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Sample records for oxide zno crystal

  1. Giant negative photoresistance of ZnO single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Barzola-Quiquia, Jose; Esquinazi, Pablo [Division of Superconductivity and Magnetism, University of Leipzig (Germany); Heluani, Silvia [Laboratorio de Fisica del Solido, FCEyT, Universidad Nacional de Tucuman, 4000 S. M. de Tucuman (Argentina); Villafuerte, Manuel [Dept. de Fisica, FCEyT, Universidad Nacional de Tucuman (Argentina); CONICET, Tucuman (Argentina); Poeppl, Andreas [Division of Magnetic Resonance of Complex Quantum Solids, University of Leipzig, D-04103 Leipzig (Germany)

    2011-07-01

    ZnO is a wide band gap semiconductor exhibiting the largest charge-carrier mobility among oxides. ZnO is a material with potential applications for short-wavelength optoelectronic devices, as a blue light emitting diodes and in spintronics. In this contribution we have measured the temperature dependence (30 K < T < 300 K) of the electrical resistance of ZnO single crystals prepared by hydrothermal method in darkness and under the influence of light in the ultraviolet range. The resistance decreases several orders of magnitude at temperatures T < 200 K after illumination. Electron paramagnetic resonance studies under illumination reveal that the excitation of Li acceptor impurities is the origin for the giant negative photoresistance effect. Permanent photoresistance effect is also observed, which remains many hours after leaving the crystal in darkness.

  2. Sodium doping in ZnO crystals

    Science.gov (United States)

    Parmar, N. S.; Lynn, K. G.

    2015-01-01

    ZnO bulk single crystals were doped with sodium by thermal diffusion. Positron annihilations spectroscopy confirms the filling of zinc vacancies, to >6 μm deep in the bulk. Secondary-ion mass spectrometry measurement shows the diffusion of sodium up to 8 μm with concentration (1-3.5) × 1017 cm-3. Broad photoluminescence excitation peak at 3.1 eV, with onset appearance at 3.15 eV in Na:ZnO, is attributed to an electronic transition from a NaZn level at ˜(220-270) meV to the conduction band. Resistivity in Na doped ZnO crystals increases up to (4-5) orders of magnitude at room temperature.

  3. Sodium doping in ZnO crystals

    International Nuclear Information System (INIS)

    Parmar, N. S.; Lynn, K. G.

    2015-01-01

    ZnO bulk single crystals were doped with sodium by thermal diffusion. Positron annihilations spectroscopy confirms the filling of zinc vacancies, to >6 μm deep in the bulk. Secondary-ion mass spectrometry measurement shows the diffusion of sodium up to 8 μm with concentration (1–3.5) × 10 17  cm −3 . Broad photoluminescence excitation peak at 3.1 eV, with onset appearance at 3.15 eV in Na:ZnO, is attributed to an electronic transition from a Na Zn level at ∼(220–270) meV to the conduction band. Resistivity in Na doped ZnO crystals increases up to (4–5) orders of magnitude at room temperature

  4. Sodium doping in ZnO crystals

    Energy Technology Data Exchange (ETDEWEB)

    Parmar, N. S., E-mail: nparmar@wsu.edu; Lynn, K. G. [Center for Materials Research, Washington State University, Pullman, Washington 99164-2711 (United States)

    2015-01-12

    ZnO bulk single crystals were doped with sodium by thermal diffusion. Positron annihilations spectroscopy confirms the filling of zinc vacancies, to >6 μm deep in the bulk. Secondary-ion mass spectrometry measurement shows the diffusion of sodium up to 8 μm with concentration (1–3.5) × 10{sup 17 }cm{sup −3}. Broad photoluminescence excitation peak at 3.1 eV, with onset appearance at 3.15 eV in Na:ZnO, is attributed to an electronic transition from a Na{sub Zn} level at ∼(220–270) meV to the conduction band. Resistivity in Na doped ZnO crystals increases up to (4–5) orders of magnitude at room temperature.

  5. Zinc Oxide Nano crystals Synthesized by Quenching Technique

    International Nuclear Information System (INIS)

    Norhayati Abu Bakar; Akrajas Ali Umar; Muhamad Mat Salleh; Muhammad Yahya

    2011-01-01

    This paper reports an attempt to synthesize non toxic zinc oxide (ZnO) nano crystals using a simple quenching technique. The hot zinc oxide powder was quenched in hexane solution to obtain ZnO nano crystals. As the result, diameter size of the synthesized ZnO is 200 nm. It was also exhibited a good crystalline with wurtzite phase. The nano crystals properties of ZnO were revealed from good absorbance and green luminescence under UV exposure. This may be related with oxygen vacancy ionization during the annealing process. (author)

  6. Radio-frequency magnetron sputtering and wet thermal oxidation of ZnO thin film

    International Nuclear Information System (INIS)

    Liu, H. F.; Chua, S. J.; Hu, G. X.; Gong, H.; Xiang, N.

    2007-01-01

    The authors studied the growth and wet thermal oxidation (WTO) of ZnO thin films using a radio-frequency magnetron sputtering technique. X-ray diffraction reveals a preferred orientation of [1010]ZnO(0002)//[1120]Al 2 O 3 (0002) coexisted with a small amount of ZnO (1011) and ZnO (1013) crystals on the Al 2 O 3 (0001) substrate. The ZnO (1011) and ZnO (1013) crystals, as well as the in-plane preferred orientation, are absent from the growth of ZnO on the GaAs(001) substrate. WTO at 550 deg. C improves the crystalline and the photoluminescence more significantly than annealing in air, N 2 and O 2 ambient; it also tends to convert the crystal from ZnO (1011) and ZnO (1013) to ZnO (0002). The evolution of the photoluminescence upon WTO and annealing reveals that the green and orange emissions, centered at 520 and 650 nm, are likely originated from oxygen vacancies and oxygen interstitials, respectively; while the 420 nm emission, which is very sensitive to the postgrowth thermal processing regardless of the substrate and the ambient gas, is likely originated from the surface-state related defects

  7. ZnO crystals obtained by electrodeposition: Statistical analysis of most important process variables

    International Nuclear Information System (INIS)

    Cembrero, Jesus; Busquets-Mataix, David

    2009-01-01

    In this paper a comparative study by means of a statistical analysis of the main process variables affecting ZnO crystal electrodeposition is presented. ZnO crystals were deposited on two different substrates, silicon wafer and indium tin oxide. The control variables were substrate types, electrolyte concentration, temperature, exposition time and current density. The morphologies of the different substrates were observed using scanning electron microscopy. The percentage of substrate area covered by ZnO deposit was calculated by computational image analysis. The design of the applied experiments was based on a two-level factorial analysis involving a series of 32 experiments and an analysis of variance. Statistical results reveal that variables exerting a significant influence on the area covered by ZnO deposit are electrolyte concentration, substrate type and time of deposition, together with a combined two-factor interaction between temperature and current density. However, morphology is also influenced by surface roughness of the substrates

  8. Halide-oxide carbon vapor transport of ZnO: Novel approach for unseeded growth of single crystals with controllable growth direction

    Science.gov (United States)

    Colibaba, G. V.

    2018-05-01

    The thermodynamic analysis of using HCl + CO gas mixture as a chemical vapor transport agent (TA) for ZnO single crystal growth in closed ampoules, including 11 chemical species, is carried out for wide temperature and loaded TA pressure ranges. The advantages of HCl + CO TA for faster and more stable growth are shown theoretically in comparison with HCl, HCl + H2 and CO. The influence of the growth temperature, of the TA density, of the HCl/CO ratio, and of the undercooling on the ZnO mass transport rate was investigated theoretically and experimentally. The HCl/CO ratios favorable for the growth of m planes and (0001)Zn surface were found. It was shown that HCl + CO TA provides: (i) a rather high growth rate (up to 1.5 mm per day); (ii) a decrease of wall adhesion effect and an etch pit density down to 103 cm-2; (iii) a minimization of growth nucleus quantity down to 1; (iv) stable unseeded growth of the high crystalline quality large single crystals with a controllable preferred growth direction. The characterization by the photoluminescence spectra, the transmission spectra and the electrical properties are analyzed.

  9. Mechanism of oxidative stress involved in the toxicity of ZnO nanoparticles against eukaryotic cells

    Directory of Open Access Journals (Sweden)

    M. Saliani

    2016-01-01

    Full Text Available ZnO NPs (zinc oxide nanoparticles has generated significant scientific interest as a novel antibacterial and anticancer agent. Since oxidative stress is a critical determinant of ZnO NPs-induced damage, it is necessary to characterize their underlying mode of action. Different structural and physicochemical properties of ZnO NPs such as particle surface, size, shape, crystal structure, chemical position, and presence of metals can lead to changes in biological activities including ROS (reactive oxygen species production. However, there are some inconsistencies in the literature on the relation between the physicochemical features of ZnO NPs and their plausible oxidative stress mechanism. Herein, the possible oxidative stress mechanism of ZnO NPs was reviewed. This is worthy of further detailed evaluations in order to improve our understanding of vital NPs characteristics governing their toxicity. Therefore, this study focuses on the different reported oxidative stress paradigms induced by ZnO NPs including ROS generated by NPs, oxidative stress due to the NPs-cell interaction, and role of the particle dissolution in the oxidative damage. Also, this study tries to characterize and understand the multiple pathways involved in oxidative stress induced by ZnO NPs. Knowledge about different cellular signaling cascades stimulated by ZnO NPs lead to the better interpretation of the toxic influences induced by the cellular and acellular parameters. Regarding the potential benefits of toxic effects of ZnO NPs, in-depth evaluation of their toxicity mechanism and various effects of these nanoparticles would facilitate their implementation for biomedical applications.

  10. ZnO crystal growth on microelectrode by electrochemical deposition method

    International Nuclear Information System (INIS)

    Kondo, Y; Ashida, A; Nouzu, N; Fujimura, N

    2011-01-01

    Zinc Oxide crystals were grown by constant potential electrochemical deposition method on the substrate with the Pt working electrode which consists of Pt film with large area and μm-sized line and space structured area. In case of depositions with cathodic potential of -0.3V, ZnO crystal is not observed on the micro electrode, but observed on the electrode with large area (0.2 cm 2 ). By using electrolyte with higher pH, ZnO crystal grows on both areas. In case of lower pH, ZnO crystal does not grow on either. From these results, the pH range for growth of ZnO on the microelectrode seems to be higher than that on the electrode with large area. And, it is expected that the pH just on the surface of μm-sized electrode is lower than that in the bulk of electrolyte. Based on these results, it can be concluded that control of the pH in vicinity of the surface is very important to ECD method for micro- and nano-scaled devices.

  11. A comparison study between ZnO nanorods coated with graphene oxide and reduced graphene oxide

    International Nuclear Information System (INIS)

    Ding, Jijun; Wang, Minqiang; Deng, Jianping; Gao, Weiyin; Yang, Zhi; Ran, Chenxin; Zhang, Xiangyu

    2014-01-01

    Highlights: • Optical properties between ZnO-GO and ZnO-RGO composites were compared. • Photoluminescence quenching was observed in ZnO-GO composites. • We obtained enhanced photoluminescence in ZnO-RGO composites. -- Abstract: ZnO nanorods (ZnO NRs) coated with graphene oxide (ZnO-GO) and reduced graphene oxide sheets (ZnO-RGO) were prepared on indium tin oxide (ITO) substrates. The crystal structures, morphology and optical properties were analyzed by using X-ray diffraction (XRD) pattern, scanning electron microscopy (SEM) images, absorption spectra and photoluminescence (PL) spectra, respectively. A comparison between PL properties from ZnO-GO and ZnO-RGO were studied. Results indicated that the peak at 442 nm and a broad band at 450–600 nm of ZnO NRs show PL quenching after coating with GO sheets. As coating with RGO sheets, the extent of PL quenching increases. It is interesting to note that as ZnO NRs coated with RGO sheets, the intensity of PL peak at 390 nm significantly increased. The enhanced PL emission research in ZnO-RGO is directed toward development of the “nextgeneration” optoelectronics devices related with graphene materials

  12. Rapid growth of ZnO hexagonal prism crystals by direct microwave heating

    Institute of Scientific and Technical Information of China (English)

    ZHU Zhenqi; ZHOU Jian; LIU Guizhen; REN Zhiguo

    2008-01-01

    ZnO hexagonal prism crystals were synthesized from ZnO powders by microwave heating in a short time (within 20 min) without any metal catalyst or transport agent.Zinc oxide raw materials were made by evaporating from the high-temperature zone in an enclosure atmosphere and crystals were grown on the self-source substrate.The inherent asymmetry in microwave heating provides the temperature gradient for crystal growth.Substrate and temperature distribution in the oven show significant effects on the growth of the ZnO crystal.The morphologies demonstrate that these samples are pure hexagonal prism crystals with maximum 80 μm in diameter and 600 μm in length,which possess a well faceted end and side surface.X-ray diffraction (XRD) reveals that these samples are pure crystals.The photoluminescence (PL) exhibits strong ultraviolet emission at room temperature,indicating potential applications for short-wave light-emitting photonic devices.

  13. Photocatalytic Water Oxidation on ZnO: A Review

    Directory of Open Access Journals (Sweden)

    Sharifah Bee Abdul Hamid

    2017-03-01

    Full Text Available The investigation of the water oxidation mechanism on photocatalytic semiconductor surfaces has gained much attention for its potential to unlock the technological limitations of producing H2 from carbon-free sources, i.e., H2O. This review seeks to highlight the available scientific and fundamental understanding towards the water oxidation mechanism on ZnO surfaces, as well as present a summary on the modification strategies carried out to increase the photocatalytic response of ZnO.

  14. Point defects in ZnO crystals grown by various techniques

    International Nuclear Information System (INIS)

    Čížek, J; Vlček, M; Hruška, P; Lukáč, F; Melikhova, O; Anwand, W; Selim, F; Hugenschmidt, Ch; Egger, W

    2017-01-01

    In the present work point defects in ZnO crystals were characterized by positron lifetime spectroscopy combined with back-diffusion measurement of slow positrons. Defects in ZnO crystals grown by various techniques were compared. Hydrothermally grown ZnO crystals contain defects characterized by lifetime of ≈181 ps. These defects were attributed to Zn vacancies associated with hydrogen. ZnO crystals prepared by other techniques (Bridgman, pressurized melt growth, and seeded chemical vapour transport) exhibit shorter lifetime of ≈165 ps. Positron back-diffusion studies revealed that hydrothermally grown ZnO crystals contain higher density of defects than the crystals grown by other techniques. The lowest concentration of defects was detected in the crystal grown by seeded chemical vapor transport. (paper)

  15. ZNO and AG-ZNO crystals: synthesis, characterization, and application in heterogeneous photocatalysis

    Directory of Open Access Journals (Sweden)

    Adriana Campano Lucilha

    2016-05-01

    Full Text Available ZnO and Ag-ZnO were synthesized in a simple and efficient manner by thermal decomposition of zinc oxalate and silver/zinc mixed oxalate. The influence of the addition of metallic silver on ZnO particles and the effect of temperature in the thermal treatment were investigated. The samples were characterized by thermogravimetric analysis, Raman, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, specific surface area (Brunauer-Emmett-Teller and diffuse reflectance spectroscopy. The photocatalytic activity of these materials in the decolorization of direct red 23 diazo dye was studied. The complete conversion into oxides from oxalates at lower temperatures was determinant in the photocatalytic efficiency of both the oxides. The presence of silver in zinc oxide, treated at 400 °C, more than doubled the rate constant of diazo dye decolorization (6.87×10-3 min-1 with respect to ZnO, treated at 600 °C, resulting in 3.07×10-3 min-1 under UV irradiation at 30 °C.

  16. Hydrogen-related complexes in Li-diffused ZnO single crystals

    Science.gov (United States)

    Corolewski, Caleb D.; Parmar, Narendra S.; Lynn, Kelvin G.; McCluskey, Matthew D.

    2016-07-01

    Zinc oxide (ZnO) is a wide band gap semiconductor and a potential candidate for next generation white solid state lighting applications. In this work, hydrogen-related complexes in lithium diffused ZnO single crystals were studied. In addition to the well-known Li-OH complex, several other hydrogen defects were observed. When a mixture of Li2O and ZnO is used as the dopant source, zinc vacancies are suppressed and the bulk Li concentration is very high (>1019 cm-3). In that case, the predominant hydrogen complex has a vibrational frequency of 3677 cm-1, attributed to surface O-H species. When Li2CO3 is used, a structured blue luminescence band and O-H mode at 3327 cm-1 are observed at 10 K. These observations, along with positron annihilation measurements, suggest a zinc vacancy-hydrogen complex, with an acceptor level ˜0.3 eV above the valence-band maximum. This relatively shallow acceptor could be beneficial for p-type ZnO.

  17. Hydrogen-related complexes in Li-diffused ZnO single crystals

    International Nuclear Information System (INIS)

    Corolewski, Caleb D.; Parmar, Narendra S.; Lynn, Kelvin G.; McCluskey, Matthew D.

    2016-01-01

    Zinc oxide (ZnO) is a wide band gap semiconductor and a potential candidate for next generation white solid state lighting applications. In this work, hydrogen-related complexes in lithium diffused ZnO single crystals were studied. In addition to the well-known Li-OH complex, several other hydrogen defects were observed. When a mixture of Li_2O and ZnO is used as the dopant source, zinc vacancies are suppressed and the bulk Li concentration is very high (>10"1"9" cm"−"3). In that case, the predominant hydrogen complex has a vibrational frequency of 3677 cm"−"1, attributed to surface O-H species. When Li_2CO_3 is used, a structured blue luminescence band and O-H mode at 3327 cm"−"1 are observed at 10 K. These observations, along with positron annihilation measurements, suggest a zinc vacancy–hydrogen complex, with an acceptor level ∼0.3 eV above the valence-band maximum. This relatively shallow acceptor could be beneficial for p-type ZnO.

  18. Hydrogen-related complexes in Li-diffused ZnO single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Corolewski, Caleb D. [Materials Science and Engineering Program, Washington State University, Pullman, Washington 99164-2814 (United States); Parmar, Narendra S.; Lynn, Kelvin G. [Center for Materials Research, Washington State University, Pullman, Washington 99164-2814 (United States); McCluskey, Matthew D., E-mail: mattmcc@wsu.edu [Materials Science and Engineering Program, Washington State University, Pullman, Washington 99164-2814 (United States); Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164-2814 (United States)

    2016-07-21

    Zinc oxide (ZnO) is a wide band gap semiconductor and a potential candidate for next generation white solid state lighting applications. In this work, hydrogen-related complexes in lithium diffused ZnO single crystals were studied. In addition to the well-known Li-OH complex, several other hydrogen defects were observed. When a mixture of Li{sub 2}O and ZnO is used as the dopant source, zinc vacancies are suppressed and the bulk Li concentration is very high (>10{sup 19 }cm{sup −3}). In that case, the predominant hydrogen complex has a vibrational frequency of 3677 cm{sup −1}, attributed to surface O-H species. When Li{sub 2}CO{sub 3} is used, a structured blue luminescence band and O-H mode at 3327 cm{sup −1} are observed at 10 K. These observations, along with positron annihilation measurements, suggest a zinc vacancy–hydrogen complex, with an acceptor level ∼0.3 eV above the valence-band maximum. This relatively shallow acceptor could be beneficial for p-type ZnO.

  19. Synthesis and characterization of thermally oxidized ZnO films

    Indian Academy of Sciences (India)

    Administrator

    Synthesis and characterization of thermally oxidized ZnO films. A P RAMBU1,* and N IFTIMIE2 .... R. −. Δ. = = (1) where Ra is the sensor resistance in the air and Rg is the .... ple, Aida and coworkers (2006) reported that the total oxidation is ...

  20. 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.

  1. Thermally induced growth of ZnO nanocrystals on mixed metal oxide surfaces.

    Science.gov (United States)

    Inayat, Alexandra; Makky, Ayman; Giraldo, Jose; Kuhnt, Andreas; Busse, Corinna; Schwieger, Wilhelm

    2014-06-23

    An in situ method for the growth of ZnO nanocrystals on Zn/Al mixed metal oxide (MMO) surfaces is presented. The key to this method is the thermal treatment of Zn/Al layered double hydroxides (Zn/Al LDHs) in the presence of nitrate anions, which results in partial demixing of the LDH/MMO structure and the subsequent crystallization of ZnO crystals on the surface of the forming MMO layers. In a first experimental series, thermal treatment of Zn/Al LDHs with different fractions of nitrate and carbonate in the interlayer space was examined by thermogravimetry coupled with mass spectrometry (TG-MS) and in situ XRD. In a second experimental series, Zn/Al LDHs with only carbonate in the interlayer space were thermally treated in the presence of different amounts of an external nitrate source (NH4NO3). All obtained Zn/Al MMO samples were analysed by electron microscopy, nitrogen physisorption and powder X-ray diffraction. The gas phase formed during nitrate decomposition turned out to be responsible for the formation of crystalline ZnO nanoparticles. Accordingly, both interlayer nitrate and the presence of ammonium nitrate led to the formation of supported ZnO nanocrystals with mean diameters between 100 and 400 nm, and both methods offer the possibility to tailor the amount and size of the ZnO crystals by means of the amount of nitrate. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Optical and scintillation properties of bulk ZnO crystal

    Energy Technology Data Exchange (ETDEWEB)

    Yanagida, Takayuki [Kyushu Institute of Technology, 2-4 Hibikino, Wakamatsu, Kitakyushu 808-0196 (Japan); Fujimoto, Yutaka; Kurosawa, Shunsuke [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Yamanoi, Kohei; Sarukura, Nobuhiko [Institute of Laser Engineering, Osaka University, Suita, Osaka 565-0871 (Japan); Kano, Masataka; Wakamiya, Akira [Daishinku Corporation, 1389 Shinzaike, Hiraoka-cho, Kakogawa, Hyogo 675-0194 (Japan)

    2012-12-15

    Single crystal bulk ZnO scintillator grown by the hydrothermal method was tested on its scintillation performances. In X-ray induced radio luminescence spectrum, it exhibited two intense emission peaks at 400 and 550 nm. The former was ascribed to the free and bound exciton related luminescence and the latter to oxygen vacancy related one, respectively. X-ray induced scintillation decay time of the exciton related emission measured by the pulse X-ray streak camera system resulted {proportional_to} 4 ns. Finally, the light yield under {sup 241}Am 5.5 MeV {alpha}-ray was examined and it resulted {proportional_to} 500 ph/5.5 MeV-{alpha}.(copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

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

    KAUST Repository

    Wang, Xudong; Ding, Yong; Li, Zhou; Song, Jinhui; Wang, Zhong Lin

    2009-01-01

    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

  4. Physical deoxygenation of graphene oxide paper surface and facile in situ synthesis of graphene based ZnO films

    International Nuclear Information System (INIS)

    Ding, Jijun; Wang, Minqiang; Zhang, Xiangyu; Ran, Chenxin; Shao, Jinyou; Ding, Yucheng

    2014-01-01

    In-situ sputtering ZnO films on graphene oxide (GO) paper are used to fabricate graphene based ZnO films. Crystal structure and surface chemical states are investigated. Results indicated that GO paper can be effectively deoxygenated by in-situ sputtering ZnO on them without adding any reducing agent. Based on the principle of radio frequency magnetron sputtering, we propose that during magnetron sputtering process, plasma streams contain large numbers of electrons. These electrons not only collide with argon atoms to produce secondary electrons but also they are accelerated to bombard the substrates (GO paper) resulting in effective deoxygenation of oxygen-containing functional groups. In-situ sputtering ZnO films on GO paper provide an approach to design graphene-semiconductor nanocomposites

  5. Hydrothermal temperature effect on crystal structures, optical properties and electrical conductivity of ZnO nanostructures

    Science.gov (United States)

    Dhafina, Wan Almaz; Salleh, Hasiah; Daud, Mohd Zalani; Ghazali, Mohd Sabri Mohd; Ghazali, Salmah Mohd

    2017-09-01

    ZnO is an wide direct band gap semiconductor and possess rich family of nanostructures which turned to be a key role in the nanotechnology field of applications. Hydrothermal method was proven to be simple, robust and low cost among the reported methods to synthesize ZnO nanostructures. In this work, the properties of ZnO nanostructures were altered by varying temperatures of hydrothermal process. The changes in term of morphological, crystal structures, optical properties and electrical conductivity were investigated. A drastic change of ZnO nanostructures morphology and decreases of 002 diffraction peak were observed as the hydrothermal temperature increased. The band gap of samples decreased as the size of ZnO nanostructure increased, whereas the electrical conductivity had no influence on the band gap value but more on the morphology of ZnO nanostructures instead.

  6. Formation of different micro-morphologies from VO2 and ZnO crystallization using macro-porous silicon substrates

    Science.gov (United States)

    Salazar-Kuri, U.; Antúnez, E. E.; Estevez, J. O.; Olive-Méndez, Sion F.; Silva-González, N. R.; Agarwal, V.

    2017-05-01

    Square-shaped macropores produced by electrochemical anodization of n- and p-type Si wafers have been used as centers of nucleation to crystallize VO2 and ZnO. Substrate roughness dependent formation of different morphologies is revealed in the form of squared particles, spheres, bars and ribbons in the case of VO2 and hexagonal piles and spheres in the case of ZnO, have been observed.The presence of nano-/micro-metric crystals was studied through field emission scanning electron microscopy and energy dispersive X-ray spectroscopy mapping. Crystal structure of metal oxides was confirmed by micro-Raman spectroscopy. The growth of the different morphologies has been explained in terms of the surface free energy of a bare Si/SiO2 substrate and its modification originated from the roughness of the surface and of the walls of the porous substrates. This energy plays a crucial role on the minimization of the required energy to induce heterogeneous nucleation and crystal growth. Present work strengthens and provides an experimental evidence of roughness dependent metal oxide crystal growth with well-defined habits from pore corners and rough sides of the pore walls, similar to already reported protein crystals.

  7. Crystallization inhibitors for amorphous oxides

    International Nuclear Information System (INIS)

    Reznitskij, L.A.; Filippova, S.E.

    1993-01-01

    Data for the last 10 years, in which experimental results of studying the temperature stabilization of x-ray amorphous oxides (including R 3 Fe 5 O 12 R-rare earths, ZrO 2 , In 2 O 3 , Sc 2 O 3 ) and their solid solution are presented, are generalized. Processes of amorphous oxide crystallization with the production of simple oxides, solid solutions and chemical compounds with different polyhedral structure, are investigated. Energy and crystallochemical criteria for selecting the doping inhibitor-components stabilizing the amorphous state are ascertained, temperatures and enthalpies of amorpous oxide crystallization are determined, examination of certain provisions of iso,orphous miscibility theory is conducted

  8. Study of defects and vacancies in structural properties of Mn, co-doped oxides: ZnO

    Science.gov (United States)

    Kumar, Harish; Kaushik, A.; Alvi, P. A.; Dalela, B.; Dalela, S.

    2018-05-01

    The paper deals with the Structural properties on Mn, Co doped oxides ZnO samples using XRD, Positron Annihilation Lifetime (PAL) Spectra and Raman Spectra. The Mn, Co doped ZnO samples crystallize in a wurtzite structure without any impurity phases in XRD Spectra. The defect state of these samples has been investigated by using positron annihilation lifetime (PAL) spectroscopy technique in which all the relevant lifetime parameters are measured for all the spectra. The results are explained in the direction of doping concentration in these samples in terms of defects structure on Zn lattice site VZn and oxygen defects Vo.

  9. Catalyst growth of single crystal aligned ZnO nanorods on ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Dongxu; Andreazza, Caroline; Andreazza, Pascal [Centre de Recherche sur la Matiere Divisee, CNRS-Universite d' Orleans, 1b rue de la Ferollerie, 45071 Orleans cedex 2 (France)

    2005-02-01

    One dimensional ZnO nanorods were successfully fabricated on Si substrates via a simple physical vapor-phase transport method at 950 C. A ZnO shell covered Au/Zn alloy is assumed as the nucleation site, then ZnO nanorods grow following a vapor-solid (VS) process. In order to guide the nanorod growth a c-axis oriented ZnO thin film and Au catalyst were first deposited on Si (100) surface. SEM images show nanorods grown on this substrate are vertical to the substrate surface. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Structural and magnetic properties of Tb implanted ZnO single crystals

    International Nuclear Information System (INIS)

    Zhou Shengqiang; Potzger, K.; Muecklich, A.; Eichhorn, F.; Helm, M.; Skorupa, W.; Fassbender, J.

    2008-01-01

    ZnO single crystals have been implanted with Tb ions. For an atomic concentration of 1.5%, annealing at 823 K leads to an increase of the saturation magnetization per implanted Tb ion up to 1.8 μ B at room temperature. Structural investigations revealed no secondary phase formation, but the out-diffusion of Tb. No significant evidence is found for Tb substituting Zn sites either in the as-implanted or annealed samples. However, indications for the existence of a small amount of Tb nanoclusters however have been found using magnetization versus temperature measurements. The ferromagnetic properties disappear completely upon annealing at 1023 K. This behavior is related to the formation of oxide complexes or nanoparticles

  11. Potassium acceptor doping of ZnO crystals

    Directory of Open Access Journals (Sweden)

    Narendra S. Parmar

    2015-05-01

    Full Text Available ZnO bulk single crystals were doped with potassium by diffusion at 950°C. Positron annihilation spectroscopy confirms the filling of zinc vacancies and a different trapping center for positrons. Secondary ion mass spectroscopy measurements show the diffusion of potassium up to 10 μm with concentration ∼1 × 1016 cm−3. IR measurements show a local vibrational mode (LVM at 3226 cm−1, at a temperature of 9 K, in a potassium doped sample that was subsequently hydrogenated. The LVM is attributed to an O–H bond-stretching mode adjacent to a potassium acceptor. When deuterium substitutes for hydrogen, a peak is observed at 2378 cm−1. The O-H peak is much broader than the O-D peak, perhaps due to an unusually low vibrational lifetime. The isotopic frequency ratio is similar to values found in other hydrogen complexes. Potassium doping increases the resistivity up to 3 orders of magnitude at room temperature. The doped sample has a donor level at 0.30 eV.

  12. Potassium acceptor doping of ZnO crystals

    Science.gov (United States)

    Parmar, Narendra S.; Corolewski, Caleb D.; McCluskey, Matthew D.; Lynn, K. G.

    2015-05-01

    ZnO bulk single crystals were doped with potassium by diffusion at 950°C. Positron annihilation spectroscopy confirms the filling of zinc vacancies and a different trapping center for positrons. Secondary ion mass spectroscopy measurements show the diffusion of potassium up to 10 μm with concentration ˜1 × 1016 cm-3. IR measurements show a local vibrational mode (LVM) at 3226 cm-1, at a temperature of 9 K, in a potassium doped sample that was subsequently hydrogenated. The LVM is attributed to an O-H bond-stretching mode adjacent to a potassium acceptor. When deuterium substitutes for hydrogen, a peak is observed at 2378 cm-1. The O-H peak is much broader than the O-D peak, perhaps due to an unusually low vibrational lifetime. The isotopic frequency ratio is similar to values found in other hydrogen complexes. Potassium doping increases the resistivity up to 3 orders of magnitude at room temperature. The doped sample has a donor level at 0.30 eV.

  13. Potassium acceptor doping of ZnO crystals

    Energy Technology Data Exchange (ETDEWEB)

    Parmar, Narendra S., E-mail: nparmar@wsu.edu; Lynn, K. G. [Center for Materials Research, Washington State University, Pullman, Washington 99164-2711 (United States); Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164-2814 (United States); Corolewski, Caleb D.; McCluskey, Matthew D. [Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164-2814 (United States)

    2015-05-15

    ZnO bulk single crystals were doped with potassium by diffusion at 950°C. Positron annihilation spectroscopy confirms the filling of zinc vacancies and a different trapping center for positrons. Secondary ion mass spectroscopy measurements show the diffusion of potassium up to 10 μm with concentration ∼1 × 10{sup 16} cm{sup −3}. IR measurements show a local vibrational mode (LVM) at 3226 cm{sup −1}, at a temperature of 9 K, in a potassium doped sample that was subsequently hydrogenated. The LVM is attributed to an O–H bond-stretching mode adjacent to a potassium acceptor. When deuterium substitutes for hydrogen, a peak is observed at 2378 cm{sup −1}. The O-H peak is much broader than the O-D peak, perhaps due to an unusually low vibrational lifetime. The isotopic frequency ratio is similar to values found in other hydrogen complexes. Potassium doping increases the resistivity up to 3 orders of magnitude at room temperature. The doped sample has a donor level at 0.30 eV.

  14. Encapsulation of nanoparticles into single-crystal ZnO nanorods and microrods

    Directory of Open Access Journals (Sweden)

    Jinzhang Liu

    2014-04-01

    Full Text Available One-dimensional single crystal incorporating functional nanoparticles of other materials could be an interesting platform for various applications. We studied the encapsulation of nanoparticles into single-crystal ZnO nanorods by exploiting the crystal growth of ZnO in aqueous solution. Two types of nanodiamonds with mean diameters of 10 nm and 40 nm, respectively, and polymer nanobeads with size of 200 nm have been used to study the encapsulation process. It was found that by regrowing these ZnO nanorods with nanoparticles attached to their surfaces, a full encapsulation of nanoparticles into nanorods can be achieved. We demonstrate that our low-temperature aqueous solution growth of ZnO nanorods do not affect or cause degradation of the nanoparticles of either inorganic or organic materials. This new growth method opens the way to a plethora of applications combining the properties of single crystal host and encapsulated nanoparticles. We perform micro-photoluminescence measurement on a single ZnO nanorod containing luminescent nanodiamonds and the spectrum has a different shape from that of naked nanodiamonds, revealing the cavity effect of ZnO nanorod.

  15. Encapsulation of nanoparticles into single-crystal ZnO nanorods and microrods.

    Science.gov (United States)

    Liu, Jinzhang; Notarianni, Marco; Rintoul, Llew; Motta, Nunzio

    2014-01-01

    One-dimensional single crystal incorporating functional nanoparticles of other materials could be an interesting platform for various applications. We studied the encapsulation of nanoparticles into single-crystal ZnO nanorods by exploiting the crystal growth of ZnO in aqueous solution. Two types of nanodiamonds with mean diameters of 10 nm and 40 nm, respectively, and polymer nanobeads with size of 200 nm have been used to study the encapsulation process. It was found that by regrowing these ZnO nanorods with nanoparticles attached to their surfaces, a full encapsulation of nanoparticles into nanorods can be achieved. We demonstrate that our low-temperature aqueous solution growth of ZnO nanorods do not affect or cause degradation of the nanoparticles of either inorganic or organic materials. This new growth method opens the way to a plethora of applications combining the properties of single crystal host and encapsulated nanoparticles. We perform micro-photoluminescence measurement on a single ZnO nanorod containing luminescent nanodiamonds and the spectrum has a different shape from that of naked nanodiamonds, revealing the cavity effect of ZnO nanorod.

  16. Effects of Doping Concentration on the Structural and Optical Properties of Spin-Coated In-doped ZnO Thin Films Grown on Thermally Oxidized ZnO Film/ZnO Buffer Layer/Mica Substrate

    International Nuclear Information System (INIS)

    Kim, Byunggu; Leem, Jae-Young

    2017-01-01

    ZnO buffer layers were deposited on mica substrates using a sol-gel spin coating method. Then, a thin film of metallic Zn was deposited onto the ZnO buffer layer/mica substrate using a thermal evaporator, and the deposited Zn thin films were then thermally oxidized in a furnace at 500 ℃ for 2 h in air. Finally, In-doped ZnO (IZO) thin films with different In concentrations were grown on the oxidized ZnO film/ZnO buffer layer/mica substrates using the sol-gel spin-coating method. All the IZO films showed ZnO peaks with similar intensities. The full width at half maximum values of the ZnO (002) peak for the IZO thin films decreased with an increase in the In concentration to 1 at%, because the crystallinity of the films was enhanced. However, a further increase in the In concentration caused the crystal quality to degrade. This might be attributed to the fact that the higher In doping resulted in an increase in the number of ionized impurities. The Urbach energy (EU) values of the IZO thin film decreased with an increase in the In concentration to 1 at % because of the enhanced crystal quality of the films. The EU values for the IZO thin films increased with the In concentration from 1 at%to 3 at%, reflecting the broadening of localized band tail state near the conduction band edge of the films.

  17. Effects of Doping Concentration on the Structural and Optical Properties of Spin-Coated In-doped ZnO Thin Films Grown on Thermally Oxidized ZnO Film/ZnO Buffer Layer/Mica Substrate

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Byunggu; Leem, Jae-Young [Inje University, Gimhae (Korea, Republic of)

    2017-01-15

    ZnO buffer layers were deposited on mica substrates using a sol-gel spin coating method. Then, a thin film of metallic Zn was deposited onto the ZnO buffer layer/mica substrate using a thermal evaporator, and the deposited Zn thin films were then thermally oxidized in a furnace at 500 ℃ for 2 h in air. Finally, In-doped ZnO (IZO) thin films with different In concentrations were grown on the oxidized ZnO film/ZnO buffer layer/mica substrates using the sol-gel spin-coating method. All the IZO films showed ZnO peaks with similar intensities. The full width at half maximum values of the ZnO (002) peak for the IZO thin films decreased with an increase in the In concentration to 1 at%, because the crystallinity of the films was enhanced. However, a further increase in the In concentration caused the crystal quality to degrade. This might be attributed to the fact that the higher In doping resulted in an increase in the number of ionized impurities. The Urbach energy (EU) values of the IZO thin film decreased with an increase in the In concentration to 1 at % because of the enhanced crystal quality of the films. The EU values for the IZO thin films increased with the In concentration from 1 at%to 3 at%, reflecting the broadening of localized band tail state near the conduction band edge of the films.

  18. Oxidant-Dependent Thermoelectric Properties of Undoped ZnO Films by Atomic Layer Deposition

    KAUST Repository

    Kim, Hyunho

    2017-02-27

    Extraordinary oxidant-dependent changes in the thermoelectric properties of undoped ZnO thin films deposited by atomic layer deposition (ALD) have been observed. Specifically, deionized water and ozone oxidants are used in the growth of ZnO by ALD using diethylzinc as a zinc precursor. No substitutional atoms have been added to the ZnO films. By using ozone as an oxidant instead of water, a thermoelectric power factor (σS) of 5.76 × 10 W m K is obtained at 705 K for undoped ZnO films. In contrast, the maximum power factor for the water-based ZnO film is only 2.89 × 10 W m K at 746 K. Materials analysis results indicate that the oxygen vacancy levels in the water- and ozone-grown ZnO films are essentially the same, but the difference comes from Zn-related defects present in the ZnO films. The data suggest that the strong oxidant effect on thermoelectric performance can be explained by a mechanism involving point defect-induced differences in carrier concentration between these two oxides and a self-compensation effect in water-based ZnO due to the competitive formations of both oxygen and zinc vacancies. This strong oxidant effect on the thermoelectric properties of undoped ZnO films provides a pathway to improve the thermoelectric performance of this important material.

  19. Photoelectrochemical Stability and Alteration Products of n-Type Single-Crystal ZnO Photoanodes

    Directory of Open Access Journals (Sweden)

    I. E. Paulauskas

    2011-01-01

    Full Text Available The photoelectrochemical stability and surface-alteration characteristics of doped and undoped n-type ZnO single-crystal photoanode electrodes were investigated. The single-crystal ZnO photoanode properties were analyzed using current-voltage measurements plus spectral and time-dependent quantum-yield methods. These measurements revealed a distinct anodic peak and an accompanying cathodic surface degradation process at negative potentials. The features of this peak depended on time and the NaOH concentration in the electrolyte, but were independent of the presence of electrode illumination. Current measurements performed at the peak indicate that charging and discharging effects are apparently taking place at the semiconductor/electrolyte interface. This result is consistent with the significant reactive degradation that takes place on the ZnO single crystal photoanode surface and that ultimately leads to the reduction of the ZnO surface to Zn metal. The resulting Zn-metal reaction products create unusual, dendrite-like, surface alteration structural features that were analyzed using x-ray diffraction, energy-dispersive analysis, and scanning electron microscopy. ZnO doping methods were found to be effective in increasing the n-type character of the crystals. Higher doping levels result in smaller depletion widths and lower quantum yields, since the minority carrier diffusion lengths are very short in these materials.

