations, the grain size shows a tendency to first increase then decrease, and (002) diffraction peak position is inclined to shift to higher angles first then to lower angles. The resistivity of the films first decreases then increases with H2 flux, and the lowest resistivity of 4.02 × 10−4Ω cm is obtained at a H2 flux of 10 sccm. The average transmittance in the visible region shows little dependence on H2 flux. As a whole, the AZO films with higher values of figure of merit are obtained when the H2 flux is in the range of 6–12 sccm. The AZO films deposited in Ar and Ar + H2 exhibit different annealing behaviors. For the AZO film deposited in Ar, the grain size gradually increases, the stresses are relaxed, the resistivity first decreases then increases, and the average transmittance in the visible region is unchanged initially then somewhat decreased as annealing temperature is increased. The optimum annealing temperature for improving properties of AZO films deposited in Ar is 300 °C. For the AZO films deposited in Ar + H2, annealing does not significantly change the microstructure but increases the resistivity of the films; the average transmittance in the visible region remains unchanged initially but greatly reduced with further increase in annealing temperature. The carrier transport in the as-deposited and annealed films appears to be controlled by a mechanism of grain boundary scattering, and the value of Eg increases with the increase in carrier concentration due to Burstein–Moss effect

  2. UV assisted photoelectrocatalytic oxidation of phthalic acid using spray deposited Al doped zinc oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Mahadik, M.A.; Shinde, S.S.; Hunge, Y.M.; Mohite, V.S.; Kumbhar, S.S.; Moholkar, A.V.; Rajpure, K.Y.; Bhosale, C.H., E-mail: chbhosale@gmail.com

    2014-10-25

    Highlights: • Nanostructured undoped and AZO thin films prepared by chemical spray pyrolysis. • Effect of Al doping on the structural, morphological and photoluminance properties. • Photocatalytic degradation of phthalic acid under UV light illumination. • Reaction kinetics and mineralization of phthalic acid. - Abstract: Undoped and Al doped ZnO (AZO) thin films are successfully prepared by spray pyrolysis technique at optimised substrate temperature of 400 °C onto amorphous and F:SnO{sub 2} coated glass substrates. Effect of Al doping on structural, morphological and optical properties of ZnO thin films is studied. Deposited films are polycrystalline with a hexagonal (wurtzite) crystal structure having (0 0 2) preferred orientation. The PEC characterization shows that, short circuit current (I{sub sc}) and open circuit voltage (V{sub oc}) are (I{sub sc} = 0.38 mA and V{sub oc} = 421 mV) relatively higher at the 3 at.% Al doping. SEM images show deposited thin films are compact and uniform with seed like grains. All films exhibit average transmittance of about 82% in the visible region and a sharp absorption onset at 375 nm corresponding to 3.3 eV. The photocatalytic activities of the large surface area (64 cm{sup 2}) Al-doped ZnO photocatalyst samples were evaluated by photoelectrocatalytic degradation of phthalic acid under UV light irradiation. The results show that the 3 at.% AZO thin film photocatalyst exhibited degradation of phthalic acid up to about 45% within 3 h with significant reduction in COD and TOC values.

  3. Investigation of conductive and transparent Al-doped ZnO/Ag/Al-doped ZnO multilayer coatings by electron beam evaporation

    International Nuclear Information System (INIS)

    Multilayer coatings consisting of thin silver layer sandwiched between layers of Al-doped ZnO (AZO) were prepared by electron beam evaporation. The optical and electrical performances of AZO/Ag/AZO multilayers were investigated. Optimization of the multilayer coatings resulted with low sheet resistance of 7.7 Ω/sq and transmittance of 85%. The influence of thickness of each layer on the optic and electrical performance was analyzed. The sheet resistance of the multilayer was reduced to 5.34 Ω/sq. and the average transmittance was improved to 90% by the thermal treatment. The coatings had satisfactory properties of low resistance, high transmittance and thermal stability

  4. Structural, optical and electrical properties of Al-doped ZnO microrods prepared by spray pyrolysis

    International Nuclear Information System (INIS)

    Al-doped ZnO thin films were obtained on glass substrates by spray pyrolysis in air atmosphere. The molar ratio of Al in the spray solution was changed in the range of 0-20 at.% in steps of 5 at.%. X-ray diffraction patterns of the films showed that the undoped and Al-doped ZnO films exhibited hexagonal wurtzite crystal structure with a preferred orientation along (002) direction. Surface morphology of the films obtained by scanning electron microscopy revealed that pure ZnO film grew as quasi-aligned hexagonal shaped microrods with diameters varying between 0.7 and 1.3 μm. However, Al doping resulted in pronounced changes in the morphology of the films such as the reduction in the rod diameter and deterioration in the surface quality of the rods. Nevertheless, the morphology of Al-doped samples still remained rod-like with a hexagonal cross-section. Flower-like structures in the films were observed due to rods slanting to each other when spray solution contained 20 at.% Al. Optical studies indicated that films had a low transmittance and the band gap decreased from 3.15 to 3.10 eV with the increasing Al molar ratio in the spray solution from 0 to 20 at.%.

  5. Temperature dependent dual hydrogen sensor response of Pd nanoparticle decorated Al doped ZnO surfaces

    International Nuclear Information System (INIS)

    Sputter deposited Al doped ZnO (AZO) thin films exhibit a dual hydrogen sensing response in the temperature range 40 °C–150 °C after surface modifications with palladium nanoparticles. The unmodified AZO films showed no response in hydrogen in the temperature range 40 °C–150 °C. The operational temperature windows on the low and high temperature sides have been estimated by isolating the semiconductor-to-metal transition temperature zone of the sensor device. The gas response pattern was modeled by considering various adsorption isotherms, which revealed the dominance of heterogeneous adsorption characteristics. The Arrhenius adsorption barrier showed dual variation with change in hydrogen gas concentration on either side of the semiconductor-to-metal transition. A detailed analysis of the hydrogen gas response pattern by considering the changes in nano palladium due to hydrogen adsorption, and semiconductor-to-metal transition of nanocrystalline Al doped ZnO layer due to temperature, along with material characterization studies by glancing incidence X-ray diffraction, atomic force microscopy, and transmission electron microscopy, are presented

  6. Effect of thickness on structural and electrical properties of Al-doped ZnO films

    International Nuclear Information System (INIS)

    In this work, we have investigated the influence of thickness on structural and electrical properties of Al-doped ZnO films. Transparent conducting oxide films were grown by the spray pyrolysis technique from precursors prepared via the sol–gel method. We determined the structural properties of the films by performing X-ray diffraction and mosaicity measurements, which evidenced an increase of disorder and inhomogeneity between crystalline domains as the films thickened. This behavior was contrasted with results obtained from electrical measurements and was attributed to plastic deformation of the films as their thickness increased. As a result, the carrier mobility, the optical gap and the activation energy are affected due to emerging grain boundaries and a higher degree of disorder. - Highlights: • Al-doped ZnO thin films on glass with different thicknesses • Film thickness affects the morphological and electrical properties. • Increasing time deposition allows modification of resistivity and Hall mobility. • Mosaicity between crystalline domains increases with film thickness

  7. Temperature dependent dual hydrogen sensor response of Pd nanoparticle decorated Al doped ZnO surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, D.; Barman, P. B.; Hazra, S. K., E-mail: surajithazra@yahoo.co.in [Department of Physics and Materials Science, Jaypee University of Information Technology, Waknaghat, Solan, Himachal Pradesh-173234 (India); Dutta, D. [IC Design and Fabrication Centre, Department of Electronics and Telecommunication Engineering, Jadavpur University, Kolkata-700032 (India); Kumar, M.; Som, T. [SUNAG Laboratory, Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India)

    2015-10-28

    Sputter deposited Al doped ZnO (AZO) thin films exhibit a dual hydrogen sensing response in the temperature range 40 °C–150 °C after surface modifications with palladium nanoparticles. The unmodified AZO films showed no response in hydrogen in the temperature range 40 °C–150 °C. The operational temperature windows on the low and high temperature sides have been estimated by isolating the semiconductor-to-metal transition temperature zone of the sensor device. The gas response pattern was modeled by considering various adsorption isotherms, which revealed the dominance of heterogeneous adsorption characteristics. The Arrhenius adsorption barrier showed dual variation with change in hydrogen gas concentration on either side of the semiconductor-to-metal transition. A detailed analysis of the hydrogen gas response pattern by considering the changes in nano palladium due to hydrogen adsorption, and semiconductor-to-metal transition of nanocrystalline Al doped ZnO layer due to temperature, along with material characterization studies by glancing incidence X-ray diffraction, atomic force microscopy, and transmission electron microscopy, are presented.

  8. Effect of thickness on structural and electrical properties of Al-doped ZnO films

    Energy Technology Data Exchange (ETDEWEB)

    Garcés, F.A., E-mail: felipe.garces@santafe-conicet.gov.ar [Instituto de Física del Litoral (CONICET-UNL), Güemes 3450, Santa Fe S3000GLN (Argentina); Budini, N. [Instituto de Física del Litoral (CONICET-UNL), Güemes 3450, Santa Fe S3000GLN (Argentina); Arce, R.D.; Schmidt, J.A. [Instituto de Física del Litoral (CONICET-UNL), Güemes 3450, Santa Fe S3000GLN (Argentina); Facultad de Ingeniería Química, Universidad Nacional del Litoral, Santiago del Estero 2829, Santa Fe S3000AOM (Argentina)

    2015-01-01

    In this work, we have investigated the influence of thickness on structural and electrical properties of Al-doped ZnO films. Transparent conducting oxide films were grown by the spray pyrolysis technique from precursors prepared via the sol–gel method. We determined the structural properties of the films by performing X-ray diffraction and mosaicity measurements, which evidenced an increase of disorder and inhomogeneity between crystalline domains as the films thickened. This behavior was contrasted with results obtained from electrical measurements and was attributed to plastic deformation of the films as their thickness increased. As a result, the carrier mobility, the optical gap and the activation energy are affected due to emerging grain boundaries and a higher degree of disorder. - Highlights: • Al-doped ZnO thin films on glass with different thicknesses • Film thickness affects the morphological and electrical properties. • Increasing time deposition allows modification of resistivity and Hall mobility. • Mosaicity between crystalline domains increases with film thickness.

  9. Structure-dependent optical and electrical transport properties of nanostructured Al-doped ZnO

    International Nuclear Information System (INIS)

    The structure–property relation of nanostructured Al-doped ZnO thin films has been investigated in detail through a systematic variation of structure and morphology, with particular emphasis on how they affect optical and electrical properties. A variety of structures, ranging from compact polycrystalline films to mesoporous, hierarchically organized cluster assemblies, are grown by pulsed laser deposition at room temperature at different oxygen pressures. We investigate the dependence of functional properties on structure and morphology and show how the correlation between electrical and optical properties can be studied to evaluate energy gap, conduction band effective mass and transport mechanisms. Understanding these properties opens up opportunities for specific applications in photovoltaic devices, where optimized combinations of conductivity, transparency and light scattering are required. (paper)

  10. Gas sensing properties of Al-doped ZnO for UV-activated CO detection

    Science.gov (United States)

    Dhahri, R.; Hjiri, M.; El Mir, L.; Bonavita, A.; Iannazzo, D.; Latino, M.; Donato, N.; Leonardi, S. G.; Neri, G.

    2016-04-01

    Al-doped ZnO (AZO) samples were prepared using a modified sol-gel route and charaterized by means of trasmission electron microscopy, x-ray diffraction and photoluminescence analysis. Resistive planar devices based on thick films of AZO deposited on interdigitated alumina substrates were fabricated and investigated as UV light activated CO sensors. CO sensing tests were performed in both dark and illumination condition by exposing the samples to UV radiation (λ  =  400 nm).Under UV light, Al-doped ZnO gas sensors operated at lower temperature than in dark. Furthermore, by photoactivation we also promoted CO sensitivity and made signal recovery of AZO sensors faster. Results demonstrate that Al-doped ZnO might be a promising sensing material for the detection of CO under UV illumination.

  11. Al-doped ZnO nanocoatings obtained by sol-gel route

    Science.gov (United States)

    Mihaiu, S.; Toader, A.; Atkinson, I.; Anastasescu, M.; Vasilescu, M.; Zaharescu, M.; Plugaru, R.

    2010-11-01

    In recent years aluminum doped zinc oxide (AZO) film has attracted more attention due to many advantages including low cost, non-toxicity, and high stability to H2 plasma in comparison with indium tin oxide (ITO) film, the best known and used transparent conductive oxide (TCO) film. In this work, mono and multilayer Al-doped ZnO coatings have been obtained by dip coating sol-gel method on the glass and silicon supports. X-ray Diffraction, Atomic Force Microscopy (AFM) and Fluorescence Spectroscopy were used for the structural, morphological and optical characterization of the obtained coatings. The multilayer Al-doped ZnO coatings (after five layer depositions) on the silicon substrate present a polycrystalline wurtzite type structure with crystallite size of 20 nm. The AFM measurements have shown that no matter the support type, the Al-doped ZnO coatings present a similar morphology consisting in a smooth distribution of the circular grains leading also to similar values of the RMS roughness, around 2 nm. The photoluminescence properties of the Al-doped ZnO coatings depend on the number of depositions and type of substrate. Systematic study performed allows finding most suitable parameters for obtaining coatings with desired properties.

  12. Effects of morphology on the thermoelectric properties of Al-doped ZnO

    DEFF Research Database (Denmark)

    Han, Li; Van Nong, Ngo; Zhang, Wei; Le, Thanh Hung; Holgate, Tim; Tashiro, Kazunari; Ohtaki, Michitaka; Pryds, Nini; Linderoth, Søren

    2014-01-01

    The nanoparticles of Al-doped ZnO were successfully grown into rod-like and platelet-like morphologies by soft chemical routes. These powders were consolidated using spark plasma sintering (SPS) technique. The samples consolidated from rods and platelets exhibited characteristic structures with...

  13. Influence of Annealing on Microstructure and Photoluminescence Properties of Al-Doped ZnO Films

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Effect of annealing temperature and time on the microstructure and photoluminescence (PL) properties of Al doped ZnO thin films deposited on Si (100) substrates by sol-gel method was investigated. An X-ray diffraction (XRD) was used to analyze the structural properties of the thin films. All the thin films have a preferential c-axis orientation, which are enhances in the annealing process. It is found from the PL measurement that near band edge (NBE) emission and deep-level (DL) emissions are observed in as-grown ZnO∶Al thin films. However, the intensity of DLE is much smaller than that of NBE. Enhancement of NBE is clearly observed after thermal annealing in air and the intensity of NBE increases with annealing temperature. Results also show that the PL spectrum is dependent not only on the processing temperature but also on the processing time. The DLE related defects can not be removed by annealing, and on the contrary, the annealing conditions actually favor their formation.

  14. Ultra-violet absorption induced modifications in bulk and nanoscale electrical transport properties of Al-doped ZnO thin films

    International Nuclear Information System (INIS)

    Using conductive atomic force microscopy and Kelvin probe force microscopy, we study local electrical transport properties in aluminum-doped zinc oxide (ZnO:Al or AZO) thin films. Current mapping shows a spatial variation in conductivity which corroborates well with the local mapping of donor concentration (∼1020 cm−3). In addition, a strong enhancement in the local current at grains is observed after exposing the film to ultra-violet (UV) light which is attributed to persistent photocurrent. Further, it is shown that UV absorption gives a smooth conduction in AZO film which in turn gives rise to an improvement in the bulk photoresponsivity of an n-AZO/p-Si heterojunction diode. This finding is in contrast to the belief that UV absorption in an AZO layer leads to an optical loss for the underneath absorbing layer of a heterojunction solar cell

  15. Ultra-violet absorption induced modifications in bulk and nanoscale electrical transport properties of Al-doped ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Mohit; Basu, Tanmoy; Som, Tapobrata, E-mail: tsom@iopb.res.in [SUNAG Laboratory, Institute of Physics, Sachivalaya Marg, Bhubaneswar 751 005 (India)

    2015-08-07

    Using conductive atomic force microscopy and Kelvin probe force microscopy, we study local electrical transport properties in aluminum-doped zinc oxide (ZnO:Al or AZO) thin films. Current mapping shows a spatial variation in conductivity which corroborates well with the local mapping of donor concentration (∼10{sup 20 }cm{sup −3}). In addition, a strong enhancement in the local current at grains is observed after exposing the film to ultra-violet (UV) light which is attributed to persistent photocurrent. Further, it is shown that UV absorption gives a smooth conduction in AZO film which in turn gives rise to an improvement in the bulk photoresponsivity of an n-AZO/p-Si heterojunction diode. This finding is in contrast to the belief that UV absorption in an AZO layer leads to an optical loss for the underneath absorbing layer of a heterojunction solar cell.

  16. On the transparent conducting oxide Al doped ZnO: First Principles and Boltzmann equations study

    Energy Technology Data Exchange (ETDEWEB)

    Slassi, A. [Institute of Nanomaterials and Nanotechnology, MAScIR, Rabat (Morocco); LMPHE (URAC 12), Faculté des Sciences, Université Mohammed V-Agdal, Rabat (Morocco); Naji, S. [LMPHE (URAC 12), Faculté des Sciences, Université Mohammed V-Agdal, Rabat (Morocco); Department of Physics, Faculty of Science, Ibb University, Ibb (Yemen); Benyoussef, A. [Institute of Nanomaterials and Nanotechnology, MAScIR, Rabat (Morocco); LMPHE (URAC 12), Faculté des Sciences, Université Mohammed V-Agdal, Rabat (Morocco); Hamedoun, M., E-mail: hamedoun@hotmail.com [Institute of Nanomaterials and Nanotechnology, MAScIR, Rabat (Morocco); El Kenz, A. [LMPHE (URAC 12), Faculté des Sciences, Université Mohammed V-Agdal, Rabat (Morocco)

    2014-08-25

    Highlights: • The incorporation of Al in ZnO increases the optical band edge absorption. • Incorporated Al creates shallow donor states of Al-3s around Fermi level. • Transmittance decreases in the visible and IR regions, while it increases in the UV region. • Electrical conductivity increases and reaches almost the saturation for high concentration of Al. - Abstract: We report, in this work, a theoretical study on the electronic, optical and electrical properties of pure and Al doped ZnO with different concentrations. In fact, we investigate these properties using both First Principles calculations within TB-mBJ approximation and Boltzmann equations under the constant relaxation time approximation for charge carriers. It is found out that, the calculated lattice parameters and the optical band gap of pure ZnO are close to the experimental values and in a good agreement with the other theoretical studies. It is also observed that, the incorporations of Al in ZnO increase the optical band edge absorption which leads to a blue shift and no deep impurities levels are induced in the band gap as well. More precisely, these incorporations create shallow donor states around Fermi level in the conduction band minimum from mainly Al-3s orbital. Beside this, it is found that, the transmittance is decreased in the visible and IR regions, while it is significantly improved in UV region. Finally, our calculations show that the electrical conductivity is enhanced as a result of Al doping and it reaches almost the saturation for high concentration of Al. These features make Al doped ZnO a transparent conducting electrode for optoelectronic device applications.

  17. Al-doped ZnO films deposited on a slightly reduced buffer layer by reactive dc unbalanced magnetron sputtering

    International Nuclear Information System (INIS)

    Al-doped ZnO (AZO) films were deposited on a fused silica glass substrate by reactive dc unbalanced magnetron sputtering using a Zn–Al (Al: 3.6 at.%) alloy target with an impedance control system. A very thin slightly reduced AZO buffer layer was inserted between the glass substrate and AZO films. For the AZO films deposited at 200 °C, the lowest resistivity in the absence of the buffer layer was 8.0 × 10−4 Ω cm, whereas this was reduced to 5.9 × 10−4 Ω cm after introducing a 5-nm-thick buffer layer. The transmittance for all the films was above 80% in the visible region. The effects of the buffer layer were analysed and discussed in detail. It is found that the insertion of the buffer layer can improve the crystallinity of the AZO film. - Highlights: • Al-doped ZnO (AZO) films with AZO buffer layers were deposited. • Reactive dc unbalance magnetron sputtering with impedance control was used. • Insertion of a buffer layer can lead to a lower resistivity. • Insertion of a buffer layer improved the crystallinity of AZO films

  18. Plasma versus thermal annealing for the Au-catalyst growth of ZnO nanocones and nanowires on Al-doped ZnO buffer layers

    Science.gov (United States)

    Güell, Frank; Martínez-Alanis, Paulina R.; Roso, Sergio; Salas-Pérez, Carlos I.; García-Sánchez, Mario F.; Santana, Guillermo; Marel Monroy, B.

    2016-06-01

    We successfully synthesized ZnO nanocones and nanowires over polycrystalline Al-doped ZnO (AZO) buffer layers on fused silica substrates by a vapor-transport process using Au-catalyst thin films. Different Au film thicknesses were thermal or plasma annealed in order to analyze their influence on the ZnO nanostructure growth morphology. Striking differences have been observed. Thermal annealing generates a distribution of Au nanoclusters and plasma annealing induces a fragmentation of the Au thin films. While ZnO nanowires are found in the thermal-annealed samples, ZnO nanocones and nanowires have been obtained on the plasma-annealed samples. Enhancement of the preferred c-axis (0001) growth orientation was demonstrated by x-ray diffraction when the ZnO nanocones and nanowires have been grown over the AZO buffer layer. The transmittance spectra of the ZnO nanocones and nanowires show a gradual increase from 375 to 900 nm, and photoluminescence characterization pointed out high concentration of defects leading to observation of a broad emission band in the visible range from 420 to 800 nm. The maximum emission intensity peak position of the broad visible band is related to the thickness of the Au-catalyst for the thermal-annealed samples and to the plasma power for the plasma-annealed samples. Finally, we proposed a model for the plasma versus thermal annealing of the Au-catalyst for the growth of the ZnO nanocones and nanowires. These results are promising for renewable energy applications, in particular for its potential application in solar cells.

  19. The crystallization and physical properties of Al-doped ZnO nanoparticles

    International Nuclear Information System (INIS)

    Un-doped Al (0-9 at.%) nanoparticles and doped ZnO powders were prepared by the sol-gel method. The nanoparticles were heated at 700-800 deg. C for 1 h in air and then analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectra and photoluminescence (PL). The results of un-doped (ZnO) and Al-doped ZnO (AZO) nanoparticles were also compared to investigate the structural characteristics and physical properties. XRD patterns of AZO powders were similar to those of ZnO powders, indicating that micro-Al ions were substituted for Zn atoms and there were no variations in the structure of the ZnO nanoparticles. From the XRD and SEM data, the grain size of the AZO nanoparticles increased from 34.41 to 40.14 nm when the annealing temperature was increased. The Raman intensity of the AZO nanoparticles (Al = 5 at.%) increased when the annealing temperature was increased. Increasing the degree of crystalline not only reduced the residual stress, but also improved the physical properties of the nanoparticles

  20. Photoluminescence, FTIR and X-ray diffraction studies on undoped and Al-doped ZnO thin films grown on polycrystalline {alpha}-alumina substrates by ultrasonic spray pyrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Djelloul, A., E-mail: djelloulabdelkader@yahoo.f [LASPI2A Laboratoire des Structures, Proprietes et Interactions Inter Atomiques, Centre Universitaire Khenchela (Algeria); Aida, M-S. [Laboratoire des Couches minces et Interface, Universite de Constantine (Algeria); Bougdira, J. [Institut Jean Lamour, UMR 7198 CNRS, Nancy Universite, UPV-Metz, Faculte des Sciences et Techniques, B.P. 239, Bd des Aiguillettes, 54506 Vandoeuvre-les-Nancy (France)

    2010-11-15

    Undoped and aluminum-doped zinc oxide (ZnO) thin films have been grown on polycrystalline {alpha}-alumina substrates by ultrasonic spray pyrolysis (USP) technique using zinc acetate dihydrate and aluminum chloride hexahydrate (Al source) dissolved in methanol, ethanol and deionized water. A number of techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and photoluminescence (PL) were used to characterize the obtained ZnO thin films. It was seen that the orientation changed with increase in substrate temperature. During the ZnO deposition Zn source reacted with polycrystalline {alpha}-Al{sub 2}O{sub 3} substrate to form an intermediate ZnAl{sub 2}O{sub 4} spinel layer. It has been interestingly found that the intensity of green emission at 2.48 eV remarkably increased when the obtained ZnO:Al films were deposited at 380 {sup o}C. The FTIR absorbance intensity of spectroscopic band at 447{+-}6 cm{sup -1} is very sensitive to oxygen sublattice disorder resulting from non-stoichiometry, which is consistent with the result of PL characterization.

  1. Glancing angle deposited Al-doped ZnO nanostructures with different structural and optical properties

    International Nuclear Information System (INIS)

    Al-doped ZnO (AZO) nanostructure arrays with different shapes (tilted rods, vertical rods, spirals, and zigzags) were fabricated by utilizing glancing angle deposition (GLAD) technique in a DC sputter growth unit at room temperature. During GLAD, all the samples were tilted at an oblique angle of about 90° with respect to incoming flux direction. In order to vary the shapes of nanostructures, each sample was rotated at different speeds around the substrate normal axis. Rotation speed did not only affect the shape but also changed the microstructural and optical properties of GLAD AZO nanostructures. The experimental results reveal that GLAD AZO nanostructures of different shapes each have unique morphological, crystal structure, mechanical, and optical properties determined by scanning electron microscopy, X-ray diffraction, transmission, and reflectance measurements. Vertical nanorods display the largest grain size, minimum strain, lowest defect density, and highest optical transmittance compared to the other shapes. Growth dynamics of GLAD has been discussed to explain the dependence of structural and optical properties of nanostructures on the substrate rotation speed. - Highlights: • Al-doped ZnO (AZO) nanostructures with different shapes were fabricated. • They have unique morphological, crystal structure, and optical properties. • Vertical AZO nanorods show an enhanced optical transmittance

  2. Glancing angle deposited Al-doped ZnO nanostructures with different structural and optical properties

    Energy Technology Data Exchange (ETDEWEB)

    Yildiz, A., E-mail: yildizab@gmail.com [Department of Physics and Astronomy, University of Arkansas at Little Rock, Little Rock, AR 72204 (United States); Department of Energy Systems Engineering, Faculty of Engineering and Natural Sciences, Yıldırım Beyazıt University, Ankara (Turkey); Cansizoglu, H. [Department of Physics and Astronomy, University of Arkansas at Little Rock, Little Rock, AR 72204 (United States); Turkoz, M. [Department of Physics and Astronomy, University of Arkansas at Little Rock, Little Rock, AR 72204 (United States); Department of Electrical-Electronic Engineering, Faculty of Engineering, University of Karabuk, Karabuk (Turkey); Abdulrahman, R.; Al-Hilo, Alaa; Cansizoglu, M.F.; Demirkan, T.M.; Karabacak, T. [Department of Physics and Astronomy, University of Arkansas at Little Rock, Little Rock, AR 72204 (United States)

    2015-08-31

    Al-doped ZnO (AZO) nanostructure arrays with different shapes (tilted rods, vertical rods, spirals, and zigzags) were fabricated by utilizing glancing angle deposition (GLAD) technique in a DC sputter growth unit at room temperature. During GLAD, all the samples were tilted at an oblique angle of about 90° with respect to incoming flux direction. In order to vary the shapes of nanostructures, each sample was rotated at different speeds around the substrate normal axis. Rotation speed did not only affect the shape but also changed the microstructural and optical properties of GLAD AZO nanostructures. The experimental results reveal that GLAD AZO nanostructures of different shapes each have unique morphological, crystal structure, mechanical, and optical properties determined by scanning electron microscopy, X-ray diffraction, transmission, and reflectance measurements. Vertical nanorods display the largest grain size, minimum strain, lowest defect density, and highest optical transmittance compared to the other shapes. Growth dynamics of GLAD has been discussed to explain the dependence of structural and optical properties of nanostructures on the substrate rotation speed. - Highlights: • Al-doped ZnO (AZO) nanostructures with different shapes were fabricated. • They have unique morphological, crystal structure, and optical properties. • Vertical AZO nanorods show an enhanced optical transmittance.

  3. On performance limitations and property correlations of Al-doped ZnO deposited by radio-frequency sputtering

    DEFF Research Database (Denmark)

    Crovetto, Andrea; Ottsen, Tobias Sand; Stamate, Eugen;

    2016-01-01

    The electrical properties of RF-sputtered Al-doped ZnO are often spatially inhomogeneous and strongly dependent on deposition parameters. In this work, we study the mechanisms that limit the minimum resistivity achievable under different deposition regimes. In a low- and intermediate-pressure reg......The electrical properties of RF-sputtered Al-doped ZnO are often spatially inhomogeneous and strongly dependent on deposition parameters. In this work, we study the mechanisms that limit the minimum resistivity achievable under different deposition regimes. In a low- and intermediate...

  4. Complex hierarchical arrangements of stacked nanoplates in Al-doped ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Ortega, Y. [Departamento de Fisica de Materiales, Facultad de Ciencias Fisicas, Universidad Complutense de Madrid, 28040 Madrid (Spain); Mikrostrukturanalytik, Christian-Albrechts Universitaet zu Kiel, 24143 Kiel (Germany); Haeussler, D.; Jaeger, W. [Mikrostrukturanalytik, Christian-Albrechts Universitaet zu Kiel, 24143 Kiel (Germany); Piqueras, J.; Fernandez, P. [Departamento de Fisica de Materiales, Facultad de Ciencias Fisicas, Universidad Complutense de Madrid, 28040 Madrid (Spain)

    2012-08-15

    Al-doped micro- and nanostructures have been grown by an evaporation-deposition method with a mixture of ZnS and Al{sub 2}O{sub 3} powders as precursor. It has been found that the presence of Al is the cause of the growth of complex morphologies, as rods formed by stacks of nanoplates and other complex hierarchical structures. The role of Al in the growth process has been investigated by electron microscopy techniques. Al-rich particles in specific sites of a central rod lead to hierarchical growth. Transmission electron microscopy shows that in some cases the Al-rich zones are clusters of spinel ZnAl{sub 2}O{sub 4} nanoparticles adhered to ZnO nanorods. Al incorporation into the structures and the dopant effect on the luminescence behavior of the ZnO structures were investigated by energy dispersive spectroscopy and by cathodoluminescence. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Growth and properties of electrodeposited transparent Al-doped ZnO nanostructures

    Science.gov (United States)

    Baka, O.; Mentar, L.; Khelladi, M. R.; Azizi, A.

    2015-12-01

    Al-doped zinc oxide (AZO) nanostructures were fabricated on fluorine-doped tin-oxide (FTO)- coated glass substrates by using electrodeposition. The effects of the doping concentration of Al on the morphological, microstructural, electrical and optical properties of the nanostructures were investigated. From the field emission scanning electron microscopy (FE-SEM) observation, when the amount of Al was increased in the solution, the grains size was observed to decreases. The observed changes in the morphology indicate that Al acts as nucleation centers in the vacancy sites of ZnO and destroys the crystalline structure at high doping level. Effectively, the X-ray diffraction (XRD) analysis indicated that the undoped and the doped ZnO nanostructures has a polycrystalline nature and a hexagonal wurtzite structure with a (002) preferential orientation. The photoluminescence (PL) room-temperature measurements showed that the incorporation of Al in the Zn lattice can improve the intensity of ultraviolet (UV) emission, thus suggesting its greater prospects for use in UV optoelectronic devices.

  6. Structural and luminescence properties of pure and Al-doped ZnO nanopowders

    Energy Technology Data Exchange (ETDEWEB)

    Louiza, Arab; Saliha, Hamdelou; Sofiane, Harouni [Laboratory of Physics-Chemistry of Semiconductors, Department of Physics, University Mentouri, Constantine 25000 (Algeria); Kamel, Guergouri, E-mail: kamelguergouri@yahoo.com [Laboratory of Physics-Chemistry of Semiconductors, Department of Physics, University Mentouri, Constantine 25000 (Algeria); Lakhder, Guerbous [Algiers Nuclear Research Center, Algiers 16000 (Algeria)

    2012-06-25

    Highlights: Black-Right-Pointing-Pointer The powders follow the wuertzite structure and possess a very small size. Black-Right-Pointing-Pointer The grain size deceases as a function of Al concentration. Black-Right-Pointing-Pointer The powders' morphology evaluates with increasing Al concentration from pebbles without cavities to highly porous powder. Black-Right-Pointing-Pointer The blue luminescence peaks of the PL spectrum covering the green to the ultraviolet area are the most intense. Black-Right-Pointing-Pointer The violet luminescence intensity decreases with increasing Al concentration. - Abstract: Pure and Al doped zinc oxide nanopowders have been synthesized by sol-gel route. This is a simple and inexpensive method permitting to obtain a very small grain size powders. Zinc acetate dehydrate was first dissolved in a mixture of 2-methoxyethanol and mono-ethanolamine (MEA) solution, were used as a solvent and stabilizer respectively and doped with a quantity of aluminum nitrate, varying from 0 to 10 mol%. The obtained gel is then calcinated in air at 500 Degree-Sign C. The samples are characterized by XRD, SEM and photoluminescence (PL) studies. The XRD results indicate that pure and Al-doped ZnO powders are solid solutions crystallizing in pure wuertzite structure, and consisted of a mixture of nanoparticles with grain size between 23 and 36 nm. The grain size decreases strongly with increasing Al concentration and reaches its lowest value at 5 mol% Al. The PL spectra show that the most important establishment is that the powders show luminescence peaks from green to ultraviolet light, and thus can be used to manufacture transmitters using these emissions. The peaks connected to the blue luminescence are the most intense, and they are generated by transitions involving (Zn{sub i}). The SEM images show a formation of pebbles with sizes decreasing with Al concentration and a morphology evaluating, qualitatively, from pebbles without cavities to highly

  7. Enhanced photoluminescence and Raman properties of Al-Doped ZnO nanostructures prepared using thermal chemical vapor deposition of methanol assisted with heated brass.

    Directory of Open Access Journals (Sweden)

    Tamil Many K Thandavan

    Full Text Available Vapor phase transport (VPT assisted by mixture of methanol and acetone via thermal evaporation of brass (CuZn was used to prepare un-doped and Al-doped zinc oxide (ZnO nanostructures (NSs. The structure and morphology were characterized by field emission scanning electron microscopy (FESEM and x-ray diffraction (XRD. Photoluminescence (PL properties of un-doped and Al-doped ZnO showed significant changes in the optical properties providing evidence for several types of defects such as zinc interstitials (Zni, oxygen interstitials (Oi, zinc vacancy (Vzn, singly charged zinc vacancy (VZn-, oxygen vacancy (Vo, singly charged oxygen vacancy (Vo+ and oxygen anti-site defects (OZn in the grown NSs. The Al-doped ZnO NSs have exhibited shifted PL peaks at near band edge (NBE and red luminescence compared to the un-doped ZnO. The Raman scattering results provided evidence of Al doping into the ZnO NSs due to peak shift from 145 cm-1 to an anomalous peak at 138 cm-1. Presence of enhanced Raman signal at around 274 and 743 cm-1 further confirmed Al in ZnO NSs. The enhanced D and G band in all Al-doped ZnO NSs shows possible functionalization and doping process in ZnO NSs.

  8. Enhanced photoluminescence and Raman properties of Al-Doped ZnO nanostructures prepared using thermal chemical vapor deposition of methanol assisted with heated brass.

    Science.gov (United States)

    Thandavan, Tamil Many K; Gani, Siti Meriam Abdul; San Wong, Chiow; Md Nor, Roslan

    2015-01-01

    Vapor phase transport (VPT) assisted by mixture of methanol and acetone via thermal evaporation of brass (CuZn) was used to prepare un-doped and Al-doped zinc oxide (ZnO) nanostructures (NSs). The structure and morphology were characterized by field emission scanning electron microscopy (FESEM) and x-ray diffraction (XRD). Photoluminescence (PL) properties of un-doped and Al-doped ZnO showed significant changes in the optical properties providing evidence for several types of defects such as zinc interstitials (Zni), oxygen interstitials (Oi), zinc vacancy (Vzn), singly charged zinc vacancy (VZn-), oxygen vacancy (Vo), singly charged oxygen vacancy (Vo+) and oxygen anti-site defects (OZn) in the grown NSs. The Al-doped ZnO NSs have exhibited shifted PL peaks at near band edge (NBE) and red luminescence compared to the un-doped ZnO. The Raman scattering results provided evidence of Al doping into the ZnO NSs due to peak shift from 145 cm-1 to an anomalous peak at 138 cm-1. Presence of enhanced Raman signal at around 274 and 743 cm-1 further confirmed Al in ZnO NSs. The enhanced D and G band in all Al-doped ZnO NSs shows possible functionalization and doping process in ZnO NSs. PMID:25756598

  9. A Study of Structural and Photoluminescence for Al-Doped CdO Thin Films

    Directory of Open Access Journals (Sweden)

    Bong Ju Lee

    2016-01-01

    Full Text Available Al-doped CdO thin films were prepared by radio frequency magnetron sputtering at different deposition time and substrate temperature. X-ray diffraction showed that the changes in the intensities of the (200, (220, and (311 planes followed a similar trend with increase in deposition time. The surface of the thin film was examined by scanning electron microscopy. Grain sizes of Al-doped CdO thin films increased significantly with increasing deposition time. The film thicknesses were 0.09, 0.12, 0.20, and 0.225 μm for the deposition times of 1, 2, 3, and 4 h, respectively. The photoluminescence spectra of the Al-doped CdO thin films were measured at room temperature. The photoluminescence wavelength changed in the sequence, green, blue, green, and blue, with increasing deposition time, which indicates that blue light emitting films can be fabricated by adjusting the processing parameters.

  10. Effect of energetic electron beam treatment on transparent conductive ZnO thin films

    International Nuclear Information System (INIS)

    Undoped and Al-doped ZnO thin films were prepared by a sol–gel spin coating method. The films were exposed to the electron beam at different energies to improve their electrical properties by modifying their film crystallinity. For both the undoped and Al-doped ZnO thin films, the carrier concentration significantly increased and the resistivity decreased after the introduction of the energetic electron beam. Since band gap widening of the undoped and Al-doped ZnO thin films was also observed with exposure to the electron beam, the behaviors and tendencies can be explained by the Burstein–Moss effect. The effects of the electron beam on ZnO thin film properties, including band gap widening, increasing carrier concentration, and significantly decreased resistivity, were similar to the effects of Al doping in ZnO. Finally, by combining electron beam treatment and Al doping of ZnO thin films prepared by a sol–gel method, the resistivity of the sol–gel synthesized ZnO thin film decreased from 5.8 × 102 Ω cm to 8.2 × 10−2 Ω cm. According to the Monte Carlo simulation of electron penetration in the ZnO thin film, the penetration depth increased with electron beam energy, which induced lattice heating and atomic rearrangement by electronic excitation in a collision cascade. - Highlights: • Electron beam treatment on ZnO thin films by sol–gel spin coating synthesis • Improvement of crystallinity and increase in the optical band gap energy • Decrease in the resistivity with the increase in the carrier concentration • Increase in the electron penetration depth with beam energy

  11. 绒面AZO最新研究进展及应用%Recent development and application of surface-textured Al doped ZnO transparent conductive oxide thin films

    Institute of Scientific and Technical Information of China (English)

    王文娜; 张大伟; 黄元申; 倪争技; 庄松林

    2012-01-01

    Aluminum doped zinc oxide(AZO) transparent conductive thin films as a kind of transparent conductive film(TCO) have received a wide attention by researchers because of their superior photoelectric performance,and are considered as the replacement materials of the current large-scale use of the traditional indium tin oxide(ITO).Furthermore,surface-textured AZO has been considered an ideal material for the former electrode of solar cells due to its low resistivity,high transmittance and excellent liglht trapping effect which can improve the conversion efficiency of solar cells.Thestatus of preparation and properties of AZO transparent conductive thin filmsare reviewed;in addition,the AZO research trends and future research directions are pointed out based on the research situation home and abroad.%掺铝氧化锌(AZO)透明导电膜作为一种光电性能优异的透明导电膜(TCO)受到研究人员的广泛关注,并被认为是当前大规模使用的传统铟锡氧化物(ITO)的替换材料。绒面AZO薄膜因其电阻率低、高透过率且具有良好的陷光效果,可以提高太阳能电池的光电转换效率,而被认为是太阳能电池前电极的理想材料。综述了绒面AZO透明导电膜的制备方法和性能研究现状,并针对AZO的国内外研究状况提出了今后的发展趋势和研究方向。

  12. Pulsed laser deposition of epitaxial Al-doped ZnO film on sapphire with GaN buffer layer

    International Nuclear Information System (INIS)

    Al-doped ZnO (ZnO:Al) films with thickness in the range of 0.5-0.9 μm were grown epitaxially on epi-GaN/sapphire (0001) by pulsed laser deposition (PLD; XeCl, λ=308 nm). The growth parameters such as substrate temperature, oxygen pressure and pulse repetition rate were established in a sequential manner to obtain highly epitaxial ZnO:Al film. The best films were obtained at substrate temperature of 400 deg. C, oxygen pressure of 1 mTorr and pulse repetition rate of 5 Hz. Reflection high-energy electron diffraction (RHEED) and low temperature photoluminescence (PL) studies confirm the high quality epitaxial nature of the film with near match and stacking order between ZnO and GaN

  13. Enhanced Photoluminescence and Raman Properties of Al-Doped ZnO Nanostructures Prepared Using Thermal Chemical Vapor Deposition of Methanol Assisted with Heated Brass

    OpenAIRE

    Thandavan, Tamil Many K.; Gani, Siti Meriam Abdul; San Wong, Chiow; Md. Nor, Roslan

    2015-01-01

    Vapor phase transport (VPT) assisted by mixture of methanol and acetone via thermal evaporation of brass (CuZn) was used to prepare un-doped and Al-doped zinc oxide (ZnO) nanostructures (NSs). The structure and morphology were characterized by field emission scanning electron microscopy (FESEM) and x-ray diffraction (XRD). Photoluminescence (PL) properties of un-doped and Al-doped ZnO showed significant changes in the optical properties providing evidence for several types of defects such as ...

  14. Al-doped ZnO contact to CdZnTe for x- and gamma-ray detector applications

    Science.gov (United States)

    Roy, U. N.; Camarda, G. S.; Cui, Y.; Gul, R.; Hossain, A.; Yang, G.; Mundle, R. M.; Pradhan, A. K.; James, R. B.

    2016-06-01

    The poor adhesion of common metals to CdZnTe (CZT)/CdTe surfaces has been a long-standing challenge for radiation detector applications. In this present work, we explored the use of an alternative electrode, viz., Al-doped ZnO (AZO) as a replacement to common metallic contacts. ZnO offers several advantages over the latter, such as having a higher hardness, a close match of the coefficients of thermal expansion for CZT and ZnO, and better adhesion to the surface of CZT due to the contact layer being an oxide. The AZO/CZT contact was investigated via high spatial-resolution X-ray response mapping for a planar detector at the micron level. The durability of the device was investigated by acquiring I-V measurements over an 18-month period, and good long-term stability was observed. We have demonstrated that the AZO/CZT/AZO virtual-Frisch-grid device performs fairly well, with comparable or better characteristics than that for the same detector fabricated with gold contacts.

  15. Polymer solar cells with efficiency >10% enabled via a facile solution-processed Al-doped ZnO electron transporting layer

    KAUST Repository

    Jagadamma, Lethy Krishnan

    2015-10-05

    The present work details a facile and low-temperature (125C) solution-processed Al-doped ZnO (AZO) buffer layer functioning very effectively as electron accepting/hole blocking layer for a wide range of polymer:fullerene bulk heterojunction systems, and yielding power conversion efficiency in excess of 10% (8%) on glass (plastic) substrates. We show that ammonia addition to the aqueous AZO nanoparticle solution is a critically important step toward producing compact and smooth thin films which partially retain the aluminum doping and crystalline order of the starting AZO nanocrystals. The ammonia treatment appears to reduce the native defects via nitrogen incorporation, making the AZO film a very good electron transporter and energetically matched with the fullerene acceptor. Importantly, highly efficient solar cells are achieved without the need for additional surface chemical passivation or modification, which has become an increasingly common route to improving the performance of evaporated or solution-processed ZnO ETLs in solar cells.

  16. Synthesis of High Crystalline Al-Doped ZnO Nanopowders from Al2O3 and ZnO by Radio-Frequency Thermal Plasma

    Directory of Open Access Journals (Sweden)

    Min-Kyeong Song

    2015-01-01

    Full Text Available High crystalline Al-doped ZnO (AZO nanopowders were prepared by in-flight treatment of ZnO and Al2O3 in Radio-Frequency (RF thermal plasma. Micron-sized (~1 μm ZnO and Al2O3 powders were mixed at Al/Zn ratios of 3.3 and 6.7 at.% and then injected into the RF thermal plasma torch along the centerline at a feeding rate of 6.6 g/min. The RF thermal plasma torch system was operated at the plate power level of ~140 kVA to evaporate the mixture oxides and the resultant vapor species were condensed into solid particles by the high flow rate of quenching gas (~7000 slpm. The FE-SEM images of the as-treated powders showed that the multipod shaped and the whisker type nanoparticles were mainly synthesized. In addition, these nanocrystalline structures were confirmed as the single phase AZO nanopowders with the hexagonal wurtzite ZnO structure by the XRD patterns and FE-TEM results with the SAED image. However, the composition changes of 0.3 and 1.0 at.% were checked for the as-synthesized AZO nanopowders at Al/Zn ratios of 3.3 and 6.7 at.%, respectively, by the XRF data, which can require the adjustment of Al/Zn in the mixture precursors for the applications of high Al doping concentrations.

  17. Electrical stability of Al-doped ZnO transparent electrode prepared by sol-gel method

    Science.gov (United States)

    Tabassum, Samia; Yamasue, Eiji; Okumura, Hideyuki; Ishihara, Keiichi N.

    2016-07-01

    Al-doped zinc oxide (AZO) thin films have been considered as a promising alternative to tin doped indium oxide (ITO), which is currently used in various optoelectronic applications. However, the environmental stability of AZO film is not satisfactory, in that the resistivity is significantly increases in air. Here, we investigate the resistivity stability of AZO thin films prepared by sol-gel method using various annealing temperatures and durations. The degradation of resistivity property was observed for AZO films stored in ambient or damp heat environment, where the degradation rate was influenced by annealing temperature. A significant improvement of electrical stability was attained in AZO films that were prepared at high annealing temperature. The films, which showed the highest and the lowest increasing rate of resistivity, were further characterized in detail to shed light on the possible mechanisms explaining the improved stability through crystallinity, surface morphology and elemental state of the thin film.

  18. Growth of Al-doped ZnO films with tilted nano-columns on r-cut sapphire substrates by pulsed laser deposition

    International Nuclear Information System (INIS)

    2 wt.% Al2O3-doped ZnO (AZO) thin films in both single layer and bi-layer forms were deposited on α-Al2O3 (011¯2) (r-cut) and (0001) (c-cut) substrates by a pulsed laser deposition technique. Single layer AZO films were grown under either vacuum or 33.3 Pa of O2 pressure. Bilayer AZO films were grown with a sequential deposition of a uniform template layer under vacuum and a nano-column-structured layer under 33.3 Pa of O2 pressure. Interestingly, single layer AZO film grown on r-cut sapphire in high oxygen pressure (33.3 Pa) shows tilted grain boundaries along [1¯102¯]AZO. The bilayer film deposited on r-cut substrate shows tilted nano-column growth while the film grown on c-cut substrate has vertically grown nano-columns. The results of X-ray diffraction and cross-section transmission electron microscopy studies show a systematic variation of the d-spacing of (0002)AZO and (112¯0)AZO for all AZO films. Electrical resistivity was measured and found to be strongly dependent on the different microstructures achieved under different oxygen pressures and substrates. - Highlights: ► 2 wt.% Al doped ZnO (AZO) thin film grown on r-cut sapphire under 33.3 Pa of O2 ► Tiled boundary along [1¯102¯]AZO observed as a result of internal lattice strain ► Tilted nano-column processed after sequential deposition under vacuum and 33.3 Pa of O2 ► Significantly reduced electrical resistivity observed for the films on r-cut sapphire

  19. Polymer Solar Cells with Efficiency >10% Enabled via a Facile Solution-Processed Al-Doped ZnO Electron Transporting Layer

    KAUST Repository

    Jagadamma, Lethy Krishnan

    2015-04-22

    A facile and low-temperature (125 °C) solution-processed Al-doped ZnO (AZO) buffer layer functioning very effectively as electron accepting/hole blocking layer for a wide range of polymer:fullerene bulk heterojunction systems, yielding power conversion efficiency in excess of 10% (8%) on glass (plastic) substrates is described. The ammonia-treatment of the aqueous AZO nanoparticle solution produces compact, crystalline, and smooth thin films, which retain the aluminum doping, and eliminates/reduces the native defects by nitrogen incorporation, making them good electron transporters and energetically matched with the fullerene acceptor. It is demonstrated that highly efficient solar cells can be achieved without the need for additional surface chemical modifications of the buffer layer, which is a common requirement for many metal oxide buffer layers to yield efficient solar cells. Also highly efficient solar cells are achieved with thick AZO films (>50 nm), highlighting the suitability of this material for roll-to-roll coating. Preliminary results on the applicability of AZO as electron injection layer in F8BT-based polymer light emitting diode are also presented. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Local probe microscopic studies on Al-doped ZnO: Pseudoferroelectricity and band bending at grain boundaries

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Mohit; Basu, Tanmoy; Som, Tapobrata, E-mail: tsom@iopb.res.in [SUNAG Laboratory, Institute of Physics, Sachivalaya Marg, Bhubaneswar 751 005 (India)

    2016-01-07

    In this paper, based on piezoforce measurements, we show the presence of opposite polarization at grains and grain boundaries of Al-doped ZnO (AZO). The polarization can be flipped by 180° in phase by switching the polarity of the applied electric field, revealing the existence of nanoscale pseudoferroelectricity in AZO grown on Pt/TiO{sub 2}/SiO{sub 2}/Si substrate. We also demonstrate an experimental evidence on local band bending at grain boundaries of AZO films using conductive atomic force microscopy and Kelvin probe force microscopy. The presence of an opposite polarization at grains and grain boundaries gives rise to a polarization-driven barrier formation at grain boundaries. With the help of conductive atomic force microscopy, we show that the polarization-driven barrier along with the defect-induced electrostatic potential barrier account for the measured local band bending at grain boundaries. The present study opens a new avenue to understand the charge transport in light of both polarization and electrostatic effects.

  1. The Influence of α- and γ-Al2O3 Phases on the Thermoelectric Properties of Al-doped ZnO

    DEFF Research Database (Denmark)

    Han, Li; Van Nong, Ngo; Le, Thanh Hung; Holgate, Tim; Pryds, Nini; Ohtaki, Michitaka; Linderoth, Søren

    2013-01-01

    A systematic investigation on the microstructure and thermoelectric properties of Al-doped ZnO using α- and γ-Al2O3 as dopants was conducted in order to understand the doping effect and its mechanism. The samples were prepared by the spark plasma sintering technique from precursors calcined at...... various temperatures. Clear differences in microstructure and thermoelectric properties were observed between the samples doped with α- and γ-Al2O3. At any given calcination temperature, γ-Al2O3 resulted in the formation of a larger amount of the ZnAl2O4 phase in the Al-doped ZnO samples. The average...... exhibited by these samples. The γ-Al2O3 promoted the substitution for donor impurities in ZnO, thus resulting in shrinkage of the unit cell volume and an increase in the electrical conductivity compared with the α-Al2O3-doped ZnO. At a calcination temperature of 1173K, the γ-Al2O3-doped sample showed a ZT...

  2. On the variations of optical property and electronic structure in heavily Al-doped ZnO films during double-step growth process

    International Nuclear Information System (INIS)

    We have investigated the variations of optical property and electronic structure in heavily Al-doped ZnO (AZO) films during the growth process, which were formed by first creating Zn vacancies in O2-rich atmosphere and second filling the vacancies with Zn atoms in Zn-vapor atmosphere. After the first step, the high-resistance AZO films have the same optical bandgap with nominally undoped ZnO, indicating that negligible variations in the fundamental bandgap happened to the AZO films although Al atom was incorporated into the ZnO lattice. After the second step, once free electrons were brought into the lattice by Zn-filling, the optical transition energy blueshifts due to the band-filling effect. X-ray absorption fine structure measurements suggest that Zn-filling process decreased the unoccupied states of the conduction band, but not raised the conduction band minimum

  3. Poole-Frenkel effect on electrical characterization of Al-doped ZnO films deposited on p-type GaN

    International Nuclear Information System (INIS)

    This paper presents the electrical properties of Al-doped ZnO (AZO) films directly grown on two types of p-type GaN thin films. The low-pressure p-GaN thin films (LP-p-GaN) exhibited structural properties of high-density edge-type threading dislocations (TDs) and compensated defects (i.e., nitrogen vacancy). Compared with high-pressure p-GaN thin films (HP-p-GaN), X-ray photoemission spectroscopy of Ga 3d core levels indicated that the surface Fermi-level shifted toward the higher binding-energy side by approximately 0.7 eV. The high-density edge-type TDs and compensated defects enabled surface Fermi-level shifting above the intrinsic Fermi-level, causing the surface of LP-p-GaN thin films to invert to n-type semiconductor. A highly nonlinear increase in leakage current regarding reverse-bias voltage was observed for AZO/LP-p-GaN. The theoretical fits for the reverse-bias voltage region indicated that the field-assisted thermal ionization of carriers from defect associated traps, which is known as the Poole-Frenkel effect, dominated the I-V behavior of AZO/LP-p-GaN. The fitting result estimated the trap energy level at 0.62 eV below the conduction band edge. In addition, the optical band gap increased from 3.50 eV for as-deposited AZO films to 3.62 eV for 300 °C annealed AZO films because of the increased carrier concentration. The increasing Fermi-level of the 300 °C annealed AZO films enabled the carrier transport to move across the interface into the LP-p-GaN thin films without any thermal activated energy. Thus, the Ohmic behavior of AZO contact can be achieved directly on the low-pressure p-GaN films at room temperature

  4. Solution processed Al doped ZnO film fabrication through electrohydrodynamic atomization

    International Nuclear Information System (INIS)

    In this study, highly transparent, 250 nm thick films of Aluminum doped Zinc-oxide (ZnO:Al) are achieved on glass substrates at ambient conditions through a solution processing technique called electrohydrodynamic atomization. A 10 wt.% monodispersed solution containing 6% ZnO:Al nanoparticles (ZnO/Al2O3) in ethanol has been synthesized first and then used in the deposition process as the working solution. Pure and uniform transparent films with an average transmittance of 93% have been deposited with crystal structure exhibiting both zincite and gahnite phases. Surface composition purity has been confirmed using X-ray photoelectron spectroscopy technique and the clear indication of Zn-2p and Al-2p peaks confirms surface integrity. Fourier Transform Infrared analysis further confirms the presence of aluminum in the samples. The electrical properties are studied by recording and analyzing the current–voltage (I–V) measurements and the resistivity has been estimated from the slope of the IV-curve which is approximately 25 mΩ.cm. The layer roughness has been characterized using atomic force microscopy. - Highlights: ►Aluminum doped Zinc oxide (ZnO:Al) films are made via electrohydrodynamic atomization. ►ZnO:Al nano-particle ink is used to form thin films in single step at room conditions. ►Scanning electron and atomic force microscopes confirm fine layer characteristics. ►X-ray photoelectron and Fourier Transform-Infrared spectroscope confirm film purity. ►Transparent and conductive films have been fabricated with wurtzite structure.

  5. The Influence of α- and γ-Al2O3 Phases on the Thermoelectric Properties of Al-doped ZnO

    OpenAIRE

    Han, Li; Van Nong, Ngo; Le, Thanh Hung; Holgate, Tim; Pryds, Nini; Ohtaki, Michitaka; Linderoth, Søren

    2012-01-01

    A systematic investigation on the microstructure and thermoelectric properties of Al-doped ZnO using α- and γ-Al2O3 as dopants was conducted in order to understand the doping effect and its mechanism. The samples were prepared by the spark plasma sintering technique from precursors calcined at various temperatures. Clear differences in microstructure and thermoelectric properties were observed between the samples doped with α- and γ-Al2O3. At any given calcination temperature, γ-Al2O3 resulte...

  6. Micro/Nano hierarchical peony-like Al doped ZnO superhydrophobic film: The guiding effect of (100) preferred seed layer

    OpenAIRE

    Yang Li; Jingfeng Wang; Yi Kong; Jia Zhou; Jinzhu Wu; Gang Wang; Hai Bi; Xiaohong Wu; Wei Qin; Qingkun Li

    2016-01-01

    In this communication, we present a versatile and controllable strategy for formation of superhydrophobic micro/nano hierarchical Al doped ZnO (AZO) films with a water contact angle (CA) of 170 ± 4°. This strategy involves a two-step layer-by-layer process employing an atomic layer deposition (ALD) technique followed by a hydrothermal method, and the resulting novel AZO surface layer consists of (100) dominant nano-rice-like AZO seed layer (the water CA of 110 ± 4°) covered with micro-peony-l...

  7. Effect of aluminium doping on structural and optical properties of ZnO thin films by sol-gel method

    International Nuclear Information System (INIS)

    We systematically investigated the structural, morphological and optical properties of 0.05 mol % Al doped ZnO (Al:ZnO) thin films deposited on glass substrates by sol-gel spin coating method. The influences of Al doping in ZnO thin films are characterized by Powder X-ray diffraction study. ZnO and Al:ZnO thin films have showed hexagonal wurtzite structure without any secondary phase in c-axis (002) orientation. The SEM images also proved the hexagonal rod like morphologies for both films. All the films exhibited transmittance of 70-80% in the visible range up to 800 nm and cut-off wavelength observed at ∼390 nm corresponding to the fundamental absorption of ZnO. The band gap of the ZnO thin films slightly widened with the Al doping. The photoluminescence properties have been studied for Al: ZnO thin films and the results are presented in detail

  8. Pressurized polyol synthesis of Al-doped ZnO nanoclusters with high electrical conductivity and low near-infrared transmittance

    International Nuclear Information System (INIS)

    Highlights: • Low-temperature pressurized polyol method synthesized Al-doped ZnO nanoclusters. • Reaction time affected the doping efficiency, resistivity, and NIR transmittance. • The near-IR blocking efficiency of Al-doped ZnO (AZO) nanoclusters reached 85%. • AZO nanocluster coatings could be used for heat reflectors or artificial glasses. - Abstract: In this study, a novel pressurized polyol method is proposed to synthesize aluminum-doped ZnO (AZO) nanoclusters without utilizing additional thermal treatment to avoid the merging of nanoclusters. The size of the AZO nanoclusters range from 100 to 150 nm with a resistivity of 204 Ω cm. The AZO nanoclusters primarily consist of approximately 10-nm nanocrystals that form a spherically clustered morphology. A two-stage growth model has been proposed based on the results of scanning electron microscopy and transmission electron microscopy images, nanocluster sizes, and X-ray diffraction patterns. The primary AZO nanocrystals first nucleate under pressurized conditions and then spontaneously aggregate into larger nanoclusters. Optically, the AZO nanoclusters exhibit a significant decrease in the near-infrared (NIR) transmittance compared to pure ZnO nanoparticles. The NIR blocking efficiency of AZO nanoclusters reached 85%. Moreover, the doping efficiency, resistivity, and NIR transmittance of AZO nanoclusters are influenced by the reaction time in the pressurized polyol solution. On the other hand, the reaction time has no effect on the particle size and crystallinity. An optically transparent coating for the AZO nanoclusters, which consisted of iso-propanol solvent and ultraviolet-curable acrylic binder, was also demonstrated

  9. Pressurized polyol synthesis of Al-doped ZnO nanoclusters with high electrical conductivity and low near-infrared transmittance

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ho-Nyun; Shin, Chi-Ho [Surface Technology R& BD Group, Korea Institute of Industrial Technology (KITECH), Incheon 406-840 (Korea, Republic of); Hwang, Duck Kun [Department of Corporate Diagnosis, Small and Medium Business Corporation, Seoul 150-718 (Korea, Republic of); Kim, Haekyoung [School of Materials Science and Engineering, Yeungnam University, Gyeongsan 712-749 (Korea, Republic of); Oh, Kyeongseok [Department of Chemical and Environmental Technology, Inha Technical College, Incheon 402-752 (Korea, Republic of); Kim, Hyun-Jong, E-mail: hjkim23@kitech.re.kr [Surface Technology R& BD Group, Korea Institute of Industrial Technology (KITECH), Incheon 406-840 (Korea, Republic of)

    2015-09-25

    Highlights: • Low-temperature pressurized polyol method synthesized Al-doped ZnO nanoclusters. • Reaction time affected the doping efficiency, resistivity, and NIR transmittance. • The near-IR blocking efficiency of Al-doped ZnO (AZO) nanoclusters reached 85%. • AZO nanocluster coatings could be used for heat reflectors or artificial glasses. - Abstract: In this study, a novel pressurized polyol method is proposed to synthesize aluminum-doped ZnO (AZO) nanoclusters without utilizing additional thermal treatment to avoid the merging of nanoclusters. The size of the AZO nanoclusters range from 100 to 150 nm with a resistivity of 204 Ω cm. The AZO nanoclusters primarily consist of approximately 10-nm nanocrystals that form a spherically clustered morphology. A two-stage growth model has been proposed based on the results of scanning electron microscopy and transmission electron microscopy images, nanocluster sizes, and X-ray diffraction patterns. The primary AZO nanocrystals first nucleate under pressurized conditions and then spontaneously aggregate into larger nanoclusters. Optically, the AZO nanoclusters exhibit a significant decrease in the near-infrared (NIR) transmittance compared to pure ZnO nanoparticles. The NIR blocking efficiency of AZO nanoclusters reached 85%. Moreover, the doping efficiency, resistivity, and NIR transmittance of AZO nanoclusters are influenced by the reaction time in the pressurized polyol solution. On the other hand, the reaction time has no effect on the particle size and crystallinity. An optically transparent coating for the AZO nanoclusters, which consisted of iso-propanol solvent and ultraviolet-curable acrylic binder, was also demonstrated.

  10. Structural and X-Ray Photoelectron Spectroscopy Study of Al-Doped Zinc-Oxide Thin Films

    Directory of Open Access Journals (Sweden)

    Bong Ju Lee

    2015-01-01

    Full Text Available Al-doped zinc-oxide (AZO thin films were prepared by RF magnetron sputtering at different oxygen partial pressures and substrate temperatures. The charge-carrier concentrations in the films decreased from 1.69 × 1021 to 6.16 × 1017 cm−3 with increased gas flow rate from 7 to 21 sccm. The X-ray diffraction (XRD patterns show that the (002/(103 peak-intensity ratio decreased as the gas flow rate increased, which was related to the increase of AZO thin film disorder. X-ray photoelectron spectra (XPS of the O1s were decomposed into metal oxide component (peak A and the adsorbed molecular oxygen on thin films (peak B. The area ratio of XPS peaks (A/B was clearly related to the stoichiometry of AZO films; that is, the higher value of A/B showed the higher stoichiometric properties.

  11. Study on the enhanced and stable field emission behavior of a novel electrosprayed Al-doped ZnO bilayer film

    KAUST Repository

    Mahmood, Khalid

    2014-01-01

    A novel electrosprayed bilayer film composed of an over-layer (L 2) of aluminium-doped ZnO (AZO) nanoflakes (NF-AZO) and a under-layer (L1) of AZO nanocrystallites structure (NC-AZO) named BL:NF/NC-AZO is studied as an excellent field-emitter. The XRD pattern demonstrated that the doped bilayer film has preferential growth along the c-axis with hexagonal wurtzite structure and the (0 0 2) peak shifted toward the larger angle side after doping. The lowest turn-on field of ∼2.8 V μm-1, highest emission current density of 1.95 mA cm-2 is obtained for BL:NF/NC-AZO under the field of 6.8 V μm-1 and as well as the highest field enhancement factor (β) is estimated to be 4370 ± 3, compared to pure ZnO bilayer film (BL:NF/NC-ZnO) and also better than NC-AZO film and possesses the excellent long term stability of emission current. The PL intensity of doped ZnO bilayer film is very much stronger than pure ZnO bilayer structure. The superior field emission properties are attributed to the better morphologies, Al-doping and better crystallinity of bilayer AZO films. © 2014 The Royal Society of Chemistry.

  12. Micro/Nano hierarchical peony-like Al doped ZnO superhydrophobic film: The guiding effect of (100) preferred seed layer

    Science.gov (United States)

    Li, Yang; Wang, Jingfeng; Kong, Yi; Zhou, Jia; Wu, Jinzhu; Wang, Gang; Bi, Hai; Wu, Xiaohong; Qin, Wei; Li, Qingkun

    2016-01-01

    In this communication, we present a versatile and controllable strategy for formation of superhydrophobic micro/nano hierarchical Al doped ZnO (AZO) films with a water contact angle (CA) of 170 ± 4°. This strategy involves a two-step layer-by-layer process employing an atomic layer deposition (ALD) technique followed by a hydrothermal method, and the resulting novel AZO surface layer consists of (100) dominant nano-rice-like AZO seed layer (the water CA of 110 ± 4°) covered with micro-peony-like AZO top. The growth mechanisms and superhydrophobic properties of the hierarchical AZO layer are discussed. It is believed that the present route holds promise for future success in the design and development of practical superhydrophobic materials.

  13. Mechanisms of lighting enhancement of Al nanoclusters-embedded Al-doped ZnO film in GaN-based light-emitting diodes

    International Nuclear Information System (INIS)

    Aluminum (Al)-doped ZnO (AZO) films with embedded Al nanoclusters were proposed and utilized to enhance the light output power and maximum operation current of GaN-based light-emitting diodes (LEDs). The AZO films were sputtered using ZnO and Al targets in a magnetron cosputtering system. With Al dc power of 7 W and ZnO 100 W ac power, the electron concentration of 4.1x1020 cm-3, electron mobility of 16.2 cm2/V s, and resistivity of 7.2x10-4 Ω cm were obtained for the deposited AZO film annealed at 600 deg. C for 1 min in a N2 ambient. As verified by a high resolution transmission electron microscopy, the deposited AZO films with embedded Al nanoclusters were clearly observed. A 35% increase in light output power of the GaN-based LEDs with Al nanoclusters-embedded AZO films was realized compared with the conventional LEDs operated at 500 mA. It was verified experimentally that the various characteristics of GaN-based LEDs including the antireflection, light scattering, current spreading, and the light extraction efficiency in light emission could be significantly enhanced with the use of Al nanoclusters-embedded AZO films.

  14. Reactive sputter deposition of Al doped TiOx thin films using titanium targets with aluminium inserts

    International Nuclear Information System (INIS)

    Highlights: •Ti(Al)Ox thin films with varying Al fractions and increasing discharge current were deposited. •The reactive sputtering behaviour of Ti targets with Al inserts was studied. •XPS and EDX were used to check the stoichiometry of the films. •Optical transmittance measurements were performed to determine the band gap. -- Abstract: Al doped TiOx thin films were deposited using Ti targets with Al inserts. Both the effect of the number of aluminium inserts and the discharge current on the discharge voltage, on the aluminium content in the thin films, and on the reactive sputtering behaviour was investigated. The aluminium content in the film was measured using X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX). X-ray diffraction (XRD) revealed that the as-deposited thin films were amorphous, independent of the aluminium content or the discharge current. The XPS results indicated that the oxide films were substoichiometric. The optical band gap of the Ti(Al)Ox thin films was investigated as a function of the aluminium concentration and the discharge current. The addition of aluminium results in a significant increase of the band gap at low discharge currents, while no significant influence on the band gap was found at higher currents

  15. High-Hall-Mobility Al-Doped ZnO Films Having Textured Polycrystalline Structure with a Well-Defined (0001) Orientation.

    Science.gov (United States)

    Nomoto, Junichi; Makino, Hisao; Yamamoto, Tetsuya

    2016-12-01

    Five hundred-nanometer-thick ZnO-based textured polycrystalline films consisting of 490-nm-thick Al-doped ZnO (AZO) films deposited on 10-nm-thick Ga-doped ZnO (GZO) films exhibited a high Hall mobility (μ H) of 50.1 cm(2)/Vs with a carrier concentration (N) of 2.55 × 10(20) cm(-3). Firstly, the GZO films were prepared on glass substrates by ion plating with dc arc discharge, and the AZO films were then deposited on the GZO films by direct current magnetron sputtering (DC-MS). The GZO interface layers with a preferential c-axis orientation play a critical role in producing AZO films with texture development of a well-defined (0001) orientation, whereas 500-nm-thick AZO films deposited by only DC-MS showed a mixture of the c-plane and the other plane orientation, to exhibit a μ H of 38.7 cm(2)/Vs with an N of 2.22 × 10(20) cm(-3). PMID:27365000

  16. Optical measurements and mapping in Ga- and Al-doped ZnO and Sn-doped In{sub 2}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Look, D.C. [Semiconductor Research Center, Wright State University, Dayton, OH, 45435 (United States); Wyle Laboratories, Inc., 2601 Mission Point Boulevard, Suite 300, Dayton, OH, 45431 (United States); Air Force Research Laboratory Sensors Directorate, Wright-Patterson Air Force Base, OH, 45433 (United States); Leedy, K.D. [Air Force Research Laboratory Sensors Directorate, Wright-Patterson Air Force Base, OH, 45433 (United States)

    2015-07-15

    Hall-effect/conductivity measurements in TCO materials such as Ga-doped ZnO (GZO), Al-doped ZnO (AZO), and Sn-doped In{sub 2}O{sub 3} (ITO) determine Hall mobility μ{sub H} and sheet carrier concentration n{sub s} directly by measurements of current, voltage, and magnetic field. If thickness d is known, then n{sub s} can be converted into volume concentration n = n{sub s}/d. Optical measurements, on the other hand, determine analogous quantities μ{sub opt} and n{sub opt} indirectly, usually by invoking the Drude model of the dielectric constant. Here we compare μ{sub opt} and n{sub opt} obtained by Drude analysis of reflection, transmission, and spectroscopic-ellipsometry (SE) measurements, with μ{sub H} and n. Although reasonably good agreement between Hall effect and optical parameters can be obtained with all of these techniques, SE is especially attractive for non-destructive, high-density mapping of μ and n. Moreover, we can use degenerate scattering theory to convert maps of μ and n into maps of donor and acceptor concentration. This new mapping methodology is applied to GZO and ITO. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Improved photovoltaic performance of inverted polymer solar cells through a sol-gel processed Al-doped ZnO electron extraction layer.