  20. Fabrication and Characterization of Vertically Aligned ZnO Nanorod Arrays via Inverted Monolayer Colloidal Crystals Mask

    Science.gov (United States)

    Chen, Cheng; Ding, Taotao; Qi, Zhiqiang; Zhang, Wei; Zhang, Jun; Xu, Juan; Chen, Jingwen; Dai, Jiangnan; Chen, Changqing

    2018-04-01

    The periodically ordered ZnO nanorod (NR) arrays have been successfully synthesized via a hydrothermal approach on the silicon substrates by templating of the TiO2 ring deriving from the polystyrene (PS) nanosphere monolayer colloidal crystals (MCC). With the inverted MCC mask, sol-gel-derived ZnO seeds could serve as the periodic nucleation positions for the site-specific growth of ZnO NRs. The large-scale patterned arrays of single ZnO NR with good side-orientation can be readily produced. According to the experimental results, the as-integrated ZnO NR arrays showed an excellent crystal quality and optical property, very suitable for optoelectronic applications such as stimulated emitters and ZnO photonic crystal devices.

  1. Influence of ZnO nanostructures in liquid crystal interfaces for bistable switching applications

    Energy Technology Data Exchange (ETDEWEB)

    Pal, Kaushik, E-mail: kaushikpal@whu.edu.cn [School of Power and Mechanical Engineering, Wuhan University, 8 East Lake South Road, Wuhan 430072 (China); Zhan, Bihong, E-mail: bihong_zhan@whu.edu.cn [School of Power and Mechanical Engineering, Wuhan University, 8 East Lake South Road, Wuhan 430072 (China); Madhu Mohan, M.L.N. [Liquid Crystal Research Laboratory (LCRL), Bannari Amman Institute of Technology, Sathyamangalam 638 401 (India); Schirhagl, Romana [University Medical Center Groningen, Department of BioMedical Engineering, Ant. Deusinglaan 1, 9713 AV Groningen (Netherlands); Wang, Guoping, E-mail: guopingwang@whu.edu.cn [School of Power and Mechanical Engineering, Wuhan University, 8 East Lake South Road, Wuhan 430072 (China)

    2015-12-01

    Graphical abstract: - Highlights: • One step bench top novel synthesis and growth dynamics of ZnO structures are successfully performed. • Nanostructures dispersing liquid crystals (NDLC) is recently found to have significant influence on the nucleation and growth of many functional nanocrystals (NCs), and provide a fundamental approach to modify the crystallographic phase, size, morphology, and electronic configuration of nanomaterials. • Electro-optical switching application ensures the bright field droplet design marble pattern of smectic G phase, nematic and most significant twist nematic phase pattern are obtained. • Spontaneous polarization, rotational viscosity and response time study, exploring smart applications in LCD technology. - Abstract: The controlled fabrication of nanometer-scale objects is without doubt one of the central issues in current science and technology. In this article, we exhibit a simple, one-step bench top synthesis of zinc oxide nano-tetrapods and nano-spheres which were tailored by the facial growth of nano-wires (diameter ≈ 24 nm; length ≈ 118 nm) and nano-cubes (≈395 nm edge) to nano-sphere (diameter ≈ 585 nm) appeaded. The possibilities of inexpensive, simple solvo-chemical synthesis of nanostructures were considered. In this article, a successful attempt has been made that ZnO nano-structures dispersed on well aligned hydrogen bonded liquid crystals (HBLC) comprising azelaic acid (AC) with p-n-alkyloxy benzoic acid (nBAO) by varying the respective alkyloxy carbon number (n = 5). The dispersion of nanomaterials with HBLC is an effective route to enhance the existing functionalities. A series of these composite materials were analyzed by polarizing optical microscope's electro-optical switching. An interesting feature of AC + nBAO is the inducement of tilted smectic G phase with increasing carbon chain length. Phase diagrams of the above hybrid ZnO nanomaterial influenced LC complex and pure LC were

  2. Defect studies of ZnO single crystals electrochemically doped with hydrogen

    Science.gov (United States)

    Čížek, J.; Žaludová, N.; Vlach, M.; Daniš, S.; Kuriplach, J.; Procházka, I.; Brauer, G.; Anwand, W.; Grambole, D.; Skorupa, W.; Gemma, R.; Kirchheim, R.; Pundt, A.

    2008-03-01

    Various defect studies of hydrothermally grown (0001) oriented ZnO crystals electrochemically doped with hydrogen are presented. The hydrogen content in the crystals is determined by nuclear reaction analysis and it is found that already 0.3at.% H exists in chemically bound form in the virgin ZnO crystals. A single positron lifetime of 182ps is detected in the virgin crystals and attributed to saturated positron trapping at Zn vacancies surrounded by hydrogen atoms. It is demonstrated that a very high amount of hydrogen (up to ˜30at.%) can be introduced into the crystals by electrochemical doping. More than half of this amount is chemically bound, i.e., incorporated into the ZnO crystal lattice. This drastic increase of the hydrogen concentration is of marginal impact on the measured positron lifetime, whereas a contribution of positrons annihilated by electrons belonging to O-H bonds formed in the hydrogen doped crystal is found in coincidence Doppler broadening spectra. The formation of hexagonal shape pyramids on the surface of the hydrogen doped crystals by optical microscopy is observed and discussed.

  3. Positron annihilation lifetime measurement of electron-irradiated ZnO crystals

    International Nuclear Information System (INIS)

    Tomiyama, N.; Takenaka, M.; Kuramoto, E.

    1992-01-01

    In order to clarify the basic properties of radiation-induced defects in ZnO crystals positron annihilation lifetime measurements were performed for the ZnO crystals irradiated by 28 MeV electrons at 77 K. The electron-irradiation induced the color change of the specimens from the original yellowish-white to the orange and long lifetime component of about 200 psec. The isochronal annealing experiments showed that the decrease of the positron annihilation lifetime appeared in the temperature range between 423 and 473 K and between 723 and 923 K. The radiation-induced color change disappeared in the first temperature range. It can be considered that the first stage corresponds to migration and recovery of radiation-induced oxygen vacancies. It is difficult to identify the second stage, but it might be the recovery stage of small ZnO interstitial clusters formed through clustering of Zn and O interstitials

  4. Crystal and electronic structure study of Mn doped wurtzite ZnO nanoparticles

    Directory of Open Access Journals (Sweden)

    O.M. Ozkendir

    2016-08-01

    Full Text Available The change in the crystal and electronic structure properties of wurtzite ZnO nanoparticles was studied according to Mn doping in the powder samples. The investigations were conducted by X-ray Absorption Fine Structure Spectroscopy (XAFS technique for the samples prepared with different heating and doping processes. Electronic analysis was carried out by the collected data from the X-ray Absorption Near-Edge Structure Spectroscopy (XANES measurements. Additional crystal structure properties were studied by Extended-XAFS (EXAFS analysis. Longer heating periods for the undoped wurtzite ZnO samples were determined to own stable crystal geometries. However, for some doped samples, the distortions in the crystal were observed as a result of the low doping amounts of Mn which was treated as an impurity. Besides, the changes in oxygen locations were determined to create defects and distortions in the samples.

  5. Emission characteristics of electrically- and optically-pumped single ZnO micro-spherical crystal

    Science.gov (United States)

    Nakamura, D.; Shimogaki, T.; Tetsuyama, N.; Fusazaki, K.; Mizokami, Y.; Higashihata, M.; Ikenoue, H.; Okada, T.

    2014-03-01

    Zinc oxide (ZnO) nano/microstructures have been attractive as the building blocks for the efficient opto-electronic devices in the ultraviolet (UV) region. We have succeeded in growing the ZnO micro/nanosphere by a simple laser ablation in the air, and therefore we have obtained UV lasing from the sphere under optical pumping. Recently, large size of several 10 micrometer ZnO microspheres were grown using Nd:YAG laser without Q-switching, and ZnO microsphere/p-GaN heterojunction were fabricated to obtain the electroluminescence (EL) from the microsphere by electrical pumping. Room-temperature EL in near-UV region with peak wavelength of 400 nm is observed under forward bias.

  6. Fabrication and thermal oxidation of ZnO nano fibers prepared via electro spinning technique

    International Nuclear Information System (INIS)

    Baek, Jeongha; Park, Juyun; Kim, Don; Kang, Yongcheol; Koh, Sungwi; Kang, Jisoo

    2012-01-01

    Materials on the scale of nano scale have widely been used as research topics because of their interesting characteristics and aspects they bring into the field. Out of the many metal oxides, zinc oxide (ZnO) was chosen to be fabricated as nano fibers using the electro spinning method for potential uses of solar cells and sensors. After ZnO nano fibers were obtained, calcination temperature effects on the ZnO nano fibers were studied and reported here. The results of scanning electron microscopy (SEM) revealed that the aggregation of the ZnO nano fibers progressed by calcination. X-ray diffraction (XRD) study showed the hcp ZnO structure was enhanced by calcination at 873 and 1173 K. Transmission electron microscopy (TEM) confirmed the crystallinity of the calcined ZnO nano fibers. X-ray photoelectron spectroscopy (XPS) verified the thermal oxidation of Zn species by calcination in the nano fibers. These techniques have helped US deduce the facts that the diameter of ZnO increases as the calcination temperature was raised; the process of calcination affects the crystallinity of ZnO nano fibers, and the thermal oxidation of Zn species was observed as the calcination temperature was raised

  7. Characterisation of irradiation-induced defects in ZnO single crystals

    International Nuclear Information System (INIS)

    Prochazka, I; Cizek, J; Lukac, F; Melikhova, O; Valenta, J; Havranek, V; Anwand, W; Skuratov, V A; Strukova, T S

    2016-01-01

    Positron annihilation spectroscopy (PAS) combined with optical methods was employed for characterisation of defects in the hydrothermally grown ZnO single crystals irradiated by 167 MeV Xe 26+ ions to fluences ranged from 3×10 12 to 1×10 14 cm -2 . The positron lifetime (LT), Doppler broadening as well as slow-positron implantation spectroscopy (SPIS) techniques were involved. The ab-initio theoretical calculations were utilised for interpretation of LT results. The optical transmission and photoluminescence measurements were conducted, too. The virgin ZnO crystal exhibited a single component LT spectrum with a lifetime of 182 ps which is attributed to saturated positron trapping in Zn vacancies associated with hydrogen atoms unintentionally introduced into the crystal during the crystal growth. The Xe ion irradiated ZnO crystals have shown an additional component with a longer lifetime of ≈ 360 ps which comes from irradiation-induced larger defects equivalent in size to clusters of ≈10 to 12 vacancies. The concentrations of these clusters were estimated on the basis of combined LT and SPIS data. The PAS data were correlated with irradiation induced changes seen in the optical spectroscopy experiments. (paper)

  8. Characterisation of irradiation-induced defects in ZnO single crystals

    Science.gov (United States)

    Prochazka, I.; Cizek, J.; Lukac, F.; Melikhova, O.; Valenta, J.; Havranek, V.; Anwand, W.; Skuratov, V. A.; Strukova, T. S.

    2016-01-01

    Positron annihilation spectroscopy (PAS) combined with optical methods was employed for characterisation of defects in the hydrothermally grown ZnO single crystals irradiated by 167 MeV Xe26+ ions to fluences ranged from 3×1012 to 1×1014 cm-2. The positron lifetime (LT), Doppler broadening as well as slow-positron implantation spectroscopy (SPIS) techniques were involved. The ab-initio theoretical calculations were utilised for interpretation of LT results. The optical transmission and photoluminescence measurements were conducted, too. The virgin ZnO crystal exhibited a single component LT spectrum with a lifetime of 182 ps which is attributed to saturated positron trapping in Zn vacancies associated with hydrogen atoms unintentionally introduced into the crystal during the crystal growth. The Xe ion irradiated ZnO crystals have shown an additional component with a longer lifetime of ≈ 360 ps which comes from irradiation-induced larger defects equivalent in size to clusters of ≈10 to 12 vacancies. The concentrations of these clusters were estimated on the basis of combined LT and SPIS data. The PAS data were correlated with irradiation induced changes seen in the optical spectroscopy experiments.

  9. Photoluminescence and positron annihilation spectroscopic investigation on a H+ irradiated ZnO single crystal

    Science.gov (United States)

    Sarkar, A.; Chakrabarti, Mahuya; Sanyal, D.; Bhowmick, D.; Dechoudhury, S.; Chakrabarti, A.; Rakshit, Tamita; Ray, S. K.

    2012-08-01

    Low temperature photoluminescence and room temperature positron annihilation spectroscopy have been employed to investigate the defects incorporated by 6 MeV H+ ions in a hydrothermally grown ZnO single crystal. Prior to irradiation, the emission from donor bound excitons is at 3.378 eV (10 K). The irradiation creates an intense and narrow emission at 3.368 eV (10 K). The intensity of this peak is nearly four times that of the dominant near band edge peak of the pristine crystal. The characteristic features of the 3.368 eV emission indicate its origin as a ‘hydrogen at oxygen vacancy’ type defect. The positron annihilation lifetime measurement reveals a single component lifetime spectrum for both the unirradiated (164 ± 1 ps) and irradiated crystal (175 ± 1 ps). It reflects the fact that the positron lifetime and intensity of the new irradiation driven defect species are a little higher compared to those in the unirradiated crystal. However, the estimated defect concentration, even considering the high dynamic defect annihilation rate in ZnO, comes out to be ˜4 × 1017 cm-3 (using SRIM software). This is a very high defect concentration compared to the defect sensitivity of positron annihilation spectroscopy. A probable reason is the partial filling of the incorporated vacancies (positron traps), which in ZnO are zinc vacancies. The positron lifetime of ˜175 ps (in irradiated ZnO) is consistent with recent theoretical calculations for partially hydrogen-filled zinc vacancies in ZnO. Passivation of oxygen vacancies by hydrogen is also reflected in the photoluminescence results. A possible reason for such vacancy filling (at both Zn and O sites) due to irradiation has also been discussed.

  10. Photoluminescence and positron annihilation spectroscopic investigation on a H+ irradiated ZnO single crystal

    International Nuclear Information System (INIS)

    Sarkar, A; Chakrabarti, Mahuya; Sanyal, D; Bhowmick, D; Dechoudhury, S; Chakrabarti, A; Rakshit, Tamita; Ray, S K

    2012-01-01

    Low temperature photoluminescence and room temperature positron annihilation spectroscopy have been employed to investigate the defects incorporated by 6 MeV H + ions in a hydrothermally grown ZnO single crystal. Prior to irradiation, the emission from donor bound excitons is at 3.378 eV (10 K). The irradiation creates an intense and narrow emission at 3.368 eV (10 K). The intensity of this peak is nearly four times that of the dominant near band edge peak of the pristine crystal. The characteristic features of the 3.368 eV emission indicate its origin as a ‘hydrogen at oxygen vacancy’ type defect. The positron annihilation lifetime measurement reveals a single component lifetime spectrum for both the unirradiated (164 ± 1 ps) and irradiated crystal (175 ± 1 ps). It reflects the fact that the positron lifetime and intensity of the new irradiation driven defect species are a little higher compared to those in the unirradiated crystal. However, the estimated defect concentration, even considering the high dynamic defect annihilation rate in ZnO, comes out to be ∼4 × 10 17 cm -3 (using SRIM software). This is a very high defect concentration compared to the defect sensitivity of positron annihilation spectroscopy. A probable reason is the partial filling of the incorporated vacancies (positron traps), which in ZnO are zinc vacancies. The positron lifetime of ∼175 ps (in irradiated ZnO) is consistent with recent theoretical calculations for partially hydrogen-filled zinc vacancies in ZnO. Passivation of oxygen vacancies by hydrogen is also reflected in the photoluminescence results. A possible reason for such vacancy filling (at both Zn and O sites) due to irradiation has also been discussed. (paper)

  11. Photoluminescence and positron annihilation spectroscopic investigation on a H(+) irradiated ZnO single crystal.

    Science.gov (United States)

    Sarkar, A; Chakrabarti, Mahuya; Sanyal, D; Bhowmick, D; Dechoudhury, S; Chakrabarti, A; Rakshit, Tamita; Ray, S K

    2012-08-15

    Low temperature photoluminescence and room temperature positron annihilation spectroscopy have been employed to investigate the defects incorporated by 6 MeV H(+) ions in a hydrothermally grown ZnO single crystal. Prior to irradiation, the emission from donor bound excitons is at 3.378 eV (10 K). The irradiation creates an intense and narrow emission at 3.368 eV (10 K). The intensity of this peak is nearly four times that of the dominant near band edge peak of the pristine crystal. The characteristic features of the 3.368 eV emission indicate its origin as a 'hydrogen at oxygen vacancy' type defect. The positron annihilation lifetime measurement reveals a single component lifetime spectrum for both the unirradiated (164 ± 1 ps) and irradiated crystal (175 ± 1 ps). It reflects the fact that the positron lifetime and intensity of the new irradiation driven defect species are a little higher compared to those in the unirradiated crystal. However, the estimated defect concentration, even considering the high dynamic defect annihilation rate in ZnO, comes out to be ∼4 × 10(17) cm(-3) (using SRIM software). This is a very high defect concentration compared to the defect sensitivity of positron annihilation spectroscopy. A probable reason is the partial filling of the incorporated vacancies (positron traps), which in ZnO are zinc vacancies. The positron lifetime of ∼175 ps (in irradiated ZnO) is consistent with recent theoretical calculations for partially hydrogen-filled zinc vacancies in ZnO. Passivation of oxygen vacancies by hydrogen is also reflected in the photoluminescence results. A possible reason for such vacancy filling (at both Zn and O sites) due to irradiation has also been discussed.

  12. Zn nanoparticle formation in FIB irradiated single crystal ZnO

    Science.gov (United States)

    Pea, M.; Barucca, G.; Notargiacomo, A.; Di Gaspare, L.; Mussi, V.

    2018-03-01

    We report on the formation of Zn nanoparticles induced by Ga+ focused ion beam on single crystal ZnO. The irradiated materials have been studied as a function of the ion dose by means of atomic force microscopy, scanning electron microscopy, Raman spectroscopy and transmission electron microscopy, evidencing the presence of Zn nanoparticles with size of the order of 5-30 nm. The nanoparticles are found to be embedded in a shallow amorphous ZnO matrix few tens of nanometers thick. Results reveal that ion beam induced Zn clustering occurs producing crystalline particles with the same hexagonal lattice and orientation of the substrate, and could explain the alteration of optical and electrical properties found for FIB fabricated and processed ZnO based devices.

  13. The investigation of Ce doped ZnO crystal: The electronic, optical and magnetic properties

    Science.gov (United States)

    Wen, Jun-Qing; Zhang, Jian-Min; Qiu, Ze-Gang; Yang, Xu; Li, Zhi-Qin

    2018-04-01

    The electronic, optical and magnetic properties of Ce doped ZnO crystal have been studied by using first principles method. The research of formation energies show that Ce doped ZnO is energetically stable, and the formation energies reduce from 6.25% to 12.5% for Ce molar percentage. The energy band is still direct band gap after Ce doped, and band gap increases with the increase of Cesbnd Ce distance. The Fermi level moves upward into conduction band and the DOS moves to lower energy with the increase of Ce concentration, which showing the properties of n-type semiconductor. The calculated optical properties imply that Ce doped causes a red-shift of absorption peaks, and enhances the absorption of the visible light. The transition from ferromagnetic to antiferromagnetic has been found in Ce doped ZnO.

  14. Coherent diffractive imaging of solid state reactions in zinc oxide crystals

    Science.gov (United States)

    Leake, Steven J.; Harder, Ross; Robinson, Ian K.

    2011-11-01

    We investigated the doping of zinc oxide (ZnO) microcrystals with iron and nickel via in situ coherent x-ray diffractive imaging (CXDI) in vacuum. Evaporated thin metal films were deposited onto the ZnO microcrystals. A single crystal was selected and tracked through annealing cycles. A solid state reaction was observed in both iron and nickel experiments using CXDI. A combination of the shrink wrap and guided hybrid-input-output phasing methods were applied to retrieve the electron density. The resolution was 33 nm (half order) determined via the phase retrieval transfer function. The resulting images are nevertheless sensitive to sub-angstrom displacements. The exterior of the microcrystal was found to degrade dramatically. The annealing of ZnO microcrystals coated with metal thin films proved an unsuitable doping method. In addition the observed defect structure of one crystal was attributed to the presence of an array of defects and was found to change upon annealing.

  15. Nanosecond X-ray detector based on high resistivity ZnO single crystal semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Xiaolong; He, Yongning, E-mail: yongning@mail.xjtu.edu.cn; Peng, Wenbo; Huang, Zhiyong; Qi, Xiaomeng; Pan, Zijian; Zhang, Wenting [School of Electronic and Information Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Chen, Liang; Liu, Jinliang; Zhang, Zhongbing; Ouyang, Xiaoping [Radiation Detection Research Center, Northwest Institute of Nuclear Technology, Xi' an 710024 (China)

    2016-04-25

    The pulse radiation detectors are sorely needed in the fields of nuclear reaction monitoring, material analysis, astronomy study, spacecraft navigation, and space communication. In this work, we demonstrate a nanosecond X-ray detector based on ZnO single crystal semiconductor, which emerges as a promising compound-semiconductor radiation detection material for its high radiation tolerance and advanced large-size bulk crystal growth technique. The resistivity of the ZnO single crystal is as high as 10{sup 13} Ω cm due to the compensation of the donor defects (V{sub O}) and acceptor defects (V{sub Zn} and O{sub i}) after high temperature annealing in oxygen. The photoconductive X-ray detector was fabricated using the high resistivity ZnO single crystal. The rise time and fall time of the detector to a 10 ps pulse electron beam are 0.8 ns and 3.3 ns, respectively, indicating great potential for ultrafast X-ray detection applications.

  16. Origin of green luminescence in hydrothermally grown ZnO single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Čížek, J., E-mail: jakub.cizek@mff.cuni.cz; Hruška, P.; Melikhova, O.; Procházka, I. [Department of Low-Temperature Physics, Charles University in Prague, V Holešovičkách 2, CZ-180 00, Prague 8 (Czech Republic); Valenta, J. [Department of Chemical Physics and Optics, Charles University in Prague, Ke Karlovu 3, CZ-121 16, Prague 2 (Czech Republic); Novotný, M.; Bulíř, J. [Academy of Science of the Czech Republic, Institute of Physics, Na Slovance 2, CZ-182 21 Praha 8 (Czech Republic)

    2015-06-22

    Combining photoluminescence and positron annihilation studies of hydrothermally grown ZnO crystals with stoichiometry varied by controlled annealing enabled us to clarify the origin of green luminescence. It was found that green luminescence in ZnO has multiple origins and consists of a band at 2.3(1) eV due to recombination of electrons of the conduction band by zinc vacancy acceptors coupled with hydrogen and a band at 2.47(2) eV related to oxygen vacancies. The as-grown ZnO crystals contain zinc vacancies associated with hydrogen and exhibit a green luminescence at 2.3(1) eV. Annealing in Zn vapor removed zinc vacancies and introduced oxygen vacancies. This led to disappearance of the green luminescence band at 2.3(1) eV and appearance of a green emission at higher energy of 2.47(2) eV. Moreover, the color of the crystal was changed from colorless to dark red. In contrast, annealing of the as-grown crystal in Cd vapor did not remove zinc vacancies and did not cause any significant change of green luminescence nor change in coloration.

  17. Origin of green luminescence in hydrothermally grown ZnO single crystals

    International Nuclear Information System (INIS)

    Čížek, J.; Hruška, P.; Melikhova, O.; Procházka, I.; Valenta, J.; Novotný, M.; Bulíř, J.

    2015-01-01

    Combining photoluminescence and positron annihilation studies of hydrothermally grown ZnO crystals with stoichiometry varied by controlled annealing enabled us to clarify the origin of green luminescence. It was found that green luminescence in ZnO has multiple origins and consists of a band at 2.3(1) eV due to recombination of electrons of the conduction band by zinc vacancy acceptors coupled with hydrogen and a band at 2.47(2) eV related to oxygen vacancies. The as-grown ZnO crystals contain zinc vacancies associated with hydrogen and exhibit a green luminescence at 2.3(1) eV. Annealing in Zn vapor removed zinc vacancies and introduced oxygen vacancies. This led to disappearance of the green luminescence band at 2.3(1) eV and appearance of a green emission at higher energy of 2.47(2) eV. Moreover, the color of the crystal was changed from colorless to dark red. In contrast, annealing of the as-grown crystal in Cd vapor did not remove zinc vacancies and did not cause any significant change of green luminescence nor change in coloration

  18. Origin of green luminescence in hydrothermally grown ZnO single crystals

    Science.gov (United States)

    Čížek, J.; Valenta, J.; Hruška, P.; Melikhova, O.; Procházka, I.; Novotný, M.; Bulíř, J.

    2015-06-01

    Combining photoluminescence and positron annihilation studies of hydrothermally grown ZnO crystals with stoichiometry varied by controlled annealing enabled us to clarify the origin of green luminescence. It was found that green luminescence in ZnO has multiple origins and consists of a band at 2.3(1) eV due to recombination of electrons of the conduction band by zinc vacancy acceptors coupled with hydrogen and a band at 2.47(2) eV related to oxygen vacancies. The as-grown ZnO crystals contain zinc vacancies associated with hydrogen and exhibit a green luminescence at 2.3(1) eV. Annealing in Zn vapor removed zinc vacancies and introduced oxygen vacancies. This led to disappearance of the green luminescence band at 2.3(1) eV and appearance of a green emission at higher energy of 2.47(2) eV. Moreover, the color of the crystal was changed from colorless to dark red. In contrast, annealing of the as-grown crystal in Cd vapor did not remove zinc vacancies and did not cause any significant change of green luminescence nor change in coloration.

  19. Neutron monochromators of BeO, MgO and ZnO single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Adib, M.; Habib, N. [Reactor Physics Department, NRC, AEAE, Cairo (Egypt); Bashter, I.I. [Physics Department, Faculty of Science, Zagazig University (Egypt); Morcos, H.N.; El-Mesiry, M.S. [Reactor Physics Department, NRC, AEAE, Cairo (Egypt); Mansy, M.S., E-mail: mohamedmansy_np@yahoo.com [Physics Department, Faculty of Science, Zagazig University (Egypt)

    2014-05-21

    The monochromatic features of BeO, MgO and ZnO single crystals are discussed in terms of orientation, mosaic spread, and thickness within the wavelength band from 0.05 up to 0.5 nm. A computer program MONO, written in “FORTRAN”, has been developed to carry out the required calculations. Calculation shows that a 5 mm thick MgO single crystal cut along its (2 0 0) plane having mosaic spread of 0.5° FWHM has the optimum parameters when it is used as a neutron monochromator. Moreover, at wavelengths shorter than 0.24 nm the reflected monochromatic neutrons are almost free from the higher order ones. The same features are seen with BeO (0 0 2) with less reflectivity than that of the former. Also, ZnO cut along its (0 0 2) plane is preferred over the others only at wavelengths longer than 0.20 nm. When the selected monochromatic wavelength is longer than 0.24 nm, the neutron intensities of higher orders from a thermal reactor flux are higher than those of the first-order one. For a cold reactor flux, the first order of BeO and MgO single crystals is free from the higher orders up to 0.4 nm, and ZnO at wavelengths up to 0.5 nm. - Highlights: • Monochromatic features of BeO, MgO and ZnO single crystals. • Calculations of neutron reflectivity using a computer program MONO. • Optimum mosaic spread, thickness and cutting plane of single crystals.

  20. Controllable synthesis of mesoporous multi-shelled ZnO microspheres as efficient photocatalysts for NO oxidation

    Science.gov (United States)

    Chen, Xiaolang; Zhang, Huiqiang; Zhang, Dieqing; Miao, Yingchun; Li, Guisheng

    2018-03-01

    The successful application of hierarchically porous structure in environmental treatment has provided new insights for solving environmental problems. Hierarchically structured semiconductor materials were considered as promising photocatalysts for NO oxidation in gas phase. Multi-shelled ZnO microspheres (MMSZ) were controllably shaped with hierarchically porous structures via a facile hydrothermal route using amino acid (N-Acetyl-D-Proline) as template and post-calcination treatment. Symmetric Ostwald ripening was used to explain the morphological evolution of hierarchical nanostructure. MMSZ was proved highly efficient for oxidizing NO (400 ppb) in gas phase under UV light irradiation with a much higher photocatalytic removal rate (77.3%) than that of the as-obtained ZnO crystals with other hierachically porous structures, owing to its higher photocurrent intensity. Such greatly enhanced photocatalytic activity can be assigned to the enhanced crystallinity of ZnO, mesopores and unique multi-shelled structure. Enhanced crystallinity promotes photogenerated charges under light irradiation. Mesoporous porosity can ensure enough light scattering between the shells. Multi-shelled structure endows ZnO with higher specific surface area and high frequency of multiple light reflection, resulting in more exposed active sites, higher light utilization efficiency, and fast separation efficiency of photogenerated charge carriers. The experimental results demonstrated that the photogenerated holes (h+) are the main active species. Hierarchically structured ZnO is not only contributed to directly use solar energy to solving various problems caused by atmospheric pollution, but also has potential applications in energy converse and storage including solar cells, lithium batteries, water-splitting, etc.

  1. Efficiency of Advanced H2O2/ZnO Oxidation Process in Ceftriaxone Antibiotic Removal from Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    Maryam Noroozi cholcheh

    2017-11-01

    Full Text Available A major concern about pharmaceutical pollution is the presence of antibiotics in water resources through their release into sewers where they cause bacterial resistance and enhanced drug-resistance in human-borne pathogens and growing microbial populations in the environment. The objective of this study was to investigate the efficiency of  the advanced H2O2/ZnO oxidation process in removing ceftriaxone from aqueous solutions. For this purpose, an experimental study was conducted in which the SEM, XRD, and TEM techniques were employed to determine the size of Zinc oxide nano-particles. Additionally, the oxidation process parameters of pH (3-11, molar ratio of H2O2/ZnO (1.5-3, initial concentration of ceftriaxone (5–15 mg/L, and contact time (30-90 min were investigated. Teh data thus obntained were subjected top statistical analysis using the SPSS (ANOVA test. XRD results revealeda hexagonal crystal structure for the nano-ZnO. TEM images confirmed the spherical shape of the nanoparticles. Finally, SEM images revealed that the Zn nanoparticles used in this study were less than 30 nanometers in diameter. Based on the results, an optimum pH of 11, a contact time of 90 minutes, and a H2O2/ZnO molar ratio equal to 1.5 were the optimum conditions to achieve a ceftriaxone removal efficiency of 92%. The advance H2O2/ZnO oxidation process may thus be claimed to be highly capable of removing ceftriaxone from aqueous solutions.

  2. Origin of the defects-induced ferromagnetism in un-doped ZnO single crystals

    Science.gov (United States)

    Zhan, Peng; Xie, Zheng; Li, Zhengcao; Wang, Weipeng; Zhang, Zhengjun; Li, Zhuoxin; Cheng, Guodong; Zhang, Peng; Wang, Baoyi; Cao, Xingzhong

    2013-02-01

    We clarified, in this Letter, that in un-doped ZnO single crystals after thermal annealing in flowing argon, the defects-induced room-temperature ferromagnetism was originated from the surface defects and specifically, from singly occupied oxygen vacancies denoted as F+, by the optical and electrical properties measurements as well as positron annihilation analysis. In addition, a positive linear relationship was observed between the ferromagnetism and the F+ concentration, which is in support with the above clarification.

  3. Neutron monochromators of BeO, MgO and ZnO single crystals

    Science.gov (United States)

    Adib, M.; Habib, N.; Bashter, I. I.; Morcos, H. N.; El-Mesiry, M. S.; Mansy, M. S.

    2014-05-01

    The monochromatic features of BeO, MgO and ZnO single crystals are discussed in terms of orientation, mosaic spread, and thickness within the wavelength band from 0.05 up to 0.5 nm. A computer program MONO, written in “FORTRAN”, has been developed to carry out the required calculations. Calculation shows that a 5 mm thick MgO single crystal cut along its (2 0 0) plane having mosaic spread of 0.5° FWHM has the optimum parameters when it is used as a neutron monochromator. Moreover, at wavelengths shorter than 0.24 nm the reflected monochromatic neutrons are almost free from the higher order ones. The same features are seen with BeO (0 0 2) with less reflectivity than that of the former. Also, ZnO cut along its (0 0 2) plane is preferred over the others only at wavelengths longer than 0.20 nm. When the selected monochromatic wavelength is longer than 0.24 nm, the neutron intensities of higher orders from a thermal reactor flux are higher than those of the first-order one. For a cold reactor flux, the first order of BeO and MgO single crystals is free from the higher orders up to 0.4 nm, and ZnO at wavelengths up to 0.5 nm.

  4. Optical and Magnetic Resonance Studies of Na-Diffused ZnO Bulk Single Crystals

    Science.gov (United States)

    Glaser, E. R.; Garces, N. Y.; Parmar, N. S.; Lynn, K. G.

    2013-03-01

    Photoluminescence (PL) and optically-detected magnetic resonance (ODMR) at 24 GHz were performed on bulk ZnO crystals after diffusion of Na impurities that were explored as an alternate doping source for p-type conductivity. PL at 2K revealed strong bandedge excitonic recombination at 3.361 eV and a broad ``orange'' PL band at 2.17 eV with FWHM of ~0.5 eV. This ``orange'' emission is very similar to that reported previously[1] from thermoluminescence measurements of intentionally Na-doped bulk ZnO and, thus, strongly suggests the incorporation and activation of the Na-diffused impurities. ODMR performed on this ``orange'' PL revealed two signals. The first was a sharp feature with g-value of ~1.96 and is a well-known ``fingerprint'' of shallow donors in ZnO. The second signal consisted of a pair of lines with an intensity ratio of ~3:1 and with g-tensors (g∥,g⊥ ~2.008-2.029) very similar to ESR signals attributed previously[2] to holes bound to Na impurities located at the axial and non-axial Zn host lattice sites in Na-doped ZnO. Thus, the ``orange'' PL can be tentatively assigned to radiative recombination between residual shallow donors and deep Na-related hole traps.

  5. Origins of low resistivity in Al ion-implanted ZnO bulk single crystals

    Science.gov (United States)

    Oga, T.; Izawa, Y.; Kuriyama, K.; Kushida, K.; Kinomura, A.

    2011-06-01

    The origins of low resistivity in Al ion-implanted ZnO bulk single crystals are studied by combining Rutherford backscattering spectroscopy (RBS), nuclear reaction analysis (NRA), photoluminescence (PL), and Van der Pauw methods. The Al-ion implantation (peak concentration: 2.6 × 1020cm-3) into ZnO is performed using a multiple-step energy. The resistivity decreases from ˜104 Ω cm for un-implanted ZnO to 1.4 × 10-1 Ω cm for as-implanted, and reaches 6.0 × 10-4 Ω cm for samples annealed at 1000 °C. RBS and NRA measurements for as-implanted ZnO suggest the existence of the lattice displacement of Zn (Zni) and O (Oi), respectively. After annealing at 1000 °C, the Zni related defects remain and the Oi related defects disappear. The origin of the low resistivity in the as-implanted sample is attributed to the Zni (˜30 meV [Look et al., Phys. Rev. Lett. 82, 2552 (1999)]). In contrast, the origin of the low resistivity in the sample annealed at 1000 °C is assigned to both of the Zni related defects and the electrically activated Al donor. A new PL emission appears at around 3.32 eV after annealing at 1000 °C, suggesting electrically activated Al donors.

  6. High-resolution photoluminescence spectroscopy of Sn-doped ZnO single crystals

    International Nuclear Information System (INIS)

    Kumar, E. Senthil; Mohammadbeigi, F.; Boatner, L.A.; Watkins, S.P.

    2016-01-01

    Group IV donors in ZnO are poorly understood, despite evidence that they are effective n-type dopants. Here we present high-resolution photoluminescence (PL) spectroscopy studies of unintentionally doped and Sn-doped ZnO single crystals grown by the chemical vapor transport method. Doped samples showed greatly increased emission from the I 10 bound exciton transition that was recently proven to be related to the incorporation of Sn impurities based on radio-isotope studies. The PL linewidths are exceptionally sharp for these samples, enabling a clear identification of several donor species. Temperature-dependent PL measurements of the I 10 line emission energy and intensity dependence reveal a behavior that is similar to other shallow donors in ZnO. Ionized donor bound-exciton and two-electron satellite transitions of the I 10 transition are unambiguously identified and yield a donor binding energy of 71 meV. In contrast to recent reports of Ge-related donors in ZnO, the spectroscopic binding energy for the Sn-related donor bound exciton follows a linear relationship with donor binding energy (Haynes rule) similar to recently observed carbon related donors, and confirming the shallow nature of this defect center, which was recently attributed to a Sn Zn double donor compensated by an unknown single acceptor.

  7. Photocatalytic Activity and Stability of Porous Polycrystalline ZnO Thin-Films Grown via a Two-Step Thermal Oxidation Process

    Directory of Open Access Journals (Sweden)

    James C. Moore

    2014-08-01

    Full Text Available The photocatalytic activity and stability of thin, polycrystalline ZnO films was studied. The oxidative degradation of organic compounds at the ZnO surface results from the ultraviolet (UV photo-induced creation of highly oxidizing holes and reducing electrons, which combine with surface water to form hydroxyl radicals and reactive oxygen species. Therefore, the efficiency of the electron-hole pair formation is of critical importance for self-cleaning and antimicrobial applications with these metal-oxide catalyst systems. In this study, ZnO thin films were fabricated on sapphire substrates via direct current sputter deposition of Zn-metal films followed by thermal oxidation at several annealing temperatures (300–1200 °C. Due to the ease with which they can be recovered, stabilized films are preferable to nanoparticles or colloidal suspensions for some applications. Characterization of the resulting ZnO thin films through atomic force microscopy and photoluminescence indicated that decreasing annealing temperature leads to smaller crystal grain size and increased UV excitonic emission. The photocatalytic activities were characterized by UV-visible absorption measurements of Rhodamine B dye concentrations. The films oxidized at lower annealing temperatures exhibited higher photocatalytic activity, which is attributed to the increased optical quality. Photocatalytic activity was also found to depend on film thickness, with lower activity observed for thinner films. Decreasing activity with use was found to be the result of decreasing film thickness due to surface etching.

  8. Enhanced photocatalytic performance of ZnO nanostructures by electrochemical hybridization with graphene oxide

    Science.gov (United States)

    Pruna, A.; Wu, Z.; Zapien, J. A.; Li, Y. Y.; Ruotolo, A.

    2018-05-01

    Synthesis of zinc oxide (ZnO) nanostructures is reported by electrochemical deposition from an aqueous electrolyte in presence of graphene oxide (GO) with varying oxidation degree. The properties of hybrids were investigated by scanning electron microscopy, X-ray diffraction, Raman, Fourier-Transform Infrared and X-ray photoelectron spectroscopy techniques and photocatalytic measurements. The results indicated the electrodeposition of ZnO in presence of GO with increased oxygen content led to marked differences in the morphology while Raman measurements indicated an increased defect level both in the ZnO and the electrochemically reduced GO (ErGO) within the hybrids. The decrease in C/O atomic ratio of GO (from 0.79 to 0.71) employed for the electrodeposition of ZnO resulted in an increase in photocatalytic efficiency for methylene blue degradation under UV irradiation from 4-folds to 10-folds with respect to non-hybridized ZnO. The observed synergetic effect of cathodic deposition potential and oxygen content in GO towards improving the photocatalytic activity of immobilized ZnO is expected to contribute to further development of more effective deposition approaches for the preparation of high performance hybrid nanostructures.

  9. Characterization of Zinc Oxide (ZnO) piezoelectric properties for Surface Acoustic Wave (SAW) device

    Science.gov (United States)

    Rosydi Zakaria, Mohd; Johari, Shazlina; Hafiz Ismail, Mohd; Hashim, Uda

    2017-11-01

    In fabricating Surface Acoustic Wave (SAW) biosensors device, the substrate is one of important factors that affected to performance device. there are many types of piezoelectric substrate in the markets and the cheapest is zinc Oxide substrate. Zinc Oxide (ZnO) with its unique properties can be used as piezoelectric substrate along with SAW devices for detection of DNA in this research. In this project, ZnO thin film is deposited onto silicon oxide substrate using electron beam evaporation (E-beam) and Sol-Gel technique. Different material structure is used to compare the roughness and best piezoelectric substrate of ZnO thin film. Two different structures of ZnO target which are pellet and granular are used for e-beam deposition and one sol-gel liquid were synthesize and compared. Parameter for thickness of ZnO e-beam deposition is fixed to a 0.1kÅ for both materials structure and sol-gel was coat using spin coat technique. After the process is done, samples are annealed at temperature of 500°C for 2 hours. The structural properties of effect of post annealing using different material structure of ZnO are studied using Atomic Force Microscopic (AFM) for surface morphology and X-ray Diffraction (XRD) for phase structure.

  10. The formation of tungsten doped Al{sub 2}O{sub 3}/ZnO coatings on aluminum by plasma electrolytic oxidation and their application in photocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    Stojadinović, Stevan, E-mail: sstevan@ff.bg.ac.rs [University of Belgrade, Faculty of Physics, Studentski trg 12-16, 11000 Belgrade (Serbia); Vasilić, Rastko [University of Belgrade, Faculty of Physics, Studentski trg 12-16, 11000 Belgrade (Serbia); Radić, Nenad [University of Belgrade, Institute of Chemistry, Technology and Metallurgy, Department of Catalysis and Chemical Engineering, Njegoševa 12, 11000 Belgrade (Serbia); Tadić, Nenad [University of Belgrade, Faculty of Physics, Studentski trg 12-16, 11000 Belgrade (Serbia); Stefanov, Plamen [Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Block 11, 1113 Sofia (Bulgaria); Grbić, Boško [University of Belgrade, Institute of Chemistry, Technology and Metallurgy, Department of Catalysis and Chemical Engineering, Njegoševa 12, 11000 Belgrade (Serbia)

    2016-07-30

    Highlights: • Tungsten doped Al{sub 2}O{sub 3}/ZnO coatings are formed by plasma electrolytic oxidation (PEO). • Coatings are mainly composed of alpha alumina, ZnO and metallic tungsten. • Photocatalytic activity of doped Al{sub 2}O{sub 3}/ZnO coatings is higher than of undoped ones. • The increase of photoluminescence corresponds to decrease of photocatalytic activity. • Tungsten acts as a charge trap to reduce the recombination rate of electron/hole pairs. - Abstract: Tungsten doped Al{sub 2}O{sub 3}/ZnO coatings are formed by plasma electrolytic oxidation of aluminum substrate in supporting electrolyte (0.1 M boric acid + 0.05 M borax + 2 g/L ZnO) with addition of different concentrations of Na{sub 2}WO{sub 4}·2H{sub 2}O. The morphology, crystal structure, chemical composition, and light absorption characteristics of formed surface coatings are investigated. The X-ray diffraction and X-ray photoelectron spectroscopy results indicate that formed surface coatings consist of alpha and gamma phase of Al{sub 2}O{sub 3}, ZnO, metallic tungsten and WO{sub 3}. Obtained results showed that incorporated tungsten does not have any influence on the absorption spectra of Al{sub 2}O{sub 3}/ZnO coatings, which showed invariable band edge at about 385 nm. The photocatalytic activity of undoped and tungsten doped Al{sub 2}O{sub 3}/ZnO coatings is estimated by the photodegradation of methyl orange. The photocatalytic activity of tungsten doped Al{sub 2}O{sub 3}/ZnO coatings is higher thanof undoped Al{sub 2}O{sub 3}/ZnO coatings; the best photocatalytic activity is ascribed to coatings formed in supporting electrolyte with addition of 0.3 g/L Na{sub 2}WO{sub 4}·2H{sub 2}O. Tungsten in Al{sub 2}O{sub 3}/ZnO coatings acts as a charge trap, thus reducing the recombination rate of photogenerated electron-hole pairs. The results of PL measurements are in agreement with photocatalytic activity. Declining PL intensity corresponds to increasing photocatalytic activity of the

  11. The formation of tungsten doped Al_2O_3/ZnO coatings on aluminum by plasma electrolytic oxidation and their application in photocatalysis

    International Nuclear Information System (INIS)

    Stojadinović, Stevan; Vasilić, Rastko; Radić, Nenad; Tadić, Nenad; Stefanov, Plamen; Grbić, Boško

    2016-01-01

    Highlights: • Tungsten doped Al_2O_3/ZnO coatings are formed by plasma electrolytic oxidation (PEO). • Coatings are mainly composed of alpha alumina, ZnO and metallic tungsten. • Photocatalytic activity of doped Al_2O_3/ZnO coatings is higher than of undoped ones. • The increase of photoluminescence corresponds to decrease of photocatalytic activity. • Tungsten acts as a charge trap to reduce the recombination rate of electron/hole pairs. - Abstract: Tungsten doped Al_2O_3/ZnO coatings are formed by plasma electrolytic oxidation of aluminum substrate in supporting electrolyte (0.1 M boric acid + 0.05 M borax + 2 g/L ZnO) with addition of different concentrations of Na_2WO_4·2H_2O. The morphology, crystal structure, chemical composition, and light absorption characteristics of formed surface coatings are investigated. The X-ray diffraction and X-ray photoelectron spectroscopy results indicate that formed surface coatings consist of alpha and gamma phase of Al_2O_3, ZnO, metallic tungsten and WO_3. Obtained results showed that incorporated tungsten does not have any influence on the absorption spectra of Al_2O_3/ZnO coatings, which showed invariable band edge at about 385 nm. The photocatalytic activity of undoped and tungsten doped Al_2O_3/ZnO coatings is estimated by the photodegradation of methyl orange. The photocatalytic activity of tungsten doped Al_2O_3/ZnO coatings is higher thanof undoped Al_2O_3/ZnO coatings; the best photocatalytic activity is ascribed to coatings formed in supporting electrolyte with addition of 0.3 g/L Na_2WO_4·2H_2O. Tungsten in Al_2O_3/ZnO coatings acts as a charge trap, thus reducing the recombination rate of photogenerated electron-hole pairs. The results of PL measurements are in agreement with photocatalytic activity. Declining PL intensity corresponds to increasing photocatalytic activity of the coatings, indicating slower recombination of electron-hole pairs.

  12. Investigation on structural aspects of ZnO nano-crystal using radio-active ion beam and PAC

    Energy Technology Data Exchange (ETDEWEB)

    Ganguly, Bichitra Nandi, E-mail: bichitra.ganguly@saha.ac.in [Saha Institute of Nuclear Physics, Kolkata 700064 (India); Dutta, Sreetama; Roy, Soma [Saha Institute of Nuclear Physics, Kolkata 700064 (India); Röder, Jens [Physics Department, ISOLDE/CERN, Geneva (Switzerland); Physical Chemistry, RWTH-Aachen, Aachen (Germany); Johnston, Karl [Physics Department, ISOLDE/CERN, Geneva (Switzerland); Experimental Physics, University of the Saarland, Saarbrücken (Germany); Martin, Manfred [Physical Chemistry, RWTH-Aachen, Aachen (Germany)

    2015-11-01

    Nano-crystalline ZnO has been studied with perturbed angular correlation using {sup 111m}Cd, implanted at ISOLDE/CERN and X-ray diffraction using Rietveld analysis. The data show a gradual increase in the crystal size and stress for a sample annealed at 600 °C, and reaching nearly properties of standard ZnO with tempering at 1000 °C. The perturbed angular correlation data show a broad frequency distribution at low annealing temperatures and small particle sizes, whereas at high annealing temperature and larger crystal sizes, results similar to bulk ZnO have been obtained. The ZnO nano-crystalline samples were initially prepared through a wet chemical route, have been examined by Fourier Transform Infrared Spectroscopy (FT-IR) and chemical purity has been confirmed with Energy Dispersive X-ray (EDAX) analysis as well as Transmission Electron Microscopy (TEM).

  13. Composite structure of ZnO films coated with reduced graphene oxide: structural, electrical and electrochemical properties

    Science.gov (United States)

    Shuai, Weiqiang; Hu, Yuehui; Chen, Yichuan; Hu, Keyan; Zhang, Xiaohua; Zhu, Wenjun; Tong, Fan; Lao, Zixuan

    2018-02-01

    ZnO films coated with reduced graphene oxide (RGO-ZnO) were prepared by a simple chemical approach. The graphene oxide (GO) films transferred onto ZnO films by spin coating were reduced to RGO films by two steps (exposed to hydrazine vapor for 12 h and annealed at 600 °C). The crystal structures, electrical and photoluminescence properties of RGO-ZnO films on quartz substrates were systematically studied. The SEM images illustrated that RGO layers have successfully been coated on the ZnO films very tightly. The PL properties of RGO-ZnO were studied. PL spectra show two sharp peaks at 390 nm and a broad visible emission around 490 nm. The resistivity of RGO-ZnO films was measured by a Hall measurement system, RGO as nanofiller considerably decrease the resistivity of ZnO films. An electrode was fabricated, using RGO-ZnO films deposited on Si substrate as active materials, for super capacitor application. By comparison of different results, we conclude that the RGO-ZnO composite material couples possess the properties of super capacitor. Project supported by the National Natural Science Foundation of China (Nos. 61464005, 51562015), the Natural Science Foundation of Jiangxi Province (Nos. 20143ACB21004, 20151BAB212008, 20171BAB216015), the Jiangxi Province Foreign Cooperation Projects, China (No. 20151BDH80031), the Leader Training Object Project of Major Disciplines Academic and Technical of Jiangxi Province (No. 20123BCB22002), and the Key Technology R & D Program of the Jiangxi Provine of Science and Technology (No. 20171BBE50053).

  14. A flexible UV nanosensor based on reduced graphene oxide decorated ZnO nanostructures

    Science.gov (United States)

    Wang, Zhenxing; Zhan, Xueying; Wang, Yajun; Muhammad, Safdar; Huang, Ying; He, Jun

    2012-03-01

    A low-cost, compatible with flexible electronics, high performance UV sensor has been achieved from a reduced graphene oxide (RGO) decorated hydrangea-like ZnO film on a PDMS substrate. The hydrangea-like ZnO UV sensor has the best UV sensing performance among devices made of three kinds of ZnO nanostructures synthesized by a hydrothermal method, and demonstrated a dramatic enhancement in on/off ratio and photoresponse current by introducing an appropriate weight ratio of RGO. The on/off ratio of the 0.05% RGO/ZnO sensor increases almost one order of magnitude compared to that of a pristine hydrangea-like ZnO UV sensor. While for the 5% RGO decorated ZnO sensor, the photoresponse current reaches as high as ~1 μA and exceeds 700 times that of a ZnO UV sensor. These results indicate that RGO is an appropriate material to enhance the performance of ZnO nanostructure UV sensors based on its unique features, especially the high optical transparency and excellent electronic conductivity. Our findings will make RGO/ZnO nanohybrids extraordinarily promising in optoelectronics, flexible electronics and sensor applications.

  15. Enhancing the Antibacterial Activity of Light-Activated Surfaces Containing Crystal Violet and ZnO Nanoparticles: Investigation of Nanoparticle Size, Capping Ligand, and Dopants.

    Science.gov (United States)

    Sehmi, Sandeep K; Noimark, Sacha; Pike, Sebastian D; Bear, Joseph C; Peveler, William J; Williams, Charlotte K; Shaffer, Milo S P; Allan, Elaine; Parkin, Ivan P; MacRobert, Alexander J

    2016-09-30

    Healthcare-associated infections pose a serious risk for patients, staff, and visitors and are a severe burden on the National Health Service, costing at least £1 billion annually. Antimicrobial surfaces significantly contribute toward reducing the incidence of infections as they prevent bacterial adhesion and cause bacterial cell death. Using a simple, easily upscalable swell-encapsulation-shrink method, novel antimicrobial surfaces have been developed by incorporating metal oxide nanoparticles (NPs) and crystal violet (CV) dye into medical-grade polyurethane sheets. This study compares the bactericidal effects of polyurethane incorporating ZnO, Mg-doped ZnO, and MgO. All metal oxide NPs are well defined, with average diameters ranging from 2 to 18 nm. These materials demonstrate potent bactericidal activity when tested against clinically relevant bacteria such as Escherichia coli and Staphylococcus aureus . Additionally, these composites are tested against an epidemic strain of methicillin-resistant Staphylococcus aureus (MRSA) that is rife in hospitals throughout the UK. Furthermore, we have tested these materials using a low light intensity (∼500 lx), similar to that present in many clinical environments. The highest activity is achieved from polymer composites incorporating CV and ∼3 nm ZnO NPs, and the different performances of the metal oxides have been discussed.

  16. Identification of Zn-vacancy-hydrogen complexes in ZnO single crystals: A challenge to positron annihilation spectroscopy

    Science.gov (United States)

    Brauer, G.; Anwand, W.; Grambole, D.; Grenzer, J.; Skorupa, W.; Čížek, J.; Kuriplach, J.; Procházka, I.; Ling, C. C.; So, C. K.; Schulz, D.; Klimm, D.

    2009-03-01

    A systematic study of various, nominally undoped ZnO single crystals, either hydrothermally grown (HTG) or melt grown (MG), has been performed. The crystal quality has been assessed by x-ray diffraction, and a comprehensive estimation of the detailed impurity and hydrogen contents by inductively coupled plasma mass spectrometry and nuclear reaction analysis, respectively, has been made also. High precision positron lifetime experiments show that a single positron lifetime is observed in all crystals investigated, which clusters at 180-182 ps and 165-167 ps for HTG and MG crystals, respectively. Furthermore, hydrogen is detected in all crystals in a bound state with a high concentration (at least 0.3at.% ), whereas the concentrations of other impurities are very small. From ab initio calculations it is suggested that the existence of Zn-vacancy-hydrogen complexes is the most natural explanation for the given experimental facts at present. Furthermore, the distribution of H at a metal/ZnO interface of a MG crystal, and the H content of a HTG crystal upon annealing and time afterward has been monitored, as this is most probably related to the properties of electrical contacts made at ZnO and the instability in p -type conductivity observed at ZnO nanorods in literature. All experimental findings and presented theoretical considerations support the conclusion that various types of Zn-vacancy-hydrogen complexes exist in ZnO and need to be taken into account in future studies, especially for HTG materials.

  17. Intrinsic magnetism of a series of Co substituted ZnO single crystals

    International Nuclear Information System (INIS)

    Lv Peiwen; Huang Feng; Chu Wangsheng; Lin Zhang; Chen Dagui; Li Wei; Chen Dongliang; Wu Ziyu

    2008-01-01

    Magnetic properties of a series of well-substituted Zn 1-x Co x O (x = 0.018,0.036 and 0.05) single crystals were studied. A typical paramagnetic anisotropy property, which strengthens when x decreases, was found. A magnetization step was observed at 2 K when the magnetic field is parallel to the c axis, indicating that paramagnetic anisotropy is the origin of the strong crystal field effect on Co 2+ ions in ZnO lattices. The Co 2+ single-ion anisotropy parameter 2D is obtained as 7.5 K. The effective moment of Co 2+ takes the values 2.7 μ B , 1.82 μ B , 1.49 μ B when x = 0.018, 0.036 and 0.05, revealing that more antiferromagnetic coupling between Co 2+ ions arises in the perfect crystal when x increases

  18. Fabrication and characterization of Zinc Oxide (ZnO) nanoparticle by sol-gel method

    International Nuclear Information System (INIS)

    Siswanto; Akwalia, Putri Riski; Rochman, Nurul T.

    2017-01-01

    Currently, nanomaterial is an interestingfield of study. This is due to its chemical and physical properties that are superior to that of large-sized materials. One nanomaterial widely studied is zinc oxide (ZnO). In this study, a synthesis of ZnO nanoparticles made by Sol-Gel method was conducted. The process parameters used are variations in pH, in increasing order, of 7; 8; 9; 10; 11; and 12. There are two principal reactions to produce a compound oxide, namely hydrolysis and condensation. NaOH is an agent for the hydrolysis of (CH 3 COO) 2 Zn resultingin Zn (OH) 2 . Subsequently, condensation produces ZnO. Calcination was carried out at a temperature of 80 ° C for 1 hour. The ccharacterization of the samples showed that the condition of pH 12 produced the best sample with a size of 73.8 nm and ZnO percentage of 100%. Although pH 7 produced a particle size of 1.3 nm, the percentage of ZnO formed was only 42.9%. The calcination process was performed to remove CH 3 COONa. However, the process can lead to aggregation of ZnO particles to each other, which increases the particle size. (paper)

  19. Trapping effects and acoustoelectric current saturation in ZnO single crystals

    DEFF Research Database (Denmark)

    Mosekilde, Erik

    1970-01-01

    Measurements of current-voltage characteristics for ZnO single crystals at temperatures between 77 and 640 °K are reported. Because of the buildup of an intense acoustic flux, a strong current saturation sets in when the trap-controlled electron drift velocity is equal to the velocity of sound....... The temperature dependence of the saturated current is discussed in terms of a trapping model which includes nonlinear trapping effects. Our results indicate the presence of a shallow-donor level with an ionization energy of 50 meV and a deep-donor level approximately 230 meV below the conduction-band edge...

  20. Properties and local environment of p-type and photoluminescent rare earths implanted into ZnO single crystals

    CERN Document Server

    Rita, EMC; Wahl, U; Soares, JC

    This thesis presents an experimental study of the local environment of p-type and Rare- Earth dopants implanted in ZnO single-crystals (SCs). Various nuclear and bulk property techniques were combined in the following evaluations: Implantation damage annealing was evaluated in ZnO SCs implanted with Fe, Sr and Ca. P-type dopants Cu and Ag implanted ZnO SCs were studied revealing that the solubility of Cu in substituting Zn is considerably higher than that of Ag. These results are discussed within the scope of the ZnO p-type doping problematic with these elements. Experimental proofs of the As “anti-site” behavior in ZnO were for the first time attained, i.e., the majority of As atoms are substitutional at the Zn site (SZn), possibly surrounded by two Zn vacancies (VZn). This reinforces the theoretical prediction that As acts as an acceptor in ZnO via the AsZn-2VZn complex formation. The co-doping of ZnO SC with In (donor) and As (acceptor) was addressed. The most striking result is the possible In-As “p...

  1. Structural characterization of H plasma-doped ZnO single crystals by positron annihilation spectroscopies

    Energy Technology Data Exchange (ETDEWEB)

    Anwand, Wolfgang; Brauer, Gerhard; Cowan, Thomas E. [Institut fuer Strahlenphysik, Forschungszentrum Dresden-Rossendorf, P.O. Box 510 119, 01314 Dresden (Germany); Grambole, Dieter; Skorupa, Wolfgang [Institut fuer Ionenstrahlphysik und Materialforschung, Forschungszentrum Dresden-Rossendorf, P.O. Box 510 119, 01314 Dresden (Germany); Cizek, Jakub; Kuriplach, Jan; Prochazka, Ivan [Department of Low Temperature Physics, Charles University, V Holesovickach 2, 18000 Prague (Czech Republic); Egger, Werner; Sperr, Peter [Institut fuer Angewandte Physik und Messtechnik, Fakultaet fuer Luft- und Raumfahrttechnik, Universitaet der Bundeswehr, Heisenbergweg 39, 85579 Neubiberg (Germany)

    2010-11-15

    Nominally undoped, hydrothermally grown ZnO single crystals have been investigated before and after exposure to remote H plasma. Structural characterizations have been made by various positron annihilation spectroscopies (continuous and pulsed slow positron beams, conventional lifetime). The content of bound hydrogen (H-b) before and after the remote H plasma treatment at the polished side of the crystals was determined at depths of 100 and 600 nm, respectively, using nuclear reaction analysis. At a depth of 100 nm, H-b increased from (11.8{+-}2.5) to (48.7{+-}7.6) x 10{sup 19} cm{sup -3} after remote H plasma treatment, whereas at 600 nm no change in H-b was observed. (Copyright copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

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

    International Nuclear Information System (INIS)

    Loukya, B.; Negi, D.S.; Dileep, K.; Kumar, N.; Ghatak, Jay; Datta, R.

    2013-01-01

    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

  3. Physical and chemical properties of a Ga-doped ZnO crystal

    International Nuclear Information System (INIS)

    Stashans, Arvids; Olivos, Katia; Rivera, Richard

    2011-01-01

    First-principles calculations based on density functional theory and strengthened by Hartree-Fock computations have been performed to study a Ga-doped wurtzite-type ZnO crystal. The large 108-atom supercell used throughout this work allows one to model a single point defect within the periodic supercell model. Thus, the Ga impurity produced purely local effects on the properties of the material. The electronic band structure was obtained for both pure and impurity-doped materials. The occurrence of free electrons in the conduction band was observed after the incorporation of Ga, implying the Ga dopant's contribution to n-type electrical conductivity in the ZnO crystal, in agreement with known experimental data. An analysis of the charges on atoms and obtained atomic displacements in the region surrounding the defect showed that there is some alteration in the chemical bonding because of the presence of Ga atoms. In particular, the ionic bonding is strengthened in the defect's neighbourhood.

  4. Physical and chemical properties of a Ga-doped ZnO crystal

    Energy Technology Data Exchange (ETDEWEB)

    Stashans, Arvids; Olivos, Katia; Rivera, Richard, E-mail: arvids@utpl.edu.e [Grupo de FisicoquImica de Materiales, Universidad Tecnica Particular de Loja, Apartado 11-01-608, Loja (Ecuador)

    2011-06-01

    First-principles calculations based on density functional theory and strengthened by Hartree-Fock computations have been performed to study a Ga-doped wurtzite-type ZnO crystal. The large 108-atom supercell used throughout this work allows one to model a single point defect within the periodic supercell model. Thus, the Ga impurity produced purely local effects on the properties of the material. The electronic band structure was obtained for both pure and impurity-doped materials. The occurrence of free electrons in the conduction band was observed after the incorporation of Ga, implying the Ga dopant's contribution to n-type electrical conductivity in the ZnO crystal, in agreement with known experimental data. An analysis of the charges on atoms and obtained atomic displacements in the region surrounding the defect showed that there is some alteration in the chemical bonding because of the presence of Ga atoms. In particular, the ionic bonding is strengthened in the defect's neighbourhood.

  5. Modulating the size of ZnO nanorods on SiO2 substrates by incorporating reduced graphene oxide into the seed layer solution

    Directory of Open Access Journals (Sweden)

    Tzu-Yi Yu

    2017-06-01

    Full Text Available In this research, reduced graphene oxide was incorporated into the ZnO seed layer to modulate the rod diameter of ZnO nanorods (NRs during solgel/hydrothermal growth. To characterize the reduced graphene oxide incorporated ZnO NRs, multiple material analysis techniques including field-emission scanning electron microscopy, surface contact angle measurements, X-ray diffraction, and photoluminescence were used to explore distinct properties of these size modulatable NRs. Results indicate ZnO NRs with smaller diameters could be observed with more reduced graphene oxide added into the ZnO seed layer. Furthermore, better crystallinity, higher hydrophobicity and lower defect concentration could be obtained with more amount of reduced graphene oxide added into the ZnO seed layer. The modulatable reduced graphene oxide-incorporated ZnO NRs growth is promising for future ZnO NRs based nanodevice applications.

  6. Life cycle assessment of facile microwave-assisted zinc oxide (ZnO) nanostructures

    CSIR Research Space (South Africa)

    Papadaki, D

    2017-05-01

    Full Text Available The life cycle assessment of several zinc oxide (ZnO) nanostructures, fabricated by a facile microwave technique, is presented. Key synthesis parameters such as annealing temperature, varied from 90 °C to 220 °C, and microwave power, varied from 110...

  7. Superior environment resistance of quartz crystal microbalance with anatase TiO2/ZnO nanorod composite films

    International Nuclear Information System (INIS)

    Qiang, Wei; Wei, Li; Shaodan, Wang; Yu, Bai

    2015-01-01

    Graphical abstract: ZnO nanorod array being prepared by an in situ method on the QCM coated with Au film via hydrothermal process and surface modification with coated TiO 2 by sol–gel methods to form a superhydrophobic TiO 2 /ZnO composite film the anatase TiO 2 /ZnO nanorod composite film with a sharp, pencil-like structure exhibiting excellent superhydrophobicity (water contact angle of 155°), non-sticking water properties, and an autonomous cleaning property under UV irradiation. The anatase TiO 2 /ZnO nanorod composite film facilitates the precise measurement and extended lifetime of the QCM for the detection of organic gas molecules. - Highlights: • This work combines, for the first time, the advantage of the TiO 2 /ZnO composite film on photocatalysis and reversible super-hydrophobic and super-hydrophilic transition, and puts forward a solution to satisfy weatherability of quartz crystal microbalance in long-term application. • The anatase TiO 2 /ZnO nanorod composite film with pencil structure exhibit excellent super-hydrophobicity (water contact angle can reach 155°), no-sticking water properties and self-cleaning property under UV irradiation. • The photocatalysis and reversible super-hydrophobic and super-hydrophilic transition of the TiO 2 /ZnO nanorod composite film is stable in long-term application. - Abstract: The precise measurement of quartz crystal microbalance (QCM) in the detection and weighing of organic gas molecules is achieved due to excellent superhydrophobicity of a deposited film composite. Photocatalysis is utilized as a method for the self-cleaning of organic molecules on the QCM for extended long-term stability in the precision of the instrument. In this paper, ZnO nanorod array is prepared via in situ methods on the QCM coated with Au film via hydrothermal process. Subsequently, a TiO 2 /ZnO composite film is synthesized by surface modification with TiO 2 via sol–gel methods. Results show the anatase TiO 2 /ZnO nanorod

  8. Preparation of a Non-Polar ZnO Film on a Single-Crystal NdGaO3 Substrate by the RF Sputtering Method

    Science.gov (United States)

    Kashiwaba, Y.; Tanaka, Y.; Sakuma, M.; Abe, T.; Imai, Y.; Kawasaki, K.; Nakagawa, A.; Niikura, I.; Kashiwaba, Y.; Osada, H.

    2018-04-01

    Preparation of non-polar ZnO ( 11\\overline{2} 0 ) films on single-crystal NdGaO3 (NGO) (001) substrates was successfully achieved by the radio frequency (RF) sputtering method. Orientation, deposition rate, and surface roughness of ZnO films strongly depend on the working pressure. Characteristics of ZnO films deposited on single-crystal NGO (001) substrates were compared with those of ZnO films deposited on single-crystal sapphire ( 01\\overline{1} 2 ) substrates. An x-ray diffraction peak of the ZnO ( 11\\overline{2} 0 ) plane was observed on ZnO films deposited on single-crystal NGO (001) substrates under working pressure of less than 0.5 Pa. On the other hand, uniaxially oriented ZnO ( 11\\overline{2} 0 ) films on single-crystal sapphire ( 01\\overline{1} 2 ) substrates were observed under working pressure of 0.1 Pa. The mechanism by which the diffraction angle of the ZnO ( 11\\overline{2} 0 ) plane on single-crystal NGO (001) substrates was shifted is discussed on the basis of anisotropic stress of lattice mismatch. The deposition rate of ZnO films decreased with an increase in working pressure, and the deposition rate on single-crystal NGO (001) substrates was larger than that on single-crystal sapphire ( 01\\overline{1} 2 ) substrates. Root mean square (RMS) roughness of ZnO films increased with an increase in working pressure, and RMS roughness of ZnO films on single-crystal NGO (001) substrates was smaller than that of ZnO films on single-crystal sapphire ( 01\\overline{1} 2 ) substrates even though the film thickness on single-crystal NGO (001) substrates was greater than that on sapphire substrates. It is thought that a single-crystal NGO (001) substrate is useful for deposition of non-polar ZnO ( 11\\overline{2} 0 ) films.

  9. Effects of high-dose hydrogen implantation on defect formation and dopant diffusion in silver implanted ZnO crystals

    Energy Technology Data Exchange (ETDEWEB)

    Yaqoob, Faisal [Department of Physics, State University of New York at Albany, Albany, New York 12222 (United States); Huang, Mengbing, E-mail: mhuang@sunypoly.edu [College of Nanoscale Science and Engineering, State University of New York Polytechnic Institute, Albany, New York 12203 (United States)

    2016-07-28

    This work reports on the effects of a deep high-dose hydrogen ion implant on damage accumulation, defect retention, and silver diffusion in silver implanted ZnO crystals. Single-crystal ZnO samples were implanted with Ag ions in a region ∼150 nm within the surface, and some of these samples were additionally implanted with hydrogen ions to a dose of 2 × 10{sup 16 }cm{sup −2}, close to the depth ∼250 nm. Rutherford backscattering/ion channeling measurements show that crystal damage caused by Ag ion implantation and the amount of defects retained in the near surface region following post-implantation annealing were found to diminish in the case with the H implantation. On the other hand, the additional H ion implantation resulted in a reduction of substitutional Ag atoms upon post-implantation annealing. Furthermore, the presence of H also modified the diffusion properties of Ag atoms in ZnO. We discuss these findings in the context of the effects of nano-cavities on formation and annihilation of point defects as well as on impurity diffusion and trapping in ZnO crystals.

  10. Atomic layer deposition grown composite dielectric oxides and ZnO for transparent electronic applications

    International Nuclear Information System (INIS)

    Gieraltowska, S.; Wachnicki, L.; Witkowski, B.S.; Godlewski, M.; Guziewicz, E.

    2012-01-01

    In this paper, we report on transparent transistor obtained using laminar structure of two high-k dielectric oxides (hafnium dioxide, HfO 2 and aluminum oxide, Al 2 O 3 ) and zinc oxide (ZnO) layer grown at low temperature (60 °C–100 °C) using Atomic Layer Deposition (ALD) technology. Our research was focused on the optimization of technological parameters for composite layers Al 2 O 3 /HfO 2 /Al 2 O 3 for thin film transistor structures with ZnO as a channel and a gate layer. We elaborate on the ALD growth of these oxides, finding that the 100 nm thick layers of HfO 2 and Al 2 O 3 exhibit fine surface flatness and required amorphous microstructure. Growth parameters are optimized for the monolayer growth mode and maximum smoothness required for gating.

  11. Influence of Nanosized Silicon Oxide on the Luminescent Properties of ZnO Nanoparticles

    Directory of Open Access Journals (Sweden)

    Vitaliy Shvalagin

    2016-01-01

    Full Text Available For practical use of nanosized zinc oxide as the phosphor its luminescence quantum yields should be maximized. The aim of this work was to enhance luminescent properties of ZnO nanoparticles and obtain high-luminescent ZnO/SiO2 composites using simpler approaches to colloidal synthesis. The luminescence intensity of zinc oxide nanoparticles was increased about 3 times by addition of silica nanocrystals to the source solutions during the synthesis of ZnO nanoparticles. Then the quantum yield of luminescence of the obtained ZnO/SiO2 composites is more than 30%. Such an impact of silica is suggested to be caused by the distribution of ZnO nanocrystals on the surface of silica, which reduces the probability of separation of photogenerated charges between the zinc oxide nanoparticles of different sizes, and as a consequence, there is a significant increase of the luminescence intensity of ZnO nanoparticles. This way of increasing nano-ZnO luminescence intensity facilitates its use in a variety of devices, including optical ultraviolet and visible screens, luminescent markers, antibacterial coatings, luminescent solar concentrators, luminescent inks for security printing, and food packaging with abilities of informing consumers about the quality and safety of the packaged product.

  12. Synthesis of ZnO nanowire arrays on ZnO−TiO{sub 2} mixed oxide seed layer for dye sensitized solar cell applications

    Energy Technology Data Exchange (ETDEWEB)

    Marimuthu, T. [Advanced Materials and Thin Film Physics Lab, Department of Physics, Alagappa University, Karaikudi (India); Anandhan, N., E-mail: anandhan_kn@rediffmail.com [Advanced Materials and Thin Film Physics Lab, Department of Physics, Alagappa University, Karaikudi (India); Thangamuthu, R. [Electrochemical Materials Science Division, CSIR-Central Electrochemical Research Institute, Karaikudi (India); Mummoorthi, M. [Advanced Materials and Thin Film Physics Lab, Department of Physics, Alagappa University, Karaikudi (India); Ravi, G. [Photonic Crystal Lab, Department of Physics, Alagappa University, Karaikudi (India)

    2016-08-25

    ZnO nanowire arrays (NWAs) were synthesized on ZnO−TiO{sub 2} mixed oxide seeded FTO conducting glass plate by two-step sol-gel and hydrothermal method, respectively. X-ray diffraction patterns reveal the presence of mixed and hexagonal phases in seed layer and NWAs, respectively. Scanning electron microscope images showed that the FTO glass plate is uniformly covered with grains and a few nanorods in seed layer and dense NWAs are vertically grown on the seed layer. The hexagonal structure and high crystal quality have been confirmed by micro Raman spectra. Photoluminescence spectra also present that NWAs have high crystal quality and less atomic defects. UV spectra indicate that NWAs are absorbed more dye molecules and it has the band gap equal to bulk material. The efficiency of ZnO−TiO{sub 2} mixed oxide seed layer and ZnO NWAs is found to be 0.56 and 0.84% respectively. Electrochemical impedance spectra reveal that NWAs DSSC has high charge transfer recombination resistance than the seed layer DSSC. - Highlights: • ZnO nanowire arrays were synthesized by two-step sol-gel and hydrothermal method. • The crystal structure and crystalline quality of films are confirmed by Raman spectra. • The emission properties of films are investigated by photoluminescence spectra. • ZnO nanowire arrays (NWAs) have higher charge transfer recombination resistance. • The conversion efficiency of the seed layer and NWAs is to be 0.56 and 0.84%.

  13. Optical properties of Mn doped ZnO films and wires synthesized by thermal oxidation of ZnMn alloy

    Energy Technology Data Exchange (ETDEWEB)

    Sima, M., E-mail: msima@infim.ro [National Institute of Materials Physics, 105bis Atomistilor Street, 077125 Magurele (Romania); Mihut, L. [National Institute of Materials Physics, 105bis Atomistilor Street, 077125 Magurele (Romania); Vasile, E. [University “Politehnica”of Bucharest, Faculty of Applied Chemistry and Material Science, Department of Oxide Materials and Nanomaterials, No. 1-7 Gh. Polizu Street, 011061 Bucharest (Romania); Sima, Ma.; Logofatu, C. [National Institute of Materials Physics, 105bis Atomistilor Street, 077125 Magurele (Romania)

    2015-09-01

    Mn doped ZnO films and wires, having different manganese concentrations were synthesized by thermal oxidation of the corresponding ZnMn alloy films and wires electrodeposited on a gold substrate. Structural and optical properties were addressed with scanning electron microscopy, X-ray diffraction (XRD), Raman scattering and photoluminescence (PL). To estimate the manganese concentration in Mn doped ZnO films, X-ray photoelectron spectroscopy was used. XRD patterns indicate that the incorporation of Mn{sup 2+} ions into the Zn{sup 2+} site of ZnO lattice takes place. Quenching of the ZnO PL appears due to Mn{sup 2+} ions in the ZnO lattice. Moreover, a significant decrease in the green emission of ZnO is reported in the case of the Mn doped ZnO wire array with a Mn concentration of 1.45%. The wurtzite ZnO has a total of 12 phonon modes, namely, one longitudinal acoustic (LA), two transverse acoustic (TA), three longitudinal optical (LO), and six transverse optical branches. Compared to the undoped ZnO, a gradual up-shift of the Raman lines assigned to the 2LA and A{sub 1} (LO) vibrational modes, from 482 and 567 cm{sup −1} to 532 and 580 cm{sup −1}, respectively, takes place for the Mn doped ZnO films having a Mn concentration between 2 and 15%. Additionally, in the case of the Mn doped ZnO films with 7 and 15% Mn concentration, Raman spectra show the appearance and increase in the relative intensity of the ZnO Raman line assigned to the TA + LO vibrational mode in the 600–750 cm{sup −1} spectral range. For the Mn-doped ZnO wires, the presence of the Raman line peaking at 527 cm{sup −1} confirms the insertion of Mn{sup 2+} ions in ZnO lattice. - Highlights: • Mn doped ZnO films and wires grown by thermal oxidation of ZnMn alloy • Incorporation of Mn{sup 2+} ions into Zn{sup 2+} site of ZnO lattice • Appearance of a strong Raman line in the spectral range 600–800 cm{sup −1} at high Mn concentration • Compensation of the oxygen vacancy at higher

  14. Optical properties of Mn doped ZnO films and wires synthesized by thermal oxidation of ZnMn alloy

    International Nuclear Information System (INIS)

    Sima, M.; Mihut, L.; Vasile, E.; Sima, Ma.; Logofatu, C.

    2015-01-01

    Mn doped ZnO films and wires, having different manganese concentrations were synthesized by thermal oxidation of the corresponding ZnMn alloy films and wires electrodeposited on a gold substrate. Structural and optical properties were addressed with scanning electron microscopy, X-ray diffraction (XRD), Raman scattering and photoluminescence (PL). To estimate the manganese concentration in Mn doped ZnO films, X-ray photoelectron spectroscopy was used. XRD patterns indicate that the incorporation of Mn 2+ ions into the Zn 2+ site of ZnO lattice takes place. Quenching of the ZnO PL appears due to Mn 2+ ions in the ZnO lattice. Moreover, a significant decrease in the green emission of ZnO is reported in the case of the Mn doped ZnO wire array with a Mn concentration of 1.45%. The wurtzite ZnO has a total of 12 phonon modes, namely, one longitudinal acoustic (LA), two transverse acoustic (TA), three longitudinal optical (LO), and six transverse optical branches. Compared to the undoped ZnO, a gradual up-shift of the Raman lines assigned to the 2LA and A 1 (LO) vibrational modes, from 482 and 567 cm −1 to 532 and 580 cm −1 , respectively, takes place for the Mn doped ZnO films having a Mn concentration between 2 and 15%. Additionally, in the case of the Mn doped ZnO films with 7 and 15% Mn concentration, Raman spectra show the appearance and increase in the relative intensity of the ZnO Raman line assigned to the TA + LO vibrational mode in the 600–750 cm −1 spectral range. For the Mn-doped ZnO wires, the presence of the Raman line peaking at 527 cm −1 confirms the insertion of Mn 2+ ions in ZnO lattice. - Highlights: • Mn doped ZnO films and wires grown by thermal oxidation of ZnMn alloy • Incorporation of Mn 2+ ions into Zn 2+ site of ZnO lattice • Appearance of a strong Raman line in the spectral range 600–800 cm −1 at high Mn concentration • Compensation of the oxygen vacancy at higher Mn concentration in ZnO lattice

  15. Catalyst free growth of ZnO nanowires on graphene and graphene oxide and its enhanced photoluminescence and photoresponse

    International Nuclear Information System (INIS)

    Biroju, Ravi K; Giri, P K; Tilak, Nikhil; Rajender, Gone; Dhara, S

    2015-01-01

    We demonstrate the graphene assisted catalyst free growth of ZnO nanowires (NWs) on chemical vapor deposited (CVD) and chemically processed graphene buffer layers at a relatively low growth temperature (580 °C) in the presence and absence of ZnO seed layers. In the case of CVD graphene covered with rapid thermal annealed ZnO buffer layer, the growth of vertically aligned ZnO NWs takes place, while the direct growth on CVD graphene, chemically derived graphene (graphene oxide and graphene quantum dots) without ZnO seed layer resulted in randomly oriented sparse ZnO NWs. Growth mechanism was studied from high resolution transmission electron microscopy and Raman spectroscopy of the hybrid structure. Further, we demonstrate strong UV, visible photoluminescence (PL) and enhanced photoconductivity (PC) from the CVD graphene–ZnO NWs hybrids as compared to the ZnO NWs grown without the graphene buffer layer. The evolution of crystalinity in ZnO NWs grown with ZnO seed layer and graphene buffer layer is correlated with the Gaussian line shape of UV and visible PL. This is further supported by the strong Raman mode at 438 cm −1 significant for the wurtzite phase of the ZnO NWs grown on different graphene substrates. The effect of the thickness of ZnO seed layers and the role of graphene buffer layers on the aligned growth of ZnO NWs and its enhanced PC are investigated systematically. Our results demonstrate the catalyst free growth and superior performance of graphene–ZnO NW hybrid UV photodetectors as compared to the bare ZnO NW based photodetectors. (paper)

  16. Effect of high temperature annealing on defects and optical properties of ZnO single crystals

    International Nuclear Information System (INIS)

    Jiang, M.; Wang, D.D.; Zou, B.; Chen, Z.Q.; Kawasuso, A.; Sekiguchi, T.