    Science.gov (United States)

    Kim, Jun Young; Cho, Eunae; Kim, Jaehoon; Shin, Hyeonwoo; Roh, Jeongkyun; Thambidurai, Mariyappan; Kang, Chan-mo; Song, Hyung-Jun; Kim, SeongMin; Kim, Hyeok; Lee, Changhee

    2015-09-21

    We demonstrate that nanocrystalline Al-doped zinc oxide (n-AZO) thin film used as an electron-extraction layer can significantly enhance the performance of inverted polymer solar cells based on the bulk heterojunction of poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl] (PCDTBT) and [6,6]-phenyl C(71)-butyric acid methyl ester (PC(70)BM). A synergistic study with both simulation and experiment on n-AZO was carried out to offer a rational guidance for the efficiency improvement. As a result, An n-AZO film with an average grain size of 13 to 22 nm was prepared by a sol-gel spin-coating method, and a minimum resistivity of 2.1 × 10(-3) Ω·cm was obtained for an Al-doping concentration of 5.83 at.%. When an n-AZO film with a 5.83 at.% Al concentration was inserted between the ITO electrode and the active layer (PCDTBT:PC(70)BM), the power conversion efficiency increased from 3.7 to 5.6%. PMID:26406762

  18. Effect of Al and N Doping on Structural and Optical Properties of Sol-Gel Derived ZnO Thin Films

    International Nuclear Information System (INIS)

    In this work, the preparation of ZnO, N-doped ZnO (NZO), Al-doped ZnO (AZO) and Al, N-doped ZnO (ANZO) thin films by the sol-gel spin-coating method is reported. The structural properties and surface morphologies of films were characterized by X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM). The optical properties of the films were interpreted from their transmission spectra using UV-VIS spectrophotometer. The XRD and SEM results disclosed that the crystallization quality and grain size of as-prepared films were highly influenced by N and Al doping. UV-VIS spectrophotometer results indicated that Al and N additives could significantly enhance the optical transparency and induce the blue-shift in optical bandgap of ZnO films. (author)

  19. Band alignment at the interface between Ni-doped Cr2O3 and Al-doped ZnO: implications for transparent p-n junctions

    Science.gov (United States)

    Arca, Elisabetta; McInerney, Michael A.; Shvets, Igor V.

    2016-06-01

    The realization of transparent electronic and optoelectronic devices requires the use of transparent p-n junctions. In this context, understanding the band alignment at the interface between the p- and n-components represents a fundamental step towards the realization of high performance devices. In this work, the band alignment at the interface between Al-doped ZnO (AZO) and Ni-doped Cr2O3 has been analysed. The formation and evolution of the core levels as the interface progressively forms have been followed by means of x-ray Photoelectron Spectroscopy, x-ray diffraction and x-ray reflectivity. A type two (staggered) band alignment was identified, with the valence band offset and conduction band offset found to be 2.6 eV and 2.5 eV, respectively. The electrical behaviour will be discussed in terms of the position of the bands, the presence of band bending and the expected built-in potential and how these can be engineered in order to achieve the maximum performance for this hetero-structure.

  20. Band alignment at the interface between Ni-doped Cr2O3 and Al-doped ZnO: implications for transparent p-n junctions.

    Science.gov (United States)

    Arca, Elisabetta; McInerney, Michael A; Shvets, Igor V

    2016-06-01

    The realization of transparent electronic and optoelectronic devices requires the use of transparent p-n junctions. In this context, understanding the band alignment at the interface between the p- and n-components represents a fundamental step towards the realization of high performance devices. In this work, the band alignment at the interface between Al-doped ZnO (AZO) and Ni-doped Cr2O3 has been analysed. The formation and evolution of the core levels as the interface progressively forms have been followed by means of x-ray Photoelectron Spectroscopy, x-ray diffraction and x-ray reflectivity. A type two (staggered) band alignment was identified, with the valence band offset and conduction band offset found to be 2.6 eV and 2.5 eV, respectively. The electrical behaviour will be discussed in terms of the position of the bands, the presence of band bending and the expected built-in potential and how these can be engineered in order to achieve the maximum performance for this hetero-structure. PMID:26952763

  1. Significant improvement in performances of LiNi0.5Mn1.5O4 through surface modification with high ordered Al-doped ZnO electro-conductive layer

    International Nuclear Information System (INIS)

    Graphical abstract: Al-doped ZnO (AZO)-coated LiNi0.5Mn1.5O4 (LNMO) was prepared by sol–gel method. AZO-coated LNMO electrode shows excellent rate capability and a remarkable improvement in the cyclic performance at a high rate at elevated temperature. - Highlights: • Al-doped ZnO (AZO)-coated LiNi0.5Mn1.5O4 (LNMO) was prepared by a traditional sol–gel method. • Al-doped ZnO (AZO) layer grown on the surface of LNMO is high ordered. • At a high rate of 10 C, the discharge capacity of the AZO-coated LNMO electrode can reach 114 mAh g−1. • Al-doped ZnO (AZO) modification improved cyclic performance of LNMO at high temperatures. - Abstract: Al-doped ZnO (AZO)-coated LiNi0.5Mn1.5O4 (LNMO) was prepared by sol–gel method. Transmission electron microscopy (TEM) analysis indicates that AZO layer grown on the surface of LNMO is high ordered. The results of electrochemical performance measurements reveal that the AZO-coated LNMO electrode displays the best rate capability compared with the bare LNMO and ZnO-coated LNMO, even at a high rate of 10 C. The discharge capacity of the AZO-coated LNMO electrode can still reach 114.3 mAh g−1, about 89% of its discharge capacity at 0.1 C. Moreover, AZO-coated LNMO electrode shows a remarkable improvement in the cyclic performance at a high rate at elevated temperature due to the protective effect of AZO coating layer. The electrode delivers a capacity of 120.3 mAh g−1 with the capacity retention of 95% at 5 C in 50 cycles at 50 °C. The analysis of electrochemical impedance spectra (EIS) indicates that AZO-coated LNMO possesses the lowest charge transfer resistance compared to the bare LNMO and ZnO-coated LNMO, which may be responsible for improved rate capability

  2. Significant improvement in performances of LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} through surface modification with high ordered Al-doped ZnO electro-conductive layer

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Hongdan; Xia, Bingbo [College of Physics, Optoelectronics and Energy & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Key Laboratory of Lithium Ion Battery Materials of Jiangsu Province, Institute of Chemical Power Sources, Soochow University, Suzhou 215006 (China); Liu, Weiwei [Changzhou Institute of Energy Storage Materials & Devices, Changzhou 213000 (China); Fang, Guoqing; Wu, Jingjing; Wang, Haibo; Zhang, Ruixue [College of Physics, Optoelectronics and Energy & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Key Laboratory of Lithium Ion Battery Materials of Jiangsu Province, Institute of Chemical Power Sources, Soochow University, Suzhou 215006 (China); Kaneko, Shingo [Key Laboratory of Lithium Ion Battery Materials of Jiangsu Province, Institute of Chemical Power Sources, Soochow University, Suzhou 215006 (China); Zheng, Junwei [College of Physics, Optoelectronics and Energy & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Key Laboratory of Lithium Ion Battery Materials of Jiangsu Province, Institute of Chemical Power Sources, Soochow University, Suzhou 215006 (China); Wang, Hongyu [Changzhou Institute of Energy Storage Materials & Devices, Changzhou 213000 (China); Li, Decheng, E-mail: lidecheng@suda.edu.cn [College of Physics, Optoelectronics and Energy & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Key Laboratory of Lithium Ion Battery Materials of Jiangsu Province, Institute of Chemical Power Sources, Soochow University, Suzhou 215006 (China)

    2015-03-15

    Graphical abstract: Al-doped ZnO (AZO)-coated LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} (LNMO) was prepared by sol–gel method. AZO-coated LNMO electrode shows excellent rate capability and a remarkable improvement in the cyclic performance at a high rate at elevated temperature. - Highlights: • Al-doped ZnO (AZO)-coated LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} (LNMO) was prepared by a traditional sol–gel method. • Al-doped ZnO (AZO) layer grown on the surface of LNMO is high ordered. • At a high rate of 10 C, the discharge capacity of the AZO-coated LNMO electrode can reach 114 mAh g{sup −1}. • Al-doped ZnO (AZO) modification improved cyclic performance of LNMO at high temperatures. - Abstract: Al-doped ZnO (AZO)-coated LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} (LNMO) was prepared by sol–gel method. Transmission electron microscopy (TEM) analysis indicates that AZO layer grown on the surface of LNMO is high ordered. The results of electrochemical performance measurements reveal that the AZO-coated LNMO electrode displays the best rate capability compared with the bare LNMO and ZnO-coated LNMO, even at a high rate of 10 C. The discharge capacity of the AZO-coated LNMO electrode can still reach 114.3 mAh g{sup −1}, about 89% of its discharge capacity at 0.1 C. Moreover, AZO-coated LNMO electrode shows a remarkable improvement in the cyclic performance at a high rate at elevated temperature due to the protective effect of AZO coating layer. The electrode delivers a capacity of 120.3 mAh g{sup −1} with the capacity retention of 95% at 5 C in 50 cycles at 50 °C. The analysis of electrochemical impedance spectra (EIS) indicates that AZO-coated LNMO possesses the lowest charge transfer resistance compared to the bare LNMO and ZnO-coated LNMO, which may be responsible for improved rate capability.

  3. Tunneling into Al doped MgB{sub 2} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, Rudolf; Zaitsev, Alexander G.; Geerk, Jochen [Forschungszentrum Karlsruhe (Germany). Institut fuer Festkoerperphysik

    2009-07-01

    Superconducting thin films with composition Mg{sub 1-x}Al{sub x}B{sub 2} (0{<=}x< 0.6) were prepared in situ by thermal sublimation of Mg combined with B rf and Al dc magnetron sputtering. The critical temperature, T{sub c}, decreased linearly with a slope of -0.4 K per at% Al up to x{approx}0.4. For 0.4

  4. Effect of Al dopants on the structural, optical and gas sensing properties of spray-deposited ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Prajapati, C.S. [Department of Physics, Motilal Nehru National Institute of Technology, Allahabad 211 004 (India); Kushwaha, Ajay [Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai 400076 (India); Sahay, P.P., E-mail: dr_ppsahay@rediffmail.com [Department of Physics, Motilal Nehru National Institute of Technology, Allahabad 211 004 (India)

    2013-10-01

    Undoped and Al-doped ZnO thin films were deposited on glass substrates by the spray pyrolysis method. The structural, morphological and optical properties of these films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV–Vis spectroscopy, photoluminescence (PL) and photoconductivity (PC) measurements, respectively. XRD analyses confirm that the films are polycrystalline zinc oxide with the hexagonal wurtzite structure, and the crystallite size has been found to be in the range 20–40 nm. SEM and AFM analyses reveal that the films have continuous surface without visible holes or faulty zones, and the surface roughness decreases on Al doping. The Al-doped films have been found to be highly transparent (>85%) and show normal dispersion behavior in the wavelength range 450–700 nm. The doped films show only ultraviolet emission and are found to be highly photosensitive. Among all the films examined, at 300 °C the 1.0 at% Al-doped film shows the selective high response (98.2%) to 100 ppm acetone concentration over to methanol, ethanol, propan-2-ol, formaldehyde and hydrogen. - Highlights: • ZnO films possess hexagonal wurtzite structure with crystallite size: 20–40 nm. • On Al doping, the surface roughness decreases and optical transmission increases. • Al-doped films exhibit the normal dispersion behavior for (450–700 nm) wavelength. • All the films are photosensitive and the photocurrent enhances on Al doping. • 1 at% Al-doped films exhibit high sensitivity and selectivity to acetone at 300 °C.

  5. Stable and high-quality Al-doped ZnO films with ICP-assisted facing targets sputtering at low temperature

    International Nuclear Information System (INIS)

    FTS (facing targets sputtering) has been studied intensively for high-quality TCO films in low-temperature processes. In this study, we designed ICP-assisted FTS process for high-quality Al-doped ZnO film synthesis in a low temperature process. A one-turn ICP coil was installed a few cm above the upper target edge through which hydrogen was introduced and fully dissociated to the atomic radicals. The increase of ICP power caused heating and rarefaction of Ar gas and generated abundant hydrogen atoms and hydrogenated molecules. In FESEM analysis, the films synthesized with high ICP power showed high crystallinity. XPS was used to analyze the film structure. In O1s spectra, the low binding energy component located at ∼530.3 ± 0.4 eV corresponding to O2− ions on the wurtzite structure of the hexagonal Zn2+ ion array increased with the ICP power, indicating good crystal quality. With increasing ICP power fixing while fixing the RF power at the cathode, the resistivity was observed to decrease to 5 × 10−4 Ω-cm. For thermal reliability tests, films were stored in an air-based chamber at 200 °C. The films synthesized without ICP showed rapid degradation in the electrical properties, while the films synthesized with high ICP power showed good stabilities with little change in the electrical properties after 30 h of storage in an oven. By adding hydrogen, the carrier concentration of the films increased, while the mobility did not change much. From these results, it is expected that hydrogen was incorporated into the film as a stable n-dopant by using an auxiliary ICP plasma source. (papers)

  6. Investigation of Al doping concentration effect on the structural and optical properties of the nanostructured CdO thin film

    Science.gov (United States)

    Gencer Imer, Arife

    2016-04-01

    Nanostructured aluminium (Al) doped cadmium oxide (CdO) films with highly electrical conductivity and optical transparency have been deposited for the first time on soda-lime glass substrates preheated at 250 °C by ultrasonic spray coating technique. The aluminium dopant content in the CdO film was changed from 0 to 5 at%. The influencing of Al doping on the structural, morphological, electrical and optical properties of the CdO nanostructured films has been investigated. Atomic force microscopy study showed the grain size of the films is an order of nanometers, and it decreases with increase in Al dopant content. All the films having cubic structure with a lattice parameter 4.69 Å were determined via X ray diffraction analysis. The optical band gap value of the films, obtained by optical absorption, was found to increase with Al doping. Electrical studies exhibited mobility, carrier concentration and resistivity of the film strongly dependent on the doping content. It has been evaluated that optical band gap, and grain size of the nanostructured CdO film could be modified by Al doping.

  7. Ga and Al doped zinc oxide thin films for transparent conducting oxide applications: Structure-property correlations

    Science.gov (United States)

    Temizer, Namik K.; Nori, Sudhakar; Narayan, Jagdish

    2014-01-01

    We report a detailed investigation on the structure-property correlations in Ga and Al codoped ZnO films on c-sapphire substrates where the thin film microstructure varies from nanocrystalline to single crystal. We have achieved highly epitaxial films with very high optical transmittance (close to 90%) and low resistivity (˜110 μΩ-cm) values. The films grown in an ambient oxygen partial pressure (PO2) of 5 × 10-2 Torr and at growth temperatures from room temperature to 600 °C show semiconducting behavior, whereas samples grown at a PO2 of 1 × 10-3 Torr show metallic nature. The most striking feature is the occurrence of resistivity minima at relatively high temperatures around 110 K in films deposited at high temperatures. The measured optical and transport properties were found to be a strong function of growth conditions implying that the drastic changes are brought about essentially by native point defects. The structure-property correlations reveal that point defects play an important role in modifying the structural, optical, electrical, and magnetic properties and such changes in physical properties are controlled predominantly by the defect content.

  8. Effect of Al and Mg Doping on Optical Properties of ZnO Thin Films Prepared by Spin Coating

    Directory of Open Access Journals (Sweden)

    G. T Yusuf

    2014-08-01

    Full Text Available This paper investigated the influence of aluminum and magnesium doping on the optical and electrical properties of zinc oxide (ZnO thin films for solar cell application. Zinc acetate dehydrates was used as starting material. Aluminum chloride and tin chloride were added to each solution to serve as dopants. X-ray diffractions were analyzed by X-ray diffraction (XRD which revealed crystalline and hexagonal wurtzite structure. All the films showed more than 80% transparency in the visible region. The optical band gap of undoped ZnO thin film was found to be 3.12ev while that of Al-doped and Mg-doped ZnO film was estimated to be 3.16eV and 3.26eV respectively. The resistivity of the films measured were 2.51×10–4 Ω cm for Al-doped, 2.53×10–4 Ω cm for mg-doped and 2.61×10-4 Ω cm for undoped ZnO respectively. The quality of the films deposited in this work is a promising window layer component of a solar cell. The variation in the band gap observed in this work could be explained by Burstein–Moss effect which was fully explained in the discussion section of this work.

  9. Physical properties and heterojunction device demonstration of aluminum-doped ZnO thin films synthesized at room ambient via sol–gel method

    International Nuclear Information System (INIS)

    Highlights: ► Undoped and Al doped ZnO (AZO) thin films were successfully prepared using sol–gel technique. ► Structural analysis has revealed that Al doping has a significant influence on preferential orientation. ► It has been observed that wrinkles forms on the surface of films when annealed with a fast heat ramp up rate. ► Optical analysis has revealed that that the band gap energy of ZnO thin film increases with increasing Al doping concentration. ► The lowest resistivity is observed for 1% Al ZnO thin film, which is 2.2 × 10−2 (Ω cm). - Abstract: ZnO and some of its ternary wide-bandgap alloys offer interesting opportunities for designing materials with tunable band gaps, strong piezoresistivity and controlled electrical conductance with high optical transparency. Synthesizing these materials on arbitrary substrates using low-cost and unconventional techniques can help in integrating semiconductors with different physical, electrical, and optical characteristics on a single substrate for heterogeneous integration of multifunctional devices. Here we report the successful synthesis of aluminum (Al) doped ZnO (AZO) thin films on soda-lime glass, silicon and fluorine doped tin oxide (FTO) pre-coated glass substrates by using sol–gel deposition method at ambient condition. X-ray diffraction (XRD) analysis revealed that varying degree of Al doping significantly impacts the crystal orientation, semiconductor bandgap and optical transparency of the film. Crystal structure of the film is also found to be strongly correlated to the characteristics of the substrate material. The impact of heating rate during post annealing process is studied and optimized in order to improve the surface morphology of the deposited films. Optical characterizations have revealed that bandgap energy of AZO films can be tuned between 3.30 eV and 4.1 eV as the Al concentration is varied from 1% to 20%. Similarly, electrical characteristics of these films indicate that 1

  10. Comparative study about Al-doped zinc oxide thin films deposited by Pulsed Electron Deposition and Radio Frequency Magnetron Sputtering as Transparent Conductive Oxide for Cu(In,Ga)Se2-based solar cells

    International Nuclear Information System (INIS)

    In this study, a comparison between Al-doped ZnO (AZO) as Transparent Conductive Oxide for Cu(In,Ga)Se2-based solar cells grown by Pulsed Electron Deposition (PED) and Radio Frequency Magnetron Sputtering (RFMS) was performed. PED yielded polycrystalline [002] mono-oriented thin films with low electrical resistivity and high optical transparency with heater temperatures ranging from room temperature (RT) to 250 °C. The electrical resistivity of these films can be tuned by varying the heater temperature, reaching a minimum value of 3.5 × 10−4 Ωcm at 150 °C and an average transmittance over 90% in the visible range. An AZO film grown at RT was deposited by PED on an actual Cu(In,Ga)Se2-based solar cell, resulting to an efficiency value of 15.2% on the best device. This result clearly shows that PED is a suitable technique for growing ZnO-based thin films for devices/applications where low deposition temperature is required. On the other hand, an optimized AZO thin film front contact for thin film solar cells was studied and fabricated via RFMS. The parameters of this technique were tweaked to obtain highly conductive and transparent AZO thin films. The lowest resistivity value of 3.7 × 10−4 Ωcm and an average transmittance of 86% in the 400-1100 nm wavelength range was obtained with a heater temperature of 250 °C. A thick sputtered AZO film was deposited at RT onto an identical cell used for PED-grown AZO, reaching the highest conversion efficiency value of 14.7%. In both cases, neither antireflection coatings nor pure ZnO layer was used. - Highlights: • Pulsed Electron Deposition (PED) lets high quality films grow at low temperature. • Al:ZnO (AZO) thin films grown by PED present high optical and electrical quality. • AZO electrical resistivity can be tuned from 10−4 to 10−2 Ωcm in proper condition. • Cu(In,Ga)Se2-based simplified solar cells achieved efficiency of 15.2% for PED-grown AZO

  11. Comparative study about Al-doped zinc oxide thin films deposited by Pulsed Electron Deposition and Radio Frequency Magnetron Sputtering as Transparent Conductive Oxide for Cu(In,Ga)Se{sub 2}-based solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Pattini, F., E-mail: pattini@imem.cnr.it [IMEM-CNR, Institute of Materials for Electronics and Magnetism, Parco Area delle Scienze 37/A, 43124 Parma (Italy); Annoni, F.; Bissoli, F.; Bronzoni, M. [IMEM-CNR, Institute of Materials for Electronics and Magnetism, Parco Area delle Scienze 37/A, 43124 Parma (Italy); Garcia, J.P. [Delft University of Technology, Faculty of Applied Sciences, Delft Product and Process Design Institute, Julianalaan 67, 2628 BC Delft (Netherlands); Gilioli, E.; Rampino, S. [IMEM-CNR, Institute of Materials for Electronics and Magnetism, Parco Area delle Scienze 37/A, 43124 Parma (Italy)

    2015-05-01

    In this study, a comparison between Al-doped ZnO (AZO) as Transparent Conductive Oxide for Cu(In,Ga)Se{sub 2}-based solar cells grown by Pulsed Electron Deposition (PED) and Radio Frequency Magnetron Sputtering (RFMS) was performed. PED yielded polycrystalline [002] mono-oriented thin films with low electrical resistivity and high optical transparency with heater temperatures ranging from room temperature (RT) to 250 °C. The electrical resistivity of these films can be tuned by varying the heater temperature, reaching a minimum value of 3.5 × 10{sup −4} Ωcm at 150 °C and an average transmittance over 90% in the visible range. An AZO film grown at RT was deposited by PED on an actual Cu(In,Ga)Se{sub 2}-based solar cell, resulting to an efficiency value of 15.2% on the best device. This result clearly shows that PED is a suitable technique for growing ZnO-based thin films for devices/applications where low deposition temperature is required. On the other hand, an optimized AZO thin film front contact for thin film solar cells was studied and fabricated via RFMS. The parameters of this technique were tweaked to obtain highly conductive and transparent AZO thin films. The lowest resistivity value of 3.7 × 10{sup −4} Ωcm and an average transmittance of 86% in the 400-1100 nm wavelength range was obtained with a heater temperature of 250 °C. A thick sputtered AZO film was deposited at RT onto an identical cell used for PED-grown AZO, reaching the highest conversion efficiency value of 14.7%. In both cases, neither antireflection coatings nor pure ZnO layer was used. - Highlights: • Pulsed Electron Deposition (PED) lets high quality films grow at low temperature. • Al:ZnO (AZO) thin films grown by PED present high optical and electrical quality. • AZO electrical resistivity can be tuned from 10{sup −4} to 10{sup −2} Ωcm in proper condition. • Cu(In,Ga)Se{sub 2}-based simplified solar cells achieved efficiency of 15.2% for PED-grown AZO.

  12. Residual and intentional n-type doping of ZnO thin films grown by metal-organic vapor phase epitaxy on sapphire and ZnO substrates

    Science.gov (United States)

    Brochen, Stéphane; Lafossas, Matthieu; Robin, Ivan-Christophe; Ferret, Pierre; Gemain, Frédérique; Pernot, Julien; Feuillet, Guy

    2014-03-01

    ZnO epilayers usually exhibit high n-type residual doping which is one of the reasons behind the difficulties to dope this material p-type. In this work, we aimed at determining the nature of the involved impurities and their potential role as dopant in ZnO thin films grown by metalorganic vapor phase epitaxy (MOVPE) on sapphire and ZnO substrates. In both cases, secondary ion mass spectroscopy (SIMS) measurements give evidence for a strong diffusion of impurities from the substrate to the epilayer, especially for silicon and aluminum. In the case of samples grown on sapphire substrates, aluminum follows Fick's diffusion law on a wide growth temperature range (800-1000°C). Thus, the saturation solubility and the diffusion coefficient of aluminum in ZnO single crystals have been determined. Furthermore, the comparison between SIMS impurity and effective dopant concentrations determined by capacitance-voltage measurements highlights, on one hand a substitutional mechanism for aluminum diffusion, and on the other hand that silicon acts as a donor in ZnO and not as an amphoteric impurity. In addition, photoluminescence spectra exhibit excitonic recombinations at the same energy for aluminum and silicon, indicating that silicon behaves as an hydrogenic donor in ZnO. Based on these experimental observations, ZnO thin films with a controlled n-type doping in the 1016-1019cm-3 range have been carried out. These results show that MOVPE growth is fully compatible with the achievement of highly Al-doped n-type thin films, but also with the growth of materials with low residual doping, which is a crucial parameter to address ZnO p-type doping issues.

  13. Double-beam pulsed laser deposition for the growth of Al-incorporated ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Moreno, L. [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, Circuito Exterior S/N, Ciudad Universitaria, AP 70-186, C.P. 04510 México D.F., México (Mexico); Sánchez-Aké, C., E-mail: citlali.sanchez@ccadet.unam.mx [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, Circuito Exterior S/N, Ciudad Universitaria, AP 70-186, C.P. 04510 México D.F., México (Mexico); Bizarro, M. [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apartado Postal 70-186, C.P. 04510 México D.F., México (Mexico)

    2014-05-01

    Pulsed laser deposition in a delayed-double beam configuration is used to incorporate in situ Al in ZnO thin films. In this configuration, two synchronized pulsed-laser beams are employed to ablate independently a ZnO and an Al target. We investigated the effects of relative time delay of plasma plumes on the composition of the films with the aim of evaluating the performance of this technique to produce doped materials. Relative delay between plumes was found to control the incorporation of Al in the film in the range from 14% to 30%. However, to produce low impurity concentration of Al-doped ZnO (with Al incorporation less than 2%) the fluence used to produce the plasmas has more influence over the film composition than the relative plume delay. The minimum incorporation of Al corresponded to a relative delay of 0 μs, due to the interaction between plumes during their expansion.

  14. Microstructure and optical properties of nanocrystalline ZnO and ZnO:(Li or Al) thin films

    International Nuclear Information System (INIS)

    Zinc oxide thin films (ZnO, ZnO:Li, ZnO:Al) were deposited on glass substrates by a sol-gel technique. Zinc acetate, lithium acetate, and aluminum chloride were used as metal ion sources in the precursor solutions. XRD analysis revealed that Li doped and undoped ZnO films formed single phase zincite structure in contrast to Al:ZnO films which did not fully crystallize at the annealing temperature of 550 deg. C. Crystallized films had a grain size under 50 nm and showed c-axis grain orientation. All films had a very smooth surface with RMS surface roughness values between 0.23 and 0.35 nm. Surface roughness and optical band tail values increased by Al doping. Compared to undoped ZnO films, Li doping slightly increased the optical band gap of the films

  15. Enhanced light extraction of GaN-based light-emitting diodes with periodic textured SiO2 on Al-doped ZnO transparent conductive layer

    Science.gov (United States)

    Yu, Zhao; Bingfeng, Fan; Yiting, Chen; Yi, Zhuo; Zhoujun, Pang; Zhen, Liu; Gang, Wang

    2016-07-01

    We report an effective enhancement in light extraction of GaN-based light-emitting diodes (LEDs) with an Al-doped ZnO (AZO) transparent conductive layer by incorporating a top regular textured SiO2 layer. The 2 inch transparent through-pore anodic aluminum oxide (AAO) membrane was fabricated and used as the etching mask. The periodic pore with a pitch of about 410 nm was successfully transferred to the surface of the SiO2 layer without any etching damages to the AZO layer and the electrodes. The light output power was enhanced by 19% at 20 mA and 56% at 100 mA compared to that of the planar LEDs without a patterned surface. This approach offers a technique to fabricate a low-cost and large-area regular pattern on the LED chip for achieving enhanced light extraction without an obvious increase of the forward voltage. ).

  16. Improved efficiency of aluminum doping in ZnO thin films grown by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Park, Hui Kyung; Heo, Jaeyeong, E-mail: jheo@jnu.ac.kr

    2014-08-01

    The improved efficiency of aluminum doping in ZnO (AZO) thin films grown by atomic layer deposition was demonstrated by controlling the number of surface reaction sites for trimethylalumium (TMA). Prolonged purge time (120 s) for deionized water used as an oxidant decreased the number of hydroxyl groups on the surface via dehydration reaction, resulting in the reduced chemisorption of TMA. The enhanced doping efficiency by sparse distribution of Al dopants was demonstrated by the increased carrier concentration from ~4 × 10²⁰ to ~6 × 10²⁰ cm⁻³ for the same Al doping cycle ratio. A comparison was made among the AZO films formed by using the control and modified recipes, focusing on their electrical, structural, and optical properties.

  17. Al and Fe co-doped transparent conducting ZnO thin film for mediator-less biosensing application

    Directory of Open Access Journals (Sweden)

    Shibu Saha

    2011-12-01

    Full Text Available Highly c-axis oriented Al and Fe co-doped ZnO (ZAF thin film is prepared by pulsed laser deposition. Fe introduces redox centre along with shallow donor level while Al doping enhances conductivity of ZnO, thus removing the requirement of both mediator and bottom conducting layer in bioelectrode. Model enzyme (glucose oxidase, was immobilized on surface of ZAF matrix. Cyclic voltammetry and photometric assay show that prepared bio-electrode is sensitive to glucose concentration with enhanced response of 0.18 μAmM-1cm-2 and low Km ∼ 2.01 mM. The results illustrate that ZAF is an attractive matrix for realization of miniaturized mediator-less solid state biosensor.

  18. Structural, electrical and optical characteristics of Al-doped zinc oxide thin films deposited by reactive magnetron sputtering

    International Nuclear Information System (INIS)

    ZnO:Al (AZO) thin films on glass were deposited by DC reactive magnetron sputtering at approximately 300°C substrate temperature. Structural, electrical and optical properties were investigated as a function of oxygen flow. XRD data shows that AZO thin films are polycrystalline with pronounced c-axis orientation and the grain size increasing with the oxygen flow. The lowest achieved resistivity within the deposited set of samples was 7.6·10−4 Ωcm The transmittance of AZO films was above 80 % at 550 run with the optical band gap between 3.4 and 3.8 eV

  19. An Al-doped ZnO electrode grown by highly efficient cylindrical rotating magnetron sputtering for low cost organic photovoltaics

    International Nuclear Information System (INIS)

    We report the characteristics of Al-doped zinc oxide (AZO) films prepared by a highly efficient cylindrical rotating magnetron sputtering (CRMS) system for use as a transparent conducting electrode in cost-efficient bulk hetero-junction organic solar cells (OSCs). Using a rotating cylindrical type cathode with an AZO target, whose usage was above 80%, we were able to obtain a low cost and indium free AZO electrode with a low sheet resistance of ∼4.59 Ω/sq, a high transparency of 85% in the visible wavelength region and a work function of 4.9 eV at a substrate temperature of 230 0C. Moreover, the neutral poly(3,4-ethylenedioxythiophene) : poly(styrenesulfonate) based OSC fabricated on the CRMS-grown AZO electrode at 230 0C showed an open circuit voltage of 0.5 V, a short circuit current of 8.94 mA cm-2, a fill factor of 45% and power conversion efficiency of 2.01%, indicating that CRMS is a promising cost-efficient AZO deposition technique for low cost OSCs.

  20. Influence of low sputtering pressure on structural, electrical and optical properties of Al-doped zinc oxide thin films

    Science.gov (United States)

    Zhang, Zengguang; Tang, Yang; Chen, Jingyun; Chen, Jie

    2016-08-01

    Aluminum-doped zinc oxide thin films were deposited without intentional heating by radio-frequency magnetron sputtering. The sputtering pressure varied from 0.02 Pa to 0.32 Pa while the deposition power was kept at 240 W for all depositions. The structural properties of as-deposited films were analyzed by X-ray diffraction and scanning electron microscopy, indicating that the deposited films have a strong preferred c-axis (002) orientation perpendicular to the substrate regardless of sputtering pressure. The minimum resistivity of 6.4×10-4 Ω cm is obtained at 0.05 Pa, which is mainly influenced by the hall mobility, rather than carrier concentration. The highest transmittance could be ~80% on average in the visible range under various working pressures, and the largest bandgap achieved is about 3.82 eV. The ultraviolet emission peaks in photoluminescence spectra are centered at about 360 nm. A new mechanism is proposed to explain the dependence of the electrical and optical properties on structural evolution of deposited films.

  1. Synthesis and characterization of ZnO thin films

    Science.gov (United States)

    Anilkumar T., S.; Girija M., L.; Venkatesh, J.

    2016-05-01

    Zinc oxide (ZnO) Thin films were deposited on glass substrate using Spin coating method. Zinc acetate dehydrate, Carbinol and Mono-ethanolamine were used as the precursor, solvent and stabilizer respectively to prepare ZnO Thin-films. The molar ratio of Monoethanolamine to Zinc acetate was maintained as approximately 1. The thickness of the films was determined by Interference technique. The optical properties of the films were studied by UV Vis-Spectrophotometer. From transmittance and absorbance curve, the energy band gap of ZnO is found out. Electrical Conductivity measurements of ZnO are carried out by two probe method and Activation energy for the electrical conductivity of ZnO are found out. The crystal structure and orientation of the films were analyzed by XRD. The XRD patterns show that the ZnO films are polycrystalline with wurtzite hexagonal structure.

  2. Microstructure and blueshift in optical band gap of nanocrystalline Al{sub x}Zn{sub 1−x}O thin films

    Energy Technology Data Exchange (ETDEWEB)

    Majeed Khan, M.A., E-mail: majeed_phys@rediffmail.com [King Abdullah Institute for Nanotechnology, King Saud University, Riyadh 11451 (Saudi Arabia); Kumar, Sushil [Materials ScienceLaboratory, Department of Physics, Chaudhary Devi Lal University, Sirsa 125055 (India); Naziruddin Khan, M.; Ahamed, Maqusood [King Abdullah Institute for Nanotechnology, King Saud University, Riyadh 11451 (Saudi Arabia); Al Dwayyan, A.S. [King Abdullah Institute for Nanotechnology, King Saud University, Riyadh 11451 (Saudi Arabia); Physics and Astronomy Department, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia)

    2014-11-15

    In this paper, we report the structural and optical properties of Al doped ZnO (AZO) thin films grown on glass substrates using the sol–gel process. To understand the effect of Al doping on the structural and optical response of ZnO nanoparticles thin films, the prepared samples have been characterized using X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), photoluminescence (PL), UV–vis absorption and Raman spectroscopy. X-ray diffraction results show that Al doped ZnO nanoparticles have hexagonal phase similar to ZnO nanoparticles. TEM images as well as XRD data exhibit the estimated size of nanoparticles to be in the range 35–45 nm. The optical band gap has been determined from optical absorption spectra. The band gap varied from 3.27 eV for undoped ZnO film to 3.87 eV for AZO film having 3 atwt% Al. The blue shift in energy band gap mainly related to carrier concentration induced by Al-donor doping, and to the degree of crystalline order. Photoluminescence study further confirms the blue shift in UV emission when Al doping concentration is increased, as a consequence of extension in band gap. - Highlights: • Undoped and Al doped ZnO nanoparticles has been synthesized by the sol–gel method. • Undoped and Al doped ZnO films have a (0 0 2) peak, indicating a hexagonal wurtzite structure. • The stacking faults induced by Al-doped provide another path for electron transfer. • Influence of Al doping on the physical properties of ZnO nanoparticles was investigated. • The quality and crystallinity of Al-doped ZnO films were investigated by varying the Al compositions.

  3. Atomic layer deposition of Al-doped ZnO films using ozone as the oxygen source: A comparison of two methods to deliver aluminum

    International Nuclear Information System (INIS)

    Aluminum-doped ZnO films were prepared by atomic layer deposition at 250 deg. C using diethylzinc (DEZ), trimethylaluminum (TMA), and ozone as the precursors. Two deposition methods were compared to assess their impact on the composition, structural, electrical, and optical properties as a function of Al concentration. The first method controlled the Al concentration by changing the relative number of Al to Zn deposition cycles; a process reported in the literature where water was used as the oxygen source. The second method involved coinjection of the DEZ and TMA during each cycle where the partial pressures of the precursors control the aluminum concentration. Depth profiles of the film composition using Auger electron spectroscopy confirmed a layered microstructure for the films prepared by the first method, whereas the second method led to a homogeneous distribution of the aluminum throughout the ZnO film. Beneath the surface layer the carbon concentrations for all of the films were below the detection limit. Comparison of their electrical and optical properties established that films deposited by coinjection of the precursors were superior.

  4. Different magnetothermoelectric behavior in Al- and Ga-doped ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Han; Fang, Liang, E-mail: lfang@cqu.edu.cn; Tian, Dexiang; Wu, Fang; Li, Wanjun

    2014-03-05

    Highlights: • The effect of magnetic field on the thermoelectric property was investigated. • The tendencies of the |S| for AZO and GZO varying with magnetic field were observed. • Magnetic field can decrease the |S| of AZO but increase that of GZO. -- Abstract: This essay mainly focuses on the influence of magnetic filed on thermoelectric properties of Al-doped ZnO (AZO) and Ga-doped ZnO (GZO) thin films. The Seebeck coefficients (S) of AZO and GZO films show opposite behavior as a function of the magnetic field intensity (B), which should be attributed to the effect of magnetic field on the effective electron number and potential barrier at grain boundary. For GZO film, with higher electron number, the influence of magnetic field on the effective electron number is the dominant factor, while more potential barriers at grain boundaries exist in AZO film due to the Al–O bond length with a higher mismatch to Zn–O bond length than the Ga–O bond length, so the effect of magnetic field on the potential barriers at grain boundaries dominates in AZO film.

  5. Low-frequency dielectric properties of intrinsic and Al-doped rutile TiO2 thin films grown by the atomic layer deposition technique

    Science.gov (United States)

    Kassmi, M.; Pointet, J.; Gonon, P.; Bsiesy, A.; Vallée, C.; Jomni, F.

    2016-06-01

    Dielectric spectroscopy is carried out for intrinsic and aluminum-doped TiO2 rutile films which are deposited on RuO2 by the atomic layer deposition technique. Capacitance and conductance are measured in the 0.1 Hz-100 kHz range, for ac electric fields up to 1 MVrms/cm. Intrinsic films have a much lower dielectric constant than rutile crystals. This is ascribed to the presence of oxygen vacancies which depress polarizability. When Al is substituted for Ti, the dielectric constant further decreases. By considering Al-induced modification of polarizability, a theoretical relationship between the dielectric constant and the Al concentration is proposed. Al doping drastically decreases the loss in the very low frequency part of the spectrum. However, Al doping has almost no effect on the loss at high frequencies. The effect of Al doping on loss is discussed through models of hopping transport implying intrinsic oxygen vacancies and Al related centers. When increasing the ac electric field in the MVrms/cm range, strong voltage non-linearities are evidenced in undoped films. The conductance increases exponentially with the ac field and the capacitance displays negative values (inductive behavior). Hopping barrier lowering is proposed to explain high-field effects. Finally, it is shown that Al doping strongly improves the high-field dielectric behavior.

  6. Epsilon-Near-Zero Al-Doped ZnO for Ultrafast Switching at Telecom Wavelengths: Outpacing the Traditional Amplitude-Bandwidth Trade-Off

    CERN Document Server

    Kinsey, N; Kim, J; Ferrera, M; Shalaev, V M; Boltasseva, A

    2015-01-01

    Transparent conducting oxides have recently gained great attention as CMOS-compatible materials for applications in nanophotonics due to their low optical loss, metal-like behavior, versatile/tailorable optical properties, and established fabrication procedures. In particular, aluminum doped zinc oxide (AZO) is very attractive because its dielectric permittivity can be engineered over a broad range in the near infrared and infrared. However, despite all these beneficial features, the slow (> 100 ps) electron-hole recombination time typical of these compounds still represents a fundamental limitation impeding ultrafast optical modulation. Here we report the first epsilon-near-zero AZO thin films which simultaneously exhibit ultra-fast carrier dynamics (excitation and recombination time below 1 ps) and an outstanding reflectance modulation up to 40% for very low pump fluence levels (< 4 mJ/cm2) at the telecom wavelength of 1.3 {\\mu}m. The unique properties of the demonstrated AZO thin films are the result of...

  7. Highly transparent and conductive Sn/F and Al co-doped ZnO thin films prepared by sol–gel method

    International Nuclear Information System (INIS)

    Highlights: • F/Sn and Al co-doped ZnO thin films were synthesized by sol–gel method. • The co-doped nanocrystals exhibit good crystal quality. • The origin of the photoluminescence emissions was discussed. • The films showed high transmittance and low resistivity. -- Abstract: Al doped ZnO, Al–Sn co-doped ZnO and Al–F co-doped ZnO nanocrystals were successfully synthesized onto glass substrates by the sol–gel method. The structure and morphology of the films are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). The results indicated that all the films were polycrystalline with a hexagonal wurtzite structure and exhibited a c-axis preferred orientation. The electrical and optical properties were also investigated by 4-point probe device and Uv–vis spectroscopy, room temperature photoluminescence (PL) and Raman spectrum (Raman), respectively. The PL and Raman results suggested that the co-doped films with a very low defect concentration and exhibit a better crystallinity than AZO thin films. The XPS study confirmed the incorporation of Al, Sn and F ions in the ZnO lattice

  8. Influence of Ag thickness of aluminum-doped ZnO/Ag/aluminum-doped ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Hung-Wei, E-mail: hwwu@mail.ksu.edu.tw [Department of Computer and Communication, Kun Shan University, No. 949, Dawan Rd., Yongkang Dist., Tainan City 710, Taiwan (China); Yang, Ru-Yuan [Graduate Institute of Materials Engineering, National Pingtung University of Science and Technology, 1, Shuefu Rd., Neipu, Pingtung City 912, Taiwan (China); Hsiung, Chin-Min; Chu, Chien-Hsun [Department of Mechanical Engineering, National Pingtung University of Science and Technology, 1, Shuefu Rd., Neipu, Pingtung City 912, Taiwan (China)

    2012-10-01

    Highly conducting aluminum-doped ZnO (30 nm)/Ag (5-15 nm)/aluminum-doped ZnO (30 nm) multilayer thin films were deposited on glass substrate by rf magnetron sputtering (for top/bottom aluminum-doped ZnO films) and e-beam evaporation (for Ag film). The transmittance is more than 70% for wavelengths above 400 nm with the Ag layer thickness of 10 nm. The resistivity is 3.71 Multiplication-Sign 10{sup -4} {Omega}-cm, which can be decreased to 3.8 Multiplication-Sign 10{sup -5} {Omega}-cm with the increase of the Ag layer thickness to 15 nm. The Haacke figure of merit has been calculated for the films with the best value being 8 Multiplication-Sign 10{sup -3} {Omega}{sup -1}. It was shown that the multilayer thin films have potential for applications in optoelectronics. - Highlights: Black-Right-Pointing-Pointer High-quality Al-doped ZnO (AZO)/Ag/AZO Transparent Conducting Oxide films. Black-Right-Pointing-Pointer AZO films (30 nm) made by RF sputtering; E-beam evaporation for Ag film (5-15 nm). Black-Right-Pointing-Pointer Influence of Ag thickness on optical and electrical properties were analyzed. Black-Right-Pointing-Pointer High quality multilayer film with optimal intermediate Ag layer thickness of 10 nm. Black-Right-Pointing-Pointer 3.71 Multiplication-Sign 10{sup -4} {Omega}-cm resistivity, 91.89% transmittance at 470 nm obtained and reproducible.

  9. Optical and electrical characterization of Al doped zinc oxide nanoporous films prepared via sol-gel method

    Energy Technology Data Exchange (ETDEWEB)

    Nasr, Babak; Dasgupta, Subho; Kruk, Robert; Hahn, Horst [Karlsruhe Institute of Technology (KIT) GmbH, Institute of Nanotechnology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)

    2010-07-01

    Highly transparent and conducting ZnO films doped with different Al concentration prepared via sol-gel method. In this study one of the most important deposition parameters, heat ramping at pre-heat-treatment step, was investigated to grow high porous thin films in high surface area applications. It was found that high porosity is obtainable by fast heat ramping of the gel films. In addition the optical and electrical properties of Al doped ZnO films as a function of carrier concentration was studied using UV-Vis, FTIR spectroscopy, and four points measurement. The films were all transparent in visible range and had a sharp absorption around 380 nm. A blue shifts of the absorption edge respect to undoped ZnO has been observed as a function of the carrier concentration up to 2 at.% Al doping due to Burstein-Moss effect. Strongly resonance absorption at plasma frequency in near infra red region led to calculation of carrier concentration. These investigations were complemented by photoconductivity measurement to understand the impact of surface states in electronic structure of the films. Among different doped films with atomic ratio of 0.5 to 4 with increments of 0.5 the systems with 1.5at.% to 2at.% show the lowest resistivity and widest optical band gap.

  10. Fundamental understanding of the growth, doping and characterization of aligned ZnO nanowires

    Science.gov (United States)

    Shen, Gang

    Zinc oxide (ZnO) is a II-VI semiconductor whose wide direct bandgap (3.37 eV) and large exciton binding energy (60 meV) make it compelling for optoelectronic devices such as light emitting diodes, lasers, photodetectors, solar cells, and mechanical energy harvesting devices. One dimensional structures of ZnO (nanowires) have become significant due to their unique physical properties arising from quantum confinement, and they are ideal for studying transport mechanisms in one-dimensional systems. In this doctoral research work, ZnO nanowire (NW) arrays were synthesized on sapphire substrates through carbo-thermal reduction of ZnO powders, and the effects of growth parameters on the properties of ZnO NW arrays were studied by scanning and transmission electron microscopy, X-ray diffraction, photoluminescence and Raman spectroscopy. Based on the phonon mode selection rules in wurtzite ZnO, confocal Raman spectroscopy was used to assess the alignment of ZnO NWs in an array, thereby complementing X-ray diffraction. Al doped ZnO NW arrays were achieved by mixing Al powder into the ZnO and graphite source mixture, and the presence of Al was confirmed by Energy-dispersive X-ray spectroscopy. The incorporation of Al had the effects of lowering the electrical resistivity, slightly deteriorating crystal quality and suppressing defect related green emission. Two models of ZnO NW growth were developed by establishing the relationship between NW length and diameter for undoped and Al doped ZnO NWs separately. The growth of undoped ZnO NWs followed the diffusion-induced model which was characterized by thin wires being longer than thick wires, while the growth of Al doped ZnO was controlled by Gibbs-Thomson effect which was characterized by thin wires being shorter than thin wires. Local electrode atom probe analysis of ZnO NWs was carried out to study the crystal stoichiometry and Al incorporation. Undoped ZnO NWs were found to be high purity with no detectable impurities

  11. ZnO Thin Film Electronics for More than Displays

    Science.gov (United States)

    Ramirez, Jose Israel

    Zinc oxide thin film transistors (TFTs) are investigated in this work for large-area electronic applications outside of display technology. A constant pressure, constant flow, showerhead, plasma-enhanced atomic layer deposition (PEALD) process has been developed to fabricate high mobility TFTs and circuits on rigid and flexible substrates at 200 °C. ZnO films and resulting devices prepared by PEALD and pulsed laser deposition (PLD) have been compared. Both PEALD and PLD ZnO films result in densely packed, polycrystalline ZnO thin films that were used to make high performance devices. PEALD ZnO TFTs deposited at 300 °C have a field-effect mobility of ˜ 40 cm2/V-s (and > 20 cm2/V-S deposited at 200 °C). PLD ZnO TFTs, annealed at 400 °C, have a field-effect mobility of > 60 cm2/V-s (and up to 100 cm2/V-s). Devices, prepared by either technique, show high gamma-ray radiation tolerance of up to 100 Mrad(SiO2) with only a small radiation-induced threshold voltage shift (VT ˜ -1.5 V). Electrical biasing during irradiation showed no enhanced radiation-induced effects. The study of the radiation effects as a function of material stack thicknesses revealed the majority of the radiation-induced charge collection happens at the semiconductor-passivation interface. A simple sheet-charge model at that interface can describe the radiation-induced charge in ZnO TFTs. By taking advantage of the substrate-agnostic process provided by PEALD, due to its low-temperature and excellent conformal coatings, ZnO electronics were monolithically integrated with thin-film complex oxides. Application-based examples where ZnO electronics provide added functionality to complex oxide-based devices are presented. In particular, the integration of arrayed lead zirconate titanate (Pb(Zr, Ti)O3 or PZT) thin films with ZnO electronics for microelectromechanical systems (MEMs) and deformable mirrors is demonstrated. ZnO switches can provide voltage to PZT capacitors with fast charging and slow

  12. A high power ZnO thin film piezoelectric generator

    Science.gov (United States)

    Qin, Weiwei; Li, Tao; Li, Yutong; Qiu, Junwen; Ma, Xianjun; Chen, Xiaoqiang; Hu, Xuefeng; Zhang, Wei

    2016-02-01

    A highly efficient and large area piezoelectric ZnO thin film nanogenerator (NG) was fabricated. The ZnO thin film was deposited onto a Si substrate by pulsed laser ablation at a substrate temperature of 500 °C. The deposited ZnO film exhibited a preferred c-axis orientation and a high piezoelectric value of 49.7 pm/V characterized using Piezoelectric Force Microscopy (PFM). Thin films of ZnO were patterned into rectangular power sources with dimensions of 0.5 × 0.5 cm2 with metallic top and bottom electrodes constructed via conventional semiconductor lithographic patterning processes. The NG units were subjected to periodic bending/unbending motions produced by mechanical impingement at a fixed frequency of 100 Hz at a pressure of 0.4 kg/cm2. The output electrical voltage, current density, and power density generated by one ZnO NG were recorded. Values of ∼95 mV, 35 μA cm-2 and 5.1 mW cm-2 were recorded. The level of power density is typical to that produced by a PZT NG on a flexible substrate. Higher energy NG sources can be easily created by adding more power units either in parallel or in series. The thin film ZnO NG technique is highly adaptable with current semiconductor processes, and as such, is easily integrated with signal collecting circuits that are compatible with mass production. A typical application would be using the power harvested from irregular human foot motions to either to operate blue LEDs directly or to drive a sensor network node in mille-power level without any external electric source and circuits.

  13. Influence of process parameters on band gap of AI-doped ZnO film

    Institute of Scientific and Technical Information of China (English)

    Diqiu HUANG; Xiangbin ZENG; Yajuan ZHENG; Xiaojin WANG; Yanyan YANG

    2013-01-01

    This paper presents the influence of process parameters, such as argon (Ar) flow rate, sputtering power and substrate temperature on the band gap of Al-doped ZnO film, Al-doped ZnO thin films were fabricated by radio frequency (RF) magnetron sputtering technology and deposited on polyimide and glass substrates. Under different Ar flow rates varied from 30 to 70 sccm, the band gap of thin films were changed from 3.56 to 3.67 eV. As sputtering power ranged from 125 to 200 W, the band gap was varied from 3.28 to 3.82 eV; the band gap was between 3.41 and 3.88 eV as substrate temperature increases from 150℃ to 300℃. Furthermore, the correlation between carrier concentration and band gap was investigated by HALL. These results demonstrate that the band gap of the Al-doped ZnO thin film can be adjusted by changing the Ar flow rate, sputtering power and substrate temperature, which can improve the performance of semiconductor devices related to Al-doped ZnO thin film.

  14. Compositional and physico-optical characterization of 0-5% Al-doped zinc oxide films prepared by chemical spray pyrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Romero, R; Lopez-Ibanez, R; Ramos-Barrado, J R; Martin, F; Leinen, D [Laboratorio de Materiales y Superficie (Unidad Asociada al CSIC), Dpto. Fisica Aplicada I and Dpto. IngenierIa Quimica, Universidad de Malaga, E-29071 Malaga (Spain); Dalchiele, E A, E-mail: dietmar@uma.e [Instituto de Fisica, Facultad de IngenierIa, Universidad de la Republica, Herrera y Reissig 565, C.C. 30, 11000 Montevideo (Uruguay)

    2010-03-10

    Highly transparent polycrystalline Al-doped ZnO thin films were deposited in open atmosphere by chemical spray pyrolysis on fused silica and glass substrates at 623 K. The influence of Al doping, 0 to 5%, was studied. XPS results revealed a linear relationship between Al content in the precursor solutions and Al content in the films. XPS depth profiling showed that any carbon contamination is restricted to the uppermost surface of the films. Optical transmission measurements revealed an increasing number of dispersion centres as well as a band gap shift to higher values with increasing Al content in the films. At fixed Al concentration, the comparison of the absorption coefficient for increasing film thickness showed that the films are very homogeneous, not changing their materials properties such as absorption coefficient and band gap.

  15. Impact of Al doping on microstructure and optical characteristics of tetrapod-like zinc oxide whiskers

    International Nuclear Information System (INIS)

    Al-doped tetrapod-like zinc oxide whiskers with different Al dopant concentration (0.3∼1.0 mol%) were prepared by solid state reaction method using T-ZnOw and AlCl3 powder as raw materials. X-ray diffraction and SEM microscopy were applied to characterize the structure and surface morphology of the T-ZnOw. The shift of diffraction peaks of ZnO towards high angle indicated the increase of Al-doping concentration. The ZnO whiskers with 0.5 mol% Al doping concentration exhibit good photoluminescence properties with a large PL intensity ratio value (24) and a narrow FWHM value (15 nm). The improvement photoluminescence properties are attributed to the doping of Al element in the ZnO lattice. It is thought that the visible emission with the wavelength of 517 nm is attributed to the electronics transition from Al atoms to Zn vacancy level.

  16. Effects of doping concentration on properties of Mn-doped ZnO thin films

    Institute of Scientific and Technical Information of China (English)

    Gao Li; Zhang Jian-Min

    2009-01-01

    This paper reports that the radio frequency magnetron sputtering is used to fabricate ZnO and Mn-doped ZnO thin films on glass substrates at 500 ℃. The Mn-doped ZnO thin films present wurtzite structure of ZnO and have a smoother surface, better conductivity but no ferromagnetism. The x-ray photoelectron spectroscopy results show that the binding energy of Mn_(2p3/2) increases with increasing Mn content slightly, and the state of Mn in the Mn-doped ZnO thin films is divalent. The chemisorbed oxygen in the Mn-doped ZnO thin films increases with increasing Mn doping concentration. The photoluminescence spectra of ZnO and Mn-doped ZnO thin films have a similar ultraviolet emission. The yellow green emissions of 4 wt. % and 10 wt. % Mn-doped thin films are quenched, whereas the yellow green emission occurs because of abundant oxygen vacancies in the Mn-doped ZnO thin films after 20 wt. % Mn doping. Compared with pure ZnO thin film, the bandgap of the Mn-doped ZnO thin films increases with increasing Mn content.

  17. ZnO Thin Film Ga s Sensor for CO

    International Nuclear Information System (INIS)

    ZnO thin films were deposited onto corning glass substrates by rf magnetron sputtering system using ZnO targets. Films were deposited under rf power of 80 W at various deposition time. The distance between the target and substrate was held at 45 cm. A mixed Ar and O2 gas was introduced into the chamber at 4x10-2 Torr. The structure of the deposited ZnO films was investigated by Scanning electron miscroscopy. The gas sensing properties were evaluated at various operation temperatures by measuring the changes of resistance of the sensor in air and in CO gas respectively using the gas sensing characterization system. The grain size was increased as the film thickness was increased during deposition. The sensor with 233 nm film thickness exhibited the highest sensitivity for CO gas.

  18. Comparative study on the properties of ZnO nanowires and nanocrystalline thin films

    OpenAIRE

    Broitman, Esteban; Bojorge, C; Elhordoy, F; Kent, V.; Zanini Gadioli, G; Marotti, R.; Canepa, H; Dalchiele, E. A.

    2012-01-01

    The microstructural, morphological, optical and water-adsorption properties of nanocrystalline ZnO thin films and ZnO nanowires were studied and compared. The ZnO thin films were obtained by a sol–gel process, while the ZnO nanowires were electrochemically grown onto a ZnO sol–gel spin-coated seed layer. Thin films and nanowire samples were deposited onto crystalline quartz substrates covered by an Au electrode, able to be used in a quartz crystal microbalance. X-ray diffraction measurements ...

  19. Preparation of highly textured surface ZnO thin films

    International Nuclear Information System (INIS)

    In order to investigate the influence of the deposition technique upon the surface morphology of ZnO thin films we have employed two methods, which are the spray pyrolysis and magnetron sputtering. The surface morphology of ZnO thin films is a crucial parameter for controlling the reflection losses reduction when the coating is used as a transparent front layer in solar cells. The morphology of the surface was characterized by optical microscopy and profilometry. The results indicate that spray technique enables the elaboration of films with a highly rough surface, however sputtering technique yields to smoother films. This difference originates from the different deposition processes involved in both techniques. A vertical r.m.s. (root mean square) roughness in the order of 200 nm was measured in sprayed film; however only 40 nm r.m.s. vertical roughness is reported in sputtered one. The surface morphology in sprayed films causes the incident light diffraction; consequently the reflection is reduced up to zero. Therefore we show that ZnO thin films deposited with spray method is a potential candidate for use as a front transparent layer in solar cells

  20. Optical characterization of ZnO thin films deposited by RF magnetron sputtering method

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    This study investigated the process parameter effects on the structural and optical properties of ZnO thin film using radio frequency (RF) magnetron sputtering on amorphous glass substrates. The process parameters included RF power and working pressure. Results show that RF power was increased to promote the crystalline quality and decrease ZnO thin film defects. However, when the working pressure was increased to 3 Pa the ZnO thin film crystalline quality became worse. At a 200 W RF power and 1 Pa working pressure, the ZnO thin film with an optical band gap energy of 3.225 eV was obtained.

  1. Single-Crystal Mesoporous ZnO Thin Films Composed of Nanowalls

    KAUST Repository

    Wang, Xudong

    2009-02-05

    This paper presents a controlled, large scale fabrication of mesoporous ZnO thin films. The entire ZnO mesoporous film is one piece of a single crystal, while high porosity made of nanowalls is present. The growth mechanism was proposed in comparison with the growth of ZnO nanowires. The ZnO mesoporous film was successfully applied as a gas sensor. The fabrication and growth analysis of the mesoporous ZnO thin film gi ve general guidance for the controlled growth of nanostructures. It also pro vides a unique structure with a superhigh surface-to-volume ratio for surface-related applications. © 2009 American Chemical Society.

  2. Two different mechanisms on UV emission enhancement in Ag-doped ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Linhua, E-mail: congyu3256@tom.com [School of Physics and Optoelectronic Engineering, Nanjing University of Information Science and Technology, Nanjing 210044 (China); Optics and Photonic Technology Laboratory, Nanjing University of Information Science and Technology, Nanjing 210044 (China); Zheng, Gaige; Zhao, Lilong; Pei, Shixin [School of Physics and Optoelectronic Engineering, Nanjing University of Information Science and Technology, Nanjing 210044 (China); Optics and Photonic Technology Laboratory, Nanjing University of Information Science and Technology, Nanjing 210044 (China)

    2015-02-15

    Ag-doped ZnO thin films were prepared by a sol–gel method. The structural, morphological and optical properties of the samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV–vis and photoluminescence spectra. The results show that the Ag in the ZnO thin films annealed at 500 °C for 1 h substitutes for Zn and exists in the form of Ag{sup +} ion (Ag{sub Zn}) while the Ag in the ZnO thin films without a post-annealing mainly exists in the form of simple substance (Ag{sup 0}). The incorporation of Ag indeed can improve the ultraviolet emission of ZnO thin films and suppress the visible emissions at the same time. However, the mechanisms on the ultraviolet emission enhancement in the annealed and unannealed Ag-doped ZnO thin films are very different. As for the post-annealed Ag-doped ZnO thin films, the UV emission enhancement maybe mainly results from more electron–hole pairs (excitons) due to Ag-doping while for the unannealed Ag-doped ZnO thin films; the UV emission enhancement is attributed to the resonant coupling between exciton emission in ZnO and localized surface plasmon in Ag nanoparticles. - Highlights: • Ag-doped ZnO thin films have been prepared by the sol–gel method. • Ag-doping can enhance ultraviolet emission of ZnO thin films and depress the visible emissions at the same time. • There are two different mechanisms on UV emission enhancement in Ag-doped ZnO thin films. • The UV emission enhancement from the resonant coupling between excitonic emissions and localized surface plasmon in Ag nanoparticle is very attractive.

  3. Atomic layer deposition of ZnO thin films and dot structures

    International Nuclear Information System (INIS)

    Successful growth of thin films and quantum dots of ZnO by atomic layer deposition (ALD) is reported. Properties of ZnO films produced by four different ALD-procedures and by oxidation of ALD-grown ZnS films are discussed. The use of thin ZnO films as buffer layers for GaN deposition is also shortly described. (author)

  4. ZnO thin films prepared by surfatron produced discharge

    Czech Academy of Sciences Publication Activity Database

    Olejníček, Jiří; Šmíd, Jiří; Čada, Martin; Kment, Š.; Churpita, Olexandr; Kšírová, Petra; Brunclíková, Michaela; Adámek, Petr; Kohout, Michal; Valvoda, V.; Chvostová, Dagmar; Zlámal, M.; Hubička, Zdeněk

    2014-01-01

    Roč. 230, Jul (2014), s. 119-124. ISSN 0920-5861 R&D Projects: GA TA ČR TA01011740; GA MŠk LH12045; GA ČR GAP108/12/1941; GA ČR(CZ) GAP205/11/0386 Grant ostatní: GACR(CZ) GP13-29241P Institutional support: RVO:68378271 Keywords : ZnO * surfatron * thin films * Langmuir probe * plasma density Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.893, year: 2014

  5. Influence of Al concentration and annealing temperature on structural, optical, and electrical properties of Al co-doped ZnO thin films

    International Nuclear Information System (INIS)

    Highlights: • RF magnetron sputtering technique seems to be very efficient method for fabrication of Al doped ZnO (AZO) films. • Long range single crystalline structure improves with annealing process. • Optical properties became much better after annealing process especially for the AZO films that include high Al concentration. • Much greater conductivity with increasing Al concentration and annealing process. • AZO films have potential applicability in spintronic devices. - Abstract: The pure ZnO and Al-doped ZnO (AZO) thin films (thickness: 200 nm) were prepared on both side polished silica (SiO2) substrates via RF magnetron sputtering at room temperature by using 2.5 inches high-purity ZnO (99.9%) and Al (99.9%) targets. The samples were annealed at 300 °C, 400 °C and 500 °C for 45 min in N2 ambient in quartz annealing furnace system, respectively. We investigated the effects of various Al concentrations and annealing treatment on the structural, electrical, and optical properties of films. The preferred crystallization was observed along c axis (single (0 0 2) diffraction peak) from substrate surface assigning the single crystalline Würtzite lattice for pure ZnO and AZO thin films. Although increasing Al concentration decreases the order of crystallization of as-grown films, annealing process increases the long range crystal order. The crystallite sizes vary between minimum 12.98 nm and maximum 20.79 nm for as-grown and annealed samples. The crystallite sizes decrease with increasing Al concentration but increase with increasing annealing temperature as general trend. The grain size and porosity of films change with annealing treatment. The smaller grains coalesce together to form larger grains for many films. However, a reverse behavior is seen for Al2.23ZnO and Al12.30ZnO samples. That is, Al concentration plays critical role as well as temperature on grain size. Low percent optical transmittance (T%) is observed due to higher Al concentration

  6. Influence of Al concentration and annealing temperature on structural, optical, and electrical properties of Al co-doped ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Gürbüz, Osman [Department of Physics, Yıldız Technical University, Davutpaşa, 34210 İstanbul (Turkey); Kurt, İsmail; Çalışkan, Serkan [Department of Physics, Fatih University, Büyükçekmece, 34500 İstanbul (Turkey); Güner, Sadık, E-mail: sguner@fatih.edu.tr [Department of Physics, Fatih University, Büyükçekmece, 34500 İstanbul (Turkey)

    2015-09-15

    Highlights: • RF magnetron sputtering technique seems to be very efficient method for fabrication of Al doped ZnO (AZO) films. • Long range single crystalline structure improves with annealing process. • Optical properties became much better after annealing process especially for the AZO films that include high Al concentration. • Much greater conductivity with increasing Al concentration and annealing process. • AZO films have potential applicability in spintronic devices. - Abstract: The pure ZnO and Al-doped ZnO (AZO) thin films (thickness: 200 nm) were prepared on both side polished silica (SiO{sub 2}) substrates via RF magnetron sputtering at room temperature by using 2.5 inches high-purity ZnO (99.9%) and Al (99.9%) targets. The samples were annealed at 300 °C, 400 °C and 500 °C for 45 min in N{sub 2} ambient in quartz annealing furnace system, respectively. We investigated the effects of various Al concentrations and annealing treatment on the structural, electrical, and optical properties of films. The preferred crystallization was observed along c axis (single (0 0 2) diffraction peak) from substrate surface assigning the single crystalline Würtzite lattice for pure ZnO and AZO thin films. Although increasing Al concentration decreases the order of crystallization of as-grown films, annealing process increases the long range crystal order. The crystallite sizes vary between minimum 12.98 nm and maximum 20.79 nm for as-grown and annealed samples. The crystallite sizes decrease with increasing Al concentration but increase with increasing annealing temperature as general trend. The grain size and porosity of films change with annealing treatment. The smaller grains coalesce together to form larger grains for many films. However, a reverse behavior is seen for Al{sub 2.23}ZnO and Al{sub 12.30}ZnO samples. That is, Al concentration plays critical role as well as temperature on grain size. Low percent optical transmittance (T%) is observed due to

  7. Effect of Mg doping in ZnO buffer layer on ZnO thin film devices for electronic applications

    Science.gov (United States)

    Giri, Pushpa; Chakrabarti, P.

    2016-05-01

    Zinc Oxide (ZnO) thin films have been grown on p-silicon (Si) substrate using magnesium doped ZnO (Mg: ZnO) buffer layer by radio-frequency (RF) sputtering method. In this paper, we have optimized the concentration of Mg (0-5 atomic percent (at. %)) ZnO buffer layer to examine its effect on ZnO thin film based devices for electronic and optoelectronic applications. The crystalline nature, morphology and topography of the surface of the thin film have been characterized. The optical as well as electrical properties of the active ZnO film can be tailored by varying the concentration of Mg in the buffer layer. The crystallite size in the active ZnO thin film was found to increase with the Mg concentration in the buffer layer in the range of 0-3 at. % and subsequently decrease with increasing Mg atom concentration in the ZnO. The same was verified by the surface morphology and topography studies carried out with scanning electron microscope (SEM) and atomic electron microscopy (AFM) respectively. The reflectance in the visible region was measured to be less than 80% and found to decrease with increase in Mg concentration from 0 to 3 at. % in the buffer region. The optical bandgap was initially found to increase from 3.02 eV to 3.74 eV by increasing the Mg content from 0 to 3 at. % but subsequently decreases and drops down to 3.43 eV for a concentration of 5 at. %. The study of an Au:Pd/ZnO Schottky diode reveals that for optimum doping of the buffer layer the device exhibits superior rectifying behavior. The barrier height, ideality factor, rectification ratio, reverse saturation current and series resistance of the Schottky diode were extracted from the measured current voltage (I-V) characteristics.

  8. ZnO thin films with (Li,Ni)-codoping

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Senthil; Rao, M.S. Ramachandra [Materials Science Research Centre, Indian Institute of Technology Madras, Chennai (India); Althammer, Matthias; Venkateshvaran, Deepak; Karrer-Mueller, Eva; Goennenwein, Sebastian T.B.; Opel, Matthias; Gross, Rudolf [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany)

    2011-07-01

    The wide bandgap II-VI semiconductor ZnO is controversially discussed with regard to both dilute magnetic doping and stable p-type conductivity. Following a recent report [APL 96, 232504 (2010)], we investigated (Li,Ni)-codoping to establish ferromagnetism together with p-type conduction. Using laser-MBE, we deposited thin films from stoichiometric targets with compositions Zn{sub 0.98-x}Li{sub x}Ni{sub 0.02}O (x=0, 0.02, 0.05, 0.09). High-resolution x-ray diffraction reveals excellent structural quality and nearly perfect in-plane orientation. Magnetization measurements show an ''S''-shaped behavior in M(H) at room temperature and a clear difference after field cooling or zero-field cooling in M(T) which is reminiscent of superparamagnetism. The saturation magnetic moment is around 0.7 {mu}{sub B} per Ni and, hence, very close to the bulk value of Ni metal (0.6 {mu}{sub B}). From thermopower measurements, we obtained negative Seebeck coefficients between -400 {mu} V/K and -900 {mu} V/K, with smaller absolute values corresponding to lower Li concentrations. In summary, we could not confirm p-type conductivity or ferromagnetism in (Li,Ni)-substituted ZnO thin films.

  9. Al-doped ZnO/Ag grid hybrid transparent conductive electrodes fabricated using a low-temperature process

    International Nuclear Information System (INIS)

    Highlights: • Al-doped ZnO/Ag transparent conductive electrode is fabricated at low temperature. • Performance of the hybrid transparent conductive electrode affected by the structure. • The performance enhancement mechanism is suggested. - Abstract: Al-doped ZnO (AZO)/Ag grid hybrid transparent conductive electrode (TCE) structures were fabricated at a low temperature by using electrohydrodynamic jet printing for the Ag grids and atomic layer deposition for the AZO layers. The structural investigations showed that the AZO/Ag grid hybrid structures consisted of Ag grid lines formed by Ag particles and the AZO layer covering the inter-spacing between the Ag grid lines. The Ag particles comprising the Ag grid lines were also capped by thin AZO layers, and the coverage of the AZO layers was increased with increasing the thickness of the AZO layer. Using the optimum thickness of AZO layer of 70 nm, the hybrid TCE structure showed an electrical resistivity of 5.45 × 10−5 Ω cm, an optical transmittance of 80.80%, and a figure of merit value of 1.41 × 10−2 Ω−1. The performance enhancement was suggested based on the microstructural investigations on the AZO/Ag grid hybrid structures

  10. Al-doped ZnO/Ag grid hybrid transparent conductive electrodes fabricated using a low-temperature process

    Energy Technology Data Exchange (ETDEWEB)

    An, Ha-Rim; Oh, Sung-Tag [Department of Materials Science and Engineering, Seoul National University of Science and Technology, Seoul 139-743 (Korea, Republic of); Kim, Chang Yeoul [Future Convergence Ceramic Division, Korea Institute Ceramic Engineering and Technology (KICET), Seoul 233-5 (Korea, Republic of); Baek, Seong-Ho [Energy Research Division, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 711-873 (Korea, Republic of); Park, Il-Kyu, E-mail: ikpark@ynu.ac.kr [Department of Electronic Engineering, Yeungnam University, Gyeongbuk 712-749 (Korea, Republic of); Ahn, Hyo-Jin, E-mail: hjahn@seoultech.ac.kr [Department of Materials Science and Engineering, Seoul National University of Science and Technology, Seoul 139-743 (Korea, Republic of)

    2014-12-05

    Highlights: • Al-doped ZnO/Ag transparent conductive electrode is fabricated at low temperature. • Performance of the hybrid transparent conductive electrode affected by the structure. • The performance enhancement mechanism is suggested. - Abstract: Al-doped ZnO (AZO)/Ag grid hybrid transparent conductive electrode (TCE) structures were fabricated at a low temperature by using electrohydrodynamic jet printing for the Ag grids and atomic layer deposition for the AZO layers. The structural investigations showed that the AZO/Ag grid hybrid structures consisted of Ag grid lines formed by Ag particles and the AZO layer covering the inter-spacing between the Ag grid lines. The Ag particles comprising the Ag grid lines were also capped by thin AZO layers, and the coverage of the AZO layers was increased with increasing the thickness of the AZO layer. Using the optimum thickness of AZO layer of 70 nm, the hybrid TCE structure showed an electrical resistivity of 5.45 × 10{sup −5} Ω cm, an optical transmittance of 80.80%, and a figure of merit value of 1.41 × 10{sup −2} Ω{sup −1}. The performance enhancement was suggested based on the microstructural investigations on the AZO/Ag grid hybrid structures.