    2012-01-01

    Hydrothermal grown ZnO single crystals were annealed in N 2 or O 2 between 900 and 1300 C. Positron lifetime measurements reveal a single lifetime in all the ZnO samples before and after annealing. The positron lifetime is about 181 ps after annealing at 900 C in either N 2 or O 2 atmosphere. However, increase of the positron lifetime is observed after further annealing the sample at higher temperatures up to 1300 C, and it has a faster increase in O 2 ambient. Temperature dependence measurements show that the positron lifetime has very slight increase with temperature for the 900 C annealed sample, while it shows notable variation for the sample annealed at 1300 C. This implied that annealing at high temperature introduces additional defects. These defects are supposed to be Zn vacancy-related defects. Cathodoluminescence (CL) measurements indicates enhancement of both UV and green emission after annealing, and the enhancement of green emission is much stronger for the samples annealed in O 2 ambient. The possible origin of green emission is tentatively discussed. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Graphene oxide-modified ZnO particles: synthesis, characterization, and antibacterial properties

    Directory of Open Access Journals (Sweden)

    Zhong LL

    2015-08-01

    Full Text Available Linlin Zhong, Kyusik Yun Department of Bionanotechnology, Gachon University, Gyeonggi-do, Republic of Korea Abstract: Nanosized ZnO particles with diameters of 15 nm were prepared with a solution precipitation method at low cost and high yield. The synthesis of the particles was functionalized by the organic solvent dimethylformamide, and the particles were covalently bonded to the surface of graphene oxide. The morphology of the graphene oxide sheets and ZnO particles was confirmed with field emission scanning electron microscopy and biological atomic force microscopy. Fourier transform infrared spectroscopy and X-ray diffraction were used to analyze the physical and chemical properties of the ZnO/graphene oxide composites that differed from those of the individual components. Enhanced electrochemical properties were detected with cyclic voltammetry, with a redox peak of the composites at 0.025 mV. Excellent antibacterial activity of ZnO/graphene oxide composites was observed with a microdilution method in which minimum inhibitory concentrations of 6.25 µg/mL for Escherichia coli and Salmonella typhimurium, 12.5 µg/mL for Bacillus subtilis, and 25 µg/mL for Enterococcus faecalis. After further study of the antibacterial mechanism, we concluded that a vast number of reactive oxygen species formed on the surface of composites, improving antibacterial properties. Keywords: graphene oxide, ZnO, characterization, antibacterial property

  18. Intrinsic magnetism of a series of Co substituted ZnO single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Lv Peiwen [Laboratory of Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, National Engineering Research Center for Optoelectronic Crystalline Materials, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Huang Feng [Laboratory of Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, National Engineering Research Center for Optoelectronic Crystalline Materials, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Chu Wangsheng [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, 100049 Beijing (China); Lin Zhang [Laboratory of Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, National Engineering Research Center for Optoelectronic Crystalline Materials, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Chen Dagui [Laboratory of Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, National Engineering Research Center for Optoelectronic Crystalline Materials, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Li Wei [Laboratory of Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, National Engineering Research Center for Optoelectronic Crystalline Materials, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Chen Dongliang [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, 100049 Beijing (China); Wu Ziyu [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, 100049 Beijing (China)

    2008-01-23

    Magnetic properties of a series of well-substituted Zn{sub 1-x}Co{sub x}O (x = 0.018,0.036 and 0.05) single crystals were studied. A typical paramagnetic anisotropy property, which strengthens when x decreases, was found. A magnetization step was observed at 2 K when the magnetic field is parallel to the c axis, indicating that paramagnetic anisotropy is the origin of the strong crystal field effect on Co{sup 2+} ions in ZnO lattices. The Co{sup 2+} single-ion anisotropy parameter 2D is obtained as 7.5 K. The effective moment of Co{sup 2+} takes the values 2.7 {mu}{sub B}, 1.82 {mu}{sub B}, 1.49 {mu}{sub B} when x = 0.018, 0.036 and 0.05, revealing that more antiferromagnetic coupling between Co{sup 2+} ions arises in the perfect crystal when x increases.

  19. Effect of cerium oxide addition on electrical properties of ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Ibrahim, D.M. [National Research Center, Dokki, Giza (Egypt). Dept. of Ceramics; Mounir, M. [Dept. of Physics, Cairo Univ., Giza (Egypt); Mahgoub, A.S. [Cairo Univ., Giza (Egypt). Dept. of Chemistry; Turky, G. [Dept. of Physics, National Research Center, Dokki, Giza (Egypt); El-Desouky, O.A. [Cer. Cleopatra Co., Ramadan City (Egypt)

    2002-07-01

    Mixtures of ZnO and Ce{sub 6} O{sub 11} as additive were prepared by solid state reaction from the calcined oxides with the following proportions: 0.03, 0.08, 0.1, 0.2 and 0.4 mole. Disc specimens 1.2 cm 5 cm in diameter and 0.3 cm thickness were processed under a force of 70 kN and fired at 1150 C/ 30 minutes. XRD revealed the presence of limited solid solution of cerium in ZnO, as evident from the shift in the peaks [0.03-0.04 A ] up to 0.1 mole addition and remains constant. SEM revealed the presence of inter-granular phase. EDAX showed it to be a mixture of ZnO and Ce{sub 6}O{sub 11}. Also cerium was detected in the ZnO grains confirming the XRD results. RCL circuit was used to measure the capacitance and resistance at different frequencies at room temperature. The dielectric constant and conductivity were calculated. The change in resistivity with temperature was followed up to 523 K. The change in dielectric strength with temperature at spot frequency of 10 kHz is demonstrated. The electrical conductivity was found to increase with the proportion of cerium oxide up to 0.2 mole then decreased. (orig.)

  20. Effects of Phonon Coupling and Free Carriers on Band-Edge Emission at Room Temperature in n-type ZnO Crystals

    National Research Council Canada - National Science Library

    Giles, N. C; Xu, Chunchuan; Callahan, M. J; Wang, Buguo; Neal, J. S; Boatner, L. A

    2008-01-01

    Room-temperature photoluminescence has been studied in II-type bulk ZnO crystals representing three different growth methods and having free-carrier concentrations (n) ranging from 10(exp 13) to 10(exp 18) /cu cm...

  1. Optical and structural properties of ZnO nanorods grown on graphene oxide and reduced graphene oxide film by hydrothermal method

    Energy Technology Data Exchange (ETDEWEB)

    Alver, U., E-mail: alver@ksu.edu.tr [Department of Physics, Kahramanmaras Sutcu Imam University, K. Maras 46100 (Turkey); Zhou, W.; Belay, A.B. [Nanoscience and Technology Center, University of Central Florida, Orlando, FL 32816 (United States); Florida Solar Energy Center, Cocoa, FL 32922 (United States); Krueger, R. [Nanoscience and Technology Center, University of Central Florida, Orlando, FL 32816 (United States); Davis, K.O.; Hickman, N.S. [Nanoscience and Technology Center, University of Central Florida, Orlando, FL 32816 (United States); Florida Solar Energy Center, Cocoa, FL 32922 (United States)

    2012-01-15

    ZnO nanorods were grown on graphene oxide (GO) and reduced graphene oxide (RGO) films with seed layers by using simple hydrothermal method. The GO films were deposited by spray coating and then annealed at 400 Degree-Sign C in argon atmosphere to obtain RGO films. The optical and structural properties of the ZnO nanorods were systematically studied by scanning electron microscopy (SEM), X-ray diffraction (XRD) and ultraviolet-visible spectroscopy. The XRD patterns and SEM images show that without a seed layer, no ZnO nanorod deposition occurs on GO or RGO films. Transmittance of ZnO nanorods grown on RGO films was measured to be approximately 83% at 550 nm. Furthermore, while transmittance of RGO films increases with ZnO nanorod deposition, transmittance of GO decreases.

  2. Photoactivity of N-doped ZnO nanoparticles in oxidative and reductive reactions

    Science.gov (United States)

    Oliveira, Jéssica A.; Nogueira, André E.; Gonçalves, Maria C. P.; Paris, Elaine C.; Ribeiro, Caue; Poirier, Gael Y.; Giraldi, Tania R.

    2018-03-01

    N-doped ZnO is a prospective material for photocatalytic reactions. However, only oxidative paths are well investigated in the literature. This paper describes a comparative study about ZnO and ZnO:N potential for oxidative and reductive reactions, probed by rhodamine B dye photodegradation and CO2 photoreduction. The materials were prepared by the polymeric precursor method, using urea as a nitrogen source, and different heat treatments were used to observe their effects on surface decontamination, crystallinity, particle sizes and shapes, and photocatalytic performance. ZnO and ZnO:N presented a wurtzite crystalline structure and nanometric-scale particles. Samples submitted to higher temperatures showed lower specific surface areas, but higher crystallinity and lower contents of species adsorbed on their surfaces. On the other hand, the photocatalysts annealed in shorter times presented smaller crystallite sizes and lower crystallinity. These factors influenced the photoactivity in both conditions, i.e., oxidation and reduction reactions, under the ultraviolet and visible light, indicating that structural factors influenced the adequate charge separation and consequent photocatalytic activity since the as-synthesized samples were versatile photocatalysts in both redox reactions.

  3. Oxide nano crystals for in vivo imaging

    International Nuclear Information System (INIS)

    Heinrich, E.

    2005-01-01

    For small animal, fluorescence imaging is complementary with other techniques such as nuclear imaging (PET, SPECT). In vivo imaging studies imply the development of new luminescent probes, with a better sensitivity and a better biological targeting. These markers must filled biological and optical conditions. Our goal is to study new doped lanthanides oxide nano-crystals, their properties, their functionalization and their ability to target biological molecules. Characterizations of Y 2 O 3 :Eu and Y 2 SiO 5 :Eu nano-crystals (light diffusion, spectrometry, microscopy) allowed the determination of their size, their fluorescence properties but also their photo-bleaching. Means of stabilization of the nanoparticles were also studied in order to decrease their aggregation. Gd 2 O 3 :Eu nano-crystals were as well excited by X rays. Nano-crystals of Y 2 SiO 5 :Eu were functionalized, and organic ligands grafting evidenced by fluorescence and NMR. The functionalized nano-crystals could then recognized biological targets (streptavidin-biotin) and be incubated in the presence of HeLa cells. This report deals with the properties of these nano-crystals and their ability to meet the optical and biological conditions required for the application of in vivo imaging. (author)

  4. Investigation of the pulsed electrochemical deposition of ZnO

    International Nuclear Information System (INIS)

    Dunkel, Christian; Lüttich, Franziska; Graaf, Harald; Oekermann, Torsten; Wark, Michael

    2012-01-01

    The influence of pulse parameters on the morphology of ZnO prepared by pulsed cathodic electrodeposition from oxygen-saturated aqueous ZnCl 2 solution on ITO (indium tin oxide)/glass substrates was investigated. It was found that the ratio between the pulse and the pause duration has a crucial influence on the crystal growth, reaching the highest density of the films with pause/pulse-ratios between 0.25 and 1. Longer pauses cause an Ostwald-like ripening of the ZnO crystals and therewith a strong change in the crystal morphology from roundly shaped to hexagonal. Also the hydrophilicity of the substrate resulting from pre-treatment has a crucial influence on the deposited films, leading to films only consisting of few large and separately grown ZnO crystals for highly hydrophilic substrates and an increasing fraction of small densely grown ZnO crystals with increasing hydrophobicity.

  5. Femtosecond pulse laser-induced self-organized nanostructures on the surface of ZnO crystal

    International Nuclear Information System (INIS)

    Zhong Minjian; Guo Guanglei; Yang Junyi; Ma Ninghua; Ye Guo; Ma Hongliang; Guo Xiaodong; Li Ruxin

    2008-01-01

    This paper reports self-organized nanostructures observed on the surface of ZnO crystal after irradiation by a focused beam of a femtosecond Ti:sapphire laser with a repetition rate of 250 kHz. For a linearly polarized femtosecond laser, the periodic nanograting structure on the ablation crater surface was promoted. The period of self-organization structures is about 180 nm. The grating orientation is adjusted by the laser polarization direction. A long range Bragg-like grating is formed by moving the sample at a speed of 10 μm/s. For a circularly polarized laser beam, uniform spherical nanoparticles were formed as a result of Coulomb explosion during the interaction of near-infrared laser with ZnO crystal

  6. In situ direct observation of photocorrosion in ZnO crystals in ionic liquid using a laser-equipped high-voltage electron microscope

    Directory of Open Access Journals (Sweden)

    J. Ishioka

    2017-03-01

    Full Text Available ZnO photocatalysts in water react with environmental water molecules and corrode under illumination. ZnO nanorods in water can also grow because of water splitting induced by UV irradiation. To investigate their morphological behavior caused by crystal growth and corrosion, here we developed a new laser-equipped high-voltage electron microscope and observed crystal ZnO nanorods immersed in ionic liquid. Exposing the specimen holder to a laser with a wavelength of 325 nm, we observed the photocorrosion in situ at the atomic scale for the first time. This experiment revealed that Zn and O atoms near the interface between the ZnO nanorods and the ionic liquid tended to dissolve into the liquid. The polarity and facet of the nanorods were strongly related to photocorrosion and crystal growth.

  7. ZnO based transparent conductive oxide films with controlled type of conduction

    Energy Technology Data Exchange (ETDEWEB)

    Zaharescu, M., E-mail: mzaharescu@icf.ro [Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Mihaiu, S., E-mail: smihaiu@icf.ro [Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Toader, A. [Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Atkinson, I., E-mail: irinaatkinson@yahoo.com [Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Calderon-Moreno, J.; Anastasescu, M.; Nicolescu, M.; Duta, M.; Gartner, M. [Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Vojisavljevic, K.; Malic, B. [Institute Jožef Stefan, Ljubljana (Slovenia); Ivanov, V.A.; Zaretskaya, E.P. [State Scientific and Production Association “Scientific-Practical Materials Research Center of the National Academy of Science Belarus, P. Brovska str.19, 220072, Minsk (Belarus)

    2014-11-28

    The transparent conductive oxide films with controlled type of conduction are of great importance and their preparation is intensively studied. In our work, the preparation of such films based on doped ZnO was realized in order to achieve controlled type of conduction and high concentration of the charge carriers. Sol–gel method was used for films preparation and several dopants were tested (Sn, Li, Ni). Multilayer deposition was performed on several substrates: SiO{sub 2}/Si wafers, silica-soda-lime and/or silica glasses. The structural and morphological characterization of the obtained films were done by scanning electron microscopy, X-ray diffraction, X-ray fluorescence, X-ray photoelectron spectroscopy and atomic force microscopy respectively, while spectroscopic ellipsometry and transmittance measurements were done for determination of optical properties. The selected samples with the best structural, morphological and optical properties were subjected to electrical measurement (Hall and Seebeck effect). In all studied cases, samples with good adherence and homogeneous morphology as well as monophasic wurtzite type structure were obtained. The optical constants (refractive index and extinction coefficient) were calculated from spectroscopic ellipsometry data using Cauchy model. Films with n- or p-type conduction were obtained depending on the composition, number of deposition and thermal treatment temperature. - Highlights: • Transparent conductive ZnO based thin films were prepared by the sol–gel method. • Controlled type of conduction is obtained in (Sn, Li) doped and Li-Ni co-doped ZnO films. • Hall and Seebeck measurements proved the p-type conductivity for Li-Ni co-doped ZnO films. • The p-type conductivity was maintained even after 4-months of storage. • Influence of dopant- and substrate-type on the ZnO films properties was established.

  8. In situ reduced graphene oxide interlayer for improving electrode performance in ZnO nanorods

    Science.gov (United States)

    Venkatesan, A.; Ramesha, C. K.; Kannan, E. S.

    2016-06-01

    The effect of reduced graphene oxide (RGO) thin film on the transport characteristics of vertically aligned zinc oxide nanorods (ZnO NRs) grown on ITO substrate was studied. GO was uniformly drop casted on ZnO NRs as a passivation layer and then converted into RGO by heating it at 60 °C prior to metal electrode deposition. This low temperature reduction is facilitated by the thermally excited electrons from ZnI interstitial sites (~30 meV). Successful reduction of GO was ascertained from the increased disorder band (D) intensity in the Raman spectra. Temperature (298 K-10 K) dependent transport measurements of RGO-ZnO NRs indicate that the RGO layer not only acts as a short circuiting inhibitor but also reduces the height of the potential barrier for electron tunneling. This is confirmed from the temperature dependent electrical characteristics which revealed a transition of carrier transport from thermionic emission at high temperature (T  >  100 K) to tunneling at low temperature (T  <  100 K) across the interface. Our technique is the most promising approach for making reliable electrical contacts on vertically aligned ZnO NRs and improving the reproducibility of device characteristics.

  9. Synthesis of reduced graphene oxide intercalated ZnO quantum dots nanoballs for selective biosensing detection

    International Nuclear Information System (INIS)

    Chen, Jing; Zhao, Minggang; Li, Yingchun; Fan, Sisi; Ding, Longjiang; Liang, Jingjing; Chen, Shougang

    2016-01-01

    Highlights: • A MWCNTs/rGO/ZnO quantum dots intercalation nanoballs decorated 3D hierarchical architecture is fabricated on Ni foam. • Large numbers of ZnO quantum dots are intercalated by rGO sheets to construct hierarchical nanoballs. • Improved mechanical, kinetic and electrochemical properties are found. • The strong interfacial effect makes the material can be used for selective detection of dopamine, ascorbic acid and uric acid. - Abstract: ZnO quantum dots (QDs), reduced graphene oxide (rGO) and multi-walled carbon nanotubes (MWCNTs) are always used in sensors due to their excellent electrochemical characteristics. In this work, ZnO QDs were intercalated by rGO sheets with cross-linked MWCNTs to construct intercalation nanoballs. A MWCNTs/rGO/ZnO QDs 3D hierarchical architecture was fabricated on supporting Ni foam, which exhibited excellent mechanical, kinetic and electrochemical properties. The intercalation construction can introduce strong interfacial effects to improve the surface electronic state. The selectively determinate of uric acid, dopamine, and ascorbic acid by an electrode material using distinct applied potentials was realized.

  10. Synthesis of cadmium oxide doped ZnO nanostructures using electrochemical deposition

    International Nuclear Information System (INIS)

    Singh, Trilok; Pandya, D.K.; Singh, R.

    2011-01-01

    Research highlights: → Ternary ZnCdO alloy semiconductor nanostructures were grown using electrochemical deposition. → X-ray diffraction measurements showed that the nanostructures were of wurtzite structure and possessed a compressive stress along the c-axis direction. → The cut-off wavelength shifted from blue to red on account of the Cd incorporation in the ZnO and the average transmittance decreased by ∼31%. → The bandgap tuning for 4-16 at% Cd in the initial solution was achieved in the range of 3.08-3.32 eV (up to 0.24 eV). - Abstract: Ternary ZnCdO alloy semiconductor nanostructures were grown using electrochemical deposition. Crystalline nanostructures/nanorods with cadmium concentration ranging from 4 to 16 at% in the initial solution were electrodeposited on tin doped indium oxide (ITO) conducting glass substrates at a constant cathodic potential -0.9 V and subsequently annealed in air at 300 deg. C. X-ray diffraction measurements showed that the nanostructures were of wurtzite structure and possessed a compressive stress along the c-axis direction. The elemental composition of nanostructures was confirmed by energy dispersive spectroscopy (EDS). ZnO nanostructures were found to be highly transparent and had an average transmittance of 85% in the visible range of the spectrum. After the incorporation of Cd content into ZnO the average transmittance decreased and the bandgap tuning was also achieved.

  11. Synthesis of reduced graphene oxide intercalated ZnO quantum dots nanoballs for selective biosensing detection

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jing; Zhao, Minggang, E-mail: zhaomg@ouc.edu.cn; Li, Yingchun; Fan, Sisi; Ding, Longjiang; Liang, Jingjing; Chen, Shougang, E-mail: sgchen@ouc.edu.cn

    2016-07-15

    Highlights: • A MWCNTs/rGO/ZnO quantum dots intercalation nanoballs decorated 3D hierarchical architecture is fabricated on Ni foam. • Large numbers of ZnO quantum dots are intercalated by rGO sheets to construct hierarchical nanoballs. • Improved mechanical, kinetic and electrochemical properties are found. • The strong interfacial effect makes the material can be used for selective detection of dopamine, ascorbic acid and uric acid. - Abstract: ZnO quantum dots (QDs), reduced graphene oxide (rGO) and multi-walled carbon nanotubes (MWCNTs) are always used in sensors due to their excellent electrochemical characteristics. In this work, ZnO QDs were intercalated by rGO sheets with cross-linked MWCNTs to construct intercalation nanoballs. A MWCNTs/rGO/ZnO QDs 3D hierarchical architecture was fabricated on supporting Ni foam, which exhibited excellent mechanical, kinetic and electrochemical properties. The intercalation construction can introduce strong interfacial effects to improve the surface electronic state. The selectively determinate of uric acid, dopamine, and ascorbic acid by an electrode material using distinct applied potentials was realized.

  12. Antibacterial activity against Escherichia coli and characterization of ZnO and ZnO–Al2O3 mixed oxide nanoparticles

    Directory of Open Access Journals (Sweden)

    Ertan Şahin

    2017-02-01

    Full Text Available In order to achieve better antibacterial water insoluble nanoparticles (Nanoparticles of ZnO and ZnO–Al2O3 were studied. ZnO–Al2O3 mixed oxide nanoparticles were produced from a solution containing Zn(AC2⋅2H2O and AlCl3 by Solvothermal method. The calcination process of the ZnO–Al2O3 composite nanoparticles brought forth polycrystalline one phase ZnO–Al2O3 nanoparticles of 30–50 nm in diameters. ZnO and ZnO–Al2O3 were crystallized into würtzite and rock salt structures, respectively. The structural properties of this sample were analyzed by XRD and compared with bulk case of these samples. Antibacterial effectiveness of the ZnO and ZnO–Al2O3 nanoparticles were tested against general Escherichia coli (E. coli ATCC 25922 and E. coli O157:H7 by measuring the growth through optical density and digital counting of live–dead cells. Minimum inhibitory concentration values against four representative bacteria along with E. coli O157:H7 were also obtained.

  13. Oxidation and crystal field effects in uranium

    Energy Technology Data Exchange (ETDEWEB)

    Tobin, J. G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Booth, C. H. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Shuh, D. K. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); van der Laan, G. [Diamond Light Source, Didcot (United Kingdom); Sokaras, D. [Stanford Synchrotron Radiation Lightsource, Stanford, CA (United States); Weng, T. -C. [Stanford Synchrotron Radiation Lightsource, Stanford, CA (United States); Yu, S. W. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Bagus, P. S. [Univ. of North Texas, Denton, TX (United States); Tyliszczak, T. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Nordlund, D. [Stanford Synchrotron Radiation Lightsource, Stanford, CA (United States)

    2015-07-06

    An extensive investigation of oxidation in uranium has been pursued. This includes the utilization of soft x-ray absorption spectroscopy, hard x-ray absorption near-edge structure, resonant (hard) x-ray emission spectroscopy, cluster calculations, and a branching ratio analysis founded on atomic theory. The samples utilized were uranium dioxide (UO2), uranium trioxide (UO3), and uranium tetrafluoride (UF4). As a result, a discussion of the role of non-spherical perturbations, i.e., crystal or ligand field effects, will be presented.

  14. Physical model construction for electrical anisotropy of single crystal zinc oxide micro/nanobelt using finite element method

    International Nuclear Information System (INIS)

    Yu, Guangbin; Tang, Chaolong; Song, Jinhui; Lu, Wenqiang

    2014-01-01

    Based on conductivity characterization of single crystal zinc oxide (ZnO) micro/nanobelt (MB/NB), we further investigate the physical mechanism of nonlinear intrinsic resistance-length characteristic using finite element method. By taking the same parameters used in experiment, a model of nonlinear anisotropic resistance change with single crystal MB/NB has been deduced, which matched the experiment characterization well. The nonlinear resistance-length comes from the different electron moving speed in various crystal planes. As the direct outcome, crystallography of the anisotropic semiconducting MB/NB has been identified, which could serve as a simple but effective method to identify crystal growth direction of single crystal semiconducting or conductive nanomaterial

  15. Optimization of CVD parameters for long ZnO NWs grown on ITO

    Indian Academy of Sciences (India)

    The optimization of chemical vapour deposition (CVD) parameters for long and vertically aligned (VA) ZnO nanowires (NWs) were investigated. Typical ZnO NWs as a single crystal grown on indium tin oxide (ITO)-coated glass substrate were successfully synthesized. First, the conducted side of ITO–glass substrate was ...

  16. Effect of KrF excimer laser irradiation on the surface changes and photoelectric properties of ZnO single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Yong [Institute of Laser Engineering, Beijing University of Technology, Beijing 100124 (China); Beijing Engineering Research Center of 3D Printing for Digital Medical Health, Beijing International Cooperation Base of 3D Printing for Digital MedicalHealth, Beijing University of Technology, Beijing 100124 (China); Zhao, Yan [Institute of Laser Engineering, Beijing University of Technology, Beijing 100124 (China); Jiang, Yijian, E-mail: yjjiang@bjut.edu.cn [Institute of Laser Engineering, Beijing University of Technology, Beijing 100124 (China); Beijing Engineering Research Center of 3D Printing for Digital Medical Health, Beijing International Cooperation Base of 3D Printing for Digital MedicalHealth, Beijing University of Technology, Beijing 100124 (China)

    2016-06-25

    In this paper, the effect of KrF pulsed excimer laser irradiation on the structural, surface morphology, photoluminescence and electrical properties of ZnO single crystal was investigated. Compared to the as-grown sample, at an irradiation energy density of 257 mJ/cm{sup 2}, the ZnO single crystal exhibits a series of phenomenon: XRD and Raman results show that the crystallization of ZnO quality change slightly, resistivity is decreased by two orders of magnitude, carrier concentration is increased by one order of magnitude. After laser irradiation, the surface shows some strip lines and no cracks. Formula calculation and simulation results show that the stripes are not caused by surface melting. We speculate that these stripes are caused by the precipitation of ZnO material inside to the surface. Due to the reduction of oxygen vacancies, UV emission has been enhanced and visible emission has been declined after irradiation. After the laser irradiation, the visible light of ZnO surface can be regulated. The experimental results show that KrF laser irradiation could effectively improve the optical and electrical properties of ZnO single crystal, which is important for the application of high performance of emitting optoelectronic devices. - Highlights: • After laser irradiation, the surface shows some strip lines and no cracks. • The visible light of as-irradiated ZnO surface can be regulated to four colors. • The electrical properties of as-irradiated ZnO has been improved greatly.

  17. Cobalt oxides from crystal chemistry to physics

    CERN Document Server

    Raveau, Bernard

    2012-01-01

    Unparalleled in the breadth and depth of its coverage of all important aspects, this book systematically treats the electronic and magnetic properties of stoichiometric and non-stoichiometric cobaltites in both ordered and disordered phases. Authored by a pioneer and a rising star in the field, the monograph summarizes, organizes and streamlines the otherwise difficult-to-obtain information on this topic. An introductory chapter sets forth the crystal chemistry of cobalt oxides to lay the groundwork for an understanding of the complex phenomena observed in this materials class. Special emphasis is placed on a comprehensive discussion of cobaltite physical properties in different structural families. Providing a thorough introduction to cobalt oxides from a chemical and physical viewpoint as a basis for understanding their intricacies, this is a must-have for both experienced researchers as well as entrants to the field.

  18. Boron doped ZnO embedded into reduced graphene oxide for electrochemical supercapacitors

    Energy Technology Data Exchange (ETDEWEB)

    Alver, Ü., E-mail: ualver@ktu.edu.tr [Karadeniz Technical University, Dept. of Metallurgical and Materials Engineering, 61080 Trabzon (Turkey); Tanrıverdi, A. [Kahramanmaras Sutcu Imam University, Department of Physics, 46100 Kahramanmaraş (Turkey)

    2016-08-15

    Highlights: • Boron doped ZnO particles are fabricated and embedded into reduced graphene oxide (RGO) by hydrothermal method. • RGO/ZnO:B composites are used as electrodes for supercapacitors. • Presence of boron in RGO/ZnO composites caused increasing the stability and specific capacitance of electrodes. - Abstract: In this work, reduced graphene oxide/boron doped zinc oxide (RGO/ZnO:B) composites were fabricated by a hydrothermal process and their electrochemical properties were investigated as a function of dopant concentration. First, boron doped ZnO (ZnO:B) particles was fabricated with different boron concentrations (5, 10, 15 and 20 wt%) and then ZnO:B particles were embedded into RGO sheets. The physical properties of sensitized composites were characterized by XRD and SEM. Characterization indicated that the ZnO:B particles with plate-like structure in the composite were dispersed on graphene sheets. The electrochemical properties of the RGO/ZnO:B composite were investigated through cyclic voltammetry, galvanostatic charge/discharge measurements in a 6 M KOH electrolyte. Electrochemical measurements show that the specific capacitance values of RGO/ZnO:B electrodes increase with increasing boron concentration. RGO/ZnO:B composite electrodes (20 wt% B) display the specific capacitance as high as 230.50 F/g at 5 mV/s, which is almost five times higher than that of RGO/ZnO (52.71 F/g).

  19. Boron doped ZnO embedded into reduced graphene oxide for electrochemical supercapacitors

    International Nuclear Information System (INIS)

    Alver, Ü.; Tanrıverdi, A.

    2016-01-01

    Highlights: • Boron doped ZnO particles are fabricated and embedded into reduced graphene oxide (RGO) by hydrothermal method. • RGO/ZnO:B composites are used as electrodes for supercapacitors. • Presence of boron in RGO/ZnO composites caused increasing the stability and specific capacitance of electrodes. - Abstract: In this work, reduced graphene oxide/boron doped zinc oxide (RGO/ZnO:B) composites were fabricated by a hydrothermal process and their electrochemical properties were investigated as a function of dopant concentration. First, boron doped ZnO (ZnO:B) particles was fabricated with different boron concentrations (5, 10, 15 and 20 wt%) and then ZnO:B particles were embedded into RGO sheets. The physical properties of sensitized composites were characterized by XRD and SEM. Characterization indicated that the ZnO:B particles with plate-like structure in the composite were dispersed on graphene sheets. The electrochemical properties of the RGO/ZnO:B composite were investigated through cyclic voltammetry, galvanostatic charge/discharge measurements in a 6 M KOH electrolyte. Electrochemical measurements show that the specific capacitance values of RGO/ZnO:B electrodes increase with increasing boron concentration. RGO/ZnO:B composite electrodes (20 wt% B) display the specific capacitance as high as 230.50 F/g at 5 mV/s, which is almost five times higher than that of RGO/ZnO (52.71 F/g).

  20. Photovoltaic Properties of Co-doped ZnO Thin Film on Glass Substrate

    International Nuclear Information System (INIS)

    Sabia Aye; Zin Ma Ma; May Nwe Oo; Than Than Win; Yin Maung Maung; Ko Ko Kyaw Soe

    2011-12-01

    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. Direct Heteroepitaxial Growth of ZnO over GaN Crystal in Aqueous Solution

    Science.gov (United States)

    Hamada, Takahiro; Ito, Akihiro; Nagao, Nobuaki; Suzuki, Nobuyasu; Fujii, Eiji; Tsujimura, Ayumu

    2013-04-01

    We report on the structural and electrical properties of ZnO films grown on surface-treated GaN/Al2O3 substrates by chemical bath deposition. X-ray diffraction analysis indicated that the ZnO films had a single-crystalline wurtzite structure with c-axis orientation. The ZnO film exhibited n-type conduction with a carrier concentration of 6.9 ×1018 cm-3, an electron mobility of 41 cm2/(V.s), and a resistivity of 2.2 ×10-2 Ω.cm. A low specific contact resistivity of 4.3 ×10-3 Ω.cm2 was obtained at the ZnO/n-GaN interface. Additionally, the ZnO film exhibited high transparency in the visible and infrared region.

  2. Defects in N{sup +} ion-implanted ZnO single crystals studied by positron annihilation and Hall effect

    Energy Technology Data Exchange (ETDEWEB)

    Brauer, G.; Anwand, W.; Skorupa, W. [Institut fuer Ionenstrahlphysik und Materialforschung, Forschungszentrum Rossendorf, Dresden (Germany); Kuriplach, J.; Melikhova, O.; Cizek, J.; Prochazka, I. [Department of Low Temperature Physics, Faculty of Mathematics and Physics, Charles Univ., Prague (Czech Republic); Wenckstern, H. von; Brandt, M.; Lorenz, M.; Grundmann, M. [Institut fuer Experimentelle Physik II, Universitaet Leipzig (Germany)

    2007-07-01

    High quality ZnO single crystals of dimensions 10 x 10 x 0.5 mm{sup 3}, grown by a hydrothermal approach, have been implanted by 40 keV N{sup +} ions to a fluence of 1 x 10{sup 15} cm{sup -2} at room temperature. Their properties revealed by positron annihilation and Hall effect measurements are given in the as-grown and as-irradiated states, and after post-implantation annealing in an oxygen ambient at 200 C and 500 C. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. Deep levels due to hydrogen in ZnO single crystals

    Science.gov (United States)

    Parmar, Narendra; Weber, Marc; Lynn, Kelvin

    2009-05-01

    Hydrogen impurities and oxygen vacancies are involved in the ˜0.7 eV shift of the optical absorption edge of ZnO. Deuterium causes a smaller shift. Titanium metal is used to bind hydrogen as it diffuses out of ZnO. Positron annihilation spectroscopy coupled with other techniques point to the presence of oxygen vacancies. Removing hydrogen followed by annealing in oxygen reduces the carrier concentration.

  4. Crystallization of purple nitrous oxide reductase from Pseudomonas stutzeri

    International Nuclear Information System (INIS)

    Pomowski, Anja; Zumft, Walter G.; Kroneck, Peter M. H.; Einsle, Oliver

    2010-01-01

    The physiologically active form of nitrous oxide reductase was isolated and crystallized under strict exclusion of dioxygen and diffraction data were collected from crystals belonging to two different space groups. Nitrous oxide reductase (N 2 OR) from Pseudomonas stutzeri catalyzes the final step in denitrification: the two-electron reduction of nitrous oxide to molecular dinitrogen. Crystals of the enzyme were grown under strict exclusion of dioxygen by sitting-drop vapour diffusion using 2R,3R-butanediol as a cryoprotectant. N 2 OR crystallized in either space group P1 or P6 5 . Interestingly, the key determinant for the resulting space group was the crystallization temperature. Crystals belonging to space group P1 contained four 130 kDa dimers in the asymmetric unit, while crystals belonging to space group P6 5 contained a single dimer in the asymmetric unit. Diffraction data were collected to resolutions better than 2 Å

  5. Formation of Isolated Zn Vacancies in ZnO Single Crystals by Absorption of Ultraviolet Radiation: A Combined Study Using Positron Annihilation, Photoluminescence, and Mass Spectroscopy

    Science.gov (United States)

    Khan, Enamul H.; Weber, Marc H.; McCluskey, Matthew D.

    2013-07-01

    Positron annihilation spectra reveal isolated zinc vacancy (VZn) creation in single-crystal ZnO exposed to 193-nm radiation at 100mJ/cm2 fluence. The appearance of a photoluminescence excitation peak at 3.18 eV in irradiated ZnO is attributed to an electronic transition from the VZn acceptor level at ˜100meV to the conduction band. The observed VZn density profile and hyperthermal Zn+ ion emission support zinc vacancy-interstitial Frenkel pair creation by exciting a wide 6.34 eV Zn-O antibonding state at 193-nm photon—a novel photoelectronic process for controlled VZn creation in ZnO.

  6. Transient behaviors of ZnO thin films on a transparent, flexible polyethylene terephthalate substrate

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yong Jun [Department of Nano-Physics, Gachon University, 1342 Seongnamdaero, Sujeong-gu, Seongnam-si, Gyeonggi-do 461-701 (Korea, Republic of); Lee, Ho Seok [Department of Materials Science and Engineering, Korea University, 5-1 Anam-dong, Seongbuk-gu, Seoul 136-713 (Korea, Republic of); Noh, Jin-Seo, E-mail: jinseonoh@gachon.ac.kr [Department of Nano-Physics, Gachon University, 1342 Seongnamdaero, Sujeong-gu, Seongnam-si, Gyeonggi-do 461-701 (Korea, Republic of)

    2016-03-31

    Thickness-dependent electrical, structural, and optical properties of zinc oxide (ZnO) thin films on polyethylene terephthalate (PET) substrates have been investigated in the very thin thickness range of 20 to 120 nm. In this thickness range, the electrical resistance of ZnO film increased with an increase in film thickness. This unusual transition behavior was explained in terms of structural evolution from Zn-phase-incorporating non-crystalline ZnO to hexagonal-structured ZnO. A critical thickness for the full development of hexagonal ZnO crystal was estimated at approximately 80 nm in this study. ZnO thin films on PET substrates exhibit a high optical transmittance of > 70% and good endurance to bending cycles over the measured thickness range. The results of this study indicate that a trade-off should be sought between structural, electrical, optical, and mechanical properties for practical applications of very thin ZnO films on organic substrates. - Highlights: • Very thin ZnO films were sputter-deposited on the PET substrate. • The ZnO film resistance increases with an increase in film thickness until saturation. • Hexagonal crystal structures gradually develop with increasing film thickness. • A Zn phase appears in a 20-nm-thick ZnO film. • ZnO films show high optical transmittance of > 80% and good endurance to bending.

  7. Transient behaviors of ZnO thin films on a transparent, flexible polyethylene terephthalate substrate

    International Nuclear Information System (INIS)

    Kim, Yong Jun; Lee, Ho Seok; Noh, Jin-Seo

    2016-01-01

    Thickness-dependent electrical, structural, and optical properties of zinc oxide (ZnO) thin films on polyethylene terephthalate (PET) substrates have been investigated in the very thin thickness range of 20 to 120 nm. In this thickness range, the electrical resistance of ZnO film increased with an increase in film thickness. This unusual transition behavior was explained in terms of structural evolution from Zn-phase-incorporating non-crystalline ZnO to hexagonal-structured ZnO. A critical thickness for the full development of hexagonal ZnO crystal was estimated at approximately 80 nm in this study. ZnO thin films on PET substrates exhibit a high optical transmittance of > 70% and good endurance to bending cycles over the measured thickness range. The results of this study indicate that a trade-off should be sought between structural, electrical, optical, and mechanical properties for practical applications of very thin ZnO films on organic substrates. - Highlights: • Very thin ZnO films were sputter-deposited on the PET substrate. • The ZnO film resistance increases with an increase in film thickness until saturation. • Hexagonal crystal structures gradually develop with increasing film thickness. • A Zn phase appears in a 20-nm-thick ZnO film. • ZnO films show high optical transmittance of > 80% and good endurance to bending.

  8. Hydrogen peroxide treatment on ZnO substrates to investigate the characteristics of Pt and Pt oxide Schottky contacts

    International Nuclear Information System (INIS)

    Tsai, Chia-Hung; Hung, Chen-I; Yang, Cheng-Fu; Houng, Mau-Phon

    2010-01-01

    We utilize hydrogen peroxide (H 2 O 2 ) treatment on (0 0 0 1) ZnO substrates to investigate the characteristics of Pt and Pt oxide Schottky contacts (SCs). X-ray rocking curves show the mosaicity structure becomes larger after H 2 O 2 treatment. Photoluminescence (PL) spectra show the yellow-orange emission peaking at ∼576-580 nm with respect to deep level of oxygen interstitials introduced by H 2 O 2 treatment. The threshold formation of ZnO 2 resistive layer on H 2 O 2 -treated ZnO for 45 min is observed from grazing-incidence X-ray diffraction. The better electrical characteristic is performed by Pt oxide SC with the larger barrier height (1.09 eV) and the lower leakage current (9.52 x 10 -11 A/cm 2 at -2 V) than Pt SC on the H 2 O 2 -treated ZnO for 60 min. X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometer (SIMS) examinations indicate the promoted interface oxide bonding and Zn outdiffusion for Pt oxide contact, different from Pt contact. Based on current-voltage, capacitance-voltage, X-ray diffraction, PL spectra, XPS, and SIMS results, the possible mechanism for effective rectifying characteristic and enhanced Schottky fbehavior is given.

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

    Energy Technology Data Exchange (ETDEWEB)

    Chen, K.J. [Institute of Microelectronics and Department of Electrical Engineering, Center for Micro/Nano Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Fang, T.H. [Institute of Mechanical and Electromechanical Engineering, National Formosa University, Yunlin 632, Taiwan (China); Hung, F.Y. [Institute of Nanotechnology and Microsystems Engineering, Center for Micro/Nano Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan (China)], E-mail: fyhung@mail.mse.ncku.edu.tw; Ji, L.W. [Institute of Mechanical and Electromechanical Engineering, National Formosa University, Yunlin 632, Taiwan (China); Chang, S.J.; Young, S.J. [Institute of Microelectronics and Department of Electrical Engineering, Center for Micro/Nano Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Hsiao, Y.J. [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan (China)

    2008-07-15

    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.

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

    International Nuclear Information System (INIS)

    Chen, K.J.; Fang, T.H.; Hung, F.Y.; Ji, L.W.; Chang, S.J.; Young, S.J.; Hsiao, Y.J.

    2008-01-01

    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

  11. Shape-dependent plasma-catalytic activity of ZnO nanomaterials coated on porous ceramic membrane for oxidation of butane.

    Science.gov (United States)

    Sanjeeva Gandhi, M; Mok, Young Sun

    2014-12-01

    In order to explore the effects of the shape of ZnO nanomaterials on the plasma-catalytic decomposition of butane and the distribution of byproducts, three types of ZnO nanomaterials (nanoparticles (NPs), nanorods (NRs) and nanowires (NWs)) were prepared and coated on multi-channel porous alumina ceramic membrane. The structures and morphologies of the nanomaterials were confirmed by X-ray diffraction method and scanning electron microscopy. The observed catalytic activity of ZnO in the oxidative decomposition of butane was strongly shape-dependent. It was found that the ZnO NWs exhibited higher catalytic activity than the other nanomaterials and could completely oxidize butane into carbon oxides (COx). When using the bare or ZnO NPs-coated ceramic membrane, several unwanted partial oxidation and decomposition products like acetaldehyde, acetylene, methane and propane were identified during the decomposition of butane. When the ZnO NWs- or ZnO NRs-coated membrane was used, however, the formation of such unwanted byproducts except methane was completely avoided, and full conversion into COx was achieved. Better carbon balance and COx selectivity were obtained with the ZnO NWs and NRs than with the NPs. Copyright © 2014 Elsevier Ltd. All rights reserved.

  12. 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.

  13. Structural and Optical Properties of ZnO Thin Film Prepared by Oxidation of Zn Metal Powders

    International Nuclear Information System (INIS)

    Hassan, N.K.; Hashim, M.R.

    2013-01-01

    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)

  14. UV Enhanced Oxygen Response Resistance Ratio of ZnO Prepared by Thermally Oxidized Zn on Sapphire Substrate

    Directory of Open Access Journals (Sweden)

    Cheng-Chang Yu

    2013-01-01

    Full Text Available ZnO thin film was fabricated by thermally oxidized Zn at 600°C for 1 h. A surface containing nanostructured dumbbell and lines was observed by scanning electron microscope (SEM. The ZnO resistor device was formed after the following Ti/Au metallization. The device resistance was characterized at different oxygen pressure environment in the dark and under ultraviolet (UV light illumination coming from the mercury lamp with a short pass filter. The resistance increases with the increase of oxygen pressure. The resistance decreases and response increases with the increase of light intensity. Models considering the barrier height variation caused by the adsorbed oxygen related species were used to explain these results. The UV light illumination technology shows an effective method to enhance the detection response for this ZnO resistor oxygen sensor.

  15. ZnO Nanowires Synthesized by Vapor Phase Transport Deposition on Transparent Oxide Substrates

    Directory of Open Access Journals (Sweden)

    Taylor Curtis

    2010-01-01

    Full Text Available Abstract Zinc oxide nanowires have been synthesized without using metal catalyst seed layers on fluorine-doped tin oxide (FTO substrates by a modified vapor phase transport deposition process using a double-tube reactor. The unique reactor configuration creates a Zn-rich vapor environment that facilitates formation and growth of zinc oxide nanoparticles and wires (20–80 nm in diameter, up to 6 μm in length, density <40 nm apart at substrate temperatures down to 300°C. Electron microscopy and other characterization techniques show nanowires with distinct morphologies when grown under different conditions. The effect of reaction parameters including reaction time, temperature, and carrier gas flow rate on the size, morphology, crystalline structure, and density of ZnO nanowires has been investigated. The nanowires grown by this method have a diameter, length, and density appropriate for use in fabricating hybrid polymer/metal oxide nanostructure solar cells. For example, it is preferable to have nanowires no more than 40 nm apart to minimize exciton recombination in polymer solar cells.

  16. Biodiesel synthesis by TiO2-ZnO mixed oxide nanocatalyst catalyzed palm oil transesterification process.

    Science.gov (United States)

    Madhuvilakku, Rajesh; Piraman, Shakkthivel

    2013-12-01

    Biodiesel is a promising alternating environmentally benign fuel to mineral diesel. For the development of easier transesterification process, stable and active heterogeneous mixed metal oxide of TiO2-ZnO and ZnO nanocatalysts were synthesized and exploited for the palm oil transesterification process. The synthesized catalysts were characterized by XRD, FT-IR, and FE-SEM studies for their structural and morphological characteristics. It was found that TiO2-ZnO nanocatalyst exhibits good catalytic activity and the catalytic performance was greatly depends on (i) catalyst concentration (ii) methanol to oil molar ratio (iii) reaction temperature and (iv) reaction time. A highest 98% of conversion was obtained at the optimum reaction parameters with 200 mg of catalyst loading and the biodiesel was analyzed by TLC and (1)H NMR techniques. The TiO2-ZnO nanocatalyst shows good catalytic performance over the ZnO catalyst, which could be a potential candidate for the large-scale biodiesel production from palm oil at the reduced temperature and time. Copyright © 2013. Published by Elsevier Ltd.

  17. Solvothermal synthesis, characterization and optical properties of ZnO, ZnO-MgO and ZnO-NiO, mixed oxide nanoparticles

    International Nuclear Information System (INIS)

    Aslani, Alireza; Arefi, Mohammad Reza; Babapoor, Aziz; Amiri, Asghar; Beyki-Shuraki, Khalil

    2011-01-01

    ZnO-MgO and ZnO-NiO mixed oxides nanoparticles were produced from a solution containing Zinc acetate, Mg and Ni nitrate by Solvothermal method. The calcination process of the ZnO-MgO and ZnO-NiO composites nanoparticles brought forth polycrystalline two-phase ZnO-MgO and ZnO-NiO nanoparticles of 40-80 nm in diameters. ZnO, MgO and NiO were crystallized into wuertzite and rock salt structures, respectively. The optical properties of ZnO-MgO and ZnO-NiO nanoparticles were obtained by solid state UV and solid state florescent. The XRD, SEM and Raman spectroscopies of these nanoparticles were analyzed.

  18. Solvothermal synthesis, characterization and optical properties of ZnO, ZnO-MgO and ZnO-NiO, mixed oxide nanoparticles

    Science.gov (United States)

    Aslani, Alireza; Arefi, Mohammad Reza; Babapoor, Aziz; Amiri, Asghar; Beyki-Shuraki, Khalil

    2011-03-01

    ZnO-MgO and ZnO-NiO mixed oxides nanoparticles were produced from a solution containing Zinc acetate, Mg and Ni nitrate by Solvothermal method. The calcination process of the ZnO-MgO and ZnO-NiO composites nanoparticles brought forth polycrystalline two-phase ZnO-MgO and ZnO-NiO nanoparticles of 40-80 nm in diameters. ZnO, MgO and NiO were crystallized into würtzite and rock salt structures, respectively. The optical properties of ZnO-MgO and ZnO-NiO nanoparticles were obtained by solid state UV and solid state florescent. The XRD, SEM and Raman spectroscopies of these nanoparticles were analyzed.

  19. Solvothermal synthesis, characterization and optical properties of ZnO, ZnO-MgO and ZnO-NiO, mixed oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Aslani, Alireza, E-mail: a.aslani@vru.ac.ir [Department of Chemistry, Faculty of Science, Vali-E-Asr University of Rafsanjan, Rafsanjan, PO Box: 77176 (Iran, Islamic Republic of); Arefi, Mohammad Reza [Islamic Azad University, Yazd Brunch, Young researchers Club, Yazd (Iran, Islamic Republic of); Babapoor, Aziz [Department of Chemical Engineering, Ahar Branch, Islamic Azad University, Ahar, PO Box: 54516 (Iran, Islamic Republic of); Amiri, Asghar; Beyki-Shuraki, Khalil [Department of Chemistry, Faculty of Science, Vali-E-Asr University of Rafsanjan, Rafsanjan, PO Box: 77176 (Iran, Islamic Republic of)

    2011-03-15

    ZnO-MgO and ZnO-NiO mixed oxides nanoparticles were produced from a solution containing Zinc acetate, Mg and Ni nitrate by Solvothermal method. The calcination process of the ZnO-MgO and ZnO-NiO composites nanoparticles brought forth polycrystalline two-phase ZnO-MgO and ZnO-NiO nanoparticles of 40-80 nm in diameters. ZnO, MgO and NiO were crystallized into wuertzite and rock salt structures, respectively. The optical properties of ZnO-MgO and ZnO-NiO nanoparticles were obtained by solid state UV and solid state florescent. The XRD, SEM and Raman spectroscopies of these nanoparticles were analyzed.

  20. ZnO nanodisk based UV detectors with printed electrodes.

    Science.gov (United States)

    Alenezi, Mohammad R; Alshammari, Abdullah S; Alzanki, Talal H; Jarowski, Peter; Henley, Simon John; Silva, S Ravi P

    2014-04-08

    The fabrication of highly functional materials for practical devices requires a deep understanding of the association between morphological and structural properties and applications. A controlled hydrothermal method to produce single crystal ZnO hexagonal nanodisks, nanorings, and nanoroses using a mixed solution of zinc sulfate (ZnSO4) and hexamethylenetetramine (HMTA) without the need of catalysts, substrates, or templates at low temperature (75 °C) is introduced. Metal-semiconductor-metal (MSM) ultraviolet (UV) detectors were fabricated based on individual and multiple single-crystal zinc oxide (ZnO) hexagonal nanodisks. High quality single crystal individual nanodisk devices were fabricated with inkjet-printed silver electrodes. The detectors fabricated show record photoresponsivity (3300 A/W) and external quantum efficiency (1.2 × 10(4)), which we attribute to the absence of grain boundaries in the single crystal ZnO nanodisk and the polarity of its exposed surface.

  1. Crystal-free Formation of Non-Oxide Optical Fiber

    Science.gov (United States)

    Nabors, Sammy A.

    2015-01-01

    Researchers at NASA Marshall Space Flight Center have devised a method for the creation of crystal-free nonoxide optical fiber preforms. Non-oxide fiber optics are extensively used in infrared transmitting applications such as communication systems, chemical sensors, and laser fiber guides for cutting, welding and medical surgery. However, some of these glasses are very susceptible to crystallization. Even small crystals can lead to light scatter and a high attenuation coefficient, limiting their usefulness. NASA has developed a new method of non-oxide fiber formation that uses axial magnetic fields to suppress crystallization. The resulting non-oxide fibers are crystal free and have lower signal attenuation rates than silica based optical fibers.

  2. Room temperature photoluminescence properties of ZnO nanorods grown by hydrothermal reaction

    Energy Technology Data Exchange (ETDEWEB)

    Iwan, S., E-mail: iwan-sugihartono@unj.ac.id [Jurusan Fisika, FMIPA-UNJ, Rawamangun, Jakarta (Indonesia); Prodi Ilmu Material, Departemen Fisika, FMIPA, Universitas Indonesia, Kampus UI Depok (Indonesia); Fauzia, Vivi [Prodi Ilmu Material, Departemen Fisika, FMIPA, Universitas Indonesia, Kampus UI Depok (Indonesia); Umar, A. A. [Institute of Microengineering and Nanoelectronics, Universiti Kebangsaan Malaysia, UKM Bangi, Selangor (Malaysia); Sun, X. W. [School of Electrical & Electronic Engineering, Nanyang Technological University, Nanyang Avenue (Singapore)

    2016-04-19

    Zinc oxide (ZnO) nanorods were fabricated by a hydrothermal reaction on silicon (Si) substrate at 95 °C for 6 hours. The ZnO seed layer was fabricated by depositing ZnO thin films on Si substrates by ultrasonic spray pyrolisis (USP). The annealing effects on crystal structure and optical properties of ZnO nanorods were investigated. The post-annealing treatment was performed at 800 °C with different environments. The annealed of ZnO nanorods were characterized by X-ray diffraction (XRD) and photoluminescence (PL) in order to analyze crystal structure and optical properties, respectively. The results show the orientations of [002], [101], [102], and [103] diffraction peaks were observed and hexagonal wurtzite structure of ZnO nanorods were vertically grown on Si substrates. The room temperature PL spectra show ultra-violet (UV) and visible emissions. The annealed of ZnO nanorods in vacuum condition (3.8 × 10{sup −3} Torr) has dominant UV emission. Meanwhile, non-annealed of ZnO nanorods has dominant visible emission. It was expected that the annealed of ZnO in vacuum condition suppresses the existence of native defects in ZnO nanorods.

  3. Annealing and surface conduction on Hydrogen peroxide treated bulk melt-grown, single crystal ZnO

    International Nuclear Information System (INIS)

    Mtangi, W.; Nel, J.M.; Auret, F.D.; Chawanda, A.; Diale, M.; Nyamhere, C.

    2012-01-01

    We report on the studies carried out on hydrogen peroxide treated melt-grown, bulk single crystal ZnO samples. Results show the existence of two shallow donors in the as-received ZnO samples with energy levels (37.8±0.3) meV that has been suggested as Zn i related and possibly H-complex related and (54.5±0.9) meV, which has been assigned to an Al-related donor. Annealing studies performed on the hydrogen peroxide treated samples reveal the existence of a conductive channel in the samples in which new energy levels have been observed, Zn vacancies, related to the Group I elements, X Zn . The surface donor volume concentration of the conductive channel was calculated from a theory developed by Look (2007) . Results indicate an increase in the surface volume concentration with increasing annealing temperature from 60×10 17 cm −3 at 200 °C to 4.37×10 18 cm -3 at 800 °C.

  4. Annealing and surface conduction on Hydrogen peroxide treated bulk melt-grown, single crystal ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Mtangi, W., E-mail: wilbert.mtangi@up.ac.za [University of Pretoria, Physics Department, Pretoria 0002 (South Africa); Nel, J.M.; Auret, F.D.; Chawanda, A.; Diale, M. [University of Pretoria, Physics Department, Pretoria 0002 (South Africa); Nyamhere, C. [Nelson Mandela Metropolitan University, Physics Department, P.O. Box 77000, Port Elizabeth 6031 (South Africa)

    2012-05-15

    We report on the studies carried out on hydrogen peroxide treated melt-grown, bulk single crystal ZnO samples. Results show the existence of two shallow donors in the as-received ZnO samples with energy levels (37.8{+-}0.3) meV that has been suggested as Zn{sub i} related and possibly H-complex related and (54.5{+-}0.9) meV, which has been assigned to an Al-related donor. Annealing studies performed on the hydrogen peroxide treated samples reveal the existence of a conductive channel in the samples in which new energy levels have been observed, Zn vacancies, related to the Group I elements, X{sub Zn}. The surface donor volume concentration of the conductive channel was calculated from a theory developed by Look (2007) . Results indicate an increase in the surface volume concentration with increasing annealing temperature from 60 Multiplication-Sign 10{sup 17} cm{sup -3} at 200 Degree-Sign C to 4.37 Multiplication-Sign 10{sup 18} cm{sup -3} at 800 Degree-Sign C.

  5. Spent oxide fuel regeneration by crystallization in molybdate melts

    International Nuclear Information System (INIS)

    Ustinov, O.A.; Sukhanov, L.P.; Yakunin, S.A.

    2006-01-01

    Paper describes a procedure to regenerate spent oxide fuel by its crystallization in molybdate melts. Paper presents the process procedures to regenerate spent fuel of both fast and thermal neutron reactors. One analyzes the advantages of the elaborated procedure [ru

  6. Synthesis, characterization and photocatalysis enhancement of Eu2O3-ZnO mixed oxide nanoparticles

    Science.gov (United States)

    Mohamed, W. S.; Abu-Dief, Ahmed M.

    2018-05-01

    Pure ZnO nanoparticles (NPs) and mixed Eu2O3 and ZnO NPs with different Eu2O3 ratios (5%, 10%, and 15%) were synthesized by a precipitation method under optimum conditions. The synthesized samples were characterized by means of X-ray diffraction, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and UV-vis diffuse reflectance spectroscopy. The as-synthesized ZnO NPs exhibit high phase purity and a highly crystalline wurtzite ZnO structure. The mixed Eu2O3 and ZnO NPs exhibit a Eu2O3 zinc blend phase in addition to the wurtzite phase of pure ZnO, confirming the high purity and good crystallinity of the as-synthesized samples. The high-purity formation of ZnO and Eu2O3 phases was confirmed by FTIR and Raman spectra. Microstructural analysis by SEM and TEM confirmed the sphere-like morphology with different particle sizes (29-40 nm) of the as-synthesized samples. The photocatalytic activities of pure ZnO NPs and mixed Eu2O3 and ZnO NPs for the degradation of methylene blue were evaluated under ultraviolet (UV) irradiation. The results show that Eu2O3 plays an important role in the enhancement of the photocatalytic properties of ZnO NPs. We found that mixed 5% Eu2O3 and ZnO NPs exhibit the highest photocatalytic activity (degradation efficiency of 96.5% after 180 min of UV irradiation) as compared with pure ZnO NPs (degradation efficiency of 80.3% after 180 min of UV irradiation). The increased photocatalytic activity of the optimum mixed Eu2O3 and ZnO NPs is due to the high crystallinity, high surface area with small particle size, and narrow energy gap.

  7. Persistent photoconductivity and photo-responsible defect in 30 MeV-electron irradiated single crystal ZnO

    International Nuclear Information System (INIS)

    Kuriyama, K.; Matsumoto, K.; Kushida, K.; Xu, Q.

    2010-01-01

    Persistent photoconductivity (PPC) in 30-MeV electron irradiated ZnO single crystals is studied by excitation using light emitting diodes (LEDs) with various wavelengths. The decay transient of the photoconductivity shows relaxation times in the range of a few ten days for the illumination at 90 K and a few hours at room temperature. An electron paramagnetic resonance (EPR) signal with g-value = 2.005 appears after illumination of blue LED, suggesting the transfer from the artificially introduced oxygen vacancy of 2+ charge state to the metastable + charge state. Once generated, the metastable state does not immediately decay into the 2+ charge state because of energetic barriers of ∼190 meV, supporting the mechanism of PPC proposed by Van de Walle.

  8. Nuclear reaction analysis of Ge ion-implanted ZnO bulk single crystals: The evaluation of the displacement in oxygen lattices

    Energy Technology Data Exchange (ETDEWEB)

    Kamioka, K.; Oga, T.; Izawa, Y. [College of Engineering and Research Center of Ion Beam Technology, Hosei University, Koganei, Tokyo 184-8584 (Japan); Kuriyama, K., E-mail: kuri@ionbeam.hosei.ac.jp [College of Engineering and Research Center of Ion Beam Technology, Hosei University, Koganei, Tokyo 184-8584 (Japan); Kushida, K. [Department of Arts and Science, Osaka Kyouiku University, Kashiwara, Osaka 582-8582 (Japan); Kinomura, A. [National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568 (Japan)

    2014-08-01

    The displacement of oxygen lattices in Ge ion-implanted ZnO bulk single crystals is studied by nuclear reaction analysis (NAR), photoluminescence (PL), and Van der Pauw methods. The Ge ion-implantation (net concentration: 2.6 × 10{sup 20} cm{sup −3}) into ZnO is performed using a multiple-step energy. The high resistivity of ∼10{sup 3} Ω cm in un-implanted samples remarkably decreased to ∼10{sup −2} Ω cm after implanting Ge-ion and annealing subsequently. NRA measurements of as-implanted and annealed samples suggest the existence of the lattice displacement of O atoms acting as acceptor defects. As O related defects still remain after annealing, these defects are not attributed to the origin of the low resistivity in 800 and 1000 °C annealed ZnO.

  9. Nuclear reaction analysis of Ge ion-implanted ZnO bulk single crystals: The evaluation of the displacement in oxygen lattices

    Science.gov (United States)

    Kamioka, K.; Oga, T.; Izawa, Y.; Kuriyama, K.; Kushida, K.; Kinomura, A.

    2014-08-01

    The displacement of oxygen lattices in Ge ion-implanted ZnO bulk single crystals is studied by nuclear reaction analysis (NAR), photoluminescence (PL), and Van der Pauw methods. The Ge ion-implantation (net concentration: 2.6 × 1020 cm-3) into ZnO is performed using a multiple-step energy. The high resistivity of ∼103 Ω cm in un-implanted samples remarkably decreased to ∼10-2 Ω cm after implanting Ge-ion and annealing subsequently. NRA measurements of as-implanted and annealed samples suggest the existence of the lattice displacement of O atoms acting as acceptor defects. As O related defects still remain after annealing, these defects are not attributed to the origin of the low resistivity in 800 and 1000 °C annealed ZnO.

  10. Boron doped ZnO embedded into reduced graphene oxide for electrochemical supercapacitors

    Science.gov (United States)

    Alver, Ü.; Tanrıverdi, A.

    2016-08-01

    In this work, reduced graphene oxide/boron doped zinc oxide (RGO/ZnO:B) composites were fabricated by a hydrothermal process and their electrochemical properties were investigated as a function of dopant concentration. First, boron doped ZnO (ZnO:B) particles was fabricated with different boron concentrations (5, 10, 15 and 20 wt%) and then ZnO:B particles were embedded into RGO sheets. The physical properties of sensitized composites were characterized by XRD and SEM. Characterization indicated that the ZnO:B particles with plate-like structure in the composite were dispersed on graphene sheets. The electrochemical properties of the RGO/ZnO:B composite were investigated through cyclic voltammetry, galvanostatic charge/discharge measurements in a 6 M KOH electrolyte. Electrochemical measurements show that the specific capacitance values of RGO/ZnO:B electrodes increase with increasing boron concentration. RGO/ZnO:B composite electrodes (20 wt% B) display the specific capacitance as high as 230.50 F/g at 5 mV/s, which is almost five times higher than that of RGO/ZnO (52.71 F/g).

  11. Random laser based on Rhodamine 6G (Rh6G doped poly(methyl methacrylate (PMMA films coating on ZnO nanorods synthesized by hydrothermal oxidation

    Directory of Open Access Journals (Sweden)

    Hua Zhang

    Full Text Available Random laser based on Rh6G doped PMMA thin films coating on ZnO nanorods synthesized by a simple hydrothermal oxidation method has been demonstrated. This kind of random laser medium is based on waveguide structure consisting of ZnO nanorods, Rh6G doped PMMA film and air. By controlling the time of hydrothermal oxidation reaction, wheat-like and hexagonal prism ZnO nanorods have been successfully fabricated. The emission spectra of these gain mediums based on different ZnO nanorods are different. The one based on wheat-like ZnO nanorods mainly exhibits amplified spontaneous emission, and the other one based on hexagonal prism ZnO nanorods shows random laser emission. The threshold of the random laser medium is about 73.8 μJ/pulse, and the full width at half maximum (FWHM is around 2.1 nm. The emission spectra measured at different detecting angles reveal that the output direction is strongly confined in ±30° by the waveguide effect. Our experiments demonstrate a promising method to achieve organic random laser medium. Keywords: Random laser, ZnO nanorods, Hydrothermal oxidation, Rhodamine 6G (Rh6G, Poly(methyl methacrylate (PMMA

  12. Thermal neutron detectors based on complex oxide crystals

    CERN Document Server

    Ryzhikov, V; Volkov, V; Chernikov, V; Zelenskaya, O

    2002-01-01

    The ways of improvement of spectrometric quality of CWO and GSO crystals have been investigated with the aim of their application in thermal neutron detectors based on radiation capture reactions. The efficiency of the neutron detection by these crystals was measured, and the obtained data were compared with the results for sup 6 LiI(Tl) crystals. It is shown that the use of complex oxide crystals and neutron-absorption filters for spectrometry of thermal and resonance neutrons could be a promising method in combination with computer data processing. Numerical calculations are reported for spectra of gamma-quanta due to radiation capture of the neutrons. To compensate for the gamma-background lines, we used a crystal pair of heavy complex oxides with different sensitivity to neutrons.

  13. 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.

  14. Oxidant-Dependent Thermoelectric Properties of Undoped ZnO Films by Atomic Layer Deposition

    KAUST Repository

    Kim, Hyunho; Wang, Zhenwei; Hedhili, Mohamed N.; Wehbe, Nimer; Alshareef, Husam N.

    2017-01-01

    , the maximum power factor for the water-based ZnO film is only 2.89 × 10 W m K at 746 K. Materials analysis results indicate that the oxygen vacancy levels in the water- and ozone-grown ZnO films are essentially the same, but the difference comes from Zn

  15. Recovery of thermal-degraded ZnO photodetector by embedding nano silver oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Zhan-Shuo [Institute of Microelectronics, Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan (China); Hung, Fei-Yi, E-mail: fyhung@mail.ncku.edu.tw [Institute of Nanotechnology and Microsystems Engineering, Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan (China); Chen, Kuan-Jen [Institute of Nanotechnology and Microsystems Engineering, Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan (China); The Instrument Center, National Cheng Kung University, Tainan 701, Taiwan (China); Chang, Shoou-Jinn [Institute of Microelectronics, Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan (China); Institute of Microelectronics and Department of Electrical Engineering, Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan (China); Hsieh, Wei-Kang; Liao, Tsai-Yu; Chen, Tse-Pu [Institute of Microelectronics, Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan (China)

    2013-08-15

    The degraded performance of annealed ZnO-based photodetector can be recovered by embedding Ag{sub 2}O nanoparticles resulted from the transformation of as-deposited Ag layer. After thermal treatment, the electrons were attracted at the interface between ZnO and Ag{sub 2}O. The excess Ag{sup +} ions form the cluster to incorporate into the interstitial sites of ZnO lattice to create a larger amount of lattice defects for the leakage path. The photo-current of ZnO film with Ag{sub 2}O nanoparticles is less than annealed ZnO film because the photo-induced electrons would flow into Ag{sub 2}O side. ZnO photodetector with the appropriate Ag{sub 2}O nanoparticles possesses the best rejection ratio.

  16. Non-isothermal cold crystallization kinetics of poly(3-hydoxybutyrate) filled with zinc oxide

    Energy Technology Data Exchange (ETDEWEB)

    Ries, Andreas, E-mail: ries750@yahoo.com.br [Electrical Engineering Department, Federal University of Paraíba, João Pessoa, PB 58051-900 (Brazil); Canedo, Eduardo L. [Materials Engineering Department, Federal University of Campina Grande, Campina Grande, PB 58429-900 (Brazil); Souto, Cícero R. [Electrical Engineering Department, Federal University of Paraíba, João Pessoa, PB 58051-900 (Brazil); Wellen, Renate M.R. [Materials Engineering Department, Federal University of Paraíba, João Pessoa, PB 58051-900 (Brazil)

    2016-08-10

    Highlights: • Non-isothermal cold crystallization kinetics of PHB filled with ZnO is presented. • Pseudo-Avrami model is best for describing an individual crystallization condition. • Mo model is allows to judge the kinetics of a condition untested in this work. • ZnO affects the kinetics irregularly. - Abstract: The non-isothermal cold crystallization kinetics of poly(3-hydroxybutyrate) (PHB) and PHB-ZnO composites, with ZnO content of 1%, 5% and 10% per weight, was investigated at different heating rates (5, 7.5, 10, 15, 20 and 30 °C/min) using differential scanning calorimetry. Both, Kissinger and Friedman activation energies predict correctly the slowest and fastest crystallizing composition. It was further found, that ZnO can neither be classified as a crystallization accelerator, nor as a crystallization inhibitor; its action is strongly concentration dependent. The empirical Pseudo-Avrami model has the best overall capability for fitting the experimental kinetic data. However, since the Pseudo-Avrami exponent was found to vary irregularly with heating rate and filler content, this model should not be applied for kinetic predictions of an arbitrary composition or an untested heating rate. In such cases, Mo's model should be used.

  17. Nitrogen grain-boundary passivation of In-doped ZnO transparent conducting oxide

    Science.gov (United States)

    Ali, D.; Butt, M. Z.; Coughlan, C.; Caffrey, D.; Shvets, I. V.; Fleischer, K.

    2018-04-01

    We have investigated the properties and conduction limitations of spray pyrolysis grown, low-cost transparent conducting oxide ZnO thin films doped with indium. We analyze the optical, electrical, and crystallographic properties as functions of In content with a specific focus on postgrowth heat treatment of these thin films at 320 ∘C in an inert, nitrogen atmosphere, which improves the films electrical properties considerably. The effect was found to be dominated by nitrogen-induced grain-boundary passivation, identified by a combined study using i n situ resistance measurement upon annealing, x-ray photoelectron spectroscopy, photoluminescence, and x-ray diffraction studies. We also highlight the chemical mechanism of morphologic and crystallographic changes found in films with high indium content. By optimizing growth conditions according to these findings, ZnO:In with a resistivity as low as 2 ×10 -3Ω cm , high optical quality (T ≈90 % ), and sheet resistance of 32 Ω /□ has been obtained without any need for postgrowth treatments.

  18. Microstructural and electrical characteristics of rare earth oxides doped ZnO varistor films

    Science.gov (United States)

    Jiao, Lei; Mei, Yunzhu; Xu, Dong; Zhong, Sujuan; Ma, Jia; Zhang, Lei; Bao, Li

    2018-02-01

    ZnO-Bi2O3 varistor films doped with two kinds of rare earth element oxides (Lu2O3 and Yb2O3) were prepared by the sol-gel method. The effects of Lu2O3/Yb2O3 doping on the microstructure and electrical characteristics of ZnO-Bi2O3 varistor films were investigated. All samples show a homogenized morphology and an improved nonlinear relationship between the electric field (E) and current density (I). Both Yb2O3 and Lu2O3 doping can decrease the grain size of ZnO-Bi2O3 varistor films and improve the electrical properties, which have a positive effect on the development of ZnO varistor ceramics. Yb2O3 doping significantly increases the dielectric constant at low frequency. 0.2 mol. % Yb2O3 doped ZnO-Bi2O3 varistor films exhibit the highest nonlinear coefficient (2.5) and the lowest leakage current (328 μA) among Lu2O3/Yb2O3 doped ZnO-Bi2O3 varistor films. Similarly, 0.1 mol. % Lu2O3 doping increases the nonlinear coefficient to 1.9 and decrease the leakage current to 462 μA.

  19. Solvothermal crystallization of nanocrystals of metal oxides

    International Nuclear Information System (INIS)

    Furukawa, S; Amino, H; Iwamoto, S; Inoue, M

    2008-01-01

    Solvothermal crystallization of the hydroxide gels obtained by hydrolysis of alkoxides (Zr, Ta, Nb, ln, Sn, Ti and Al) was examined. Nanocrystals having high surface areas (S BET > 170 m 2 g -1 ) were obtained except for the product derived from indium isopropoxide. The effect of water in organic solvent upon the crystallinity of the product was investigated. The increase in the activity of water by using high concentration of alkoxide or intentional addition of water to the solvothermal medium led to crystal growth of the products. In contrast, decrease in activity of water by adding ethylene glycol before solvothermal treatment caused a decrease in crystallinity of the product

  20. Solvothermal crystallization of nanocrystals of metal oxides

    Science.gov (United States)

    Furukawa, S.; Amino, H.; Iwamoto, S.; Inoue, M.

    2008-07-01

    Solvothermal crystallization of the hydroxide gels obtained by hydrolysis of alkoxides (Zr, Ta, Nb, ln, Sn, Ti and Al) was examined. Nanocrystals having high surface areas (SBET > 170 m2 g-1) were obtained except for the product derived from indium isopropoxide. The effect of water in organic solvent upon the crystallinity of the product was investigated. The increase in the activity of water by using high concentration of alkoxide or intentional addition of water to the solvothermal medium led to crystal growth of the products. In contrast, decrease in activity of water by adding ethylene glycol before solvothermal treatment caused a decrease in crystallinity of the product.

  1. Effect of zinc oxide (ZnO) nanoparticles on physiology and steviol glycosides production in micropropagated shoots of Stevia rebaudiana Bertoni.

    Science.gov (United States)

    Javed, Rabia; Usman, Muhammad; Yücesan, Buhara; Zia, Muhammad; Gürel, Ekrem

    2017-01-01

    This study aims to address the effects of different concentrations (0, 0.1, 1.0, 10, 100 or 1000 mg L -1 ) of engineered zinc oxide (ZnO) nanoparticles (34 nm in size) on growth parameters, steviol glycosides (rebaudioside A and stevioside) production and antioxidant activities in the tissue culture grown shoots of Stevia rebaudiana Bertoni. The highest percentage of shoot formation (89.6%) at 1 mg L -1 of ZnO nanoparticles concentration suggests a positive influence of ZnO nanoparticles on S. rebaudiana growth as compared to other treatments with or without ZnO nanoparticles. Additionally, HPLC results illustrate a significant enhancement of steviol glycosides (almost doubled as compared to the control) in micropropagated shoots grown under an oxidative stress of 1 mg L -1 of ZnO nanoparticles. This finding is further affirmed by an increased 2,2-diphenyl-1-picryl hydrazyl (DPPH) scavenging activity, total anti-oxidant capacity, total reducing power, total flavonoid content and total phenolic content, with an ascending oxidative pressure and generation of reactive oxygen species (ROS). However, the antioxidant activities, formation of secondary metabolites and the physiological parameters showed a sudden decline after crossing a threshold of 1 mg L -1 concentration of ZnO nanoparticles and falls to a minimum at 1000 mg L -1 , elucidating maximum phytotoxic effect of ZnO nanoparticles at this concentration. This is the first study evaluating both the favorable and adverse effects of ZnO nanoparticles employed to a highly valuable medicinal plant, S. rebaudiana. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  2. 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.

  3. Limits of ZnO Electrodeposition in Mesoporous Tin Doped Indium Oxide Films in View of Application in Dye-Sensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Christian Dunkel

    2014-04-01

    Full Text Available Well-ordered 3D mesoporous indium tin oxide (ITO films obtained by a templated sol-gel route are discussed as conductive porous current collectors. This paper explores the use of such films modified by electrochemical deposition of zinc oxide (ZnO on the pore walls to improve the electron transport in dye-sensitized solar cells (DSSCs. Mesoporous ITO film were dip-coated with pore sizes of 20–25 nm and 40–45 nm employing novel poly(isobutylene-b-poly(ethylene oxide block copolymers as structure-directors. After electrochemical deposition of ZnO and sensitization with the indoline dye D149 the films were tested as photoanodes in DSSCs. Short ZnO deposition times led to strong back reaction of photogenerated electrons from non-covered ITO to the electrolyte. ITO films with larger pores enabled longer ZnO deposition times before pore blocking occurred, resulting in higher efficiencies, which could be further increased by using thicker ITO films consisting of five layers, but were still lower compared to nanoporous ZnO films electrodeposited on flat ITO. The major factors that currently limit the application are the still low thickness of the mesoporous ITO films, too small pore sizes and non-ideal geometries that do not allow obtaining full coverage of the ITO surface with ZnO before pore blocking occurs.

  4. Limits of ZnO Electrodeposition in Mesoporous Tin Doped Indium Oxide Films in View of Application in Dye-Sensitized Solar Cells

    Science.gov (United States)

    Dunkel, Christian; von Graberg, Till; Smarsly, Bernd M.; Oekermann, Torsten; Wark, Michael

    2014-01-01

    Well-ordered 3D mesoporous indium tin oxide (ITO) films obtained by a templated sol-gel route are discussed as conductive porous current collectors. This paper explores the use of such films modified by electrochemical deposition of zinc oxide (ZnO) on the pore walls to improve the electron transport in dye-sensitized solar cells (DSSCs). Mesoporous ITO film were dip-coated with pore sizes of 20–25 nm and 40–45 nm employing novel poly(isobutylene)-b-poly(ethylene oxide) block copolymers as structure-directors. After electrochemical deposition of ZnO and sensitization with the indoline dye D149 the films were tested as photoanodes in DSSCs. Short ZnO deposition times led to strong back reaction of photogenerated electrons from non-covered ITO to the electrolyte. ITO films with larger pores enabled longer ZnO deposition times before pore blocking occurred, resulting in higher efficiencies, which could be further increased by using thicker ITO films consisting of five layers, but were still lower compared to nanoporous ZnO films electrodeposited on flat ITO. The major factors that currently limit the application are the still low thickness of the mesoporous ITO films, too small pore sizes and non-ideal geometries that do not allow obtaining full coverage of the ITO surface with ZnO before pore blocking occurs. PMID:28788618

  5. Controlled synthesis of thorium and uranium oxide nano-crystals

    International Nuclear Information System (INIS)

    Hudry, Damien; Apostolidis, Christos; Walter, Olaf; Gouder, Thomas; Courtois, Eglantine; Kubel, Christian; Meyer, Daniel

    2013-01-01

    Very little is known about the size and shape effects on the properties of actinide compounds. As a consequence, the controlled synthesis of well-defined actinide-based nano-crystals constitutes a fundamental step before studying their corresponding properties. In this paper, we report on the non-aqueous surfactant-assisted synthesis of thorium and uranium oxide nano-crystals. The final characteristics of thorium and uranium oxide nano-crystals can be easily tuned by controlling a few experimental parameters such as the nature of the actinide precursor and the composition of the organic system (e.g., the chemical nature of the surfactants and their relative concentrations). Additionally, the influence of these parameters on the outcome of the synthesis is highly dependent on the nature of the actinide element (thorium versus uranium). By using optimised experimental conditions, monodisperse isotropic uranium oxide nano-crystals with different sizes (4.5 and 10.7 nm) as well as branched nano-crystals (overall size ca. 5 nm), nano-dots (ca. 4 nm) and nano-rods (with ultra-small diameters of 1 nm) of thorium oxide were synthesised. (authors)

  6. Positron annihilation study of defects in electron-irradiated single crystal zinc oxide

    Science.gov (United States)

    To, C. K.; Yang, B.; Beling, C. D.; Fung, S.; Ling, C. C.; Gong, M.

    2011-01-01

    Pressurized melt grown zinc oxide (ZnO) single crystals purchased from Cermet Inc. were irradiated by 2MeV electrons with fluence of 6x1017cm-2. Isochronal annealing from 100°C-800°C was performed on the crystals under argon and air ambience. Variable Energy Doppler Broadening Spectroscopy (VEDBS) was carried out on both the as-grown and the irradiated samples at each annealing step. The migration, agglomeration and annealing of grown-in and irradiated-introduced defects were studied. It was observed that the grown-in vacancy-type defects concentration decreased at 300°C and 600 °C. For the irradiated sample annealed in argon, the positron trapping vacancy-type defect concentration decreased at 300°C and 600°C. Further annealing the as-grown and irradiated samples in argon increased the S parameter further. For the irradiated sample annealed in air, the vacancy-type defect concentration decreases at 300°C and 700°C.