  11. Analysis of Li-related defects in ZnO thin films influenced by annealing ambient

    Indian Academy of Sciences (India)

    Bing Wang; Lidan Tang

    2014-02-01

    Li-doped ZnO thin films were grown on quartz substrates by radio frequency magnetron sputtering and in situ annealing under O2 or Ar ambient. Li-related defects in ZnO films strongly depend on the annealing ambient. AFM and XRD indicated that ZnO films possessed a good crystallinity with -axis orientation, uniform thickness and dense surface. Electrical and optical properties demonstrated that, an amount of LiZn defect had existed in ZnO annealed under O2 ambient and an amount of Lii(o) defect had existed in ZnO annealed under Ar ambient. First-principle calculations were performed to calculate formation energies of Li-doped ZnO in order to explain the formation mechanism of Li-related defects in ZnO.

  12. Influence of annealing on polymeric precursor derived ZnO thin films on sapphire

    International Nuclear Information System (INIS)

    Zinc oxide (ZnO) thin films on c-sapphire substrates were synthesized by spin-coating aqueous polymeric precursors. The effects of annealing at 1000 °C on crystallinity, surface morphology, and optical properties of ZnO thin films, with varying thicknesses, were studied. Single-layered ZnO thin films are polycrystalline with wurtzite structure and preferentially oriented along the (002) plane. X-ray diffraction pattern also reveals the presence of spinel zinc aluminate (ZnAl2O4) peaks. ZnO films have highly faceted granular morphology. Multilayered ZnO films, annealed twice at 1000 °C, do not exhibit any ZnO peaks but only ZnAl2O4 peaks. Moreover, the surface morphology was smooth with ridges. These films do not exhibit the band gap or ultra-violet emission photoluminescence characteristics of ZnO. On annealing, there is an interfacial reaction between ZnO and sapphire resulting in ZnAl2O4. - Highlights: • Multilayer polymeric precursor derived ZnO film is annealed at 1000 °C on c-sapphire. • X-Ray diffraction (XRD) pattern of ZnO film annealed at 1000 °C shows ZnO peaks. • XRD pattern of ZnO films twice-annealed at 1000 °C shows only ZnAl2O4 peaks. • Optical characterization of the multilayered films does not show ZnAl2O4 peaks. • On annealing twice at 1000 °C, ZnO reacts with the c-sapphire to form ZnAl2O4

  13. Laser nanostructuring of ZnO thin films

    Science.gov (United States)

    Nedyalkov, N.; Koleva, M.; Nikov, R.; Atanasov, P.; Nakajima, Y.; Takami, A.; Shibata, A.; Terakawa, M.

    2016-06-01

    In this work, results on laser processing of thin zinc oxide films deposited on metal substrate are presented. ZnO films are obtained by classical nanosecond pulsed laser deposition method in oxygen atmosphere on tantalum substrate. The produced films are then processed by nanosecond laser pulses at wavelength of 355 nm. The laser processing parameters and the film thickness are varied and their influence on the fabricated structures is estimated. The film morphology after the laser treatment is found to depend strongly on the laser fluence as two regimes are defined. It is shown that at certain conditions (high fluence regime) the laser treatment of the film leads to formation of a discrete nanostructure, composed of spherical like nanoparticles with narrow size distribution. The dynamics of the melt film on the substrate and fast cooling are found to be the main mechanisms for fabrication of the observed structures. The demonstrated method is an alternative way for direct fabrication of ZnO nanostructures on metal which can be easy implemented in applications as resistive sensor devices, electroluminescent elements, solar cell technology.

  14. Optical and structural properties of Sr-doped ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Linhua, E-mail: congyu3256@tom.com [School of Physics and Optoelectronic Engineering, Nanjing University of Information Science and Technology, Nanjing 210044 (China); Optics and Photonic Technology Laboratory, Nanjing University of Information Science and Technology, Nanjing 210044 (China); Xiao, Shaorong; Zhang, Chengyi; Zheng, Gaige; Su, Jing; Zhao, Lilong; Wang, Junfeng [School of Physics and Optoelectronic Engineering, Nanjing University of Information Science and Technology, Nanjing 210044 (China); Optics and Photonic Technology Laboratory, Nanjing University of Information Science and Technology, Nanjing 210044 (China)

    2014-12-15

    ZnO thin film is a widely studied optoelectronic material at present. Doping is an important method to adjust its structural, optical, electrical and magnetic properties. A lot of doped ZnO thin films especially those doped with Al, Ga, Co have been extensively investigated. However, the Sr-doped ZnO thin films are still few reported up to now. In this work, the Sr-doped ZnO thin films have been deposited by sol–gel method. Their structural and optical properties have been analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–visible spectrophotometry and photoluminescence (PL), respectively. The results show that the appropriate Sr-doping levels can improve the crystalline quality and ultraviolet emission performance of ZnO thin films and suppress their visible emissions. This probably results from the decrease of point defects such as oxygen vacancy etc. due to the Sr-doping. What is more, it is also found that there exists a saturation value of Sr-doping concentration in ZnO thin films deposited using our prepared sol system, which is because the dopant Strontium chloride is slightly soluble in ethanol. - Graphical abstract: The figure shows the XRD patterns of the Sr-doped ZnO thin films with different doping levels. All the diffraction peaks correspond to the diffraction from wurtzite ZnO planes and no secondary phases are detected from the XRD patterns. Compared with the pure ZnO thin film, the intensity of the (002) peak located at ∼34.4° is enhanced and the FWHM is decreased when the Sr-doped level is below 7%. This means Sr-doping improves the crystalline quality of ZnO thin films to some extent. - Highlights: • Sr-doped ZnO thin films have been prepared by sol–gel method and deeply studied. • The crystalline quality of ZnO thin film is improved to some extent by Sr-doping. • All the films exhibit high transmittance in the visible range. • With an appropriate Sr-doping level, the visible emissions are suppressed and

  15. Defects Induced Room Temperature Ferromagnetism in ZnO Thin Films

    OpenAIRE

    Xiao Zhang; , Wei Zhang; Xinghua Zhang; Xuewen Xu; Fanbin Meng; Tang, C.C.

    2014-01-01

    Polycrystalline ZnO thin films are prepared by the co-sputtering method under different oxygen partial pressures. Films deposited in pure argon gas exhibit ferromagnetism, whereas other films deposited under different oxygen partial pressures are diamagnetism. XPS results show the presence of Zn interstitial and oxygen vacancy in all of samples. Further analysis indicates that Zn interstitial may play an important role in triggering magnetic order on the undoped ZnO thin films by inducing an ...

  16. Application of an Al-doped zinc oxide subcontact layer on vanadium-compensated 6H-SiC photoconductive switches

    Institute of Scientific and Technical Information of China (English)

    周天宇; 刘学超; 黄维; 代冲冲; 郑燕青; 施尔畏

    2015-01-01

    Al-doped ZnO thin film (AZO) is used as a subcontact layer in 6H–SiC photoconductive semiconductor switches (PCSSs) to reduce the on-state resistance and optimize the device structure. Our photoconductive test shows that the on-state resistance of lateral PCSS with an n+-AZO subcontact layer is 14.7%lower than that of PCSS without an n+-AZO subcontact layer. This occurs because a heavy-doped AZO thin film can improve Ohmic contact properties, reduce contact resistance, and alleviate Joule heating. Combined with the high transparance characteristic at 532 nm of AZO film, vertical structural PCSS devices are designed and their structural superiority is discussed. This paper provides a feasible route for fabricating high performance SiC PCSS by using conductive and transparent ZnO-based materials.

  17. Nanocrystalline ZnO thin film for photocatalytic purification of water

    International Nuclear Information System (INIS)

    ZnO thin film was prepared via evaporation of Zn metal on a glass sheet following by calcination (oxidation) process. The influences of calcination parameters such as temperature and time on the surface morphology and phase structure of ZnO films were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The analysis of XRD patterns indicated that the growth of ZnO nano-structure was controlled by calcination time and temperature. Optimum ZnO nano-fibers can be formed uniformly after 2 h of oxidation at 550 deg. C. Nanostructured ZnO catalyst exhibited a significantly greater superiority for the photodegradation of 2,4,6-Trichlorophenol (TCP) as a model pollutant in water over photolysis via irradiation with UV of 254 nm wavelength. The role of ZnO catalyst is discussed and the chemical composition of degradation products and intermediates are identified.

  18. Assembly of ordered ZnO porous thin films by cooperative assembly method using polystyrene spheres and ultrafine ZnO particles

    International Nuclear Information System (INIS)

    Ordered ZnO porous thin films were fabricated by cooperative assembly method using polystyrene sphere (PS) and ultrafine ZnO particles, in which ultrafine ZnO particles were directly assembled in the voids of PS while the template was being assembled by capillary forces. The influence of experimental parameters, such as evaporation temperature, ZnO concentration and the concentration ratio of PS/ZnO on morphology of the porous structure was mainly studied. The results showed that an ordered porous structure could be obtained by this method. X-ray diffraction (XRD) spectra indicated the porous ZnO thin film was wurtzite structure. The transmissivity decreased with the decrease of wavelength, but still kept above 80% beyond the wavelength of 550 nm. Optical band gap of the ZnO thin film was 3.13 eV

  19. Crystallinity Improvement of ZnO Thin Film on Different Buffer Layers Grown by MBE

    Directory of Open Access Journals (Sweden)

    Shao-Ying Ting

    2012-01-01

    Full Text Available The material and optical properties of ZnO thin film samples grown on different buffer layers on sapphire substrates through a two-step temperature variation growth by molecular beam epitaxy were investigated. The thin buffer layer between the ZnO layer and the sapphire substrate decreased the lattice mismatch to achieve higher quality ZnO thin film growth. A GaN buffer layer slightly increased the quality of the ZnO thin film, but the threading dislocations still stretched along the c-axis of the GaN layer. The use of MgO as the buffer layer decreased the surface roughness of the ZnO thin film by 58.8% due to the suppression of surface cracks through strain transfer of the sample. From deep level emission and rocking curve measurements it was found that the threading dislocations play a more important role than oxygen vacancies for high-quality ZnO thin film growth.

  20. Surface Engineering of ZnO Thin Film for High Efficiency Planar Perovskite Solar Cells

    OpenAIRE

    Zong-Liang Tseng; Chien-Hung Chiang; Chun-Guey Wu

    2015-01-01

    Sputtering made ZnO thin film was used as an electron-transport layer in a regular planar perovskite solar cell based on high quality CH3NH3PbI3 absorber prepared with a two-step spin-coating. An efficiency up to 15.9% under AM 1.5G irradiation is achieved for the cell based on ZnO film fabricated under Ar working gas. The atmosphere of the sputtering chamber can tune the surface electronic properties (band structure) of the resulting ZnO thin film and therefore the photovoltaic performance o...

  1. Recent advances in ZnO nanostructures and thin films for biosensor applications: Review

    International Nuclear Information System (INIS)

    Graphical abstract: ZnO nanostructures have shown binding of biomolecules in desired orientation with improved conformation and high biological activity, resulting in enhanced sensing characteristics. Furthermore, their compatibility with complementary metal oxide semiconductor technology for constructing integrated circuits makes them suitable candidate for future small integrated biosensor devices. This review highlights various approaches to synthesize ZnO nanostructures and thin films, and their applications in biosensor technology. Highlights: ► This review highlights various approaches to synthesize ZnO nanostructures and thin films. ► Article highlights the importance of ZnO nanostructures as biosensor matrix. ► Article highlights the advances in various biosensors based on ZnO nanostructures. ► Article describes the potential of ZnO based biosensor for new generation healthcare devices. - Abstract: Biosensors have shown great potential for health care and environmental monitoring. The performance of biosensors depends on their components, among which the matrix material, i.e., the layer between the recognition layer of biomolecule and transducer, plays a crucial role in defining the stability, sensitivity and shelf-life of a biosensor. Recently, zinc oxide (ZnO) nanostructures and thin films have attracted much interest as materials for biosensors due to their biocompatibility, chemical stability, high isoelectric point, electrochemical activity, high electron mobility, ease of synthesis by diverse methods and high surface-to-volume ratio. ZnO nanostructures have shown the binding of biomolecules in desired orientations with improved conformation and high biological activity, resulting in enhanced sensing characteristics. Furthermore, compatibility with complementary metal oxide semiconductor technology for constructing integrated circuits makes ZnO nanostructures suitable candidate for future small integrated biosensor devices. This review

  2. Use of chemically synthesized ZnO thin film as a liquefied petroleum gas sensor

    International Nuclear Information System (INIS)

    Liquefied petroleum gas (LPG) sensing properties of ZnO thin films consisting of sub-micron rods synthesized by chemical bath deposition (CBD) method are presented in depth. The scanning electron microscopy observation reveals that ZnO sub-micron rods are of hexagonal in phase grown perpendicular to the substrate surface. Due to large surface area, the ZnO thin films of sub-micron rods were sensitive to the explosive LPG, which was studied for different time depositions and for different operating temperatures. The maximum response of 28% at 673 K was recorded under the exposure of 10% of lower explosive level (LEL) of LPG. The ZnO thin films of sub-micron rods exhibited good sensitivity and rapid response-recovery characteristics towards LPG

  3. Properties of antimony doped ZnO thin films deposited by spray pyrolysis technique

    Energy Technology Data Exchange (ETDEWEB)

    Sadananda Kumar, N., E-mail: sadanthara@gmail.com; Bangera, Kasturi V.; Shivakumar, G. K. [National Institute of Technology Karnataka, Surathkal, Thin Films Laboratory, Department of Physics (India)

    2015-07-15

    Antimony (Sb) doped zinc oxide (ZnO) thin films were deposited on the glass substrate at 450°C using spray pyrolysis technique. Effect of Sb doping on surface morphology structural, optical and electrical properties were studied. X-ray diffraction (XRD) analysis showed that both the undoped and doped ZnO thin films are polycrystalline in nature with (101) preferred orientation. SEM analysis showed a change in surface morphology of Sb doped ZnO thin films. Doping results in a marked increase in conductivity without affecting the transmittance of the films. ZnO films prepared with 3 at % Sb shows the lowest resistivity of 0.185 Ohm cm with a Hall mobility of 54.05 cm{sup 2} V{sup –1} s{sup –1}, and a hole concentration of 6.25 × 10{sup 17} cm{sup –3}.

  4. Superhydrophobic Ag decorated ZnO nanostructured thin film as effective surface enhanced Raman scattering substrates

    Science.gov (United States)

    Jayram, Naidu Dhanpal; Sonia, S.; Poongodi, S.; Kumar, P. Suresh; Masuda, Yoshitake; Mangalaraj, D.; Ponpandian, N.; Viswanathan, C.

    2015-11-01

    The present work is an attempt to overcome the challenges in the fabrication of super hydrophobic silver decorated zinc oxide (ZnO) nanostructure thin films via thermal evaporation process. The ZnO nanowire thin films are prepared without any surface modification and show super hydrophobic nature with a contact angle of 163°. Silver is further deposited onto the ZnO nanowire to obtain nanoworm morphology. Silver decorated ZnO (Ag@ZnO) thin films are used as substrates for surface enhanced Raman spectroscopy (SERS) studies. The formation of randomly arranged nanowire and silver decorated nanoworm structure is confirmed using FESEM, HR-TEM and AFM analysis. Crystallinity and existence of Ag on ZnO are confirmed using XRD and XPS studies. A detailed growth mechanism is discussed for the formation of the nanowires from nanobeads based on various deposition times. The prepared SERS substrate reveals a reproducible enhancement of 3.082 × 107 M for Rhodamine 6G dye (R6G) for 10-10 molar concentration per liter. A higher order of SERS spectra is obtained for a contact angle of 155°. Thus the obtained thin films show the superhydrophobic nature with a highly enhanced Raman spectrum and act as SERS substrates. The present nanoworm morphology shows a new pathway for the construction of semiconductor thin films for plasmonic studies and challenges the orderly arranged ZnO nanorods, wires and other nano structure substrates used in SERS studies.

  5. Textured ZnO thin films by RF magnetron sputtering

    CERN Document Server

    Ginting, M; Kang, K H; Kim, S K; Yoon, K H; Park, I J; Song, J S

    1999-01-01

    Textured thin films ZnO has been successfully grown by rf magnetron sputtering method using a special technique of introducing a small amount of water and methanol on the deposition chamber. The grain size of the textured surface is highly dependent on the argon pressure during the deposition. The pressure in this experiment was varied from 50 mTorr down to 5 mTorr and the highest grain size of the film is obtained at 5 mTorr. The total transmittance of the films are more than 85% in the wavelength of 400 to 800 nm, and haze ratio of about 14% is obtained at 400 nm wavelength. Beside the textured surface, these films also have very low resistivity, which is lower than 1.4x10 sup - sup 3 OMEGA centre dot cm. X-ray analysis shows that the films with textured surface have four diffraction peaks on the direction of (110), (002), (101) and (112), while the non-textured films have only (110) and (002) peaks. Due to the excellent characteristics of this film, it will make the film very good TCO alternatives for the ...

  6. Improving light trapping and conversion efficiency of amorphous silicon solar cell by modified and randomly distributed ZnO nanorods

    International Nuclear Information System (INIS)

    Three-dimensional (3D) nanostructures in thin film solar cells have attracted significant attention due to their applications in enhancing light trapping. Enhanced light trapping can result in more effective absorption in solar cells, thus leading to higher short-circuit current density and conversion efficiency. We develop randomly distributed and modified ZnO nanorods, which are designed and fabricated by the following processes: the deposition of a ZnO seed layer on substrate with sputtering, the wet chemical etching of the seed layer to form isolated islands for nanorod growth, the chemical bath deposition of the ZnO nanorods, and the sputtering deposition of a thin Al-doped ZnO (ZnO:Al) layer to improve the ZnO/Si interface. Solar cells employing the modified ZnO nanorod substrate show a considerable increase in solar energy conversion efficiency. (condensed matter: structural, mechanical, and thermal properties)

  7. Cytotoxic evaluation of nanostructured zinc oxide (ZnO) thin films and leachates.

    Science.gov (United States)

    Petrochenko, Peter E; Zhang, Qin; Bayati, Reza; Skoog, Shelby A; Phillips, K Scott; Kumar, Girish; Narayan, Roger J; Goering, Peter L

    2014-09-01

    Nanostructured ZnO films have potential use as coatings on medical devices and food packaging due to their antimicrobial and UV-protection properties. However, their influence on mammalian cells during clinical use is not fully understood. This study investigated the potential cytotoxicity of ZnO thin films in RAW 264.7 macrophages. ZnO thin films (∼96nm thick with a 50nm grain) were deposited onto silicon wafers using pulsed laser deposition. Cells grown directly on ZnO thin film coatings exhibited less toxicity than cells exposed to extracts of the coatings. Cells on ZnO thin films exhibited a 43% and 68% decrease in cell viability using the MTT and 7-AAD/Annexin V flow cytometry assays, respectively, after a 24-h exposure as compared to controls. Undiluted 100% 24- and 48-h extracts decreased viability by 89%, increased cell death by LDH release to 76% 24h after treatment, and increased ROS after 5-24h of exposure. In contrast, no cytotoxicity or ROS were observed for 25% and 50% extracts, indicating a tolerable concentration. Roughly 24 and 34μg/m(2) Zn leached off the surfaces after 24 and 48h of incubation, respectively. ZnO coatings may produce gradual ion release which becomes toxic after a certain level and should be evaluated using both direct exposure and extraction methods. PMID:24878115

  8. Investigation of thin ZnO layers in view of laser desorption-ionization

    Science.gov (United States)

    Grechnikov, A. A.; Georgieva, V. B.; Alimpiev, S. S.; Borodkov, A. S.; Nikiforov, S. M.; Simanovsky, Ya O.; Dimova-Malinovska, D.; Angelov, O. I.

    2010-04-01

    Thin zinc oxide films (ZnO) were developed as a matrix-free platform for surface assisted laser desorption-ionization (SALDI) time-of-flight mass spectrometry. The ZnO films were deposited by RF magnetron sputtering of ZnO ceramic targets in Ar atmospheres on monocrystalline silicon. The generation under UV (355 nm) laser irradiation of positive ions of atenolol, reserpine and gramicidin S from the ZnO layers deposited was studied. All analytes tested were detected as protonated molecules with no or very structure-specific fragmentation. The mass spectra obtained showed low levels of chemical background noise. All ZnO films studied exhibited high stability and good reproducibility. The detection limits for test analytes are in the 10 femtomol range.

  9. Properties of ZnO thin films grown on Si substrates by photo-assisted MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Li Xiangping [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Qianjin Street 2699, Changchun 130012 (China)], E-mail: lxp2897871@126.com; Zhang Baolin [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Qianjin Street 2699, Changchun 130012 (China)], E-mail: zbl@jlu.edu.cn; Zhu Huichao [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Qianjin Street 2699, Changchun 130012 (China); Dong Xin [State Key Laboratory for Materials Modification by Laser, Ion, and Electron Beams and Department of Physics, Dalian University of Technology, Dalian 116024 (China); Xia Xiaochuan [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Qianjin Street 2699, Changchun 130012 (China); Cui Yongguo [State Key Laboratory for Materials Modification by Laser, Ion, and Electron Beams and Department of Physics, Dalian University of Technology, Dalian 116024 (China); Huang Keke [State Key Laboratory of Inorganic Synthesis and Preparation Chemistry, Jilin University, Qianjin Street 2699, Changchun 130012 (China); Du Guotong [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Qianjin Street 2699, Changchun 130012 (China); State Key Laboratory for Materials Modification by Laser, Ion, and Electron Beams and Department of Physics, Dalian University of Technology, Dalian 116024 (China)

    2008-01-30

    ZnO thin films were grown on (1 0 0) p-Si substrates by Photo-assisted Metal Organic Chemical Vapor Deposition (PA-MOCVD) using diethylzinc (DEZn) and O{sub 2} as source materials and tungsten-halogen lamp as a light source. The effects of tungsten-halogen lamp irradiation on the surface morphology, structural and optical properties of the deposited ZnO films have been investigated by means of atomic force microscope (AFM), X-ray diffraction and photoluminescence (PL) spectra measurements. Compared with the samples without irradiation, the several characteristics of ZnO films with irradiation are improved, including an improvement in the crystallinity of c-axis orientation, an increase in the grain size and an improvement in optical quality of ZnO films. These results indicated that light irradiation played an important role in the growth of ZnO films by PA-MOCVD.

  10. Properties of ZnO thin films grown on Si substrates by photo-assisted MOCVD

    International Nuclear Information System (INIS)

    ZnO thin films were grown on (1 0 0) p-Si substrates by Photo-assisted Metal Organic Chemical Vapor Deposition (PA-MOCVD) using diethylzinc (DEZn) and O2 as source materials and tungsten-halogen lamp as a light source. The effects of tungsten-halogen lamp irradiation on the surface morphology, structural and optical properties of the deposited ZnO films have been investigated by means of atomic force microscope (AFM), X-ray diffraction and photoluminescence (PL) spectra measurements. Compared with the samples without irradiation, the several characteristics of ZnO films with irradiation are improved, including an improvement in the crystallinity of c-axis orientation, an increase in the grain size and an improvement in optical quality of ZnO films. These results indicated that light irradiation played an important role in the growth of ZnO films by PA-MOCVD

  11. Investigations of ZnO thin films deposited by a reactive pulsed laser ablation

    Institute of Scientific and Technical Information of China (English)

    Y.; C.; SOO; H.; KANDEL; M.; A.; THOMAS; C.; P.; DAGHLIAN

    2009-01-01

    Highly transparent ZnO thin films were deposited at different substrate temperatures by pulsed laser deposition in an oxygen atmosphere. The thin films were characterized by various techniques including X-ray diffraction, scanning electron microscopy, optical absorption, and photoluminescence. We demonstrated that oriented wurtzite ZnO thin films could be deposited at room temperature using a high purity zinc target. Variable temperature photoluminescence revealed new characteristics in the band edge emission. The underlying mechanism for the observed phenomena was also discussed.

  12. Fabrication of superhydrophobic surface of hierarchical ZnO thin films by using stearic acid

    Science.gov (United States)

    Wang, Yanfen; Li, Benxia; Xu, Chuyang

    2012-01-01

    Flower-like hierarchical ZnO microspheres were successfully synthesized by a simple, template-free, and low-temperature aqueous solution route. The morphology and microstructure of the ZnO microspheres were examined by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The bionic films with hydrophobicity were fabricated by the hierarchical ZnO microspheres modified by stearic acid. It was found that the hydrophobicity of the thin films was very sensitive to the added amount of stearic acid. The thin films modified with 8% stearic acid took on strong superhydrophobicity with a water contact angle (CA) almost to be 178° and weak adhersion. The remarkable superhydrophobicity could be attributed to the synergistic effect of micro/nano hierarchical structure of ZnO and low surface energy of stearic acid.

  13. Ultrafast dynamics of ZnO and ZnO-BaTiO3 thin films

    Energy Technology Data Exchange (ETDEWEB)

    Acharya, Snigdhatanu; Chouthe, Sumedha; Seifert, Gerhard [Institute of Physics, Martin-Luther-University, Halle-Wittenberg, Von-Danckelmann Platz 3, D-06120, Halle (Germany); Boentgen, Tammo; Schmidt-Grund, Ruediger; Grundmann, Marius [Institute for Experimental Physics-II, University of Leipzig, Linnestrasse 5, D-04103 Leipzig (Germany)

    2011-07-01

    Femtosecond pump-probe spectroscopy was performed at room temperature on ZnO thin film and a double layer thin film structure of BaTiO{sub 3}/ZnO, to investigate coupling between the layers via the charge carrier dynamics. Frequency-doubled Ti:Sa laser pulses (150 fs, 400 nm) were used as pump; induced transmission changes were probed by supercontinuum (320-600 nm) fs pulses. For ZnO, two photon absorption as well as direct excitation to the trap states close to the conduction band edge leads to transfer of carriers to the conduction band. The displaced carriers relax rapidly to the bottom of conduction band, and bleaching at 375 nm attributed to population of discrete exciton A is observed. Further increase in the density at exciton levels lead to a stimulated emission at 390 nm due to exciton-exciton scattering. Changes in refractive index induced by pump-pulse generates interferometric transmission changes between 400-600 nm. Similar contributions to the transient spectra are observed in BaTiO{sub 3}/ZnO. BaTiO{sub 3} does not show any femtosecond response. Difference in the dynamical behaviour of the contributions in ZnO and BaTiO{sub 3}/ZnO gives an indication of coupling between ZnO and BaTiO{sub 3}.

  14. Laser molecular beam epitaxy of ZnO thin films and heterostructures

    OpenAIRE

    Opel, Matthias; Geprägs, Stephan; Althammer, Matthias; Brenninger, Thomas; Gross, Rudolf

    2013-01-01

    We report on the growth of epitaxial ZnO thin films and ZnO based heterostructures on sapphire substrates by laser molecular beam epitaxy (MBE). We first discuss some recent developments in laser-MBE such as flexible ultra-violet laser beam optics, infrared laser heating systems or the use of atomic oxygen and nitrogen sources, and describe the technical realization of our advanced laser-MBE system. Then we describe the optimization of the deposition parameters for ZnO films such as laser flu...

  15. Effects of Mn doping on electrical properties of ZnO thin films

    Science.gov (United States)

    Motevalizadeh, Leili; Shohany, Boshra Ghanbari; Abrishami, Majid Ebrahimizadeh

    2016-01-01

    In this paper, we have investigated the effect of Mn doping on the electrical properties of ZnO thin films. ZnO thin films with different amounts of Mn concentrations (0, 5, 10 and 15 mol.%) were prepared by spray pyrolysis technique. The crystal structure was examined by X-ray diffraction (XRD) analysis. XRD patterns showed that all the samples were crystallized in wurtzite structure while a decrease in crystallinity and switch in preferential orientations were observed in Mn-doped thin films comparing to undoped ZnO. The element composition of all thin films was detected by energy dispersive X-ray (EDX). The surface morphology of the films was investigated using field emission scanning electron microscope (FESEM) and optical properties were studied using UV-vis spectroscopy. UV-vis study revealed that the band gap blueshifts with the increase in Mn content and Eg increases with the increase in Mn concentration. The resistivity and activation energy were measured at room temperature and ranging from 373 K to 573 K. Comparing to undoped ZnO thin film, the resistivity of Mn-doped ZnO films increased because of different parameters such as increasing barrier height energy and reducing the oxygen deficiency.

  16. Strong adsorption of Al-doped carbon nanotubes toward cisplatin

    Science.gov (United States)

    Li, Wei; Li, Guo-Qing; Lu, Xiao-Min; Ma, Juan-Juan; Zeng, Peng-Yu; He, Qin-Yu; Wang, Yin-Zhen

    2016-08-01

    The adsorption of cisplatin molecule on Al-doped CNTs is investigated using density functional theory. The obtained results indicate that Al-doped carbon nanotubes can strongly absorb cisplatin. After absorbing cisplatin, the symmetry of CNTs has some changes. We innovatively defined a parameter of symmetry variation which relates to the adsorption. By analyzing the electronic structure, it can be concluded that under the circumstance that cisplatin was absorbed by Al-doped CNTs through aluminum atom of Al-doped CNTs. In conclusion, Al-doped CNTs is a kind of potential delivery carrier with high quality for anticancer drug cisplatin.

  17. Optical Properties of MEH-PPV Thin Films Containing ZnO Nanoparticles

    International Nuclear Information System (INIS)

    Thin films of poly [2-methoxy-5(2'-ethyl hexyloxy)-phenylene vinylene](MEH-PPV) containing different weight percent of ZnO nanoparticles were deposited by spin coating from THF solutions and their optical properties were investigated. Optical characterization of the nanocomposite thin films were performed by Ultraviolet-Visible Spectrophotometer (UV-Vis) and Photoluminescence Spectrometer while the thickness of the thin films was measured by using Surface Profiler. The UV-Vis absorption spectra of MEH-PPV: ZnO films showed a small red shift as compared with pure MEH-PPV. Similarly, a small red shift was found in PL emission spectra with increasing the content of ZnO nanoparticles.

  18. Laser-assisted sol-gel growth and characteristics of ZnO thin films

    International Nuclear Information System (INIS)

    ZnO thin films were grown on Si(100) substrates by a sol-gel method assisted by laser beam irradiation with a 325 nm He-Cd laser. In contrast to conventional sol-gel ZnO thin films, the surface morphology of the laser-assisted sol-gel thin films was much smoother, and the residual stress in the films was relaxed by laser irradiation. The luminescent properties of the films were also enhanced by laser irradiation, especially, by irradiation during the deposition and post-heat treatment stages. The incident laser beam is thought to play several roles, such as annihilating defects by accelerating crystallization during heat treatment, enhancing the surface migration of atoms and molecules, and relaxing the ZnO matrix structure during crystallization.

  19. Study on pulsed laser ablation and deposition of ZnO thin films by L-MBE

    Institute of Scientific and Technical Information of China (English)

    HE YongNing; ZHANG JingWen; YANG XiaoDong; XU QingAn; ZHU ChangChun; HOU Xun

    2007-01-01

    ZnO, as a wide-band gap semiconductor, has recently become a new research focus in the field of ultraviolet optoelectronic semiconductors. Laser molecular beam epitaxy (L-MBE) is quite useful for the unit cell layer-by-layer epitaxial growth of zinc oxide thin films from the sintered ceramic target. The ZnO ceramic target with high purity was ablated by KrF laser pulses in an ultra high vacuum to deposit ZnO thin film during the process of L-MBE. It is found that the deposition rate of ZnO thin film by L-MBE is much lower than that by conventional pulsed laser deposition (PLD). Based on the experimental phenomena in the ZnO thin film growth process and the thermal-controlling mechanism of the nanosecond (ns) pulsed laser ablation of ZnO ceramic target, the suggested effective ablating time during the pulse duration can explain the very low deposition rate of the ZnO film by L-MBE. The unique dynamic mechanism for growing ZnO thin film is analyzed. Both the high energy of the deposition species and the low growth rate of the film are really beneficial for the L-MBE growth of the ZnO thin film with high crystallinity at low temperature.

  20. Diffusion of phosphorus and arsenic using ampoule-tube method on undoped ZnO thin films and electrical and optical properties of P-type ZnO thin films

    Science.gov (United States)

    So, Soon-Jin; Park, Choon-Bae

    2005-12-01

    To investigate ZnO thin films, which are in the spotlight of next generation short wavelength LEDs and semiconductor lasers, the ZnO thin films were deposited using RF sputtering system in this study. The substrate temperature and work pressure were set at 300 °C and 5.2 mTorr, respectively, in the sputtering process of ZnO thin films and ZnO 5N was used as the purity target. The thickness of ZnO thin films was about 2.1 μm at the time of SEM analysis after the sputtering process. Phosphorus (P) and arsenic (As) were diffused in an ampoule tube of below 5×10 -7 Torr into the undoped ZnO thin films sputtered by RF magnetron sputtering system. The doping sources of phosphorus and arsenic were Zn 3P 2 and ZnAs 2. The diffusion of these elements was performed at the temperatures of 500, 600, and 700 °C for 3 h. Diffusion process of the conductive ZnO thin films, which have n-type and p-type properties, has been discovered. The ZnO thin films in this study showed not only very high carrier concentration of above 10 17/cm 3 but also low resistivity of below 2.0×10 -2 Ω cm.

  1. Nitrogen doping in pulsed laser deposited ZnO thin films using dense plasma focus

    International Nuclear Information System (INIS)

    Pulsed laser deposition synthesized ZnO thin films, grown at 400 deg. C substrate temperature in different oxygen gas pressures, were irradiated with 6 shots of pulsed nitrogen ions obtained from 2.94 kJ dense plasma focus to achieve the nitrogen doping in ZnO. Structural, compositional and optical properties of as-deposited and nitrogen ion irradiated ZnO thin films were investigated to confirm the successful doping of nitrogen in irradiated samples. Spectral changes have been seen in the nitrogen irradiated ZnO thin film samples from the low temperature PL measurements. Free electron to acceptor emissions can be observed from the irradiated samples, which hints towards the successful nitrogen doping in films. Compositional analysis by X-ray photoelectron spectroscopy and corresponding shifts in binding energy core peaks of oxygen and nitrogen confirmed the successful use of plasma focus device as a novel source for nitrogen ion doping in ZnO thin films.

  2. Sol-gel-deposited ZnO thin films: A review

    International Nuclear Information System (INIS)

    During the last years, ZnO thin films have been studied extensively due to their potential applications in e.g. piezoelectric and optoelectronic devices or photovoltaic cells. Ordered c-axis orientation of ZnO crystallites is desirable for applications where crystallographic anisotropy is a prerequisite such as for short-wavelength semiconductor diode lasers (SDLs), and piezoelectric surface acoustic wave or acousto-optic devices. Many works were dedicated to c-axis oriented ZnO thin films elaboration and the study of their properties, including physical and chemical methods. For instance, sol-gel processes are particularly well adapted to produce ZnO films in a simple, low-cost and highly controlled way. This review summarizes the main chemical routes used in the sol-gel synthesis of undoped ZnO thin films and highlights the chemical and physical parameters influencing their structural properties. In this process, the ZnO films synthesis includes three principal steps: (i) solution preparation, (ii) coating and (iii) heat treatment. For the first step, the particle formation is discussed including nucleation and growth, particle size, morphology and colloids stability. These three steps involve several parameters such as: (i) nature and concentration of precursor, solvent and additive, and solution aging time, for the chemical system, (ii) coating method, thickness and substrate for the coating step, and (iii) pre-and post-heat treatment for the last step. The influence of these steps and synthesis parameters on ZnO thin films orientation is discussed.

  3. Preparation of ZnO Thin Films on Free-Standing Diamond Substrates

    International Nuclear Information System (INIS)

    Highly c-axis-oriented ZnO films were deposited successfully on the nucleation sides of free-standing diamond (FD) films by the direct current (DC) magnetron sputtering method. The effect of the sputtering parameters, such as power, gas pressure and sputtering plasma composition of Ar-to-O2, on the properties of ZnO thin films was investigated in detail. X-ray diffraction (XRD) measurements showed that, at a sputtering power of 200 W, gas pressure of 0.5 Pa and an Ar-to-O2 composition of 1:1, a higher intensity of the (002) diffraction peak and a narrower full width at half maximum (FWHM) were detected which meant high c-axis orientation and high quality of the ZnO films. To improve the quality of the ZnO film, a thin ZnO layer was pre-grown as a homo-buffer layer. XRD measurements showed that this buffer layer had a beneficial effect on the structural and morphological properties of the post-grown ZnO film. (low temperature plasma)

  4. Influence of PANI Additions on Methanol Sensing Properties of ZnO Thin Films

    International Nuclear Information System (INIS)

    The influence of PANI additions on methanol sensing properties of ZnO thin films at room temperature had been investigated. Commercial poly aniline powder (PANI) was mixed into 3 mL ZnO solution in five different weight percentages namely 1.25, 2.50, 3.75, 5.00 and 6.25 % to obtain ZnO/ PANI composite solutions. These solutions were spin coated onto glass substrate to form thin films. Microstructural studies by FESEM indicated that ZnO/ PANI films showed porous structures with nano size grains. The thickness of the film increased from 55 to 256 nm, proportionate to increment of PANI. The presence of 2 adsorption peaks at ∼310 nm and ∼610 nm in UV-Vis spectrum proved that addition of PANI has modified the adsorption peak of ZnO film. Methanol vapour detection showed that addition of PANI into ZnO dramatically improved the sensing properties of the sensor. The sensors also exhibited good repeatability and reversibility. Sensor with the amount of PANI of 3.75 wt % exhibited the highest sensitivity with response and recovery time was about 10 and 80 s, respectively. The possible sensing mechanism of the sensor was also discussed in this article. (author)

  5. Degenerate interface layers in epitaxial scandium-doped ZnO thin films

    International Nuclear Information System (INIS)

    Scandium is a donor in ZnO, in contradiction to all heavier 3d-elements. Although the Sc3+ ion fits exactly the size of Zn2+, the conductivity of epitaxial Sc-doped ZnO thin films is dominated by a degenerated interface layer with pronounced Sc accumulation in the concentration depth profile. Electron paramagnetic resonance clearly excludes the isovalent oxidation state Sc2+ in ZnO, in agreement with the low resistivity of homoepitaxial ZnO:Sc of 1.3 × 10-2 Ω cm and high Hall mobility of 139 cm2 V-1 s-1 at 300 K. Employing the two-layer Hall model of Look and Molnar, a maximum Hall mobility of the volume part of the ZnO:Sc layer of 650 cm2 V-1 s-1 at 95 K was extracted. Thermal activation energies of the donors are 28 and 43 meV for a homoepitaxial ZnO:0.1% Sc film. Homoepitaxial ZnO films with 0.1 and 1 at% Sc on c-plane ZnO are almost phase pure and in-plane lattice matched with perpendicular compressive strain up to 1%. Heteroepitaxial ZnO:Sc on a-plane sapphire shows secondary XRD peaks, pointing to a limited solubility of Sc in ZnO.

  6. Nonlinear optical parameters of nanocrystalline AZO thin film measured at different substrate temperatures

    Science.gov (United States)

    Jilani, Asim; Abdel-wahab, M. Sh; Al-ghamdi, Attieh A.; Dahlan, Ammar sadik; Yahia, I. S.

    2016-01-01

    The 2.2 wt% of aluminum (Al)-doped zinc oxide (AZO) transparent and preferential c-axis oriented thin films were prepared by using radio frequency (DC/RF) magnetron sputtering at different substrate temperature ranging from room temperature to 200 °C. For structural analysis, X-ray Diffraction (XRD) and Atomic Force Electron Microscope (AFM) was used for morphological studies. The optical parameters such as, optical energy gap, refractive index, extinction coefficient, dielectric loss, tangent loss, first and third order nonlinear optical properties of transparent films were investigated. High transmittance above 90% and highly homogeneous surface were observed in all samples. The substrate temperature plays an important role to get the best transparent conductive oxide thin films. The substrate temperature at 150 °C showed the growth of highly transparent AZO thin film. Energy gap increased with the increased in substrate temperature of Al doped thin films. Dielectric constant and loss were found to be photon energy dependent with substrate temperature. The change in substrate temperature of Al doped thin films also affect the non-liner optical properties of thin films. The value of χ(3) was found to be changed with the grain size of the thin films that directly affected by the substrate temperature of the pure and Al doped ZnO thin films.

  7. Structural, electronic and magnetic properties of Er implanted ZnO thin films

    International Nuclear Information System (INIS)

    We report the structural, electronic and magnetic properties of Er implanted and annealed ZnO thin films. The effect of annealing in oxygen-deficient and oxygen-rich conditions was investigated. Rutherford backscattering spectrometry results revealed that the Er atoms are located at the implantation depth of around 13 nm, and annealing conditions had no adverse effect on the Er concentration in the layer. Raman spectroscopy results showed peak related to E2(high) mode of ZnO indicating enhanced crystalline quality of the Er implanted and annealed ZnO films. X-ray absorption near edge spectroscopy results demonstrated pre-edge features in O K-edge which are attributed to the structural defects in the films. Room temperature magnetic ordering was observed in Er implanted and annealed films, and is mainly assigned to the intrinsic defects in ZnO

  8. Structural, electronic and magnetic properties of Er implanted ZnO thin films

    Science.gov (United States)

    Murmu, P. P.; Kennedy, J.; Ruck, B. J.; Leveneur, J.

    2015-09-01

    We report the structural, electronic and magnetic properties of Er implanted and annealed ZnO thin films. The effect of annealing in oxygen-deficient and oxygen-rich conditions was investigated. Rutherford backscattering spectrometry results revealed that the Er atoms are located at the implantation depth of around 13 nm, and annealing conditions had no adverse effect on the Er concentration in the layer. Raman spectroscopy results showed peak related to E2(high) mode of ZnO indicating enhanced crystalline quality of the Er implanted and annealed ZnO films. X-ray absorption near edge spectroscopy results demonstrated pre-edge features in O K-edge which are attributed to the structural defects in the films. Room temperature magnetic ordering was observed in Er implanted and annealed films, and is mainly assigned to the intrinsic defects in ZnO.

  9. Structural, electronic and magnetic properties of Er implanted ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Murmu, P.P. [National Isotope Centre, GNS Science, PO Box 31312, Lower Hutt 5010 (New Zealand); The MacDiarmid Institute for Advanced Materials and Nanotechnology, PO Box 600, Wellington 6140 (New Zealand); Kennedy, J., E-mail: J.Kennedy@gns.cri.nz [National Isotope Centre, GNS Science, PO Box 31312, Lower Hutt 5010 (New Zealand); The MacDiarmid Institute for Advanced Materials and Nanotechnology, PO Box 600, Wellington 6140 (New Zealand); Ruck, B.J. [The MacDiarmid Institute for Advanced Materials and Nanotechnology, PO Box 600, Wellington 6140 (New Zealand); Leveneur, J. [National Isotope Centre, GNS Science, PO Box 31312, Lower Hutt 5010 (New Zealand)

    2015-09-15

    We report the structural, electronic and magnetic properties of Er implanted and annealed ZnO thin films. The effect of annealing in oxygen-deficient and oxygen-rich conditions was investigated. Rutherford backscattering spectrometry results revealed that the Er atoms are located at the implantation depth of around 13 nm, and annealing conditions had no adverse effect on the Er concentration in the layer. Raman spectroscopy results showed peak related to E{sub 2}(high) mode of ZnO indicating enhanced crystalline quality of the Er implanted and annealed ZnO films. X-ray absorption near edge spectroscopy results demonstrated pre-edge features in O K-edge which are attributed to the structural defects in the films. Room temperature magnetic ordering was observed in Er implanted and annealed films, and is mainly assigned to the intrinsic defects in ZnO.

  10. Quantum corrections to low temperature electrical conductivity in Dy doped ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Ajimsha, R.S., E-mail: ajimsha@gmail.com; Das, Amit K.; Joshi, M.P.; Kukreja, L.M.

    2015-08-31

    We have grown thin films of Dy doped ZnO (Dy:ZnO) on sapphire substrate using pulsed laser deposition with Dy concentration varying from 0.05 at.% to 1.8 at.%. These as grown Dy:ZnO thin films were characterized using low temperature four probe electrical measurements (in the range ~ 300 K to 4 K). All the Dy:ZnO thin films showed metal like behavior with a transition from positive to negative temperature coefficient of resistivity (TCR) and again to positive TCR with an increase of Dy concentration. This anomaly in conduction mechanism was investigated by considering quantum corrections to classical Boltzmann conductivity. All the Dy:ZnO thin films also exhibited negative magneto-resistance that supported for a significant contribution of weak localization in quantum corrections to conductivity. - Highlights: • Dy doped ZnO films were grown on sapphire substrate using pulsed laser deposition. • All the Dy doped ZnO films show metal like behavior according to Mott's criteria. • All the Dy doped ZnO thin films exhibited negative magneto-resistance. • Observation of weak localization leading to Quantum corrections to conductivity.

  11. Synthesis, structural and optical characterization of undoped, N-doped ZnO and co-doped ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Pathak, Trilok Kumar, E-mail: tpathak01@gmail.com; Kumar, R.; Purohit, L. P., E-mail: proflppurohitphys@gmail.com [Semiconductor Research Lab., Department of Physics, Gurukula Kangri University, Haridwar (India)

    2015-05-15

    ZnO, N-doped ZnO and Al-N co-doped ZnO thin films were deposited on ITO coated corning glass by spin coater using sol-gel method. The films were annealed in air at 450°C for one hour. The crystallographic structure and morphology of the films were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively. The X-ray diffraction results confirm that the thin films are of wurtzite hexagonal with a very small distortion. The optical properties were investigated by transmission spectra of different films using spectrophotometer (Shimadzu UV-VIS-NIR 3600). The results indicate that the N doped ZnO thin films have obviously enhanced transmittance in visible region. Moreover, the thickness of the films has strong influences on the optical constants.

  12. Random lasing of ZnO thin films grown by pulsed-laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Cachoncinlle, C., E-mail: christophe.cachoncinlle@univ-orleans.fr [GREMI, UMR 7344 CNRS—Université Orléans, 45067 Orléans Cedex 2 (France); Hebert, C.; Perrière, J. [Sorbonne Universités, UPMC Université Paris 06, UMR 7588, INSP, 75005 Paris (France); CNRS, UMR 7588, INSP, 75005 Paris (France); Nistor, M. [NILPRP, L 22 PO Box. MG-36, 77125 Bucharest—Magurele (Romania); Petit, A.; Millon, E. [GREMI, UMR 7344 CNRS—Université Orléans, 45067 Orléans Cedex 2 (France)

    2015-05-01

    Highlights: • Random lasing at RT in nanocrystalline ZnO PLD thin film (<100 nm). • Low optical pumping threshold (<30 kW cm{sup −2}) for UV random lasing. • Random lasing interpreted by the electron-hole plasma (EHP) model. - Abstract: Low-dimensional semiconductor structures on nanometer scale are of great interest because of their strong potential applications in nanotechnologies. We report here optical and structural properties on UV lasing in ZnO thin films. The ZnO films, 110 nm thick, were prepared using pulsed-laser deposition on c-cut sapphire substrates at 500 °C under 10{sup −2} oxygen pressure. The ZnO films are nearly stoichiometric, dense and display the wurtzite phase. The films are highly textured along the ZnO c-axis and are constituted of nanocrystallites. According to Hall measurements these films are conductive (0.11 Ω cm). Photoluminescence measurements reveals a so-called random lasing in the range 390 to 410 nm, when illuminating at 355 nm with a tripled frequency pulsed Nd-YAG laser. Such random lasing is obtained at rather low optical pumping, 45 kW cm{sup −2}, a value lower than those classically reported for pulsed-laser deposition thin films.

  13. Random lasing of ZnO thin films grown by pulsed-laser deposition

    International Nuclear Information System (INIS)

    Highlights: • Random lasing at RT in nanocrystalline ZnO PLD thin film (<100 nm). • Low optical pumping threshold (<30 kW cm−2) for UV random lasing. • Random lasing interpreted by the electron-hole plasma (EHP) model. - Abstract: Low-dimensional semiconductor structures on nanometer scale are of great interest because of their strong potential applications in nanotechnologies. We report here optical and structural properties on UV lasing in ZnO thin films. The ZnO films, 110 nm thick, were prepared using pulsed-laser deposition on c-cut sapphire substrates at 500 °C under 10−2 oxygen pressure. The ZnO films are nearly stoichiometric, dense and display the wurtzite phase. The films are highly textured along the ZnO c-axis and are constituted of nanocrystallites. According to Hall measurements these films are conductive (0.11 Ω cm). Photoluminescence measurements reveals a so-called random lasing in the range 390 to 410 nm, when illuminating at 355 nm with a tripled frequency pulsed Nd-YAG laser. Such random lasing is obtained at rather low optical pumping, 45 kW cm−2, a value lower than those classically reported for pulsed-laser deposition thin films

  14. Study on pulsed laser ablation and deposition of ZnO thin films by L-MBE

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    ZnO,as a wide-band gap semiconductor,has recently become a new research fo-cus in the field of ultraviolet optoelectronic semiconductors. Laser molecular beam epitaxy(L-MBE) is quite useful for the unit cell layer-by-layer epitaxial growth of zinc oxide thin films from the sintered ceramic target. The ZnO ceramic target with high purity was ablated by KrF laser pulses in an ultra high vacuum to deposit ZnO thin film during the process of L-MBE. It is found that the deposition rate of ZnO thin film by L-MBE is much lower than that by conventional pulsed laser deposition(PLD) . Based on the experimental phenomena in the ZnO thin film growth process and the thermal-controlling mechanism of the nanosecond(ns) pulsed laser abla-tion of ZnO ceramic target,the suggested effective ablating time during the pulse duration can explain the very low deposition rate of the ZnO film by L-MBE. The unique dynamic mechanism for growing ZnO thin film is analyzed. Both the high energy of the deposition species and the low growth rate of the film are really beneficial for the L-MBE growth of the ZnO thin film with high crystallinity at low temperature.

  15. Effect of hydrogen doping in ZnO thin films by pulsed DC magnetron sputtering

    International Nuclear Information System (INIS)

    This study examined the role of hydrogen impurities in highly oriented ZnO thin films. Hydrogen intentionally incorporated was found to play an important role as a donor in n-type conduction, improving the free carrier concentration. The increase in the conductivity of ZnO thin films was attributed to the two centers assigned to isolated hydrogen atoms in the anti-bonding sites as well as bond-centered interstitial hydrogen located between the Zn-O bonds and Zn vacancy passivated by one or two hydrogen atoms. Micro Raman spectroscopy showed two additional modes at approximately 501 and 573 cm-1. These two peaks were attributed to damage to the crystal lattice, which could be explained by the optical-phonon branch at the zone boundary and host lattice defects, such as vacancy clusters, respectively.

  16. ZnO thin film synthesis by reactive radio frequency magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Şenay, Volkan, E-mail: vsenay@bayburt.edu.tr [Bayburt University, Primary Science Education Department, Bayburt, 69000 (Turkey); Pat, Suat; Korkmaz, Şadan; Aydoğmuş, Tuna; Elmas, Saliha; Özen, Soner; Ekem, Naci [Eskisehir Osmangazi University, Physics Department, Eskisehir, 26480 (Turkey); Balbağ, M. Zafer [Eskisehir Osmangazi University, Education Faculty, Eskisehir, 26480 (Turkey)

    2014-11-01

    Highlights: • Band gaps of the layer are affected by the film thickness. • Nano structured ZnO deposited. • Spectral dependence of reflectance of deposited ZnO thin films. - Abstract: In this study, ZnO thin films were deposited on glass substrates by reactive RF magnetron sputtering method at argon–oxygen gas mixing (1:1) atmosphere. Some properties of the synthesized films were investigated by interferometry, UV–vis spectrophotometer, atomic force microscopy, and tensiometer. Tauc method was adopted to estimate the optical band gaps. The band gaps of the deposited films were affected by film thickness. We concluded that the surface composition plays a substantial role in the values of the band gaps. Nanocrystalline structures were detected in all produced samples.

  17. Nanostructured ZnO thin films prepared by sol–gel spin-coating

    Energy Technology Data Exchange (ETDEWEB)

    Heredia, E., E-mail: heredia.edu@gmail.com [UNIDEF (CONICET-MINDEF), J.B. de La Salle 4397, 1603 Villa Martelli, Pcia. de Buenos Aires (Argentina); Bojorge, C.; Casanova, J.; Cánepa, H. [UNIDEF (CONICET-MINDEF), J.B. de La Salle 4397, 1603 Villa Martelli, Pcia. de Buenos Aires (Argentina); Craievich, A. [Instituto de Física, Universidade de São Paulo, Cidade Universitária, 66318 São Paulo, SP (Brazil); Kellermann, G. [Universidade Federal do Paraná, 19044 Paraná (Brazil)

    2014-10-30

    Highlights: • ZnO films synthesized by sol–gel were deposited by spin-coating on flat substrates. • Structural features of ZnO films with several thicknesses were characterized by means of different techniques. • The thicknesses of different ZnO thin films were determined by means of FESEM and AFM. • The nanoporous structures of ZnO thin films were characterized by GISAXS using IsGISAXS software. • The average densities of ZnO thin films were derived from (i) the critical angle in 1D XR patterns, (ii) the angle of Yoneda peak in 2D GISAXS images, (iii) minimization of chi2 using IsGISAXS best fitting procedure. - Abstract: ZnO thin films deposited on silica flat plates were prepared by spin-coating and studied by applying several techniques for structural characterization. The films were prepared by depositing different numbers of layers, each deposition being followed by a thermal treatment at 200 °C to dry and consolidate the successive layers. After depositing all layers, a final thermal treatment at 450 °C during 3 h was also applied in order to eliminate organic components and to promote the crystallization of the thin films. The total thickness of the multilayered films – ranging from 40 nm up to 150 nm – was determined by AFM and FESEM. The analysis by GIXD showed that the thin films are composed of ZnO crystallites with an average diameter of 25 nm circa. XR results demonstrated that the thin films also exhibit a large volume fraction of nanoporosity, typically 30–40 vol.% in thin films having thicknesses larger than ∼70 nm. GISAXS measurements showed that the experimental scattering intensity is well described by a structural model composed of nanopores with shape of oblate spheroids, height/diameter aspect ratio within the 0.8–0.9 range and average diameter along the sample surface plane in the 5–7 nm range.

  18. Ti doped ZnO thin film based UV photodetector: Fabrication and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Shewale, P.S.; Lee, N.K.; Lee, S.H.; Kang, K.Y. [Convergence of IT Devices Institute, Dong-Eui University, Busan 614-714 (Korea, Republic of); Yu, Y.S., E-mail: ysyu@deu.ac.kr [Convergence of IT Devices Institute, Dong-Eui University, Busan 614-714 (Korea, Republic of); Department of Radiological Science, Dong-Eui University, Busan 614-714 (Korea, Republic of)

    2015-03-05

    Highlights: • UV photoconductive undoped and Ti doped ZnO films were grown by spray pyrolysis. • Ti doping effects on physical and UV detection properties of films were studied. • Samples are polycrystalline with a hexagonal wurtzite crystal structure. • Ti doping increases the optical transmittance and band gap of ZnO film. • Ti doping improves the responsivity of ZnO film based MSM UV photodetector. - Abstract: This paper presents the synthesis of undoped and 2 wt.% titanium (Ti) doped zinc oxide (ZnO) thin films onto glass substrates by chemical spray pyrolysis technique. Both films are deposited at 375 °C substrate temperature. The influence of Ti doping on structural, morphological, optical and UV detection properties of ZnO film was studied. Both films revealed to be of polycrystalline nature with a hexagonal wurtzite structure; and the ZnO film crystallinity improved on Ti doping. Surface morphological observations agreed well with structural results. The Ti incorporation in ZnO thin films were confirmed by an energy dispersive X-ray spectroscopic analysis (EDX). The Ti doping increased the optical transmittance (∼96% at 550) and band gap (∼3.2927 eV) of ZnO thin film. Further, the metal–semiconductor–metal (MSM) planar ultraviolet photodetectors (UV PDs) were fabricated from deposition of tin (Sn) contacts onto undoped and Ti doped ZnO films using e-beam evaporation technique. To investigate UV photodetection properties, the MSM devices were subjected to current–voltage (I–V) characteristics measurements of forward and reverse bias in dark and UV light conditions. The photocurrent and responsivity were measured as a function of optical power density and applied voltage, respectively. The reproducibility of the UV detection performance of MSM devices was ensured by constantly switching UV light on and off at regular time intervals. The Ti doped ZnO film based UV PD demonstrates highest responsivity of about 0.051 A/W upon 2 mW/cm{sup 2

  19. Superhydrophobic nanostructured ZnO thin films on aluminum alloy substrates by electrophoretic deposition process

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Fabrication of superhydrophobic ZnO thin films surfaces by electrophoretic deposition process on aluminum substrates. • Effect of bath temperature on the physical and superhydrophobic properties of thin films. • The water contact angle of 155° ± 3 with roll off property has been observed on the film that was grown at bath temperatures of 50 °C. • The activation energy for electrophoretic deposition of SA-functionalized ZnO nanoparticle is calculated to be 0.50 eV. - Abstract: Superhydrophobic thin films have been fabricated on aluminum alloy substrates by electrophoretic deposition (EPD) process using stearic acid (SA) functionalized zinc oxide (ZnO) nanoparticles suspension in alcohols at varying bath temperatures. The deposited thin films have been characterized using both X-ray diffraction (XRD) and infrared (IR) spectroscopy and it is found that the films contain low surface energy zinc stearate and ZnO nanoparticles. It is also observed that the atomic percentage of Zn and O, roughness and water contact angle of the thin films increase with the increase of the deposited bath temperature. Furthermore, the thin film deposited at 50 °C, having a roughness of 4.54 ± 0.23 μm, shows superhydrophobic properties providing a water contact angle of 155 ± 3° with rolling off properties. Also, the activation energy of electrophoretic deposition of stearic-acid-functionalized ZnO nanoparticles is calculated to be 0.5 eV

  20. Superhydrophobic nanostructured ZnO thin films on aluminum alloy substrates by electrophoretic deposition process

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Ying; Sarkar, D.K., E-mail: dsarkar@uqac.ca; Chen, X-Grant

    2015-02-01

    Graphical abstract: - Highlights: • Fabrication of superhydrophobic ZnO thin films surfaces by electrophoretic deposition process on aluminum substrates. • Effect of bath temperature on the physical and superhydrophobic properties of thin films. • The water contact angle of 155° ± 3 with roll off property has been observed on the film that was grown at bath temperatures of 50 °C. • The activation energy for electrophoretic deposition of SA-functionalized ZnO nanoparticle is calculated to be 0.50 eV. - Abstract: Superhydrophobic thin films have been fabricated on aluminum alloy substrates by electrophoretic deposition (EPD) process using stearic acid (SA) functionalized zinc oxide (ZnO) nanoparticles suspension in alcohols at varying bath temperatures. The deposited thin films have been characterized using both X-ray diffraction (XRD) and infrared (IR) spectroscopy and it is found that the films contain low surface energy zinc stearate and ZnO nanoparticles. It is also observed that the atomic percentage of Zn and O, roughness and water contact angle of the thin films increase with the increase of the deposited bath temperature. Furthermore, the thin film deposited at 50 °C, having a roughness of 4.54 ± 0.23 μm, shows superhydrophobic properties providing a water contact angle of 155 ± 3° with rolling off properties. Also, the activation energy of electrophoretic deposition of stearic-acid-functionalized ZnO nanoparticles is calculated to be 0.5 eV.

  1. Enhanced the photocatalytic activity of Ni-doped ZnO thin films: Morphological, optical and XPS analysis

    Science.gov (United States)

    Abdel-wahab, M. Sh.; Jilani, Asim; Yahia, I. S.; Al-Ghamdi, Attieh A.

    2016-06-01

    Pure and Ni-doped ZnO thin films with different concentration of Ni (3.5 wt%, 5 wt%, 7 wt%) were prepared by DC/RF magnetron sputtering technique. The X-rays diffraction pattern showed the polycrystalline nature of pure and Ni-doped ZnO thin films. The surface morphology of pure and Ni doped ZnO thin films were investigated through atomic force microscope, which indicated the increase in the grain dimension and surface roughness with increasing the Ni doping. The UV-Visible transmission spectra showed the decrease in the transmittance of doped ZnO thin films with the incorporation of Ni dopants. The surface and chemical state analysis of pure and Ni doped ZnO thin films were investigated by X-rays photoelectron spectroscopy (XPS). The photocatalytic activities were evaluated by an aqueous solution of methyl green dye. The tungsten lamp of 500 W was used as a source of visible light for photocatalytic study. The degradation results showed that the Ni-doped ZnO thin films exhibit highly enhanced photocatalytic activity as compared to the pure ZnO thin films. The enhanced photocatalytic activities of Ni-doped ZnO thin films were attributed to the enhanced surface area (surface defects), surface roughness and decreasing the band gap of Ni-doped ZnO thin films. Our work supports the applications of thin film metal oxides in waste water treatment.

  2. Homoepitaxial growth of ZnO thin film by pulsed laser deposition (PLD)

    Energy Technology Data Exchange (ETDEWEB)

    Brandt, Matthias; Wenckstern, Holger von; Hanisch, Christian; Hochmuth, Holger; Lorenz, Michael; Schmidt, Heidemarie; Grundmann, Marius [Universitaet Leipzig, Semiconductor Physics Group, Institut fuer ExperimentellePhysik II, Leipzig (Germany)

    2007-07-01

    In this work ZnO thin films have been deposited homoepitaxially by PLD on ZnO single crystals grown by the hydrothermal method (purchased from CrysTec GmbH). These wafers have first been investigated by atomic force microscopy (AFM) and were found to show significant surface roughness in the as-received state. Therefore a thermal annealing method has been applied to the wafers prior to thin film growth, in order to improve the surface properties. An overview of the changes during annealing will be presented along with information on the optimal conditions for thermal annealing. Structural, morphological, optical and electrical properties of the thin films grown homoepitaxially on these optimized wafers will be discussed with respect to the growth conditions. Comparisons to properties of thin films grown heteroepitaxially on sapphire (Al{sub 2}O{sub 3}) and SCAM (ScAlM{sub g}O{sub 4}) will be provided.

  3. Multifunctional Thin Layers of ZnO Prepared by PECVD (Surfatron)

    Czech Academy of Sciences Publication Activity Database

    Dytrych, Pavel; Klusoň, Petr; Krystyník, Pavel; Šolcová, Olga

    - : -, 2013, s. 114. ISBN N. [Chemistry, Physics and Technology of Surface. Kyiv (UA), 15.05.2013-17.05.2013] Grant ostatní: NATO(US) SPS984398 Institutional support: RVO:67985858 Keywords : ZnO particles * thin layers * nano structures Subject RIV: CC - Organic Chemistry

  4. Hydrogen absorption in thin ZnO films prepared by pulsed laser deposition

    Czech Academy of Sciences Publication Activity Database

    Melikhova, O.; Čížek, J.; Lukáč, F.; Vlček, M.; Novotný, Michal; Bulíř, Jiří; Lančok, Ján; Anwand, W.; Brauer, G.; Connolly, J.; McCarthy, E.; Krishnamurthy, S.; Mosnier, J.-P.

    2013-01-01

    Roč. 580, suppl. 1 (2013), S40-S43. ISSN 0925-8388 R&D Projects: GA ČR(CZ) GAP108/11/0958 Institutional support: RVO:68378271 Keywords : defects * hydrogen * positron annihilation * thin films * ZnO Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.726, year: 2013

  5. Study of the wettability of ZnO nanofilms

    Science.gov (United States)

    Subedi, Deepak Prasad; Madhup, Dinesh Kumar; Sharma, Ashish; Joshi, Ujjwal Man; Huczko, Andrzej

    2012-04-01

    Al-doped and un-doped ZnO thin films deposited on quartz substrates by the nebulized spray pyrolysis method were studied to investigate the wettability of the surface. The main objective of the present study was to investigate the wettability of ZnO thin film by changing the concentration of Al doping. Microstructure and water contact angles of the films were measured by scanning electron microscopy (SEM) and using a contact angle goniometer. SEM studies revealed that the grain size within the film increases with the doping concentration. The contact angles were studied to see the effect of aluminum doping on the hydrophilicity of the film. ZnO films were found to be hydrophobic in nature. A good correlation was observed between the SEM micrographs and contact angle results. The nature of the film was found to change from being hydrophobic to hydrophilic after the treatment in low-pressure DC glow discharge plasma, which, however, was reversible with the storage time.

  6. Retracted: Study of the wettability of ZnO nanofilms

    Directory of Open Access Journals (Sweden)

    Ujjwal M Joshi

    2012-04-01

    Full Text Available Al-doped and un-doped ZnO thin films deposited on quartz substrates by the nebulized spray pyrolysis method were studied to investigate the wettability of the surface. The main objective of the present study was to investigate the wettability of ZnO thin film by changing the concentration of Al doping. Microstructure and water contact angles of the films were measured by scanning electron microscopy (SEM and using a contact angle goniometer. SEM studies revealed that the grain size within the film increases with the doping concentration. The contact angles were studied to see the effect of aluminum doping on the hydrophilicity of the film. ZnO films were found to be hydrophobic in nature. A good correlation was observed between the SEM micrographs and contact angle results. The nature of the film was found to change from being hydrophobic to hydrophilic after the treatment in low-pressure DC glow discharge plasma, which, however, was reversible with the storage time.

  7. Heteroepitaxial growth of nonpolar Cu-doped ZnO thin film on MnS-buffered (100) Si substrate

    Science.gov (United States)

    Nakamura, Tatsuru; Nguyen, Nam; Nagata, Takahiro; Takahashi, Kenichiro; Ri, Sung-Gi; Ishibashi, Keiji; Suzuki, Setsu; Chikyow, Toyohiro

    2015-06-01

    The preparation of nonpolar ZnO and Cu-doped ZnO thin films on Si substrates was studied for the application to the fabrication of green-light-emitting diodes. The use of rocksalt MnS and wurtzite AlN as buffer layers is a key technology for achieving the heteroepitaxial growth of nonpolar ZnO thin film on a (100) Si substrate. X-ray diffraction and photoluminescence measurements revealed that deposition under a high oxygen partial pressure (∼1 Torr) can enhance the nonpolar crystallization of undoped ZnO, and can simultaneously suppress the formation of defects such as oxygen vacancies. These techniques can be also applied to the growth of Cu-doped ZnO. A room-temperature photoluminescence study revealed that nonpolar [11\\bar{2}0]-oriented Cu-doped ZnO film exhibits enhanced green emission owing to the doped Cu ions.

  8. Reactive Radiofrequency Sputtering-Deposited Nanocrystalline ZnO Thin-Film Transistors

    International Nuclear Information System (INIS)

    The structural and electrical properties of ZnO films deposited by reactive radiofrequency sputtering with a metallic zinc target are systematically investigated. While the as-deposited ZnO film is in a poly-crystalline structure when the partial pressure of oxygen (pO2) is low, the grain size abruptly decreases to a few nanometers as pO2 increases to a critical value, and then becomes almost unchanged with a further increase in pO2. In addition, the resistivity of the ZnO films shows a non-monotonic dependence on pO2, including an abrupt transition of about seven orders of magnitude at the critical pO2. Thin-film transistors (TFTs) with the nanocrystalline ZnO films as channel layers have an on/off current ratio of more than 107, an off-current in the order of pA, a threshold voltage of about 4.5 V, and a carrier mobility of about 2cm2/(V·s). The results show that radiofrequency sputtered ZnO with a zinc target is a promising candidate for high-performance ZnO TFTs. (cross-disciplinary physics and related areas of science and technology)

  9. Characterization of ZnO thin films grown on various substrates by RF magnetron sputtering

    International Nuclear Information System (INIS)

    In this study we investigated properties of ZnO thin films deposited on both oxygen-containing substrates and a substrate without oxygen content at various O2/Ar reactant gas ratios. Deposition of ZnO on indium-tin oxide (ITO) resulted in the best crystallinity, whereas the least degree of crystallization was observed from ZnO deposited on glass. All the films were found to have compressive stress, which was relieved by annealing in O2 environment. ZnO films deposited on glass revealed p-type conductivity when prepared at O2/Ar ratio of 0.25 whereas those on SiNx yielded p-type conductivity when prepared at O2/Ar ratio of 4. In addition, shallower oxygen interstitial seemed to be found from films with better crystallinity. The largest shift in binding energy of Zn2p3/2 was observed from ZnO prepared on glass at O2/Ar ratio of 0.25, whereas that of O1s was obtained from ZnO deposited on SiNx at O2/Ar ratio of 4. A model was proposed in terms of O2 diffusion and hydrogen desorption in order to account for the observed property variations depending on substrates and O2/Ar ratios.