  7. Positron annihilation study of defects in electron-irradiated single crystal zinc oxide

    Energy Technology Data Exchange (ETDEWEB)

    To, C K; Yang, B; Beling, C D; Fung, S; Ling, C C [Department of Physics, University of Hong Kong (Hong Kong); Gong, M, E-mail: sfung@hkucc.hku.h, E-mail: edwardto04@yahoo.com.h [Department of Physics, Sichuan University, Chengdu (China)

    2011-01-01

    Pressurized melt grown zinc oxide (ZnO) single crystals purchased from Cermet Inc. were irradiated by 2 MeV electrons with fluence of 6x10{sup 17}cm{sup -2}. Isochronal annealing from 100 deg. C - 800 deg. C was performed on the crystals under argon and air ambience. Variable Energy Doppler Broadening Spectroscopy (VEDBS) was carried out on both the as-grown and the irradiated samples at each annealing step. The migration, agglomeration and annealing of grown-in and irradiated-introduced defects were studied. It was observed that the grown-in vacancy-type defects concentration decreased at 300 deg. C and 600 deg. C. For the irradiated sample annealed in argon, the positron trapping vacancy-type defect concentration decreased at 300 deg. C and 600 deg. C. Further annealing the as-grown and irradiated samples in argon increased the S parameter further. For the irradiated sample annealed in air, the vacancy-type defect concentration decreases at 300 deg. C and 700 deg. C.

  8. Positron annihilation study of defects in electron-irradiated single crystal zinc oxide

    International Nuclear Information System (INIS)

    To, C K; Yang, B; Beling, C D; Fung, S; Ling, C C; Gong, M

    2011-01-01

    Pressurized melt grown zinc oxide (ZnO) single crystals purchased from Cermet Inc. were irradiated by 2 MeV electrons with fluence of 6x10 17 cm -2 . Isochronal annealing from 100 deg. C - 800 deg. C was performed on the crystals under argon and air ambience. Variable Energy Doppler Broadening Spectroscopy (VEDBS) was carried out on both the as-grown and the irradiated samples at each annealing step. The migration, agglomeration and annealing of grown-in and irradiated-introduced defects were studied. It was observed that the grown-in vacancy-type defects concentration decreased at 300 deg. C and 600 deg. C. For the irradiated sample annealed in argon, the positron trapping vacancy-type defect concentration decreased at 300 deg. C and 600 deg. C. Further annealing the as-grown and irradiated samples in argon increased the S parameter further. For the irradiated sample annealed in air, the vacancy-type defect concentration decreases at 300 deg. C and 700 deg. C.

  9. Application of walnut shell modified with Zinc Oxide (ZnO nanoparticles in removal of natural organic matters (NOMs from aqueous solution

    Directory of Open Access Journals (Sweden)

    ali naghizadeh

    2015-10-01

    Full Text Available Background & Aims of the Study: Natural organic matters (NOMs are a mixture of chemically complex polyelectrolytes produced mainly from the decomposition of plant and animal residues that are present in all surface and groundwater resources. This paper evaluates the aqueous NOMs adsorption efficiency on walnut shell modified with Zinc Oxide (ZnO. Materials & Methods: This study examined the feasibility of removing NOMs from aqueous solutions using walnut shell modified with ZnO. The effects of NOMs concentration, modified walnut shell with ZnO dosage, and pH on adsorption of NOMs by modified walnut shell with ZnO were evaluated. Results: The adsorption capacities of modified walnut shell with ZnO in the best conditions were 37.93 mg/g. The results also demonstrated that adsorption capacity of NOMs on modified walnut shell with ZnO was higher in lower pHs due to significantly high electrostatic attraction exists between the positively charged surface of the adsorbent and negatively charged NOMs. And finally adsorption capacity decreases as adsorbent dose increase. Conclusion: Walnut shell modified with ZnO can be proposed as a natural adsorbent in the removal of NOMs from aqueous solutions

  10. Unique Crystal Orientation of Poly(ethylene oxide) Thin Films by Crystallization Using a Thermal Gradient

    DEFF Research Database (Denmark)

    Gbabode, Gabin; Delvaux, Maxime; Schweicher, Guillaume

    2017-01-01

    Poly(ethylene oxide), (PEO), thin films of different thicknesses (220, 450, and 1500 nm) and molecular masses (4000, 8000, and 20000 g/mol) have been fabricated by spin-coating of methanol solutions onto glass substrates. All these samples have been recrystallized from the melt using a directional......, to significantly decrease the distribution of crystal orientation obtained after crystallization using the thermal gradient technique....

  11. Recent progress on doped ZnO nanostructures for visible-light photocatalysis

    International Nuclear Information System (INIS)

    Samadi, Morasae; Zirak, Mohammad; Naseri, Amene; Khorashadizade, Elham; Moshfegh, Alireza Z.

    2016-01-01

    Global environmental pollution and energy supply demand have been regarded as important concerns in recent years. Metal oxide semiconductor photocatalysts is a promising approach to apply environmental remediation as well as fuel generation from water splitting and carbon dioxide reduction. ZnO nanostructures have been shown promising photocatalytic activities due to their non-toxic, inexpensive, and highly efficient nature. However, its wide band gap hinders photo-excitation for practical photocatalytic applications under solar light as an abundant, clean and safe energy source. To overcome this barrier, many strategies have been developed in the last decade to apply ZnO nanostructured photocatalysts under visible light. In this review, we have classified different approaches to activate ZnO as a photocatalyst in visible-light spectrum. Utilization of various nonmetals, transition metals and rare-earth metals for doping in ZnO crystal lattice to create visible-light-responsive doped ZnO photocatalysts is discussed. Generation of localized energy levels within the gap in doped ZnO nanostructures has played an important role in effective photocatalytic reaction under visible-light irradiation. The effect of dopant type, ionic size and its concentration on the crystal structure, electronic property and morphology of doped ZnO with a narrower band gap is reviewed systematically. Finally, a comparative study is performed to evaluate two classes of metals and nonmetals as useful dopants for ZnO nanostructured photocatalysts under visible light. - Highlights: • Metals and nonmetals used as a dopant to shift ZnO band gap toward visible-light. • Modification of electronic structure played a crucial role in doped ZnO activity. • Correlation between dopant's characteristics and ZnO visible activity was reviewed. • Photo-degradation of doped ZnO was studied and compared for different dopants.

  12. Recent progress on doped ZnO nanostructures for visible-light photocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    Samadi, Morasae; Zirak, Mohammad [Department of Physics, Sharif University of Technology, P.O. Box 11555-9161, Tehran (Iran, Islamic Republic of); Naseri, Amene [Institute for Nanoscience and Nanotechnology, Sharif University of Technology, P.O. Box 11365-8639, Tehran (Iran, Islamic Republic of); Khorashadizade, Elham [Department of Physics, Sharif University of Technology, P.O. Box 11555-9161, Tehran (Iran, Islamic Republic of); Moshfegh, Alireza Z., E-mail: moshfegh@sharif.edu [Department of Physics, Sharif University of Technology, P.O. Box 11555-9161, Tehran (Iran, Islamic Republic of); Institute for Nanoscience and Nanotechnology, Sharif University of Technology, P.O. Box 11365-8639, Tehran (Iran, Islamic Republic of)

    2016-04-30

    Global environmental pollution and energy supply demand have been regarded as important concerns in recent years. Metal oxide semiconductor photocatalysts is a promising approach to apply environmental remediation as well as fuel generation from water splitting and carbon dioxide reduction. ZnO nanostructures have been shown promising photocatalytic activities due to their non-toxic, inexpensive, and highly efficient nature. However, its wide band gap hinders photo-excitation for practical photocatalytic applications under solar light as an abundant, clean and safe energy source. To overcome this barrier, many strategies have been developed in the last decade to apply ZnO nanostructured photocatalysts under visible light. In this review, we have classified different approaches to activate ZnO as a photocatalyst in visible-light spectrum. Utilization of various nonmetals, transition metals and rare-earth metals for doping in ZnO crystal lattice to create visible-light-responsive doped ZnO photocatalysts is discussed. Generation of localized energy levels within the gap in doped ZnO nanostructures has played an important role in effective photocatalytic reaction under visible-light irradiation. The effect of dopant type, ionic size and its concentration on the crystal structure, electronic property and morphology of doped ZnO with a narrower band gap is reviewed systematically. Finally, a comparative study is performed to evaluate two classes of metals and nonmetals as useful dopants for ZnO nanostructured photocatalysts under visible light. - Highlights: • Metals and nonmetals used as a dopant to shift ZnO band gap toward visible-light. • Modification of electronic structure played a crucial role in doped ZnO activity. • Correlation between dopant's characteristics and ZnO visible activity was reviewed. • Photo-degradation of doped ZnO was studied and compared for different dopants.

  13. Effects of the annealing duration of the ZnO buffer layer on structural and optical properties of ZnO rods grown by a hydrothermal process

    Energy Technology Data Exchange (ETDEWEB)

    Shin, C.M.; Lee, J.Y.; Heo, J.H.; Park, J.H.; Kim, C.R. [Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Obang-dong, Gimhae, Gyeongnam 621-749 (Korea, Republic of); Ryu, H., E-mail: hhryu@inje.ac.kr [Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Obang-dong, Gimhae, Gyeongnam 621-749 (Korea, Republic of); Chang, J.H. [Major of Nano Semiconductor, Korea Maritime University, 1 Dongsam-dong, Yeongdo-Ku, Busan 606-791 (Korea, Republic of); Son, C.S. [Department of Electronic Materials Engineering, Silla University, Gwaebeop-dong, Sasang-gu, Busan 617-736 (Korea, Republic of); Lee, W.J. [Department of Nano Engineering, Dong-Eui University, 995 Eomgwangno, Busanjin-gu, Busan 614-714 (Korea, Republic of); Tan, S.T. [Institute of Microelectronics, 11 Science Park Road, Science Park II, Singapore 117685 (Singapore); Zhao, J.L. [School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore); Sun, X.W. [Institute of Microelectronics, 11 Science Park Road, Science Park II, Singapore 117685 (Singapore); School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore)

    2009-07-30

    In this study, the effects of the annealing duration of a zinc oxide (ZnO) buffer layer on structural and optical properties of ZnO rods grown by a hydrothermal process are discussed. A ZnO buffer layer was deposited on p-type Si (1 1 1) substrates by the metal organic chemical vapor deposition (MOCVD) method. After that, ZnO rods were grown on the ZnO-buffer/Si (1 1 1) substrate by a hydrothermal process. In order to determine the optimum annealing duration of the buffer layer for the growth of ZnO rods, durations ranging from 0.5 to 30 min were tried. The morphology and crystal structure of the ZnO/ZnO-buffer/Si (1 1 1) were measured by field emission scanning electron microscopy (FE-SEM) and x-ray diffraction (XRD). The optical properties were investigated by photoluminescence (PL) measurement.

  14. Thermo-electric oxidization of iron in lithium niobate crystals

    International Nuclear Information System (INIS)

    Falk, Matthias

    2007-01-01

    Lithium niobate crystals (LiNbO 3 ) are a promising material for nonlinear-optical applications like frequency conversion to generate visible light, e.g., in laser displays, but their achievable output power is greatly limited by the ''optical damage'', i.e., light-induced refractive-index changes caused by excitation of electrons from iron impurities and the subsequent retrapping in unilluminated areas of the crystal. The resulting space-charge fields modify the refractive indices due to the electro-optic effect. By this ''photorefractive effect'' the phase-matching condition, i.e., the avoidance of destructive interference between light generated at different crystal positions due to the dispersion of the fundamental wave and the converted wave, is disturbed critically above a certain light intensity threshold. The influence of annealing treatments conducted in the presence of an externally applied electric field (''thermo-electric oxidization'') on the valence state of iron impurities and thereby on the optical damage is investigated. It is observed that for highly iron-doped LiNbO 3 crystals this treatment leads to a nearly complete oxidization from Fe 2+ to Fe 3+ indicated by the disappearance of the absorption caused by Fe 2+ . During the treatment an absorption front forms that moves through the crystal. The absorption in the visible as well as the electrical conductivity are decreased by up to five orders of magnitude due to this novel treatment. The ratio of the Fe 2+ concentration to the total iron concentration - a measure for the strength of the oxidization - is in the order of 10 -6 for oxidized crystals whereas it is about 10 -1 for untreated samples. Birefringence changes are observed at the absorption front that are explained by the removal of hydrogen and lithium ions from the crystal that compensate for the charges of the also removed electrons from Fe 2+ . A microscopic shock-wave model is developed that explains the observed absorption front by

  15. A prototype Ultraviolet Light Sensor based on ZnO Nanoparticles/Graphene Oxide Nanocomposite Using Low Temperature Hydrothermal Method

    International Nuclear Information System (INIS)

    Al-Fandi, M; Oweis, R; Khwailah, H; Al-Hattami, S; Al-Shawwa, E; Albiss, B A; Al-Akhras, M-Ali; Qutaish, H; AlZoubi, T

    2015-01-01

    A new prototype UV nanosensor using ZnO nanoparticles (NPs)/graphene oxide (GO) nanocomposite (ZnO-NP/GO) on silicon substrate is reported in this paper. The hybrid nanocomposite structure has been developed by an optimized hydrothermal process at low growth temperature (∼50 °C). In this hybrid nanosensor, the ZnO nanoparticles act as UV- absorbing and charge carrier generating material, while graphene with its superior electrical conductivity has been used as a charge transporting material. Various nanostructure characterization techniques were intensively utilized including SEM, EDX, XRD, FTIR and UV-VIS. Also, the I-V measurement was employed to evaluate the prototype sensor. The morphological SEM analysis showed that the ZnO-NPs (average diameter of 20 nm) were dispersed evenly on the GO sheets. As well, the EDX spectra confirmed the exact chemical composition of the intended structure. The room temperature UV-VIS measurement revealed an enhanced optical absorption of UV-light at an absorption band centered on 375 nm. The improved optical and electrical properties were observed at an optimum relative concentration of 1:10. Under UV light illumination, the measured I-V characteristic of the prototype detector exhibited a considerable photocurrent increase of the ZnO-NP/GO nanocomposite compared to pristine ZnO nanostructure. These results can be promising for future enhanced UV- sensing applications. (paper)

  16. Functional doped metal oxide films. Zinc oxide (ZnO) as transparent conducting oxide (TCO) titanium dioxide (TiO{sub 2}) as thermographic phosphor and protective coating

    Energy Technology Data Exchange (ETDEWEB)

    Nebatti Ech-Chergui, Abdelkader

    2011-07-29

    Metalorganic chemical vapor deposition (MOCVD) was used in the present work. Un-doped and Al-doped ZnO films were developed using two reactors: Halogen Lamp Reactor (HLR) (a type of Cold Wall Reactor) and Hot Wall Reactor (HWR), and a comparison was made between them in terms of the film properties. Zinc acetylacetonate was used as precursor for ZnO films while aluminum acetylacetonate was used for doping. The amount of Al doping can be controlled by varying the gas flow rate. Well ordered films with aluminum content between 0 and 8 % were grown on borosilicate glass and silicon. The films obtained are 0.3 to 0.5 {mu}m thick, highly transparent and reproducible. The growth rate of ZnO films deposited using HLR is less than HWR. In HLR, the ZnO films are well oriented along c-axis ((002) plane). ZnO films are commonly oriented along the c-axis due to its low surface free energy. On the other hand, the HWR films are polycrystalline and with Al doping these films aligned along the a-axis ((100) plane) which is less commonly observed. The best films were obtained with the HLR method showing a minimum electrical resistivity of 2.4 m{omega}cm and transmittance of about 80 % in the visible range. The results obtained for Al-doped films using HLR are promising to be used as TCOs. The second material investigated in this work was un-doped and doped titanium dioxide (TiO{sub 2}) films- its preparation and characterization. It is well known that thermographic phosphors can be used as an optical method for the surface temperature measurement. For this application, the temperature-dependent luminescence properties of europium (III)-doped TiO{sub 2} thin films were studied. It was observed that only europium doped anatase films show the phosphorescence. Rutile phase do not show phosphorescence. The films were prepared by the sol-gel method using the dip coating technique. The structures of the films were determined by X-ray diffraction (XRD). The excitation and the emission

  17. TiN/Al2O3/ZnO gate stack engineering for top-gate thin film transistors by combination of post oxidation and annealing

    Science.gov (United States)

    Kato, Kimihiko; Matsui, Hiroaki; Tabata, Hitoshi; Takenaka, Mitsuru; Takagi, Shinichi

    2018-04-01

    Control of fabrication processes for a gate stack structure with a ZnO thin channel layer and an Al2O3 gate insulator has been examined for enhancing the performance of a top-gate ZnO thin film transistor (TFT). The Al2O3/ZnO interface and the ZnO layer are defective just after the Al2O3 layer formation by atomic layer deposition. Post treatments such as plasma oxidation, annealing after the Al2O3 deposition, and gate metal formation (PMA) are promising to improve the interfacial and channel layer qualities drastically. Post-plasma oxidation effectively reduces the interfacial defect density and eliminates Fermi level pinning at the Al2O3/ZnO interface, which is essential for improving the cut-off of the drain current of TFTs. A thermal effect of post-Al2O3 deposition annealing at 350 °C can improve the crystalline quality of the ZnO layer, enhancing the mobility. On the other hand, impacts of post-Al2O3 deposition annealing and PMA need to be optimized because the annealing can also accompany the increase in the shallow-level defect density and the resulting electron concentration, in addition to the reduction in the deep-level defect density. The development of the interfacial control technique has realized the excellent TFT performance with a large ON/OFF ratio, steep subthreshold characteristics, and high field-effect mobility.

  18. A novel fabrication methodology for sulfur-doped ZnO nanorods as an active photoanode for improved water oxidation in visible-light regime

    Science.gov (United States)

    Khan, A.; Ahmed, M. I.; Adam, A.; Azad, A.-M.; Qamar, M.

    2017-02-01

    Incorporation of foreign moiety in the lattice of semiconductors significantly alters their optoelectronic behavior and opens a plethora of new applications. In this paper, we report the synthesis of sulfur-doped zinc oxide (S-doped ZnO) nanorods by reacting ZnO nanorods with diammonium sulfide in vapor phase. Microscopic investigation revealed that the morphological features, such as, the length (2-4 μm) and width (100-250 nm) of the original hexagonal ZnO nanorods remained intact post-sulfidation. X-ray photoelectron spectroscopy analysis of the sulfide sample confirmed the incorporation of sulfur into ZnO lattice. The optical measurements suggested the extension of absorption threshold into visible region upon sulfidation. Photoelectrochemical (PEC) activities of pure and S-doped ZnO nanorods were compared for water oxidation in visible light (λ > 420 nm), which showed several-fold increment in the performance of S-doped ZnO sample; the observed amelioration in the PEC activity was rationalized in terms of preferred visible light absorption and low resistance of sulfide sample, as evidenced by optical and electrochemical impedance spectroscopy.

  19. Controlling the electrical properties of ZnO films by forming zinc and oxide bridges by a plasma and electron-assisted process

    Directory of Open Access Journals (Sweden)

    Norihiro Shimoi

    2012-06-01

    Full Text Available A new method to produce electrically steady ZnO films without any heating process has been developed by using plasma and electron beams to facilitate bonding between the metallic component and the oxygen on coated ZnO films. Both plasma atmosphere and electron beams can function as sources of nonequilibrium bonding energy, forming bridges between the zinc present in the zinc complex and the oxygen in the ZnO particles to construct a zinc-oxide thin film. Our results confirm that it is possible to achieve low conductive characteristics by controlling the acceleration voltage of electrons used to irradiate the ZnO coating. The electrically steady films fabricated have various potential applications, being particularly well-suited to electrical devices on a plastic medium.

  20. Controlling the electrical properties of ZnO films by forming zinc and oxide bridges by a plasma and electron-assisted process

    Energy Technology Data Exchange (ETDEWEB)

    Shimoi, Norihiro; Tanaka, Yasumitsu [Graduate School of Environmental Studies, Tohoku University, 6-6-20 Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan); Harada, Takamitsu [Sendai Technology Center, Consumer-Professional and Devices Group, Sony Corporation, 3-4-1 Sakuragi, Tagajo 985-0842 (Japan); Tanaka, Shun-ichiro [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2012-06-15

    A new method to produce electrically steady ZnO films without any heating process has been developed by using plasma and electron beams to facilitate bonding between the metallic component and the oxygen on coated ZnO films. Both plasma atmosphere and electron beams can function as sources of nonequilibrium bonding energy, forming bridges between the zinc present in the zinc complex and the oxygen in the ZnO particles to construct a zinc-oxide thin film. Our results confirm that it is possible to achieve low conductive characteristics by controlling the acceleration voltage of electrons used to irradiate the ZnO coating. The electrically steady films fabricated have various potential applications, being particularly well-suited to electrical devices on a plastic medium.

  1. Growth and characterization of nonpolar (10-10) ZnO transparent conductive oxide on semipolar (11–22) GaN-based light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ki-Wook; Choi, Nak-Jung [Department of Nano-Optical Engineering, Korea Polytechnic University, Siheung, Gyeonggi-do, 429-839 (Korea, Republic of); Kim, Kyoung-Bo [Department of Metallurgical and Materials Engineering, Inha Technical College, Incheon, 402-752 (Korea, Republic of); Kim, Moojin [Department of Renewable Energy, Jungwon University, 85, Munmu-ro, Goesan-eup, Goesan-gun, Chungbuk, 367-805 (Korea, Republic of); Lee, Sung-Nam, E-mail: snlee@kpu.ac.kr [Department of Nano-Optical Engineering, Korea Polytechnic University, Siheung, Gyeonggi-do, 429-839 (Korea, Republic of)

    2016-05-05

    We have grown thin films of nonpolar m-plane (10-10) ZnO on a semipolar (11–22) GaN template by atomic layer deposition (ALD) at low growth temperatures (<200 °C). The surface morphology of the ZnO film is found to be an arrowhead-like structure, which is a typical surface structure of the semipolar (11–22) GaN films. On increasing the growth temperature of the ZnO films, the concentration and mobility of the charge carriers in the ZnO film are increased. However, the optical transmittance decreases with an increase in the growth temperature. Based on these results, we have fabricated semipolar (11–22) GaN-based light-emitting diodes (LEDs) with nonpolar m-plane ZnO film as a transparent conductive oxide (TCO) to improve the light extraction efficiency. In spite of a decrease in the optical transmittance, the operation voltage of semipolar (11–22) GaN-based LEDs is found to decrease with an increase in the growth temperature, which might be due to the improvements in the electrical properties and current spreading effect, resulting in an increase in the optical output power. - Highlights: • Polarity control of ZnO film grown in m-/c-sapphire and semipolar GaN template. • Achievement of high quality nonpolar m-plane ZnO flims on semipolar (11–22) GaN template. • The simultaneous improvements of carrier concentration and mobility in the nonpolar ZnO TCO flims. • Nonpolar ZnO TCO increases current spreading length and light output power of semipolar GaN-LED.

  2. Structural, optical and magnetic characterization of Ru doped ZnO nanorods

    International Nuclear Information System (INIS)

    Kumar, Sanjeev; Kaur, Palvinder; Chen, C.L.; Thangavel, R.; Dong, C.L.; Ho, Y.K.; Lee, J.F.; Chan, T.S.; Chen, T.K.; Mok, B.H.; Rao, S.M.; Wu, M.K.

    2014-01-01

    Graphical abstract: Ruthenium (Ru = 0%, 1% and 2%) doped nano-crystalline zinc oxide (ZnO) nanorods were synthesized by using well-known sol–gel technique. X-ray diffraction (XRD) results show that Ru (0%, 1% and 2%) doped ZnO nanorods crystallized in the wurtzite structure having space group C 3v (P6 3 mc). Williamson and Hall plot reveal that in the nanoscale dimensions, incorporation of Ru induced the tensile strain in ZnO host matrix. Photoluminescence (PL) and Raman studies of Ru doped ZnO nanorods show the formation of singly ionized oxygen vacancies which may account for the observed room temperature ferromagnetism (RTFM) in 2% Ru doped ZnO. X-ray absorption spectroscopy (XAS) reveals that Ru replace the Zn atoms in the host lattice and maintain the crystal symmetry with slightly lattice distortion. Highlights: • Ru doped ZnO nanorods crystallized in the wurtzite structure having space group C 3v (P6 3 mc). • PL and Raman studies show the formation of singly ionized oxygen vacancies in 2% Ru doped ZnO. • XAS reveals that Ru replace the Zn atoms in the host lattice with slightly lattice distortion. • Doping of Ru in ZnO nanostructures gives rise to RTFM ordering. -- Abstract: Ruthenium (Ru = 0%, 1% and 2%) doped nano-crystalline zinc oxide (ZnO) nanorods were synthesized by using well-known sol–gel technique. X-ray diffraction (XRD) results show that Ru (0%, 1% and 2%) doped ZnO nanorods crystallized in the wurtzite structure having space group C 3v (P6 3 mc). Williamson and Hall plot reveal that in the nanoscale dimensions, incorporation of Ru induced the tensile strain in ZnO host matrix. Photoluminescence (PL) and Raman studies of Ru doped ZnO nanorods show the formation of singly ionized oxygen vacancies which may account for the observed room temperature ferromagnetism (RTFM) in 2% Ru doped ZnO. X-ray absorption spectroscopy (XAS) reveals that Ru replace the Zn atoms in the host lattice and maintain the crystal symmetry with slightly lattice

  3. Some clues about the interphase reaction between ZnO and MnO2 oxides

    International Nuclear Information System (INIS)

    Rubio-Marcos, F.; Quesada, A.; Garcia, M.A.; Banares, M.A.; Fierro, J.L.G.; Martin-Gonzalez, M.S.; Costa-Kraemer, J.L.; Fernandez, J.F.

    2009-01-01

    Raman spectroscopy is used to evidence both the nature of the interphase reaction between ZnO and MnO 2 particles and its kinetic evolution. Zn cations migrate from the ZnO grains during oxygen vacancies formation process and diffuse into the MnO 2 particles leading to an interphase region with an intermediate valence Mn +3 -O-Mn +4 . Large amounts of desorbed Zn cations promote the formation of ZnMn 2 O 4 structure, in addition to the intermediate valence state. The system evolves towards complete formation of the spinel phase at higher thermal treatment times. The reactivity of the ZnO plays an important role in the formation of this interphase. Low-reactivity ZnO powder, in which the oxygen vacancies are previously produced, shows a stabilization of the intermediate valence state with very limited formation of the spinel phase. A clear correlation between the amount of the intermediate state interphase and the magnetic properties has been established. - Graphical abstract: Recently new room temperature interphase magnetism has been reported to appear in ZnO-MnO 2 system. Raman spectroscopy is used to evidence both the nature of the interphase reaction and the kinetic. The interphase evolved towards complete formation of the spinel phase. The reactivity of the ZnO plays an important role in the formation of this interphase. Finally, a clear correlation between the amount of the intermediate valence state and the interphase magnetic properties has been established.

  4. Bulk ZnO: Current Status, Challenges, and Prospects

    Science.gov (United States)

    2009-04-01

    von Wenckstern, H. Schmidt, M. Lorenz, and M. Grundmann, “Defects in virgin and N+-implanted ZnO single crystals studied by positron annihilation...characterization, and device applications of semiconductor and complex oxide thin films. He is a co-author of more than 50 papers in referred...REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < 1 Abstract— Rediscovered in the last decade, zinc oxide

  5. Enhancement in photo-electrochemical efficiency by reducing recombination rate in branched TiO2 nanotube array on functionalizing with ZnO micro crystals

    Science.gov (United States)

    Boda, Muzaffar Ahmad; Ashraf Shah, Mohammad

    2018-06-01

    In this study, branched TiO2 nanotube array were fabricated through electrochemical anodization process at constant voltage using third generation electrolyte. On account of morphological advantage, these nanotubes shows significant enhancement in photo-electrochemical property than compact or conventional titania nanotube array. However, their photo-electrochemical efficiency intensifies on coating with ZnO micro-crystals. ZnO coated branched TiO2 nanotube array shows a photocurrent density of 27.8 mA cm‑2 which is 1.55 times the photocurrent density (17.2 mA cm‑2) shown by bare branched titania nanotubes. The significant enhancement in photocurrent density shown by the resulting ZnO/TiO2 hybrid structure is attributed to suppression in electron–hole recombination phenomenon by offering smooth pathway to photo generated excitons on account of staggered band edge positions in individual semiconductors.

  6. Platinum single crystal electrodes for the electrocatalysis of methane oxidation

    Directory of Open Access Journals (Sweden)

    Mayara Munaretto

    2011-03-01

    Full Text Available The main objective of this paper is to characterize the voltammetric profiles of platinum single crystals of low Miller indexes Pt(100 and Pt(110 and study their catalytic activities on the oxidation of methane. In this way, it was developed a metallic surface modified by presence of other metal oxide, which presents catalytic activity for this reaction. It is well known that the electrooxidation of methane (CH4 leads mainly to the formation of CO2 and H2O, however, the oxidation can also lead to the formation of CO, a reaction intermediate that has strong interaction with metal surfaces, such as platinum. This molecule tends to accumulate on the platinum surface and to passive it, due to the self-poisoning, decreasing its catalytic activity. Therefore, the main aim of this work was the development of a platinum electrode modified by deposition of titanium oxide, which presented electrocatalytic properties for the oxidation of methane.

  7. Dominant ultraviolet-blue photoluminescence of ZnO embedded into synthetic opal

    International Nuclear Information System (INIS)

    Abrarov, S.M.; Yuldashev, Sh.U.; Kim, T.W.; Lee, S.B.; Kwon, H.Y.; Kang, T.W.

    2005-01-01

    The temperature-dependent photoluminescence (PL) characteristics of zinc oxide (ZnO) embedded into the voids of synthetic opal were studied. ZnO was infiltrated into opal from aqueous solution with zinc nitrate precursor followed by thermal annealing. The PL spectra of the ZnO powder exhibit very high and broad emission peaks in the green region due to crystal defects, such as oxygen vacancies and zinc ion interstitials. In contrast to the PL spectra of ZnO powder, nanocrystals of ZnO embedded into the voids of FCC packed opal matrix exhibit dominant ultraviolet (UV)-blue and rapidly decreasing green PL emissions with decreasing temperature. The temperature-dependent PL characteristics show that the green band suppression in the ZnO nanocrystals is due to the influence of photonic crystal. The infiltration of nanoparticles into synthetic opal may be used for the fabrication of polycrystalline ZnO with dominant UV-blue PL. These results indicate that the luminescent materials embedded into photonic crystal may be promising for the fabrication of the RGB pixels in full-color displays

  8. Aloe vera mediated hydrothermal synthesis of reduced graphene oxide decorated ZnO nanocomposite: Luminescence and antioxidant properties

    Science.gov (United States)

    Kavyashree, D.; Nagabhushana, H.; Ananda Kumari, R.; Basavaraj, R. B.; Suresh, D.; Daruka Prasad, B.; Sharma, S. C.

    2016-05-01

    A zinc oxide/reduced graphene oxide (ZnO/rGO) nanocomposite was fabricated by facile hydrothermal route using Aloe vera gel as surfactant. The PL emission spectrum of the ZnO/rGO composite consists of four peaks at around 380, 394, 449 and 465nm. The PL intensity is found to diminish in ZnO-rGO composites rather than in pure ZnO, which was attributed to electron transfer from ZnO to rGO. A single intense glow curve was recorded in rGo-ZnO for a dose range of 1-8kGy. The TL response curve of rGO-ZnO is found to be a simple glow curve structure, linear dependence over a dose range of 1-8kGy. The obtained ZnO/rGO composite could provide a facile and eco-friendly method for the development of graphene-based nanocomposites with promising applications in radiation dosimetry and antioxidant activities.

  9. Effect of replacement of tin doped indium oxide (ITO) by ZnO: analysis of environmental impact categories

    Science.gov (United States)

    Ziemińska-Stolarska, Aleksandra; Barecka, Magda; Zbiciński, Ireneusz

    2017-10-01

    Abundant use of natural resources is doubtlessly one of the greatest challenges of sustainable development. Process alternatives, which enable sustainable manufacturing of valuable products from more accessible resources, are consequently required. One of examples of limited resources is Indium, currently broadly used for tin doped indium oxide (ITO) for production of transparent conductive films (TCO) in electronics industry. Therefore, candidates for Indium replacement, which would offer as good performance as the industrial state-of-the-art technology based on ITO are widely studied. However, the environmental impact of new layers remains unknown. Hence, this paper studies the environmental effect of ITO replacement by zinc oxide (ZnO) by means life cycle assessment (LCA) methodology. The analysis enables to quantify the environmental impact over the entire period of life cycle of products—during manufacturing, use phase and waste generation. The analysis was based on experimental data for deposition process. Further, analysis of different impact categories was performed in order to determine specific environmental effects related to technology change. What results from the analysis, is that ZnO is a robust alternative material for ITO replacement regarding environmental load and energy efficiency of deposition process which is also crucial for sustainable TCO layer production.

  10. Copper doping of ZnO crystals by transmutation of {sup 64}Zn to {sup 65}Cu: An electron paramagnetic resonance and gamma spectroscopy study

    Energy Technology Data Exchange (ETDEWEB)

    Recker, M. C.; McClory, J. W., E-mail: John.McClory@afit.edu; Holston, M. S.; Golden, E. M.; Giles, N. C. [Department of Engineering Physics, Air Force Institute of Technology, Wright-Patterson Air Force Base, Ohio 45433 (United States); Halliburton, L. E. [Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506 (United States)

    2014-06-28

    Transmutation of {sup 64}Zn to {sup 65}Cu has been observed in a ZnO crystal irradiated with neutrons. The crystal was characterized with electron paramagnetic resonance (EPR) before and after the irradiation and with gamma spectroscopy after the irradiation. Major features in the gamma spectrum of the neutron-irradiated crystal included the primary 1115.5 keV gamma ray from the {sup 65}Zn decay and the positron annihilation peak at 511 keV. Their presence confirmed the successful transmutation of {sup 64}Zn nuclei to {sup 65}Cu. Additional direct evidence for transmutation was obtained from the EPR of Cu{sup 2+} ions (where {sup 63}Cu and {sup 65}Cu hyperfine lines are easily resolved). A spectrum from isolated Cu{sup 2+} (3d{sup 9}) ions acquired after the neutron irradiation showed only hyperfine lines from {sup 65}Cu nuclei. The absence of {sup 63}Cu lines in this Cu{sup 2+} spectrum left no doubt that the observed {sup 65}Cu signals were due to transmuted {sup 65}Cu nuclei created as a result of the neutron irradiation. Small concentrations of copper, in the form of Cu{sup +}-H complexes, were inadvertently present in our as-grown ZnO crystal. These Cu{sup +}-H complexes are not affected by the neutron irradiation, but they dissociate when a crystal is heated to 900 °C. This behavior allowed EPR to distinguish between the copper initially in the crystal and the copper subsequently produced by the neutron irradiation. In addition to transmutation, a second major effect of the neutron irradiation was the formation of zinc and oxygen vacancies by displacement. These vacancies were observed with EPR.

  11. Copper doping of ZnO crystals by transmutation of 64Zn to 65Cu: An electron paramagnetic resonance and gamma spectroscopy study

    International Nuclear Information System (INIS)

    Recker, M. C.; McClory, J. W.; Holston, M. S.; Golden, E. M.; Giles, N. C.; Halliburton, L. E.

    2014-01-01

    Transmutation of 64 Zn to 65 Cu has been observed in a ZnO crystal irradiated with neutrons. The crystal was characterized with electron paramagnetic resonance (EPR) before and after the irradiation and with gamma spectroscopy after the irradiation. Major features in the gamma spectrum of the neutron-irradiated crystal included the primary 1115.5 keV gamma ray from the 65 Zn decay and the positron annihilation peak at 511 keV. Their presence confirmed the successful transmutation of 64 Zn nuclei to 65 Cu. Additional direct evidence for transmutation was obtained from the EPR of Cu 2+ ions (where 63 Cu and 65 Cu hyperfine lines are easily resolved). A spectrum from isolated Cu 2+ (3d 9 ) ions acquired after the neutron irradiation showed only hyperfine lines from 65 Cu nuclei. The absence of 63 Cu lines in this Cu 2+ spectrum left no doubt that the observed 65 Cu signals were due to transmuted 65 Cu nuclei created as a result of the neutron irradiation. Small concentrations of copper, in the form of Cu + -H complexes, were inadvertently present in our as-grown ZnO crystal. These Cu + -H complexes are not affected by the neutron irradiation, but they dissociate when a crystal is heated to 900 °C. This behavior allowed EPR to distinguish between the copper initially in the crystal and the copper subsequently produced by the neutron irradiation. In addition to transmutation, a second major effect of the neutron irradiation was the formation of zinc and oxygen vacancies by displacement. These vacancies were observed with EPR.

  12. Copper doping of ZnO crystals by transmutation of 64Zn to 65Cu: An electron paramagnetic resonance and gamma spectroscopy study

    Science.gov (United States)

    Recker, M. C.; McClory, J. W.; Holston, M. S.; Golden, E. M.; Giles, N. C.; Halliburton, L. E.

    2014-06-01

    Transmutation of 64Zn to 65Cu has been observed in a ZnO crystal irradiated with neutrons. The crystal was characterized with electron paramagnetic resonance (EPR) before and after the irradiation and with gamma spectroscopy after the irradiation. Major features in the gamma spectrum of the neutron-irradiated crystal included the primary 1115.5 keV gamma ray from the 65Zn decay and the positron annihilation peak at 511 keV. Their presence confirmed the successful transmutation of 64Zn nuclei to 65Cu. Additional direct evidence for transmutation was obtained from the EPR of Cu2+ ions (where 63Cu and 65Cu hyperfine lines are easily resolved). A spectrum from isolated Cu2+ (3d9) ions acquired after the neutron irradiation showed only hyperfine lines from 65Cu nuclei. The absence of 63Cu lines in this Cu2+ spectrum left no doubt that the observed 65Cu signals were due to transmuted 65Cu nuclei created as a result of the neutron irradiation. Small concentrations of copper, in the form of Cu+-H complexes, were inadvertently present in our as-grown ZnO crystal. These Cu+-H complexes are not affected by the neutron irradiation, but they dissociate when a crystal is heated to 900 °C. This behavior allowed EPR to distinguish between the copper initially in the crystal and the copper subsequently produced by the neutron irradiation. In addition to transmutation, a second major effect of the neutron irradiation was the formation of zinc and oxygen vacancies by displacement. These vacancies were observed with EPR.

  13. Fano resonance in anodic aluminum oxide based photonic crystals.

    Science.gov (United States)

    Shang, Guo Liang; Fei, Guang Tao; Zhang, Yao; Yan, Peng; Xu, Shao Hui; Ouyang, Hao Miao; Zhang, Li De

    2014-01-08

    Anodic aluminum oxide based photonic crystals with periodic porous structure have been prepared using voltage compensation method. The as-prepared sample showed an ultra-narrow photonic bandgap. Asymmetric line-shape profiles of the photonic bandgaps have been observed, which is attributed to Fano resonance between the photonic bandgap state of photonic crystal and continuum scattering state of porous structure. And the exhibited Fano resonance shows more clearly when the sample is saturated ethanol gas than air-filled. Further theoretical analysis by transfer matrix method verified these results. These findings provide a better understanding on the nature of photonic bandgaps of photonic crystals made up of porous materials, in which the porous structures not only exist as layers of effective-refractive-index material providing Bragg scattering, but also provide a continuum light scattering state to interact with Bragg scattering state to show an asymmetric line-shape profile.

  14. 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.

  15. The early stages of oxidation of magnesium single crystal surfaces

    International Nuclear Information System (INIS)

    Hayden, B.E.; Schweizer, E.; Koetz, R.; Bradshaw, A.M.