  10. Pulsed laser deposition of piezoelectric ZnO thin films for bulk acoustic wave devices

    Energy Technology Data Exchange (ETDEWEB)

    Serhane, Rafik, E-mail: rserhane@cdta.dz [Centre for Development of Advanced Technologies, Cité 20 Août 1956, Baba Hassen, BP: 17, DZ-16303 Algiers (Algeria); Abdelli-Messaci, Samira; Lafane, Slimane; Khales, Hammouche; Aouimeur, Walid [Centre for Development of Advanced Technologies, Cité 20 Août 1956, Baba Hassen, BP: 17, DZ-16303 Algiers (Algeria); Hassein-Bey, Abdelkadder [Centre for Development of Advanced Technologies, Cité 20 Août 1956, Baba Hassen, BP: 17, DZ-16303 Algiers (Algeria); Micro and Nano Physics Group, Faculty of Sciences, University Saad Dahlab of Blida (USDB), BP. 270, DZ-09000 Blida (Algeria); Boutkedjirt, Tarek [Equipe de Recherche Physique des Ultrasons, Faculté de Physique, Université des Sciences et de la Technologie Houari Boumediene (USTHB), BP 32, El-Alia, Bab-Ezzouar, DZ-16111 Algiers (Algeria)

    2014-01-01

    Piezoelectric properties of ZnO thin films have been investigated for micro-electro-mechanical systems (MEMS). Wurtzite ZnO structure was prepared on different substrates (Si (1 0 0), Pt (1 1 1)/Ti/SiO{sub 2}/Si and Al (1 1 1)/SiO{sub 2}/Si) at different substrate temperatures (from 100 to 500 °C) by a pulsed laser deposition (PLD) technique. X-ray diffraction (XRD) characterization showed that the ZnO films were highly c-axis (0 0 2) oriented, which is of interest for various piezoelectric applications. Scanning electron microscopy (SEM) showed evidence of honeycomb-like structure on the surface and columnar structure on the cross-section. In the case of ZnO on Al, ZnO exhibited an amorphous phase at the ZnO/Al interface. The XRD measurements indicated that the substrate temperature of 300 °C was the optimum condition to obtain high quality (strongest (0 0 2) peak with the biggest associated grain size) of crystalline ZnO on Pt and on Al and that 400 °C was the optimum one on Si. ZnO on Al exhibits smallest rocking curve width than on Pt, leading to better crystalline quality. The ZnO films were used in bulk acoustic wave (BAW) transducer. Electrical measurements of the input impedance and S-Parameters showed evidence of piezoelectric response. The electromechanical coupling coefficient was evaluated as K{sub eff}{sup 2}=5.09%, with a quality factor Q{sub r} = 1001.4.

  11. Pulsed laser deposition of piezoelectric ZnO thin films for bulk acoustic wave devices

    International Nuclear Information System (INIS)

    Piezoelectric properties of ZnO thin films have been investigated for micro-electro-mechanical systems (MEMS). Wurtzite ZnO structure was prepared on different substrates (Si (1 0 0), Pt (1 1 1)/Ti/SiO2/Si and Al (1 1 1)/SiO2/Si) at different substrate temperatures (from 100 to 500 °C) by a pulsed laser deposition (PLD) technique. X-ray diffraction (XRD) characterization showed that the ZnO films were highly c-axis (0 0 2) oriented, which is of interest for various piezoelectric applications. Scanning electron microscopy (SEM) showed evidence of honeycomb-like structure on the surface and columnar structure on the cross-section. In the case of ZnO on Al, ZnO exhibited an amorphous phase at the ZnO/Al interface. The XRD measurements indicated that the substrate temperature of 300 °C was the optimum condition to obtain high quality (strongest (0 0 2) peak with the biggest associated grain size) of crystalline ZnO on Pt and on Al and that 400 °C was the optimum one on Si. ZnO on Al exhibits smallest rocking curve width than on Pt, leading to better crystalline quality. The ZnO films were used in bulk acoustic wave (BAW) transducer. Electrical measurements of the input impedance and S-Parameters showed evidence of piezoelectric response. The electromechanical coupling coefficient was evaluated as Keff2=5.09%, with a quality factor Qr = 1001.4.

  12. Photocatalytic efficiency of reusable ZnO thin films deposited by sputtering technique

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Decolorization of Orange G dye using highly c-axis-oriented ZnO thin films. • The flake-shaped film shows superior and stable photoactivity at a wide range of pH. • The highest photodecolorization was achieved at pH of 7. • The exposure of (101) and (100) facets enhanced the photoactivity. • ZnO thin films exhibit a promising performance as recyclable photocatalysts. - Abstract: The photocatalytic activity of ZnO thin films with different physicochemical characteristics deposited by RF magnetron sputtering on glass substrate was tested for the decolorization of orange G dye aqueous solution (OG). The crystalline phase, surface morphology, surface roughness and the optical properties of these ZnO films were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM) and UV–visible spectroscopy (UV–Vis), respectively. The dye photodecolorization process was studied at acid, neutral and basic pH media under UV irradiation of 365 nm. Results showed that ZnO films grow with an orientation along the c-axis of the substrate and exhibit a wurtzite crystal structure with a (002) preferential crystalline orientation. A clear relationship between surface morphology and photocatalytic activity was observed for ZnO films. Additionally, the recycling photocatalytic abilities of the films were also evaluated. A promising photocatalytic performance has been found with a very low variation of the decolorization degree after five consecutive cycles at a wide range of pH media

  13. Photocatalytic efficiency of reusable ZnO thin films deposited by sputtering technique

    Energy Technology Data Exchange (ETDEWEB)

    Ahumada-Lazo, R.; Torres-Martínez, L.M. [Universidad Autónoma de Nuevo León, Facultad de Ingeniería Civil, Departamento de Ecomateriales y Energía, Av. Universidad S/N Ciudad Universitaria, San Nicolás de los Garza, Nuevo León C.P. 66450, México (Mexico); Ruíz-Gómez, M.A. [Universidad Autónoma de Nuevo León, Facultad de Ingeniería Civil, Departamento de Ecomateriales y Energía, Av. Universidad S/N Ciudad Universitaria, San Nicolás de los Garza, Nuevo León C.P. 66450, México (Mexico); Departmento de Física Aplicada, CINVESTAV-IPN, Antigua Carretera a Progreso km 6, Mérida, Yucatán 97310, México (Mexico); Vega-Becerra, O.E. [Centro de Investigación en Materiales Avanzados S.C, Alianza norte 202, Parque de Investigación e Innovación Tecnológica, C.P. 66600 Apodaca Nuevo León, México (Mexico); and others

    2014-12-15

    Graphical abstract: - Highlights: • Decolorization of Orange G dye using highly c-axis-oriented ZnO thin films. • The flake-shaped film shows superior and stable photoactivity at a wide range of pH. • The highest photodecolorization was achieved at pH of 7. • The exposure of (101) and (100) facets enhanced the photoactivity. • ZnO thin films exhibit a promising performance as recyclable photocatalysts. - Abstract: The photocatalytic activity of ZnO thin films with different physicochemical characteristics deposited by RF magnetron sputtering on glass substrate was tested for the decolorization of orange G dye aqueous solution (OG). The crystalline phase, surface morphology, surface roughness and the optical properties of these ZnO films were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM) and UV–visible spectroscopy (UV–Vis), respectively. The dye photodecolorization process was studied at acid, neutral and basic pH media under UV irradiation of 365 nm. Results showed that ZnO films grow with an orientation along the c-axis of the substrate and exhibit a wurtzite crystal structure with a (002) preferential crystalline orientation. A clear relationship between surface morphology and photocatalytic activity was observed for ZnO films. Additionally, the recycling photocatalytic abilities of the films were also evaluated. A promising photocatalytic performance has been found with a very low variation of the decolorization degree after five consecutive cycles at a wide range of pH media.

  14. Second harmonic generation in ZnO thin films fabricated by metalorganic chemical vapor deposition

    Science.gov (United States)

    Liu, C. Y.; Zhang, B. P.; Binh, N. T.; Segawa, Y.

    2004-07-01

    Second harmonic generation (SHG) from ZnO thin films fabricated by metalorganic chemical vapor deposition (MOCVD) technique was carried out. By comparing the second harmonic signal generated in a series of ZnO films with different deposition temperatures, we conclude that a significant part of second harmonic signal is generated at the film deposited with appropriate temperature. The second-order susceptibility tensor χ(2)zzz=9.2 pm/V was deduced for a film deposited at 250 °C.

  15. Room temperature ferromagnetism of Ni, (Ni, Li), (Ni, N)-doped ZnO thin films

    Institute of Scientific and Technical Information of China (English)

    AU; ChakTong

    2010-01-01

    Ni-doped ZnO thin films (Ni concentration up to 10 mol%) were generated on Si (100) substrates by a sol-gel technique. The films showed wurtzite structure and no other phase was found. The chemical state of Ni was found to be bivalent by X-ray photoelectron spectroscopy. The results of magnetic measurements at room temperature indicated that the films were ferromagnetic, and magnetic moment decreased with rise of Ni concentration. The magnetization of Ni (10 mol%)-doped ZnO film annealed in nitrogen was lower than that annealed in argon, suggesting that the density of defects had an effect on ferromagnetism.

  16. Selective Purcell enhancement of defect emission in ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Haglund, Jr, Richard F [ORNL

    2012-01-01

    A zinc interstitial defect present but unobservable in ZnO thin films annealed at 500 C in oxygen or in atmosphere was selectively detected by interaction of the film with an Ag surface-plasmon polariton. The time-dependent differential reflectivity of the ZnO near the ZnO/MgO interface exhibited a subpicosecond decay followed by a several nanosecond recovery, consistent with the Purcell-enhanced Zn interstitial luminescence seen in Ag-ZnO heterostructures. Heterostructures annealed at other temperatures showed significantly greater band-edge photoluminescence and no evidence of the Zn interstitial defect.

  17. Investigation of sol-gel yttrium doped ZnO thin films: structural and optical properties

    Science.gov (United States)

    Ivanova, T.; Harizanova, A.; Koutzarova, T.; Vertruyen, B.

    2016-02-01

    Nanostructured metal oxide films are extensively studied due to their numerous applications such as optoelectronic devices, sensors. In this work, we report the Y-Zn-O nanostructured films prepared by sol-gel technology from sols with different concentration of yttrium precursor, followed by post-annealing treatment. The Y doped ZnO thin films have been deposited on Si and quartz substrates by spin coating method, then treated at temperatures ranging from 300-800oC. XRD analysis reveals modification of the film structure and phases in the doped ZnO films.

  18. Plasmonic assisted enhanced photoresponse of metal nanoparticle loaded ZnO thin film ultraviolet photodetectors

    International Nuclear Information System (INIS)

    An ultraviolet (UV) photodetector exhibiting enhanced response characteristics has been realized successfully after integrating various metal nanoparticles (NPs) such as silver (Ag), gold (Au) and platinum (Pt) with sol–gel derived ZnO thin film (NPs–ZnO). The metal NP based photodetector (Ag, Au, Pt-NPs–ZnO) exhibits a relatively high photoresponse in comparison to the bare ZnO based UV photodetector and gives a maximum value of about 4.27 × 103. The combined effect of the lowering of dark current due to the formation of a Schottky barrier at the interface of the metal NPs with the ZnO thin film and the photocurrent upon UV illumination due to the plasmonic effect of loaded NPs results in an enhanced photoresponse of the prepared metal NP–ZnO photodetector. The trapping of incident UV radiation mainly through the enhanced optical absorption by loaded metal NPs due to the plasmonic effect and subsequent coupling of harvesting photons into underlying optical modes of the surface of photoconducting ZnO thin films lead to a significant increase in photocurrent. The observed results provide an indication that the plasmonic assisted UV response of the novel metal NP–ZnO photodetector might provide a breakthrough for the development of next generation photodetectors. (paper)

  19. Growth and optical characteristics of high-quality ZnO thin films on graphene layers

    Directory of Open Access Journals (Sweden)

    Suk In Park

    2015-01-01

    Full Text Available We report the growth of high-quality, smooth, and flat ZnO thin films on graphene layers and their photoluminescence (PL characteristics. For the growth of high-quality ZnO thin films on graphene layers, ZnO nanowalls were grown using metal-organic vapor-phase epitaxy on oxygen-plasma treated graphene layers as an intermediate layer. PL measurements were conducted at low temperatures to examine strong near-band-edge emission peaks. The full-width-at-half-maximum value of the dominant PL emission peak was as narrow as 4 meV at T = 11 K, comparable to that of the best-quality films reported previously. Furthermore, the stimulated emission of ZnO thin films on the graphene layers was observed at the low excitation energy of 180 kW/cm2 at room temperature. Their structural and optical characteristics were investigated using X-ray diffraction, transmission electron microscopy, and PL spectroscopy.

  20. Growth and optical characteristics of high-quality ZnO thin films on graphene layers

    Energy Technology Data Exchange (ETDEWEB)

    Park, Suk In; Tchoe, Youngbin; Baek, Hyeonjun; Hyun, Jerome K.; Yi, Gyu-Chul, E-mail: njkim36@gmail.com, E-mail: gcyi@snu.ac.kr [Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul 151-747 (Korea, Republic of); Heo, Jaehyuk [Advanced Development Team, LED Business, Samsung Electronics Co., Ltd., San#24 Nongseo-Dong, Giheung-Gu, Yongin-City, Gyeonggi-Do 446–711 (Korea, Republic of); Jo, Janghyun; Kim, Miyoung [Department of Materials Science and Engineering, Seoul National University, Seoul 151–744 (Korea, Republic of); Kim, Nam-Jung, E-mail: njkim36@gmail.com, E-mail: gcyi@snu.ac.kr [Department of Physics and Chemistry, Korea Military Academy, Seoul (Korea, Republic of)

    2015-01-01

    We report the growth of high-quality, smooth, and flat ZnO thin films on graphene layers and their photoluminescence (PL) characteristics. For the growth of high-quality ZnO thin films on graphene layers, ZnO nanowalls were grown using metal-organic vapor-phase epitaxy on oxygen-plasma treated graphene layers as an intermediate layer. PL measurements were conducted at low temperatures to examine strong near-band-edge emission peaks. The full-width-at-half-maximum value of the dominant PL emission peak was as narrow as 4 meV at T = 11 K, comparable to that of the best-quality films reported previously. Furthermore, the stimulated emission of ZnO thin films on the graphene layers was observed at the low excitation energy of 180 kW/cm{sup 2} at room temperature. Their structural and optical characteristics were investigated using X-ray diffraction, transmission electron microscopy, and PL spectroscopy.

  1. Nanoscale heterogeniety and workfunction variations in ZnO thin films

    Science.gov (United States)

    Sharma, Anirudh; Untch, Maria; Quinton, Jamie S.; Berger, Rüdiger; Andersson, Gunther; Lewis, David A.

    2016-02-01

    Nano-roughened, sol-gel derived polycrystalline ZnO thin films prepared by a thermal ramping procedure were found to exhibit different work function values on a sub-micrometer scale. By Kelvin probe force microscopy (KPFM) two distinct nanoscale regions with work function differing by over 0.1 eV were detected which did not coincide with the nano-roughened surface topography. In contrast, a flat ZnO surface displayed a single, uniform distribution. Ultraviolet photoelectron spectroscopy (UPS) studies showed that the average workfunction across a flat ZnO surface was 3.7 eV while ZnO with a nano-roughened morphology had a lower workfunction of 3.4 eV with indications of electronic heterogeneity across the surface, supporting the KPFM results. Scanning Auger Nanoprobe measurements showed that the chemical composition was uniform across the surface in all samples, suggesting the work function heterogeneity was due to variations in crystallinity or crystal orientation on the surface of these thin films. Such heterogeneity in the electronic properties of materials in thin film devices can significantly influence the interfacial charge transport across materials.

  2. Studies on nonvolatile resistance memory switching in ZnO thin films

    Indian Academy of Sciences (India)

    L M Kukreja; A K Das; P Misra

    2009-06-01

    Six decades of research on ZnO has recently sprouted a new branch in the domain of resistive random access memories. Highly resistive and c-axis oriented ZnO thin films were grown by us using d.c. discharge assisted pulsed laser deposition on Pt/Ti/SiO2/Si substrates at room temperature. The resistive switching characteristics of these films were studied in the top-bottom configuration using current–voltage measurements at room temperature. Reliable and repeated switching of the resistance of ZnO thin films was obtained between two well defined states of high and low resistance with a narrow dispersion and small switching voltages. Resistance ratios of the high resistance state to low resistance state were found to be in the range of 2–5 orders of magnitude up to 20 test cycles. The conduction mechanism was found to be dominated by the Ohmic behaviour in low resistance states, while Poole–Frenkel emission was found to dominate in high resistance state. The achieved characteristics of the resistive switching in ZnO thin films seem to be promising for nonvolatile memory applications.

  3. Nanostructured hybrid ZnO thin films for energy conversion

    Directory of Open Access Journals (Sweden)

    Samantilleke Anura

    2011-01-01

    Full Text Available Abstract We report on hybrid films based on ZnO/organic dye prepared by electrodeposition using tetrasulfonated copper phthalocyanines (TS-CuPc and Eosin-Y (EoY. Both the morphology and porosity of hybrid ZnO films are highly dependent on the type of dyes used in the synthesis. High photosensitivity was observed for ZnO/EoY films, while a very weak photoresponse was obtained for ZnO/TS-CuPc films. Despite a higher absorption coefficient of TS-CuPc than EoY, in ZnO/EoY hybrid films, the excited photoelectrons between the EoY levels can be extracted through ZnO, and the porosity of ZnO/EoY can also be controlled.

  4. Preparation and characterization of nanostructured ZnO thin films for photoelectrochemical splitting of water

    Indian Academy of Sciences (India)

    Monika Gupta; Vidhika Sharma; Jaya Shrivastava; Anjana Solanki; A P Singh; V R Satsangi; S Dass; Rohit Shrivastav

    2009-02-01

    Nanostructured zinc oxide thin films (ZnO) were prepared on conducting glass support (SnO2: F overlayer) via sol–gel starting from colloidal solution of zinc acetate 2-hydrate in ethanol and 2-methoxy ethanol. Films were obtained by spin coating at 1500 rpm under room conditions (temperature, 28–35°C) and were subsequently sintered in air at three different temperatures (400, 500 and 600°C). The evolution of oxide coatings under thermal treatment was studied by glancing incidence X-ray diffraction and scanning electron microscopy. Average particle size, resistivity and bandgap energy were also determined. Photoelectrochemical properties of thin films and their suitability for splitting of water were investigated. Study suggests that thin films of ZnO, sintered at 600°C are better for photoconversion than the films sintered at 400 or 500°C. Plausible explanations have been provided.

  5. Enhanced optical band-gap of ZnO thin films by sol-gel technique

    Science.gov (United States)

    Raghu, P.; Naveen, C. S.; Shailaja, J.; Mahesh, H. M.

    2016-05-01

    Transparent ZnO thin films were prepared using different molar concentration (0.1 M, 0.2 M & 0.8 M) of zinc acetate on soda lime glass substrates by the sol-gel spin coating technique. The optical properties revealed that the transmittance found to decrease with increase in molar concentration. Absorption edge showed that the higher concentration film has increasingly red shifted. An increased band gap energy of the thin films was found to be direct allowed transition of ˜3.9 eV exhibiting their relevance for photovoltaic applications. The extinction coefficient analysis revealed maximum transmittance with negligible absorption coefficient in the respective wavelengths. The results of ZnO thin film prepared by sol-gel technique reveal its suitability for optoelectronics and as a window layer in solar cell applications.

  6. Pulsed laser deposited cobalt-doped ZnO thin film

    Science.gov (United States)

    Wang, Li; Su, Xue-qiong; Lu, Yi; Chen, Jiang-bo

    2013-09-01

    To realize the room-temperature ferromagnetism (RTFM) in diluted magnetic semiconductors (DMS), we prepared a series of Cobalt-doped ZnO thin films using pulsed laser deposition (PLD) at deposition temperatures 500°C under oxygen pressure from 2.5×10-4 Pa to 15 Pa. To elucidate the physical origin of RTFM, Co 2p spectra of cobalt-doped ZnO thin films was measured by X-ray photoelectron spectroscopy (XPS). The magnetic properties of films were measured by an alternating gradient magnetometer (AGM), and the electrical properties were detected by a Hall Effect instrument using the Van der Pauw method. XPS analysis shows that the Co2+ exists and Co clusters and elemental content change greatly in samples under various deposition oxygen pressures. Not only the valence state and elemental content but also the electrical and magnetic properties were changed. In the case of oxygen pressure 10 Pa, an improvement of saturation magnetic moment about one order of magnitude over other oxygen pressure experiments, and the film exhibits ferromagnetism with a curie temperature above room temperature. It was found that the value of carrier concentration in the Co-doped ZnO film under oxygen pressure 10Pa increases about one order of magnitude than the values of other samples under different oxygen pressure. Combining XPS with AGM measurements, we found that the ferromagnetic signals in cobalt-doped ZnO thin film deposited at 500 °C under oxygen pressure 10 Pa only appear with the detectable Co2+ spectra from incompletely oxidized Co metal or Co cluster. So oxygen pressure 10 Pa can be thought the best condition to obtain room-temperature dilute magnetic semiconductor about cobalt-doped ZnO thin films.

  7. Experiment and prediction on thermal conductivity of Al2O3/ZnO nano thin film interface structure

    Indian Academy of Sciences (India)

    Ping Yang; Liqiang Zhang; Haiying Yang; Dongjing Liu; Xialong Li

    2014-05-01

    We predict that there is a critical value of Al2O3/ZnO nano thin interface thickness based on two assumptions according to an interesting phenomenon, which the thermal conductivity (TC) trend of Al2O3/ZnO nano thin interface is consistent with that of relevant single nano thin interface when the nano thin interface thickness is > 300 nm; however, TC of Al2O3/ZnO nano thin interface is higher than that of relevant single nano thin interface when the thin films thickness is < 10 nm. This prediction may build a basis for the understanding of interface between two different oxide materials. It implies an idea for new generation of semiconductor devices manufacturing.

  8. Scintillation characteristic of In, Ga-doped ZnO thin films with different dopant concentrations

    International Nuclear Information System (INIS)

    The present study describes the first detailed evaluation of the rise and the decay time of scintillation phenomenon in In3+- and Ga3+-doped ZnO thin films with different dopant concentrations. In3+-(25, 55, and 141 ppm) and Ga3+-(33, 67, 333, and 1374 ppm) doped ZnO films were grown by the Liquid Phase Epitaxy (LPE) method. The characterization was performed using the pulse X-ray equipped streak camera system. Both the rise and the decay times were shortened considerably with increasing content of In3+ and Ga3+ in the films. However, the scintillation light yield under 241Am α-ray excitation reduced when concentration of In3+ and Ga3+ in the ZnO films was high. (author)

  9. Electrical characteristics of ZnO nanorods reinforced polymer nanocomposite thin films

    International Nuclear Information System (INIS)

    ZnO nanorods have been prepared by simple chemical method, which is used to fabricate organic bistable devices (OBDs). OBDs are fabricated by incorporating different weight percent (wt %) of chemically synthesized Zinc Oxide (ZnO) nanorods into polymethylmethacrylate (PMMA). Current-voltage (I-V) measurements of the spin coated ZnO+PMMA nanocomopsite thin film on indium tin oxide (ITO) coated glass substrate showed current hysteresis behaviour, which is an indication of memory effect. The samples exhibit two distinct resistance states, ON and OFF states, characterised by relatively low and high resistance of the OBDs, respectively. It is also observed that with change in ZnO dopant concentration the value of ON/OFF current changes. Higher ON/OFF current ratio is desired for practical applications. Current conduction mechanism of the devices has been explained invoking various existing models, and it has been found that the trapped-charge-limited conduction mechanism was dominant in our samples

  10. Role of Ni doping on transport properties of ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Dar, Tanveer Ahmad, E-mail: tanveerphysics@gmail.com; Agrawal, Arpana; Sen, Pratima [Laser Bhawan, School Of Physics, Devi Ahilaya University Takshashila Campus Khandwa Road Indore, Indore-452001 (India)

    2015-06-24

    Nickel doped (Ni=0.05) and undoped Zinc Oxide (ZnO) thin films have been prepared by Pulsed laser deposition (PLD) technique. The structural analysis of the films was done by X-ray diffraction (XRD) studies which reveal absence of any secondary phase in the prepared samples. UV transmission spectra show that Ni doping reduces the transparency of the films. X-ray Photoelectron spectroscopy (XPS) also shows the presence of metallic Ni along with +2 oxidation state in the sample. Low temperature magneto transport properties of the ZnO and NiZnO films are also discussed in view of Khosla fisher model. Ni doping in ZnO results in decrease in magnitude of negative MR.

  11. Electrical characteristics of ZnO nanorods reinforced polymer nanocomposite thin films

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharjee, Snigdha; Roy, Asim, E-mail: 28.asim@gmail.com [Department of Physics National Institute Technology Silchar Silchar-788010, Assam (India)

    2015-05-15

    ZnO nanorods have been prepared by simple chemical method, which is used to fabricate organic bistable devices (OBDs). OBDs are fabricated by incorporating different weight percent (wt %) of chemically synthesized Zinc Oxide (ZnO) nanorods into polymethylmethacrylate (PMMA). Current-voltage (I-V) measurements of the spin coated ZnO+PMMA nanocomopsite thin film on indium tin oxide (ITO) coated glass substrate showed current hysteresis behaviour, which is an indication of memory effect. The samples exhibit two distinct resistance states, ON and OFF states, characterised by relatively low and high resistance of the OBDs, respectively. It is also observed that with change in ZnO dopant concentration the value of ON/OFF current changes. Higher ON/OFF current ratio is desired for practical applications. Current conduction mechanism of the devices has been explained invoking various existing models, and it has been found that the trapped-charge-limited conduction mechanism was dominant in our samples.

  12. Influence of high-pressure hydrogen treatment on structural and electrical properties of ZnO thin films

    International Nuclear Information System (INIS)

    ZnO thin films were treated by high-pressure hydrogen (H2). Scanning electron microscope (SEM) images show that the surface morphology of ZnO films has been changed significantly by H2 treatment. X-ray diffraction patterns show that the Zn(OH)2 phases formed after H2 treatment. The X-ray photoelectron spectroscopy results indicate that H atoms were doped into the surface of ZnO by forming H-O-Zn bond. The phenomenon shows that it is easy to form O-H bond in ZnO rather than H interstitial atom under high-pressure hydrogen circumstance.

  13. Microfluidic pumps employing surface acoustic waves generated in ZnO thin films

    International Nuclear Information System (INIS)

    ZnO thin film based surface acoustic wave (SAW) devices have been utilized to fabricate microfluidic pumps. The SAW devices were fabricated on nanocrystalline ZnO piezoelectric thin films deposited on Si substrates using rf magnetron sputtering and use a Sezawa wave mode for effective droplet motion. The as-deposited ZnO surface is hydrophilic, with a water contact angle of ∼75 deg., which prevents droplet pumping. Therefore, the ZnO surface was coated using a self-assembled monolayer of octadecyltrichlorosilane which forms a hydrophobic surface with a water contact angle of ∼110 deg. Liquid droplets between 0.5 and 1 μl in volume were successfully pumped on the hydrophobic ZnO surface at velocities up to 1 cm s-1. Under acoustic pressure, the water droplet on an hydrophilic surface becomes deformed, and the asymmetry in the contact angle at the trailing and leading edges allow the force acting upon the droplet to be calculated. These forces, which increase with input voltage above a threshold level, are found to be in the range of ∼100 μN. A pulsed rf signal has also been used to demonstrate precision manipulation of the liquid droplets. Furthermore, a SAW device structure is demonstrated in which the ZnO piezoelectric only exists under the input and output transducers. This structure still permits pumping, while avoiding direct contact between the piezoelectric material and the fluid. This is of particular importance for biological laboratory-on-a-chip applications

  14. Effect of R.F. Power to the Structural Properties of ZnO Thin Films Deposited by Magnetron Sputtering

    International Nuclear Information System (INIS)

    The effect of RF power variation (100 watt∼400 watt ) on the zinc oxide (ZnO) thin films electrical, optical and structural properties were examined using current voltage (I-V) measurement, UV-Vis-NIR spectrophotometer, x-ray diffraction (XRD) and atomic force microscope (AFM). ZnO thin films were prepared at room temperature in pure argon atmosphere by a RF magnetron sputtering using ZnO target. The resistivity of thin film show the lowest at 300 watt. The absorption coefficient spectra obtained from UV-Vis-NIR spectrophotometer measurement show all films have low absorbance in visible and near infrared (IR) region but have high UV absorption properties using UV-VIS spectrophotometer (JASCO 670) . Highly oriented ZnO thin films [002] direction were obtained by using Rigaku Ultima IV. (author)

  15. Influence of annealing temperature on ZnO thin films grown by dual ion beam sputtering

    Indian Academy of Sciences (India)

    Sushil Kumar Pandey; Saurabh Kumar Pandey; Vishnu Awasthi; Ashish Kumar; Uday P Deshpande; Mukul Gupta; Shaibal Mukherjee

    2014-08-01

    We have investigated the influence of in situ annealing on the optical, electrical, structural and morphological properties of ZnO thin films prepared on -type Si(100) substrates by dual ion beam sputtering deposition (DIBSD) system. X-ray diffraction (XRD) measurements showed that all ZnO films have (002) preferred orientation. Full-width at half-maximum (FWHM) of XRD from the (002) crystal plane was observed to reach to a minimum value of 0.139° from ZnO film, annealed at 600 °C. Photoluminescence (PL) measurements demonstrated sharp near-band-edge emission (NBE) at ∼ 380 nm along with broad deep level emissions (DLEs) at room temperature. Moreover, when the annealing temperature was increased from 400 to 600 °C, the ratio of NBE peak intensity to DLE peak intensity initially increased, however, it reduced at further increase in annealing temperature. In electrical characterization as well, when annealing temperature was increased from 400 to 600 °C, room temperature electron mobility enhanced from 6.534 to 13.326 cm2/V s, and then reduced with subsequent increase in temperature. Therefore, 600 °C annealing temperature produced good-quality ZnO film, suitable for optoelectronic devices fabrication. X-ray photoelectron spectroscopy (XPS) study revealed the presence of oxygen interstitials and vacancies point defects in ZnO film annealed at 400 °C.

  16. Characteristics of laser-annealed ZnO thin film transistors

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jun-Je; Bak, Jun-Yong; Lee, Jong-Hoon [Department of Nano Semiconductor, Korea Maritime University, Busan 606-791 (Korea, Republic of); Kim, Hong Seung, E-mail: hongseung@hhu.ac.k [Department of Nano Semiconductor, Korea Maritime University, Busan 606-791 (Korea, Republic of); Jang, Nak-Won [Department of Electrical Engineering, Korea Maritime University, Busan 609-791 (Korea, Republic of); Yun, Young [Department of Radio Communication Engineering, Korea Maritime University, Busan 606-791 (Korea, Republic of); Lee, Won-Jae [Department of Nano Technology, Dong Eui University, Busan 614-714 (Korea, Republic of)

    2010-03-31

    We investigated the effects of laser annealing on ZnO thin film transistors (TFTs). ZnO layers were deposited on a bottom-gate patterned Si substrate by radio-frequency sputtering at room temperature. Laser annealing of the ZnO films reduced the full width at half maximum of the ZnO (002) diffraction peak from 0.49{sup o} to 0.1{sup o}. It reveals that the crystalline quality is improved by annealing effect. A SiO{sub 2} formed in low temperature was used as the gate dielectric. Unannealed ZnO-TFTs were operated in enhancement mode with a threshold voltage of 21.6 V. They had a field-effect mobility of 0.004 cm{sup 2}/Vs and an on/off current ratio of 134. Laser annealing of the ZnO-TFTs by 200 laser pulses reduced their threshold voltage to 0.6 V and increased their field-effect mobility to 5.08 cm{sup 2}/Vs. The increase of mobility is originated from the crystallization enhancement of ZnO films after laser annealing.

  17. Quenching of surface traps in Mn doped ZnO thin films for enhanced optical transparency

    International Nuclear Information System (INIS)

    The structural and photoluminescence analyses were performed on un-doped and Mn doped ZnO thin films grown on Si (1 0 0) substrate by pulsed laser deposition (PLD) and annealed at different post-deposition temperatures (500-800 deg. C). X-ray diffraction (XRD), employed to study the structural properties, showed an improved crystallinity at elevated temperatures with a consistent decrease in the lattice parameter 'c'. The peak broadening in XRD spectra and the presence of Mn 2p3/2 peak at ∼640 eV in X-ray Photoelectron Spectroscopic (XPS) spectra of the doped thin films confirmed the successful incorporation of Mn in ZnO host matrix. Extended near band edge emission (NBE) spectra indicated the reduction in the concentration of the intrinsic surface traps in comparison to the doped ones resulting in improved optical transparency. Reduced deep level emission (DLE) spectra in doped thin films with declined PL ratio validated the quenching of the intrinsic surface traps thereby improving the optical transparency and the band gap, essential for optoelectronic and spintronic applications. Furthermore, the formation and uniform distribution of nano-sized grains with improved surface features of Mn-doped ZnO thin films were observed in Field Emission Scanning Electron Microscopy (FESEM) images.

  18. Polyelectrolyte-assisted preparation and characterization of nanostructured ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Shijun

    2005-05-15

    The present work focuses on the synthesis and characterization of nanostructured ZnO thin films onto silicon wafers modified by self-assembled-monolayers via chemical bath deposition. Two precursor solutions were designed and used for the film deposition, in which two different polymers were introduced respectively to control the growth of the ZnO colloidal particles in solution. ZnO films were deposited from an aqueous solution containing zinc salt and hexamethylenetetramine (HMTA) in the presence of a graft-copolymer (P (MAA{sub 0.50}-co(MAA-EO{sub 20}){sub 0.50}){sub 70}). A film-formation-diagram was established based on the results obtained by scanning electron microscopy (SEM) and atomic force microscopy (AFM), which describes the influence of the concentration of HMTA and copolymer on the ZnO film formation. According to the film morphology, film formation can be classified into three categories: (a) island-like films, (b) uniform films and (c) canyon-like films. The ZnO films annealed at temperatures of 450 C, 500 C, 600 C and 700 C were examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). After annealing, the films are polycrystalline ZnO with wurtzite structure. XRD measurements indicate that with increasing annealing temperature, the average grain size increases accordingly and the crystallinity of the films is improved. Upon heating to 600 C, the ZnO films exhibit preferred orientation with c-axis normal to substrate, whereas the films annealed at 700 C even show a more explicit texture. By annealing at temperatures above 600 C the ZnO film reacts with the substrate to form an interfacial layer of Zn{sub 2}SiO{sub 4}, which grows thicker at elevated annealing temperatures. The ZnO films annealed at 600 C and 700 C show strong UV emission. Another non-aqueous solution system for ZnO thin film deposition was established, in which 2- propanol was used as a solvent and Zn(CH3COO){sub 2}.2H{sub 2}O as well as NaOH as reactants

  19. MICROSTRUCTURE AND PROPERTIES OF ANNEALED ZnO THIN FILMS DEPOSITED BY MAGNETRON SPUTTERING

    Institute of Scientific and Technical Information of China (English)

    J. Lee; W. Gao; Z. Li; M. Hodgson; A. Asadov; J. Metson

    2005-01-01

    ZnO thin films were deposited on a glass substrate by dc (direct current) and rf (radio frequency) magnetron sputtering. Post-deposition annealing was performed in different atmospheres and at different temperatures. The correlation of the annealing conditions with the microstructure and properties of the ZnO films were investigated by ultraviolet-visible spectroscopy, X-ray diffraction, conductivity measurement and scanning electron microscopy. Only the strong 002peak could be observed by X-ray diffraction. The post-deposition annealing of ZnO films was found to alter the film's microstructure and properties, including crystallinity, porosity, grain size, internal stress level and resistivity. It was also found that after annealing, the conductivity of poorly conductive samples often improved. However, annealing does not improve the conductivity of samples with high conductivity prior to annealing. The resistivity of as-grown films annealing on the conductivity of ZnO, it is believed that annealing may alter the presence and distribution of oxygen defects, reduce the lattice stress, cause diffusion, grain coarsening and recrystallization. Annealing will reduce the density of grain boundaries in less dense films,which may decrease the resistivity of the films. On the other hand, annealing may also increase the porosity of thin films, leading to an increase in resistivity.

  20. Effect of substrate temperature on structural and optical properties of spray deposited ZnO thin films

    Directory of Open Access Journals (Sweden)

    Larbah Y.

    2015-09-01

    Full Text Available Undoped ZnO thin films have been prepared on glass substrates at different substrate temperatures by spray pyrolysis method. The effect of temperature on the structural, morphological and optical properties of n-type ZnO films was studied. The X-ray diffraction (XRD results confirmed that the ZnO thin films were polycrystalline with wurtzite structure. Scanning electron microscopy (SEM measurements showed that the surface morphology of the films changed with temperature. The studies demonstrated that the ZnO film had a transmission of about 85 % and energy gap of 3.28 eV at 450 °C. The RBS measurements revealed that ZnO layers with a thickness up to 200 nm had a good stoichiometry.

  1. Recent advances in the transparent conducting ZnO for thin-film Si solar cells

    Science.gov (United States)

    Moon, Taeho; Shin, Gwang Su; Park, Byungwoo

    2015-11-01

    The key challenge for solar-cell development lies in the improvement of power-conversion efficiency and the reduction of fabrication cost. For thin-film Si solar cells, researches have been especially focused on the light trapping for the breakthrough in the saturated efficiencies. The ZnO-based transparent conducting oxides (TCOs) have therefore received strong attention because of their excellent light-scattering capability by the texture-etched surface and cost effectiveness through in-house fabrication. Here, we have highlighted our recent studies on the transparent conducting ZnO for thin-film Si solar cells. From the electrical properties and their degradation mechanisms, bilayer deposition and organic-acid texturing approaches for enhancing the light trapping, and finally the relation between textured ZnO and electrical cell performances are sequentially introduced in this review article. [Figure not available: see fulltext.

  2. Comparative study of ZnO thin films prepared by different sol-gel route

    Directory of Open Access Journals (Sweden)

    F Esmaieli Ghodsi

    2012-03-01

    Full Text Available   Retraction Notice    The paper "Comparative study of ZnO thin films prepared by different sol-gel route" by H. Absalan and F. E. Ghodsi, which appeared in Iranian Journal of Physics Research, Vol. 11, No. 4, 423-428 (in Farsi is translation of the paper "Comparative Study of ZnO Thin Films Prepared by Different Sol-Gel Route" by F. E. Ghodsi and H. Absalan, which appeared in ACTA PHYSICA POLONICA A, Vol 118 (2010 (in English and for this reason is retracted from this journal.The corresponding author  (and also the first author is the only responsible person for this action.   

  3. Identification of Parameters influencing in the Growth of Thin Layers ZnO Using MOCVD Method

    International Nuclear Information System (INIS)

    The identification of growth parameters of zinc oxide thin films has been studied. From the analysis of effect growth rate on the total pressure, it was found that the growth rate increased exponentially with total pressure. It was also found that higher activation energy was reached at mass composition of DEZ and H2O of 20 sccm and 40 sccm, respectively. Effect of precursor rate with nozzle distance from substrate on the peak intensity ratio ((110)/(002)) and ((100)/(002) was studied. It was found that the reflection peak intensity changes from (002) to (110). The lower sheet resistivity of 3.42 ohm/sqr at 4.47 μm thick film. This result indicated that the growth parameters of ZnO thin films should be knew to order to grow ZnO films with good quality and low resistivity. (author)

  4. The Electrical Properties of Co-Doped ZnO Thin Films

    International Nuclear Information System (INIS)

    Codoped ZnO thin films were prepared on silicon (111) substrates by cosputtering of aluminium rods and zinc target using DC magnetron sputtering followed by heat treatment at 400 deg. C for 1 hour at different ratios of oxygen and nitrogen gas. Results indicate that gas ratios influenced the film conduction properties, which had the lowest resistivity of 7.985x10-3 cm-3 and highest carrier concentration of 6.89x1021 cm-3.

  5. Carrier dynamics and gain spectra at room-temperature in epitaxial ZNO thin films

    DEFF Research Database (Denmark)

    Yu, Ping; Hvam, Jørn Märcher; Wong, K. S.;

    1999-01-01

    Carrier dynamics of epitaxial ZnO thin film was investigated using a frequency up-conversion tehcnique. At lower carrier densities, the decay time of free exciton recombination was measured to be 24 ps. Rapid decay times of a few picoseconds were observed at higher carrier densities, which show a...... transition of two dynamic processes. The comparison of calculated gain spectrum and experimental data gave evidence that the transition is form exciton-exciton scattering to the recombination of electron hole plasma....

  6. Improved sensing response of photo activated ZnO thin film for hydrogen peroxide detection.

    Science.gov (United States)

    Parthasarathy, S; Nandhini, V; Jeyaprakash, B G

    2016-11-15

    The nanostructured ZnO thin films were deposited using spray pyrolysis technique. Formation of polycrystalinity with hexagonal wurtzite structure was observed from the structural study. Highly dense spherical shaped nanoparticles with fine crystallites were observed from the surface morphological studies. The light induced hydrogen peroxide vapour sensing was done using chemi-resistive method and its effect on the sensing response was studied and reported. PMID:27491004

  7. Photoelectrochemical characterization of dye-modified ZnO hybrid thin films prepared by electrochemical deposition

    OpenAIRE

    Nonomura, Kazuteru

    2006-01-01

    Dye-sensitized electrodeposited ZnO thin films were studied in their photoelectrochemical characteristics. Such electrodes can be applied for dye-sensitized solar cells. The main analysis techniques were wavelength- dependent photocurrent measurements to obtain the incident photon to current conversion efficiency (IPCE) of the films as well as time- and frequency- resolved measurements of the photocurrent (IMPS) and photovoltage (IMVS) to characterize in detail individual steps of photoelectr...

  8. Pump-probe measurement of ZnO epitaxial thin films

    CERN Document Server

    Yamamoto, A; Goto, T; Chen, Y; Yao, T; Kasuya, A

    1999-01-01

    Time-resolved optical absorption spectra of ZnO epitaxial thin films have been measured by using a pump-probe technique with subpicosecond time resolution. We have observed following three structures in the differential absorption spectra: saturation of the exciton absorption, bandgap renormalization and optical gain. The optical gain is thought to be due to electron-hole plasma. From the temporal changes of these structures, the dynamical properties of the photo-excited carriers are discussed.

  9. Photovoltaic performance of Gallium-doped ZnO thin film/Si nanowires heterojunction diodes

    Science.gov (United States)

    Akgul, Guvenc; Aksoy Akgul, Funda; Emrah Unalan, Husnu; Turan, Rasit

    2016-04-01

    In this work, photovoltaic performance of Ga-doped ZnO thin film/Si NWs heterojunction diodes was investigated. Highly dense and vertically well-aligned Si NW arrays were successfully synthesised on a p-type (1 0 0)-oriented Si wafer through cost-effective metal-assisted chemical etching technique. Ga-doped ZnO thin films were deposited onto Si NWs via radio frequency magnetron sputtering to construct three-dimensional heterostructures. Photovoltaic characteristics of the fabricated diodes were determined with current density (J)-voltage (V) measurements under simulated solar irradiation of AM 1.5 G. The optimal open-circuit voltage, short-circuit current density, fill factor and power conversion efficiency were found to be 0.37 V, 3.30 mA cm-2, 39.00 and 0.62%, respectively. Moreover, photovoltaic diodes exhibited relatively high external quantum efficiency over the broadband wavelengths between 350 and 1100 nm interval of the spectrum. The observed photovoltaic performance in this study clearly indicates that the investigated device structure composed of Ga-doped ZnO thin film/Si NWs heterojunctions could facilitate an alternative pathway for optoelectronic applications in future, and be a promising alternative candidate for high-performance low-cost new-generation photovoltaic diodes.

  10. Structural, morphological, optical and opto-thermal properties of Ni-doped ZnO thin films using spray pyrolysis chemical technique

    Indian Academy of Sciences (India)

    S Rajeh; A Barhoumi; A Mhamdi; G Leroy; B Duponchel; M Amlouk; S Guermazi

    2016-02-01

    Nickel-doped zinc oxide thin films (ZnO : Ni) at different percentages were deposited on glass substrates using a chemical spray technique. The effect of Ni concentration on the structural, morphological, optical and photoluminescence (PL) properties of the ZnO : Ni thin films were investigated. X-ray diffraction analysis revealed that all films consist of single phase ZnO and was well crystallized in würtzite phase with the crystallites preferentially oriented towards the (002) direction parallel to the c-axis. The optical transmittance measurement was found to be higher than 90%, the optical band gap values of ZnO thin films decreased after doping from 3.29 to 3.21 eV. A noticeable change in optical constants was observed between undoped and Ni-doped ZnO. Room-temperature PL is observed for ZnO, and Ni-doped ZnO thin films.

  11. Optical and electrical studies of ZnO thin films heavily implanted with silver ions

    International Nuclear Information System (INIS)

    Thin films of zinc oxide (ZnO) with the thickness of 200 nm have been deposited on quartz substrates by using ion-beam sputtering technique. Then Ag+ ions with the energy of 30 keV have been implanted into as-deposited ZnO films to the fluences in the range of (0.25-1.00)×1017 ions/cm2 to form ZnO:Ag composite layers with different concentrations of the silver impurity. The analysis of the microstructure has shown that the thickness of the ZnO film decreases, and the Ag dopant concentration tends to the saturation with increasing Ag implantation fluence. The ZnO:Ag composite layers reveal the optical selective absorption at the wavelength of the surface plasmon resonance that is typical for silver nanoparticles dispersed in the ZnO matrix. The red shift of the plasmon resonance peak from 480 to 500 nm is observed with the increase in the implantation fluence to 0.75×1017 Ag ions/cm2. Then the absorption peak position starts the backward motion, and the absorption intensity decreases with the subsequent increase in the implantation fluence. The non-monotonic dependence of the absorption peak position on the implantation fluence has been analyzed within of Maxwell Garnet theory and taking into account the strong sputtering of ZnO films during implantation. The ZnO:Ag composite layers exhibit the p-type conductivity indicating that a part of Ag+ ions is in the form of acceptor impurities implanted into the ZnO lattice

  12. Growth of b-axis oriented VO2 thin films on glass substrates using ZnO buffer layer

    International Nuclear Information System (INIS)

    VO2 thin films are grown on glass substrates by pulsed laser deposition using vanadium metal as a target. In this study, a ZnO thin film was used as a buffer layer for the growth of VO2 thin films on glass substrates. X-ray diffraction studies showed that the VO2 thin film had b-axis preferential orientation on a c-axis oriented ZnO buffer layer. The thickness of the ZnO buffer layer and the oxygen pressure during VO2 deposition were optimized to grow highly b-axis oriented VO2 thin films. The metal-insulator transition properties of the VO2 film samples were investigated in terms of infrared reflectance and electrical resistance with varying temperatures.

  13. Optical and electrical characterization of aluminium doped ZnO layers

    International Nuclear Information System (INIS)

    Al doped ZnO (ZAO) thin films (with Al-doping levels 2 at.%) were deposited at different deposition parameters on silicon substrate by reactive magnetron sputtering for solar cell contacts, and samples were investigated by transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS) and spectroscopic ellipsometry (SE). Specific resistances were measured by the well known 4-pin method. Well visible columnar structure and in most cases voided other regions were observed at the grain boundaries by TEM. EELS measurements were carried out to characterize the grain boundaries, and the results show spacing voids between columnar grains at samples with high specific resistance, while no spacing voids were observed at highly conductive samples. SE measurements were evaluated by using the analytical expression suggested by Yoshikawa and Adachi [H. Yoshikawa, S. Adachi, Japanese Journal of Applied Physics 36 (1997) 6237], and the results show correlation between specific resistance and band gap energy and direct exciton strength parameter.

  14. P-Type Conduction of ZnO Thin Film by Codoping Technique

    International Nuclear Information System (INIS)

    Aluminium and zinc target were co-sputtered on silicon (111) substrates using DC magnetron sputtering in the pure argon atmosphere. These films were then underwent the thermal annealing in different ratios of nitrogen and oxygen for 1 hour to form thin oxide films. P-type conduction in ZnO thin films have been realized by the Al-N codoping method, whereby the lowest resistivity of 3.41x10-3 Ω·cm and the highest carrier concentration of 1.54x1022 cm-3 was achieved for sample prepared at annealed temperature of 300 deg. C

  15. Defect-band mediated ferromagnetism in Gd-doped ZnO thin films

    KAUST Repository

    Venkatesh, S.

    2015-01-07

    Gd-doped ZnO thin films prepared by pulsed laser deposition with Gd concentrations varying from 0.02–0.45 atomic percent (at. %) showed deposition oxygen pressure controlled ferromagnetism. Thin films prepared with Gd dopant levels (

  16. Fabrication and Characterization of High-Crystalline Nanoporous ZnO Thin Films by Modified Thermal Evaporation System

    Science.gov (United States)

    Islam, M. S.; Hossain, M. F.; Razzak, S. M. A.; Haque, M. M.; Saha, D. K.

    2016-05-01

    The aim of this work is to fabricate high-crystalline nanoporous zinc oxide (ZnO) thin films by a modified thermal evaporation system. First, zinc thin films have been deposited on bare glass substrate by the modified thermal evaporation system with pressure of 0.05mbar, source-substrate distance of 3cm and source temperature 700∘C. Then, high-crystalline ZnO thin film is obtained by annealing at 500∘C for 2h in atmosphere. The prepared ZnO films are characterized with various deposition times of 10min and 20min. The structural property was investigated by X-ray diffractometer (XRD). The optical bandgap and absorbance/transmittance of these films are examined by ultraviolet/visible spectrophotometer. The surface morphological property has been observed by scanning electron microscope (SEM). ZnO films have showed uniform nanoporous surface with high-crystalline hexagonal wurtzite structure. The ZnO films prepared with 20min has excitation absorption-edge at 369nm, which is blueshifted with respect to the bulk absorption-edge appearing at 380nm. The gap energy of ZnO film is decreased from 3.14eV to 3.09eV with increase of the deposition time, which can enhance the excitation of ZnO films by the near visible light, and is suitable for the application of photocatalyst of waste water cleaning and polluted air purification.

  17. Effect of ZnO Addition on Structural Properties of ZnO-PANi/ Carbon Black Thin Films

    International Nuclear Information System (INIS)

    The aim of this project was to investigate the effect of ZnO addition on the structural properties of ZnO-PANi/ carbon black thin films. The sol gel method was employed for the preparation of ZnO sol. The sol was dried for 24 h at 100 degree Celsius and then annealed at 600 degree Celsius for 5 h. XRD characterization of the ZnO powder showed the formation of wurtzite type ZnO crystals. The ZnO powder were mixed into PANi/ carbon black solution which was dissolved into M-Pyrol, N-Methyl-2-Pyrrolidinone (NMP) to produce a composite solution of ZnO-PANi/ carbon black. The weight ratio of ZnO were 4 wt %, 6 wt % and 8 wt %. The composite solutions were deposited onto glass substrates using a spin-coating technique to fabricate ZnO-PANi/ carbon black thin films. AFM characterization showed the decreasing of average roughness from 7.98 nm to 2.23 nm with the increment of ZnO addition in PANi/ carbon black films. The thickness of the films also decreased from 59.5 nm to 28.3 nm. FESEM image revealed that ZnO-PANi/ carbon black thin films have changed into agglomerated surface morphology resulting in the increment of porosity of the films. (author)

  18. Electrode loading effect and high temperature performance of ZnO thin film ultrasonic transducers

    Science.gov (United States)

    Zhou, X. S.; Zhang, J.; Hou, R.; Zhao, C.; Kirk, K. J.; Hutson, D.; Hu, P. A.; Peng, S. M.; Zu, X. T.; Fu, Y. Q.

    2014-10-01

    Nanocrystalline ZnO films of 5.8 μm thick were sputter-deposited on ferritic carbon steel plates (25 × 25 × 3 mm3) and characterized for use as ultrasonic transducers at both room temperature and high temperatures. Electrode loading effects have been studied using two types of electrodes, i.e., sputtered Cr/Au (5/50 nm) and silver paste, with electrode diameters 0.7-2.5 mm. Longitudinal and transverse waves were obtained in pulse-echo tests using both types of electrodes. With a silver paste top electrode, a dominant longitudinal mode was obtained, but with a thin Cr/Au film as the top electrode, shear waves were more dominant. Pulse-echo tests of the ZnO transducers were also performed at elevated temperatures up to 450 °C using a carbon paste electrodes. The sputtered ZnO films maintained a stable crystalline structure and orientation at the elevated temperatures, and ZnO devices on ferritic carbon steel could be used successfully up to 400 °C. However, when the temperature was increased further, rapid surface oxidation of the ferritic carbon steel caused the failure of the transducer.

  19. Plasma enhanced chemical vapor deposition of thin ZnO layers on glass substrates

    International Nuclear Information System (INIS)

    The plasma enhanced chemical vapor deposition (PECVD) is a powerful and flexible instrument for depositing thin layers, nanocomposites or nanostructures. In this work ZnO layers were grown by metal-organic PECVD (RF – 13.56 MHz) on glass substrates coated with ZnO seed films. Zn acetylacetonate was used as a precursor and oxygen as oxidant. The influence of the oxygen content in gas mixture on the morphology, optical and electrical properties of the deposited layers was studied. ZnO film properties were investigated by scanning electron microscopy (SEM), UV-VIS optical spectrophotometry and current-voltage (I-V) measurements. The results obtained show that the oxygen content in the deposition atmosphere influences the morphology, the optical properties and the electrical resistivity of the obtained ZnO layers. Nanorods with good alignment, vertically orientated to the surface of glass substrate can be observed in the layers deposited at low content of O2 in plasma at substrate temperature of 400°C

  20. Engineering the switching dynamics of TiOx-based RRAM with Al doping

    Science.gov (United States)

    Trapatseli, Maria; Khiat, Ali; Cortese, Simone; Serb, Alexantrou; Carta, Daniela; Prodromakis, Themistoklis

    2016-07-01

    Titanium oxide (TiOx) has attracted a lot of attention as an active material for resistive random access memory (RRAM), due to its versatility and variety of possible crystal phases. Although existing RRAM materials have demonstrated impressive characteristics, like ultra-fast switching and high cycling endurance, this technology still encounters challenges like low yields, large variability of switching characteristics, and ultimately device failure. Electroforming has been often considered responsible for introducing irreversible damage to devices, with high switching voltages contributing to device degradation. In this paper, we have employed Al doping for tuning the resistive switching characteristics of titanium oxide RRAM. The resistive switching threshold voltages of undoped and Al-doped TiOx thin films were first assessed by conductive atomic force microscopy. The thin films were then transferred in RRAM devices and tested with voltage pulse sweeping, demonstrating that the Al-doped devices could on average form at lower potentials compared to the undoped ones and could support both analog and binary switching at potentials as low as 0.9 V. This work demonstrates a potential pathway for implementing low-power RRAM systems.

  1. Bias-voltage dependent ultraviolet photodetectors prepared by GaOx + ZnO mixture phase nanocrystalline thin films

    International Nuclear Information System (INIS)

    Highlights: •GaOx + ZnO thin films sputtered and annealed exhibit interesting and unique optical properties, especially deep UV photo response. •GaOx + ZnO thin films can be used to fabricate efficient deep UV photodetectors. •The mixture phase nature of GaOx + ZnO thin films is revealed to be responsible for the unique characteristics of the photodetectors. •Two bands in UV range can be adjusted by a applied voltage when the PDs were fabricated using the mixture phase nature of GaOx + ZnO thin films. -- Abstract: Ultraviolet (UV) photodetectors were prepared by using the GaOx + ZnO mixture phase thin films sputtered on sapphire as the photoresponse layer. The devices show good photoresponse in UV range. More interestingly, the device responsivity in the wavelength less than 280 nm range rapidly increases with increasing the applied voltage and becomes dominant for the bias ⩾3.0 V. X-ray diffraction, absorption and cathodoluminescence measurements firmly reveal the mixture phases in the thin films. Electric field dependent detrapping of photo-excited carriers in nanocrystals in the films shall be responsible for the observed bias-voltage dependent deep UV photoresponse of the devices

  2. Photoelectrochemical properties of highly mobilized Li-doped ZnO thin films.

    Science.gov (United States)

    Shinde, S S; Bhosale, C H; Rajpure, K Y

    2013-03-01

    Li-doped ZnO thin films with preferred (002) orientation have been prepared by spray pyrolysis technique in aqueous medium on to the corning glass substrates. The effect of Li-doping on to the photoelectrochemical, structural, morphological, optical, luminescence, electrical and thermal properties has been investigated. XRD and Raman study indicates that the films have hexagonal crystal structure. The transmittance, reflectance, refractive index, extinction coefficient and bandgap have been analyzed by optical study. PL spectra consist of a near band edge and visible emission due to the electronic defects, which are related to deep level emissions, such as oxide antisite (OZn), interstitial zinc (Zni), interstitial oxygen (Oi) and zinc vacancy (VZn). The Li-doped ZnO films prepared for 1at% doping possesses the highest electron mobility of 102cm(2)/Vs and carrier concentration of 3.62×10(19)cm(-3). Finally, degradation of 2,4,6-Trinitrotoluene using Li-doped ZnO thin films has been reported. PMID:23416707

  3. Photoluminescence properties of ZnO thin films prepared by DC magnetron sputtering

    Institute of Scientific and Technical Information of China (English)

    YANG Bing-chu; LIU Xiao-yan; GAO Fei; MA Xue-long

    2008-01-01

    ZnO thin films were prepared by direct current(DC) reactive magnetron sputtering under different oxygen partial pressures.And then the samples were annealed in vacuum at 450 ℃. The effects of the oxygen partial pressures and the treatment of annealing in vacuum on the photoluminescence and the concentration of six intrinsic defects in ZnO thin films such as oxygen vacancy(Vo),zinc vacancy(VZn), antisite oxygen(OZn), antisite zinc(ZnO), interstitial oxygen(Oi) and interstitial zinc(Zni) were studied. The results show that a green photoluminescence peak at 520 nm can be observed in all the samples, whose intensity increases with increasing oxygen partial pressure; for the sample annealed in vacuum, the intensity of the green peak increases as well. The green photoluminescence peak observed in ZnO may be attributed to zinc vacancy, which probably originates from transitions between electrons in the conduction band and zinc vacancy levels, or from transitions between electrons in zinc vacancy levels and up valence band.

  4. Flexible pH sensors based on polysilicon thin film transistors and ZnO nanowalls

    Science.gov (United States)

    Maiolo, L.; Mirabella, S.; Maita, F.; Alberti, A.; Minotti, A.; Strano, V.; Pecora, A.; Shacham-Diamand, Y.; Fortunato, G.

    2014-09-01

    A fully flexible pH sensor using nanoporous ZnO on extended gate thin film transistor (EGTFT) fabricated on polymeric substrate is demonstrated. The sensor adopts the Low Temperature Polycrystalline Silicon (LTPS) TFT technology for the active device, since it allows excellent electrical characteristics and good stability and opens the way towards the possibility of exploiting CMOS architectures in the future. The nanoporous ZnO sensitive film, consisting of very thin (20 nm) crystalline ZnO walls with a large surface-to-volume ratio, was chemically deposited at 90 °C, allowing simple process integration with conventional TFT micro-fabrication processes compatible with wide range of polymeric substrates. The pH sensor showed a near-ideal Nernstian response (˜59 mV/pH), indicating an ideality factor α ˜ 1 according to the conventional site binding model. The present results can pave the way to advanced flexible sensing systems, where sensors and local signal conditioning circuits will be integrated on the same flexible substrate.

  5. Laser molecular beam epitaxy of ZnO thin films and heterostructures

    International Nuclear Information System (INIS)

    We report on the growth of epitaxial ZnO thin films and ZnO-based heterostructures on sapphire substrates by laser molecular beam epitaxy (MBE). We first discuss some recent developments in laser-MBE such as flexible ultraviolet laser beam optics, infrared laser heating systems or the use of atomic oxygen and nitrogen sources, and describe the technical realization of our advanced laser-MBE system. Then we describe the optimization of the deposition parameters for ZnO films such as laser fluence and substrate temperature and the use of buffer layers. The detailed structural characterization by x-ray analysis and transmission electron microscopy shows that epitaxial ZnO thin films with high structural quality can be achieved, as demonstrated by a small out-of-plane and in-plane mosaic spread as well as the absence of rotational domains. We also demonstrate the heteroepitaxial growth of ZnO-based multilayers as a prerequisite for spin transport experiments and the realization of spintronic devices. As an example, we show that TiN/Co/ZnO/Ni/Au multilayer stacks can be grown on (0 0 0 1)-oriented sapphire with good structural quality of all layers and well defined in-plane epitaxial relations. (paper)

  6. Preparation of manganese-doped ZnO thin films and their characterization

    Indian Academy of Sciences (India)

    S Mondal; S R Bhattacharyya; P Mitra

    2013-04-01

    In this study, pure and manganese-doped zinc oxide (Mn:ZnO) thin films were deposited on quartz substrate following successive ion layer adsorption and reaction (SILAR) technique. The film growth rate was found to increase linearly with number of dipping cycle. Characterization techniques of XRD, SEM with EDX and UV–visible spectra measurement were done to investigate the effect of Mn doping on the structural and optical properties of Mn:ZnO thin films. Structural characterization by X-ray diffraction reveals that polycrystalline nature of the films increases with increasing manganese incorporation. Particle size evaluated using X-ray line broadening analysis shows decreasing trend with increasing manganese impurification. The average particle size for pure ZnO is 29.71nm and it reduces to 23.76nm for 5%Mn-doped ZnO. The strong preferred c-axis orientation is lost due to manganese (Mn) doping. The degree of polycrystallinity increases and the average microstrain in the films decreases with increasing Mn incorporation. Incorporation of Mn was confirmed from elemental analysis using EDX. As the Mn doping concentration increases the optical bandgap of the films decreases for the range of Mn doping reported here. The value of fundamental absorption edge is 3.22 eV for pure ZnO and it decreases to 3.06 eV for 5%Mn:ZnO.

  7. Synthesis and Characterization of Varying Concentrations of Ag-doped ZnO Thin Films

    Science.gov (United States)

    Hachlica, Justin; Wadie-Ibrahim, Patrick; Sahiner, M. Alper

    Silver doped ZnO is a promising compound for photovoltaic solar cell use. Doping this compound with varying amounts of silver will theoretically make this type of thin film more efficient by reducing the overall resistance and increasing the voltage and current output. The extent of this promise is being tested experimentally, by analysis of both the electrical and the surface roughness properties of the cells. Ag-doped Zinc Oxide is deposited by method of Pulsed Laser Deposition (PLD) onto Indium Tin Oxide (ITO) coated Glass. Annealing effects were also observed by varying the temperature at which the annealing occurred after synthesis of the sample. Thickness is confirmed by use of Ellipsometery. X-Ray Diffraction (XRD) measurements confirmed a ZnO crystal structure on the thin films. The active dopant carrier concentrations were determined using a Hall Effect Measuring System. Finally, the photovoltaic properties of the film are recorded by using a Keithley Source Meter. The structural characterization and electrical results of the effect of Ag doping on ZnO will then be discussed.

  8. Characterization of the ZnO thin film prepared by single source chemical vapor deposition under low vacuum condition

    Institute of Scientific and Technical Information of China (English)

    DENG; Hong(邓宏); B.; GONG; A.; J.; Petrella; J.; J.; Russell; R.; N.; Lamb

    2003-01-01

    A novel technique is developed for growing high quality ZnO thin films by means of single source chemical vapor deposition (SS CVD) under low vacuum conditions with the precursor of zinc carbamate Zn4O(CO2Net2)6. SEM, AFM and XRD studies show that the resultant thin films have high density, smooth surface, uniform polycrystalline structure and excellent c-axis orientation. XPS investigation indicates that the ZnO films are free of decomposed precursor residues in the bulk. Careful quantitative XPS analysis reveals that the ZnO films are stoichiometric with O/Zn atomic ratio very close to that of ZnO single crystal.

  9. Surface phonon polariton characteristics of wurtzite ZnO thin film grown on silicon substrate

    Energy Technology Data Exchange (ETDEWEB)

    Ng, Sha Shiong; Ooi, Poh Kok; Lee, Sai Cheong; Abdullah, Mat Johar; Hassan, Zainuriah; Hassan, Haslan Abu [Nano-Optoelectronics Research and Technology Laboratory, School of Physics, Universiti Sains Malaysia, 11800 Penang (Malaysia)

    2012-05-15

    In this work, p-polarized far infrared attenuated total reflection (ATR) with Otto configuration technique is employed to study the surface phonon polariton (SPP) characteristics of wurtzite ZnO thin film grown on Si(111) substrate. One prominent dip corresponding to the leaky SPP mode of the ZnO is detected at 532 cm{sup -1}. The obtained result is in good agreement with the calculated ATR spectrum simulated based on the transfer matrix formulation. The origin of the observed dip is verified with the surface polariton dispersion curves based on a three anisotropic layer model (air-ZnO-Si). The results also reveal that the real SPP and the interface phonon polariton modes for this studied structure are barely observable experimentally. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Preface: Thin Solid Films Topical Special Issue on ZnO Related Transparent Conductive Oxides

    Energy Technology Data Exchange (ETDEWEB)

    Chu, Jinn P.; Endo, Tamio; Ellmer, Klaus; Gessert, Tim; Ginley, David

    2016-04-03

    World-wide research activities on ZnO and related transparent conductive oxides (TCO) in thin film, nanostructured, and multilayered forms are driven by the vast potential of these materials for optoelectronic, microelectronic, and photovoltaic applications. Renewed interest in ZnO applications is partly stimulated by cost reduction in material processing and device development. One of the most important issues is doping and alloying with Al, Ga, In, Sn, etc. in order to tune properties. When highly doped, these materials are used as transparent-conducting contacts on solar cells, as well as in catalytic, spintronic, and surface acoustic wave devices. Film growth conditions, including substrate type and orientation, growth temperature, deposition rate, and ambient atmosphere, all play important roles in determining structural, electrical, magnetic, and optical properties.

  11. The magnetic ordering in high magnetoresistance Mn-doped ZnO thin films

    KAUST Repository

    Venkatesh, S.

    2016-03-24

    We studied the nature of magnetic ordering in Mn-doped ZnO thin films that exhibited ferromagnetism at 300 K and superparamagnetism at 5 K. We directly inter-related the magnetisation and magnetoresistance by invoking the polaronpercolation theory and variable range of hopping conduction below the metal-to-insulator transition. By obtaining a qualitative agreement between these two models, we attribute the ferromagnetism to the s-d exchange-induced spin splitting that was indicated by large positive magnetoresistance (∼40 %). Low temperature superparamagnetism was attributed to the localization of carriers and non-interacting polaron clusters. This analysis can assist in understanding the presence or absence of ferromagnetism in doped/un-doped ZnO.

  12. The magnetic ordering in high magnetoresistance Mn-doped ZnO thin films

    Science.gov (United States)

    Venkatesh, S.; Baras, A.; Lee, J.-S.; Roqan, I. S.

    2016-03-01

    We studied the nature of magnetic ordering in Mn-doped ZnO thin films that exhibited ferromagnetism at 300 K and superparamagnetism at 5 K. We directly inter-related the magnetisation and magnetoresistance by invoking the polaron percolation theory and variable range of hopping conduction below the metal-to-insulator transition. By obtaining a qualitative agreement between these two models, we attribute the ferromagnetism to the s-d exchange-induced spin splitting that was indicated by large positive magnetoresistance (˜40 %). Low temperature superparamagnetism was attributed to the localization of carriers and non-interacting polaron clusters. This analysis can assist in understanding the presence or absence of ferromagnetism in doped/un-doped ZnO.

  13. Thermal activation of nitrogen acceptors in ZnO thin films grown by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Dangbegnon, J.K.; Talla, K.; Botha, J.R. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth (South Africa)

    2010-06-15

    Nitrogen doping in ZnO is inhibited by spontaneous formation of compensating defects. Perfect control of the nitrogen doping concentration is required, since a high concentration of nitrogen could induce the formation of donor defects involving nitrogen. In this work, the effect of post-growth annealing in oxygen ambient on ZnO thin films grown by Metalorganic Chemical Vapor Deposition, using NO as both oxidant and nitrogen dopant, is studied. After annealing at 700 C and above, low-temperature photoluminescence shows the appearance of a transition at {proportional_to}3.23 eV which is interpreted as pair emission involving a nitrogen acceptor. A second transition at {proportional_to}3.15 eV is also discussed. This work suggests annealing as a potential means for p-type doping using nitrogen (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Effect of oxygen partial pressure on the behavior of dual ion beam sputtered ZnO thin films

    International Nuclear Information System (INIS)

    Undoped ZnO thin films were grown on p-type Si (1 0 0) substrates at different oxygen partial pressure by dual ion beam sputtering deposition system at a constant growth temperature of 400 °C. The crystallinity, surface morphology, optical, elemental and electrical properties of these ZnO thin films was studied. The minimum value of full-width at half-maximum of the θ-rocking curve obtained from x-ray diffraction of the ZnO (0 0 2) plane, was reported to be 0.1865° from ZnO film grown at 50% of (O2/(O2 + Ar))%. Crystalline property of ZnO films was observed to degrade with the increase in oxygen partial pressure. Photoluminescence measurements demonstrated sharp near-band-edge emission at ∼381 nm at room temperature. X-ray photoelectron spectroscopy study revealed presence of oxygen interstitials and vacancies as point defects in ZnO films. Electrical resistivity of ZnO was found to increase with the increase in oxygen partial pressure. (paper)

  15. Study of deposition parameters for the fabrication of ZnO thin films using femtosecond laser

    Science.gov (United States)

    Hashmi, Jaweria Zartaj; Siraj, Khurram; Latif, Anwar; Murray, Mathew; Jose, Gin

    2016-08-01

    Femtosecond (fs) pulsed laser deposition (fs-PLD) of ZnO thin film on borosilicate glass substrates is reported in this work. The effect of important fs-PLD parameters such as target-substrate distance, laser pulse energy and substrate temperature on structure, morphology, optical transparency and luminescence of as-deposited films is discussed. XRD analysis reveals that all the films grown using the laser energy range 120-230 μJ are polycrystalline when they are deposited at room temperature in a ~10-5 Torr vacuum. Introducing 0.7 mTorr oxygen pressure, the films show preferred c-axis growth and transform into a single-crystal-like film when the substrate temperature is increased to 100 °C. The scanning electron micrographs show the presence of small nano-size grains at 25 °C, which grow in size to the regular hexagonal shape particles at 100 °C. Optical transmission of the ZnO film is found to increase with an increase in crystal quality. Maximum transmittance of 95 % in the wavelength range 400-1400 nm is achieved for films deposited at 100 °C employing a laser pulse energy of 180 μJ. The luminescence spectra show a strong UV emission band peaked at 377 nm close to the ZnO band gap. The shallow donor defects increase at higher pulse energies and higher substrate temperatures, which give rise to violet-blue luminescence. The results indicate that nano-crystalline ZnO thin films with high crystalline quality and optical transparency can be fabricated by using pulses from fs lasers.

  16. Thermal conductivity of ZnO thin film produced by reactive sputtering

    International Nuclear Information System (INIS)

    ZnO thin films have been produced by reactive sputtering with different oxygen contents in the sputtering gas. As a result of transmission electronic microscopy observation, each film consist of two layers: an interfacial layer close to the substrate, with a thickness of about 200 nm, composed of very fine crystal grains and an upper layer above the interfacial layer, composed of column-shaped grains aligned along the out-plane direction. The grain diameter ranges from 35 to 100 nm depending on the oxygen partial pressure. The in-plane and out-plane thermal conductivity have been measured at room temperature. The out-plane thermal conductivity of the interfacial layer is 2.3 W m-1 K-1, independent on the oxygen partial pressure. The out-plane thermal conductivity of the upper layer is 5.4, 7.1, and 4.0 W m-1 K-1, and the in-plane thermal conductivity 4.86, 6.01, and 2.66 W m-1 K-1, for the O2 30%, 60%, and 90% ZnO film, respectively. Both out-plane and in-plane thermal conductivity decrease with the decrease of grain diameter. The thermal conductance of grain boundary has been estimated with the phonon diffusion mismatch model, and the intrinsic thermal conductivity within ZnO grains has been calculated with a cylinder-structured composite model. The result shows that the thermal conductivity of the ZnO thin films is dominated by the intrinsic thermal conductivity, which is a function of grain size.

  17. Physical Property Evaluation of ZnO Thin Film Fabricated by Low-Temperature Process for Flexible Transparent TFT.

    Science.gov (United States)

    Khafe, Adie Bin Mohd; Watanabe, Hiraku; Yamauchi, Hiroshi; Kuniyoshi, Shigekazu; Iizuka, Masaaki; Sakai, Masatoshi; Kudo, Kazuhiro

    2016-04-01

    The usual silicon-based display back planes require fairly high process temperature and thus the development of a low temperature process is needed on flexible plastic substrates. A new type of flexible organic light emitting transistor (OLET) had been proposed and investigated in the previous work. By using ultraviolet/ozone (UV/O3) assisted thermal treatments on wet processed zinc oxide field effect transistor (ZnO-FET), through low-process temperature, ZnO-FETs were fabricated which succeeded to achieve target drain current value and mobility. In this study, physical property evaluation of ZnO was conducted in term of their crystallinity, the increase composition of ZnO formed inside the thin film and the decrease of the carbon impurities originated from aqueous solution of the ZnO itself. The X-ray diffraction (XRD) evaluation showed UV/03 assisted thermal treatment has no obvious effect towards crystallinity of ZnO in the range of low process temperature. Moreover, through X-ray photoelectron spectroscopy (XPS) evaluation and Fourier transform infrared (FT-IR) spectroscopy evaluation, more carbon impurities disappeared from the ZnO thin film and the increase of composition amount of ZnO, when the thin film was subjected to UV/O3 assisted thermal treatment. Therefore, UV/O3 assisted thermal treatment contributed in carbon impurities elimination and accelerate ZnO formation in ZnO thin film, which led to the improvement in the electrical property of ZnO-FET in the low-process temperature. PMID:27451599

  18. Synthesis of PS colloidal crystal templates and ordered ZnO porous thin films by dip-drawing method

    Energy Technology Data Exchange (ETDEWEB)

    Liu Zhifeng [Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education, School of Materials, Tianjin University, Tianjin 300072 (China); Jin Zhengguo [Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education, School of Materials, Tianjin University, Tianjin 300072 (China)]. E-mail: zhgjin@tju.edu.cn; Li Wei [Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education, School of Materials, Tianjin University, Tianjin 300072 (China); Qiu Jijun [Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education, School of Materials, Tianjin University, Tianjin 300072 (China); Zhao Juan [Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education, School of Materials, Tianjin University, Tianjin 300072 (China); Liu Xiaoxin [Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education, School of Materials, Tianjin University, Tianjin 300072 (China)

    2006-05-15

    Polystyrene spheres (PS) were synthesized by an emulsifier-free emulsion polymerization technique and the PS colloidal crystal templates were assembled orderly on clean glass substrates by dip-drawing method from emulsion of PS. Porous ZnO thin films were prepared by filling the ZnO sol into the spaces among the close-packed PS templates and then annealing to remove the PS templates. The effects of ZnO precursor sol concentration and dipping time in sol on the porous structure of the thin films were studied. The results showed an ordered ZnO porous thin film with designed pore size that depended on the sol concentration and PS size could be obtained. And the shrinkage of pore diameter was about 30-43%. X-ray diffraction (XRD) spectra indicated the thin film was wurtzite structure. The transmittance spectrum showed that optical transmittance decreased with the decrease of wavelength, but kept above 80% optical transmittances beyond the wavelength of 550 nm. Optical band gap of the porous ZnO thin film (fired at 500 deg. C) was 3.22 eV.

  19. Effects of annealing on properties of ZnO thin films prepared by electrochemical deposition in chloride medium

    International Nuclear Information System (INIS)

    The development of cost-effective and low-temperature synthesis techniques for the growth of high-quality zinc oxide thin films is paramount for fabrication of ZnO-based optoelectronic devices, especially ultraviolet (UV)-light-emitting diodes, lasers and detectors. We demonstrate that the properties, especially UV emission, observed at room temperature, of electrodeposited ZnO thin films from chloride medium (at 70 deg. C) on fluor-doped tin oxide (FTO) substrates is strongly influenced by the post-growth thermal annealing treatments. X-ray diffraction (XRD) measurements show that the films have preferably grown along (0 0 2) direction. Thermal annealing in the temperature range of 150-400 deg. C in air has been carried out for these ZnO thin films. The as-grown films contain chlorine which is partially removed after annealing at 400 deg. C. Morphological changes upon annealing are discussed in the light of compositional changes observed in the ZnO crystals that constitute the film. The optical quality of ZnO thin films was improved after post-deposition thermal treatment at 150 deg. C and 400 deg. C in our experiments due to the reducing of defects levels and of chlorine content. The transmission and absorption spectra become steeper and the optical bandgap red shifted to the single-crystal value. These findings demonstrate that electrodeposition have potential for the growth of high-quality ZnO thin films with reduced defects for device applications.

  20. Synthesis of PS colloidal crystal templates and ordered ZnO porous thin films by dip-drawing method

    International Nuclear Information System (INIS)

    Polystyrene spheres (PS) were synthesized by an emulsifier-free emulsion polymerization technique and the PS colloidal crystal templates were assembled orderly on clean glass substrates by dip-drawing method from emulsion of PS. Porous ZnO thin films were prepared by filling the ZnO sol into the spaces among the close-packed PS templates and then annealing to remove the PS templates. The effects of ZnO precursor sol concentration and dipping time in sol on the porous structure of the thin films were studied. The results showed an ordered ZnO porous thin film with designed pore size that depended on the sol concentration and PS size could be obtained. And the shrinkage of pore diameter was about 30-43%. X-ray diffraction (XRD) spectra indicated the thin film was wurtzite structure. The transmittance spectrum showed that optical transmittance decreased with the decrease of wavelength, but kept above 80% optical transmittances beyond the wavelength of 550 nm. Optical band gap of the porous ZnO thin film (fired at 500 deg. C) was 3.22 eV

  1. Arrays of ZnO nanocolumns for 3-dimensional very thin amorphous and microcrystalline silicon solar cells

    International Nuclear Information System (INIS)

    We report on the hydrothermal growth of high quality arrays of single crystalline zinc oxide (ZnO) nanocolumns, oriented perpendicularly to the transparent conductive oxide substrate. In order to obtain precisely defined spacing and arrangement of ZnO nanocolumns over an area up to 0.5 cm2, we used electron beam lithography. Vertically aligned ZnO (multicrystalline or single crystals) nanocolumns were grown in an aqueous solution of zinc nitrate hexahydrate and hexamethylenetetramine at 95 °C, with a growth rate 0.5 ÷ 1 μm/h. The morphology of the nanostructures was visualized by scanning electron microscopy. Such nanostructured ZnO films were used as a substrate for the recently developed 3-dimensional thin film silicon (amorphous, microcrystalline) solar cell, with a high efficiency potential. The photoelectrical and optical properties of the ZnO nanocolumns and the silicon absorber layers of these type nanostructured solar cells were investigated in details. - Highlights: • Vertically-oriented ZnO nanocolumns were grown by hydrothermal method. • The ZnO nanocolumns were grown over an area of 0.5 cm2. • For precise arrangement of the ZnO nanocolumns electron beam lithography was used. • We report on 3-D design of nanostructured solar cell. • Optical thickness of nanostructured cell was three times higher compared to flat cell

  2. Photovoltaic properties of ZnO nanorods/p-type Si heterojunction structures

    Directory of Open Access Journals (Sweden)

    Rafal Pietruszka

    2014-02-01

    Full Text Available Selected properties of photovoltaic (PV structures based on n-type zinc oxide nanorods grown by a low temperature hydrothermal method on p-type silicon substrates (100 are investigated. PV structures were covered with thin films of Al doped ZnO grown by atomic layer deposition acting as transparent electrodes. The investigated PV structures differ in terms of the shapes and densities of their nanorods. The best response is observed for the structure containing closely-spaced nanorods, which show light conversion efficiency of 3.6%.

  3. High-performance metal–semiconductor–metal UV photodetector based on spray deposited ZnO thin films

    International Nuclear Information System (INIS)

    Highlights: • ZnO based MSM UV photodetector by economical chemical spray pyrolysis technique. • Effect of substrate temperature on properties of ZnO based MSM UV photodetector. • Photoresponse mechanism by optical switching property of ZnO thin film photodetectors. - Abstract: Zinc oxide (ZnO) based metal–semiconductor–metal (MSM) ultraviolet photodetectors at different substrate temperatures were fabricated on glass substrates by economical chemical spray pyrolysis technique and its UV photoresponsivity was measured at room temperature. The samples were characterized with respect to their structural, morphological, and optical properties using various methods such as X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–Vis spectroscopy, transmittance, reflectance etc. The synthesized ZnO thin films were c-axis oriented with hexagonal crystal structure as confirmed from XRD. All deposited films were specular and show high transmittance (∼85%) in visible region with steep fall off at 375 nm. The photoconductive MSM UV photodetector showed relatively high photocurrent (1.3 mA) and fast switching. ZnO thin films exhibited relatively high photoresponsivity (788 A/W) with cut of wavelength ∼375 nm signifying their application as UV detector

  4. Microstructures, optical and electrical properties of In-doped ZnO thin films prepared by sol-gel method

    International Nuclear Information System (INIS)

    ZnO and indium-doped ZnO (IxZO) thin films were prepared on silica-glass substrates by the sol-gel method. The thin films were crystallized at 600 deg. C and 700 deg. C for 1 h in 6.9 x 10-1 Torr under pure O2 atmosphere. The analyzed results were compared to investigate the structural characteristics and optical properties. The surface morphology of the IxZO films was different from that of the ZnO films, and showed a thin overlay structure. In addition, the crystallization of IxZO film was depleted at higher crystallized temperatures. From XRD analysis, the ZnO and IxZO thin films possessed hexagonal structures. Notably, micro-In2O3 phases were observed in the IxZO thin films using EDS. Both of In2O3 phases and the crystallization mechanism not only improved the peeling of structure, but also improved the electrical conductivity of IxZO thin films. For the PL spectrum, the optical property of the IxZO film was raised at a higher crystallization temperature. Although the In2O3 phases reduced the structural defects of IxZO thin film, the optical effect of the residual In3+ was not enhanced completely at higher crystallized temperatures.

  5. Indium-doped ZnO thin films deposited by the sol-gel technique

    International Nuclear Information System (INIS)

    Conducting and transparent indium-doped ZnO thin films were deposited on sodocalcic glass substrates by the sol-gel technique. Zinc acetate and indium chloride were used as precursor materials. The electrical resistivity, structure, morphology and optical transmittance of the films were analyzed as a function of the film thickness and the post-deposition annealing treatments in vacuum, oxygen or argon. The obtained films exhibited a (002) preferential growth in all the cases. Surface morphology studies showed that an increase in the films' thickness causes an increase in the grain size. Films with 0.18 μm thickness, prepared under optimal deposition conditions followed by an annealing treatment in vacuum showed electrical resistivity of 1.3 x 10-2 Ωcm and optical transmittance higher than 85%. These results make ZnO:In thin films an attractive material for transparent electrodes in thin film solar cells

  6. Characterization of nanostructured ZnO thin films deposited through vacuum evaporation

    Science.gov (United States)

    Maldonado, Arturo; Juarez, Héctor; Pacio, Mauricio; Perez, Rene

    2015-01-01

    Summary This work presents a novel technique to deposit ZnO thin films through a metal vacuum evaporation technique using colloidal nanoparticles (average size of 30 nm), which were synthesized by our research group, as source. These thin films had a thickness between 45 and 123 nm as measured by profilometry. XRD patterns of the deposited thin films were obtained. According to the HRSEM micrographs worm-shaped nanostructures are observed in samples annealed at 600 °C and this characteristic disappears as the annealing temperature increases. The films obtained were annealed from 25 to 1000 °C, showing a gradual increase in transmittance spectra up to 85%. The optical band gaps obtained for these films are about 3.22 eV. The PL measurement shows an emission in the red and in the violet region and there is a correlation with the annealing process. PMID:25977868

  7. Characterization of nanostructured ZnO thin films deposited through vacuum evaporation

    Directory of Open Access Journals (Sweden)

    Jose Alberto Alvarado

    2015-04-01

    Full Text Available This work presents a novel technique to deposit ZnO thin films through a metal vacuum evaporation technique using colloidal nanoparticles (average size of 30 nm, which were synthesized by our research group, as source. These thin films had a thickness between 45 and 123 nm as measured by profilometry. XRD patterns of the deposited thin films were obtained. According to the HRSEM micrographs worm-shaped nanostructures are observed in samples annealed at 600 °C and this characteristic disappears as the annealing temperature increases. The films obtained were annealed from 25 to 1000 °C, showing a gradual increase in transmittance spectra up to 85%. The optical band gaps obtained for these films are about 3.22 eV. The PL measurement shows an emission in the red and in the violet region and there is a correlation with the annealing process.

  8. Producing CuO and ZnO composite thin films using the spin coating method on microscope glasses

    International Nuclear Information System (INIS)

    Highlights: ► Annealing at 600 °C and 700 °C creates crystallinity in all doping concentrations. ► Starting with pure ZnO thin films and ending up with CuO by doping Cu in various percentages (ranging from 0% to 100%). ► Justification of the crystal phases by XRD spectra. ► Pure ZnO thin films have the absorption band at 370 nm and CuO has a strong absorption band at 570 nm. -- Abstract: In this work, we have presented a new route to produce pure ZnO and composite ZnO-CuO thin films. In the process we have started with pure ZnO thin films and ended up with CuO by doping Cu in various percentages, ranging from 0% to 100%. We have managed to attain crystal phases in all doping concentrations. All the produced thin films have been crystallized at the annealing temperatures of 600 and 700 °C for 6 h. The X-ray diffraction (XRD) spectra have been performed to see the formation of crystal phases of all pure ZnO and composite ZnO-CuO thin films. These give insight that the two crystal phases related to ZnO and CuO stayed together within the thin film matrices, which were produced in different doping concentrations, i.e. nZnO + mCuO (0 ≤ n, m ≤ 100%). The scanning electron microscopy (SEM) micrographs and UV–vis absorption spectra have also been taken to elucidate the structure and composition of the all films

  9. Ultrasonic spray pyrolysis growth of ZnO and ZnO:Al nanostructured films: Application to photocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    Kenanakis, G., E-mail: gkenanak@iesl.forth.gr [Institute of Electronic Structure and Laser, Foundation for Research and Technology – Hellas, P.O. Box 1385, Vassilika Vouton, 711 10 Heraklion, Crete (Greece); Center of Materials Technology and Photonics, School of Applied Technology, Technological Educational Institute of Crete, 710 04 Heraklion, Crete (Greece); Katsarakis, N. [Institute of Electronic Structure and Laser, Foundation for Research and Technology – Hellas, P.O. Box 1385, Vassilika Vouton, 711 10 Heraklion, Crete (Greece); Center of Materials Technology and Photonics, School of Applied Technology, Technological Educational Institute of Crete, 710 04 Heraklion, Crete (Greece)

    2014-12-15

    Highlights: • Al–ZnO thin films and nanostructures were obtained by ultrasonic spray pyrolysis. • The texture and morphology of the samples depend on the deposition parameters. • The photocatalytic degradation of stearic acid was studied upon UV-A irradiation. - Abstract: Pure and Al-doped ZnO (Al = 1, 3, 5%) nanostructured thin films were grown at 400 °C on glass substrates by ultrasonic spray pyrolysis, a simple, environmental-friendly and inexpensive method, using aqueous solutions as precursors. The structural and morphological characteristics of the samples depend drastically on deposition parameters; ZnO nanostructured films, nanopetals and nanorods were systematically obtained by simply varying the precursor solution and/or the spraying time. Transmittance measurements have shown that all samples are transparent in the visible wavelength region. Finally, the photocatalytic properties of the samples were investigated against the degradation of stearic acid under UV-A light illumination (365 nm); both pure and Al-doped ZnO nanostructured thin films show good photocatalytic activity regarding the degradation of stearic acid, due to their good crystallinity and large surface area.

  10. Ultrasonic spray pyrolysis growth of ZnO and ZnO:Al nanostructured films: Application to photocatalysis

    International Nuclear Information System (INIS)

    Highlights: • Al–ZnO thin films and nanostructures were obtained by ultrasonic spray pyrolysis. • The texture and morphology of the samples depend on the deposition parameters. • The photocatalytic degradation of stearic acid was studied upon UV-A irradiation. - Abstract: Pure and Al-doped ZnO (Al = 1, 3, 5%) nanostructured thin films were grown at 400 °C on glass substrates by ultrasonic spray pyrolysis, a simple, environmental-friendly and inexpensive method, using aqueous solutions as precursors. The structural and morphological characteristics of the samples depend drastically on deposition parameters; ZnO nanostructured films, nanopetals and nanorods were systematically obtained by simply varying the precursor solution and/or the spraying time. Transmittance measurements have shown that all samples are transparent in the visible wavelength region. Finally, the photocatalytic properties of the samples were investigated against the degradation of stearic acid under UV-A light illumination (365 nm); both pure and Al-doped ZnO nanostructured thin films show good photocatalytic activity regarding the degradation of stearic acid, due to their good crystallinity and large surface area

  11. Structural and optical properties of electrodeposited ZnO thin films

    International Nuclear Information System (INIS)

    Zinc oxide thin films were electrodeposited on different substrates. Electrodeposition was performed with hydrogen peroxide, as hydroxide ions source, at - 1.5 V versus mercurial sulfate electrode during one hour, and a temperature maintained at 70 deg. C . The resulting thin films have a good crystallinity and a high c-axis orientation, and the unit cell parameters determined by X-ray diffraction experiment are a = 0.326 nm and c = 0.523 nm, respectively. Microstructure studies using scanning electron microscopy and atomic force microscopy show a good homogeneity of the film and a roughness around 22 nm. Optical properties were studied with Raman spectroscopy and photoluminescence spectroscopy. Optical properties of the films revealed a low defect emission in photoluminescence spectra. The E2 vibration mode for ZnO was observed near 439 cm-1, indicating that the as-deposited films were under compressive stress. Oscillations were observed in the photoluminescence spectra, from which the refractive index of ZnO thin films was extracted, that is ∼ 1.90

  12. Giant coercivity in ferromagnetic Co doped ZnO single crystal thin film

    International Nuclear Information System (INIS)

    The origin of ferromagnetism in ZnO doped with transition metal impurities has been discussed extensively and appeared to be a highly controversial and challenging topic in today's solid state physics. Magnetism observed in this system is generally weak and soft. We have grown Co:ZnO up to 30 at% Co in single crystal thin film form on c-plane sapphire. A composition dependent coercivity is observed in this system which reaches peak value at 25 at% Co, the values are 860 Oe and 1149 Oe with applied field along parallel and perpendicular to the film substrate interface respectively. This giant coercivity might pave the way to exploit this material as a magnetic semiconductor with novel logic functionalities. The findings are explained based on defect band itinerant ferromagnetism and its partial interaction with localized d electrons of Co through charge transfer. Besides large coercivity, an increase in the band gap with Co concentration has also been observed along with blue emission peak with long tail confirming the formation of extended point defect levels in the host lattice band gap. - Highlights: • Co doped ZnO ferromagnetic single crystal thin film. • Giant coercivity in Co:ZnO thin film which may help to turn this material into application. • Cathodoluminescence (CL) data showing increase in band gap with Co concentrations. • A theoretical proposal is made to explain the observed giant coercivity

  13. Room temperature pulsed laser deposited ZnO thin films as photoluminiscence gas sensors

    Energy Technology Data Exchange (ETDEWEB)

    Padilla-Rueda, D.; Vadillo, J.M. [Department of Analytical Chemistry, Faculty of Science, University of Malaga, UMA Campus Teatinos, s/n, 29071 Malaga (Spain); Laserna, J.J., E-mail: laserna@uma.es [Department of Analytical Chemistry, Faculty of Science, University of Malaga, UMA Campus Teatinos, s/n, 29071 Malaga (Spain)

    2012-10-15

    Highlights: Black-Right-Pointing-Pointer Elaboration of functional ZnO thin films by PLD at room temperature is possible. Black-Right-Pointing-Pointer Fluorescence quenching of ZnO thin films may be used for NO{sub 2} sensors. Black-Right-Pointing-Pointer Addition of oxygen during deposition is required to get films of better quality. Black-Right-Pointing-Pointer Films exhibited linear behaviour in the range between 26 and 100 ppm. - Abstract: Zinc oxide thin films with optical sensing capabilities for NO{sub 2} have been elaborated by pulsed laser deposition (PLD) onto glass substrates at room temperature with Nd:YAG laser (1064 nm). Morphology, chemical composition and optical characteristics of the films were evaluated as a function of laser fluence, gas pressure and target-to-substrate distance. Films exhibit excellent morphological and optical (transmittance and photoluminescence) properties. The films have been evaluated as fluorescence sensors for NO{sub 2} in the concentration range between 26 and 200 ppm.

  14. Effect of band gap energy on the electrical conductivity in doped ZnO thin film

    International Nuclear Information System (INIS)

    The transparent conductive pure and doped zinc oxide thin films with aluminum, cobalt and indium were deposited by ultrasonic spray technique on glass substrate at 350 °C. This paper is to present a new approach to the description of correlation between electrical conductivity and optical gap energy with dopants' concentration of Al, Co and In. The correlation between the electrical and optical properties with doping level suggests that the electrical conductivity of the films is predominantly estimated by the band gap energy and the concentrations of Al, Co and In. The measurement in the electrical conductivity of doped films with correlation is equal to the experimental value, the error of this correlation is smaller than 13%. The minimum error value was estimated in the cobalt-doped ZnO thin films. This result indicates that such Co-doped ZnO thin films are chemically purer and have far fewer defects and less disorder owing to an almost complete chemical decomposition. (semiconductor materials)

  15. In situ doping of ZnO nanowires using aerosol-assisted chemical vapour deposition

    Energy Technology Data Exchange (ETDEWEB)

    Pung, Swee-Yong; Choy, Kwang-Leong; Hou Xianghui; Dinsdale, Keith, E-mail: Kwang-leong.Choy@nottingham.ac.uk [Faculty of Engineering, Energy and Sustainability Research Division, University of Nottingham, Nottingham NG7 2RD (United Kingdom)

    2010-08-27

    An in situ doping approach of producing Al-doped ZnO NWs was demonstrated using an aerosol-assisted chemical vapour deposition (AA-CVD) technique. In this technique, Zn precursor was kept in the middle of a horizontal tube furnace whereas the dopant solution was kept in an aerosol generator, which was located outside the furnace. The Al aerosol was flowed into the reactor during the growth of NWs in order to achieve in situ doping. Al-doped ZnO NWs were synthesized as verified by the combination of XRD, TEM/EDS and TOF-SIMS analysis. Highly (00.2) oriented ZnO seed layers were used to promote vertically aligned growth of Al-doped ZnO NWs. Lastly, a growth mechanism of vertically aligned Al-doped ZnO NWs was discussed.

  16. Fabrication and characterization of pristine and annealed Ga doped ZnO thin films using sputtering

    Science.gov (United States)

    Mishra, Abhisek; Mohapatra, Saswat; Gouda, Himanshu Sekhar; Singh, Udai P.

    2016-05-01

    ZnO is a wide-band gap, transparent, polar semiconductor with unparalleled optoelectronic, piezoelectric, thermal and transport properties, which make it the material of choice for a wide range of applications such as blue/UV optoelectronics, energy conversion, transparent electronics, spintronic, plasmonic and sensor devices. We report, three sets of Ga doped Zinc Oxide (GZO) were fabricated in different sputtering power (100 watt, 200 watt and 300 watt). Thereafter films were annealed in nitrogen ambient for 30 minutes at 400° C. From the optical absorption spectroscopy it was found that pristine films are showing a 75% transmittance in the visible region of light and it increases after the annealing. However, for 300 W grown sample opposite trend has been achieved for the post annealed sample. X-ray diffraction pattern of all the pristine and annealed films showed a preferable growth orientation at (002) phase. Some other weak peaks were also appeared in different angle which indicates that films are polycrystalline in nature. XRD data also reveals that crystallite size increases with sputtering power up to 200 W and thereafter it decreases with the deposition power. It also noted that the crystallite size of the annealed film increases with compare to the non annealed films. At room temperature an enhancement in electrical properties of Ga doped ZnO thin films was noted for the annealed ZnO films except for the film deposited at 300 watt. More significantly, it was found that annealed thin films showed the resistivity in the range of 10-3 ˜ 10-4 ohm-cm. Such a high optical transmittance and conducting zinc-oxide thin film can be used as a window layer in solar cell.

  17. Thickness dependent magnetic transitions in pristine MgO and ZnO sputtered thin films

    Directory of Open Access Journals (Sweden)

    Mukes Kapilashrami

    2010-09-01

    Full Text Available We report a systematic study of the thickness dependency of room temperature ferromagnetism in pristine MgO (~100–500 nm and ZnO (~100–1000 nm thin films deposited by reactive magnetron sputtering technique under the respective identical controlled optimum oxygen ambience. As far as we know this is the first such report on ferromagnetic pure MgO thin films, a result which should be of significance in understanding the functional aspects of magnetic tunnelling characteristics in devices using MgO dielectrics. From the magnetic characterization we observe a distinct variation in the saturation magnetization (MS with increasing film thickness. In the case of MgO thin films MS values vary in the range 0.04–1.58 emu/g (i.e. 0.0012–0.046 μB/unit cell with increasing film thickness showing the highest MS value for the 170 nm thick film. Above this thickness MS is found to decrease and eventually above 420 nm the films show a paramagnetic behaviour followed by the well known diamagnetic property for the bulk (>500 nm. It is obvious that since initially the MS values increase with thickness, there has to be a maximum before the films become diamagnetic at some finite thickness. We also note that the MS values observed for MgO are the highest (more than twice the value observed for ZnO to be reported for such a defect induced ferromagnetism in a pristine oxide. The origin of ferromagnetic order in both the oxides appears to arise from the respective cat-ion vacancies. The discovery of film thickness dependent ferromagnetic order should be very useful in developing multifunctional devices based on the technologically important materials MgO and ZnO.

  18. Bandgap-controlled non-equilibrium ZnO1−xSx thin films grown by pulsed laser deposition method

    International Nuclear Information System (INIS)

    Although ZnO and ZnS are chemically and structurally similar, these binary compounds do not form a solid solution at room temperature for all proportions of sulfur (S) and oxygen (O) due to solubility limits of S in ZnO and O in ZnS in equilibrium states. To fabricate ZnO1−xSx thin films with 0 < x < 1, films were intentionally deposited in a non-equilibrium state using pulsed laser deposition while controlling oxygen pressures. The deposited ZnO1−xSx thin film structures were investigated by X-ray diffraction, confirming the formation of hexagonal wurtzite structures with c-axis lattice constants larger than that of ZnO and smaller than that of ZnS. Furthermore, phase segregation to ZnO and ZnS was observed by increasing the temperature of the ZnO0.5S0.5 thin film, suggesting non-equilibrium state of the deposited film. The observed optical energy bandgaps of the ZnO1−xSx thin films were smaller than those of both ZnO (~ 3.3 eV) and ZnS (~ 3.68 eV), suggesting a bandgap bowing effect due to valance and conduction band shifts. - Highlights: • We successfully deposited a II–VI type of semiconductors, ZnO1−xSx thin films. • We study about ZnO0.5S0.5 phase with temperature dependent XRD. • The contents of ZnO1−xSx thin films are from 1(ZnS) to 0(ZnO)

  19. Characterization of dilute magnetic semiconducting transition metal doped ZnO thin films by sol–gel spin coating method

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Diluted magnetic semiconducting TM (Ni, Mn, Co) doped ZnO thin films were fabricated by sol–gel spin coating technique. • The XRD analyses revealed that the TM (Ni, Mn, Co) doped ZnO films have hexagonal wurtzite structure. • Photoluminescence and micro-Raman spectra were interpreted for TM (Ni, Mn, Co) doped ZnO thin films. • SEM morphology studies were made for Zn0.97 Ni0.03O, Zn0.97 Mn0.03O and Zn0.97 Co0.03O thin films. • Room temperature ferromagnetism was observed in TM (Ni, Mn, Co) doped ZnO thin films. - Abstract: Pure and transition metal (TM = Ni, Mn, Co) doped zinc oxide (ZnO) thin films were prepared by sol–gel spin coating method with a concentration of 0.03 mol% of transition metals. X-ray diffraction studies revealed the polycrystalline nature of the films with the presence of hexagonal wurtzite structure. UV transmittance spectra showed that all the films are highly transparent in the visible region and in the case of doped ZnO thin films, d–d transition was observed in the violet region due to the existence of crystalline defects and grain boundaries. The optical band gap of the films decreases with increasing orbital occupation numbers of 3d electrons due to the orbital splitting of magnetic ions. Ultraviolet and near-infrared electronic transitions were observed which reveals a strong relationship with the doping of transition metal into ZnO site. The observed luminescence in the green, violet and red regions strongly depends on the doping elements owing to the different oxygen vacancy, oxygen interstitial, and surface morphology. The surface morphology of thin films was investigated by scanning electron microscope (SEM). The energy dispersive X-ray analysis (EDX) confirmed the stoichiometric composition of the TM doped ZnO thin films. Magnetic measurements at room temperature exhibited well defined ferromagnetic features of the thin films

  20. Characterization of dilute magnetic semiconducting transition metal doped ZnO thin films by sol–gel spin coating method

    Energy Technology Data Exchange (ETDEWEB)

    Vijayaprasath, G.; Murugan, R. [Department of Physics, Alagappa University, Karaikudi 630004, Tamil Nadu (India); Ravi, G., E-mail: gravicrc@gmail.com [Department of Physics, Alagappa University, Karaikudi 630004, Tamil Nadu (India); Mahalingam, T. [Department of Electrical and Computer Engineering, Ajou University, Suwon 443-749 (Korea, Republic of); Hayakawa, Y. [Research Institute of Electronics, Shizuoka University, Hamamatsu 432-8011 (Japan)

    2014-09-15

    Graphical abstract: - Highlights: • Diluted magnetic semiconducting TM (Ni, Mn, Co) doped ZnO thin films were fabricated by sol–gel spin coating technique. • The XRD analyses revealed that the TM (Ni, Mn, Co) doped ZnO films have hexagonal wurtzite structure. • Photoluminescence and micro-Raman spectra were interpreted for TM (Ni, Mn, Co) doped ZnO thin films. • SEM morphology studies were made for Zn{sub 0.97} Ni{sub 0.03}O, Zn{sub 0.97} Mn{sub 0.03}O and Zn{sub 0.97} Co{sub 0.03}O thin films. • Room temperature ferromagnetism was observed in TM (Ni, Mn, Co) doped ZnO thin films. - Abstract: Pure and transition metal (TM = Ni, Mn, Co) doped zinc oxide (ZnO) thin films were prepared by sol–gel spin coating method with a concentration of 0.03 mol% of transition metals. X-ray diffraction studies revealed the polycrystalline nature of the films with the presence of hexagonal wurtzite structure. UV transmittance spectra showed that all the films are highly transparent in the visible region and in the case of doped ZnO thin films, d–d transition was observed in the violet region due to the existence of crystalline defects and grain boundaries. The optical band gap of the films decreases with increasing orbital occupation numbers of 3d electrons due to the orbital splitting of magnetic ions. Ultraviolet and near-infrared electronic transitions were observed which reveals a strong relationship with the doping of transition metal into ZnO site. The observed luminescence in the green, violet and red regions strongly depends on the doping elements owing to the different oxygen vacancy, oxygen interstitial, and surface morphology. The surface morphology of thin films was investigated by scanning electron microscope (SEM). The energy dispersive X-ray analysis (EDX) confirmed the stoichiometric composition of the TM doped ZnO thin films. Magnetic measurements at room temperature exhibited well defined ferromagnetic features of the thin films.

  1. Electrical and optical properties of p-type codoped ZnO thin films prepared by spin coating technique

    Science.gov (United States)

    Pathak, Trilok Kumar; Kumar, Vinod; Swart, H. C.; Purohit, L. P.

    2016-03-01

    Undoped, doped and codoped ZnO thin films were synthesized on glass substrates using a spin coating technique. Zinc acetate dihydrate, ammonium acetate and aluminum nitrate were used as precursor for zinc, nitrogen and aluminum, respectively. X-ray diffraction shows that the thin films have a hexagonal wurtzite structure for the undoped, doped and co-doped ZnO. The transmittance of the films was above 80% and the band gap of the film varied from 3.20 eV to 3.24 eV for undoped and doped ZnO. An energy band diagram to describe the photoluminescence from the thin films was also constructed. This diagram includes the various defect levels and possible quasi-Fermi levels. A minimum resistivity of 0.0834 Ω-cm was obtained for the N and Al codoped ZnO thin films with p-type carrier conductivity. These ZnO films can be used as a window layer in solar cells and in UV lasers.

  2. Influence of pH on ZnO nanocrystalline thin films prepared by sol–gel dip coating method

    Indian Academy of Sciences (India)

    K Sivakumar; V Senthil Kumar; N Muthukumarasamy; M Thambidurai; T S Senthil

    2012-06-01

    ZnO nanocrystalline thin films have been prepared on glass substrates by sol–gel dip coating method. ZnO thin films have been coated at room temperature and at four different pH values of 4, 6, 8 and 10. The X-ray diffraction pattern showed that ZnO nanocrystalline thin films are of hexagonal structure and the grain size was found to be in the range of 25–45 nm. Scanning electron microscopic images show that the surface morphology improves with increase of pH values. TEM analysis reveals formation of ZnO nanocrystalline with an average grain size of 44 nm. The compositional analysis results show that Zn and O are present in the sample. Optical band studies show that the films are highly transparent and exhibit a direct bandgap. The bandgap has been found to lie in the range of 3.14–3.32 eV depending on pH suggesting the formation of ZnO nanocrystalline thin films.

  3. RF magnetron-sputtered ZNO thin films: on the evolution of microstructure and residual stresses

    OpenAIRE

    Özen, İstem; Ozen, Istem

    2006-01-01

    Thin ZnO films (200-500 nm) were deposited onto glass, mica, and Si(100) substrates, to study the relations between microstructure and residual stresses. The ranges for the substrate temperature, chamber pressure, and RF power were room temperature-200 °C, 0.009-0.4 mbar, and 100-125 W, respectively. The strain measurements by x-ray diffraction and the biaxial stress model showed that the films were under residual compressive stresses from -2 to -8 GPa. 5-11 percent of those stresses were ind...

  4. Photoelectrocatalytic decolorization and degradation of textile effluent using ZnO thin films.

    Science.gov (United States)

    Sapkal, R T; Shinde, S S; Mahadik, M A; Mohite, V S; Waghmode, T R; Govindwar, S P; Rajpure, K Y; Bhosale, C H

    2012-09-01

    Zinc oxide (ZnO) thin films have been successfully deposited onto fluorine doped tin oxide coated glass at substrate temperature of 400 °C and used as electrode in photoelectrocatalytic reactor. The untreated textile effluent was circulated through photoelectrocatalytic reactor under UVA illumination for the decolorization and degradation. Textile effluent was decolorized by 93% within 3h at room temperature with significant reduction in COD (69%). High performance liquid chromatography (HPLC) and Fourier transform infrared spectroscopy (FTIR) analysis of samples before and after decolorization confirmed the degradation of dyes molecules from textile effluent into simpler oxidizable products. Phytotoxicity study revealed reduction in toxic nature of textile effluent after treatment. PMID:22727863

  5. Ripple topography on thin ZnO films by grazing and oblique incidence ion sputtering

    OpenAIRE

    Bhattacharjee, S.; Karmakar, P.; Naik, V.; Sinha, A. K.; Charkrabarti, A.

    2011-01-01

    We have investigated the formation and growth of nano sized ripple topography on ZnO thin films by 10 keV O1+ bombardment at impact angles of 80{\\degree} and 60{\\degree}, varying the ion fluence from 5{times}10^16 to 1{\\times}10^18 ions/cm2. At 800 the ripples are oriented along the ion beam direction whereas at 600 it is perpendicular to the ion beam direction. The developed ion induced structures are characterized by Atomic Force Microscopy (AFM) and the alignment, variation of rms roughnes...

  6. Structural characterization of ZnO thin films grown on various substrates by pulsed laser deposition

    Czech Academy of Sciences Publication Activity Database

    Novotný, Michal; Čížek, J.; Kužel, R.; Bulíř, Jiří; Lančok, Ján; Connolly, J.; McCarthy, E.; Krishnamurthy, S.; Mosnier, J.-P.; Anwand, W.; Brauer, G.

    2012-01-01

    Roč. 45, č. 22 (2012), 1-12. ISSN 0022-3727 R&D Projects: GA ČR(CZ) GAP108/11/0958; GA ČR GP202/09/P324 Institutional research plan: CEZ:AV0Z10100522 Keywords : ZnO thin film * pulsed laser deposition * x-ray diffraction positron implantation spectroscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.528, year: 2012 http://dx.doi.org/10.1088/0022-3727/45/22/225101

  7. Cerium and europium doped ZnO thin films fabricated by pulsed laser deposition

    Czech Academy of Sciences Publication Activity Database

    Novotný, Michal; Fitl, P.; Bulíř, Jiří; Marešová, E.; Hruška, P.; Guille, A.; Guy, S.; Drahokoupil, Jan; Fekete, Ladislav; Lančok, Ján

    Lille: European Materials Research Society, 2014 - (Lippert, T.). J-24-J-24 [E- MRS 2014 Spring Meeting. 26.05.2014-30.05.2014, Lille] R&D Projects: GA MŠk(CZ) LM2011029; GA ČR(CZ) GAP108/11/0958; GA MŠk(CZ) 7AMB14FR010 Grant ostatní: AVČR(CZ) M100101271 Institutional support: RVO:68378271 Keywords : cerium * europium * ZnO * thin film * pulsed laser deposition Subject RIV: BM - Solid Matter Physics ; Magnetism

  8. Optical spectra and direct optical transitions in amorphousand crystalline ZnO thin films and powders

    Czech Academy of Sciences Publication Activity Database

    Dejneka, Alexandr; Aulika, I.; Makarova, Marina; Hubička, Zdeněk; Churpita, Olexandr; Chvostová, Dagmar; Jastrabík, Lubomír; Trepakov, Vladimír

    2009-01-01

    Roč. 157, č. 2 (2009), G67-G70. ISSN 0013-4651 R&D Projects: GA ČR GA202/08/1009; GA AV ČR KJB100100703; GA AV ČR KAN301370701; GA MŠk(CZ) 1M06002 Institutional research plan: CEZ:AV0Z10100522 Keywords : ZnO * amorphous and crystalline thin films * nanocrystalline powders * direct optical bandgap Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.241, year: 2009

  9. Synthesis and optical properties of Mn doped ZnO thin films

    Czech Academy of Sciences Publication Activity Database

    Chvostová, Dagmar; Dejneka, Alexandr; Hubička, Zdeněk; Churpita, Olexandr; Bykov, Pavlo; Jastrabík, Lubomír; Trepakov, Vladimír

    2011-01-01

    Roč. 208, č. 9 (2011), 2140-2143. ISSN 1862-6300 R&D Projects: GA ČR GC202/09/J017; GA AV ČR KAN301370701; GA MŠk(CZ) 1M06002; GA ČR GA202/09/0800 Institutional research plan: CEZ:AV0Z10100522 Keywords : doping * optical properties * synthesis * ZnO thin films Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.463, year: 2011

  10. Inner surface enhanced femtosecond second harmonic generation in thin ZnO crystal tubes

    OpenAIRE

    Xu, SJ; Ning, JQ; Che, CM; Zheng, CC; Zhang, SF; Wang, JY; Hao, JH

    2011-01-01

    At room temperature, efficient second harmonic generation (SHG) emission is observed in thin ZnO crystal hollow rods (tubes) with diameter∼0.2 mm under the excitation of femtosecond laser from 700 to 860 nm. Power and polarization dependence of the SHG signal on the primary excitation beam is also measured. The multiple total reflections between the outer and inner surfaces of the sample are analyzed to be responsible for the efficient SHG. Ninefold amplification of SHG signal in the tube str...

  11. Synthesis of ZnO Nanowires and Their Photovoltaic Application: ZnO Nanowires/AgGaSe2 Thin Film Core-Shell Solar Cell

    Directory of Open Access Journals (Sweden)

    Elif Peksu

    2015-01-01

    Full Text Available In this investigation, hydrothermal technique was employed for the synthesis of well-aligned dense arrays of ZnO nanowires (NWs on a wide range of substrates including silicon, soda-lime glass (SLG, indium tin oxide, and polyethylene terephthalate (PET. Results showed that ZnO NWs can be successfully grown on any substrate that can withstand the growth temperature (~90°C and precursor solution chemicals. Results also revealed that there was a strong impact of growth time and ZnO seed layer deposition route on the orientation, density, diameter, and uniformity of the synthesized nanowires. A core-shell n-ZnO NWs/p-AgGaSe2 (AGS thin film solar cell was fabricated as a device application of synthesized ZnO nanowires by decoration of nanowires with ~700 nm thick sputtering deposited AGS thin film layer, which demonstrated an energy conversion efficiency of 1.74% under 100 mW/cm2 of simulated solar illumination.

  12. Preparation of cadmium-doped ZnO thin films by SILAR and their characterization

    Indian Academy of Sciences (India)

    S Mondal; P Mitra

    2012-10-01

    Cadmium-doped zinc oxide (Cd : ZnO) thin films were deposited from sodium zincate bath following a chemical dipping technique called successive ion layer adsorption and reaction (SILAR). Structural characterization by X-ray diffraction reveals that polycrystalline nature of the films increases with increasing cadmium incorporation. Particle size evaluated using X-ray line broadening analysis shows decreasing trend with increasing cadmium impurification. The average particle size for pure ZnO is 36.73nm and it reduces to 29.9 nm for 10% Cd:ZnO, neglecting strain broadening. The strong preferred c-axis orientation is lost due to cadmium doping and degree of polycrystallinity of the films also increases with increasing Cd incorporation. Incorporation of cadmium was confirmed from elemental analysis using EDX. The optical bandgap of the films decreases with increasing Cd dopant. The value of fundamental absorption edge is 3.18 eV for pure ZnO and it decreases to 3.11 eV for 10% Cd:ZnO.

  13. ZnO THIN FILMS PREPARED BY SPRAY-PYROLYSIS TECHNIQUE FROM ORGANO-METALLIC PRECURSOR

    Directory of Open Access Journals (Sweden)

    Martin Mikulics

    2012-07-01

    Full Text Available Presented experiments utilize methanolic solution of zinc acetyl-acetonate as a precursor and sapphire (001 as a substrate for deposition of thin films of ZnO. The X-ray diffraction analysis revealed polycrystalline character of prepared films with preferential growth orientation along c-axis. The roughness of prepared films was assessed by AFM microscopy and represented by roughness root mean square (RMS value in range of 1.8 - 433 nm. The surface morphology was mapped by scanning electron microscopy showing periodical structure with several local defects. The optical transmittance spectrum of ZnO films was measured in wavelength range of 200-1000 nm. Prepared films are transparent in visible range with sharp ultra-violet cut-off at approximately 370 nm. Raman spectroscopy confirmed wurtzite structure and the presence of compressive stress within its structure as well as the occurrence of oxygen vacancies. The four-point Van der Pauw method was used to study the transport prosperities. The resistivity of presented ZnO films was found 8 × 10–2 Ω cm with carrier density of 1.3 × 1018 cm–3 and electron mobility of 40 cm2 V–1 s–1.

  14. Effect of doping concentration on the conductivity and optical properties of p-type ZnO thin films

    Science.gov (United States)

    Pathak, Trilok Kumar; Kumar, Vinod; Swart, H. C.; Purohit, L. P.

    2016-01-01

    Nitrogen doped ZnO (NZO) thin films were synthesized on glass substrates by the sol-gel and spin coating method. Zinc acetate dihydrates and ammonium acetate were used as precursors for zinc and nitrogen, respectively. X-ray diffraction study showed that the thin films have a hexagonal wurtzite structure corresponding (002) peak for undoped and doped ZnO thin films. The transmittance of the films was above 80% and the band gap of the film varies from 3.21±0.03 eV for undoped and doped ZnO. The minimum resistivity of NZO thin films was obtained as 0.473 Ω cm for the 4 at% of nitrogen (N) doping with a mobility of 1.995 cm2/V s. The NZO thin films showed p-type conductivity at 2 and 3 at% of N doping. The AC conductivity measurements that were carried out in the frequency range 10 kHz to 0.1 MHz showed localized conduction in the NZO thin films. These highly transparent ZnO films can be used as a possible window layer in solar cells.

  15. Effects of cooling rate and post-heat treatment on properties of ZnO thin films deposited by sol-gel method

    International Nuclear Information System (INIS)

    Sol-gel spin-coated ZnO thin films are cooled with different rates after the pre-heat treatment. Atomic force microscopy (AFM), X-ray diffraction (XRD), Raman, and photoluminescence (PL) were carried out to investigate the effects of the cooling rate during pre-heat treatment on structural and optical properties of the ZnO thin films. The ZnO thin films cooled slowly exhibit mountain chain structure while the ones cooled rapidly have smooth surface. The ZnO thin films cooled rapidly have higher c-axis orientation compared to the ones cooled slowly. The narrower and the higher near-band-edge emission (NBE) peaks are observed in the ZnO thin films cooled rapidly.

  16. Near-infrared optical constants and optical polarization properties of ZnO thin films

    International Nuclear Information System (INIS)

    The optical characteristics of ZnO thin films deposited on Si (111) and quartz at temperature < 50 °C using reactive RF sputtering deposition were examined within the near-infrared (NIR) region. From the X-ray diffraction observations, it was found that the films show a polycrystalline structure. X-ray photoelectron spectroscopy analysis shows the chemical bonding states of zinc and oxygen in the surface of the films and confirms the formation of Zn–O bonds. The field emission scanning electron microscopy and the atomic force microscopy images of the films shown an almost uniform distribution and the surfaces are smooth with grains of the order of 40–60 nm. The average surface roughness was in the range of 3.15–24.33 nm. Over a wavelength range 700–2500 nm, the optical constants of the films were obtained by analysis of the measured ellipsometric spectra using the Cauchy–Urbach model. Refractive indices and extinction coefficients of the ZnO films were determined to be in the range n = 1.65–1.73 and κ = 0.0060–0.029, respectively. Also, the s- and p-polarized optical properties (transmittance and reflectance) of the films have been measured at different angles of incidence in the UV–Vis–NIR spectral range. In addition, calculations have been carried out in order to determine the optical absorptance by using the conservation of energy. The films reveal a high transmittance (85%–95%), low reflectance (5%–15%), and very low absorptance (< 1%) at normal incidence. This means that the sputtered polycrystalline ZnO films could be good candidates for antireflection (AR) optical coatings. - Highlights: • The ZnO films exhibited a polycrystalline structure. • The as-deposited ZnO films are homogeneous and continuous. • The Cauchy–Urbach model can represent sufficiently the films in the NIR range. • The films reveal a high transmittance, low reflectance and very low absorptance. • Polycrystalline ZnO films could be good candidates for

  17. Application of Thin ZnO ALD Layers in Fiber-Optic Fabry-Pérot Sensing Interferometers

    OpenAIRE

    Daria Majchrowicz; Marzena Hirsch; Paweł Wierzba; Michael Bechelany; Roman Viter; Małgorzata Jędrzejewska‑Szczerska

    2016-01-01

    In this paper we investigated the response of a fiber-optic Fabry-Pérot sensing interferometer with thin ZnO layers deposited on the end faces of the optical fibers forming the cavity. Standard telecommunication single-mode optical fiber (SMF-28) segments were used with the thin ZnO layers deposited by Atomic Layer Deposition (ALD). Measurements were performed with the interferometer illuminated by two broadband sources operating at 1300 nm and 1550 nm. Reflected interference signal was acqui...

  18. Effect of Nd3+ incorporation on the microstructure and chemical structure of RF sputtered ZnO thin films

    International Nuclear Information System (INIS)

    Highlights: ► Effects of Nd incorporation on ZnO thin films chemical and structural properties. ► Very low Nd concentrations were quantified by combining XRF and AES data. ► At low Nd concentration, Nd ions were successfully incorporated in the ZnO lattice. ► Structural changes turns up with increasing Nd doping level. ► At high Nd concentration, precipitation of a Nd2O3 separate phase occurs. -- Abstract: The present work aims at investigating the effects that different levels of Nd atoms incorporation can have on the microstructure and chemical structure of ZnO thin films. Undoped and Nd-doped ZnO films were deposited by RF co-sputtering from pure ZnO and metallic Nd targets in Ar plasma onto Si, quartz and glass substrates. The Nd concentration in the ZnO host matrix was varied in the range 0–26 at.% by varying the bias applied to the Nd target. A comprehensive characterization of the films properties was performed by X-ray photoelectron and Auger electron spectroscopies, X-ray fluorescence analysis, X-ray diffraction and scanning electron microscopy. At low Nd atomic concentration (Nd/Zn 2O3

  19. Influence of hydrogen on the structure and stability of ultra-thin ZnO on metal substrates

    Energy Technology Data Exchange (ETDEWEB)

    Bieniek, Bjoern [Fritz-Haber-Institut der Max-Planck-Gesellschaft, 14195 Berlin (Germany); Hofmann, Oliver T. [Fritz-Haber-Institut der Max-Planck-Gesellschaft, 14195 Berlin (Germany); Institut für Festkörperphysik, TU Graz, 8010 Graz (Austria); Rinke, Patrick, E-mail: patrick.rinke@aalto.fi [Fritz-Haber-Institut der Max-Planck-Gesellschaft, 14195 Berlin (Germany); School of Science, Aalto University, FI-00076 Aalto (Finland)

    2015-03-30

    We investigate the atomic and electronic structure of ultra-thin ZnO films (1 to 4 layers) on the (111) surfaces of Ag, Cu, Pd, Pt, Ni, and Rh by means of density-functional theory. The ZnO monolayer is found to adopt an α-BN structure on the metal substrates with coincidence structures in good agreement with experiment. Thicker ZnO layers change into a wurtzite structure. The films exhibit a strong corrugation, which can be smoothed by hydrogen (H) adsorption. An H over-layer with 50% coverage is formed at chemical potentials that range from low to ultra-high vacuum H{sub 2} pressures. For the Ag substrate, both α-BN and wurtzite ZnO films are accessible in this pressure range, while for Cu, Pd, Pt, Rh, and Ni wurtzite films are favored. The surface structure and the density of states of these H passivated ZnO thin films agree well with those of the bulk ZnO(0001{sup ¯})-2×1-H surface.

  20. Analysis of stability improvement in ZnO thin film transistor with dual-gate structure under negative bias stress

    Science.gov (United States)

    Yun, Ho-Jin; Kim, Young-Su; Jeong, Kwang-Seok; Kim, Yu-Mi; Yang, Seung-dong; Lee, Hi-Deok; Lee, Ga-Won

    2014-01-01

    In this study, we fabricated dual-gate zinc oxide thin film transistors (ZnO TFTs) without additional processes and analyzed their stability characteristics under a negative gate bias stress (NBS) by comparison with conventional bottom-gate structures. The dual-gate device shows superior electrical parameters, such as subthreshold swing (SS) and on/off current ratio. NBS of VGS = -20 V with VDS = 0 was applied, resulting in a negative threshold voltage (Vth) shift. After applying stress for 1000 s, the Vth shift is 0.60 V in a dual-gate ZnO TFT, while the Vth shift is 2.52 V in a bottom-gate ZnO TFT. The stress immunity of the dual-gate device is caused by the change in field distribution in the ZnO channel by adding another gate as the technology computer aided design (TCAD) simulation shows. Additionally, in flicker noise analysis, a lower noise level with a different mechanism is observed in the dual-gate structure. This can be explained by the top side of the ZnO film having a larger crystal and fewer grain boundaries than the bottom side, which is revealed by the enhanced SS and XRD results. Therefore, the improved stability of the dual-gate ZnO TFT is greatly related to the E-field cancellation effect and crystal quality of the ZnO film.

  1. Preparation and characterization of Mg-doped ZnO thin films by sol-gel method

    Energy Technology Data Exchange (ETDEWEB)

    Huang Kai; Tang Zhen; Zhang Li; Yu Jiangyin [Department of Mathematics and Physics, Anhui University of Architecture, Hefei 230601 (China); Lv Jianguo, E-mail: jglv@hftc.edu.cn [Department of Physics and Electronic Engineering, Hefei Normal University, Hefei 230601 (China); Liu Xiansong [School of Physics and Material Science, Anhui University, Hefei 230039 (China); Liu Feng [School of Mathematics and Physics, Anhui Polytechnic University, Wuhu 241000 (China)

    2012-02-01

    Undoped and Mg-doped ZnO thin films were deposited on Si(1 0 0) and quartz substrates by the sol-gel method. The thin films were annealed at 873 K for 60 min. Microstructure, surface topography and optical properties of the thin films have been measured by X-ray diffraction (XRD), atomic force microscope (AFM), UV-vis spectrophotometer, and fluorophotometer (FL), respectively. The XRD results show that the polycrystalline with hexagonal wurtzite structure are observed for the ZnO thin film with Mg:Zn = 0.0, 0.02, and 0.04, while a secondary phase of MgO is evolved for the thin film with Mg:Zn = 0.08. The ZnO:Mg-2% thin film exhibits high c-axis preferred orientation. AFM studies reveal that rms roughness of the thin films changes from 7.89 nm to 16.9 nm with increasing Mg concentrations. PL spectra show that the UV-violet emission band around 386-402 nm and the blue emission peak about 460 nm are observed. The optical band gap calculated from absorption spectra and the resistivity of the ZnO thin films increase with increasing Mg concentration. In addition, the effects of Mg concentrations on microstructure, surface topography, PL spectra and electrical properties are discussed.

  2. Characterization of piesoelectric ZnO thin films and the fabrication of piezoelectric micro-cantilevers

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Raegan Lynn

    2005-08-01

    In Atomic Force Microscopy (AFM), a microcantilever is raster scanned across the surface of a sample in order to obtain a topographical image of the sample's surface. In a traditional, optical AFM, the sample rests on a bulk piezoelectric tube and a control loop is used to control the tip-sample separation by actuating the piezo-tube. This method has several disadvantages--the most noticeable one being that response time of the piezo-tube is rather long which leads to slow imaging speeds. One possible solution aimed at improving the speed of imaging is to incorporate a thin piezoelectric film on top of the cantilever beam. This design not only improves the speed of imaging because the piezoelectric film replaces the piezo-tube as an actuator, but the film can also act as a sensor. In addition, the piezoelectric film can excite the cantilever beam near its resonance frequency. This project aims to fabricate piezoelectric microcantilevers for use in the AFM. Prior to fabricating the cantilevers and also part of this project, a systematic study was performed to examine the effects of deposition conditions on the quality of piezoelectric ZnO thin films deposited by RF sputtering. These results will be presented. The deposition parameters that produced the highest quality ZnO film were used in the fabrication of the piezoelectric cantilevers. Unfortunately, the fabricated cantilevers warped due to the intrinsic stress of the ZnO film and were therefore not usable in the AFM. The complete fabrication process will be detailed, the results will be discussed and reasons for the warping will be examined.

  3. Polycrystalline ZnO: B grown by LPCVD as TCO for thin film silicon solar cells

    International Nuclear Information System (INIS)

    Conductive zinc oxide (ZnO) grown by low pressure chemical vapor deposition (LPCVD) technique possesses a rough surface that induces an efficient light scattering in thin film silicon (TF Si) solar cells, which makes this TCO an ideal candidate for contacting such devices. IMT-EPFL has developed an in-house LPCVD process for the deposition of nanotextured boron doped ZnO films used as rough TCO for TF Si solar cells. This paper is a general review and synthesis of the study of the electrical, optical and structural properties of the ZnO:B that has been performed at IMT-EPFL. The influence of the free carrier absorption and the grain size on the electrical and optical properties of LPCVD ZnO:B is discussed. Transport mechanisms at grain boundaries are studied. It is seen that high doping of the ZnO grains facilitates the tunnelling of the electrons through potential barriers that are located at the grain boundaries. Therefore, even if these potential barriers increase after an exposition of the film to a humid atmosphere, the heavily doped LPCVD ZnO:B layers show a remarkable stable conductivity. However, the introduction of diborane in the CVD reaction induces also a degradation of the intra-grain mobility and increases over-proportionally the optical absorption of the ZnO:B films. Hence, the necessity to finely tune the doping level of LPCVD ZnO:B films is highlighted. Finally, the next challenges to push further the optimization of LPCVD ZnO:B films for thin film silicon solar cells are discussed, as well as some remarkable record cell results achieved with LPCVD ZnO:B as front electrode.

  4. Polycrystalline ZnO: B grown by LPCVD as TCO for thin film silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Fay, Sylvie, E-mail: Sylvie.fay@epfl.c [Ecole Polytechnique Federale de Lausanne (EPFL), Institute of Microengineering (IMT), Photovoltaics and Thin Film Electronics Laboratory, Breguet 2, 2000 Neuchatel (Switzerland); Steinhauser, Jerome [Now at Oerlikon Solar Lab, Neuchatel CH-2000 (Switzerland); Nicolay, Sylvain; Ballif, Christophe [Ecole Polytechnique Federale de Lausanne (EPFL), Institute of Microengineering (IMT), Photovoltaics and Thin Film Electronics Laboratory, Breguet 2, 2000 Neuchatel (Switzerland)

    2010-03-31

    Conductive zinc oxide (ZnO) grown by low pressure chemical vapor deposition (LPCVD) technique possesses a rough surface that induces an efficient light scattering in thin film silicon (TF Si) solar cells, which makes this TCO an ideal candidate for contacting such devices. IMT-EPFL has developed an in-house LPCVD process for the deposition of nanotextured boron doped ZnO films used as rough TCO for TF Si solar cells. This paper is a general review and synthesis of the study of the electrical, optical and structural properties of the ZnO:B that has been performed at IMT-EPFL. The influence of the free carrier absorption and the grain size on the electrical and optical properties of LPCVD ZnO:B is discussed. Transport mechanisms at grain boundaries are studied. It is seen that high doping of the ZnO grains facilitates the tunnelling of the electrons through potential barriers that are located at the grain boundaries. Therefore, even if these potential barriers increase after an exposition of the film to a humid atmosphere, the heavily doped LPCVD ZnO:B layers show a remarkable stable conductivity. However, the introduction of diborane in the CVD reaction induces also a degradation of the intra-grain mobility and increases over-proportionally the optical absorption of the ZnO:B films. Hence, the necessity to finely tune the doping level of LPCVD ZnO:B films is highlighted. Finally, the next challenges to push further the optimization of LPCVD ZnO:B films for thin film silicon solar cells are discussed, as well as some remarkable record cell results achieved with LPCVD ZnO:B as front electrode.

  5. Resistive switching behavior of RF magnetron sputtered ZnO thin films

    Science.gov (United States)

    Rajalakshmi, R.; Angappane, S.

    2015-06-01

    The resistive switching characteristics of RF magnetron sputtered zinc oxide thin films have been studied. The x-ray diffraction studies confirm the formation of crystalline ZnO on Pt/TiO2/SiOx/Si substrate. We have fabricated Cu/ZnO/Pt device using a shadow masking technique for resistive switching study. Our Cu/ZnO/Pt device exhibits a unipolar resistive switching behaviour. The switching observed in our device could be related to oxygen vacancies or Cu ions that generate the conducting filaments responsible for resistive switching. We found HRS to LRS resistance ratio of as high as ˜200 for our Cu/ZnO/Pt device. The higher resistance ratio and stability of Cu/ZnO/Pt device would make our RF magnetron sputtered zinc oxide thin films suitable for non volatile memory applications.

  6. Characterization of ZnO Nanorods and SnO2-CuO Thin Film for CO Gas Sensing

    Directory of Open Access Journals (Sweden)

    Woo-Chang Choi

    2012-12-01

    Full Text Available In this study, ZnO nanorods and SnO2-CuO heterogeneous oxide were grown on membrane-type gas sensor platformsand the sensing characteristics for carbon monoxide (CO were studied. Diaphragm-type gas sensor platforms withbuilt-in Pt micro-heaters were made using a conventional bulk micromachining method. ZnO nanorods were grownfrom ZnO seed layers using the hydrothermal method, and the average diameter and length of the nanorods wereadjusted by changing the concentration of the precursor. Thereafter, SnO2-CuO heterogeneous oxide thin films weregrown from evaporated Sn and Cu thin films. The average diameters of the ZnO nanorods obtained by changing theconcentration of the precursor were between 30 and 200 nm and the ZnO nanorods showed a sensitivity value of 21%at a working temperature of 350℃ and a carbon monoxide concentration of 100 ppm. The SnO2-CuO heterogeneousoxide thin films showed a sensitivity value of 18% at a working temperature of 200℃ and a carbon monoxideconcentration of 100 ppm.

  7. Structural, optical and electrical properties of ZnO thin films prepared by spray pyrolysis: Effect of precursor concentration

    Indian Academy of Sciences (India)

    F Zahedi; R S Dariani; S M Rozati

    2014-05-01

    ZnO thin films have been prepared using zinc acetate precursor by spray pyrolytic decomposition of zinc acetate on glass substrates at 450 °C. Effect of precursor concentration on structural and optical properties has been investigated. ZnO films are polycrystalline with (002) plane as preferential orientation. The optical transmission spectrum shows that transmission increases with decrease in the concentration and the maximum transmission in visible region is about 95% for ZnO films prepared with 0.1 M. The direct band-gap value decreases from 3.37 to 3.19 eV, when the precursor concentration increases from 0.1 to 0.4 M. Photoluminescence spectra at room temperature show an ultraviolet (UV) emission at 3.26 eV and two visible emissions at 2.82 and 2.38 eV. Lowest resistivity is obtained at 2.09 cm for 0.3 M. The current–voltage characteristic of the ZnO thin films were measured in dark and under UV illumination. The values of photocurrent and photoresponsivity at 5 V are increased with increase in precursor concentration and reaches to maximum value of 1148 A and 0.287 A/W, respectively which is correlated to structural properties of ZnO thin films.

  8. Co doping induced structural and optical properties of sol–gel prepared ZnO thin films

    International Nuclear Information System (INIS)

    Highlights: • Transparent metal oxides are related to ZnO. • Optical transmission spectrum of Co doped ZnO thin films. • Determination of optical band gap using photoluminescence measurement. • Deposition thin film by using ultrasonic spray pyrolysis. - Abstract: The preparation conditions for Co doping process into the ZnO structure were studied by the ultrasonic spray pyrolysis technique. Structural and optical properties of the Co:ZnO thin films as a function of Co concentrations were examined. It was observed that hexagonal wurtzite structure of ZnO is dominant up to the critical value, and after the value, the cubic structural phase of the cobalt oxide appears in the X-ray diffraction patterns. Every band-edge of Co:ZnO films shifts to the lower energies and all are confirmed with the PL measurements. Co substitution in ZnO lattice has been proved by the optical transmittance measurement which is observed as the loss of transmission appearing in specific region due to Co2+ characteristic transitions

  9. Fabrication and characterization of ZnO nanowires by wet oxidation of Zn thin film deposited on Teflon substrate

    Science.gov (United States)

    Farhat, O. F.; Halim, M. M.; Abdullah, M. J.; Ali, M. K. M.; Ahmed, Naser M.; Bououdina, M.

    2015-10-01

    In this study, ZnO nanowires (NWs) were successfully grown for the first time on to Teflon substrate by a wet oxidation of a Zn thin film coated by RF sputtering technique. The sputtered Zn thin film was oxidized at 100 °C for 5 h under water-vapour using a horizontal furnace. This oxidation process transformed Zn thin film into ZnO with wire-like nanostructure. XRD analysis confirms the formation of single nanocrystalline ZnO phase having a low compressive strain. FESEM observations reveal high density of ZnO NWs with diameter ranging from 34 to 52 nm and length about 2.231 μm, which are well distributed in different direction. A flexible ZnO NWs-based metal-semiconductor-metal UV photodetector was fabricated. Photo-response and sensitivity measurements under low power illumination (375 nm, 1.5 mW/cm2) showed a high sensitivity of 2050%, which can be considered a relatively fast response and baseline recovery for UV detection.

  10. A comparison between different ohmic contacts for ZnO thin films

    International Nuclear Information System (INIS)

    There are several metals that form ohmic contacts for ZnO thin films, such as copper, aluminum and silver. The aim of this work is to make a comparison between these ohmic contacts. To achieve this purpose, polycrystalline ZnO thin films were prepared by the spray pyrolysis technique, and characterized by the I–V measurements at room temperature. Two strips of each metal were thermally evaporated on the surface of the film and measurements were first recorded in the dark and room light, then in the dark before and after annealing for Al, which was found to be the best in the set. Films with aluminum contacts gave the smallest resistivity, best ohmicity and they are slightly affected by light as required. On the other hand, copper was found to be the worst, and films with copper contacts gave the largest resistivity, worst ohmicity and they are the most affected by light. Annealing improved the aluminum contacts due to alloying and doping. (paper)

  11. ZnO transparent conductive oxide for thin film silicon solar cells

    Science.gov (United States)

    Söderström, T.; Dominé, D.; Feltrin, A.; Despeisse, M.; Meillaud, F.; Bugnon, G.; Boccard, M.; Cuony, P.; Haug, F.-J.; Faÿ, S.; Nicolay, S.; Ballif, C.

    2010-03-01

    There is general agreement that the future production of electric energy has to be renewable and sustainable in the long term. Photovoltaic (PV) is booming with more than 7GW produced in 2008 and will therefore play an important role in the future electricity supply mix. Currently, crystalline silicon (c-Si) dominates the market with a share of about 90%. Reducing the cost per watt peak and energy pay back time of PV was the major concern of the last decade and remains the main challenge today. For that, thin film silicon solar cells has a strong potential because it allies the strength of c-Si (i.e. durability, abundancy, non toxicity) together with reduced material usage, lower temperature processes and monolithic interconnection. One of the technological key points is the transparent conductive oxide (TCO) used for front contact, barrier layer or intermediate reflector. In this paper, we report on the versatility of ZnO grown by low pressure chemical vapor deposition (ZnO LP-CVD) and its application in thin film silicon solar cells. In particular, we focus on the transparency, the morphology of the textured surface and its effects on the light in-coupling for micromorph tandem cells in both the substrate (n-i-p) and superstrate (p-i-n) configurations. The stabilized efficiencies achieved in Neuchâtel are 11.2% and 9.8% for p-i-n (without ARC) and n-i-p (plastic substrate), respectively.

  12. Synthesis of Various Nanopatterns of ZnO Thin Film Using Sol Gel Method

    Science.gov (United States)

    Julia, Sri; Yuliarto, Brian; Nugraha

    2010-10-01

    In order to achieve the different types of nanostructures of Zinc Oxide thin film using the low cost method, this research applied sol gel method and varying volume of solvent composition as the parameter. The volume of solvent composition was varying in amount of 75% distilled water + 25% ethanol, 50% distilled water + ethanol, and 25% distilled water + 75% ethanol. These compositions yield the different in pH value of solution, consequently yield the different of nanopatterns. Other parameter which also used is varying the substrates. In this investigation, kind of substrates used were glass, alumina and silicon. Through these parameters, the morphology of ZnO thin films was formed in various nanopatterns and observed by X-ray diffraction (XRD) and Scanning Electron Microscopic (SEM). X-ray diffraction determined all of the grown films are true ZnO, with wurtzite hexagonal crystal phase. Various patterns that obtained from SEM investigation are nanorod, flowerlike, nanoball and nanofiber. Uniquely, our flowerlike structure is arranged by nanosheet and nanofiber. The particle size of nanorods and nanoballs is about ±250 nm, while particle size of nanosheets is found to be ±500 nm and nanofiber is in the range of ± hundreds nm.

  13. Optical analysis of doped ZnO thin films using nonparabolic conduction-band parameters

    Science.gov (United States)

    Kim, J. S.; Jeong, J.-h.; Park, J. K.; Baik, Y. J.; Kim, I. H.; Seong, T.-Y.; Kim, W. M.

    2012-06-01

    The optical properties of impurity doped ZnO thin films were analyzed by taking into account the nonparabolicity in the conduction-band and the optically determined carrier concentration and mobility were correlated with those measured by Hall measurement. The Drude parameters obtained by applying a simple Drude model combined with the Lorentz oscillator model for the optical transmittance and reflectance spectrum were analyzed by using the carrier density dependent bare band effective mass determined by the first-order nonparabolicity approximation. The squared plasma energy multiplied by the carrier density dependent effective mass yielded fairly linear relationship with respect to the carrier concentration in wide carrier density range of 1019 - 1021 cm-3, verifying the applicability of the nonparabolicity parameter for various types of impurity doped ZnO thin films. The correlation between the optical and Hall analyses was examined by taking the ratios of optical to Hall measurements for carrier density, mobility, and resistivity by introducing a parameter, Rdl, which represents the ratio of the resistances to electron transport from the inside of the lattice and from the crystallographic defects. For both the carrier concentration and mobility, the ratios of optical to Hall measurements were shown to exhibit a monotonically decreasing function of Rdl, indicating that the parameter Rdl could be used as a yardstick in correlating the optically determined carrier density and mobility with those measured by Hall analysis.