    1981-01-01

    The early stages of oxidation of Mg(001) and Mg(100) single crystal surfaces at 300 K have been investigated by LEED, ELS, work function and ellipsometric measurements. A sharp decrease in work function on both surfaces during the first 12 L exposure indicates the incorporation of oxygen in the earliest stages of the interaction. The incorporated oxygen on Mg(001) gives rise to a broadening of the integral order LEED spots for an exposure 3 L. (orig.)

  16. Crystal structure of the uranyl-oxide mineral rameauite

    Czech Academy of Sciences Publication Activity Database

    Plášil, Jakub; Škoda, R.; Čejka, J.; Bourgoin, V.; Boulliard, J.C.

    2016-01-01

    Roč. 28, č. 5 (2016), s. 959-967 ISSN 0935-1221 R&D Projects: GA MŠk LO1603 EU Projects: European Commission(XE) CZ.2.16/3.1.00/24510 Institutional support: RVO:68378271 Keywords : rameauite * uranyl-oxide hydroxy-hydrate * crystal structure * Raman spectrum Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.362, year: 2016

  17. Selective Oxidation of Styrene to Benzaldehyde by Co-Ag Codoped ZnO Catalyst and H2O2 as Oxidant

    Directory of Open Access Journals (Sweden)

    Abderrazak Aberkouks

    2018-01-01

    Full Text Available Various ratio of Co-Ag supported on ZnO have been evaluated in the selective catalytic oxidation of styrene to benzaldehyde, using H2O2 as an oxidant. The catalysts were prepared by a sol-gel process and were characterized using XRD, FT-IR, TG-DTG, BET, and SEM/EDX. The performance of the prepared catalyst was investigated under different parameters such as solvent, temperature, substrate/oxidant molar ratios, reaction time, and doping percent. The Zn1−x−yAgxCoyO catalysts exhibit a good activity and a high selectivity towards benzaldehyde (95% with the formation of only 5% of acetophenone.

  18. Lyotropic liquid crystal based on zinc oxide nanoparticles obtained by microwave solvothermal synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Omelchenko, M.M., E-mail: momelchenko@chem.uw.edu.pl [Department of Chemistry, Warsaw University, Al. Zwirki i Wigury 101, 02-089, Warsaw (Poland); Wojnarowicz, J. [Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, Warsaw, 01-142 (Poland); Salamonczyk, M. [Department of Chemistry, Warsaw University, Al. Zwirki i Wigury 101, 02-089, Warsaw (Poland); Lojkowski, W. [Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, Warsaw, 01-142 (Poland)

    2017-05-01

    Abstract: The ZnO nanoparticles, obtained by microwave solvothermal synthesis, were used for the liquid crystal phase preparation. The structure of the material was investigated by X-ray diffraction (XRD), helium pycnometry, specific surface area (SSA), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM). The stability of aqueous suspensions was monitored by Multiple Light Scattering (MLS) technique and the average agglomerate size in suspensions was obtained by dynamic light scattering (DLS) technique. The lyotropic columnar hexagonal phase was formed by doping ZnO nanoparticles into the cetylpiridinium chloride/water/hexanol system. The structure of this phase was confirmed by x-ray diffraction. The luminescent properties of the LC phase were compared with properties of ZnO nanoparticles isolated in solution and analogues lyotropic system without nanoparticles.

  19. High-performance zno transistors processed via an aqueous carbon-free metal oxide precursor route at temperatures between 80-180 °c

    KAUST Repository

    Lin, Yenhung; Faber, Hendrik; Zhao, Kui; Wang, Qingxiao; Amassian, Aram; McLachlan, Martyn A.; Anthopoulos, Thomas D.

    2013-01-01

    An aqueous and carbon-free metal-oxide precursor route is used in combination with a UV irradiation-assisted low-temperature conversion method to fabricate low-voltage ZnO transistors with electron mobilities exceeding 10 cm2/Vs at temperatures <

  20. The sorption of silver by poorly crystallized manganese oxides

    Science.gov (United States)

    Anderson, B.J.; Jenne, E.A.; Chao, T.T.

    1973-01-01

    The sorption of silver by poorly crystallized manganese oxides was studied using synthesized samples of three members of the manganous manganite (birnessite) group, of different chemical composition and crystallinity, and a poorly organized ??-MnO2. All four oxides sorbed significant quantities of silver. The manganous manganites showed the greatest sorption (up to 0.5 moles silver/mole MnOx at pH 7) while the ??-MnO2 showed the least (0.3 moles silver/ mole MnOx at pH 7). Sorption of silver was adequately described by the Langmuir equation over a considerable concentration range. The relationship failed at low pH values and high equilibrium silver concentrations. The sorption capacity showed a direct relationship with pH. However, the rate of increase of sorption capacity decreased at the higher pH values. Silver sorption maxima. were not directly related to surface area but appeared to vary with the amount of occluded sodium and potassium present in the manganese oxide. The important processes involved in the uptake of silver by the four poorly crystallized manganese oxides ara considered to be surface exchange for manganese, potassium and sodium as well as exchange for structural manganese, potassium and sodium. ?? 1973.

  1. Photoluminescence properties of ZnO films grown on InP by thermally oxidizing metallic Zn films

    CERN Document Server

    Chen, S J; Zhang, J Y; Lu, Y M; Shen, D Z; Fan, X W

    2003-01-01

    Photoluminescence (PL) properties of ZnO films grown on (001) InP substrates by thermal oxidization of metallic Zn films, in which oxygen vacancies and interstitial Zn ions are compensated by P ions diffusing from (001) InP substrates, are investigated. X-ray diffraction spectra indicate that P ions have diffused into the Zn films and chemically combined with Zn ions to form Zn sub 3 P sub 2. Intense free exciton emission dominates the PL spectra of ZnO films with very weak deep-level emission. Low-temperature PL spectra at 79 K are dominated by neutral-donor bound exciton emission at 3.299 eV (I sub 4) with a linewidth of 17.3 meV and neutral-acceptor bound exciton emission at 3.264 eV. The free exciton emission increases with increasing temperature and eventually dominates the emission spectrum for temperature higher than 170 K. Furthermore, the visible emission around 2.3 eV correlated with oxygen deficiencies and interstitial Zn defects was quenched to a remarkable degree by P diffusing from InP substrate...

  2. Photoluminescence properties of ZnO films grown on InP by thermally oxidizing metallic Zn films

    International Nuclear Information System (INIS)

    Chen, S J; Liu, Y C; Zhang, J Y; Lu, Y M; Shen, D Z; Fan, X W

    2003-01-01

    Photoluminescence (PL) properties of ZnO films grown on (001) InP substrates by thermal oxidization of metallic Zn films, in which oxygen vacancies and interstitial Zn ions are compensated by P ions diffusing from (001) InP substrates, are investigated. X-ray diffraction spectra indicate that P ions have diffused into the Zn films and chemically combined with Zn ions to form Zn 3 P 2 . Intense free exciton emission dominates the PL spectra of ZnO films with very weak deep-level emission. Low-temperature PL spectra at 79 K are dominated by neutral-donor bound exciton emission at 3.299 eV (I 4 ) with a linewidth of 17.3 meV and neutral-acceptor bound exciton emission at 3.264 eV. The free exciton emission increases with increasing temperature and eventually dominates the emission spectrum for temperature higher than 170 K. Furthermore, the visible emission around 2.3 eV correlated with oxygen deficiencies and interstitial Zn defects was quenched to a remarkable degree by P diffusing from InP substrates

  3. ZnO nanowire-based nano-floating gate memory with Pt nanocrystals embedded in Al{sub 2}O{sub 3} gate oxides

    Energy Technology Data Exchange (ETDEWEB)

    Yeom, Donghyuk; Kang, Jeongmin; Lee, Myoungwon; Jang, Jaewon; Yun, Junggwon; Jeong, Dong-Young; Yoon, Changjoon; Koo, Jamin; Kim, Sangsig [Department of Electrical Engineering and Institute for Nano Science, Korea University, Seoul 136-701 (Korea, Republic of)], E-mail: sangsig@korea.ac.kr

    2008-10-01

    The memory characteristics of ZnO nanowire-based nano-floating gate memory (NFGM) with Pt nanocrystals acting as the floating gate nodes were investigated in this work. Pt nanocrystals were embedded between Al{sub 2}O{sub 3} tunneling and control oxide layers deposited on ZnO nanowire channels. For a representative ZnO nanowire-based NFGM with embedded Pt nanocrystals, a threshold voltage shift of 3.8 V was observed in its drain current versus gate voltage (I{sub DS}-V{sub GS}) measurements for a double sweep of the gate voltage, revealing that the deep effective potential wells built into the nanocrystals provide our NFGM with a large charge storage capacity. Details of the charge storage effect observed in this memory device are discussed in this paper.

  4. ZnO nanowire-based nano-floating gate memory with Pt nanocrystals embedded in Al2O3 gate oxides

    International Nuclear Information System (INIS)

    Yeom, Donghyuk; Kang, Jeongmin; Lee, Myoungwon; Jang, Jaewon; Yun, Junggwon; Jeong, Dong-Young; Yoon, Changjoon; Koo, Jamin; Kim, Sangsig

    2008-01-01

    The memory characteristics of ZnO nanowire-based nano-floating gate memory (NFGM) with Pt nanocrystals acting as the floating gate nodes were investigated in this work. Pt nanocrystals were embedded between Al 2 O 3 tunneling and control oxide layers deposited on ZnO nanowire channels. For a representative ZnO nanowire-based NFGM with embedded Pt nanocrystals, a threshold voltage shift of 3.8 V was observed in its drain current versus gate voltage (I DS -V GS ) measurements for a double sweep of the gate voltage, revealing that the deep effective potential wells built into the nanocrystals provide our NFGM with a large charge storage capacity. Details of the charge storage effect observed in this memory device are discussed in this paper

  5. Atomic absorption photometry of excess Zn in ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Lott, K.; Shinkarenko, S.; Tuern, L. [Department of Materials Science, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn (Estonia); Kirsanova, T.; Grebennik, A.; Vishnjakov, A. [Department of Physical Chemistry, D. Mendelejev University of Chemical Technology of Russia, Miusskaya Sq. 9, 125047 Moscow (Russian Federation)

    2005-02-01

    Zn excess in ZnO is built up automatically at high temperatures. Excess Zn in hydrothermally grown ZnO single crystals were investigated by the atomic absorption photometry (AAP) method. To determine the excess zinc in ZnO samples, the AAP of zinc vapour was used in the conditions of solid-vapour equilibrium. Zn AAP allowed to eliminate excess Zn connected differentially in ZnO samples. To fix Zn non-stoichiometry, all the ZnO samples tested were previously heat treated at temperature interval from 850 to 900 C and at fixed Zn vapour pressures from 0.1 to 0.9 of saturated zinc vapour pressure at given treatment temperature. The analysis of temperature dependence of zinc vapour pressure indicated that the impurity metals take active role in the determination of non-stoichiometric zinc. The impurities Mn, Fe, Co, Ni and Cu form oxides which will reduce during annealing in Zn vapor up to metals form. During AAP measurement in optical cuvette, these metals react with ZnO and give additional Zn vapor pressure. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Crystallization process and magnetic properties of amorphous iron oxide nanoparticles

    International Nuclear Information System (INIS)

    Phu, N D; Luong, N H; Chau, N; Hai, N H; Ngo, D T; Hoang, L H

    2011-01-01

    This paper studied the crystallization process, phase transition and magnetic properties of amorphous iron oxide nanoparticles prepared by the microwave heating technique. Thermal analysis and magnetodynamics studies revealed many interesting aspects of the amorphous iron oxide nanoparticles. The as-prepared sample was amorphous. Crystallization of the maghemite γ-Fe 2 O 3 (with an activation energy of 0.71 eV) and the hematite α-Fe 2 O 3 (with an activation energy of 0.97 eV) phase occurred at around 300 deg. C and 350 deg. C, respectively. A transition from the maghemite to the hematite occurred at 500 deg. C with an activation energy of 1.32 eV. A study of the temperature dependence of magnetization supported the crystallization and the phase transformation. Raman shift at 660 cm -1 and absorption band in the infrared spectra at 690 cm -1 showed the presence of disorder in the hematite phase on the nanoscale which is supposed to be the origin of the ferromagnetic behaviour of that antiferromagnetic phase.

  7. Ternary Oxides in the TiO2-ZnO System as Efficient Electron-Transport Layers for Perovskite Solar Cells with Efficiency over 15.

    Science.gov (United States)

    Yin, Xiong; Xu, Zhongzhong; Guo, Yanjun; Xu, Peng; He, Meng

    2016-11-02

    Perovskite solar cells, which utilize organometal-halide perovskites as light-harvesting materials, have attracted great attention due to their high power conversion efficiency (PCE) and potentially low cost in fabrication. A compact layer of TiO 2 or ZnO is generally applied as electron-transport layer (ETL) in a typical perovskite solar cell. In this study, we explored ternary oxides in the TiO 2 -ZnO system to find new materials for the ETL. Compact layers of titanium zinc oxides were readily prepared on the conducting substrate via spray pyrolysis method. The optical band gap, valence band maximum and conduction band minimum of the ternary oxides varied significantly with the ratio of Ti to Zn, surprisingly, in a nonmonotonic way. When a zinc-rich ternary oxide was applied as ETL for the device, a PCE of 15.10% was achieved, comparable to that of the device using conventional TiO 2 ETL. Interestingly, the perovskite layer deposited on the zinc-rich ternary oxide is stable, in sharp contrast with that fabricated on a ZnO layer, which will turn into PbI 2 readily when heated. These results indicate that potentially new materials with better performance can be found for ETL of perovskite solar cells in ternary oxides, which deserve more exploration.

  8. Crystal habit dependent quantum confined photoluminescence of zinc oxide nanostructures

    International Nuclear Information System (INIS)

    Arellano, Ian Harvey J.; Payawan, Leon Jr. M.; Sarmago, Roland V.

    2008-01-01

    Diverse zinc oxide crystal habits namely wire, rods, tubes, whiskers and tetrapods were synthesized via hydrothermal and carbothermal reduction routes. A vapor current induced regionalization in the carbothermal synthesis lead to the isolation of these crystal habits for characterization. The surface morphology of the nanostructures was analyzed via field emission scanning electron microscopy (FESEM). The morphology and crystallinity of the as-synthesized nanostructure architectural motifs were related to their photoluminescence (PL). The photoluminescence at 157 nm was taken using F2 excimer laser and a crystal habit dependent response was observed. X-ray diffraction (XRD) analyses were conducted to deduce the degree of crystallinity showing results consistent with the excitonic emission at the band edge and visible emission at the electron-hole recombination sites. The presence of minimal crystal defects which gave the green emission was supported by energy dispersive spectroscopy (EDS) data. Transmission spectroscopy for the tetrapods exhibited an interesting PL reduction associated with high-energy deep traps in the nanostructures. Furthermore, some intensity dependent characteristics were deduced indicating quantum confined properties of these nano structures. (author)

  9. Synthesis, structural and optical properties of ZnO spindle/reduced graphene oxide composites with enhanced photocatalytic activity under visible light irradiation

    Science.gov (United States)

    Prabhu, S.; Pudukudy, M.; Sohila, S.; Harish, S.; Navaneethan, M.; Navaneethan, D.; Ramesh, R.; Hayakawa, Y.

    2018-05-01

    In the present work, spindle-shaped ZnO and reduced graphene oxide sheets were successfully synthesized by a hydrothermal method and then ZnO/r-GO composite was prepared by a direct solution mixing method. Various characterization results confirmed the interior and surface decoration of spindle-shaped ZnO on the reduced graphene oxide sheets. The phase formation, crystalline structure, morphology, surface states and optical properties were characterized using Powder X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR) and UV-Vis spectroscopy. The X-ray diffraction analysis showed the formation of the hexagonal wurtzite crystalline structure of ZnO with high crystalline quality. The band gap of the ZnO/r-GO composite was found to be low (3.03eV) compared to the band gap of spindle shaped ZnO (3.13 eV), as calculated from optical studies. The spindle-like morphology of the single crystalline ZnO was clearly shown in the electron microscopic images. The chemical bonding and surface states of the samples were studied using XPS measurement. Moreover, a possible growth mechanism for the ZnO spindle was proposed. The catalytic activity of the as-synthesized samples was evaluated for the photodegradation of methylene blue under visible light irradiation. Among the synthesized samples, the ZnO/r-GO composite showed higher degradation efficiency of 93% and successfully reused for four consecutive run without any activity loss.

  10. ZnO nanorods/polyaniline heterojunctions for low-power flexible light sensors

    Energy Technology Data Exchange (ETDEWEB)

    Talib, Rawnaq A.; Abdullah, M.J. [Nano-Optoelectronics Research and Technology (NOR) Laboratory, School of Physics, Universiti Sains Malaysia, 11800, Penang (Malaysia); Al-Salman, Husam S. [Department of Physics, College of Science, University of Basrah, Basrah (Iraq); Mohammad, Sabah M. [Nano-Optoelectronics Research and Technology (NOR) Laboratory, School of Physics, Universiti Sains Malaysia, 11800, Penang (Malaysia); Allam, Nageh K., E-mail: nageh.allam@aucegypt.edu [Energy Materials Laboratory (EML), School of Sciences and Engineering, The American University in Cairo, New Cairo, 11835 (Egypt)

    2016-09-15

    Zinc oxide nanorods (ZnO NRs) were directly grown on p-type polyaniline (PAni)/polyethylene terephthalate (PET) using chemical bath deposition method at low temperature. Field emission scanning electron microscopy and X-ray diffraction techniques were used to study the morphology and structure of the fabricated films. The resulted ZnO NRs are hexagonal and grew vertically on the PAni surface in the (002) direction along the c-axis. The compressive strain, Raman and photoluminescence measurements confirmed the high-quality crystal structure of the formed ZnO NRs with no damage of the PAni surface. The photodetector made using ZnO NRs/PAni junction showed a sensitivity of 85% and a quantum efficiency of 12.3% at 5 V. - Highlights: • ZnO NRs/polyaniline p-n junction photodetectors were fabricated on flexible substrates. • The fabricated ZnO NRs grew along the (002) direction. • The fabricated ZnO NRs have low compressive strain. • The ZnO NRs/PAni junction showed a high sensitivity of 85%. • The photodetectors showed quantum efficiency as high as 12%.

  11. Hybrid nanostructure heterojunction solar cells fabricated using vertically aligned ZnO nanotubes grown on reduced graphene oxide.

    Science.gov (United States)

    Yang, Kaikun; Xu, Congkang; Huang, Liwei; Zou, Lianfeng; Wang, Howard

    2011-10-07

    Using reduced graphene oxide (rGO) films as the transparent conductive coating, inorganic/organic hybrid nanostructure heterojunction photovoltaic devices have been fabricated through hydrothermal synthesis of vertically aligned ZnO nanorods (ZnO-NRs) and nanotubes (ZnO-NTs) on rGO films followed by the spin casting of a poly(3-hexylthiophene) (P3HT) film. The data show that larger interfacial area in ZnO-NT/P3HT composites improves the exciton dissociation and the higher electrode conductance of rGO films helps the power output. This study offers an alternative to manufacturing nanostructure heterojunction solar cells at low temperatures using potentially low cost materials.

  12. Optical study of gamma irradiated sodium metaphosphate glasses containing divalent metal oxide MO (ZnO or CdO

    Directory of Open Access Journals (Sweden)

    E. Nabhan

    Full Text Available Sodium metaphosphate glasses containing divalent metal oxide, ZnO or CdO with composition 50 P2O5 – (50 − x Na2O – x MO (ZnO, or CdO where x = 0, 10, 20 (mol% were prepared by conventional melt method. UV/visible spectroscopy and FTIR spectroscopy are measured before and after exposing to successive gamma irradiation doses (5–80 kGy. The optical absorption spectra results of the samples before irradiation reveal a strong UV absorption band at (∼230 nm which is related to unavoided iron impurities. The effects of gamma irradiation on the optical spectral properties of the various glasses have been compared. From the optical absorption spectral data, the optical band gap is evaluated. The main structural groups and the influence of both divalent metal oxide and gamma irradiation effect on the structural vibrational groups are realized through IR spectroscopy. The FTIR spectra of γ-irradiated samples are characterized by the stability of the number and position for the main characteristic band of phosphate groups. To better understood the structural changes during γ-irradiation, a deconvolution of FTIR spectra in the range 650–1450 cm−1 is made. The FTIR deconvolution results found evidence that, the changes occurring after gamma irradiation have been related to irradiation induced structural defects and compositional changes. Keywords: Sodium metaphosphate glass, UV–visible spectra, IR spectra, Deconvolution, Optical band gap, Gamma ray

  13. Oxidative Stress and Nano-Toxicity Induced by TiO2 and ZnO on WAG Cell Line.

    Directory of Open Access Journals (Sweden)

    Akhilesh Dubey

    Full Text Available Metallic nanoparticles are widely used in cosmetics, food products and textile industry. These particles are known to cause respiratory toxicity and epithelial inflammation. They are eventually released to aquatic environment necessitating toxicity studies in cells from respiratory organs of aquatic organisms. Hence, we have developed and characterized a new cell line, WAG, from gill tissue of Wallago attu for toxicity assessment of TiO2 and ZnO nanoparticles. The efficacy of the cell line as an in vitro system for nanoparticles toxicity studies was established using electron microscopy, cytotoxicity assays, genotoxicity assays and oxidative stress biomarkers. Results obtained with MTT assay, neutral red uptake assay and lactate dehydrogenase assay showed acute toxicity to WAG cells with IC50 values of 25.29 ± 0.12, 34.99 ± 0.09 and 35.06 ± 0.09 mg/l for TiO2 and 5.716 ± 0.1, 3.160 ± 0.1 and 5.57 ± 0.12 mg/l for ZnO treatment respectively. The physicochemical properties and size distribution of nanoparticles were characterized using electron microscopy with integrated energy dispersive X-ray spectroscopy and Zetasizer. Dose dependent increase in DNA damage, lipid peroxidation and protein carbonylation along with a significant decrease in activity of Superoxide Dismutase, Catalase, total Glutathione levels and total antioxidant capacity with increasing concentration of exposed nanoparticles indicated that the cells were under oxidative stress. The study established WAG cell line as an in vitro system to study toxicity mechanisms of nanoparticles on aquatic organisms.

  14. Indium Gallium Zinc Oxide: Phase Formation and Crystallization Kinetics during Millisecond Laser Spike Annealing

    Science.gov (United States)

    Lynch, David Michael

    Flat panel displays have become ubiquitous, enabling products from highresolution cell phones to ultra-large television panels. Amorphous silicon (a- Si) has been the industry workhorse as the active semiconductor in pixeladdressing transistors due to its uniformity and low production costs. However, a-Si can no longer support larger and higher-resolution displays, and new materials with higher electron mobilities are required. Amorphous indium gallium zinc oxide (a-IGZO), which retains the uniformity and low cost of amorphous films, has emerged as a viable candidate due to its enhanced transport properties. However, a-IGZO devices suffer from long-term instabilities--the origins of which are not yet fully understood--causing a drift in switching characteristics over time and affecting product lifetime. More recently, devices fabricated from textured nanocrystalline IGZO, termed c-axis aligned crystalline (CAAC), have demonstrated superior stability. Unfortunately, little is known regarding the phase formation and crystallization kinetics of either the CAAC structure or in the broader ternary IGZO system. Crystallinity and texture of CAAC IGZO films deposited by RF reactive sputtering were studied and characterized over a wide range of deposition conditions. The characteristic CAAC (0 0 9) peak at 2theta = 30° was observed by X-ray diffraction, and nanocrystalline domain texture was determined using a general area detector diffraction system (GADDS). Highly ordered CAAC films were obtained near the InGaZnO4 composition at a substrate temperature of 310 °C and in a 10%O2/90% Ar sputtering ambient. High-resolution transmission electron microscopy (HRTEM) confirmed the formation of CAAC and identified 2-3 nm domains coherently aligned over large ranges extending beyond the field of view (15 nm x 15 nm). Cross-section HRTEM of the CAAC/substrate interface shows formation of an initially disordered IGZO layer prior to CAAC formation, suggesting a nucleation mechanism

  15. Growth of high-density ZnO nanorods on wood with enhanced photostability, flame retardancy and water repellency

    Science.gov (United States)

    Kong, Lizhuo; Tu, Kunkun; Guan, Hao; Wang, Xiaoqing

    2017-06-01

    Zinc oxide (ZnO) nanorod arrays were successfully assembled on the wood surface in situ via a two-step process consisting of formation of ZnO seeds and subsequent crystal growth under hydrothermal conditions at a low temperature. The morphology and crystalline structure of the formed ZnO nanorods were studied by field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). Highly dense and uniform arrays of ZnO nanorods with well-defined hexagonal facets were generated on the wood surface by tuning the concentration of the ZnO growth solution during the hydrothermal treatment. Accelerated weathering tests indicated that the assembled ZnO nanorod arrays were highly protective against UV radiation and greatly enhanced the photostability of the coated wood. Meanwhile, the ZnO nanorod-coated wood can withstand continuous exposure to flame with only minor smoldering in contrast with the pristine wood catching fire easily and burning rapidly. Moreover, when further modified with low-surface-energy stearic acid, the ZnO nanorod decorated wood surface can be transformed into a superhydrophobic surface, with a water contact angle (CA) of ∼154°. Such ZnO nanorod-modified woods with enhanced photostability, flame retardancy and water repellency offer an interesting alternative to conventional wood preservation strategies, highlighting their potential applications in some novel wood products.

  16. Crystal orientation dependent thermoelectric properties of highly oriented aluminum-doped zinc oxide thin films

    KAUST Repository

    Abutaha, Anas I.; Sarath Kumar, S. R.; Alshareef, Husam N.

    2013-01-01

    We demonstrate that the thermoelectric properties of highly oriented Al-doped zinc oxide (AZO) thin films can be improved by controlling their crystal orientation. The crystal orientation of the AZO films was changed by changing the temperature

  17. Cytotoxicity of zinc oxide (ZnO) nanoparticles is influenced by cell density and culture format.

    Science.gov (United States)

    Heng, Boon Chin; Zhao, Xinxin; Xiong, Sijing; Ng, Kee Woei; Boey, Freddy Yin-Chiang; Loo, Joachim Say-Chye

    2011-06-01

    A parameter that has often been overlooked in cytotoxicity assays is the density and confluency of mammalian cell monolayers utilized for toxicology screening. Hence, this study investigated how different cell seeding densities influenced their response to cytotoxic challenge with ZnO nanoparticles. Utilizing the same volume (1 ml per well) and concentration range (5-40 μg/ml) of ZnO nanoparticles, contradictory results were observed with higher-density cell monolayers (BEAS-2B cells) obtained either by increasing the number of seeded cells per well (50,000 vs. 200,000 cells per well of 12-well plate) or by seeding the same numbers of cells (50,000) within a smaller surface area (12-well vs. 48-well plate, 4.8 vs. 1.2 cm(2), respectively). Further experiments demonstrated that the data may be skewed by inconsistency in the mass/number of nanoparticles per unit area of culture surface, as well as by inconsistent nanoparticle to cell ratio. To keep these parameters constant, the same number of cells (50,000 per well) were seeded on 12-well plates, but with the cells being seeded at the edge of the well for the experimental group (by tilting the plate) to form a dense confluent monolayer, as opposed to a sparse monolayer for the control group seeded in the conventional manner. Utilizing such an experimental set-up for the comparative evaluation of four different cell lines (BEAS-2B, L-929, CRL-2922 and C2C12), it was observed that the high cell density monolayer was consistently more resistant to the cytotoxic effects of ZnO nanoparticles compared to the sparse monolayer for all four different cell types, with the greatest differences being observed above a ZnO concentration of 10 μg/ml. Hence, the results of this study demonstrate the need for the standardization of cell culture protocols utilized for toxicology screening of nanoparticles, with respect to cell density and mass/number of nanoparticles per unit area of culture surface.

  18. In2Ga2ZnO7 oxide semiconductor based charge trap device for NAND flash memory

    Science.gov (United States)

    Hwang, Eun Suk; Kim, Jun Shik; Jeon, Seok Min; Lee, Seung Jun; Jang, Younjin; Cho, Deok-Yong; Hwang, Cheol Seong

    2018-04-01

    The programming characteristics of charge trap flash memory device adopting amorphous In2Ga2ZnO7 (a-IGZO) oxide semiconductors as channel layer were evaluated. Metal-organic chemical vapor deposition (MOCVD) and RF-sputtering processes were used to grow a 45 nm thick a-IGZO layer on a 20 nm thick SiO2 (blocking oxide)/p++-Si (control gate) substrate, where 3 nm thick atomic layer deposited Al2O3 (tunneling oxide) and 5 nm thick low-pressure CVD Si3N4 (charge trap) layers were intervened between the a-IGZO and substrate. Despite the identical stoichiometry and other physicochemical properties of the MOCVD and sputtered a-IGZO, a much faster programming speed of MOCVD a-IGZO was observed. A comparable amount of oxygen vacancies was found in both MOCVD and sputtered a-IGZO, confirmed by x-ray photoelectron spectroscopy and bias-illumination-instability test measurements. Ultraviolet photoelectron spectroscopy analysis revealed a higher Fermi level (E F) of the MOCVD a-IGZO (∼0.3 eV) film than that of the sputtered a-IGZO, which could be ascribed to the higher hydrogen concentration in the MOCVD a-IGZO film. Since the programming in a flash memory device is governed by the tunneling of electrons from the channel to charge trapping layer, the faster programming performance could be the result of a higher E F of MOCVD a-IGZO.

  19. Room temperature inorganic polycondensation of oxide (Cu2O and ZnO) nanoparticles and thin films preparation by the dip-coating technique

    International Nuclear Information System (INIS)

    Salek, G.; Tenailleau, C.; Dufour, P.; Guillemet-Fritsch, S.

    2015-01-01

    Oxide thin solid films were prepared by dip-coating into colloidal dispersions of oxide nanoparticles stabilized at room temperature without the use of chelating or complex organic dispersing agents. Crystalline oxide nanoparticles were obtained by inorganic polycondensation and characterized by X-ray diffraction and field emission gun scanning electron microscopy. Water and ethanol synthesis and solution stabilization of oxide nanoparticle method was optimized to prepare two different structural and compositional materials, namely Cu 2 O and ZnO. The influence of hydrodynamic parameters over the particle shape and size is discussed. Spherical and rod shape nanoparticles were formed for Cu 2 O and ZnO, respectively. Isoelectric point values of 7.5 and 8.2 were determined for cuprous and zinc oxides, respectively, after zeta potential measurements. A shear thinning and thixotropic behavior was observed in both colloidal sols after peptization at pH ~ 6 with dilute nitric acid. Every colloidal dispersion stabilized in a low cost and environmentally friendly azeotrope solution composed of 96 vol.% of ethanol with water was used for the thin film preparation by the dip-coating technique. Optical properties of the light absorber cuprous oxide and transparent zinc oxide thin solid films were characterized by means of transmittance and reflectance measurements (300–1100 nm). - Highlights: • Room temperature inorganic polycondensation of crystalline oxides • Water and ethanol synthesis and solution stabilization of oxide nanoparticles • Low cost method for thin solid film preparation

  20. Room temperature inorganic polycondensation of oxide (Cu{sub 2}O and ZnO) nanoparticles and thin films preparation by the dip-coating technique

    Energy Technology Data Exchange (ETDEWEB)

    Salek, G.; Tenailleau, C., E-mail: tenailleau@chimie.ups-tlse.fr; Dufour, P.; Guillemet-Fritsch, S.

    2015-08-31

    Oxide thin solid films were prepared by dip-coating into colloidal dispersions of oxide nanoparticles stabilized at room temperature without the use of chelating or complex organic dispersing agents. Crystalline oxide nanoparticles were obtained by inorganic polycondensation and characterized by X-ray diffraction and field emission gun scanning electron microscopy. Water and ethanol synthesis and solution stabilization of oxide nanoparticle method was optimized to prepare two different structural and compositional materials, namely Cu{sub 2}O and ZnO. The influence of hydrodynamic parameters over the particle shape and size is discussed. Spherical and rod shape nanoparticles were formed for Cu{sub 2}O and ZnO, respectively. Isoelectric point values of 7.5 and 8.2 were determined for cuprous and zinc oxides, respectively, after zeta potential measurements. A shear thinning and thixotropic behavior was observed in both colloidal sols after peptization at pH ~ 6 with dilute nitric acid. Every colloidal dispersion stabilized in a low cost and environmentally friendly azeotrope solution composed of 96 vol.% of ethanol with water was used for the thin film preparation by the dip-coating technique. Optical properties of the light absorber cuprous oxide and transparent zinc oxide thin solid films were characterized by means of transmittance and reflectance measurements (300–1100 nm). - Highlights: • Room temperature inorganic polycondensation of crystalline oxides • Water and ethanol synthesis and solution stabilization of oxide nanoparticles • Low cost method for thin solid film preparation.

  1. A simple route to vertical array of quasi-1D ZnO nanofilms on FTO surfaces: 1D-crystal growth of nanoseeds under ammonia-assisted hydrolysis process

    Directory of Open Access Journals (Sweden)

    Abd Rahman Mohd Yusri

    2011-01-01

    Full Text Available Abstract A simple method for the synthesis of ZnO nanofilms composed of vertical array of quasi-1D ZnO nanostructures (quasi-NRs on the surface was demonstrated via a 1D crystal growth of the attached nanoseeds under a rapid hydrolysis process of zinc salts in the presence of ammonia at room temperature. In a typical procedure, by simply controlling the concentration of zinc acetate and ammonia in the reaction, a high density of vertically oriented nanorod-like morphology could be successfully obtained in a relatively short growth period (approximately 4 to 5 min and at a room-temperature process. The average diameter and the length of the nanostructures are approximately 30 and 110 nm, respectively. The as-prepared quasi-NRs products were pure ZnO phase in nature without the presence of any zinc complexes as confirmed by the XRD characterisation. Room-temperature optical absorption spectroscopy exhibits the presence of two separate excitonic characters inferring that the as-prepared ZnO quasi-NRs are high-crystallinity properties in nature. The mechanism of growth for the ZnO quasi-NRs will be proposed. Due to their simplicity, the method should become a potential alternative for a rapid and cost-effective preparation of high-quality ZnO quasi-NRs nanofilms for use in photovoltaic or photocatalytics applications. PACS: 81.07.Bc; 81.16.-c; 81.07.Gf.

  2. Magnetic nanoparticles as a seed layer for growing ZnO nanowires for optical applications

    International Nuclear Information System (INIS)

    AlSalhi, M S; Atif, M; Ansari, Anees A; Khun, K; Ibupoto, Z H; Willander, M

    2013-01-01

    In the present work, cerium oxide CeO 2 nanoparticles were synthesised by sol-gel method and used for the growth of ZnO nanorods. The synthesised nanoparticles were studied by x-ray diffraction technique [XRD]. Furthermore, these nanoparticles were used as seed layer for the growth of ZnO nanorods by following the hydrothermal growth method. The structural study of ZnO nanorods was carried out by using field emission scanning electron microscopy [FESEM], and x-ray diffraction [XRD] techniques. This study demonstrated that the grown ZnO nanorods are well align, uniform, good in crystal quality and possess diameter of less than 200 nm. Energy dispersive x-rays [EDX] revealed that the ZnO nanorods are only composed of zinc, cerium as seed atom and oxygen atoms and no any other impurity in the grown nanorods. Moreover, photoluminescence [PL] approach was applied for the optical characterisation and it was observed that the near-band-edge emission [NBE] was same to that of zinc acetate seed layer, however the green emission and orange/red emission peaks were slightly raised due to possible higher level of defects in the cerium oxide seeded ZnO nanorods. This study provides an alternative approach for the synthesis of controlled ZnO nanorods using cerium oxide nanoparticles as seed nucleation layer which in reverse describe the application of these nanoparticles as well as due to controlled morphology of ZnO nanorods the performance of nanodevices based on ZnO can be increased using these particles as seed.

  3. Hydrogen interstitial in H-ion implanted ZnO bulk single crystals: Evaluation by elastic recoil detection analysis and electron paramagnetic resonance

    Energy Technology Data Exchange (ETDEWEB)

    Kaida, T.; Kamioka, K.; Nishimura, T. [College of Engineering and Research Center of Ion Beam Technology, Hosei University, Koganei, Tokyo 184-8584 (Japan); Kuriyama, K., E-mail: kuri@ionbeam.hosei.ac.jp [College of Engineering and Research Center of Ion Beam Technology, Hosei University, Koganei, Tokyo 184-8584 (Japan); Kushida, K. [Department of Arts and Sciences, Osaka Kyoiku University, Kashiwara, Osaka 582-8582 (Japan); Kinomura, A. [National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568 (Japan)

    2015-12-15

    The origins of low resistivity in H ion-implanted ZnO bulk single crystals are evaluated by elastic recoil detection analysis (ERDA), electron paramagnetic resonance (EPR), and Van der Pauw methods. The H-ion implantation (peak concentration: 5.0 × 10{sup 15} cm{sup −2}) into ZnO is performed using a 500 keV implanter. The maximum of the concentration of the implanted H estimated by a TRIM simulation is at 3600 nm in depth. The resistivity decreases from ∼10{sup 3} Ω cm for un implanted ZnO to 6.5 Ω cm for as-implanted, 2.3 × 10{sup −1} Ω cm for 200 °C annealed, and 3.2 × 10{sup −1} Ω cm for 400 °C annealed samples. The ERDA measurements can evaluate the concentration of hydrogens which move to the vicinity of the surface (surface to 300 nm or 100 nm) because of the diffusion by the annealing at 200 °C and 400 °C. The hydrogen concentration near the surface estimated using the 2.0 MeV helium beam is ∼3.8 × 10{sup 13} cm{sup −2} for annealed samples. From EPR measurements, the oxygen vacancy of +charge state (V{sub o}{sup +}) is observed in as-implanted samples. The V{sub o}{sup +} related signal (g = 1.96) observed under no illumination disappears after successive illumination with a red LED and appears again with a blue light illumination. The activation energy of as-implanted, 200 °C annealed, and 400 °C annealed samples estimated from the temperature dependence of carrier concentration lies between 29 meV and 23 meV, suggesting the existence of H interstitial as a shallow donor level.

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

    International Nuclear Information System (INIS)

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

    2013-01-01

    Highlights: ► Thin ZnO films and high quality ZnO crystal were electrochemically doped with hydrogen. ► Hydrogen absorbed in ZnO causes plastic deformation both in ZnO crystal and thin films. ► In ZnO crystal a sub-surface region with very high density of defects was formed. ► Moreover, plastic deformation causes specific surface modification of ZnO crystal. ► In ZnO films hydrogen-induced plastic deformation introduced defects in the whole film. -- Abstract: ZnO films with thickness of ∼80 nm were grown by pulsed laser deposition (PLD) on MgO (1 0 0) single crystal and amorphous fused silica (FS) substrates. Structural studies of ZnO films and a high quality reference ZnO single crystal were performed by slow positron implantation spectroscopy (SPIS). It was found that ZnO films exhibit significantly higher density of defects than the reference ZnO crystal. Moreover, the ZnO film deposited on MgO substrate exhibits higher concentration of defects than the film deposited on amorphous FS substrate most probably due to a dense network of misfit dislocations. The ZnO films and the reference ZnO crystal were subsequently loaded with hydrogen by electrochemical cathodic charging. SPIS characterizations revealed that absorbed hydrogen introduces new defects into ZnO

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

    Energy Technology Data Exchange (ETDEWEB)

    Melikhova, O., E-mail: oksivmel@yahoo.com [Charles University in Prague, Faculty of Mathematics and Physics, V Holesovickach 2, CZ-180 00 Praha 8 (Czech Republic); Čížek, J.; Lukáč, F.; Vlček, M. [Charles University in Prague, Faculty of Mathematics and Physics, V Holesovickach 2, CZ-180 00 Praha 8 (Czech Republic); Novotný, M.; Bulíř, J.; Lančok, J. [Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague (Czech Republic); Anwand, W.; Brauer, G. [Institut für Strahlenphysik, Helmholtz-Zentrum Dresden-Rossendorf, PO Box 510 119, D-01314 Dresden (Germany); Connolly, J.; McCarthy, E.; Krishnamurthy, S.; Mosnier, J.-P. [National Centre for Plasma Science and Technology, School of Physical Sciences, Glasnevin, Dublin 9 (Ireland)

    2013-12-15

    Highlights: ► Thin ZnO films and high quality ZnO crystal were electrochemically doped with hydrogen. ► Hydrogen absorbed in ZnO causes plastic deformation both in ZnO crystal and thin films. ► In ZnO crystal a sub-surface region with very high density of defects was formed. ► Moreover, plastic deformation causes specific surface modification of ZnO crystal. ► In ZnO films hydrogen-induced plastic deformation introduced defects in the whole film. -- Abstract: ZnO films with thickness of ∼80 nm were grown by pulsed laser deposition (PLD) on MgO (1 0 0) single crystal and amorphous fused silica (FS) substrates. Structural studies of ZnO films and a high quality reference ZnO single crystal were performed by slow positron implantation spectroscopy (SPIS). It was found that ZnO films exhibit significantly higher density of defects than the reference ZnO crystal. Moreover, the ZnO film deposited on MgO substrate exhibits higher concentration of defects than the film deposited on amorphous FS substrate most probably due to a dense network of misfit dislocations. The ZnO films and the reference ZnO crystal were subsequently loaded with hydrogen by electrochemical cathodic charging. SPIS characterizations revealed that absorbed hydrogen introduces new defects into ZnO.