  14. Auger and photoluminescence analysis of ZnO nanowires grown on AlN thin film

    Energy Technology Data Exchange (ETDEWEB)

    Yousefi, Ramin, E-mail: yousefi.ramin@gmail.com [Solid State Laboratory, Department of Physics, University of Malaya, 50603 Kuala Lumpur (Malaysia); Kamaluddin, Burhanuddin [Solid State Laboratory, Department of Physics, University of Malaya, 50603 Kuala Lumpur (Malaysia); Ghoranneviss, Mahmood; Hajakbari, Fatemeh [Plasma Physics Research Center, Science and Research Campus, Islamic Azad University, 14665-678 Tehran (Iran, Islamic Republic of)

    2009-05-15

    ZnO nanowires were grown on AlN thin film deposited on the glass substrates using a physical vapor deposition method in a conventional tube furnace without introducing any catalysts. The temperature of the substrates was maintained between 500 and 600 deg. C during the growth process. The typical average diameters of the obtained nanowires on substrate at 600 and 500 deg. C were about 57 and 22 nm respectively with several micrometers in length. X-ray diffraction and Auger spectroscopy results showed Al diffused from AlN thin film into the ZnO nanowires for the sample grown at 600 deg. C. Photoluminescence of the nanowires exhibits appearance of two emission bands, one related to ultraviolet emission with a strong peak at 380-382 nm, and the other related to deep level emission with a weak peak at 503-505 nm. The ultraviolet peak of the nanowires grown at 500 deg. C was blue shifted by 2 nm compared to those grown at 600 deg. C. This shift could be attributed to surface effect.

  15. Substrate Temperature Effects on Room Temperature Sensing Properties of Nanostructured ZnO Thin Films.

    Science.gov (United States)

    Reddy, Jonnala Rakesh; Mani, Ganesh Kumar; Shankar, Prabakaran; Rayappan, John Bosco Balaguru

    2016-01-01

    Zinc oxide (ZnO) thin films were deposited on glass substrates using chemical spray pyrolysis technique at different substrate temperatures such as 523, 623 and 723 K. X-ray diffraction (XRD) patterns confirmed the formation of polycrystalline films with hexagonal wurtzite crystal structure and revealed the change in preferential orientation of the crystal planes. Scanning electron micrographs showed the formation of uniformly distributed spherical shaped grains at low deposition temperature and pebbles like structure at the higher temperature. Transmittance of 85% was observed for the film deposited at 723 K. The band gap of the films was found to be increased from 3.15 to 3.23 eV with a rise in deposition temperature. The electrical conductivity of the films was found to be improved with an increase in substrate temperature. Surface of ZnO thin films deposited at 523 K, 623 K and 723 K were found to be hydrophobic with the contact angles of 92°, 105° and 128° respectively. The room temperature gas sensing characteristics of all the films were studied and found that the film deposited at 623 K showed a better response towards ammonia vapour. PMID:27398478

  16. Effect of different sol concentrations on the properties of nanocrystalline ZnO thin films grown on FTO substrates by sol-gel spin-coating

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ikhyun; Kim, Younggyu; Nam, Giwoong; Kim, Dongwan; Park, Minju; Kim, Haeun; Lee, Wookbin; Leem, Jaeyoung [Inje University, Gimhae (Korea, Republic of); Kim, Jongsu [Yeungnam University, Gyeongsan (Korea, Republic of); Kim, Jin Soo [Chonbuk National University, Jeonju (Korea, Republic of)

    2014-08-15

    Nanocrystalline ZnO thin films grown on fluorine-doped tinoxide (FTO) substrates were fabricated using the spin-coating method. The structural and the optical properties of the ZnO thin films prepared using different sol concentrations were investigated by using field-emission scanning electron microscopy (FE-SEM), X-ray diffractometry (XRD), photoluminescence (PL) measurements, and ultraviolet-visible (UV-vis) spectrometry. The surface morphology of the ZnO thin films, as observed in the SEM images, exhibited a mountain-chain structure. XRD results indicated that the thin films were preferentially orientated along the direction of the c-axis and that the grain size of the ZnO thin films increased with increasing sol concentration. The PL spectra showed a strong ultraviolet emission peak at 3.22 eV and a broad orange emission peak at 2.0 eV. The intensities of deep-level emission (DLE) gradually increased with increasing sol concentration from 0.4 to 1.0 M. The transmittance spectra of the ZnO thin films showed that the ZnO thin films were transparent (∼85%) in the visible region and exhibited sharp absorption edges at 375 nm. Thus, The Urbach energy of ZnO thin films decreased with increasing sol concentration.

  17. The porous nature of ZnO thin films deposited by sol-gel Spin-Coating technique

    Science.gov (United States)

    Karyaoui, M.; Ben Jaballah, A.; Mechiak, R.; Chtourou, R.

    2012-02-01

    Zinc oxide (ZnO) thin films were deposited on silicon and quartz substrates, by sol-gel method, using zinc acetate dehydrate [Zn(CH3COO)2.2H2O] dissolved in isopropanol and glycerol. The structural, morphologic and optical properties of ZnO thin films subsequently annealed at 700°C in air for 30 min have leads to a porous nature of these films. To calculate, the refraction index and the extinction coefficient values, Cauchy formalism is used to evaluate the Spectroscopic Ellipsometry results. Two distinct configurations were proposed for each sample: in the first, the film is considered as mixture of randomly distributed voids and ZnO crystallites while in the second, the effect of porosity gradient is highlighted. This optical analysis gives a better agreement between experiment and theory for a wide range of wavelengths regarding the second configuration.

  18. Quality improvement of ZnO thin layers overgrown on Si(100 substrates at room temperature by nitridation pretreatment

    Directory of Open Access Journals (Sweden)

    Peng Wang

    2012-06-01

    Full Text Available To improve the quality of ZnO thin film overgrown on Si(100 substrate at RT (room temperature, the Si(100 surface was pretreated with different methods. The influence of interface on the overgrown ZnO layers was investigated by atomic force microscopy, photoluminescence and X-ray diffraction. We found that the nitridation pretreatment could significantly improve the quality of RT ZnO thin film through two-fold effects: one was to buffer the big lattice mismatch and ease the stress resulted from heterojunction growth; the other was to balance the interface charge, block the symmetric inheritance from the cubic Si (100 substrate and thus restrain the formation of zincblende phase.

  19. Thermoelectric properties of Al doped Mg2Si material

    International Nuclear Information System (INIS)

    In the present paper we have calculated thermoelectric properties of Al doped Mg2Si material (Mg2−xAlxSi, x=0.06) using Pseudo potential plane wave method based on DFT and Semi classical Boltzmann theory. The calculations showed n-type conduction, indicating that the electrical conduction are due to electron. The electrical conductivity increasing with increasing temperature and the negative value of Seebeck Coefficient also show that the conduction is due to electron. The thermal conductivity was increased slightly by Al doping with increasing temperature due to the much larger contribution of lattice thermal conductivity over electronic thermal conductivity

  20. Aluminum doping tunes band gap energy level as well as oxidative stress-mediated cytotoxicity of ZnO nanoparticles in MCF-7 cells

    Science.gov (United States)

    Akhtar, Mohd Javed; Alhadlaq, Hisham A.; Alshamsan, Aws; Majeed Khan, M. A.; Ahamed, Maqusood

    2015-09-01

    We investigated whether Aluminum (Al) doping tunes band gap energy level as well as selective cytotoxicity of ZnO nanoparticles in human breast cancer cells (MCF-7). Pure and Al-doped ZnO nanoparticles were prepared by a simple sol-gel method. Characterization study confirmed the formation of single phase of AlxZn1-xO nanocrystals with the size range of 33-55 nm. Al-doping increased the band gap energy of ZnO nanoparticles (from 3.51 eV for pure to 3.87 eV for Al-doped ZnO). Al-doping also enhanced the cytotoxicity and oxidative stress response of ZnO nanoparticles in MCF-7 cells. The IC50 for undoped ZnO nanoparticles was 44 μg/ml while for the Al-doped ZnO counterparts was 31 μg/ml. Up-regulation of apoptotic genes (e.g. p53, bax/bcl2 ratio, caspase-3 & caspase-9) along with loss of mitochondrial membrane potential suggested that Al-doped ZnO nanoparticles induced apoptosis in MCF-7 cells through mitochondrial pathway. Importantly, Al-doping did not change the benign nature of ZnO nanoparticles towards normal cells suggesting that Al-doping improves the selective cytotoxicity of ZnO nanoparticles toward MCF-7 cells without affecting the normal cells. Our results indicated a novel approach through which the inherent selective cytotoxicity of ZnO nanoparticles against cancer cells can be further improved.

  1. Study of p-type ZnO and MgZnO Thin Films for Solid State Lighting

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jianlin [University of California, Riverside

    2016-03-31

    This project on study of p-type ZnO and MgZnO thin films for solid state lighting was carried out by research group of Prof. Jianlin Liu of UCR during the four-year period between August 2011 and July 2015. Tremendous progress has been made on the proposed research. This final report summarizes the important findings.

  2. Preparation and photocatalytic activity of Cu-doped ZnO thin films prepared by the sol-gel method

    Energy Technology Data Exchange (ETDEWEB)

    Jongnavakit, P. [Department of Chemistry and Center for Innovation in Chemistry, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112 (Thailand); Amornpitoksuk, P., E-mail: ampongsa@yahoo.com [Department of Chemistry and Center for Innovation in Chemistry, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112 (Thailand); NANOTEC Center of Excellence at Prince of Songkla University (CENE), Hat Yai, Songkhla 90112 (Thailand); Suwanboon, S. [Department of Materials Science and Technology, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112 (Thailand); NANOTEC Center of Excellence at Prince of Songkla University (CENE), Hat Yai, Songkhla 90112 (Thailand); Ndiege, N. [Nanoscience and Nanotechnology Institute, W181 Chemistry Building, University of Iowa, Iowa City 52242, IA (United States)

    2012-08-01

    Cu-doped ZnO thin films were fabricated on glass substrates by the sol-gel dip-coating method. All samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The grain size and film thickness of the Cu-doped ZnO thin film decreased as a function of the Cu concentrations. All prepared films showed a very high transmittance above 89% in the visible region (400-800 nm). Two oxidation states of Cu in +1 and +2 were identified in the ZnO thin film by X-ray photoelectron spectroscopy (XPS). Their photocatalytic activities were investigated by the degradation of methylene blue (MB) dye under blacklight fluorescent tubes. The film prepared from the Zn{sup 2+} solution containing 0.5 mol% of copper ions had the highest photocatalytic activity. The photocatalytic degradation of methylene blue solution as a function of the initial concentrations was evaluated according to the Langmuir-Hinshelwood model. The reaction rate (k) and adsorption equilibrium constant (K) over 1 cm{sup 2} of 0.5 mol% Cu-doped ZnO thin film are 15.92 {mu}M h{sup -1} and 0.049 {mu}M{sup -1}, respectively.

  3. Preparation and photocatalytic activity of Cu-doped ZnO thin films prepared by the sol-gel method

    International Nuclear Information System (INIS)

    Cu-doped ZnO thin films were fabricated on glass substrates by the sol-gel dip-coating method. All samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The grain size and film thickness of the Cu-doped ZnO thin film decreased as a function of the Cu concentrations. All prepared films showed a very high transmittance above 89% in the visible region (400-800 nm). Two oxidation states of Cu in +1 and +2 were identified in the ZnO thin film by X-ray photoelectron spectroscopy (XPS). Their photocatalytic activities were investigated by the degradation of methylene blue (MB) dye under blacklight fluorescent tubes. The film prepared from the Zn2+ solution containing 0.5 mol% of copper ions had the highest photocatalytic activity. The photocatalytic degradation of methylene blue solution as a function of the initial concentrations was evaluated according to the Langmuir-Hinshelwood model. The reaction rate (k) and adsorption equilibrium constant (K) over 1 cm2 of 0.5 mol% Cu-doped ZnO thin film are 15.92 μM h-1 and 0.049 μM-1, respectively.

  4. Structural, electrical and optical studies on spray-deposited aluminium-doped ZnO thin film

    Indian Academy of Sciences (India)

    S Tewari; A Bhattacharjee

    2011-01-01

    Thin films of zinc oxide (ZnO) were deposited on cleaned glass substrates by chemical spray pyrolysis technique using Zn(CH3COO)2 as precursor solution. Also, aluminium-doped thin films of ZnO were prepared by using AlCl3 as doping solution for aluminium. The dopant concentration [Al/Zn atomic percentage (at%)] was varied from 0 to 1.5 at% in thin films of ZnO prepared in different depositions. Structural characterization of the deposited films was performed with X-ray diffraction (XRD) studies. It confirmed that all the films were of zinc oxide having polycrystalline nature and possessing typical hexagonal wurtzite structure with crystallite size varying between 100.7 and 268.6 nm. The films exhibited changes in relative intensities and crystallite size with changes in the doping concentration of Al. The electrical studies established that 1 at% of Aldoping was the optimum for enhancing electrical conduction in ZnO thin films and beyond that the distortion caused in the lattice lowered the conductivity. The films also exhibited distinct changes in their optical properties at different doping concentrations, including a blue shift and slight widening of bandgap with increasing Al dopant concentration.

  5. Research update : Atmospheric pressure spatial atomic layer deposition of ZnO thin films : reactors, doping and devices

    OpenAIRE

    Hoye, Robert L.Z.; David Muñoz-Rojas; Nelson, Shelby F.; Andrea Illiberi; Paul Poodt; Fred Roozeboom; MacManus-Driscoll, Judith L

    2015-01-01

    Atmospheric pressure spatial atomic layer deposition (AP-SALD) has recently emerged as an appealing technique for rapidly producing high quality oxides. Here, we focus on the use of AP-SALD to deposit functional ZnO thin films, particularly on the reactors used, the film properties, and the dopants that have been studied. We highlight how these films are advantageous for the performance of solar cells, organometal halide perovskite light emitting diodes, and thin-film transistors. Future AP-S...

  6. Effect of surface microstructure and wettability on plasma protein adsorption to ZnO thin films prepared at different RF powers

    Energy Technology Data Exchange (ETDEWEB)

    Huang Zhanyun; Chen Min; Chen Dihu [State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-Sen University, Guangzhou 510275 (China); Pan Shirong, E-mail: stscdh@mail.sysu.edu.c [Artificial Heart Lab, the 1st Affiliate Hospital of Sun Yat-Sen University, Guangzhou 510080 (China)

    2010-10-01

    In this paper, the adsorption behavior of plasma proteins on the surface of ZnO thin films prepared by radio frequency (RF) sputtering under different sputtering powers was studied. The microstructures and surface properties of the ZnO thin films were investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible optical absorption spectroscopy and contact angle techniques. The results show that the ZnO thin films have better orientation of the (0 0 2) peak with increasing RF power, especially at around 160 W, and the optical band gap of the ZnO films varies from 3.2 to 3.4 eV. The contact angle test carried out by the sessile drop technique denoted a hydrophobic surface of the ZnO films, and the surface energy and adhesive work of the ZnO thin films decreased with increasing sputtering power. The amounts of human fibrinogen (HFG) and human serum albumin (HSA) adsorbing on the ZnO films and reference samples were determined by using enzyme-linked immunosorbent assay (ELISA). The results show that fewer plasma proteins and a smaller HFG/HSA ratio adsorb on the ZnO thin films' surface.

  7. Low-temperature-annealed alumina/polyimide gate insulators for solution-processed ZnO thin-film transistors

    International Nuclear Information System (INIS)

    Highlights: • The surface property of the polyimide gate insulator was successfully modified by the introduction of a low-temperature-annealed amorphous alumina interlayer. • The alumina/polyimide gate insulator showed excellent electrical insulating properties. • The solution-processed ZnO TFT with the alumina/polyimide gate insulator exhibited reasonable TFT performance. - Abstract: We report here a low-temperature-annealed alumina/polyimide gate insulator with excellent electrical insulating properties for solution-processed ZnO TFTs. In this study, 150 nm-thick polyimide and 20 nm-thick alumina thin films were deposited by a simple spin-coating followed by a 200 °C-annealing process. With the deposition of the alumina interlayer, the surface of the polyimide film was successfully modified. We prepared ZnO TFTs annealed at 230 °C to investigate the potential of the prepared gate insulator. The field-effect mobility and the on/off current ratio of solution-processed ZnO TFTs with an alumina/polyimide gate insulator were 0.11 cm2/V s and 1.8 × 105, respectively, whereas a ZnO TFT with a polyimide gate insulator was inactive. The alumina interlayer introduced here might provide a compatible interface for the ZnO semiconductor

  8. Growth of ZnO Thin Films on Lattice-Matched Substrates by Pulsed-Laser Deposition

    Institute of Scientific and Technical Information of China (English)

    余庆选; 徐波; 吴气虹; 廖源; 王冠中; 方容川

    2003-01-01

    ZnO films were grown on GaN and sapphire substrates by pulse laser deposition, respectively. The effects of crystalline quality on the optical properties in ZnO epitaxial layers were investigated by x-ray rocking curve and photoluminescence. The x-ray rocking curve of the film deposited on the GaN substrate has the full width half maximum (FWHM) of 0.45°, whereas the FWHM of the x-ray θ-rocking curve of the ZnO film deposited on a sapphire substrate was measured to be about 0.77°. In photoluminescence (PL) measurement, the intensity of UV photoluminescence for the ZnO film on the GaN substrate decreased by approximately two orders of magnitude in comparison with that of the ZnO film on sapphire. It is concluded that the UV luminescence intensity almost does not depend on the textured growth of the ZnO thin film.

  9. Sol-gel derived Al-Ga co-doped transparent conducting oxide ZnO thin films

    Science.gov (United States)

    Serrao, Felcy Jyothi; Sandeep, K. M.; Bhat, Shreesha; Dharmaprakash, S. M.

    2016-05-01

    Transparent conducting ZnO doped with Al, Ga and co-doped Al and Ga (1:1) (AGZO) thin films were grown on glass substrates by cost effective sol-gel spin coating method. The XRD results showed that all the films are polycrystalline in nature and highly textured along the (002) plane. Enhanced grain size was observed in the case of AGZO thin films. The transmittance of all the films was more than 83% in the visible region of light. The electrical properties such as carrier concentration and mobility values are increased in case of AGZO compared to that of Al and Ga doped ZnO thin films. The minimum resistivity of 2.54 × 10-3 Ω cm was observed in AGZO thin film. The co-doped AGZO thin films exhibited minimum resistivity and high optical transmittance, indicate that co-doped ZnO thin films could be used in transparent electronics mainly in display applications.

  10. Transparent and conductive Al/F and In co-doped ZnO thin films deposited by spray pyrolysis

    Science.gov (United States)

    Hadri, A.; Taibi, M.; El hat, A.; Mzerd, A.

    2016-02-01

    In doped ZnO (IZO), In-Al co-doped ZnO (IAZO) and In-F co-doped ZnO (IFZO) were deposited on glass substrates at 350 °C by spray pyrolysis technique. The structural, optical and electrical properties of as-deposited thin films were investigated and compared. A polycrystalline and (002) oriented wurtzite crystal structure was confirmed by X-ray patterns for all films; and the full width at half -maximum (FWHM) of (002) diffraction peak increased after co-doping. The investigation of the optical properties was performed using Uv-vis spectroscopy. The average transmittances of all the films were between 70 and 85%. Hall Effect measurements showed that the electrical conductivity of co-doped films increased as compared with IZO thin film. The highest conductivity of about 16.39 Ω-1 cm-1 was obtained for as-deposited IFZO thin film. In addition, the thin films were annealed at 350 °C for two hour under Ar atmosphere and their optical, electrical properties and the associated photoluminescence (PL) responses of selected films were analysed. After annealing, the electrical conductivity of all thin films was improved and the optical transmittance remained above 70%. Room temperature PL revealed that the annealed IAZO thin film had a strong green emission than that of IZO film.

  11. Microwave-assisted low temperature fabrication of ZnO thin film electrodes for solar energy harvesting

    International Nuclear Information System (INIS)

    Metallic Zn thin films were electrodeposited on fluorine-doped tin oxide (FTO) glass substrates and oxidized under air by conventional radiant and microwave post-annealing methods to obtain ZnO thin film electrodes. The temperature of each post-annealing method was varied systematically and the photoelectrochemical (PEC) performance of electrodes was evaluated. The best photocurrent density achieved by the conventional radiant annealing method at 425 °C for 15 min was 93 μA cm−2 at 1.23 V vs. NHE and the electrode showed an incident photon-to-electron conversion efficiency (IPCE) of 28.2%. X-ray diffractogram of this electrode showed that the oxidation of Zn to ZnO was not completed during the radiant annealing process as evident by the presence of metallic Zn in the electrode. For the electrode oxidized from Zn to ZnO under microwave irradiation, a photocurrent of 130 μA cm−2 at 1.23 V vs. NHE and IPCE of 35.6% was observed after annealing for just 3 min, during which the temperature reached 250 °C. The photocurrent was 40% higher for the microwave annealed sample; this increase was attributed to higher surface area by preserving the nanostructure, confirmed by SEM surface topographical analysis, and better conversion yields to crystalline ZnO. Overall, it was demonstrated that oxidation of Zn to ZnO can be accomplished by microwave annealing five times faster than that of conventional annealing, thus resulting in a ~ 75% power saving. This study shows that microwave processing of materials offers significant economic and performance advantages for industrial scale up. - Highlights: • Conversion of Zn to ZnO by microwave and radiant annealing was conducted. • Microwave conversion was 5 times faster compared to radiant annealing. • Photoelectrochemical performance of microwave annealed ZnO was 40% higher. • Microwave annealing results in a 75% energy saving

  12. Structural and Magnetic Properties of Mn doped ZnO Thin Film Deposited by Pulsed Laser Deposition

    KAUST Repository

    Baras, Abdulaziz

    2011-07-01

    Diluted magnetic oxide (DMO) research is a growing field of interdisciplinary study like spintronic devices and medical imaging. A definite agreement among researchers concerning the origin of ferromagnetism in DMO has yet to be reached. This thesis presents a study on the structural and magnetic properties of DMO thin films. It attempts to contribute to the understanding of ferromagnetism (FM) origin in DMO. Pure ZnO and Mn doped ZnO thin films have been deposited by pulsed laser deposition (PLD) using different deposition conditions. This was conducted in order to correlate the change between structural and magnetic properties. Structural properties of the films were characterized using x-ray diffraction (XRD) and scanning electron microscopy (SEM). The superconducting quantum interference device (SQUID) was used to investigate the magnetic properties of these films. The structural characterizations showed that the quality of pure ZnO and Mn doped ZnO films increased as oxygen pressure (PO) increased during deposition. All samples were insulators. In Mn doped films, Mn concentration decreased as PO increased. The Mn doped ZnO samples were deposited at 600˚C and oxygen pressure from 50-500mTorr. All Mn doped films displayed room temperature ferromagnetism (RTFM). However, at 5 K a superparamagnetic (SPM) behavior was observed in these samples. This result was accounted for by the supposition that there were secondary phase(s) causing the superparamagnetic behavior. Our findings hope to strengthen existing research on DMO origins and suggest that secondary phases are the core components that suppress the ferromagnetism. Although RTFM and SPM at low temperature has been observed in other systems (e.g., Co doped ZnO), we are the first to report this behavior in Mn doped ZnO. Future research might extend the characterization and exploration of ferromagnetism in this system.

  13. Synthesis and characterization of nanostructured undoped and Sn-doped ZnO thin films via sol–gel approach

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Sn-doped ZnO films were prepared via facile sol–gel spin coating method. • The grain size of the films changes from 39.23 to 71.84 nm with Sn doping. • The refractive index dispersion of the films obeys the single oscillator model. - Abstract: Thin films of Sn-doped ZnO were prepared via facile sol–gel spin coating method. The structural and optical properties of the films were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and UV-VIS-NIR spectrophotometer. The X-ray results confirmed that all the ZnO thin films are polycrystalline with a hexagonal wurtzite structure with a preferential orientation of (002) plane. The crystallite size and lattice parameter values of the films were obtained. Atomic force microscopy results indicate that the Sn-doped ZnO films have the nanostructure. The grain size values of the films were found to vary from 39.23 to 71.84 nm with Sn doping. The nanostructure of the Sn-doped ZnO films was also confirmed by scanning electron microcopy. The optical bandgaps of the films were calculated for the various Sn contents. The refractive index dispersion curves obey the single oscillator model. The optical constants and dispersion parameters of the ZnO films were changed with Sn doping. The obtained results suggest that the structural and optical properties of ZnO films can be controlled by Sn doping

  14. Synthesis and characterization of nanostructured undoped and Sn-doped ZnO thin films via sol–gel approach

    Energy Technology Data Exchange (ETDEWEB)

    Aydin, H., E-mail: cihataydin_26@hotmail.com [Department of Metallurgical and Materials Engineering, Engineering Faculty, Tunceli University, Tunceli 62000 (Turkey); El-Nasser, H.M. [Department of Physics, Al al-Bayt University, Mafraq (Jordan); Aydin, C. [Department of Metallurgy and Materials Engineering, Faculty of Technology, Firat University, Elazig 23119 (Turkey); Al-Ghamdi, Ahmed A. [Department of Physics, Faculty of Science, King Abdulaziz University, Jeddah 21589 (Saudi Arabia); Yakuphanoglu, F. [Department of Physics, Faculty of Science, King Abdulaziz University, Jeddah 21589 (Saudi Arabia); Department of Physics, Faculty of Science, Firat University, Elazig 23119 (Turkey); Nanoscience and Nanotechnology Laboratory, Firat University, Elazig 23119 (Turkey)

    2015-09-30

    Graphical abstract: - Highlights: • Sn-doped ZnO films were prepared via facile sol–gel spin coating method. • The grain size of the films changes from 39.23 to 71.84 nm with Sn doping. • The refractive index dispersion of the films obeys the single oscillator model. - Abstract: Thin films of Sn-doped ZnO were prepared via facile sol–gel spin coating method. The structural and optical properties of the films were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and UV-VIS-NIR spectrophotometer. The X-ray results confirmed that all the ZnO thin films are polycrystalline with a hexagonal wurtzite structure with a preferential orientation of (002) plane. The crystallite size and lattice parameter values of the films were obtained. Atomic force microscopy results indicate that the Sn-doped ZnO films have the nanostructure. The grain size values of the films were found to vary from 39.23 to 71.84 nm with Sn doping. The nanostructure of the Sn-doped ZnO films was also confirmed by scanning electron microcopy. The optical bandgaps of the films were calculated for the various Sn contents. The refractive index dispersion curves obey the single oscillator model. The optical constants and dispersion parameters of the ZnO films were changed with Sn doping. The obtained results suggest that the structural and optical properties of ZnO films can be controlled by Sn doping.

  15. Electrical and optical properties of ZnO:Al thin films prepared by the spray pyrolysis technique

    International Nuclear Information System (INIS)

    Highly transparent conducting ZnO:Al thin films have been produced by the spray pyrolysis technique on glass substrates at a substrate temperature Ts=450 deg. C by a home-made spraying system. The electrical and optical properties of the films were investigated at room temperature before and after annealing in nitrogen atmosphere. The electrical properties were studied by recording and analyzing the I-V measurements. All the curves were linear, so the resistivity was estimated from the slopes. The resistivity was found to be 133 Ω cm for the undoped ZnO films, but 90 Ω cm for the Al-doped films before annealing and 84 Ω cm after annealing. The optical properties were investigated by measuring the transmittance curves that were used to find the optical bandgap energy. The bandgap energy was found to be 3.27 eV for the undoped ZnO films and 3.28 eV for the Al-doped ZnO films before and after annealing. Therefore the electro-optical properties of the films had improved with Al doping and annealing in nitrogen atmosphere.

  16. Role of growth temperature on the structural, optical and electrical properties of ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Ashish, E-mail: dr.akmr@gmail.com [Materials Science Division, Inter University Accelerator Centre, New Delhi, 110067 (India); Kumar, Parmod [Materials Science Division, Inter University Accelerator Centre, New Delhi, 110067 (India); Kumar, Kaushal [Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Roorkee, 247667 (India); Singh, Trilok [Graduate School of Engineering, Toin University of Yokohama, 1614 Kurogane-cho, Aoba, Yokohama, Kanagawa 225-8503 (Japan); Singh, R. [Department of Physics, Indian Institute of Technology, New Delhi, 110016 (India); Asokan, K.; Kanjilal, D. [Materials Science Division, Inter University Accelerator Centre, New Delhi, 110067 (India)

    2015-11-15

    Present study focuses on the influence of growth temperature on electrical and optical properties of polycrystalline ZnO thin films on sapphire substrates grown by atomic layer deposition technique. Dimethylzinc and de-ionized water were used as precursors by varying the growth temperature ranging from 70 to 130 °C. X-ray diffraction pattern confirms the formation of hexagonal wurtzite phase of ZnO with preferred (103) orientation. AFM results infer the growth of good quality films with root mean square roughness ∼1 nm for all these films having same thickness. The free carrier concentration and mobility of samples is found to increase whereas resistivity decreases with increasing growth temperature. The electrical results are well corroborated on the basis of photoluminescence and X-ray photoelectron spectroscopy. Photoluminescence and Raman measurements show that these ZnO thin films have very low defect concentrations. In particular, this study demonstrates that a device quality ZnO material with improved electrical parameters is obtained at the level of 100 °C which can be used for applications such as Schottky diodes for cross-bar memory applications and in hybrid organic/semiconductor junction devices. - Highlights: • Influence of growth temperature on various properties of ALD grown ZnO thin films. • Very smooth surface with root mean square roughness ∼1 nm. • Free carrier concentration and mobility increases with growth temperature. • Device quality ZnO films (improved electrical parameters) are obtained at 100 °C.

  17. Heavy lithium-doped ZnO thin films prepared by spray pyrolysis method

    Indian Academy of Sciences (India)

    M Ardyanian; N Sedigh

    2014-10-01

    Lithium-doped ZnO thin films (ZnO : Li) were prepared by spray pyrolysis method on the glass substrates for ( = [Li]/[Zn]) value varied between 5 and 70%. Structural, electrical and optical properties of the samples were studied by X-ray diffraction (XRD), UV–Vis–NIR spectroscopy, scanning electron microscopy (SEM), Hall effect and sheet resistance measurements. XRD results show that for ≤ 50%, the structure of the films tends to be polycrystals of wurtzite structure with preferred direction along (0 0 2). The best crystalline order is found at = 20% and the crystal structure is stable until = 60%. The Hall effect results describe that Li doping leads to change in the conduction type from - to -type, again it changes to -type at = 70% and is attributed to self-compensation effect. Moreover, the carrier density was calculated in the order of 1013 cm-3. The resistivity of Li-doped films decreases until 22 cm at = 50%. Optical bandgap was reduced slightly, from 3.27 to 3.24 eV as a function of the grain size. Optical transmittance in the visible range reaches = 97%, by increasing of Li content until = 20%. Electrical and optical properties are coherent with structural results.

  18. Realization of As-doped p-type ZnO thin films using sputter deposition

    International Nuclear Information System (INIS)

    Arsenic-doped p-type ZnO (p-ZnO:As) thin films were deposited by the magnetron sputtering technique. High-resolution low-temperature photoluminescence (PL) spectra of the films revealed emissions at 3.35 eV and 3.32 eV, representing the neutral-acceptor-bound exciton transition and the free electron to acceptor level transition. Electroluminescence spectra of the p–n diodes fabricated from the p-ZnO:As/n-GaN heterostructure showed UV emission at about 380 nm and yellowish visible lights centered at 600–650 nm, which resembled the PL spectrum of the ZnO:As layer. The p-type ZnO films with 1at% As grown at 500°C showed a hole concentration of 5 × 1012–7 × 1013 cm−3 after the deposition and 4 × 1014–1 × 1016 cm−3 after annealing at 600 °C in oxygen atmosphere. High-resolution x-ray photoelectron spectroscopy indicated that most of the As dopants occupy Zn sites within the ZnO:As films

  19. Oxidation of ZnO thin films during pulsed laser deposition process

    Indian Academy of Sciences (India)

    E De Posada; L Moreira; J Pérez De La Cruz; M Arronte; L V Ponce; T Flores; J G Lunney

    2013-06-01

    Pulsed laser deposition of ZnO thin films, using KrF laser, is analysed. The films were deposited on (001) sapphire substrates at 400 °C, at two different oxygen pressures (0.3 and 0.4 mbar) and two different target–substrate distances (30 and 40 mm). It is observed that in order to obtain good quality in the photoluminescence of the films, associated with oxygen stoichiometry, it is needed to maximize the time during which the plasma remains in contact with the growing film (plasma residence time), which is achieved by selecting suitable combinations of oxygen pressures and target to substrate distances. It is also discussed that for the growth parameters used, the higher probability for ZnO films growth results from the oxidation of Zn deposited on the substrate and such process takes place during the time that the plasma is in contact with the substrate. Moreover, it is observed that maximizing the plasma residence time over the growing film reduces the rate of material deposition, favouring the surface diffusion of adatoms, which favours both Zn–O reaction and grain growth.

  20. Control of p- and n-type conductivities in P doped ZnO thin films by using radio-frequency sputtering

    International Nuclear Information System (INIS)

    The conduction type of P doped ZnO thin films using Zn3P2 dopant source can be controlled by adjusting the oxygen partial pressure by means of radio-frequency sputtering. Under an optimal oxygen partial pressure of 5%, p-type ZnO thin films were obtained with a hole concentration of 1.93x1016-3.84x1019 cm-3. Under a growth condition of extremely low oxygen partial pressure, P doped ZnO thin films exhibit n-type conduction with a hole concentration of 8.34x1017-3.1x1019 cm-3. This research not only achieved significant technical advance in the fabrication of p-type ZnO but also gained critical advance in fundamental understanding of the governing mechanism of p-type ZnO

  1. Tuning of undoped ZnO thin film via plasma enhanced atomic layer deposition and its application for an inverted polymer solar cell

    Directory of Open Access Journals (Sweden)

    Mi-jin Jin

    2013-10-01

    Full Text Available We studied the tuning of structural and optical properties of ZnO thin film and its correlation to the efficiency of inverted solar cell using plasma-enhanced atomic layer deposition (PEALD. The sequential injection of DEZn and O2 plasma was employed for the plasma-enhanced atomic layer deposition of ZnO thin film. As the growth temperature of ZnO film was increased from 100 °C to 300 °C, the crystallinity of ZnO film was improved from amorphous to highly ordered (002 direction ploy-crystal due to self crystallization. Increasing oxygen plasma time in PEALD process also introduces growing of hexagonal wurtzite phase of ZnO nanocrystal. Excess of oxygen plasma time induces enhanced deep level emission band (500 ∼ 700 nm in photoluminescence due to Zn vacancies and other defects. The evolution of structural and optical properties of PEALD ZnO films also involves in change of electrical conductivity by 3 orders of magnitude. The highly tunable PEALD ZnO thin films were employed as the electron conductive layers in inverted polymer solar cells. Our study indicates that both structural and optical properties rather than electrical conductivities of ZnO films play more important role for the effective charge collection in photovoltaic device operation. The ability to tune the materials properties of undoped ZnO films via PEALD should extend their functionality over the wide range of advanced electronic applications.

  2. Combined effect of oxygen deficient point defects and Ni doping in radio frequency magnetron sputtering deposited ZnO thin films

    International Nuclear Information System (INIS)

    Ni doped ZnO thin films with oxygen deficiency have been synthesized on glass substrates by radio frequency magnetron sputtering technique using argon plasma. The combined effect of point defects generated due to oxygen vacancies and Ni doping on the optical and electrical properties of ZnO thin films has been studied in this work. Ni doping concentrations were varied and the structural, optical and electrical properties of the films were studied as a function of doping concentrations. The films were characterized with X-ray diffractometer, UV–Vis–NIR spectrophotometer, X-ray photoelectron spectroscopy, atomic force microscopy and electrical conductivity measurements. Oxygen deficient point defects (Schottky defects) made the ZnO thin film highly conducting while incorporation of Ni dopant made it more functional regarding their electrical and optical properties. The films were found to have tunable electrical conductivity with Ni doping concentrations. - Highlights: • ZnO thin films prepared by radio frequency magnetron sputtering technique • Synthesis process was stimulated to introduce Schottky-type point defects. • Point defects and external doping of Ni made ZnO thin films more functional. • Point defect induced high electrical conductivity in ZnO thin film. • Significant shift in optical bandgap observed in ZnO with Ni doping concentrations

  3. Combined effect of oxygen deficient point defects and Ni doping in radio frequency magnetron sputtering deposited ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Saha, B., E-mail: biswajit.physics@gmail.com [Thin Film and Nano Science Laboratory, Department of Physics, Jadavpur University, 700 032 Kolkata (India); Department of Physics, National Institute of Technology Agartala, Jirania 799046, Tripura (India); Das, N.S.; Chattopadhyay, K.K. [Thin Film and Nano Science Laboratory, Department of Physics, Jadavpur University, 700 032 Kolkata (India)

    2014-07-01

    Ni doped ZnO thin films with oxygen deficiency have been synthesized on glass substrates by radio frequency magnetron sputtering technique using argon plasma. The combined effect of point defects generated due to oxygen vacancies and Ni doping on the optical and electrical properties of ZnO thin films has been studied in this work. Ni doping concentrations were varied and the structural, optical and electrical properties of the films were studied as a function of doping concentrations. The films were characterized with X-ray diffractometer, UV–Vis–NIR spectrophotometer, X-ray photoelectron spectroscopy, atomic force microscopy and electrical conductivity measurements. Oxygen deficient point defects (Schottky defects) made the ZnO thin film highly conducting while incorporation of Ni dopant made it more functional regarding their electrical and optical properties. The films were found to have tunable electrical conductivity with Ni doping concentrations. - Highlights: • ZnO thin films prepared by radio frequency magnetron sputtering technique • Synthesis process was stimulated to introduce Schottky-type point defects. • Point defects and external doping of Ni made ZnO thin films more functional. • Point defect induced high electrical conductivity in ZnO thin film. • Significant shift in optical bandgap observed in ZnO with Ni doping concentrations.

  4. Tuning of structural, optical, and magnetic properties of ultrathin and thin ZnO nanowire arrays for nano device applications

    OpenAIRE

    Shrama, Satinder K; Saurakhiya, Neelam; Barthwal, Sumit; Kumar, Rudra; Sharma, Ashutosh

    2014-01-01

    One-dimensional (1-D) ultrathin (15 nm) and thin (100 nm) aligned 1-D (0001) and ( 000 1 ¯ ) oriented zinc oxide (ZnO) nanowire (NW) arrays were fabricated on copper substrates by one-step electrochemical deposition inside the pores of polycarbonate membranes. The aspect ratio dependence of the compressive stress because of the lattice mismatch between NW array/substrate interface and crystallite size variations is investigated. X-ray diffraction results show that the polycrystalline ZnO NWs ...

  5. p-Type Sb-Doped ZnO Thin Films Prepared with Filtered Vacuum Arc Deposition

    OpenAIRE

    David, T; Goldsmith, S.; Boxman, R. L.

    2005-01-01

    Thin p-type Sb-doped ZnO films were grown by filtered vacuum arc deposition (FVAD), on untreated glass samples. The arc cathode was prepared by dissolving Sb into molten Zn. The deposition was performed with 200 A arc current, running for 120-240 s in 0.426 Pa oxygen pressure. The film thickness was 330-500 nm. The aotmic concentration of Sb in the films was ~1.5%, whereas the O/Zn atomic concentration ratio was ~0.7. Sb incorporation into the polycrystalline ZnO matrix was concluded from XRD...

  6. Effect of Annealing on the Structure and Photoluminescence of Eu-Doped ZnO Nanorod Ordered Array Thin Films

    OpenAIRE

    Wen-Wu Zhong; Da-Wei Guan; Yue-Lin Liu; Li Zhang; Yan-Ping Liu; Zhi-Gang Li; Wei-Ping Chen

    2012-01-01

    Eu-doped ZnO nanorod ordered array thin films were synthesized on glass substrates with a ZnO seed layer via hydrothermal method. XRD reveals that the (002) diffraction peak of films annealed in hydrogen is sharper than that annealed in air. SEM reveals that the nanorods of films annealed in hydrogen are shortened and widened. TEM results demonstrate that the nanorods are single crystalline and the lattice spacing of 0.52 nm agrees with the d spacing of (001) crystal planes along c-axis. Room...

  7. Numerical study on the dependence of ZnO thin-film transistor characteristics on grain boundary position

    Institute of Scientific and Technical Information of China (English)

    Zhang An; Zhao xiao-Ru; Duan Li-Bing; Liu Jin-Ming; Zhao Jian-Lin

    2011-01-01

    The dependence of transistor characteristics on grain boundary (GB) position in short-channel ZnO thin film transistors (TFTs) has been investigated using two-dimensional numerical simulations. To simulate the device accurately,both tail states and deep-level states are taken into consideration. It is shown that both the transfer and output characteristics of ZnO TFTs change dramatically with varying GB position, which is different from polycrystalline Si (poly-Si)TFTs. By analysing the mechanism of the carrier transportation in the device, it is revealed that the dependence is derived from the degrees of carrier concentration descent and mobility variation with GB position.

  8. Investigations of rapid thermal annealing induced structural evolution of ZnO: Ge nanocomposite thin films via GISAXS

    Science.gov (United States)

    Ceylan, Abdullah; Ozcan, Yusuf; Orujalipoor, Ilghar; Huang, Yen-Chih; Jeng, U.-Ser; Ide, Semra

    2016-06-01

    In this work, we present in depth structural investigations of nanocomposite ZnO: Ge thin films by utilizing a state of the art grazing incidence small angle x-ray spectroscopy (GISAXS) technique. The samples have been deposited by sequential r.f. and d.c. sputtering of ZnO and Ge thin film layers, respectively, on single crystal Si(100) substrates. Transformation of Ge layers into Ge nanoparticles (Ge-np) has been initiated by ex-situ rapid thermal annealing of asprepared thin film samples at 600 °C for 30, 60, and 90 s under forming gas atmosphere. A special attention has been paid on the effects of reactive and nonreactive growth of ZnO layers on the structural evolution of Ge-np. GISAXS analyses have been performed via cylindrical and spherical form factor calculations for different nanostructure types. Variations of the size, shape, and distributions of both ZnO and Ge nanostructures have been determined. It has been realized that GISAXS results are not only remarkably consistent with the electron microscopy observations but also provide additional information on the large scale size and shape distribution of the nanostructured components.

  9. Vibration optimization of ZnO thin film bulk acoustic resonator with ring electrodes

    Science.gov (United States)

    Zhao, Zinan; Qian, Zhenghua; Wang, Bin

    2016-04-01

    A rectangular ZnO thin film bulk acoustic resonator with ring electrodes is presented in this paper to demonstrate the existence of a nearly uniform displacement distribution at the central part of this typical resonator. The variational formulation based on two-dimensional scalar differential equations provides a theoretical foundation for the Ritz method adopted in our analysis. The resonant frequencies and vibration distributions for the thickness-extensional modes of this ring electrode resonator are obtained. The structural parameters are optimized to achieve a more uniform displacement distribution and therefore a uniform mass sensitivity, which guarantee the high accuracy and repeatable measurement for sensor detection in an air or a liquid environment. These results provide a fundamental reference for the design and optimization of the high quality sensor.

  10. Thickness-dependent fracture behaviour of flexible ZnO : Al thin films

    International Nuclear Information System (INIS)

    The effects of thickness on flexibility and crack initiation in ZnO : Al thin films sputter-deposited on polyethersulfone substrates have been investigated. With an increase in thickness, root-mean-square roughness and average crystallite size increase linearly. It is found that the higher the thickness, the lower is the strain required to initiate cracks in the film. The thinnest film (∼240 nm) exhibits a crack-initiating critical strain of 0.96% and a saturated crack density of 0.10 μm-1. A critical energy release rate of 68.5 J m-2 and a mode I fracture toughness of 3.2 MPa m0.5 are estimated for the films. These parameters are found to exhibit a linear dependence on film thickness.

  11. Temperature dependence of the spin relaxation in highly degenerate ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Prestgard, M. C.; Siegel, G.; Tiwari, A., E-mail: tiwari@eng.utah.edu [Department of Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84112 (United States); Materials Research Science and Engineering Center, University of Utah, Salt Lake City, Utah 84112 (United States); Roundy, R.; Raikh, M. [Materials Research Science and Engineering Center, University of Utah, Salt Lake City, Utah 84112 (United States); Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112 (United States)

    2015-02-28

    Zinc oxide is considered a potential candidate for fabricating next-generation transparent spintronic devices. However, before this can be achieved, a thorough scientific understanding of the various spin transport and relaxation processes undergone in this material is essential. In the present paper, we are reporting our investigations into these processes via temperature dependent Hanle experiments. ZnO thin films were deposited on c-axis sapphire substrates using a pulsed laser deposition technique. Careful structural, optical, and electrical characterizations of the films were performed. Temperature dependent non-local Hanle measurements were carried out using an all-electrical scheme for spin injection and detection over the temperature range of 20–300 K. From the Hanle data, spin relaxation time in the films was determined at different temperatures. A detailed analysis of the data showed that the temperature dependence of spin relaxation time follows the linear-in-momentum Dyakonov-Perel mechanism.

  12. ZnO thin film transistor immunosensor with high sensitivity and selectivity

    Science.gov (United States)

    Reyes, Pavel Ivanoff; Ku, Chieh-Jen; Duan, Ziqing; Lu, Yicheng; Solanki, Aniruddh; Lee, Ki-Bum

    2011-04-01

    A zinc oxide thin film transistor-based immunosensor (ZnO-bioTFT) is presented. The back-gate TFT has an on-off ratio of 108 and a threshold voltage of 4.25 V. The ZnO channel surface is biofunctionalized with primary monoclonal antibodies that selectively bind with epidermal growth factor receptor (EGFR). Detection of the antibody-antigen reaction is achieved through channel carrier modulation via pseudo double-gating field effect caused by the biochemical reaction. The sensitivity of 10 fM detection of pure EGFR proteins is achieved. The ZnO-bioTFT immunosensor also enables selectively detecting 10 fM of EGFR in a 5 mg/ml goat serum solution containing various other proteins.

  13. Physical properties of Ga-doped ZnO thin films by spray pyrolysis

    International Nuclear Information System (INIS)

    Research highlights: In this work, we report the structural, optical and electrical properties of the transparent conducting GZO thin films prepared by spray pyrolysis method. We sought optimum deposition conditions yielding GZO films with desired physical properties, specifically good crystalline quality microstructure, low resistivity and high transparency. The electrical conductivity and mobilities of GZO thin films are very good as compared with previous reported spray pyrolysed films. - Abstract: Gallium doped zinc oxide (GZO) thin films were prepared using the simple, flexible and cost-effective spray pyrolysis technique. The physical properties of the films were studied as a function of increasing gallium dopant concentration from 1 to 9 at.%. The films were characterized by various methods to understand their structural, morphological, optical and electrical properties. The X-ray diffraction analysis revealed that the films were polycrystalline in nature having a hexagonal wurtzite type crystal structure with a preferred grain orientation in the (0 0 2) direction. Scanning electron microscopy (SEM) measurements reveal that the surface morphology of the films changes continuously with a decrease in the grain size due to Ga doping. All the films showed nearly 90% of transparency in the entire visible region. A blue shift of the optical band gap was observed with an increase in Ga doping. Room temperature photoluminescence (PL) measurement of the deposited films indicates incorporation of Ga in ZnO lattice. At 3 at.% Ga doping, the film has lowest resistivity of 6.8 x 10-3 cm while the carrier concentration is highest.

  14. Improvement in the Grain Growth of Plasma-Treated Nano-Sized ZnO Films and Their Characterization.

    Science.gov (United States)

    Chen, Mi; Chou, Ching-Chuan; Lin, Ching-Cheng; Koo, Horng-Show

    2015-11-01

    The well-aligned ZnO nanorods were rapidly grown on an indium tin oxide (ITO)-coated glass substrate using Al-doped ZnO (AZO) thin film as seed layer by the microwave-assisted hydrothermal chemical route. The optimal growth conditions for the well-aligned ZnO nanorods were obtained by modulating H2 plasma pretreatment time for the seed layer and synthesis time for ZnO nanorods. The H2 plasma effect of the seed layer on the alignment, growth rate and crysallinity of ZnO nanods is also demonstrated. The synthesized ZnO nanorods were annealed in atmosphere of N2, O2 and H2 + N2 mixed gas to improve the related physical characteristics, the ZnO nanorods on grapheme/ITO substrate were also investigated. The results show that the alignment and growth rate of ZnO nanorods depends on the physical characteristics and roughness of the seed layer, which can be improved by H2 plasma pretreatment. The average growth rate of ZnO nanorods synthesized by microwave hydrothermal technique is about 2.2 μm/hr which significantly superior to other conventional techniques. After the appropriate N2 annealing treatment, good quality and well-aligned ZnO nanorods, which are single crystal with stacking defects and pyramid or candle shape, were obtained. A fundamental model of the effect of H2 plasma pretreatment on the surface of seed layer and the growth of ZnO nanorods using a microwave-assisted hydrothermal chemical route is also described. PMID:26726662

  15. Synthesis, microstructural characterization and optical properties of undoped, V and Sc doped ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Amezaga-Madrid, P.; Antunez-Flores, W.; Ledezma-Sillas, J.E.; Murillo-Ramirez, J.G.; Solis-Canto, O.; Vega-Becerra, O.E.; Martinez-Sanchez, R. [Centro de Investigacion en Materiales Avanzados S.C. and Laboratorio Nacional de Nanotecnologia, Miguel de Cervantes 120, Chihuahua, Chih., C.P. 31109 (Mexico); Miki-Yoshida, M., E-mail: mario.miki@cimav.edu.mx [Centro de Investigacion en Materiales Avanzados S.C. and Laboratorio Nacional de Nanotecnologia, Miguel de Cervantes 120, Chihuahua, Chih., C.P. 31109 (Mexico)

    2011-06-15

    Research highlights: > Undoped, V and Sc doped ZnO thin films by Aerosol Assisted Chemical Vapour Deposition. > Optimum substrate temperatures of 673 K and 623 K for Sc and V doped films. > Around one third of the dopants in solution were deposited into the films. > Crystallite and grain size decreased with the increase of dopant concentration. > Optical band gap increased from 3.29 to 3.32 eV for undoped to 7 Sc/Zn at. %. - Abstract: Many semiconductor oxides (ZnO, TiO{sub 2}, SnO{sub 2}) when doped with a low percentage of non-magnetic (V, Sc) or magnetic 3d (Co, Mn, Ni, Fe) cation behave ferromagnetically. They have attracted a great deal of interest due to the integration of semiconducting and magnetic properties in a material. ZnO is one of the most promising materials to carry out these tasks in view of the fact that it is optically transparent and has n or p type conductivity. Here, we report the synthesis, microstructural characterization and optical properties of undoped, V and Sc doped zinc oxide thin films. ZnO based thin films with additions of V and Sc were deposited by the Aerosol Assisted Chemical Vapour Deposition method. V and Sc were incorporated separately in the precursor solution. The films were uniform, transparent and non-light scattering. The microstructure of the films was characterized by Grazing Incidence X-ray Diffraction, Scanning Electron Microscopy, and Scanning Probe Microscopy. Average grain size and surface rms roughness were estimated by the measurement of Atomic Force Microscopy. The microstructure of doped ZnO thin films depended on the type and amount of dopant material incorporated. The optical properties were determined from specular reflectance and transmittance spectra. Results were analyzed to determine the optical constant and band gap of the films. An increase in the optical band gap with the content of Sc dopant was obtained.

  16. Synthesis, microstructural characterization and optical properties of undoped, V and Sc doped ZnO thin films

    International Nuclear Information System (INIS)

    Research highlights: → Undoped, V and Sc doped ZnO thin films by Aerosol Assisted Chemical Vapour Deposition. → Optimum substrate temperatures of 673 K and 623 K for Sc and V doped films. → Around one third of the dopants in solution were deposited into the films. → Crystallite and grain size decreased with the increase of dopant concentration. → Optical band gap increased from 3.29 to 3.32 eV for undoped to 7 Sc/Zn at. %. - Abstract: Many semiconductor oxides (ZnO, TiO2, SnO2) when doped with a low percentage of non-magnetic (V, Sc) or magnetic 3d (Co, Mn, Ni, Fe) cation behave ferromagnetically. They have attracted a great deal of interest due to the integration of semiconducting and magnetic properties in a material. ZnO is one of the most promising materials to carry out these tasks in view of the fact that it is optically transparent and has n or p type conductivity. Here, we report the synthesis, microstructural characterization and optical properties of undoped, V and Sc doped zinc oxide thin films. ZnO based thin films with additions of V and Sc were deposited by the Aerosol Assisted Chemical Vapour Deposition method. V and Sc were incorporated separately in the precursor solution. The films were uniform, transparent and non-light scattering. The microstructure of the films was characterized by Grazing Incidence X-ray Diffraction, Scanning Electron Microscopy, and Scanning Probe Microscopy. Average grain size and surface rms roughness were estimated by the measurement of Atomic Force Microscopy. The microstructure of doped ZnO thin films depended on the type and amount of dopant material incorporated. The optical properties were determined from specular reflectance and transmittance spectra. Results were analyzed to determine the optical constant and band gap of the films. An increase in the optical band gap with the content of Sc dopant was obtained.

  17. Structural and Luminescent Properties of ZnO Thin Films Deposited by Atmospheric Pressure Chemical Vapour Deposition

    Institute of Scientific and Technical Information of China (English)

    ZHAO Guo-Liang; LIN Bi-Xia; HONG Liang; MENG Xiang-Dong; FU Zhu-Xi

    2004-01-01

    ZnO thin films were successfully deposited on Si (100) substrates by chemical vapour deposition (CVD) at atmospheric pressure (1 atm). The only solid source used here is zinc acetate, (CHsCOO)2Zn, and the carrier gas is nitrogen. The sample, which was prepared at 550℃ during growth and then annealed in air at 900℃ , has only a ZnO (002) diffraction peak at 34.6° with its FWHM of 0.23° in the XRD pattern. The room-temperature PL spectrum shows a strong ultraviolet emission with the peak centred at 380nm. We analysed the effects of many factors, such as the source, substrates, growth and annealing temperatures, and annealing ambience, on the structural and optical properties of our prepared ZnO films.

  18. Influence of Doping and Annealing on Structural, Optical and Electrical properties Amorphous ZnO Thin Films Prepared by PLD

    Directory of Open Access Journals (Sweden)

    Azhar AbduAlwahab Ali

    2015-03-01

    Full Text Available The optical gap of the films was calculated from the curve of absorption coefficient (αhע2 vs. hע and was found to be 3.8 eV at room temperature, and this value decreases from 3.8 to 3.58 eV with increasing of annealing temperature up to 473-673 K, and increases with the Ga doping. λ cutoff was calculated for ZnO and showed an increase with increasing annealing temperature and shifting to longer wavelength, while with doping the λcutoff shifted to shorter wavelength. The photoluminescence (PL results indicate that the pure ZnO thin films grown at room temperature show strong peaks at 640 nm , but  GaO doped ZnO films showed a band emission in the yellow-green spectral region (380 to 450nm.

  19. Investigation of ZnO thin films deposited on ferromagnetic metallic buffer layer by molecular beam epitaxy toward realization of ZnO-based magnetic tunneling junctions

    International Nuclear Information System (INIS)

    Deposition of ZnO thin films on a ferromagnetic metallic buffer layer (Co3Pt) by molecular beam epitaxy technique was investigated for realization of ZnO-based magnetic tunneling junctions with good quality hexagonal ZnO films as tunnel barriers. For substrate temperature of 600 °C, ZnO films exhibited low oxygen defects and high electrical resistivity of 130 Ω cm. This value exceeded that of hexagonal ZnO films grown by sputtering technique, which are used as tunnel barriers in ZnO-MTJs. Also, the effect of oxygen flow during deposition on epitaxial growth conditions and Co3Pt surface oxidation was discussed.

  20. Carriers-mediated ferromagnetic enhancement in Al-doped ZnMnO dilute magnetic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Saleem, Murtaza [Centre of Excellence in Solid State Physics, University of the Punjab, Lahore-54590 (Pakistan); Siddiqi, Saadat A. [Centre of Excellence in Solid State Physics, University of the Punjab, Lahore-54590 (Pakistan); Interdisciplinary Research Centre in Biomedical Materials (IRCBM), COMSATS Institute of Information Technology, Defence Road, Off Raiwind Road, Lahore (Pakistan); Atiq, Shahid, E-mail: shahidatiqpasrur@yahoo.com [Centre of Excellence in Solid State Physics, University of the Punjab, Lahore-54590 (Pakistan); Anwar, M. Sabieh; Hussain, Irshad [School of Science and Engineering (SSE), Lahore University of Management Sciences (LUMS), Opposite Sector U, D.H.A. Lahore Cantt-54792 (Pakistan); Alam, Shahzad [Pakistan Council for Scientific and Industrial Research (PCSIR) Laboratories Complex, Lahore (Pakistan)

    2011-11-15

    Nano-crystalline Zn{sub 0.95-x}Mn{sub 0.05}Al{sub x}O (x = 0, 0.05, 0.10) dilute magnetic semiconductors (DMS) were synthesized by sol-gel derived auto-combustion. X-ray diffraction (XRD) analysis shows that the samples have pure wurtzite structure typical of ZnO without the formation of secondary phases or impurity. Crystallite sizes were approximated by Scherrer formula while surface morphology and grain sizes were measured by field emission scanning electron microscopy. Incorporation of Mn and Al into the ZnO structure was confirmed by energy-dispersive X-ray analysis. Temperature dependent electrical resistivity measurements showed a decreasing trend with the doping of Al in ZnMnO, which is attributable to the enhancement of free carriers. Vibrating sample magnetometer studies confirmed the presence of ferromagnetic behavior at room temperature. The results indicate that Al doping results in significant variation in the concentration of free carriers and correspondingly the carrier-mediated magnetization and room temperature ferromagnetic behavior, showing promise for practical applications. We attribute the enhanced saturation magnetization and electrical conductivity to the exchange interaction mediated by free electrons.

  1. Pretreatment of polyethylene terephthalate substrate for the growth of Ga-doped ZnO thin film.

    Science.gov (United States)

    Kim, D W; Kang, J H; Lim, Y S; Lee, M H; Seo, W S; Park, H H; Seo, K H; Park, M G

    2011-02-01

    The effect of the pretreatment of polyethylene terephthalate (PET) substrate on the growth of transparent conducting Ga-doped ZnO (GZO) thin film was investigated. Because of its high gas and moisture absorption and easy gas permeation, PET substrate was annealed at 100 degrees C in a vacuum chamber prior to the sputtering growth of GZO thin film for the outgassing of impurity gases. GZO thin film was deposited on the pretreated PET substrate by rf-magnetron sputtering and significantly improved electrical properties of GZO thin film was achieved. Electrical and structural characterizations of the GZO thin films were carried out by 4-point probe, Hall measurement, and scanning electron microscopy, and the effects of the pretreatment on the improved properties of GZO thin films were discussed. This result is not only useful to PET substrate, but also could be applicable to other plastic substrates which inevitably containing the moisture and impurity gases. PMID:21456250

  2. Effects of precursor concentrations on ZnO nano-fibrous thin films grown by using the sol-gel dip-coating method

    International Nuclear Information System (INIS)

    ZnO thin films were fabricated by using the dip-coating method to deposit solutions with different precursor concentrations on quartz substrates. The structural and the optical properties of the ZnO thin films were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence (PL), and ultraviolet-visible spectroscopy. The average grain size in the ZnO thin films increased from 19.09 to 39.19 nm with increasing precursor concentrations, and nanofibrous structures were observed on the surface when precursor concentrations above 0.4 M were used. The PL spectra, in all cases, showed near-band-edge (NBE) emission and deep-level emission (DLE). When the precursor concentrations were increased, the optical band gap values for the ZnO thin films shifted towards the blue region, and the values of the Urbach energy (EU) gradually decreased from 154 to 65 meV.

  3. Optical and Electrical Characteristic of Layer-by-layer Sol-gel Spin Coated Nanoparticles ZnO Thin Films

    International Nuclear Information System (INIS)

    Transparent ZnO thin films have been deposited on glass substrate using sol-gel spin coating technique. 0.35 M sol were prepared by dissolving zinc acetate dehydrate in 2-methoxyethanol with monoethanolamine as the stabilizer. In this paper, a novel method called layer-by-layer is introduced, where the thin film is not only dried after each layer is spin-coated, but also directly annealed at 500 degree Celsius to improve the crystallinity of the films. Samples without annealing were also prepared as the control sample. ZnO thin films were characterized using field emission scanning electron microscopy, X-ray diffraction, current-voltage measurement, UV-Vis spectroscopy and photoluminescence spectroscopy. The results revealed that layer by- layer ZnO thin films have better conductivity and higher intensity peak for PL spectra at visible spectra of 580 nm. FE-SEM images shows nanoparticles almost hexagonal shaped with high crystallinity compared to control samples. (author)

  4. Sol–Gel and Thermally Evaporated Nanostructured Thin ZnO Films for Photocatalytic Degradation of Trichlorophenol

    Directory of Open Access Journals (Sweden)

    Mahmoud Sawsan

    2009-01-01

    Full Text Available Abstract In the present work, thermal evaporation and sol–gel coating techniques were applied to fabricate nanostructured thin ZnO films. The phase structure and surface morphology of the obtained films were investigated by X-ray diffractometer (XRD and scanning electron microscope (SEM, respectively. The topography and 2D profile of the thin ZnO films prepared by both techniques were studied by optical profiler. The results revealed that the thermally evaporated thin film has a comparatively smoother surface of hexagonal wurtzite structure with grain size 12 nm and 51 m2/g. On the other hand, sol–gel films exhibited rough surface with a strong preferred orientation of 25 nm grain size and 27 m2/g surface area. Following deposition process, the obtained films were applied for the photodegradation of 2,4,6-trichlorophenol (TCP in water in presence of UV irradiation. The concentrations of TCP and its intermediates produced in the solution during the photodegradation were determined by high performance liquid chromatography (HPLC at defined irradiation times. Complete decay of TCP and its intermediates was observed after 60 min when the thermal evaporated photocatalyst was applied. However, by operating sol–gel catalyst, the concentration of intermediates initially increased and then remained constant with irradiation time. Although the degradation of TCP followed first-order kinetic for both catalysts, higher photocatalytic activity was exhibited by the thermally evaporated ZnO thin film in comparison with sol–gel one.

  5. Towards solution-processed ambipolar hybrid thin-film transistors based on ZnO nanoparticles and P3HT polymer

    Science.gov (United States)

    Diallo, Abdou Karim; Gaceur, Meriem; Berton, Nicolas; Margeat, Olivier; Ackermann, Jörg; Videlot-Ackermann, Christine

    2013-06-01

    Solution-processed n-channel oxide semiconductor thin-film transistors (TFTs) were fabricated using zinc oxide (ZnO) nanoparticles. Polycrystalline fused-ZnO nanoparticle films were produced by spin-coating ZnO nanosphere dispersions following by a subsequent heat treatment. The solution-processable semiconductor ink based on ZnO was prepared by dispersing the synthesized ZnO nanospheres in isopropanol mixed with ethanolamine to various concentrations from 20 to 80 mg/mL. Such concentration dependence on morphology and microstructure of thin films was studied on spin-coated ZnO films by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Spin-coated ZnO films involved as active layers in transistor configuration delivered an almost ideal output characteristic (Id-Vd) with an electron mobility up to 3 × 10-2 cm2/V s. As a p-channel semiconductor, a poly(3-hexylthiophene) (P3HT) solution-processable ink was deposited by spin-coating on top of closely packed ZnO nanoparticles-based films to form an uniform overlying layer. A hybrid (inorganic-organic) interface was formed by the direct contact between ZnO and P3HT leading to carrier redistribution. Such solution-processed hybrid thin-film transistors delivered in air well balanced electron and hole mobilities as 3.9 × 10-5 and 2 × 10-5 cm2/V s, respectively.

  6. Effect of tin doping on optical properties of nanostructured ZnO thin films grown by spray pyrolysis technique

    Energy Technology Data Exchange (ETDEWEB)

    Bedia, F.Z.; Bedia, A. [URMER, Abou-Bakr Belkaid University, 13000 Tlemcen (Algeria); Maloufi, N., E-mail: nabila.maloufi@univ-lorraine.fr [Laboratoire d’Étude des Microstructures et de Mécanique des Matériaux (LEM3), UMR-CNRS 7239, Université de Lorraine, 57045 Metz (France); Laboratory of Excellence on Design of Alloy Metals for low-mAss Structures (DAMAS), Université de Lorraine (France); Aillerie, M.; Genty, F. [LMOPS-EA 4423, Université de Lorraine, 57070 Metz (France); Supelec, LMOPS, 57070 Metz (France); Benyoucef, B. [URMER, Abou-Bakr Belkaid University, 13000 Tlemcen (Algeria)

    2014-12-15

    Highlights: • (0–2%) Sn-doped ZnO films grown by spray pyrolysis on glass substrates. • Transmittance up to 93% in visible region, sharp absorption edge at 360 nm. • Blue shift of optical band gap: E{sub g} = 3.27 eV for 0% Sn; Eg{sub max} = 3.30 eV for 0.5% Sn. • All the optical parameters reach threshold values for 0.5% Sn-doped ZnO films. • Good physical properties suited for films integration in optoelectronic devices. - Abstract: Sn-doped ZnO thin films with 0%, 0.5%, 1%, 1.5% and 2% Sn were grown by spray pyrolysis method on glass substrates under optimized conditions. High resolution Field Effect Scanning Electron Microscopy characterization showed that the films consist of hexagonal-like grains. A comprehensive study of the optical properties was performed and the dispersion constants were determined. The effect of Sn content on the optical band gap and the optical constants (refractive index, extinction coefficient, dielectric constants, and dispersion parameters) was studied. These Sn-doped ZnO thin films are highly transparent (73–93%) in the visible region. A blue shift of the optical band gap, attributed to the Burstein Moss effect, was observed for the Sn-doped films. All the optical dispersion parameters depend on the Sn content of the films, but were found to reach threshold values at a Sn content of 0.5%. These optical parameters are discussed in terms of the single oscillator model. This study demonstrated that this 0.5% Sn-doped ZnO thin film has enhanced physical properties, allowing its better integration in optoelectronic devices.

  7. Effect of tin doping on optical properties of nanostructured ZnO thin films grown by spray pyrolysis technique

    International Nuclear Information System (INIS)

    Highlights: • (0–2%) Sn-doped ZnO films grown by spray pyrolysis on glass substrates. • Transmittance up to 93% in visible region, sharp absorption edge at 360 nm. • Blue shift of optical band gap: Eg = 3.27 eV for 0% Sn; Egmax = 3.30 eV for 0.5% Sn. • All the optical parameters reach threshold values for 0.5% Sn-doped ZnO films. • Good physical properties suited for films integration in optoelectronic devices. - Abstract: Sn-doped ZnO thin films with 0%, 0.5%, 1%, 1.5% and 2% Sn were grown by spray pyrolysis method on glass substrates under optimized conditions. High resolution Field Effect Scanning Electron Microscopy characterization showed that the films consist of hexagonal-like grains. A comprehensive study of the optical properties was performed and the dispersion constants were determined. The effect of Sn content on the optical band gap and the optical constants (refractive index, extinction coefficient, dielectric constants, and dispersion parameters) was studied. These Sn-doped ZnO thin films are highly transparent (73–93%) in the visible region. A blue shift of the optical band gap, attributed to the Burstein Moss effect, was observed for the Sn-doped films. All the optical dispersion parameters depend on the Sn content of the films, but were found to reach threshold values at a Sn content of 0.5%. These optical parameters are discussed in terms of the single oscillator model. This study demonstrated that this 0.5% Sn-doped ZnO thin film has enhanced physical properties, allowing its better integration in optoelectronic devices

  8. Cycling behaviour of sponge-like nanostructured ZnO as thin-film Li-ion battery anodes

    International Nuclear Information System (INIS)

    Highlights: • Zn is thermally oxidized in ambient air to obtain sponge-like ZnO film. • Polycrystalline, transparent, porous thin film is obtained. • Film exhibits stabile specific capacity (∼300 mAh g−1) after prolonged cycling. • Sponge-like ZnO film shows promising prospects as Li-ion battery anode. - Abstract: Single phase wurtzitic porous ZnO thin films are obtained by a simple two-step method, involving the sputtering deposition of a sponge-like metallic Zn layer, followed by a moderately low temperature treatment for the complete zinc oxidation. Thanks to its 3D nanostructuration, the superimposition of small branches able to grow in length almost isotropically and forming a complex topography, sponge-like ZnO can combine the fast transport properties of one dimensional material and the high surface area usually provided by nanocrystalline electrodes. When galvanostatically tested in lithium cell, after the initial decay, it can provide an almost stable specific capacity higher than 50 μAh cm−2 after prolonged cycling at estimated 0.7 C, with very high Coulombic efficiency

  9. Application of Thin ZnO ALD Layers in Fiber-Optic Fabry-Pérot Sensing Interferometers.

    Science.gov (United States)

    Majchrowicz, Daria; Hirsch, Marzena; Wierzba, Paweł; Bechelany, Michael; Viter, Roman; Jędrzejewska-Szczerska, Małgorzata

    2016-01-01

    In this paper we investigated the response of a fiber-optic Fabry-Pérot sensing interferometer with thin ZnO layers deposited on the end faces of the optical fibers forming the cavity. Standard telecommunication single-mode optical fiber (SMF-28) segments were used with the thin ZnO layers deposited by Atomic Layer Deposition (ALD). Measurements were performed with the interferometer illuminated by two broadband sources operating at 1300 nm and 1550 nm. Reflected interference signal was acquired by an optical spectrum analyzer while the length of the air cavity was varied. Thickness of the ZnO layers used in the experiments was 50 nm, 100 nm, and 200 nm. Uncoated SMF-28 fiber was also used as a reference. Based on the results of measurements, the thickness of the ZnO layers and the length of the cavity were selected in order to achieve good visibility. Following, the interferometer was used to determine the refractive index of selected liquids. PMID:27011188

  10. Cycling behaviour of sponge-like nanostructured ZnO as thin-film Li-ion battery anodes

    Energy Technology Data Exchange (ETDEWEB)

    Garino, Nadia, E-mail: nadia.garino@iit.it [Center for Space Human Robotics @Polito, Istituto Italiano di Tecnologia, Corso Trento, 21, 10129 Turin (Italy); Lamberti, Andrea; Gazia, Rossana; Chiodoni, Angelica [Center for Space Human Robotics @Polito, Istituto Italiano di Tecnologia, Corso Trento, 21, 10129 Turin (Italy); Gerbaldi, Claudio, E-mail: claudio.gerbaldi@polito.it [Center for Space Human Robotics @Polito, Istituto Italiano di Tecnologia, Corso Trento, 21, 10129 Turin (Italy); GAME Lab, Department of Applied Science and Technology – DISAT, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129 Turin (Italy)

    2014-12-05

    Highlights: • Zn is thermally oxidized in ambient air to obtain sponge-like ZnO film. • Polycrystalline, transparent, porous thin film is obtained. • Film exhibits stabile specific capacity (∼300 mAh g{sup −1}) after prolonged cycling. • Sponge-like ZnO film shows promising prospects as Li-ion battery anode. - Abstract: Single phase wurtzitic porous ZnO thin films are obtained by a simple two-step method, involving the sputtering deposition of a sponge-like metallic Zn layer, followed by a moderately low temperature treatment for the complete zinc oxidation. Thanks to its 3D nanostructuration, the superimposition of small branches able to grow in length almost isotropically and forming a complex topography, sponge-like ZnO can combine the fast transport properties of one dimensional material and the high surface area usually provided by nanocrystalline electrodes. When galvanostatically tested in lithium cell, after the initial decay, it can provide an almost stable specific capacity higher than 50 μAh cm{sup −2} after prolonged cycling at estimated 0.7 C, with very high Coulombic efficiency.

  11. Application of Thin ZnO ALD Layers in Fiber-Optic Fabry-Pérot Sensing Interferometers

    Directory of Open Access Journals (Sweden)

    Daria Majchrowicz

    2016-03-01

    Full Text Available In this paper we investigated the response of a fiber-optic Fabry-Pérot sensing interferometer with thin ZnO layers deposited on the end faces of the optical fibers forming the cavity. Standard telecommunication single-mode optical fiber (SMF-28 segments were used with the thin ZnO layers deposited by Atomic Layer Deposition (ALD. Measurements were performed with the interferometer illuminated by two broadband sources operating at 1300 nm and 1550 nm. Reflected interference signal was acquired by an optical spectrum analyzer while the length of the air cavity was varied. Thickness of the ZnO layers used in the experiments was 50 nm, 100 nm, and 200 nm. Uncoated SMF-28 fiber was also used as a reference. Based on the results of measurements, the thickness of the ZnO layers and the length of the cavity were selected in order to achieve good visibility. Following, the interferometer was used to determine the refractive index of selected liquids.

  12. ZnO thin films fabricated by chemical bath deposition, used as buffer layer in organic solar cells

    International Nuclear Information System (INIS)

    ZnO thin films synthetized by chemical bath deposition are used as buffer layer between the anode and the organic electron donor in organic solar cells. Films deposited from zinc nitrate solutions are annealed in room air at 300 deg. C for half an hour. The X-ray diffraction and microanalysis studies show that ZnO polycrystalline thin films are obtained. The solar cells used are based on the couple copper phthalocyanine as electron donor and (N,N-diheptyl-3,4,9,10-perylenetetracarboxylicdiimide-PTCDI-C7) as electron acceptor. It is shown that the presence of the ZnO buffer layer improves the energy conversion efficiency of the cells. Such improvement could be attributed to a better energy level alignment at the anode/electron donor interface. The anode roughness induced by the ZnO buffer layer can also transform the planar interface organic electron donor/electron acceptor into roughen topography. This increases the interface area, where carrier separation takes place, which improves solar cells performances.

  13. Effect of Ga doping on micro/structural, electrical and optical properties of pulsed laser deposited ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Shinde, S.D. [Centre for Advanced Studies in Materials Science and Condensed Matter Physics, Department of Physics, University of Pune, Pune 411 007 (India); Deshmukh, A.V. [Centre for Advanced Studies in Materials Science and Condensed Matter Physics, Department of Physics, University of Pune, Pune 411 007 (India); Department of Physics, College of Engineering, Pune 411 005 (India); Date, S.K. [Centre for Advanced Studies in Materials Science and Condensed Matter Physics, Department of Physics, University of Pune, Pune 411 007 (India); Sathe, V.G. [UGC-DAE Consortium for Scientific Research, University Campus, Indore-452 017 (India); Adhi, K.P., E-mail: kpa@physics.unipune.ac.in [Centre for Advanced Studies in Materials Science and Condensed Matter Physics, Department of Physics, University of Pune, Pune 411 007 (India)

    2011-12-01

    Undoped and Ga doped ZnO thin films (1% GZO, 3% GZO and 5% GZO) were grown on c-Al{sub 2}O{sub 3} substrates using the 1, 3 and 5 at. wt.% Ga doped ZnO targets by pulsed laser deposition. X-ray diffraction studies revealed that highly c-axis oriented, single phase, undoped and Ga doped ZnO thin films with wurtzite structure were deposited. Micro-Raman scattering analysis showed that Ga doping introduces defects in the host lattice. The E{sub 2}{sup High} mode of ZnO in Ga doped ZnO thin film was observed to shift to higher wavenumber indicating the presence of residual compressive stress. Appearance of the normally Raman inactive B{sub 1} modes (B{sub 1}{sup Low}, 2B{sub 1}{sup Low} and B{sub 1}{sup High}) due to breaking of local translational symmetry, also indicated that defects were introduced into the host lattice due to Ga incorporation. Band gap of the Ga doped ZnO thin films was observed to shift to higher energy with the increase in doping concentration and is explicated by the Burstein-Moss effect. Electrical resistivity measurements of the undoped and GZO thin films in the temperature range 50 to 300 K revealed the metal to semiconductor transition for 3 and 5% GZO thin films.

  14. Copper(II) Schiff base complexes and their mixed thin layers with ZnO nanoparticles

    Indian Academy of Sciences (India)

    MAGDALENA BARWIOLEK; ROBERT SZCZĘSNY; EDWARD SZŁYK

    2016-07-01

    Cu(II) complexes with Schiff bases derived from ethylenediamine (en) and 2-pyridinecarboxaldehyde (pyca), 2,5-dimethoxybenzaldehyde (dmbaH) or 4-imidazolecarboxaldehyde (4Him) were obtained and studied by elemental analysis, UV-VIS and IR spectra. Zinc oxide was synthesized using a simple homogeneous precipitation method with zinc acetate as a starting material. Thin layers of the studied Cu(II) complexes were deposited on Si(111) or ZnO/Si(111) substrates by a spin coating method and characterized with a scanningelectron microscopy (SEM/EDS), atomic force microscopy (AFM) and fluorescence spectroscopy. For Cu(II) layers the most intensive fluorescence bands due to intra-ligand transitions were observed between 462 and 503 nm. The fluorescence intensity of thin layers was corelated to the rotation speed. In the case of the [Cu(II)(en(4Him)₂)Cl₂](2a)/ZnO/Si and [Cu(en(dmbaH)₂)Cl₂](3a)/ZnO/Si layers the quenching of the emission band from ZnO at 440 nm (λex = 330 nm) associated with various intrinsic or extrinsic lattice defects was noted.

  15. An economic approach to fabricate photo sensor based on nanostructured ZnO thin films

    Science.gov (United States)

    Huse, Nanasaheb; Upadhye, Deepak; Sharma, Ramphal

    2016-05-01

    Nanostructural ZnO Thin Films have been synthesized by simple and economic Chemical Bath Deposition technique onto glass substrate with bath temperature at 60°C for 1 hour. Structural, Optical, Electrical and topographical properties of the prepared Thin Films were investigated by GIXRD, I-V Measurement System, UV-Visible Spectrophotometer and AFM respectively. Calculated lattice parameters are in good agreement with the standard JCPDS card (36-1451) values, exhibits Hexagonal Wurtzite crystal structure. I-V Measurement curve has shown ohmic nature in dark condition and responds to light illumination which reveals Photo sensor properties. After illumination of 60W light, decrease in resistance was observed from 110.9 KΩ to 104.4 KΩ. The change in current and calculated Photo sensitivity was found to be 3.51 µA and 6.3% respectively. Optical band gap was found to be 3.24 eV. AFM images revealed uniform deposition over entire glass substrate with 32.27 nm average roughness of the film.

  16. Effect of Oxygen Flow Rate on the Properties of Nano columnar ZnO Thin Films Prepared using Radio Frequency Magnetron Sputtering System for Ultraviolet Sensor Applications

    International Nuclear Information System (INIS)

    Nano structured ZnO thin films were deposited on glass substrates using radio frequency (RF) magnetron sputtering system at different oxygen (O2) flow rates ranges between 0 to 40 sccm. By using ZnO target that were bombarded by argon (Ar) plasma generated by RF power of 250 W in the Ar and O2 gas mixture ambient, nano columnar ZnO structure thin films were produced on the substrates as observed through atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). The surface roughness of the films found to be decreased with higher O2 flow rates. The ultraviolet-visible (UV-Vis) spectra show that all samples are very transparent in the visible region (400-800 nm) with average transparency above 85 %. The XRD spectra reveal that the deposited films are preferentially grown along the c-axis indicating high ZnO crystallinity. The photocurrent properties indicate that ZnO thin film prepared at O2 flow rate of 20 sccm has the optimum characteristic for ultraviolet sensor applications. This finding suggested that the O2 flow rates play important role and has critical value for semiconducting nano columnar ZnO growth in the sputtering system, which can produce ZnO thin film with high sensitivity of ultraviolet detection. (author)

  17. Thermal stability of conductive and transparent V-doped ZnO thin films

    International Nuclear Information System (INIS)

    The thermal stability of electrical, optical and structural properties of vanadium-doped zinc oxide (VZO) thin films has been investigated after heat treatments up to 550 °C in N2 and O2 atmospheres. ZnO and VZO films were prepared by RF magnetron sputtering on quartz substrates at 200 °C. It was found that the resistivity of VZO films remains low at about 5 × 10−4 Ω cm when heat treated at temperature up to 450 °C in both N2 and O2 atmospheres, while resistivity of the ZnO film increased remarkably due to the compensation of oxygen vacancies in O2 heat treatments over 400 °C. Optical transmittance of the as-grown VZO film in the visible range (400–1100 nm) was 20–30% and improved up to about 80% when heat treated at temperature up to 500 °C in N2 and O2 atmospheres. Decreased c-axis lattice constant in the VZO film was larger in N2 heat treatments than in O2 heat treatments. Based on these experimental results, we made the hypothesis that V-O bonds similar to vanadium trioxide in the as-grown VZO film changed to those similar to vanadium pentoxide after heat treatments over 500 °C. - Highlight: • Vanadium-doped zinc oxide (VZO) deposited on quartz by RF magnetron sputtering • VZO films were heat-treated up to 550 °C in N2 and O2 atmospheres. • Resistivity of the VZO films remains low at 450 °C in both N2 and O2 atmospheres. • Heat treatment over 500 °C results in change of dominant charge number of V in VZO

  18. Structural and magnetic properties of cobalt-doped ZnO thin films on sapphire (0 0 0 1) substrate deposited by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Shanying, E-mail: yshy_150@163.com [Laiwu Vocational and Technical College, Laiwu, Shandong Province, 271100 (China); Lv, Rongqing [Laiwu Vocational and Technical College, Laiwu, Shandong Province, 271100 (China); Wang, Changzheng [School of Physics Science and Information Engineering, Liaocheng University, Liaocheng, Shandong Province, 252059 (China); Liu, Yunyan [School of Science, Shandong University of Technology, Zibo, Shandong Province, 255049 (China); Song, Zeqing [Laiwu Vocational and Technical College, Laiwu, Shandong Province, 271100 (China)

    2013-12-05

    Highlights: •Co-doped ZnO thin films on sapphire (0 0 0 1) substrates were deposited. •ZnLMM Auger spectrum indicated that Zn interstitials existed in thin films. •The lattice constant increasing was ascribed to the stress and interstitial atoms. •The average moment per Co atom related to the distribution of Co{sup 2+} ions and defects. -- Abstract: Co-doped ZnO thin films on sapphire (0 0 0 1) substrates were deposited by PLD at various substrate temperatures in a one Pa oxygen ambient condition. The structural and magnetic properties of as-grown thin films were characterized by using XRD, UV–Visible absorption spectrophotometer, XPS and AGM. All samples possessed wurtzite hexagonal structure of ZnO. Co atoms incorporated into ZnO matrix and substituted for Zn in ZnO lattice, and Zn interstitials existed in as-grown thin films. The c-axis lattice constants of as-deposited thin films were larger than the standard data. Crystallization of as-prepared thin films increased and then decreased with substrate temperatures enhancing. All samples exhibited room-temperature ferromagnetism. The average moment per Co atom was much smaller than that of Co{sup 2+} (3d{sup 7}), due to the different distribution of Co{sup 2+} ions and defects, as well as the different defect concentrations in thin films.

  19. Hybrid ZnO nanowire/a-Si:H thin-film radial junction solar cells using nanoparticle front contacts

    International Nuclear Information System (INIS)

    Hydrothermally synthesized disordered ZnO nanowires were conformally coated with a-Si:H thin-films to fabricate three dimensional hybrid nanowire/thin-film structures. The a-Si:H layer formed a radial junction p-i-n diode solar cell around the ZnO nanowire. The cylindrical hybrid solar cells enhanced light scattering throughout the UV-visible-NIR spectrum (300 nm–800 nm) resulting in a 22% increase in short-circuit current density compared to the reference planar p-i-n device. A fill factor of 69% and a total power conversion efficiency of 6.5% were achieved with the hybrid nanowire solar cells using a spin-on indium tin oxide nanoparticle suspension as the top contact

  20. Humidity sensing properties of Ce-doped nanoporous ZnO thin film prepared by sol-gel method

    Institute of Scientific and Technical Information of China (English)

    Mansoor Anbia; Seyyed Ebrahim Moosavi Fard

    2012-01-01

    The humidity sensitive characteristics of the sensor fabricated from Ce-doped nanoporous ZnO by screen-printing on the alumina substrate with Ag-Pd interdigital electrodes were investigated at different sintering temperatures.The nanoporous thin films were prepared by sol-gel technique.It was found that the impedance of the sensor sintered at 600 ℃ changed more than four order of magnitude in the relative humidity (RH) range of 11%-95% at 25 ℃.The response and recovery time of the sensor were about 13 and 17 s,respectively.The sensor showed high humidity sensitivity,rapid response and recovery,prominent stability,good repeatability and narrow hysteresis loop.These results indicated that Ce-doped nanoporous ZnO thin films can be used in fabricating high-performance humidity sensors.

  1. Hybrid ZnO nanowire/a-Si:H thin-film radial junction solar cells using nanoparticle front contacts

    Energy Technology Data Exchange (ETDEWEB)

    Pathirane, M., E-mail: minoli.pathirane@uwaterloo.ca; Iheanacho, B.; Lee, C.-H.; Wong, W. S. [Department of Electrical and Computer Engineering, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1 (Canada); Tamang, A.; Knipp, D. [Research Center for Functional Materials and Nanomolecular Science, Jacobs University Bremen, Bremen 28759 (Germany); Lujan, R. [Electronic Materials and Devices Laboratory, Palo Alto Research Center, Palo Alto, California 93003 (United States)

    2015-10-05

    Hydrothermally synthesized disordered ZnO nanowires were conformally coated with a-Si:H thin-films to fabricate three dimensional hybrid nanowire/thin-film structures. The a-Si:H layer formed a radial junction p-i-n diode solar cell around the ZnO nanowire. The cylindrical hybrid solar cells enhanced light scattering throughout the UV-visible-NIR spectrum (300 nm–800 nm) resulting in a 22% increase in short-circuit current density compared to the reference planar p-i-n device. A fill factor of 69% and a total power conversion efficiency of 6.5% were achieved with the hybrid nanowire solar cells using a spin-on indium tin oxide nanoparticle suspension as the top contact.

  2. Antibacterial and barrier properties of oriented polymer films with ZnO thin films applied with atomic layer deposition at low temperatures

    International Nuclear Information System (INIS)

    Concerns on food safety, and need for high quality and extended shelf-life of packaged foods have promoted the development of antibacterial barrier packaging materials. Few articles have been available dealing with the barrier or antimicrobial properties of zinc oxide thin films deposited at low temperature with atomic layer deposition (ALD) onto commercial polymer films typically used for packaging purposes. The purpose of this paper was to study the properties of ZnO thin films compared to those of aluminum oxide. It was also possible to deposit ZnO thin films onto oriented polylactic acid and polypropylene films at relatively low temperatures using ozone instead of water as an oxidizing precursor for diethylzinc. Replacing water with ozone changed both the structure and the chemical composition of films deposited on silicon wafers. ZnO films deposited with ozone contained large grains covered and separated probably by a more amorphous and uniform layer. These thin films were also assumed to contain zinc salts of carboxylic acids. The barrier properties of a 25 nm ZnO thin film deposited with ozone at 100 °C were quite close to those obtained earlier with ALD Al2O3 of similar apparent thickness on similar polymer films. ZnO thin films deposited at low temperature indicated migration of antibacterial agent, while direct contact between ZnO and Al2O3 thin films and bacteria promoted antibacterial activity. - Highlights: • Thin films were grown from diethylzinc also with ozone instead of water at 70 and 100 °C. • ZnO films deposited with diethylzinc and ozone had different structures and chemistries. • Best barrier properties obtained with zinc oxide films close to those obtained with Al2O3 • Ozone as oxygen source provided better barrier properties at 100 °C than water. • Both aluminum and zinc oxide thin films showed antimicrobial activity against E. coli

  3. Effects of stabilizer ratio on photoluminescence properties of sol-gel ZnO nano-structured thin films

    International Nuclear Information System (INIS)

    Nanostructured ZnO thin films with different molar ratios of MEA to zinc acetate (0.5, 1.0, 1.5 and 2.0) have been deposited on glass substrates by a sol–gel dip coating technique. X-ray diffraction, Scanning Electron Microscopy, UV–visible spectrophotometry and photoluminescence spectroscopy have been employed to investigate the effect of MEA stabilizer ratio on structural, morphological, absorbance and emission properties of the ZnO thin films. Diffraction patterns have shown that all the films are polycrystalline and exhibit a wurtzite hexagonal structure. The c axis orientation has been enhanced with increasing stabilizer ratio. SEM micrographs have revealed that the morphology of the ZnO films depend on stabilizer ratio. The UV–visible absorption spectra have demonstrated that the optical absorption is affected by stabilizer ratio. The photoluminescence spectra have indicated one ultraviolet and two visible emission bands (green and red), while band intensities are found to be dependent on stabilizer ratio. ZnO thin films deposited at MEA ratio of 1.0 show the highest UV emission while the minimum UV emission intensity is observed in thin films deposited at ratio of 0.5 and the maximum green has been recorded for films deposited at MEA ratio of 2.0. - Highlight: • c axis orientation increases with increasing MEA ratio. • The increase of MEA ration from 0.5 to 1.0 enhances greatly the UV emission. • The larger IUV/Ivisible is obtained for the MEA to Zn ratio of 1:1. • The MEA ratio of 0.5 favors the formation of large density of Vzn. • The MEA ratio of 2.0 increases the Vo density

  4. Effects of stabilizer ratio on photoluminescence properties of sol-gel ZnO nano-structured thin films

    Energy Technology Data Exchange (ETDEWEB)

    Boudjouan, F. [Laboratoire de Génie de l' Environnement, Université de Bejaia, 06000 Bejaia (Algeria); Chelouche, A., E-mail: azeddinechelouche@gmail.com [Laboratoire de Génie de l' Environnement, Université de Bejaia, 06000 Bejaia (Algeria); Touam, T. [Laboratoire des Semi-conducteurs, Université Badji Mokhtar, BP 12, Annaba 23000 (Algeria); Djouadi, D. [Laboratoire de Génie de l' Environnement, Université de Bejaia, 06000 Bejaia (Algeria); Khodja, S. [Laboratoire des Semi-conducteurs, Université Badji Mokhtar, BP 12, Annaba 23000 (Algeria); Tazerout, M. [Laboratoire de Génie de l' Environnement, Université de Bejaia, 06000 Bejaia (Algeria); Ouerdane, Y. [Laboratoire Hubert Curien, Université Jean Monnet, 42 000 Saint-Etienne (France); Hadjoub, Z. [Laboratoire des Semi-conducteurs, Université Badji Mokhtar, BP 12, Annaba 23000 (Algeria)

    2015-02-15

    Nanostructured ZnO thin films with different molar ratios of MEA to zinc acetate (0.5, 1.0, 1.5 and 2.0) have been deposited on glass substrates by a sol–gel dip coating technique. X-ray diffraction, Scanning Electron Microscopy, UV–visible spectrophotometry and photoluminescence spectroscopy have been employed to investigate the effect of MEA stabilizer ratio on structural, morphological, absorbance and emission properties of the ZnO thin films. Diffraction patterns have shown that all the films are polycrystalline and exhibit a wurtzite hexagonal structure. The c axis orientation has been enhanced with increasing stabilizer ratio. SEM micrographs have revealed that the morphology of the ZnO films depend on stabilizer ratio. The UV–visible absorption spectra have demonstrated that the optical absorption is affected by stabilizer ratio. The photoluminescence spectra have indicated one ultraviolet and two visible emission bands (green and red), while band intensities are found to be dependent on stabilizer ratio. ZnO thin films deposited at MEA ratio of 1.0 show the highest UV emission while the minimum UV emission intensity is observed in thin films deposited at ratio of 0.5 and the maximum green has been recorded for films deposited at MEA ratio of 2.0. - Highlight: • c axis orientation increases with increasing MEA ratio. • The increase of MEA ration from 0.5 to 1.0 enhances greatly the UV emission. • The larger I{sub UV}/I{sub visible} is obtained for the MEA to Zn ratio of 1:1. • The MEA ratio of 0.5 favors the formation of large density of V{sub zn}. • The MEA ratio of 2.0 increases the V{sub o} density.

  5. Effect of the H2 plasma treatment of a seed layer on the synthesis of ZnO nanorods using a microwave hydrothermal method

    Science.gov (United States)

    Koo, Horng-Show; Lin, Ching-Cheng; Chen, Yao-Ju; Peng, Cheng-Hsiung; Chen, Mi

    2014-01-01

    The effect of H2 plasma treatment of a seed layer on the synthesis and characterization of zinc oxide (ZnO) nanorods is determined. Using an Al-doped ZnO (AZO) thin film as a seed layer, well-aligned ZnO nanorods are rapidly grown on an indium tin oxide (ITO)-coated glass substrate using a microwave hydrothermal method. The deposited AZO substrate was previously treated with H2 plasma. The effect of H2 plasma treatment of the seed layer on the alignment, growth rate, and crystallinity of the ZnO nanorods is determined. It is shown that the alignment and growth rate of the ZnO nanorods depend on the characteristics and roughness of the seed layer, which are improved by H2 plasma treatment. Various characterization methods such as X-ray diffraction (XRD), cathodoluminescence (CL), transmission electron microscopy (TEM), and X-ray photoemission spectroscopy (XPS) are used to determine the characteristic quality of the ZnO nanorods. A fundamental model of the effect of H2 plasma treatment on the seed layer and ZnO growth using a microwave hydrothermal process is also presented.

  6. Effect of Fe incorporation on the optical behavior of ZnO thin films prepared by sol-gel derived spin coating techniques

    Science.gov (United States)

    Rakkesh, R. Ajay; Malathi, R.; Balakumar, S.

    2013-02-01

    In this work, Fe doped Zinc Oxide (ZnO) thin films were fabricated on the glass substrate by sol-gel derived spin coating technique. X-ray Diffraction studies revealed that the obtained pure and Fe doped ZnO thin films were in the wurtzite and spinel phase respectively. The three well defined Raman lines at 432, 543 and 1091 cm-1 also confirmed the lattice structure of the ZnO thin film has wurtzite symmetry. While doping Fe atoms in the ZnO, there was a significant change in the phase from wurtzite to spinel structure; owing to Fe (III) ions being incorporated into the lattice through substitution of Zn (II) ions. Room temperature PL spectra showed that the role of defect mediated red emissions at 612 nm was due to radial recombination of a photogenerated hole with an electron that belongs to the Fe atoms, which were discussed in detail.

  7. Effects of deposition temperature on the crystallinity of Ga-doped ZnO thin films on glass substrates prepared by sputtering method

    International Nuclear Information System (INIS)

    The microstructural characterization of Ga-doped (5 at.%) ZnO thin film was conducted by a transmission electron microscopy study. The atomic arrangement of Ga-doped ZnO having an wurtzite structure was identified by the experimental HRTEM and Fourier filtered images as well as the electron diffractions. As a result, we have revealed that the orientation and defect density of Ga-doped ZnO thin films were greatly influenced by the deposition temperature, resulting in the variation of electrical property. In other words, the tendency forming a c-axis oriented texture grows up and the defects such as dislocations and stacking faults decrease, as the temperature of sputtering deposition increases. Consequently, the electrical properties of Ga-doped ZnO thin films can be controlled by the deposition temperature directly related with the defect density.

  8. Effect of the gate metal work function on water-gated ZnO thin-film transistor performance

    Science.gov (United States)

    Singh, Mandeep; Yusuf Mulla, Mohammad; Vittoria Santacroce, Maria; Magliulo, Maria; Di Franco, Cinzia; Manoli, Kyriaki; Altamura, Davide; Giannini, Cinzia; Cioffi, Nicola; Palazzo, Gerardo; Scamarcio, Gaetano; Torsi, Luisa

    2016-07-01

    ZnO thin films, prepared using a printing-compatible sol–gel method involving a thermal treatment below 400 °C, are proposed as active layers in water-gated thin-film transistors (WG-TFTs). The thin-film structure and surface morphology reveal the presence of contiguous ZnO crystalline (hexagonal wurtzite) with isotropic nano-grains as large as 10 nm characterized by a preferential orientation along the a-axis. The TFT devices are gated through a droplet of deionized water by means of electrodes characterized by different work functions. The high capacitance of the electrolyte allowed operation below 0.5 V. While the Ni, Pd, Au and Pt gate electrodes are electrochemically stable in the inspected potential range, electrochemical activity is revealed for the W one. Such an occurrence leads to an increase of capacitance (and current), which is ascribed to a high output current from the dissolution of a lower capacitance W-oxide layer. The environmental stability of the ZnO WG-TFTs is quite good over a period of five months.

  9. Controlling the processable ZnO and polythiophene interface for dye-sensitized thin film organic solar cells

    International Nuclear Information System (INIS)

    Dye-sensitized thin film hybrid solar cells (DS thin film solar cell) were fabricated by one-pot process using solution processable zinc oxide (ZnO) precursor as electron acceptor, ester-functionalized polythiophene copolymer as donor and a squaraine dye. Incorporation of slight amount of ester functionality (6%) in the regioregular poly-3-hexylthiophene (P3HT) main chain leads to enhancement in the photoconversion efficiency of the ester functionalized polymer (P3HT-E) from 0.8% to about 1% (AM1.5, 100 mw/cm2). Photocurrent associated with both of the P3HT-E (400–650 nm) and the squaraine dye (650–750 nm) were observed in incident photon to current efficiency curve of the DS thin film solar cell. This proves that the ZnO/dye/P3HT-E interface could be fabricated by one-pot coating process from ternary mixture based on a ZnO precursor. - Highlights: • Single step and one pot fabrication of dye-sensitized polymer-ZnO hybrid solar cells. • In situ generation of ZnO using its diethyl zinc precursor. • Enhanced photovoltaic performance by introduction of ester functionalized polymers. • Demonstration of far-red photon harvesting by polymer-dye-ZnO ternary blend

  10. Optical constants and near infrared emission of Er doped ZnO sol–gel thin films

    International Nuclear Information System (INIS)

    Erbium (Er) doped zinc oxide (ZnO) sol–gel thin films were deposited on glass substrate using the spin coating method. The effect of erbium concentration and annealing temperature on structural and optical properties was studied. The annealed film was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray spectrum (EDX), micro-Raman, photoluminescence (PL) and UV–vis spectroscopy. All the films showed a wurtzite structure of polycrystalline nature with an average crystal size of 27.44 nm at 500 °C and 29.28 nm at 600 °C. The Raman spectra confirmed the absence of secondary phases in the Er doped ZnO films and the longitudinal optical phonon mode was upto the fifth order. Densely packed surfaces of the films were observed from SEM images. The presence and distribution of Zn, O and Er elements in the deposited films were confirmed by EDX analysis. The calculated value of exciton binding energy of ZnO film was 60 meV with a maximum value of 72 meV being observed for Er doped films. The near infra-red emission peak was observed at 1.63 eV through PL spectra studies. The average transmission was 80% with the calculated value of optical band gap being 3.26–3.32 eV. An increase in the refractive index value predicts the substitutional incorporation of Er ions in ZnO with the maximum optical conductivity being observed in the UV region. - Highlights: • Higher exciton binding energy in the doped ZnO films. • Near infrared emission is observed and better than ZnO. • Refractive index is calculated by theoretical and experimental means. • Maximum optical conductivity in the UV region

  11. Optical constants and near infrared emission of Er doped ZnO sol–gel thin films

    Energy Technology Data Exchange (ETDEWEB)

    Vettumperumal, R. [P.G. and Research Department of Physics, Sri Paramakalyani College, Alwarkurichi 627412, Tamil Nadu (India); Kalyanaraman, S., E-mail: mayura_priya2003@yahoo.co.in [P.G. and Research Department of Physics, Sri Paramakalyani College, Alwarkurichi 627412, Tamil Nadu (India); Thangavel, R., E-mail: rtvel_au@yahoo.co.in [Department of Applied Physics, Indian School of Mines, Dhanbad (India)

    2015-02-15

    Erbium (Er) doped zinc oxide (ZnO) sol–gel thin films were deposited on glass substrate using the spin coating method. The effect of erbium concentration and annealing temperature on structural and optical properties was studied. The annealed film was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray spectrum (EDX), micro-Raman, photoluminescence (PL) and UV–vis spectroscopy. All the films showed a wurtzite structure of polycrystalline nature with an average crystal size of 27.44 nm at 500 °C and 29.28 nm at 600 °C. The Raman spectra confirmed the absence of secondary phases in the Er doped ZnO films and the longitudinal optical phonon mode was upto the fifth order. Densely packed surfaces of the films were observed from SEM images. The presence and distribution of Zn, O and Er elements in the deposited films were confirmed by EDX analysis. The calculated value of exciton binding energy of ZnO film was 60 meV with a maximum value of 72 meV being observed for Er doped films. The near infra-red emission peak was observed at 1.63 eV through PL spectra studies. The average transmission was 80% with the calculated value of optical band gap being 3.26–3.32 eV. An increase in the refractive index value predicts the substitutional incorporation of Er ions in ZnO with the maximum optical conductivity being observed in the UV region. - Highlights: • Higher exciton binding energy in the doped ZnO films. • Near infrared emission is observed and better than ZnO. • Refractive index is calculated by theoretical and experimental means. • Maximum optical conductivity in the UV region.

  12. Characterization of ZnO thin films grown on different p-Si substrate elaborated by solgel spin-coating method

    Energy Technology Data Exchange (ETDEWEB)

    Chebil, W., E-mail: Chbil.widad@live.fr [Laboratoire Physico-chimie des Matériaux, Unité de Service Commun de Recherche “High resolution X-ray diffractometer”, Département de Physique, Université de Monastir, Faculté des Sciences de Monastir, Avenue de l’Environnement, 5019 Monastir (Tunisia); Fouzri, A. [Laboratoire Physico-chimie des Matériaux, Unité de Service Commun de Recherche “High resolution X-ray diffractometer”, Département de Physique, Université de Monastir, Faculté des Sciences de Monastir, Avenue de l’Environnement, 5019 Monastir (Tunisia); Institut Supérieur des Sciences Appliquées et de Technologie de Sousse, Université de Sousse (Tunisia); Fargi, A. [Laboratoire de Microélectronique et Instrumentation, Faculté des Sciences de Monastir, Université de Monastir, Avenue de l’environnement, 5019 Monastir (Tunisia); Azeza, B.; Zaaboub, Z. [Laboratoire Micro-Optoélectroniques et Nanostructures, Faculté des Sciences de Monastir, Université de Monastir, Avenue de l' environnement, 5019 Monastir (Tunisia); and others

    2015-10-15

    Highlights: • High quality ZnO thin films grown on different p-Si substrates were successful obtained by sol–gel process. • PL measurement revealed that ZnO thin film grown on porous Si has the better optical quality. • I–V characteristics for all heterojunctions exhibit successful diode formation. • The diode ZnO/PSi shows a better photovoltaic effect under illumination with a maximum {sub Voc} of 0.2 V. - Abstract: In this study, ZnO thin films are deposited by sol–gel technique on p-type crystalline silicon (Si) with [100] orientation, etched silicon and porous silicon. The structural analyses showed that the obtained thin films were polycrystalline with a hexagonal wurtzite structure and preferentially oriented along the c-axis direction. Morphological study revealed the presence of rounded and facetted grains irregularly distributed on the surface of all samples. PL spectra at room temperature revealed that ZnO thin film grown on porous Si has a strong UV emission with low defects in the visible region comparing with ZnO grown on plat Si and etched Si surface. The heterojunction parameters were evaluated from the (I–V) under dark and illumination at room temperature. The ideality factor, barrier height and series resistance of heterojunction grown on different p-Si substrates are determined by using different methods. Best electrical properties are obtained for ZnO layer deposited on porous silicon.

  13. Influence of optical properties of ZnO thin-films deposited by spray pyrolysis and RF magnetron sputtering on the output performance of silicon solar cell

    International Nuclear Information System (INIS)

    ZnO thin-films were deposited by spray pyrolysis and RF magnetron sputtering techniques. The optical reflection of these thin-films is measured using UV-Vis spectrophotometer. The measured optical reflection data is used in PC-1D simulation software to study the output performance of commercial silicon wafer-based solar cell. As far as optical performance is concerned it could be demonstrated that the sprayed ZnO thin-film under laboratory conditions show equivalent performance compared to sputtered ZnO thin-film. The influence of optical properties of 65 nm thick zinc oxide thin-films deposited by vacuum and non-vacuum techniques on quantum efficiency and IV characteristics of commercial silicon-wafer based solar cell is studied and reported here.

  14. Photo-Patternable ZnO Thin Films Based on Cross-Linked Zinc Acrylate for Organic/Inorganic Hybrid Complementary Inverters.

    Science.gov (United States)

    Jeong, Yong Jin; An, Tae Kyu; Yun, Dong-Jin; Kim, Lae Ho; Park, Seonuk; Kim, Yebyeol; Nam, Sooji; Lee, Keun Hyung; Kim, Se Hyun; Jang, Jaeyoung; Park, Chan Eon

    2016-03-01

    Complementary inverters consisting of p-type organic and n-type metal oxide semiconductors have received considerable attention as key elements for realizing low-cost and large-area future electronics. Solution-processed ZnO thin-film transistors (TFTs) have great potential for use in hybrid complementary inverters as n-type load transistors because of the low cost of their fabrication process and natural abundance of active materials. The integration of a single ZnO TFT into an inverter requires the development of a simple patterning method as an alternative to conventional time-consuming and complicated photolithography techniques. In this study, we used a photocurable polymer precursor, zinc acrylate (or zinc diacrylate, ZDA), to conveniently fabricate photopatternable ZnO thin films for use as the active layers of n-type ZnO TFTs. UV-irradiated ZDA thin films became insoluble in developing solvent as the acrylate moiety photo-cross-linked; therefore, we were able to successfully photopattern solution-processed ZDA thin films using UV light. We studied the effects of addition of a tiny amount of indium dopant on the transistor characteristics of the photopatterned ZnO thin films and demonstrated low-voltage operation of the ZnO TFTs within ±3 V by utilizing Al2O3/TiO2 laminate thin films or ion-gels as gate dielectrics. By combining the ZnO TFTs with p-type pentacene TFTs, we successfully fabricated organic/inorganic hybrid complementary inverters using solution-processed and photopatterned ZnO TFTs. PMID:26840992

  15. Microwave-assisted low temperature fabrication of ZnO thin film electrodes for solar energy harvesting

    Energy Technology Data Exchange (ETDEWEB)

    Nirmal Peiris, T.A.; Sagu, Jagdeep S.; Hazim Yusof, Y.; Upul Wijayantha, K.G., E-mail: U.Wijayantha@lboro.ac.uk

    2015-09-01

    Metallic Zn thin films were electrodeposited on fluorine-doped tin oxide (FTO) glass substrates and oxidized under air by conventional radiant and microwave post-annealing methods to obtain ZnO thin film electrodes. The temperature of each post-annealing method was varied systematically and the photoelectrochemical (PEC) performance of electrodes was evaluated. The best photocurrent density achieved by the conventional radiant annealing method at 425 °C for 15 min was 93 μA cm{sup −2} at 1.23 V vs. NHE and the electrode showed an incident photon-to-electron conversion efficiency (IPCE) of 28.2%. X-ray diffractogram of this electrode showed that the oxidation of Zn to ZnO was not completed during the radiant annealing process as evident by the presence of metallic Zn in the electrode. For the electrode oxidized from Zn to ZnO under microwave irradiation, a photocurrent of 130 μA cm{sup −2} at 1.23 V vs. NHE and IPCE of 35.6% was observed after annealing for just 3 min, during which the temperature reached 250 °C. The photocurrent was 40% higher for the microwave annealed sample; this increase was attributed to higher surface area by preserving the nanostructure, confirmed by SEM surface topographical analysis, and better conversion yields to crystalline ZnO. Overall, it was demonstrated that oxidation of Zn to ZnO can be accomplished by microwave annealing five times faster than that of conventional annealing, thus resulting in a ~ 75% power saving. This study shows that microwave processing of materials offers significant economic and performance advantages for industrial scale up. - Highlights: • Conversion of Zn to ZnO by microwave and radiant annealing was conducted. • Microwave conversion was 5 times faster compared to radiant annealing. • Photoelectrochemical performance of microwave annealed ZnO was 40% higher. • Microwave annealing results in a 75% energy saving.

  16. ZnO Nanoparticles/Reduced Graphene Oxide Bilayer Thin Films for Improved NH3-Sensing Performances at Room Temperature.

    Science.gov (United States)

    Tai, Huiling; Yuan, Zhen; Zheng, Weijian; Ye, Zongbiao; Liu, Chunhua; Du, Xiaosong

    2016-12-01

    ZnO nanoparticles and graphene oxide (GO) thin film were deposited on gold interdigital electrodes (IDEs) in sequence via simple spraying process, which was further restored to ZnO/reduced graphene oxide (rGO) bilayer thin film by the thermal reduction treatment and employed for ammonia (NH3) detection at room temperature. rGO was identified by UV-vis absorption spectra and X-ray photoelectron spectroscope (XPS) analyses, and the adhesion between ZnO nanoparticles and rGO nanosheets might also be formed. The NH3-sensing performances of pure rGO film and ZnO/rGO bilayer films with different sprayed GO amounts were compared. The results showed that ZnO/rGO film sensors exhibited enhanced response properties, and the optimal GO amount of 1.5 ml was achieved. Furthermore, the optimal ZnO/rGO film sensor showed an excellent reversibility and fast response/recovery rate within the detection range of 10-50 ppm. Meanwhile, the sensor also displayed good repeatability and selectivity to NH3. However, the interference of water molecules on the prepared sensor is non-ignorable; some techniques should be researched to eliminate the effect of moisture in the further work. The remarkably enhanced NH3-sensing characteristics were speculated to be attributed to both the supporting role of ZnO nanoparticles film and accumulation heterojunction at the interface between ZnO and rGO. Thus, the proposed ZnO/rGO bilayer thin film sensor might give a promise for high-performance NH3-sensing applications. PMID:26956599

  17. ZnO Nanoparticles/Reduced Graphene Oxide Bilayer Thin Films for Improved NH3-Sensing Performances at Room Temperature

    Science.gov (United States)

    Tai, Huiling; Yuan, Zhen; Zheng, Weijian; Ye, Zongbiao; Liu, Chunhua; Du, Xiaosong

    2016-03-01

    ZnO nanoparticles and graphene oxide (GO) thin film were deposited on gold interdigital electrodes (IDEs) in sequence via simple spraying process, which was further restored to ZnO/reduced graphene oxide (rGO) bilayer thin film by the thermal reduction treatment and employed for ammonia (NH3) detection at room temperature. rGO was identified by UV-vis absorption spectra and X-ray photoelectron spectroscope (XPS) analyses, and the adhesion between ZnO nanoparticles and rGO nanosheets might also be formed. The NH3-sensing performances of pure rGO film and ZnO/rGO bilayer films with different sprayed GO amounts were compared. The results showed that ZnO/rGO film sensors exhibited enhanced response properties, and the optimal GO amount of 1.5 ml was achieved. Furthermore, the optimal ZnO/rGO film sensor showed an excellent reversibility and fast response/recovery rate within the detection range of 10-50 ppm. Meanwhile, the sensor also displayed good repeatability and selectivity to NH3. However, the interference of water molecules on the prepared sensor is non-ignorable; some techniques should be researched to eliminate the effect of moisture in the further work. The remarkably enhanced NH3-sensing characteristics were speculated to be attributed to both the supporting role of ZnO nanoparticles film and accumulation heterojunction at the interface between ZnO and rGO. Thus, the proposed ZnO/rGO bilayer thin film sensor might give a promise for high-performance NH3-sensing applications.

  18. Structural and Optical Properties of ZnO Thin Film Prepared by Oxidation of Zn Metal Powders

    International Nuclear Information System (INIS)

    High quality ZnO nano structures have been fabricated at room temperature by a simple vacuum thermal evaporator from metallic Zn powders (99.999 % purity) on a silicon (100) substrate. The Zn thin films were then transferred into a thermal tube furnace for oxidation at 700 degree Celsius for different time durations. Time was found to be a critical factor in the synthesis. This was followed by characterization of their morphological, structural and optical properties. The morphology of the grown ZnO nano structures exhibited several large grains, which increased gradually with increasing oxidation time. The crystallinity of the grown nano structures was investigated using X-ray diffraction, revealing that the synthesized ZnO was in hexagonal wurtzite phase. The photoluminescence (PL) spectra of the fabricated ZnO nano structures showed high intensity peak in the UV region due to near-band-edge (NBE) emission in which the structures oxidized for 30 min showing highest intensity. (author)

  19. Electrodeposition of CdSe coatings on ZnO nanowire arrays for extremely thin absorber solar cells

    International Nuclear Information System (INIS)

    We report on electrodeposition of CdSe coatings onto ZnO nanowire arrays and determine the effect of processing conditions on material properties such as morphology and microstructure. CdSe-coated ZnO nanowire arrays have potential use in extremely thin absorber (ETA) solar cells, where CdSe absorbs visible light and injects photoexcited electrons into the ZnO nanowires. We show that room-temperature electrodeposition enables growth of CdSe coatings that are highly crystalline, uniform, and conformal with precise control over thickness and microstructure. X-ray diffraction and transmission electron microscopy show nanocrystalline CdSe in both hexagonal and cubic phases with grain size ∼5 nm. Coating morphology depends on electrodeposition current density. Uniform and conformal coatings were achieved using moderate current densities of ∼2 mA cm-2 for nanowires with roughness factor of ∼10, while lower current densities resulted in sparse nucleation and growth of larger, isolated islands. Electrodeposition charge density controls the thickness of the CdSe coating, which was exploited to investigate the evolution of the morphology at early stages of nucleation and growth. UV-vis transmission spectroscopy and photoelectrochemical solar cell measurements demonstrate that CdSe effectively sensitizes ZnO nanowires to visible light.

  20. Photovoltaic Properties of Co-doped ZnO Thin Film on Glass Substrate

    International Nuclear Information System (INIS)

    Cobalt (Co) 0.4 mol doped zinc oxide (ZnO) fine powder was prepared by solid state mixed oxide route. Phase formation and crystal structure of Co-doped ZnO (CZO) powder were examined by X-ray diffraction (XRD). Scanning Electron Microscopy (SEM) was used to observe the micro structure of Co doped ZnO powder. Energy Dispersive X-ray Fluorescent (EDXRF) technique gave the elemental content of cobalt and zinc. Co-doped ZnO film was formed on glass substrate by spin coating technique. Photovoltaic properties of CZO/glass cell were measured.

  1. Tuning of structural, optical, and magnetic properties of ultrathin and thin ZnO nanowire arrays for nano device applications

    Science.gov (United States)

    Shrama, Satinder K.; Saurakhiya, Neelam; Barthwal, Sumit; Kumar, Rudra; Sharma, Ashutosh

    2014-03-01

    One-dimensional (1-D) ultrathin (15 nm) and thin (100 nm) aligned 1-D (0001) and ([InlineEquation not available: see fulltext.]) oriented zinc oxide (ZnO) nanowire (NW) arrays were fabricated on copper substrates by one-step electrochemical deposition inside the pores of polycarbonate membranes. The aspect ratio dependence of the compressive stress because of the lattice mismatch between NW array/substrate interface and crystallite size variations is investigated. X-ray diffraction results show that the polycrystalline ZnO NWs have a wurtzite structure with a = 3.24 Å, c = 5.20 Å, and [002] elongation. HRTEM and SAED pattern confirmed the polycrystalline nature of ultrathin ZnO NWs and lattice spacing of 0.58 nm. The crystallite size and compressive stress in as-grown 15- and 100-nm wires are 12.8 nm and 0.2248 GPa and 22.8 nm and 0.1359 GPa, which changed to 16.1 nm and 1.0307 GPa and 47.5 nm and 1.1677 GPa after annealing at 873 K in ultrahigh vacuum (UHV), respectively. Micro-Raman spectroscopy showed that the increase in E2 (high) phonon frequency corresponds to much higher compressive stresses in ultrathin NW arrays. The minimum-maximum magnetization magnitude for the as-grown ultrathin and thin NW arrays are approximately 8.45 × 10-3 to 8.10 × 10-3 emu/g and approximately 2.22 × 10-7 to 2.190 × 10-7 emu/g, respectively. The magnetization in 15-nm NW arrays is about 4 orders of magnitude higher than that in the 100 nm arrays but can be reduced greatly by the UHV annealing. The origin of ultrathin and thin NW array ferromagnetism may be the exchange interactions between localized electron spin moments resulting from oxygen vacancies at the surfaces of ZnO NWs. The n-type conductivity of 15-nm NW array is higher by about a factor of 2 compared to that of the 100-nm ZnO NWs, and both can be greatly enhanced by UHV annealing. The ability to tune the stresses and the structural and relative occupancies of ZnO NWs in a wide range by annealing has important

  2. Optical characterization of Mg-doped ZnO thin films deposited by RF magnetron sputtering technique

    Science.gov (United States)

    Singh, Satyendra Kumar; Hazra, Purnima; Tripathi, Shweta; Chakrabarti, P.

    2016-05-01

    This paper reports the in-depth analysis on optical characteristics of magnesium (Mg) doped zinc oxide (ZnO) thin films grown on p-silicon (Si) substrates by RF magnetron sputtering technique. The variable angle ellipsometer is used for the optical characterization of as-deposited thin films. The optical reflectance, transmission spectra and thickness of as-deposited thin films are measured in the spectral range of 300-800 nm with the help of the spectroscopic ellipsometer. The effect of Mg-doping on optical parameters such as optical bandgap, absorption coefficient, absorbance, extinction coefficient, refractive Index and dielectric constant for as-deposited thin films are extracted to show its application in optoelectronic and photonic devices.

  3. Reactive magnetron sputtering of Ni doped ZnO thin film: Investigation of optical, structural, mechanical and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Siddheswaran, R., E-mail: rajendra@ntc.zcu.cz [New Technologies Research Centre, University of West Bohemia, Plzeň 30614 (Czech Republic); Netrvalová, Marie; Savková, Jarmila; Novák, Petr; Očenášek, Jan; Šutta, Pavol [New Technologies Research Centre, University of West Bohemia, Plzeň 30614 (Czech Republic); Kováč, Jaroslav [Slovak University of Technology, Faculty of Electrical Engineering and Information Technology, Il’kovičova 3, 81219 Bratislava (Slovakia); Jayavel, R. [Centre for Nanoscience and Technology, Anna University, Chennai 600025 (India)

    2015-07-05

    Highlights: • Highly preferred oriented [0 0 1] thin film columnar structure in ZnO:Ni from RF sputtering. • XRD confirmed the preferred orientation of ZnO structure from the only observed (0 0 2) plane. • Variation of refractive indices and optical band gap by doping of Ni in ZnO were studied. • Surface morphology and mechanical properties of the thin films were studied by SEM and AFM. • Critical concentration of Ni for the rise and enhancement of ferromagnetism was studied by VSM. - Abstract: Nickel doped ZnO (ZnO:Ni) thin films are considered to be promising materials for optoelectronic applications. The doping of transition metal ion modifies the optical and physical properties of the materials. Therefore, studies on optical and physical properties are important for such applications. In the present work, the ZnO:Ni thin films with different Ni concentrations were deposited on Si (1 0 0) and corning glass substrates at 400 °C by reactive magnetron sputtering using Ar and O{sub 2} gas mixture. The (0 0 2) growth plane of the ZnO was identified from the X-ray diffraction experiment. It was also confirmed that the films exhibit strong preferred orientation (texture) of crystalline columns in the direction [0 0 1] perpendicular to the substrate surface. The optical transmittance, band gap, and refractive indices of the thin films were studied by UV–Vis spectroscopy, photoluminescence and spectroscopic ellipsometry. The optical band gap and refractive index of the thin films decreased with increase of Ni content. The Raman and FT-IR spectroscopic studies were used to explain the modes of vibrations of the functional groups in the material. The surface topography, grain size, distribution, and fine structure of the thin films were analyzed by using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The hardness of the films was measured using a nanoindenter coupled with AFM. The growth of ferromagnetism by the effect of Ni content was

  4. Effects of oxygen ion implantation in spray-pyrolyzed ZnO thin films

    Science.gov (United States)

    Vijayakumar, K. P.; Ratheesh Kumar, P. M.; Sudha Kartha, C.; Wilson, K. C.; Singh, F.; Nair, K. G. M.; Kashiwaba, Y.

    2006-04-01

    ZnO thin films, prepared using the chemical spray pyrolysis technique, were implanted using 100 keV O+ ions. Both pristine and ion-implanted samples were characterized using X-ray diffraction, optical absorption, electrical resistivity measurements, thermally stimulated current measurements and photoluminescence. Samples retained their crystallinity even after irradiation at a fluence of 1015 ions/cm2. However, at a still higher fluence of 2 × 1016 ions/cm2, the films became totally amorphous. The optical absorption edge remained unaffected by implantation and optical absorption spectra indicated two levels at 460 and 510 nm. These were attributed to defect levels corresponding to zinc vacancies (VZn) and oxygen antisites (OZn), respectively. Pristine samples had a broad photoluminescence emission centred at 517 nm, which was depleted on implantation. In the case of implanted samples, two additional emissions appeared at 425 and 590 nm. These levels were identified as due to zinc vacancies (VZn) and oxygen vacancies (VO), respectively. The electrical resistivity of implanted samples was much higher than that of pristine, while photosensitivity decreased to a very low value on implantation. This can be utilized in semiconductor device technology for interdevice isolation. Hall measurements showed a marked decrease in mobility due to ion implantation, while carrier concentration slightly increased.

  5. Study of Ultraviolet Emission Spectra in ZnO Thin Films

    Directory of Open Access Journals (Sweden)

    Y. M. Lu

    2013-01-01

    Full Text Available Photoluminescence (PL of ZnO thin films prepared on c-Al2O3 substrates by pulsed laser deposition (PLD are investigated. For all samples, roomtemperature (RT spectra show a strong band-edge ultraviolet (UV emission with a pronounced low-energy band tail. The origin of this UV emission is analyzed by the temperature dependence of PL spectra. The result shows that the UV emission at RT contains different recombination processes. At low temperature donor-bound exciton (D0X emission plays a major role in PL spectra, while the free exciton transition (FX gradually dominates the spectrum with increasing temperatures. It notes that at low temperature an emission band (FA appears in low energy side of D0X and FX and can survive up to RT. Further confirmation shows that the origin of the band FA can be attributed to the transitions of conduction band electrons to acceptors (e, A0, in which the acceptor binding energy is estimated to be approximately 121 meV. It is concluded that at room temperature UV emission originates from the corporate contributions of the free exciton and free electrons-to-acceptor transitions.

  6. Inverter Circuits Using ZnO Nanoparticle Based Thin-Film Transistors for Flexible Electronic Applications

    Directory of Open Access Journals (Sweden)

    Fábio F. Vidor

    2016-08-01

    Full Text Available Innovative systems exploring the flexibility and the transparency of modern semiconducting materials are being widely researched by the scientific community and by several companies. For a low-cost production and large surface area applications, thin-film transistors (TFTs are the key elements driving the system currents. In order to maintain a cost efficient integration process, solution based materials are used as they show an outstanding tradeoff between cost and system complexity. In this paper, we discuss the integration process of ZnO nanoparticle TFTs using a high-k resin as gate dielectric. The performance in dependence on the transistor structure has been investigated, and inverted staggered setups depict an improved performance over the coplanar device increasing both the field-effect mobility and the ION/IOFF ratio. Aiming at the evaluation of the TFT characteristics for digital circuit applications, inverter circuits using a load TFT in the pull-up network and an active TFT in the pull-down network were integrated. The inverters show reasonable switching characteristics and V/V gains. Conjointly, the influence of the geometry ratio and the supply voltage on the devices have been analyzed. Moreover, as all integration steps are suitable to polymeric templates, the fabrication process is fully compatible to flexible substrates.

  7. Structural, morphological and optical studies of ripple-structured ZnO thin films

    Science.gov (United States)

    Navin, Kumar; Kurchania, Rajnish

    2015-11-01

    Ripple-structured ZnO thin films were prepared on Si (100) substrate by sol-gel spin-coating method with different heating rates during preheating process and finally sintered at 500 °C for 2 h in ambient condition. The structural, morphological and photoluminescence (PL) properties of the nanostructured films were analyzed by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and PL spectroscopy. XRD analysis revealed that films have hexagonal wurtzite structure and texture coefficient increases along (002) plane with preheating rate. The faster heating rate produced higher crystallization and larger average crystallite size. The AFM and SEM images indicate that all the films have uniformly distributed ripple structure with skeletal branches. The number of ripples increases, while the rms roughness, amplitude and correlation length of the ripple structure decrease with preheating rates. The PL spectra show the presence of different defects in the structure. The ultraviolet emission improved with the heating rate which indicates its better crystallinity.

  8. Deposition and characterization of ZnO thin films by modified pulsed-spray pyrolysis

    International Nuclear Information System (INIS)

    Zinc oxide (ZnO) thin films were deposited using modified pulsed-spray pyrolysis on glass substrates. Depositions were carried out using N2 as the carrier gas and analysed with respect to the rate of deposition. X-ray analysis revealed the presence of mixed crystallization with a nanocrystalline structure of about 6.9 nm dispersed in the amorphous matrix. A negative trend between the bandgap and resistivity was observed with the decrease in the deposition rate. A lowest bandgap of 3.1 eV with a resistivity value of 1.6 × 10−2 Ω cm was achieved at a lowest deposition rate of 1.3 nm min−1. Hot-probe measurement revealed the p-type conductivity for the film deposited at a lowest deposition rate of 1.3 nm min−1. Details about the influence of pulsed-spray deposition for the achievement of this negative trend between bandgap and resistivity will be discussed in this paper

  9. Bias-voltage dependent ultraviolet photodetectors prepared by GaO{sub x} + ZnO mixture phase nanocrystalline thin films

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Rongxin, E-mail: rxwang2008@sinano.ac.cn [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123 (China); Yang, Lechen [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123 (China); Xu, Shijie [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123 (China); Department of Physics and HKU-CAS Joint Laboratory on New Materials, The University of Hong Kong, Pokfulam Road, Hong Kong (China); Zhang, Xiaodong; Dong, Xue; Zhao, Yingchun; Fu, Kai; Zhang, Baoshun; Yang, Hui [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123 (China)

    2013-07-25

    Highlights: •GaO{sub x} + ZnO thin films sputtered and annealed exhibit interesting and unique optical properties, especially deep UV photo response. •GaO{sub x} + ZnO thin films can be used to fabricate efficient deep UV photodetectors. •The mixture phase nature of GaO{sub x} + ZnO thin films is revealed to be responsible for the unique characteristics of the photodetectors. •Two bands in UV range can be adjusted by a applied voltage when the PDs were fabricated using the mixture phase nature of GaO{sub x} + ZnO thin films. -- Abstract: Ultraviolet (UV) photodetectors were prepared by using the GaO{sub x} + ZnO mixture phase thin films sputtered on sapphire as the photoresponse layer. The devices show good photoresponse in UV range. More interestingly, the device responsivity in the wavelength less than 280 nm range rapidly increases with increasing the applied voltage and becomes dominant for the bias ⩾3.0 V. X-ray diffraction, absorption and cathodoluminescence measurements firmly reveal the mixture phases in the thin films. Electric field dependent detrapping of photo-excited carriers in nanocrystals in the films shall be responsible for the observed bias-voltage dependent deep UV photoresponse of the devices.

  10. Theoretical study of the multiferroic properties in M-doped (M=Co, Cr, Mg) ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Bahoosh, S.G. [Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle (Germany); Apostolov, A.T. [University of Architecture, Civil Engineering and Geodesy, Faculty of Hydrotechnics, Department of Physics, 1, Hristo Smirnenski Blvd., 1046 Sofia (Bulgaria); Apostolova, I.N. [University of Forestry, Faculty of Forest Industry, 10, Kl. Ohridsky Blvd., 1756 Sofia (Bulgaria); Trimper, S. [Institute of Physics, Martin-Luther-University, D-06099 Halle (Germany); Wesselinowa, Julia M. [University of Sofia, Department of Physics, Blvd. J. Bouchier 5, 1164 Sofia (Bulgaria)

    2015-01-01

    The origin of multiferroism is still an open problem in ZnO. We propose a microscopic model to clarify the occurrence of multiferroism in this material. Using Green's function technique we study the influence of ion doping and size effects on the magnetization and polarization of ZnO thin films. The calculations for magnetic Co- and Cr-ions are based on the s–d model, the transverse Ising model in terms of pseudo-spins and a biquadratic magnetoelectric coupling, whereas in case of nonmagnetic Mg-ions the model takes into account the Coulomb interaction and an indirect coupling between the pseudo-spins via the conduction electrons. We show that the magnetization M exhibits a maximum for a fixed concentration of the doping ions. Furthermore M increases with decreasing film thickness N. The polarization increases with increasing concentration of the dopant and decreasing N. The results are in good agreement with the experimental data. - Highlights: • The paper analyzes the multiferroic properties of doped ZnO thin films by a microscopic model. • The magnetization exhibits a maximum at a fixed doping concentration. • The polarization increases with growing dopant concentration. • The ferroelectric transition temperature is enhanced for increasing dopant concentration.

  11. Effects of UV-ozone treatment on radio-frequency magnetron sputtered ZnO thin films

    International Nuclear Information System (INIS)

    The effects of UV-ozone treatment on ZnO thin films prepared by using radio-frequency magnetron sputtering are investigated. Decrease in the density of oxygen vacancy as well as increase in the density of oxygen interstitial were inferred from the UV-ozone treated samples. It was also found that a considerable difference in the work function (0.25 eV) is induced by UV-ozone treatment implying a shift in Fermi level. This shift was confirmed by capacitance-voltage measurements, which demonstrated that the boundary between the inversion region and the depletion region of a ZnO-based metal-oxide-semiconductor (MOS) capacitor positively shifts when UV ozone treated. Our results clearly indicate that the threshold voltage of a thin film transistor can be adjusted by modifying the ZnO surface via UV ozone treatment. MOS capacitors fabricated with UV-ozone treated HfO2 and/or ZnO also yielded a smaller leakage current (∼ 73%-90% smaller) and a larger breakdown voltage (∼ 8%-11% larger). The physical mechanism behind the effect of the UV ozone treatment is addressed in this study with the help of X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy.

  12. Improvement in the negative bias temperature stability of ZnO based thin film transistors by Hf and Sn doping

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Woong-Sun; Moon, Yeon-Keon; Kim, Kyung-Taek; Shin, Sae-Young [Department of Materials Science and Engineering, Hanyang University, 17 Haengdang-dong, Seoungdong-ku, Seoul 133-791 (Korea, Republic of); Ahn, Byung Du; Lee, Je-Hun [Samsung Electronics Co., Ltd., LCD Business, San 24 Nongseo-dong, Giheung-gu, Yongin, Gyonggi-do 446-711 (Korea, Republic of); Park, Jong-Wan, E-mail: jwpark@hanyang.ac.kr [Department of Materials Science and Engineering, Hanyang University, 17 Haengdang-dong, Seoungdong-ku, Seoul 133-791 (Korea, Republic of)

    2011-08-01

    We assessed the performance of ZnO TFTs using Si{sub 3}N{sub 4} gate dielectrics after various treatments. A remarkable improvement in the transfer characteristics was obtained for the O{sub 2} plasma treated ZnO TFT and SiO{sub 2} interlayer deposited ZnO TFT. Also, we developed amorphous hafnium-zinc-tin oxide (HZTO) thin film transistors (TFTs) and investigated the influence of hafnium (Hf) doping on the electrical characteristics of the hafnium-zinc oxide (HZO) thin film transistors. Doping with Hf can decrease the carrier concentration, which may result from a decrease of the field effect mobility, and reduce oxygen vacancy related defects in the interfacial layer. Adding tin (Sn) can suppress the growth of a crystalline phase in the HZTO films. The HZTO TFTs exhibited good electrical properties with a field effect mobility of 14.33 cm{sup 2}/Vs, a subthreshold swing of 0.97 V/decade, and a high I{sub ON/OFF} ratio of over 10{sup 9}.

  13. Influence of oxygen partial pressure on the microstructural and magnetic properties of Er-doped ZnO thin films

    Directory of Open Access Journals (Sweden)

    Wei-Bin Chen

    2015-06-01

    Full Text Available Er-doped ZnO thin films have been prepared by using inductively coupled plasma enhanced physical vapor deposition at different O2:Ar gas flow ratio (R = 0:30, 1:30, 1:15, 1:10 and 1:6. The influence of oxygen partial pressure on the structural, optical and magnetic properties was studied. It is found that an appropriate oxygen partial pressure (R=1:10 can produce the best crystalline quality with a maximum grain size. The internal strain, estimated by fitting the X-ray diffraction peaks, varied with oxygen partial pressure during growth. PL measurements show that plenty of defects, especially zinc vacancy, exist in Er-doped ZnO films. All the samples show room-temperature ferromagnetism. Importantly, the saturation magnetization exhibits similar dependency on oxygen partial pressure with the internal strain, which indicates that internal strain has an important effect on the magnetic properties of Er-doped ZnO thin films.

  14. Influence of oxygen partial pressure on the microstructural and magnetic properties of Er-doped ZnO thin films

    Science.gov (United States)

    Chen, Wei-Bin; Liu, Xue-Chao; Li, Fei; Chen, Hong-Ming; Zhou, Ren-Wei; Shi, Er-Wei

    2015-06-01

    Er-doped ZnO thin films have been prepared by using inductively coupled plasma enhanced physical vapor deposition at different O2:Ar gas flow ratio (R = 0:30, 1:30, 1:15, 1:10 and 1:6). The influence of oxygen partial pressure on the structural, optical and magnetic properties was studied. It is found that an appropriate oxygen partial pressure (R=1:10) can produce the best crystalline quality with a maximum grain size. The internal strain, estimated by fitting the X-ray diffraction peaks, varied with oxygen partial pressure during growth. PL measurements show that plenty of defects, especially zinc vacancy, exist in Er-doped ZnO films. All the samples show room-temperature ferromagnetism. Importantly, the saturation magnetization exhibits similar dependency on oxygen partial pressure with the internal strain, which indicates that internal strain has an important effect on the magnetic properties of Er-doped ZnO thin films.

  15. 7-Octenyltrichrolosilane/trimethyaluminum hybrid dielectrics fabricated by molecular-atomic layer deposition on ZnO thin film transistors

    Science.gov (United States)

    Huang, Jie; Lee, Mingun; Lucero, Antonio T.; Cheng, Lanxia; Ha, Min-Woo; Kim, Jiyoung

    2016-06-01

    We demonstrate the fabrication of 7-octenytrichlorosilane (7-OTS)/trimethylaluminum (TMA) organic–inorganic hybrid films using molecular-atomic layer deposition (MALD). The properties of 7-OTS/TMA hybrid films are extensively investigated using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and electrical measurements. Our results suggest that uniform and smooth amorphous hybrid thin films with excellent insulating properties are obtained using the MALD process. Films have a relatively high dielectric constant of approximately 5.0 and low leakage current density. We fabricate zinc oxide (ZnO) based thin film transistors (TFTs) using 7-OTS/TMA hybrid material as a back gate dielectric with the top ZnO channel layer deposited in-situ via MALD. The ZnO TFTs exhibit a field effect mobility of approximately 0.43 cm2 V‑1 s‑1, a threshold voltage of approximately 1 V, and an on/off ratio of approximately 103 under low voltage operation (from ‑3 to 9 V). This work demonstrates an organic–inorganic hybrid gate dielectric material potentially useful in flexible electronics application.

  16. Modification of opto-electronic properties of ZnO by incorporating metallic tin for buffer layer in thin film solar cells

    International Nuclear Information System (INIS)

    In this report, the effect of incorporation of metallic tin (Sn) on opto-electronic properties of ZnO thin films is presented. ZnO thin films were deposited through ‘automated chemical spray pyrolysis’ (CSP) technique; later different quantities of ‘Sn’ were evaporated on it and subsequently annealed. Vacuum annealing showed a positive effect on crystallinity of films. Creation of sub band gap levels due to ‘Sn’ diffusion was evident from the absorption and PL spectra. The tin incorporated films showed good photo response in visible region. Tin incorporated ZnO thin films seem to satisfy the desirable criteria for buffer layer in thin film solar cells

  17. Modification of opto-electronic properties of ZnO by incorporating metallic tin for buffer layer in thin film solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Deepu, D. R.; Jubimol, J.; Kartha, C. Sudha; Louis, Godfrey; Vijayakumar, K. P., E-mail: kpv@cusat.ac.in [Department of Physics, Cochin University of Science and Technology, Cochin-682022 (India); Kumar, K. Rajeev [Department of Instrumentation, Cochin University of Science and Technology, Cochin-682022 (India)

    2015-06-24

    In this report, the effect of incorporation of metallic tin (Sn) on opto-electronic properties of ZnO thin films is presented. ZnO thin films were deposited through ‘automated chemical spray pyrolysis’ (CSP) technique; later different quantities of ‘Sn’ were evaporated on it and subsequently annealed. Vacuum annealing showed a positive effect on crystallinity of films. Creation of sub band gap levels due to ‘Sn’ diffusion was evident from the absorption and PL spectra. The tin incorporated films showed good photo response in visible region. Tin incorporated ZnO thin films seem to satisfy the desirable criteria for buffer layer in thin film solar cells.

  18. Surfactant mediated one- and two-dimensional ZnO nanostructured thin films for dye sensitized solar cell application

    International Nuclear Information System (INIS)

    One-dimensional (1D) and two-dimensional (2D) nanostructured zinc oxide (ZnO) thin films were electrodeposited from aqueous zinc chloride on FTO glass substrates. The effects of organic surfactant such as cetyltrimethyl ammonium bromide (CTAB) and polyvinyl alcohol (PVA) on structural, morphological, crystal quality and optical properties of electrodeposited ZnO films were investigated. The x-ray diffraction pattern revealed that the prepared thin films were pure wutrzite hexagonal structure. The thin films deposited using organic surfactant in this work showed different morphologies such as nanoplatelet and flower. The hexagonal platelet and flower-like nanostructures were obtained in the presence of CTAB and PVA surfactant, respectively. The crystal quality and atomic vacancies of the prepared nanostructured thin films were investigated by micro Raman spectroscopic technique. The emission properties and optical quality of the films were studied by photoluminescence spectrometry. PEMA-LiClO4-EC gel polymer electrolyte has been used to replace the liquid electrolyte for reducing the leakage problem. Graphene counter electrode was used as an alternative for platinum electrode. Eosin yellow dye was used as a sensitizer. J–V characterizations were carried out for different 1D and 2D nanostructures. The nanoflower structure exhibited higher efficiency (η = 0.073%) than the other two nanostructures. (paper)

  19. Low pressure chemical vapour deposition of ZnO layers for thin-film solar cells. Temperature-induced morphological changes

    Energy Technology Data Exchange (ETDEWEB)

    Fay, S.; Kroll, U.; Bucher, C.; Vallat-Sauvain, E.; Shah, A. [Institut de Microtechnique IMT, Thin-film Silicon and Photovoltaics Laboratory, Rue A.-L. Breguet 2, 2000 Neuchatel (Switzerland)

    2005-03-31

    Zinc oxide (ZnO) is now often used as a transparent conductive oxide for contacts in thin-film silicon solar cells. This paper presents a study of ZnO material deposited by the low-pressure chemical vapour deposition technique, in a pressure range below the pressures usually applied for the deposition of this kind of material. A temperature series has been deposited, showing a morphological transition around 150{sup o}C. ZnO samples deposited with temperatures just higher than this transition are constituted of large grains highly oriented along a single crystallographic orientation. These 'monocrystals' lead to low resistivity values, showing a clear correlation between the size of the surface grains and the electrical performance of corresponding films. Additionally, these large grains also yield ZnO layers with high transparency and high light-scattering power, specially suitable for solar cell technology based on thin-film silicon.

  20. Effect of different annealing temperature on Sb-doped ZnO thin films prepared by pulsed laser deposition on sapphire substrates

    International Nuclear Information System (INIS)

    Influence of annealing temperature on the properties of Sb-doped ZnO thin films were studied. Hall measurement results indicated that the Sb-doped ZnO annealed at 950 deg. C was p-type conductivity. X-ray diffraction (XRD) results indicated that the Sb-doped ZnO thin films prepared at the experiments are high c-axis oriented. It was worth noting that p-type sample had the worst crystallinity. The measurements of low-temperature photoluminescence (PL) spectra indicate that the sample annealed at the temperatures of 950 deg. C showed strong acceptor-bound exciton (A0X) emission, and confirmed that it is related to Sb-doping by comparing with the undoped ZnO low-temperature PL spectrum.

  1. Title: Using Alignment and 2D Network Simulations to Study Charge Transport Through Doped ZnO Nanowire Thin Film Electrodes

    KAUST Repository

    Phadke, Sujay

    2011-09-30

    Factors affecting charge transport through ZnO nanowire mat films were studied by aligning ZnO nanowires on substrates and coupling experimental measurements with 2D nanowire network simulations. Gallium doped ZnO nanowires were aligned on thermally oxidized silicon wafer by shearing a nanowire dispersion in ethanol. Sheet resistances of nanowire thin films that had current flowing parallel to nanowire alignment direction were compared to thin films that had current flowing perpendicular to nanowire alignment direction. Perpendicular devices showed ∼5 fold greater sheet resistance than parallel devices supporting the hypothesis that aligning nanowires would increase conductivity of ZnO nanowire electrodes. 2-D nanowire network simulations of thin films showed that the device sheet resistance was dominated by inter-wire contact resistance. For a given resistivity of ZnO nanowires, the thin film electrodes would have the lowest possible sheet resistance if the inter-wire contact resistance was one order of magnitude lower than the single nanowire resistance. Simulations suggest that the conductivity of such thin film devices could be further enhanced by using longer nanowires. Solution processed Gallium doped ZnO nanowires are aligned on substrates using an innovative shear coating technique. Nanowire alignment has shown improvement in ZnO nanowire transparent electrode conductivity. 2D network simulations in conjunction with electrical measurements have revealed different regimes of operation of nanowire thin films and provided a guideline for improving electrical performance of nanowire electrodes. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Thin Film growth and characterization of Ti doped ZnO by RF/DC magnetron sputtering

    KAUST Repository

    Baseer Haider, M.

    2015-01-01

    Thin film Ti doped ZnO (Ti-ZnO) film were grown on sapphire (0001) substrate by RF and DC magnetron sputtering. Films were grown at a substrate temperature of 250 °C with different Ti/Zn concentration. Surface chemical study of the samples was performed by X-ray photoelectron spectroscopy to determine the stoichiometry and Ti/Zn ratio for all samples. Surface morphology of the samples were studied by atomic force microscopy. X-ray diffraction was carried out to determine the crystallinity of the film. No secondary phases of TixOy was observed. We observed a slight increase in the lattice constant with the increase in Ti concentration in ZnO. No ferromagnetic signal was observed for any of the samples. However, some samples showed super-paramagnetic phase. © 2015 Materials Research Society.

  3. Cation vacancies and electrical compensation in Sb-doped thin-film SnO2 and ZnO

    International Nuclear Information System (INIS)

    We present positron annihilation results on Sb-doped SnO2 and ZnO thin films. The vacancy types and the effect of vacancies on the electrical properties of these intrinsically n-type transparent semiconducting oxides are studied. We find that in both materials low and moderate Sb-doping leads to formation of vacancy clusters of variable sizes. However, at high doping levels cation vacancy defects dominate the positron annihilation signal. These defects, when at sufficient concentrations, can efficiently compensate the n-type doping produced by Sb. This is the case in ZnO, but in SnO2 the concentrations appear too low to cause significant compensation. (invited article)

  4. Electronic structure of amorphous InGaO3(ZnO)0.5 thin films

    International Nuclear Information System (INIS)

    The electronic structure of amorphous semiconductor InGaO3(ZnO)0.5 thin films, which were deposited by radio-frequency magnetron sputtering process, was investigated using X-ray photoelectron spectroscopy and O K-edge X-ray absorption spectroscopy. The overall features of the valence and conduction bands were analyzed by comparing with the spectra of Ga2O3, In2O3, and ZnO films. The valence and conduction band edges are mainly composed of O 2p and In 5sp states, respectively. The bandgap of the films determined by spectroscopic ellipsometry was approximately 3.2 eV. Further, it is found that the introduction of oxygen gas during the sputter-deposition does not induce significant variations in the chemical states and band structure.

  5. Identifying the influence of the intrinsic defects in Gd-doped ZnO thin-films

    KAUST Repository

    Flemban, T. H.

    2016-02-08

    Gd-doped ZnO thin films were prepared using pulsed laser deposition at different oxygen pressures and varied Gd concentrations. The effects of oxygen deficiency-related defects on the Gd incorporation, optical and structural properties, were explored by studying the impact of oxygen pressure during deposition and post-growth thermal annealing in vacuum. Rutherford Backscattering Spectrometry revealed that the Gd concentration increases with increasing oxygen pressure for samples grown with the same Gd-doped ZnO target. Unexpectedly, the c-lattice parameter of the samples tends to decrease with increasing Gd concentration, suggesting that Gd-defect complexes play an important role in the structural properties. Using low-temperature photoluminescence(PL), Raman measurements and density functional theory calculations, we identified oxygen vacancies as the dominant intrinsic point defects. PL spectra show a defect band related to oxygen vacancies for samples grown at oxygen deficiency.

  6. Electronic transport in highly conducting Si-doped ZnO thin films prepared by pulsed laser deposition

    International Nuclear Information System (INIS)

    Highly conducting (ρ = 3.9 × 10−4 Ωcm) and transparent (83%) polycrystalline Si-doped ZnO (SiZO) thin films have been deposited onto borosilicate glass substrates by pulsed laser deposition from (ZnO)1−x(SiO2)x (0 ≤ x ≤ 0.05) ceramic targets prepared using a sol-gel technique. Along with their structural, chemical, and optical properties, the electronic transport within these SiZO samples has been investigated as a function of silicon doping level and temperature. Measurements made between 80 and 350 K reveal an almost temperature-independent carrier concentration consistent with degenerate metallic conduction in all of these samples. The temperature-dependent Hall mobility has been modeled by considering the varying contribution of grain boundary and electron-phonon scattering in samples with different nominal silicon concentrations

  7. High Temperature Thermoelectric Properties of ZnO Based Materials

    DEFF Research Database (Denmark)

    Han, Li

    This thesis investigated the high temperature thermoelectric properties of ZnO based materials. The investigation first focused on the doping mechanisms of Al-doped ZnO, and then the influence of spark plasma sintering conditions on the thermoelectric properties of Al, Ga-dually doped ZnO. Follow......This thesis investigated the high temperature thermoelectric properties of ZnO based materials. The investigation first focused on the doping mechanisms of Al-doped ZnO, and then the influence of spark plasma sintering conditions on the thermoelectric properties of Al, Ga-dually doped Zn...... temperatures. Clear correlations between the initial crystallographic phase of the dopants and the thermoelectric properties of the resulting Al-doped ZnO were observed. For Al, Ga-dually doped ZnO, the spark plasma sintering conditions together with the microstructural evolution and thermoelectric properties...... of the samples were investigated in detail. A proposed solid-state-reaction model suggested that a sintering temperature above 1223K would be preferable in order to achieve phase equilibrium in the samples. The sintering mechanism of the ZnO particles and microstructural evolutions at different...

  8. Influence of annealing conditions on the crystallographic structure, chemical composition and luminescence of ZnO thin films

    International Nuclear Information System (INIS)

    ZnO thin films have many applications in semiconductor devices, such as semiconductor lasers, amplifiers, solar cells, chemical and ultraviolet sensors. We produced ZnO thin films on Si (4 0 0) substrates, using e-beam technique and subsequently annealed them under different conditions (i.e., temperature (200–800), time (60 min and 180 min) and environment (air and oxygen flow). The ZnO (0 0 2) preferred orientation which increases in intensity with annealing temperature and annealing time is deduced from X-ray diffraction (XRD) results. Dislocation density was higher for the films annealed in air which may be caused by the impurities (nitrogen and other species in the air) embedded in the film structure. No significant change in the nano-strain of each group of the samples (annealed under different conditions) was observed. The FESEM images showed a granular structure for annealed samples at 200 °C and 800 °C and a mixed structure of nanowires and nanosheets for samples annealed at 350 °C and 500 °C. Two peaks of UV emission and green emission were observed in the photoluminescence (PL) spectra of the produced samples. The UV emission increased with annealing temperature and annealing time showing higher crystal quality while the behavior of the green emission was opposite to that of the UV emission. The ZnO films resulted from annealing in the air showed stronger green emission than those annealed with flow of oxygen indicating higher impurity concentration and oxygen vacancies in the sample.

  9. Effect of Tertiary Amines on Structural, Morphological and Optical Properties of Nanostructured ZnO Thin Film

    Directory of Open Access Journals (Sweden)

    Mohammad Reza Golobostanfard

    2012-03-01

    Full Text Available Nanostructured ZnO thin film has been synthesized via sol-gel method. In this study, effect of stabilizer, as a vital part of sol with different molar ratios of stabilizer to Zn (stabilizer/Zn  0.25, 0.5, 1, 2, on structural, morphological and optoelectronic properties of ZnO thin film has been investigated. Triehtylamine (TeA and triethanolamine (TEA, as two important tertiary amines for synthesize of ZnO, has been used. Spin coating technique performed to deposition of sol on glass substrate and after deposition process, the samples clacined at 500 C. X-ray diffraction method conducted in order to find structural properties of the films. The results showed the formation of hexagonal wurtzite ZnO as well as increasing the unit cell parameters by increasing TeA content. Field emission scanning electron microscopy (FESEM used in order to see morphological changes for different molar ratios of stabilizer to Zn. The images demonstrate grain segregation in TeA samples by increasing TeA molar ratio. Also, in TEA samples, formation of micro holes in TEA/Zn  0.5 and smaller grain size for higher TEA ratios has been observed. UV-Vis spectroscopy was employed to obtain optoelectronic properties and the results have shown dependence of optical band gap to stabilizer’s type and content. Nanostructured ZnO thin film has been synthesized via sol-gel method. In this study, effect of stabilizer, as a vital part of sol with different molar ratios of stabilizer to Zn (stabilizer/Zn  0.25, 0.5, 1, 2, on structural, morphological and optoelectronic properties of ZnO thin film has been investigated. Triehtylamine (TeA and triethanolamine (TEA, as two important tertiary amines for synthesize of ZnO, has been used. Spin coating technique performed to deposition of sol on glass substrate and after deposition process, the samples clacined at 500 C. X-ray diffraction method conducted in order to find structural properties of the films. The

  10. Effect of oxygen partial pressure on the photoluminescence properties of sol–gel synthesized nano-structured ZnO thin films

    International Nuclear Information System (INIS)

    Nanostructured ZnO thin films were prepared by spin coating on glass substrate. The precursor ZnO gel powder was thoroughly characterized by particle size measurement, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy and selected area diffraction pattern analyses. The sol on heating at 450–650 °C resulted in the formation of dried mass with particle size in the range of 30–40 nm. The photoluminescence (PL) peak of ZnO thin film heat treated at 450 °C for different periods appeared at 400 nm. But when the film was heat treated at the same temperature (450 °C) under reducing atmosphere, another PL peak appeared at 443 nm. Heat treatment of the film at 650 °C for 3 h under reducing atmosphere resulted in the appearance of PL peaks at 500 and 555 nm. The PL peaks developed were related to the defect states of zinc oxide lattice developed at different oxygen partial pressures during the heat treatment. - Highlights: • Nano-structured ZnO thin films were prepared by spin coating. • Heat treatment at different conditions generates different defect states in ZnO. • The defect states control photoluminescence of ZnO at 400, 443, 500 and 555 nm

  11. Blue Cathodoluminescence from Highly Er-Doped ZnO Thin Films Induced by the Phonon Bottleneck Effect

    Institute of Scientific and Technical Information of China (English)

    张喜田; 刘益春; 马剑刚; 吕有明; 申德振; 许武; 钟国柱; 范希武

    2003-01-01

    The room-temperature blue cathodoluminescence (CL) from highly Er-doped ZnO thin films has been studied by using different electron beam currents (EBCs). The ZnO:Er thin films used in our experiment were prepared by simultaneous evaporation from two sources. The x-ray diffraction spectra show that the thin films have a strong preferential c-axis (0002) orientation with a hexagonal crystalline structure. The blue emission at 455 nm originating from the intra-4 f shell transition (4F5/2.4I15/2) in Er3+ ions was observed at room temperature. The nonlinear dependence of the CL intensity on the EBC shows a more intense blue emission above the threshold EBC of 0. 6 μA, which is attributed to the phonon bottleneck effect.

  12. Research Update: Atmospheric pressure spatial atomic layer deposition of ZnO thin films: Reactors, doping, and devices

    Energy Technology Data Exchange (ETDEWEB)

    Hoye, Robert L. Z., E-mail: rlzh2@cam.ac.uk, E-mail: jld35@cam.ac.uk; MacManus-Driscoll, Judith L., E-mail: rlzh2@cam.ac.uk, E-mail: jld35@cam.ac.uk [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Muñoz-Rojas, David [LMGP, University Grenoble-Alpes, CNRS, F-3800 Grenoble (France); Nelson, Shelby F. [Kodak Research Laboratories, Eastman Kodak Company, Rochester, New York 14650 (United States); Illiberi, Andrea; Poodt, Paul [Holst Centre/TNO Thin Film Technology, Eindhoven, 5656 AE (Netherlands); Roozeboom, Fred [Holst Centre/TNO Thin Film Technology, Eindhoven, 5656 AE (Netherlands); Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, Eindhoven, 5600 MB (Netherlands)

    2015-04-01

    Atmospheric pressure spatial atomic layer deposition (AP-SALD) has recently emerged as an appealing technique for rapidly producing high quality oxides. Here, we focus on the use of AP-SALD to deposit functional ZnO thin films, particularly on the reactors used, the film properties, and the dopants that have been studied. We highlight how these films are advantageous for the performance of solar cells, organometal halide perovskite light emitting diodes, and thin-film transistors. Future AP-SALD technology will enable the commercial processing of thin films over large areas on a sheet-to-sheet and roll-to-roll basis, with new reactor designs emerging for flexible plastic and paper electronics.

  13. Research Update: Atmospheric pressure spatial atomic layer deposition of ZnO thin films: Reactors, doping, and devices

    International Nuclear Information System (INIS)

    Atmospheric pressure spatial atomic layer deposition (AP-SALD) has recently emerged as an appealing technique for rapidly producing high quality oxides. Here, we focus on the use of AP-SALD to deposit functional ZnO thin films, particularly on the reactors used, the film properties, and the dopants that have been studied. We highlight how these films are advantageous for the performance of solar cells, organometal halide perovskite light emitting diodes, and thin-film transistors. Future AP-SALD technology will enable the commercial processing of thin films over large areas on a sheet-to-sheet and roll-to-roll basis, with new reactor designs emerging for flexible plastic and paper electronics

  14. Oxygen partial pressure dependent electrical conductivity type conversion of phosphorus-doped ZnO thin films

    International Nuclear Information System (INIS)

    In this study, the oxygen partial pressure dependent physical properties of phosphorous-doped ZnO thin films were investigated. All thin films, grown on Al2O3(0 0 0 1) substrates using pulsed laser deposition, exhibited (0 0 2) orientation regardless of the oxygen partial pressure. However, as the oxygen partial pressure increased, the degree of crystallinity and the concentration of oxygen vacancies in the films decreased. All the thin-film samples showed n-type characteristics except for a sample grown at 100 mTorr, which exhibited p-type characteristics. The optical band gap energy also changed with the oxygen partial pressure. The feasible microscopic mechanism of conductivity conversion is explained in terms of the lattice constant, crystallinity, and the relative roles of the substituted phosphorous in the Zn-site and/or oxygen vacancies depending on the oxygen partial pressure. (paper)

  15. Growth of phosphorus doped ZnO thin films by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Vaithianathan, Veeramuthu; Lee, Byung-Teak; Kim, Sang Sub [Photonic and Electronic Thin Film Laboratory, Department of Materials Science and Engineering Chonnam National University, 300 Yongbong-dong, Gwangju 500-757 (Korea)

    2004-09-01

    Undoped and phosphorus doped (1 and 3 mol%) ZnO (P-doped ZnO) films were grown on sapphire substrates by a pulsed laser deposition technique and then the phosphorus doping effect was investigated. Results of X-ray diffraction and scanning electron microscopy revealed that the phosphorus doping did not noticeably affect the microstructure and crystallinity of the undoped ZnO film. In the as-grown state, both of the P-doped ZnO films showed n-type conductivity rather with slightly more electron concentrations than that of the undoped ZnO film. For the 3 mol% P-doped ZnO film a significant decrease in the carrier concentration was observed at particular annealing temperatures ({>=}800 C), still showing n-type conductivity. In contrast, in the case of 1 mol% P-doping, the variation in the carrier concentration was not significant under any annealing temperature. Our results suggest that a careful adjustment both of annealing temperature and of phosphorus doping content is required to control the electrical properties including the carrier concentration, resistivity and mobility in ZnO films. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Transparent Conductive Al-Doped ZnO/Cu Bilayer Films Grown on Polymer Substrates at Room Temperature

    International Nuclear Information System (INIS)

    Al-doped ZnO (AZO)/Cu bi-layer films are deposited by dc magnetron sputtering on polycarbonate substrates at room temperature. The structural, electrical and optical properties of the films are investigated at various sputtering powers of the Cu layer. The AZO/Cu bi-layer film deposited at a moderate sputtering power of 180 W for the Cu layer displayed the highest figure of merit of 3.47 × 10−3Ω−1, with a low sheet resistance of 12.38 Ω/sq, an acceptable visible transmittance of 73%, and a high near-infrared reflectance of about 50%. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  17. Enhancement in conductivity through Ga, Al dual doping of ZnO nanofibers

    Energy Technology Data Exchange (ETDEWEB)

    Park, Minkyu; Han, Seung Min, E-mail: smhan01@kaist.ac.kr

    2015-09-01

    In this study, electrical conductivity of Al doped ZnO nanofiber was enhanced by using Ga co-doping over the maximum conductivity achievable with only Al dopants of 2 at.% in ZnO. Al and Ga have different atomic sizes that results in further doping with Ga up to 1 at.%. Al, Ga co-doped ZnO nanofiber was fabricated by using electrospinning technique and structural analysis was investigated by X-ray diffraction. X-ray analysis indicates a change in lattice parameter(a-axis) of doped ZnO from 3.2497 Å to 3.2483 Å with added 1 at.% Al and from 3.2497 Å to 3.2488 Å with co-doping of 1 at.% Ga on top of the 2 at.% of Al doped ZnO. Therefore, Ga was incorporated into Al doped ZnO nanofiber without significant lattice parameter and grain size reduction to result in the enhanced conductivity up to a maximum value of 9.57 × 10{sup −3} S/cm. - Highlights: • Al, Ga co-doped ZnO nanofiber is synthesized by electrospinning methods. • Al, Ga co-doped nanofiber shows the higher electrical conductivity compared to Al doped ZnO nanofiber. • AGZO nanofiber shows higher conductivity due to its higher crystallinity.

  18. Enhancement in conductivity through Ga, Al dual doping of ZnO nanofibers

    International Nuclear Information System (INIS)

    In this study, electrical conductivity of Al doped ZnO nanofiber was enhanced by using Ga co-doping over the maximum conductivity achievable with only Al dopants of 2 at.% in ZnO. Al and Ga have different atomic sizes that results in further doping with Ga up to 1 at.%. Al, Ga co-doped ZnO nanofiber was fabricated by using electrospinning technique and structural analysis was investigated by X-ray diffraction. X-ray analysis indicates a change in lattice parameter(a-axis) of doped ZnO from 3.2497 Å to 3.2483 Å with added 1 at.% Al and from 3.2497 Å to 3.2488 Å with co-doping of 1 at.% Ga on top of the 2 at.% of Al doped ZnO. Therefore, Ga was incorporated into Al doped ZnO nanofiber without significant lattice parameter and grain size reduction to result in the enhanced conductivity up to a maximum value of 9.57 × 10−3 S/cm. - Highlights: • Al, Ga co-doped ZnO nanofiber is synthesized by electrospinning methods. • Al, Ga co-doped nanofiber shows the higher electrical conductivity compared to Al doped ZnO nanofiber. • AGZO nanofiber shows higher conductivity due to its higher crystallinity

  19. Advanced LPCVD ZnO - Challenges in application for thin film solar cells and modules

    OpenAIRE

    Messerschmidt, Daniel; Aebi, Philipp

    2014-01-01

    Ethanol is used as a precursor during the growth of zinc oxide (ZnO) by low-pressure chemical vapor deposition (LPCVD). By adding ethanol, the surface of the deposited ZnO layer is flattened and its roughness is decreased about sevenfold. The layers become increasingly stressed and their resistivity grows significantly. The present work proposes an explanation for the observed behavior based on the catalytic decomposition of ethanol at the ZnO surface and on the growth of selected crystal plane...

  20. Electrical properties of ZnO thin films grown by MOCVD

    International Nuclear Information System (INIS)

    We report on the electrical characterization of ZnO films grown by MOCVD on glass and sapphire substrates. After correcting our temperature variable Hall measurements by applying the standard two-layer model, which takes into account an interfacial layer, scattering mechanisms in the ZnO films were studied as well as donor activation energies determined. ZnO films grown at different oxygen partial pressures indicated the importance of growth conditions on the defect structure by means of their conductivities and conductivity activation energies

  1. Investigation on the Electrical and Methane Gas-Sensing Properties of ZnO Thin Films Produced by Different Methods

    Science.gov (United States)

    Teimoori, F.; Khojier, K.; Dehnavi, N. Z.

    2016-06-01

    In this work, the influence of deposition method on the structural, electrical, and methane gas-sensing properties of ZnO thin films is investigated. Sol-gel spin coating, direct current (DC) magnetron sputtering, and e-beam evaporation techniques are employed for production of Zn thin films post-annealed at 500°C with a constant flow of oxygen. Detailed morphological, chemical, and structural investigations are carried out on all samples by field emission electron microscopy (FESEM) and x-ray diffraction (XRD) analyses. DC electrical resistivity of the samples was measured using a four-point probe instrument while a Hall effect instrument was used for the Hall effect measurements. The sensing performance was optimized with respect to the deposition method as well as the operating temperature. Detection limit, reproducibility, and stability of all samples produced using different methods are also identified. An optimum operating temperature of 350°C is obtained. The best sensitivity was attributed to the deposited film by the e-beam evaporation method due to its different surface morphology, which provided a larger ratio of surface-to-bulk area, and a lower carrier concentration, which caused higher electrical resistance. All ZnO thin films deposited by different methods also showed good reproducibility and stability.

  2. Spectroscopic ellipsometric study of ZnO and Zn1-xMgxO thin films grown on (0001) sapphire substrate

    International Nuclear Information System (INIS)

    We grew ZnO and Zn1-xMgxO thin films on (0001) sapphire substrates by using metal-organic vapor phase epitaxy and measured the pseudo-dielectric functions using variable-angle spectroscopic ellipsometry. We analyzed the pseudo-dielectric functions by using the multi-layer model. The dielectric functions were fitted by using a Holden model dielectric function. We used anisotropic layer modeling for the ZnO thin film, whereas we adopted the approximation of isotropic layer modeling for the Zn1-xMgxO alloys. We also discuss the Mg composition dependence of the bandgap and the binding energy in Zn1-xMgxO alloys, and consider the valence-band ordering in ZnO thin films.

  3. Negative permittivity of ZnO thin films prepared from aluminum and gallium doped ceramics via pulsed-laser deposition

    DEFF Research Database (Denmark)

    Bodea, M. A.; Sbarcea, G.; Naik, G. V.; Boltasseva, Alexandra; Klar, T. A.; Pedarnig, J. D.

    2013-01-01

    Aluminum and gallium doped zinc oxide thin films with negative dielectric permittivity in the near infrared spectral range are grown by pulsed laser deposition. Composite ceramics comprising ZnO and secondary phase Al2O3 or Ga2O3 are employed as targets for laser ablation. Films deposited on glass...... from dense and small-grained ceramic targets show optical transmission larger than 70 % in the visible and reveal an onset of metallic reflectivity in the near infrared at 1100 nm and a crossover to a negative real part of the permittivity at approximately 1500 nm. In comparison to noble metals, doped...

  4. Enhancement of photo sensor properties of nanocrystalline ZnO thin film by swift heavy ion irradiation

    International Nuclear Information System (INIS)

    Nanocrystalline Zinc Oxide (ZnO) thin film prepared by Low cost Successive Ionic Layer Adsorption and Reaction (SILAR) method. This film was irradiated by 120 MeV Ni7+ ions with the fluence of 5x1012ions/cm2. The X-ray diffraction study was shows polycrystalline nature with wurtzite structure. The optical properties as absorbance were determined using UV-Spectrophotometer and band gap was also calculated. The Photo Sensor nature was calculated by I-V characteristics with different sources of light 40W, 60W and 100W

  5. Photoluminescence studies of ZnO thin films on R-plane sapphire substrates grown by sol-gel method

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min Su [Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Gimhae, Gyungnam 621-749 (Korea, Republic of); Nam, Giwoong; Kim, Soaram [Department of Nano Engineering, Inje University, Gimhae, Gyungnam 621-749 (Korea, Republic of); Kim, Do Yeob [Holcombe Department of Electrical and Computer Engineering, Center for Optical Materials Science and Engineering Technologies, Clemson University, Clemson, SC 29634 (United States); Lee, Dong-Yul [LED R and D team, Samsung Electronics Co. Ltd., Yongin 446-711 (Korea, Republic of); Kim, Jin Soo [Research Center of Advanced Materials Development (RCAMD), Division of Advanced Materials Engineering, Chonbuk National University, Jeonju, Chonbuk 561-756 (Korea, Republic of); Kim, Sung-O [Holcombe Department of Electrical and Computer Engineering, Center for Optical Materials Science and Engineering Technologies, Clemson University, Clemson, SC 29634 (United States); Kim, Jong Su [Department of Physics, Yeungnam University, Gyeongsan, Gyeongsangbuk-do 712-749 (Korea, Republic of); Son, Jeong-Sik [Department of Visual Optics, Kyungwoon University, Gumi, Gyeongsangbuk-do 730-850 (Korea, Republic of); Leem, Jae-Young, E-mail: jyleem@inje.ac.kr [Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Gimhae, Gyungnam 621-749 (Korea, Republic of)

    2012-10-15

    Zinc oxide (ZnO) thin films on R-plane sapphire substrates were grown by the sol-gel spin-coating method. The optical properties of the ZnO thin films were investigated using photoluminescence. In the UV range, the asymmetric near-band-edge emission was observed at 300 K, which consisted of two emissions at 3.338 and 3.279 eV. Eight peaks at 3.418, 3.402, 3.360, 3.288, 3.216, 3.145, 3.074, and 3.004 eV, which respectively correspond to the free exciton (FX), bound exciton, transverse optical (TO) phonon replica of FX recombination, and first-order longitudinal optical phonon replica of FX and the TO (1LO+TO), 2LO+TO, 3LO+TO, 4LO+TO, and 5LO+TO, were obtained at 12 K. From the temperature-dependent PL, it was found that the emission peaks at 3.338 and 3.279 eV corresponded to the FX and TO, respectively. The activation energy of the FX and TO emission peaks was found to be about 39.3 and 28.9 meV, respectively. The values of the fitting parameters of Varshni's empirical equation were {alpha}=4 Multiplication-Sign 10{sup -3} eV/K and {beta}=4.9 Multiplication-Sign 10{sup 3} K, and the S factor of the ZnO thin films was 0.658. With increasing temperature, the exciton radiative lifetime of the FX and TO emissions increased. The temperature-dependent variation of the exciton radiative lifetime for the TO emission was slightly higher than that for the FX emission. - Highlights: Black-Right-Pointing-Pointer ZnO thin films on R-plane sapphire substrates were grown by sol-gel method. Black-Right-Pointing-Pointer Two emission peaks at 3.338 and 3.279 eV were observed at 300 K Black-Right-Pointing-Pointer Activation energies of the two peaks were 39.3 and 28.9 meV,respectively. Black-Right-Pointing-Pointer Exciton radiative lifetime of the two peaks increased with increasing temperature.

  6. A Study on the Structural Change of Al--N Co-Doped ZnO Thin Films

    International Nuclear Information System (INIS)

    The co-doped ZnO thin film were deposited by DC magnetron sputtering on silicon (111) followed by annealing treatment at 200 deg. C to 600 deg. C for 1 hour in nitrogen and oxygen gas mixture. Structural investigation was carried out by atomic force microscopy (AFM), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and X--ray diffraction (XRD). Film roughness (r.m.s) and grain shape were found to be correlated with the annealing temperatures. SEM result has shown that its surface characteristics are strongly influenced by annealing temperatures.

  7. X-ray absorption spectroscopy of Mn doped ZnO thin films prepared by rf sputtering technique

    International Nuclear Information System (INIS)

    A set of r.f. sputter deposited ZnO thin films prepared with different Mn doping concentrations have been characterised by Extended X-ray Absorption Fine Structure (EXAFS) and X-ray Absorption Near Edge Spectroscopy (XANES) measurements at Zn, Mn and O K edges and at Mn L2,3 edges apart from long range structural characterisation by Grazing Incident X-ray Diffraction (GIXRD) technique. Magnetic measurements show room temperature ferromagnetism in samples with lower Mn doping which is however, gets destroyed at higher Mn doping concentration. The results of the magnetic measurements have been explained using the local structure information obtained from EXAFS and XANES measurements

  8. Thickness dependence of the structural and electrical properties of ZnO thermal-evaporated thin films

    Indian Academy of Sciences (India)

    A Ghaderi; S M Elahi; S Solaymani; M Naseri; M Ahmadirad; S Bahrami; A E Khalili

    2011-12-01

    ZnO thin films of different thicknesses were prepared by thermal evaporation on glass substrates at room temperature. Deposition process was carried out in a vapour pressure of about 5.54 × 10-5 mbar. The substrate–target distance was kept constant during the process. By XRD and AFM techniques the microstructural characteristics and their changes with variation in thickness were studied. Electrical resistivity and conductivity of samples vs. temperature were investigated by four-probe method. It was shown that an increase in thickness causes a decrease in activation energy.

  9. Enhancement of photo sensor properties of nanocrystalline ZnO thin film by swift heavy ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Mahajan, S. V.; Upadhye, D. S.; Bagul, S. B. [Department of Nanotechnology, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad-431004 (India); Shaikh, S. U.; Birajadar, R. B.; Siddiqui, F. Y.; Huse, N. P. [Thin film and Nanotechnology Laboratory, Department of Physics, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad-431004 (India); Sharma, R. B., E-mail: ramphalsharma@yahoo.com, E-mail: rps.phy@gmail.com [Thin film and Nanotechnology Laboratory, Department of Physics, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad-431004 (India); Department of Nanotechnology, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad-431004 (India)

    2015-06-24

    Nanocrystalline Zinc Oxide (ZnO) thin film prepared by Low cost Successive Ionic Layer Adsorption and Reaction (SILAR) method. This film was irradiated by 120 MeV Ni{sup 7+} ions with the fluence of 5x10{sup 12}ions/cm{sup 2}. The X-ray diffraction study was shows polycrystalline nature with wurtzite structure. The optical properties as absorbance were determined using UV-Spectrophotometer and band gap was also calculated. The Photo Sensor nature was calculated by I-V characteristics with different sources of light 40W, 60W and 100W.

  10. ZnO nanorod arrays for highly efficient thin film a-Si and micromorph solar cells

    Czech Academy of Sciences Publication Activity Database

    Neykova, Neda; Hruška, Karel; Remeš, Zdeněk; Vaněček, Milan

    Roma: University of Roma Tor Vergata, 2012 - (DE Crescenzi, M.). s. 75-75 [International Conference on NANO-structures self-assembly - NANOSEA 2012 /4./. 25.06.2012-29.06.2012, S. Margherita di Pula - Sardinie] R&D Projects: GA ČR(CZ) GAP108/11/0937 EU Projects: European Commission(XE) 214134 - N2P Institutional research plan: CEZ:AV0Z10100521 Keywords : ZnO nanocolumns * thin film solar cells * EBL Subject RIV: BM - Solid Matter Physics ; Magnetism

  11. The preparation of ZnO based gas-sensing thin films by ink-jet printing method

    International Nuclear Information System (INIS)

    An ink-jet printing technique was applied to prepare ZnO based gas-sensing thin films. ZnO inks with appropriate viscosity and surface tension were prepared by sol-gel techniques, and printed onto substrates using a commercial printer. After the drying and heating treatment processes, continuous ZnO films were formed and studied by scanning electron microscopy, X-ray diffraction and by a home-made gas sensitivity measuring system. It was found that the morphology and electrical properties of the films changed significantly with the thickness of the films, which can be adjusted simply by printing on the film with increasing frequency. Highest resistance and sensitivity to acetone vapor were obtained when the film was prepared by printing only once on it. Different dopants with certain concentrations could be added into the films by printing with different dopant inks and printing frequency. All Pd, Ag, and ZrO2 dopants increased both the resistivity and the sensitivity of the films (180 ppm acetone). This work showed that the ink-jet printing technique was a convenient and low cost method to prepare films with controlled film thickness and dopant concentration

  12. Broad-band three dimensional nanocave ZnO thin film photodetectors enhanced by Au surface plasmon resonance.

    Science.gov (United States)

    Sun, Mengwei; Xu, Zhen; Yin, Min; Lin, Qingfeng; Lu, Linfeng; Xue, Xinzhong; Zhu, Xufei; Cui, Yanxia; Fan, Zhiyong; Ding, Yiling; Tian, Li; Wang, Hui; Chen, Xiaoyuan; Li, Dongdong

    2016-04-28

    ZnO semiconductor films with periodic 3D nanocave patterns were fabricated by the thermal nanoimprinting technology, which is promising for photodetectors with enhanced light harvesting capability. The Au nanoparticles were further introduced into the ZnO films, which boosts the UV response of ZnO films and extends the photodetection to visible regions. The best UV photoresponse was detected on the 3D nanocave ZnO-Au hybrid films, attributing to the light trapping mechanism of 3D periodic structures and the driving force of the Schottky barrier at the ZnO/Au interface, while the high visible photoresponse of ZnO-Au hybrid films mainly results from the hot electron generation and injection process over the Schottky junctions mediated by Au surface plasmon resonances. The work provides a cost-effective pathway to develop large-scale periodic 3D nanopatterned thin film photodetectors and is promising for the future deployment of high performance optoelectronic devices. PMID:27073045

  13. Broad-band three dimensional nanocave ZnO thin film photodetectors enhanced by Au surface plasmon resonance

    Science.gov (United States)

    Sun, Mengwei; Xu, Zhen; Yin, Min; Lin, Qingfeng; Lu, Linfeng; Xue, Xinzhong; Zhu, Xufei; Cui, Yanxia; Fan, Zhiyong; Ding, Yiling; Tian, Li; Wang, Hui; Chen, Xiaoyuan; Li, Dongdong

    2016-04-01

    ZnO semiconductor films with periodic 3D nanocave patterns were fabricated by the thermal nanoimprinting technology, which is promising for photodetectors with enhanced light harvesting capability. The Au nanoparticles were further introduced into the ZnO films, which boosts the UV response of ZnO films and extends the photodetection to visible regions. The best UV photoresponse was detected on the 3D nanocave ZnO-Au hybrid films, attributing to the light trapping mechanism of 3D periodic structures and the driving force of the Schottky barrier at the ZnO/Au interface, while the high visible photoresponse of ZnO-Au hybrid films mainly results from the hot electron generation and injection process over the Schottky junctions mediated by Au surface plasmon resonances. The work provides a cost-effective pathway to develop large-scale periodic 3D nanopatterned thin film photodetectors and is promising for the future deployment of high performance optoelectronic devices.ZnO semiconductor films with periodic 3D nanocave patterns were fabricated by the thermal nanoimprinting technology, which is promising for photodetectors with enhanced light harvesting capability. The Au nanoparticles were further introduced into the ZnO films, which boosts the UV response of ZnO films and extends the photodetection to visible regions. The best UV photoresponse was detected on the 3D nanocave ZnO-Au hybrid films, attributing to the light trapping mechanism of 3D periodic structures and the driving force of the Schottky barrier at the ZnO/Au interface, while the high visible photoresponse of ZnO-Au hybrid films mainly results from the hot electron generation and injection process over the Schottky junctions mediated by Au surface plasmon resonances. The work provides a cost-effective pathway to develop large-scale periodic 3D nanopatterned thin film photodetectors and is promising for the future deployment of high performance optoelectronic devices. Electronic supplementary information

  14. Effects of Al and Mn Dopant on Structural and Optical Properties of ZnO Thin Film Prepared by Sol-Gel Route

    Directory of Open Access Journals (Sweden)

    Sumetha SUWANBOON

    2007-01-01

    Full Text Available Undoped, 10 wt% Al and 10 wt% Mn doped ZnO thin films were deposited on a glass substrate by sol-gel dip coating. Al ions played an important role in improvement of the c-axis orientation, while Mn ions inhibited the growth along c-axis. The average grain size decreased when doping ZnO with Al and Mn. The smallest average grain size was 25 nm, obtained with 10 wt% Mn doping. The band gap values of prepared thin films varied in the range of 3.24 - 3.96 eV.

  15. Effects of growth temperature on the structural and the optical properties of ZnO thin films on porous silicon grown by using plasma-assisted molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min Su; Kim, Soa Ram; Yim, Kwang Gug; Leem, Jae Young; Nam, Gi Woong [Inje University, Gimhae (Korea, Republic of); Kim, Do Yeob [Clemson University, Clemson, South Carolina (United States); Lee, Dong Yul [Samsung Electronics Co. Ltd., Yongin (Korea, Republic of); Kim, Jin Soo [Chonbuk National University, Jeonju (Korea, Republic of); Kim, Jong Su [Yeungnam University, Gyeongsan (Korea, Republic of); Son, Jeong Sik [Kyungwoon University, Gumi (Korea, Republic of)

    2012-05-15

    Zinc oxide (ZnO) thin films were grown on Si and porous silicon (PS) at different growth temperatures in the range from 150 to 550 .deg. C by using plasma-assisted molecular beam epitaxy (PA-MBE). The effects of PS and growth temperature on the structural and the optical properties of the ZnO thin films were investigated by using atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL). A higher intensity and a narrower full width at half maximum (FWHM) of the ZnO (002) diffraction peak were observed from the ZnO thin films grown on PS, indicating improved crystal quality. For the ZnO thin films grown on Si, the optical properties were gradually enhanced as the growth temperature was increased. However, the structural and the optical properties of the ZnO thin films grown on PS exhibited the largest improvement at a growth temperature of 350 .deg. C. The structural and the optical properties of the ZnO thin films, compared with the ZnO thin films grown on Si, were improved by introducing PS, and the optimum growth temperature was decreased.

  16. Control of the threshold voltage in ZnO nanobelt field-effect transistors by using MoO x thin film

    Science.gov (United States)

    Qian, Haolei; Fang, Yanjun; Gu, Lin; Lu, Ren; Zhao, Ming; Wang, Wei; Wang, Yewu; Sha, Jian

    2016-07-01

    We report on the feasible control of the threshold voltage (V th) in ultra-thin ZnO nanobelt FETs by using substoichiometric molybdenum trioxide (MoO x , x electrodes instead of the widely used Ti/Au. ZnO nanobelt FETs using Ti/Au as the electrodes usually exhibit a negative threshold voltage, indicating n-channel depletion mode behavior, whereas ZnO FETs with MoO x /Au electrodes instead of Ti/Au show a positive shift of threshold voltage, exhibiting an n-channel type enhancement mode, which can be explained by a high Schottky barrier created at the interface of MoO x and the ZnO channel. In contrast, the decoration on the surface of ZnO channel by MoO x significantly increases the zero-bias conductivity and electron carrier concentration, and then negatively shifts the threshold voltage. We propose that MoO x thin film may play a passivation effect role, much more so than the doping effect role, due to the large amount of adsorbed species on as-grown ZnO nanobelts, especially oxygen species.

  17. Microtron Irradiation Induced Tuning of Band Gap and Photoresponse of Al-ZnO Thin Films Synthesized by mSILAR

    Science.gov (United States)

    Thomas, Deepu; Augustine, Simon; Sadasivuni, Kishor Kumar; Ponnamma, Deepalekshmi; Alhaddad, Ahmad Yaser; Cabibihan, John-John; Vijayalakshmi, K. A.

    2016-06-01

    Al-doped polycrystalline nano ZnO (Al-ZnO) thin films with different doping concentrations were successfully prepared by the microwave-assisted successive ionic layer adsorption and reaction (mSILAR) technique. The structural analysis along with the orientation of the prepared films was examined by powder x-ray diffraction (PXRD) patterns. The deposited film is polycrystalline and the (002) orientation enhanced upon doping. Additional investigations were carried out to study the effect of electron beam irradiation (e--irradiation) on the band gap and photoconductivity of both irradiated and unirradiated samples. Both the Al doping and e--irradiation led to the enhancement of the photoconductivity of prepared materials. This property enables us to tune the properties of materials for various applications by controlling dopant concentrations and e--irradiation. The dependence of photocurrent on e--irradiation of Al-ZnO thin films was not reported previously. Therefore, Al-doped polycrystalline nano-ZnO thin film is a promising material for band gap engineering and for the development of solar cells.

  18. Rectifying Behavior of Aligned ZnO Nano rods on Mg0.3Zn0.7O Thin Film Template

    International Nuclear Information System (INIS)

    Rectifying behavior more than 3 orders of aligned zinc oxide (ZnO) nano rods grown on Mg0.3Zn0.7O thin film template using chemical bath deposition method was observed, giving a barrier height of 0.75 eV, and the ideality factor achieved was almost 6, which was analyzed using thermionic emission theory. Field emission scanning electron microscope (FESEM) images revealed that the grown ZnO was in hexagonal shape, uniformly distributed and in vertically aligned form. The crystallinity of the sample being studied using X-ray diffraction (XRD), where the highest peak was found at (002) phase, confirming that high crystallinity of ZnO was attained. The effect of metal/semiconductor junction between metal and aligned ZnO nano rods was discussed in further details. (author)

  19. All-sputtered 14% CdS/CdTe thin-film solar cell with ZnO:Al transparent conducting oxide

    International Nuclear Information System (INIS)

    Radio-frequency (rf)-sputtered Al-doped ZnO was used as the transparent front contact in the fabrication of high efficiency superstrate configuration CdS/CdTe thin-film solar cells. These cells had CdS and CdTe layers also deposited by rf sputtering at 250 deg. C with the highest processing temperature of 387 deg. C reached during a post-deposition treatment. The devices were tested at National Renewable Energy Laboratory and yielded an efficiency of 14.0%, which is excellent for a CdTe cell using ZnO and also for any sputtered CdTe solar cell. The low-temperature deposition process using sputtering for all semiconductor layers facilitates the use of ZnO and conveys significant advantages for the fabrication of more complex multiple layers needed for the fabrication of tandem polycrystalline solar cells and for cells on polymer materials

  20. Effects of rapid thermal annealing on the structural and local atomic properties of ZnO: Ge nanocomposite thin films

    International Nuclear Information System (INIS)

    We have investigated the structural and local atomic properties of Ge nanocrystals (Ge-ncs) embedded ZnO (ZnO: Ge) thin films. The films were deposited by sequential sputtering of ZnO and Ge thin film layers on z-cut quartz substrates followed by an ex-situ rapid thermal annealing (RTA) at 600 °C for 30, 60, and 90 s under forming gas atmosphere. Effects of RTA time on the evolution of Ge-ncs were investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), hard x-ray photoelectron spectroscopy (HAXPES), and extended x-ray absorption fine structure (EXAFS). XRD patterns have clearly shown that fcc diamond phase Ge-ncs of sizes ranging between 18 and 27 nm are formed upon RTA and no Ge-oxide peak has been detected. However, cross-section SEM images have clearly revealed that after RTA process, Ge layers form varying size nanoclusters composed of Ge-ncs regions. EXAFS performed at the Ge K-edge to probe the local atomic structure of the Ge-ncs has revealed that as prepared ZnO:Ge possesses Ge-oxide but subsequent RTA leads to crystalline Ge structure without the oxide layer. In order to study the occupied electronic structure, HAXPES has been utilized. The peak separation between the Zn 2p and Ge 3d shows no significant change due to RTA. This implies little change in the valence band offset due to RTA

  1. The Theoretical Investigation and Analysis of High-Performance ZnO Double-Gate Double-Layer Insulator Thin-Film Transistors

    Institute of Scientific and Technical Information of China (English)

    GAO Hai-Xia; HU Rong; YANG Yin-Tang

    2012-01-01

    A novel structure of a ZnO thin-film transistor with a double-gate and double-layer insulator is proposed to improve device performance.Compared with the conventional ZnO thin-film transistor structure,the novel thinfilm transistor has a higher on-state current,steeper sub-threshold characteristics and a lower threshold voltage,owing to the double-gate and high-k dielectric.Based on two-dimensional simulation,the potential channel distribution and the reasons for the improvement in performance are investigated.%A novei structure of a ZnO thin-film transistor with a double-gate and double-layer insulator is proposed to improve device performance. Compared with the conventional ZnO thin-Rim transistor structure, the novel thin-Sim transistor has a higher on-state current, steeper sub-threshold characteristics and a lower threshold voltage, owing to the double-gate and high-k dielectric. Based on two-dimensional simulation, the potential channel distribution and the reasons for the improvement in performance are investigated.

  2. Effect of 8 MeV Si ions irradiation and thermal annealing in ZnO thin films

    Science.gov (United States)

    Hernández-Socorro, D. R.; Montiel-González, Z.; Rodil-Posada, S. E.; Flores-Morales, L.; Cruz-Manjarrez, H.; Hernández-Alcántara, J. M.; Rodríguez-Fernández, L.

    2012-09-01

    ZnO thin films deposited by RF magnetron sputtering on silicon (100) wafers were irradiated by 8 MeV Si ions and thermal annealed in order to study optical properties. The presence of defects inside thin films as well as their implications was discussed by Photoluminescence and Spectroscopic Ellipsometry. Photoluminescence confirmed presence of energy states in forbidden band-gap associates with ultraviolet emission and Zni, Oi and OZn defects according to the treatment received. Spectroscopic Ellipsometry using the Tauc-Lorentz model plus a Lorentz oscillator was found to be the best model to describe the properties of irradiated samples that did not receive a second thermal annealing treatment. Through this model, it was possible to obtain optical band-gap in the range of 3.1-3.3 eV and excellent approximation of position in energy of the oscillator.

  3. Determination and analysis of the dispersive optical constants of the non-crystalline ZnO thin film

    International Nuclear Information System (INIS)

    In this work, non-crystalline ZnO thin film has been successfully deposited by the spray pyrolysis method onto glass substrate. The structure of the film was analyzed by X-ray diffraction and the results obtained showed that the structure of the film is non-crystalline. The Urbach tail parameter, the optical band gap, and the optical constants such as refractive index, extinction coefficient and dielectric constants of the deposited non-crystalline thin film have been investigated by optical characterization method. The dispersion curves of the refractive index of the non-crystalline film obey single-oscillator model. The dispersion parameters such as Eo (single-oscillator energy) and Ed (dispersive energy) of the non-crystalline film was determined. (Author)

  4. Antibacterial and barrier properties of oriented polymer films with ZnO thin films applied with atomic layer deposition at low temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Vähä-Nissi, Mika, E-mail: mika.vaha-nissi@vtt.fi [VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044, VTT (Finland); Pitkänen, Marja; Salo, Erkki; Kenttä, Eija [VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044, VTT (Finland); Tanskanen, Anne, E-mail: Anne.Tanskanen@aalto.fi [Aalto University, School of Chemical Technology, Department of Chemistry, Laboratory of Inorganic Chemistry, P.O. Box 16100, FI-00076 Aalto (Finland); Sajavaara, Timo, E-mail: timo.sajavaara@jyu.fi [University of Jyväskylä, Department of Physics, P.O. Box 35, FI-40014 Jyväskylä (Finland); Putkonen, Matti; Sievänen, Jenni; Sneck, Asko; Rättö, Marjaana [VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044, VTT (Finland); Karppinen, Maarit, E-mail: Maarit.Karppinen@aalto.fi [Aalto University, School of Chemical Technology, Department of Chemistry, Laboratory of Inorganic Chemistry, P.O. Box 16100, FI-00076 Aalto (Finland); Harlin, Ali [VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044, VTT (Finland)

    2014-07-01

    Concerns on food safety, and need for high quality and extended shelf-life of packaged foods have promoted the development of antibacterial barrier packaging materials. Few articles have been available dealing with the barrier or antimicrobial properties of zinc oxide thin films deposited at low temperature with atomic layer deposition (ALD) onto commercial polymer films typically used for packaging purposes. The purpose of this paper was to study the properties of ZnO thin films compared to those of aluminum oxide. It was also possible to deposit ZnO thin films onto oriented polylactic acid and polypropylene films at relatively low temperatures using ozone instead of water as an oxidizing precursor for diethylzinc. Replacing water with ozone changed both the structure and the chemical composition of films deposited on silicon wafers. ZnO films deposited with ozone contained large grains covered and separated probably by a more amorphous and uniform layer. These thin films were also assumed to contain zinc salts of carboxylic acids. The barrier properties of a 25 nm ZnO thin film deposited with ozone at 100 °C were quite close to those obtained earlier with ALD Al{sub 2}O{sub 3} of similar apparent thickness on similar polymer films. ZnO thin films deposited at low temperature indicated migration of antibacterial agent, while direct contact between ZnO and Al{sub 2}O{sub 3} thin films and bacteria promoted antibacterial activity. - Highlights: • Thin films were grown from diethylzinc also with ozone instead of water at 70 and 100 °C. • ZnO films deposited with diethylzinc and ozone had different structures and chemistries. • Best barrier properties obtained with zinc oxide films close to those obtained with Al{sub 2}O{sub 3} • Ozone as oxygen source provided better barrier properties at 100 °C than water. • Both aluminum and zinc oxide thin films showed antimicrobial activity against E. coli.

  5. Post-annealing effect on the room-temperature ferromagnetism in Cu-doped ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Yu-Min, E-mail: ymhu@nuk.edu.tw; Kuang, Chein-Hsiun; Han, Tai-Chun; Yu, Chin-Chung [Department of Applied Physics, National University of Kaohsiung, Kaohsiung 811, Taiwan (China); Li, Sih-Sian [Institute of Electro-Optical Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan (China)

    2015-05-07

    In this work, we investigated the structural and magnetic properties of both as-deposited and post-annealed Cu-doped ZnO thin films for better understanding the possible mechanisms of room-temperature ferromagnetism (RT-FM) in ZnO-based diluted magnetic oxides. All of the films have a c-axis-oriented wurtzite structure and display RT-FM. X-ray photoelectron spectroscopy results showed that the incorporated Cu ions in as-deposited films are in 1+ valence state merely, while an additional 2+ valence state occurs in post-annealed films. The presence of Cu{sup 2+} state in post-annealed film accompanies a higher magnetization value than that of as-deposited film and, in particular, the magnetization curves at 10 K and 300 K of the post-annealed film separate distinctly. Since Cu{sup 1+} ion has a filled 3d band, the RT-FM in as-deposited Cu-doped ZnO thin films may stem solely from intrinsic defects, while that in post-annealed films is enhanced due to the presence of CuO crystallites.

  6. ZnO thin film transistors and electronic connections for adjustable x-ray mirrors: SMART-X telescope

    Science.gov (United States)

    Johnson-Wilke, R. L.; Wilke, R. H. T.; Wallace, M.; Ramirez, J. I.; Prieskorn, Z.; Nikoleyczik, J.; Cotroneo, V.; Allured, R.; Schwartz, D. A.; McMuldroch, S.; Reid, P. B.; Burrows, D. N.; Jackson, T. N.; Trolier-McKinstry, S.

    2014-09-01

    The proposed SMART-X telescope consists of a pixelated array of a piezoelectric lead zirconate titanate (PZT) thin film deposited on flexible glass substrates. These cells or pixels are used to actively control the overall shape of the mirror surface. It is anticipated that the telescope will consist of 8,000 mirror panels with 400-800 cells on each panel. This creates an enormous number (6.4 million) of traces and contacts needed to address the PZT. In order to simplify the design, a row/column addressing scheme using ZnO thin film transistors (TFTs) is proposed. In addition, connection of the gate and drain lines on the mirror segment to an external supply via a flexible cable was investigated through use of an anisotropic conductive film (ACF). This paper outlines the design of the ZnO TFTs, use of ACF for bonding, and describes a specially designed electronics box with associated software to address the desired cells.

  7. Growth of ferroelectric Li-doped ZnO thin films for metal-ferroelectric-semiconductor FET

    International Nuclear Information System (INIS)

    A metal-ferroelectric-semiconductor structure has been developed by depositing Li-doped ZnO thin films (Zn1-xLixO, x = 0.25) on p-type Si substrates by the pulsed laser ablation technique. (002) preferential oriented films were deposited at a low growth temperature of 500 0C and 100 mTorr oxygen partial pressure. The dielectric response of the films has been studied over a temperature range 250-373 K. A dielectric anomaly was observed at 360 K. The capacitance-voltage characteristics of Ag/Zn0.75Li0.25O/Si exhibited clockwise hysteresis loops with a memory window of 2 V. The films deposited at 100 mTorr pressure show a stable current density and a saturated polarization hysteresis loop with a remanent polarization of 0.09 μC cm-2 and coercive field of 25 kV cm-1. Leakage current measurements were done at elevated temperatures to provide evidence of the conduction mechanism present in these films. Ohmic behaviour was observed at low voltage, while higher voltages induced a bulk space charge. The optical properties of Zn0.75Li0.25O thin films were studied in the wavelength range 300-900 nm. The appearance of ferroelectric nature in Li-doped ZnO films adds an additional dimension to its applications

  8. Area-Selective ZnO Thin Film Deposition on Variable Microgap Electrodes and Their Impact on UV Sensing

    Directory of Open Access Journals (Sweden)

    Q. Humayun

    2013-01-01

    Full Text Available ZnO thin films were deposited on patterned gold electrodes using the sol-gel spin coating technique. Conventional photolithography process was used to obtain the variable microgaps of 30 and 43 μm in butterfly topology by using zero-gap chrome mask. The structural, morphological, and electrical properties of the deposited thin films were characterized by X-ray diffraction (XRD, scanning electron microscope (SEM, and Keithley SourceMeter, respectively. The current-voltage (I-V characterization was performed to investigate the effect of UV light on the fabricated devices. The ZnO fabricated sensors showed a photo to dark current (Iph/Id ratios of 6.26 for 30 μm and 5.28 for 43 μm gap electrodes spacing, respectively. Dynamic responses of both fabricated sensors were observed till 1V with good reproducibility. At the applied voltage of 1 V, the response time was observed to be 4.817 s and 3.704 s while the recovery time was observed to be 0.3738 s and 0.2891 s for 30 and 43 μm gaps, respectively. The signal detection at low operating voltages suggested that the fabricated sensors could be used for miniaturized devices with low power consumption.

  9. Reliable and Damage-Free Estimation of Resistivity of ZnO Thin Films for Photovoltaic Applications Using Photoluminescence Technique

    Directory of Open Access Journals (Sweden)

    N. Poornima

    2013-01-01

    Full Text Available This work projects photoluminescence (PL as an alternative technique to estimate the order of resistivity of zinc oxide (ZnO thin films. ZnO thin films, deposited using chemical spray pyrolysis (CSP by varying the deposition parameters like solvent, spray rate, pH of precursor, and so forth, have been used for this study. Variation in the deposition conditions has tremendous impact on the luminescence properties as well as resistivity. Two emissions could be recorded for all samples—the near band edge emission (NBE at 380 nm and the deep level emission (DLE at ~500 nm which are competing in nature. It is observed that the ratio of intensities of DLE to NBE (/ can be reduced by controlling oxygen incorporation in the sample. - measurements indicate that restricting oxygen incorporation reduces resistivity considerably. Variation of / and resistivity for samples prepared under different deposition conditions is similar in nature. / was always less than resistivity by an order for all samples. Thus from PL measurements alone, the order of resistivity of the samples can be estimated.

  10. Resistive switching: An investigation of the bipolar–unipolar transition in Co-doped ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Daniel A.A., E-mail: danielandrade.ufs@gmail.com [Department of Physics, Federal University of Sergipe, São Cristóvão 49100-000 (Brazil); Department of Physics, University at Buffalo, The State University of New York, Buffalo, NY 14260 (United States); Zeng, Hao [Department of Physics, University at Buffalo, The State University of New York, Buffalo, NY 14260 (United States); Macêdo, Marcelo A. [Department of Physics, Federal University of Sergipe, São Cristóvão 49100-000 (Brazil)

    2015-06-15

    Highlights: • A purely bipolar behavior on a Co-doped ZnO thin film has been demonstrated. • We have shown what can happen if a unipolar test is performed in a purely bipolar device. • An explanation for how a sample can show a purely bipolar switching behavior was suggested. • An important open issue about resistive switching effect was put in debate. - Abstract: In order to investigate the resistive switching effect we built devices in a planar structure in which two Al contacts were deposited on the top of the film and separated by a small gap using a shadow mask. Therefore, two samples of 10% Co-doped ZnO thin films were sputtered on glass substrate. High resolution X-ray diffraction (HRXRD) revealed a highly c-axis oriented crystalline structure, without secondary phase. The high resolution scanning electron microscopy (HRSEM) showed a flat surface with good coverage and thickness about 300 nm. A Keithley 2425 semiconductor characterization system was used to perform the resistive switching tests in the bipolar and unipolar modes. Considering only the effect of compliance current (CC), the devices showed a purely bipolar behavior since an increase in CC did not induce a transition to unipolar behavior.

  11. Correlation between crystallite size–optical gap energy and precursor molarities of ZnO thin films

    International Nuclear Information System (INIS)

    We investigated the structural and optical properties of ZnO thin films as an n-type semiconductor. The films were deposited at different precursor molarities using an ultrasonic spray method. In this paper we focused our attention on a new approach describing a correlation between the crystallite size and optical gap energy with the precursor molarity of ZnO thin films. The results show that the X-ray diffraction (XRD) spectra revealed a preferred orientation of the crystallites along the c-axis. The maximum value of the crystallite size of the films is 63.99 nm obtained at 0.1 M. The films deposited with 0.1 M show lower absorption within the visible wavelength region. The optical gap energy increased from 3.08 to 3.37 eV with increasing precursor molarity of 0.05 to 0.1 M. The correlation between the structural and optical properties with the precursor molarity suggests that the crystallite size of the films is predominantly influenced by the band gap energy and the precursor molarity. The measurement of the crystallite size by the model proposed is equal to the experimental data. The minimum error value was estimated by Eq. (4) in the higher crystallinity. (semiconductor physics)

  12. Effect of Nd{sup 3+} incorporation on the microstructure and chemical structure of RF sputtered ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Gottardi, Gloria, E-mail: ggottard@fbk.eu [Fondazione Bruno Kessler, Center for Materials and Microsystems, Via Sommarive 18, 38123 Trento (Italy); Pandiyan, Rajesh [Fondazione Bruno Kessler, Center for Materials and Microsystems, Via Sommarive 18, 38123 Trento (Italy); University of Trento, Physics Department, Via Sommarive 14, 38123 Trento (Italy); LGPPTS, ENSCP, Université Pierre et Marie Curie, 11 rue Pierre et Marie Curie, 75005 Paris (France); Micheli, Victor; Pepponi, Giancarlo; Gennaro, Salvatore; Bartali, Ruben; Laidani, Nadhira [Fondazione Bruno Kessler, Center for Materials and Microsystems, Via Sommarive 18, 38123 Trento (Italy)

    2013-05-15

    Highlights: ► Effects of Nd incorporation on ZnO thin films chemical and structural properties. ► Very low Nd concentrations were quantified by combining XRF and AES data. ► At low Nd concentration, Nd ions were successfully incorporated in the ZnO lattice. ► Structural changes turns up with increasing Nd doping level. ► At high Nd concentration, precipitation of a Nd{sub 2}O{sub 3} separate phase occurs. -- Abstract: The present work aims at investigating the effects that different levels of Nd atoms incorporation can have on the microstructure and chemical structure of ZnO thin films. Undoped and Nd-doped ZnO films were deposited by RF co-sputtering from pure ZnO and metallic Nd targets in Ar plasma onto Si, quartz and glass substrates. The Nd concentration in the ZnO host matrix was varied in the range 0–26 at.% by varying the bias applied to the Nd target. A comprehensive characterization of the films properties was performed by X-ray photoelectron and Auger electron spectroscopies, X-ray fluorescence analysis, X-ray diffraction and scanning electron microscopy. At low Nd atomic concentration (Nd/Zn < 0.07) Nd atoms were successfully incorporated into the ZnO matrix, whose crystalline structure was preserved. A deterioration of the ZnO würtzite phase was observed on the contrary with increasing Nd content in the films together with the precipitation of a second phase, identified as Nd{sub 2}O{sub 3}.

  13. Effect of thickness on the structural and optical properties of sputtered ZnO and ZnO:Mn thin films

    International Nuclear Information System (INIS)

    Highlights: • ZnO and ZnO:Mn films of different thickness deposited by RF magnetron sputtering. • ZnO film of 80 nm shows a high crystalline quality with sharp band edge emission. • ZnO:Mn film of 90 nm shows a good crystallinity and prominent band edge emission. • Minimum lattice stress is observed for ZnO (80 nm) and ZnO:Mn (90 nm) films. - Abstract: We have deposited ZnO and 3% Mn doped ZnO (ZnO:Mn) thin films of different thickness by RF magnetron sputtering and studied the structural and optical properties. The deposited films were characterized by a host of characterization techniques, such as, X-ray diffraction, scanning electron microscopy, UV–visible transmittance and photoluminescence. The X-ray diffraction measurements on all the films show a preferential growth along c axis and the intensity of (0 0 2) peak is found to increase with increase of thickness up to 80 and 90 nm for ZnO and ZnO:Mn films respectively and decreases thereafter. The FESEM images of the films illustrate a hexagonal granular surface morphology for lower thickness and a growth of pyramidal nanostructures for higher thickness. The calculated values of the optical band gaps are found to decrease upon increasing the film thickness. Markedly, the band edge emission is large for 80 and 90 nm films of ZnO and ZnO:Mn respectively. The obtained optimized sputtering growth conditions will facilitate to exploit these ZnO and ZnO:Mn thin films for various device applications

  14. Ozone-assisted atomic layer deposited ZnO thin films for multifunctional device applications

    International Nuclear Information System (INIS)

    We demonstrate the growth temperature dependence of film thickness and surface roughness of ZnO films grown by atomic layer deposition using ozone as an oxidizer. The significantly low growth rate of the film using O3 precursor is attributed to the recombinative surface loss of O3. The variation of the spatial uniformity inferred from the surface roughness of the ZnO films and the O3 concentration was explained by a transition from reaction- to recombination-limited growth. We have fabricated a metal–oxide–semiconductor device, consisting of an insulating ZnO layer using an O3 source, between metallic and semiconducting Al : ZnO layers. The device demonstrates a remarkable resistive switching behaviour. The electrochemical migration of oxygen vacancies, which is created in the vicinity of the interface of ZnO semiconductor–ZnO insulator, drives the resistive switching behaviour. This significant result produced on the all-oxide-based device fabricated by atomic layer deposited ZnO can have significant impact for multifunctional applications. (paper)

  15. muSR proof of magnetism in undoped ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Tietze, Thomas; Audehm, Patrick; Goering, Eberhard [Max-Planck-Institut fuer Metallforschung, Heisenbergstr. 3, D-70569 Stuttgart (Germany); Straumal, Boris [Max-Planck-Institut fuer Metallforschung, Heisenbergstr. 3, D-70569 Stuttgart (Germany); Moscow Institute of Steel and Alloys, Technological University, Leninsky Prospect 4, 119991 Moscow (Russian Federation); Straumal, Peter [Moscow Institute of Steel and Alloys, Technological University, Leninsky Prospect 4, 119991 Moscow (Russian Federation); Salman, Zaher; Luetkens, Hubertus; Prokscha, Thomas [Paul Scherrer Institut, Labor fuer Myon-Spin Spektroskopie, CH-5232 Villigen PSI (Switzerland)

    2011-07-01

    Over the last decade tremendous efforts have been taken to reveal the origin of room temperature (RT) ferromagnetism (FM) in transition metal (TM) doped ZnO. SQUID measurements mostly showed ferromagnetic behavior whereas element specific methods like x-ray magnetic circular dichroism (XMCD) could not address the FM to any of the containing elements. FM occurred even in undoped ZnO, if the specific grain boundary area exceeds a threshold value. We suggest vacancy like states located at the grain boundaries as a possible source of the origin of RT FM of undoped ZnO. In order to proof intrinsic magnetism of nanostructured pure ZnO, we performed low energy muon spin rotation (LE-muSR) experiments at the Swiss Muon Source (SmuS). SQUID hysteresis loops revealed enhanced FM according to higher specific grain boundary area, in perfect agreement with our muSR measurements. The maximum muSR related magnetic volume fraction for nano grained samples was about 35%, while the pure ZnO single crystal sample was solely diamagnetic. Therefore, we present intrinsic evidence for a new type of RT-FM.

  16. Cotton Fabric Surface Modification by Sol-Gel Deposition of ZnO Thin Films

    International Nuclear Information System (INIS)

    One of the main tasks of research is to impact the additional value on natural textiles by adding to them ultraviolet (UV) absorption and antimicrobial protection properties with ZnO nano-level coatings. ZnO shows high absorption in the UV region of the light spectrum, in comparison with organic absorbers conventionally used in the textile industry shows no significant degradation, is stable and classified as non-toxic material. Nanosols were prepared by using the sol-gel process. In this work comparison of samples coated by nanosols with zinc acetate (Zn (CH3COO)2-2H2O) and zinc sulphate (ZnSO4) was made. Scanning electron microscopy (SEM) was used to examine the nature of the surface modification with ZnO coating by the sol-gel technique as also after exploitation of samples; energy dispersive X-ray spectroscopy was used for the analysis of elemental composition of coated fabric samples.

  17. Nanoporous characteristics of sol-gel-derived ZnO thin film

    Institute of Scientific and Technical Information of China (English)

    Anees A. Ansari; M. A. M. Khan; M. Alhoshan; S. A. Alrokayan; M. S. Alsalhi

    2012-01-01

    Sol-gel-derived nanoporous ZnO film has been successfully deposited on glass substrate at 200 ℃ and subsequently annealed at different temperatures of 300,400 and 600 ℃.Atomic force micrographs demonstrated that the film was crack-free,and that granular nanoparticles were homogenously distributed on the film surface.The average grain size of the nanoparticles and RMS roughness of the scanned surface area was 10 nm and 13.6nm,respectively,which is due to the high porosity of the film.Photoluminescence (PL) spectra of the nanoporous ZnO film at room temperature show a diffused band,which might be due to an increased amount of oxygen vacancies on the lattice surface.The observed results of the nanoporous ZnO film indicates a promising applicationin the development of electrochemical biosensors due to the porosity of film enhancing the higher loading of biomacromolecules (enzyme and proteins).

  18. Nanostructured Zn and ZnO nanowire thin films for mechanical and self-cleaning applications

    International Nuclear Information System (INIS)

    Highlights: • Zn metal films were deposited by thermal evaporation, on various substrates. • Upon annealing Zn there is transformation of the Zn nanosheets into ZnO nanowires. • ZnO nanowires are superhydrophobic and exhibit wetting transition on UV exposure. • ZnO will be useful in self-cleaning, mechanical and oxidation resistance surfaces. - Abstract: Nanostructured Zn metal films were deposited by thermal evaporation, on borosilicate glass, Quartz, sapphire, lanthanum aluminate and yttria stabilized zirconia substrates. The as-deposited films are nanocrystalline and show a morphology that consists of triangular nanosheets. The films are hydrophobic with contact angles between 102° and 120° with hardness and Young's modulus between 0.15–0.8 GPa and 18–300 GPa, respectively. Thermal annealing of the films at 500 °C results only in partial oxidation of Zn to ZnO, which indicates good oxidation resistance. Annealing also causes transformation of the Zn nanosheets into ZnO nanowires that are polycrystalline in nature. The ZnO nanowires are superhydrophobic with contact angles between 159° and 162°, contact angle hysteresis between 5° and 10° and exhibit a reversible superhydrophobic–hydrophilic transition under UV irradiation. The nanowires are much softer than the as-deposited Zn metal films, with hardness between 0.02 and 0.4 GPa and Young's modulus between 3 and 35 GPa. The current study thus demonstrates a simple process for fabrication of nanostructured Zn metal films followed by a one-step transformation to nanowires with properties that will be very attractive for mechanical and self-cleaning applications

  19. Nanostructured Zn and ZnO nanowire thin films for mechanical and self-cleaning applications

    Energy Technology Data Exchange (ETDEWEB)

    Shaik, Ummar Pasha [Advanced Centre of Research in High Energy Materials, University of Hyderabad, Prof. C R Rao Road, Gachibowli, Hyderabad 500046 (India); Purkayastha, Debarun Dhar, E-mail: ddebarun@yahoo.com [Department of Physics, National Institute of Technology Nagaland, Chumukedima, Dimapur 797103 (India); Krishna, M. Ghanashyam [Advanced Centre of Research in High Energy Materials, University of Hyderabad, Prof. C R Rao Road, Gachibowli, Hyderabad 500046 (India); School of Physics, University of Hyderabad, Prof. C R Rao Road, Gachibowli, Hyderabad 500046 (India); Madhurima, V. [Department of Physics, Central University of Tamil Nadu, Thiruvarur 610004 (India)

    2015-03-01

    Highlights: • Zn metal films were deposited by thermal evaporation, on various substrates. • Upon annealing Zn there is transformation of the Zn nanosheets into ZnO nanowires. • ZnO nanowires are superhydrophobic and exhibit wetting transition on UV exposure. • ZnO will be useful in self-cleaning, mechanical and oxidation resistance surfaces. - Abstract: Nanostructured Zn metal films were deposited by thermal evaporation, on borosilicate glass, Quartz, sapphire, lanthanum aluminate and yttria stabilized zirconia substrates. The as-deposited films are nanocrystalline and show a morphology that consists of triangular nanosheets. The films are hydrophobic with contact angles between 102° and 120° with hardness and Young's modulus between 0.15–0.8 GPa and 18–300 GPa, respectively. Thermal annealing of the films at 500 °C results only in partial oxidation of Zn to ZnO, which indicates good oxidation resistance. Annealing also causes transformation of the Zn nanosheets into ZnO nanowires that are polycrystalline in nature. The ZnO nanowires are superhydrophobic with contact angles between 159° and 162°, contact angle hysteresis between 5° and 10° and exhibit a reversible superhydrophobic–hydrophilic transition under UV irradiation. The nanowires are much softer than the as-deposited Zn metal films, with hardness between 0.02 and 0.4 GPa and Young's modulus between 3 and 35 GPa. The current study thus demonstrates a simple process for fabrication of nanostructured Zn metal films followed by a one-step transformation to nanowires with properties that will be very attractive for mechanical and self-cleaning applications.

  20. Defect Chemistry Study of Nitrogen Doped ZnO Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Miami University: Dr. Lei L. Kerr (PI, PD) Wright State University: Dr. David C. Look (PI) and Dr. Zhaoqiang Fang (Co-PI)

    2009-11-29

    Our team has inv