  6. Performance improvement for solution-processed high-mobility ZnO thin-film transistors

    Energy Technology Data Exchange (ETDEWEB)

    Li Chensha; Loutfy, Rafik O [Department of Chemical Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4L7 (Canada); Li Yuning; Wu Yiliang; Ong, Beng S [Materials Design and Integration Laboratory, Xerox Research Centre of Canada, 2660 Speakman Drive, Mississauga, Ontario L5K 2L1 (Canada)], E-mail: lichnsa@163.com

    2008-06-21

    The fabrication technology of stable, non-toxic, transparent, high performance zinc oxide (ZnO) thin-film semiconductors via the solution process was investigated. Two methods, which were, respectively, annealing a spin-coated precursor solution and annealing a drop-coated precursor solution, were compared. The prepared ZnO thin-film semiconductor transistors have well-controlled, preferential crystal orientation and exhibit superior field-effect performance characteristics. But the ZnO thin-film transistor (TFT) fabricated by annealing a drop-coated precursor solution has a distinctly elevated linear mobility, which further approaches the saturated mobility, compared with that fabricated by annealing a spin-coated precursor solution. The performance of the solution-processed ZnO TFT was further improved when substituting the spin-coating process by the drop-coating process.

  7. Performance improvement for solution-processed high-mobility ZnO thin-film transistors

    International Nuclear Information System (INIS)

    Li Chensha; Loutfy, Rafik O; Li Yuning; Wu Yiliang; Ong, Beng S

    2008-01-01

    The fabrication technology of stable, non-toxic, transparent, high performance zinc oxide (ZnO) thin-film semiconductors via the solution process was investigated. Two methods, which were, respectively, annealing a spin-coated precursor solution and annealing a drop-coated precursor solution, were compared. The prepared ZnO thin-film semiconductor transistors have well-controlled, preferential crystal orientation and exhibit superior field-effect performance characteristics. But the ZnO thin-film transistor (TFT) fabricated by annealing a drop-coated precursor solution has a distinctly elevated linear mobility, which further approaches the saturated mobility, compared with that fabricated by annealing a spin-coated precursor solution. The performance of the solution-processed ZnO TFT was further improved when substituting the spin-coating process by the drop-coating process

  8. Tungsten Oxide Photonic Crystals as Optical Transducer for Gas Sensing.

    Science.gov (United States)

    Amrehn, Sabrina; Wu, Xia; Wagner, Thorsten

    2018-01-26

    Some metal oxide semiconductors, such as tungsten trioxide or tin dioxide, are well-known as resistive transducers for gas sensing and offer high sensitivities down to the part per billion level. Electrical signal read-out, however, limits the information obtained on the electronic properties of metal oxides to a certain frequency range and its application because of the required electrical contacts. Therefore, a novel approach for building an optical transducer for gas reactions utilizing metal oxide photonic crystals is presented here. By the rational design of the structure and composition it is possible to synthesize a functional material which allows one to obtain insight into its electronic properties in the optical frequency range with simple experimental measures. The concept is demonstrated by tungsten trioxide inverse opal structure as optical transducer material for hydrogen sensing. The sensing behavior is analyzed in a temperature range from room temperature to 500 °C and in a wide hydrogen concentration range (3000 ppm to 10%). The sensing mechanism is mainly the refractive index change resulting from hydrogen intercalation in tungsten trioxide, but the back reaction has also impact on the optical properties of this system. Detailed chemical reaction studies provide suggestions for specific sensing conditions.

  9. A third kind growth model of tetrapod: Rod-based single crystal ZnO tetrapod nanostructure

    International Nuclear Information System (INIS)

    Gong, J.F.; Huang, H.B.; Wang, Z.Q.; Zhao, X.N.; Yang, S.G.; Yu Zhongzhen

    2008-01-01

    In this paper, rod-based ZnO tetrapods were successfully synthesized by burning Zn particles in air covered with two firebricks. The products show hexagonal wurtzite phase. The microstructures of the tetrapod were studied carefully by scanning electron microscope (SEM), transmission electron microscope (TEM), SAED and HRTEM. The results show that tetrapod has single crystalline phase with one broader nanorod growing along [0 0 0 1] direction, three triangular nanosheets, growing out of the three trisection planes along [101-bar0] direction, and three epitaxial nanowires, growing from each tip of the triangular nanosheets. Based on the experimental results, a rod-based growth model was proposed to interpret its growth mechanism. Room temperature photoluminescence spectrum reveals that the ZnO tetrapods have ultra violet (UV) emission band (389 nm) and a green emission band (517 nm)

  10. Influence of Mg doping on ZnO nanoparticles decorated on graphene oxide (GO) crumpled paper like sheet and its high photo catalytic performance under sunlight

    Science.gov (United States)

    Labhane, P. K.; Sonawane, S. H.; Sonawane, G. H.; Patil, S. P.; Huse, V. R.

    2018-03-01

    Mg doped ZnO nanoparticles decorated on graphene oxide (GO) sheets were synthesized by a wet impregnation method. The effect of Mg doping on ZnO and ZnO-GO composite has been evaluated by using x-ray diffraction (XRD), Williamson-Hall Plot (Wsbnd H Plot), field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM) and energy dispersive x-ray spectroscopy (EDX). The physical parameters of as-prepared samples were estimated by XRD data. FESEM and HR-TEM images showed the uniform distribution of nanoparticles on GO crumpled paper like sheet. Solar light photocatalytic activities of samples were evaluated spectrophotometrically by the degradation of p-nitrophenol (PNP) and indigo carmine (IC) solution. Mgsbnd ZnO decorated on GO sheets exhibit excellent catalytic efficiency compared to all other prepared samples under identical conditions, degrading PNP and IC nearly 99% within 60 min under sunlight. The effective degradation by Mgsbnd ZnO decorated on GO sheet would be due to extended solar light absorption, enhanced adsorptivity on the composite catalyst surface and efficient charge separation of photo-induced electrons. Finally, plausible mechanism was suggested with the help of scavengers study.

  11. Tuning the optical bandgap in multi-cation compound transparent conducting-oxides: The examples of In2ZnO4 and In4Sn3O12

    Science.gov (United States)

    Sabino, Fernando P.; Oliveira, Luiz N.; Wei, Su-Huai; Da Silva, Juarez L. F.

    2018-02-01

    Transparent conducting oxides such as the bixbyite In2O3 and rutile SnO2 systems have large disparities between the optical and fundamental bandgaps, ΔEgO F , because selection rules forbid dipolar transitions from the top of the valence band to the conduction-band minimum; however, the optical gaps of multi-cation compounds with the same chemical species often coincide with their fundamental gaps. To explain this conundrum, we have employed density-functional theory to compute the optical properties of multi-cation compounds, In2ZnO4 and In4Sn3O12, in several crystal structures. We show that a recently proposed mechanism to explain the disparity between the optical and fundamental gaps of M2O3 (M = Al, Ga, and In) applies also to other binary systems and to multi-compounds. Namely, a gap disparity will arise if the following three conditions are satisfied: (i) the crystal structure has inversion symmetry; (ii) the conduction-band minimum is formed by the cation and O s-orbitals; and (iii) there is strong p-d coupling and weak p-p in the vicinity of the valence-band maximum. The third property depends critically on the cationic chemical species. In the structures with inversion symmetry, Zn (Sn) strengthens (weakens) the p-d coupling in In2ZnO4 (In4Sn3O12), enhancing (reducing) the gap disparity. Furthermore, we have also identified a In4Sn3O12 structure that is 31.80 meV per formula unit more stable than a recently proposed alternative model.

  12. Tunable band structures in digital oxides with layered crystal habits

    Science.gov (United States)

    Shin, Yongjin; Rondinelli, James M.

    2017-11-01

    We use density functional calculations to show that heterovalent cation-order sequences enable control over band-gap variations up to several eV and band-gap closure in the bulk band insulator LaSrAlO4. The band-gap control originates from the internal electric fields induced by the digital chemical order, which induces picoscale band bending; the electric-field magnitude is mainly governed by the inequivalent charged monoxide layers afforded by the layered crystal habit. Charge transfer and ionic relaxations across these layers play secondary roles. This understanding is used to construct and validate a descriptor that captures the layer-charge variation and to predict changes in the electronic gap in layered oxides exhibiting antisite defects and in other chemistries.

  13. Human eosinophils are direct targets to nanoparticles: Zinc oxide nanoparticles (ZnO) delay apoptosis and increase the production of the pro-inflammatory cytokines IL-1β and IL-8.

    Science.gov (United States)

    Silva, Luis Rafael; Girard, Denis

    2016-09-30

    Zinc oxide NPs (ZnO) have been recently proposed as novel candidates for the treatment of allergic inflammatory diseases. Paradoxically, recent data suggested that ZnO could cause eosinophilic airway inflammation in rodents. Despite the above observations, there are currently no studies reporting direct interaction between a given NP and human eosinophils themselves. In this study, freshly isolated human eosinophils were incubated with ZnO and several cellular functions were studied. We found that ZnO delay human eosinophil apoptosis, partially by inhibiting caspases and by preventing caspase-4 and Bcl-xL degradation. ZnO do not induce production of reactive oxygen species but increase de novo protein synthesis. In addition, ZnO were found to increase the production of the proinflammatory IL-1β and IL-8 cytokines. Using a pharmacological approach, we demonstrated that inhibition of caspase-1 reversed the ability of ZnO to induce IL-1β and IL-8 production, whereas inhibition of caspase-4 only reversed that of IL-8. Our results indicate the necessity of conducting studies to determine the potential of using NP as nanotherapies, particularly in diseases in which eosinophils may be involved. We conclude that, indeed, human eosinophils represent potential new direct targets to NPs, ZnO in the present case. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  14. Vegetable Peel Waste for the Production of ZnO Nanoparticles and its Toxicological Efficiency, Antifungal, Hemolytic, and Antibacterial Activities

    Science.gov (United States)

    Surendra, T. V.; Roopan, Selvaraj Mohana; Al-Dhabi, Naif Abdullah; Arasu, Mariadhas Valan; Sarkar, Gargi; Suthindhiran, K.

    2016-12-01

    Zinc oxide (ZnO) nanoparticles (NPs) are important materials when making different products like sun screens, textiles, and paints. In the current study, the photocatalytic effect of prepared ZnO NPs from Moringa oleifera ( M. oleifera) was evaluated on degradation of crystal violet (CV) dye, which is largely released from textile industries and is harmful to the environment. Preliminarily, ZnO NP formation was confirmed using a double beam ultraviolet visible (UV-Vis) spectrophotometer; further, the NP size was estimated using XRD analysis and the functional group analysis was determined using Fourier transform infrared (FT-IR) spectroscopy. The morphology of the synthesized NPs was found to be a hexagonal shape using SEM and TEM analysis and elemental screening was analyzed using EDX. ZnO NPs were shown sized 40-45 nm and spherical in shape. The degradation percentage of ZnO NPs was calculated as 94% at 70 min and the rate of the reaction -k = 0.0282. The synthesized ZnO NPs were determined for effectiveness on biological activities such as antifungal, hemolytic, and antibacterial activity. ZnO NPs showed good antifungal activity against Alternaria saloni and Sclerrotium rolfii strains. Further, we have determined the hemolytic and antibacterial activity of ZnO NPs and we got successive results in antibacterial and hemolytic activities.

  15. Solution precursor plasma deposition of nanostructured ZnO coatings

    International Nuclear Information System (INIS)

    Tummala, Raghavender; Guduru, Ramesh K.; Mohanty, Pravansu S.

    2011-01-01

    Highlights: → The solution precursor route employed is an inexpensive process with capability to produce large scale coatings at fast rates on mass scale production. → It is highly capable of developing tailorable nanostructures. → This technique can be employed to spray the coatings on any kind of substrates including polymers. → The ZnO coatings developed via solution precursor plasma spray process have good electrical conductivity and reflectivity properties in spite of possessing large amount of particulate boundaries, porosity and nanostructured grains. -- Abstract: Zinc oxide (ZnO) is a wide band gap semiconducting material that has various applications including optical, electronic, biomedical and corrosion protection. It is usually synthesized via processing routes, such as vapor deposition techniques, sol-gel, spray pyrolysis and thermal spray of pre-synthesized ZnO powders. Cheaper and faster synthesis techniques are of technological importance due to increased demand in alternative energy applications. Here, we report synthesis of nanostructured ZnO coatings directly from a solution precursor in a single step using plasma spray technique. Nanostructured ZnO coatings were deposited from the solution precursor prepared using zinc acetate and water/isopropanol. An axial liquid atomizer was employed in a DC plasma spray torch to create fine droplets of precursor for faster thermal treatment in the plasma plume to form ZnO. Microstructures of coatings revealed ultrafine particulate agglomerates. X-ray diffraction confirmed polycrystalline nature and hexagonal Wurtzite crystal structure of the coatings. Transmission electron microscopy studies showed fine grains in the range of 10-40 nm. Observed optical transmittance (∼65-80%) and reflectivity (∼65-70%) in the visible spectrum, and electrical resistivity (48.5-50.1 mΩ cm) of ZnO coatings are attributed to ultrafine particulate morphology of the coatings.

  16. Solution precursor plasma deposition of nanostructured ZnO coatings

    Energy Technology Data Exchange (ETDEWEB)

    Tummala, Raghavender [Department of Mechanical Engineering, University of Michigan - Dearborn, MI 48128 (United States); Guduru, Ramesh K., E-mail: rkguduru@umich.edu [Department of Mechanical Engineering, University of Michigan - Dearborn, MI 48128 (United States); Mohanty, Pravansu S. [Department of Mechanical Engineering, University of Michigan - Dearborn, MI 48128 (United States)

    2011-08-15

    Highlights: {yields} The solution precursor route employed is an inexpensive process with capability to produce large scale coatings at fast rates on mass scale production. {yields} It is highly capable of developing tailorable nanostructures. {yields} This technique can be employed to spray the coatings on any kind of substrates including polymers. {yields} The ZnO coatings developed via solution precursor plasma spray process have good electrical conductivity and reflectivity properties in spite of possessing large amount of particulate boundaries, porosity and nanostructured grains. -- Abstract: Zinc oxide (ZnO) is a wide band gap semiconducting material that has various applications including optical, electronic, biomedical and corrosion protection. It is usually synthesized via processing routes, such as vapor deposition techniques, sol-gel, spray pyrolysis and thermal spray of pre-synthesized ZnO powders. Cheaper and faster synthesis techniques are of technological importance due to increased demand in alternative energy applications. Here, we report synthesis of nanostructured ZnO coatings directly from a solution precursor in a single step using plasma spray technique. Nanostructured ZnO coatings were deposited from the solution precursor prepared using zinc acetate and water/isopropanol. An axial liquid atomizer was employed in a DC plasma spray torch to create fine droplets of precursor for faster thermal treatment in the plasma plume to form ZnO. Microstructures of coatings revealed ultrafine particulate agglomerates. X-ray diffraction confirmed polycrystalline nature and hexagonal Wurtzite crystal structure of the coatings. Transmission electron microscopy studies showed fine grains in the range of 10-40 nm. Observed optical transmittance ({approx}65-80%) and reflectivity ({approx}65-70%) in the visible spectrum, and electrical resistivity (48.5-50.1 m{Omega} cm) of ZnO coatings are attributed to ultrafine particulate morphology of the coatings.

  17. Highly stable field emission from ZnO nanowire field emitters controlled by an amorphous indium–gallium–zinc-oxide thin film transistor

    Science.gov (United States)

    Li, Xiaojie; Wang, Ying; Zhang, Zhipeng; Ou, Hai; She, Juncong; Deng, Shaozhi; Xu, Ningsheng; Chen, Jun

    2018-04-01

    Lowering the driving voltage and improving the stability of nanowire field emitters are essential for them to be applied in devices. In this study the characteristics of zinc oxide (ZnO) nanowire field emitter arrays (FEAs) controlled by an amorphous indium–gallium–zinc-oxide thin film transistor (a-IGZO TFT) were studied. A low driving voltage along with stabilization of the field emission current were achieved. Modulation of field emission currents up to three orders of magnitude was achieved at a gate voltage of 0–32 V for a constant anode voltage. Additionally, a-IGZO TFT control can dramatically reduce the emission current fluctuation (i.e., from 46.11 to 1.79% at an emission current of ∼3.7 µA). Both the a-IGZO TFT and ZnO nanowire FEAs were prepared on glass substrates in our research, demonstrating the feasibility of realizing large area a-IGZO TFT-controlled ZnO nanowire FEAs.

  18. Epitaxial ZnO gate dielectrics deposited by RF sputter for AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors

    Science.gov (United States)

    Yoon, Seonno; Lee, Seungmin; Kim, Hyun-Seop; Cha, Ho-Young; Lee, Hi-Deok; Oh, Jungwoo

    2018-01-01

    Radio frequency (RF)-sputtered ZnO gate dielectrics for AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors (MOS-HEMTs) were investigated with varying O2/Ar ratios. The ZnO deposited with a low oxygen content of 4.5% showed a high dielectric constant and low interface trap density due to the compensation of oxygen vacancies during the sputtering process. The good capacitance-voltage characteristics of ZnO-on-AlGaN/GaN capacitors resulted from the high crystallinity of oxide at the interface, as investigated by x-ray diffraction and high-resolution transmission electron microscopy. The MOS-HEMTs demonstrated comparable output electrical characteristics with conventional Ni/Au HEMTs but a lower gate leakage current. At a gate voltage of -20 V, the typical gate leakage current for a MOS-HEMT with a gate length of 6 μm and width of 100 μm was found to be as low as 8.2 × 10-7 mA mm-1, which was three orders lower than that of the Ni/Au Schottky gate HEMT. The reduction of the gate leakage current improved the on/off current ratio by three orders of magnitude. These results indicate that RF-sputtered ZnO with a low O2/Ar ratio is a good gate dielectric for high-performance AlGaN/GaN MOS-HEMTs.

  19. Growth of high-density ZnO nanorods on wood with enhanced photostability, flame retardancy and water repellency

    Energy Technology Data Exchange (ETDEWEB)

    Kong, Lizhuo; Tu, Kunkun; Guan, Hao [Research Institute of Wood Industry, Chinese Academy of Forestry, Beijing 100091 (China); Wang, Xiaoqing, E-mail: wangxq@caf.ac.cn [Research Institute of Forestry New Technology, Chinese Academy of Forestry, Beijing 100091 (China); Research Institute of Wood Industry, Chinese Academy of Forestry, Beijing 100091 (China)

    2017-06-15

    Highlights: • ZnO nanorod arrays were deposited on the wood surface via a hydrothermal process. • The assembled ZnO nanorod arrays greatly enhanced the photostability of wood. • The treated wood can sustain direct exposure to flame with only minor smoldering. • The ZnO-coated wood modified with stearic acid showed a superhydrophobic surface. - Abstract: Zinc oxide (ZnO) nanorod arrays were successfully assembled on the wood surface in situ via a two-step process consisting of formation of ZnO seeds and subsequent crystal growth under hydrothermal conditions at a low temperature. The morphology and crystalline structure of the formed ZnO nanorods were studied by field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). Highly dense and uniform arrays of ZnO nanorods with well-defined hexagonal facets were generated on the wood surface by tuning the concentration of the ZnO growth solution during the hydrothermal treatment. Accelerated weathering tests indicated that the assembled ZnO nanorod arrays were highly protective against UV radiation and greatly enhanced the photostability of the coated wood. Meanwhile, the ZnO nanorod-coated wood can withstand continuous exposure to flame with only minor smoldering in contrast with the pristine wood catching fire easily and burning rapidly. Moreover, when further modified with low-surface-energy stearic acid, the ZnO nanorod decorated wood surface can be transformed into a superhydrophobic surface, with a water contact angle (CA) of ∼154°. Such ZnO nanorod-modified woods with enhanced photostability, flame retardancy and water repellency offer an interesting alternative to conventional wood preservation strategies, highlighting their potential applications in some novel wood products.

  20. Growth of high-density ZnO nanorods on wood with enhanced photostability, flame retardancy and water repellency

    International Nuclear Information System (INIS)

    Kong, Lizhuo; Tu, Kunkun; Guan, Hao; Wang, Xiaoqing

    2017-01-01

    Highlights: • ZnO nanorod arrays were deposited on the wood surface via a hydrothermal process. • The assembled ZnO nanorod arrays greatly enhanced the photostability of wood. • The treated wood can sustain direct exposure to flame with only minor smoldering. • The ZnO-coated wood modified with stearic acid showed a superhydrophobic surface. - Abstract: Zinc oxide (ZnO) nanorod arrays were successfully assembled on the wood surface in situ via a two-step process consisting of formation of ZnO seeds and subsequent crystal growth under hydrothermal conditions at a low temperature. The morphology and crystalline structure of the formed ZnO nanorods were studied by field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). Highly dense and uniform arrays of ZnO nanorods with well-defined hexagonal facets were generated on the wood surface by tuning the concentration of the ZnO growth solution during the hydrothermal treatment. Accelerated weathering tests indicated that the assembled ZnO nanorod arrays were highly protective against UV radiation and greatly enhanced the photostability of the coated wood. Meanwhile, the ZnO nanorod-coated wood can withstand continuous exposure to flame with only minor smoldering in contrast with the pristine wood catching fire easily and burning rapidly. Moreover, when further modified with low-surface-energy stearic acid, the ZnO nanorod decorated wood surface can be transformed into a superhydrophobic surface, with a water contact angle (CA) of ∼154°. Such ZnO nanorod-modified woods with enhanced photostability, flame retardancy and water repellency offer an interesting alternative to conventional wood preservation strategies, highlighting their potential applications in some novel wood products.

  1. Photocatalytic and electrochemical performance of three-Dimensional reduced graphene Oxide/WS{sub 2}/Mg-doped ZnO composites

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Weiwei [College of Materials Science and Engineering, Changsha University of Science and Technology, Changsha, 410114 (China); Chen, Xi’an [Zhejiang Key Laboratory of Carbon Materials, College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, 325027 (China); Mei, Wei [College of Materials Science and Engineering, Changsha University of Science and Technology, Changsha, 410114 (China); Chen, Chuansheng, E-mail: 1666423158@qq.com [College of Materials Science and Engineering, Changsha University of Science and Technology, Changsha, 410114 (China); Tsang, Yuenhong [Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, 999077 (China)

    2017-04-01

    Highlights: • 3D graphene oxide/WS{sub 2}/Mg-doped ZnO composites were prepared by electrostatic self-assembly and coprecipitation methods. • A significant photocatalytic activity enhancement of rGWMZ was observed. • The enhancement for photocatalytic activity is ascribed to the synergistic effect of rGO and WS{sub 2} nanosheets. - Abstract: To improve the dispersion of reduced graphene oxide and enhance the photocatalytic property of reduced graphene oxide/Mg-doped ZnO composites (rGMZ), the reduced graphene oxide/WS{sub 2}/Mg-doped ZnO composites (rGWMZ) were prepared by electrostatic self-assembly and coprecipitation methods. The effects of mass ratio of WS{sub 2} nanosheets to reduced graphene oxide (WS{sub 2}/rGO wt.%) and calcination temperature on the photocatalytic and electrochemical property of rGWMZ composites were investigated. Experimental results showed that the photocatalytic efficiency of rGWMZ composites is three-fold compared with that of rGMZ composites when the WS{sub 2}/rGO wt.% is 20.8% and calcination temperature is 500 °C, in which the degradation ratio Rhodamin B (RhB) can reach 95% within 15 min under the UV light and 90% within 90 min under simulated solar light. In addition, the rGWMZ show larger capacitance and smaller resistance than rGMZ. The enhancement for photocatalytic activity and electrochemical performance of rGWMZ is ascribed to improving the specific surface area, electrical conductivity and electronic storage capability because of the synergistic effect of rGO and WS{sub 2} nanosheets.

  2. Performance of Dye-Sensitized Solar Cells (DSSCs) Fabricated with Zinc Oxide (ZnO) Nanpowders and Nanorods

    Science.gov (United States)

    Chatterjee, Suman

    2018-03-01

    Due to their high efficiencies, along with lower production costs, many researchers are working on dye-sensitized solar cells (DSSCs) over last few decades as a substitute technology for nonconventional energy. Nanostructured ZnO has got many interesting properties such as wide band gap, large exciton binding energy, good exciton stability, and high breakdown strength, which are applicable as DSSC electrodes. This present work compares the device properties of DSSC fabricated using ZnO nanorods on a ZnO film and ZnO nanopowders. Different types of ZnO photoanode and dye combinations are used to study the stability and photovoltaic properties of the DSSC cell. The photovoltaic properties of the ZnO-based DSSC samples were systematically investigated. The photovoltaic properties of fabricated cell obtained are discussed in the light of band structure and density of states of different types of ZnO nanolayers. The ZnO nanorods fabricated through the sol-gel route have more uniform thickness resulting in enhanced photovoltaic properties of the fabricated device.

  3. A comparative study of ultraviolet photoconductivity relaxation in zinc oxide (ZnO) thin films deposited by different techniques

    International Nuclear Information System (INIS)

    Yadav, Harish Kumar; Gupta, Vinay

    2012-01-01

    Photoresponse characteristics of ZnO thin films deposited by three different techniques namely rf diode sputtering, rf magnetron sputtering, and electrophoretic deposition has been investigated in the metal-semiconductor-metal (MSM) configuration. A significant variation in the crystallinity, surface morphology, and photoresponse characteristics of ZnO thin film with change in growth kinetics suggest that the presence of defect centers and their density govern the photodetector relaxation properties. A relatively low density of traps compared to the true quantum yield is found very crucial for the realization of practical ZnO thin film based ultraviolet (UV) photodetector.

  4. A comparative study of ultraviolet photoconductivity relaxation in zinc oxide (ZnO) thin films deposited by different techniques

    Energy Technology Data Exchange (ETDEWEB)

    Yadav, Harish Kumar; Gupta, Vinay [Department of Physics and Astrophysics, University of Delhi, Delhi 110 007 (India)

    2012-05-15

    Photoresponse characteristics of ZnO thin films deposited by three different techniques namely rf diode sputtering, rf magnetron sputtering, and electrophoretic deposition has been investigated in the metal-semiconductor-metal (MSM) configuration. A significant variation in the crystallinity, surface morphology, and photoresponse characteristics of ZnO thin film with change in growth kinetics suggest that the presence of defect centers and their density govern the photodetector relaxation properties. A relatively low density of traps compared to the true quantum yield is found very crucial for the realization of practical ZnO thin film based ultraviolet (UV) photodetector.

  5. Electro-optical switching of liquid crystals of graphene oxide

    Science.gov (United States)

    Song, Jang-Kun

    Electric field effects on aqueous graphene-oxide (GO) dispersions are reviewed in this chapter. In isotropic and biphasic regimes of GO dispersions, in which the inter-particle friction is low, GO particles sensitively respond to the application of electric field, producing field-induced optical birefringence. The electro-optical sensitivity dramatically decreases as the phase transits to the nematic phase; the increasing inter-particle friction hinders the rotational switching of GO particles. The corresponding Kerr coefficient reaches the maximum near the isotropic to biphasic transition concentration, at which the Kerr coefficient is found be c.a. 1:8 · 10-5 mV-2, the highest value ever reported in all Kerr materials. The exceptionally large Kerr effect arises from the Maxwell- Wagner polarization of GO particles with an extremely large aspect ratio and a thick electrical double layer (EDL). The polarization sensitively depends on the ratio of surface and bulk conductivities in dispersions. As a result, low ion concentration in bulk solvent is highly required to achieve a quality electro-optical switching in GO dispersions. Spontaneous vinylogous carboxylic reaction in GO particles produces H+ ions, resulting in spontaneous degradation of electro-optical response with time, hence the removal of residual ions by using a centrifuge cleaning process significantly improves the electro-optical sensitivity. GO particle size is another important parameter for the Kerr coefficient and the response time. The best performance is observed in a GO dispersion with c.a. 0.5 μm mean size. Dielectrophoretic migration of GO particles can be also used to manipulate GO particles in solution. Using these unique features of GO dispersions, one can fabricate GO liquid crystal devices similar to conventional liquid crystal displays; the large Kerr effect allows fabricating a low power device working at extremely low electric fields.

  6. doped ZnO thick film resistors

    Indian Academy of Sciences (India)

    The characterization and ethanol gas sensing properties of pure and doped ZnO thick films were investigated. Thick films of pure zinc oxide were prepared by the screen printing technique. Pure zinc oxide was almost insensitive to ethanol. Thick films of Al2O3 (1 wt%) doped ZnO were observed to be highly sensitive to ...

  7. Piezoelectric Response Evaluation of ZnO Thin Film Prepared by RF Magnetron Sputtering

    Directory of Open Access Journals (Sweden)

    Cheng Da-Long

    2017-01-01

    Full Text Available The most important parameter of piezoelectric materials is piezoelectric coefficient (d33. In this study, the piezoelectric ZnO thin films were deposited on the SiNx/Si substrate. The 4 inches substrate is diced into 8 cm× 8 cm piece. During the deposition process, a zinc target (99.999 wt% of 2 inches diameter was used. The vertical distance between the target and the substrate holder was fixed at 5 cm. The piezoelectric response of zinc oxide (ZnO thin films were obtained by using a direct measurement system. The system adopts a mini impact tip to generate an impulsive force and read out the piezoelectric signals immediately. Experimentally, a servo motor is used to produce a fixed quantity of force, for giving an impact against to the piezoelectric film. The ZnO thin films were deposited using the reactive radio frequency (RF magnetron sputtering method. The electric charges should be generated because of the material’s extrusion. This phenomenon was investigated through the oscilloscope by one shot trigger. It was apparent that all ZnO films exhibit piezoelectric responses evaluated by our measurement system, however, its exhibit a significant discrepancy. The piezoelectric responses of ZnO thin film at various deposition positions were measured and the crystal structures of the sputtering pressure were also discussed. The crystalline characteristics of ZnO thin films are investigated through the XRD and SEM. The results show the ZnO thin film exhibits good crystalline pattern and surface morphology with controlled sputtering condition. The ZnO thin films sputtered using 2 inches target present various piezoelectric responses. With the exactly related position, a best piezoelectric response of ZnO thin film can be achieved.

  8. N-Oxide-N-oxide interactions and Cl...Cl halogen bonds in pentachloropyridine N-oxide: the many-body approach to interactions in the crystal state.

    Science.gov (United States)

    Wzgarda-Raj, Kinga; Rybarczyk-Pirek, Agnieszka J; Wojtulewski, Sławomir; Palusiak, Marcin

    2018-02-01

    Pentachloropyridine N-oxide, C 5 Cl 5 NO, crystallizes in the monoclinic space group P2 1 /c. In the crystal structure, molecules are linked by C-Cl...Cl halogen bonds into infinite ribbons extending along the crystallographic [100] direction. These molecular aggregates are further stabilized by very short intermolecular N-oxide-N-oxide interactions into herringbone motifs. Computations based on quantum chemistry methods allowed for a more detailed description of the N-oxide-N-oxide interactions and Cl...Cl halogen bonds. For this purpose, Hirshfeld surface analysis and the many-body approach to interaction energy were applied.

  9. A boron and gallium co-doped ZnO intermediate layer for ZnO/Si heterojunction diodes

    Science.gov (United States)

    Lu, Yuanxi; Huang, Jian; Li, Bing; Tang, Ke; Ma, Yuncheng; Cao, Meng; Wang, Lin; Wang, Linjun

    2018-01-01

    ZnO (Zinc oxide)/Si (Silicon) heterojunctions were prepared by depositing n-type ZnO films on p-type single crystal Si substrates using magnetron sputtering. A boron and gallium co-doped ZnO (BGZO) high conductivity intermediate layer was deposited between aurum (Au) electrodes and ZnO films. The influence of the BGZO layer on the properties of Au/ZnO contacts and the performance of ZnO/Si heterojunctions was investigated. The results show an improvement in contact resistance by introducing the BGZO layer. Compared with the ZnO/Si heterojunction, the BGZO/ZnO/Si heterojunction exhibits a larger forward current, a smaller turn-on voltage and higher ratio of ultraviolet (UV) photo current/dark current.

  10. Crystal structure of the uranyl-oxide mineral rameauite

    Energy Technology Data Exchange (ETDEWEB)

    Plasil, Jakub [ASCR, Prague (Czech Republic). Inst. of Physics; Skoda, Radek [Masaryk Univ., Brno (Czech Republic). Dept. of Geological Sciences; Cejka, Jiri [National Museum, Prague (Czech Republic). Dept. of Mineralogy and Petrology; Bourgoin, Vincent; Boulliard, Jean-Claude [Pierre et Marie Curie Univ., Paris (France). Association Jean Wyart, Collection des Mineraux de Jussieu

    2016-12-15

    Rameauite is a rare supergene uranyl-oxide hydroxy-hydrate mineral that forms during hydration-oxidation weathering of uraninite. On the basis of single-crystal X-ray diffraction data collected on a microfocus source, rameauite is monoclinic, space group Cc, with a = 13.9458(19), b = 14.3105(19), c = 13.8959(18) Aa, β = 118.477(14) , V = 2437.7(6) Aa{sup 3} and Z = 4, with D{sub calc} = 5.467 g cm{sup -3}. The structure of rameauite (R = 0.060 for 1698 unique observed reflections) contains sheets of the β-U{sub 3}O{sub 8} topology, with both UO{sub 6} and UO{sub 7} bipyramids, which is similar to the sheets found in spriggite, ianthinite and wyartite. The sheets alternate with the interlayer, which contains K{sup +}, Ca{sup 2+} and H{sub 2}O molecules. Interstitial cations are linked into infinite chains that extend along [10-1]. Adjacent sheets are linked through K-O, Ca-O and H-bonds. The structural formula of rameauite is K{sub 2} Ca(H{sub 2}{sup [3]}O){sub 1}(H{sub 2}{sup [5]}O){sub 4}[(UO{sub 2}) {sub 6}O{sub 6}(OH){sub 4}](H{sub 2}{sup [4]}O){sub 1}. The empirical formula obtained from the average of eight electron-microprobe analyses is (on the basi s of 6 U p.f.u.) K{sub 1.87}(Ca{sub 1.10}Sr{sub 0.04}){sub Σ1.14}[(UO 2){sub 6}O{sub 6}(OH){sub 4.15}].6H{sub 2}O. The Raman spectrum is dominate d by U.O and O.H vibrations. A discussion of related uranyl-oxide minerals is given.

  11. Thin films of metal oxides on metal single crystals: Structure and growth by scanning tunneling microscopy

    International Nuclear Information System (INIS)

    Galloway, H.C.

    1995-12-01

    Detailed studies of the growth and structure of thin films of metal oxides grown on metal single crystal surfaces using Scanning Tunneling Microscopy (STM) are presented. The oxide overlayer systems studied are iron oxide and titanium oxide on the Pt(III) surface. The complexity of the metal oxides and large lattice mismatches often lead to surface structures with large unit cells. These are particularly suited to a local real space technique such as scanning tunneling microscopy. In particular, the symmetry that is directly observed with the STM elucidates the relationship of the oxide overlayers to the substrate as well as distinguishing, the structures of different oxides

  12. Self-limiting growth of ZnO films on (0 0 0 1) sapphire substrates by atomic layer deposition at low temperatures using diethyl-zinc and nitrous oxide

    International Nuclear Information System (INIS)

    Lin, Yen-Ting; Chung, Ping-Han; Lai, Hung-Wei; Su, Hsin-Lun; Lyu, Dong-Yuan; Yen, Kuo-Yi; Lin, Tai-Yuan; Kung, Chung-Yuan; Gong, Jyh-Rong

    2009-01-01

    Atomic layer deposition (ALD) of zinc oxide (ZnO) films on (0 0 0 1) sapphire substrates was conducted at low temperatures by using diethyl-zinc (DEZn) and nitrous oxide (N 2 O) as precursors. It was found that a monolayer-by-monolayer growth regime occurred at 300 deg. C in a range of DEZn flow rates from 5.7 to 8.7 μmol/min. Furthermore, the temperature self-limiting process window for the ALD-grown ZnO films was also observed ranging from 290 to 310 deg. C. A deposition mechanism is proposed to explain how saturated growth of ZnO is achieved by using DEZn and N 2 O. Transmission spectroscopic studies of the ZnO films prepared in the self-limiting regime show that the transmittances of ZnO films are as high as 80% in visible and near infrared spectra. Experimental results indicate that ZnO films with high optical quality can be achieved by ALD at low temperatures using DEZn and N 2 O precursors.

  13. CuO and ZnO nanoparticles: phytotoxicity, metal speciation, and induction of oxidative stress in sand-grown wheat

    Energy Technology Data Exchange (ETDEWEB)

    Dimkpa, Christian O., E-mail: cdimkpa@usu.edu [Utah State University, Department of Biological Engineering (United States); McLean, Joan E. [Utah State University, Utah Water Research Laboratory (United States); Latta, Drew E. [Argonne National Laboratory, Biosciences Division (United States); Manangon, Eliana [University of Utah, Department of Geology and Geophysics (United States); Britt, David W. [Utah State University, Department of Biological Engineering (United States); Johnson, William P. [University of Utah, Department of Geology and Geophysics (United States); Boyanov, Maxim I. [Argonne National Laboratory, Biosciences Division (United States); Anderson, Anne J. [Utah State University, Department of Biological Engineering (United States)

    2012-09-15

    Metal oxide nanoparticles (NPs) are reported to impact plant growth in hydroponic systems. This study describes the impact of commercial CuO (<50 nm) and ZnO (<100 nm) NPs on wheat (Triticum aestivum) grown in a solid matrix, sand. The NPs contained both metallic and non-metallic impurities to different extents. Dynamic light scattering and atomic force microscopy (AFM) assessments confirmed aggregation of the NPs to submicron sizes. AFM showed transformation of ZnO NPs from initial rhomboid shapes in water to elongated rods in the aqueous phase of the sand matrix. Solubilization of metals occurred in the sand at similar rates from CuO or ZnO NPs as their bulk equivalents. Amendment of the sand with 500 mg Cu and Zn/kg sand from the NPs significantly (p = 0.05) reduced root growth, but only CuO NPs impaired shoot growth; growth reductions were less with the bulk amendments. Dissolved Cu from CuO NPs contributed to their phytotoxicity but Zn release did not account for the changes in plant growth. Bioaccumulation of Cu, mainly as CuO and Cu(I)-sulfur complexes, and Zn as Zn-phosphate was detected in the shoots of NP-challenged plants. Total Cu and Zn levels in shoot were similar whether NP or bulk materials were used. Oxidative stress in the NP-treated plants was evidenced by increased lipid peroxidation and oxidized glutathione in roots and decreased chlorophyll content in shoots; higher peroxidase and catalase activities were present in roots. These findings correlate with the NPs causing increased production of reactive oxygen species. The accumulation of Cu and Zn from NPs into edible plants has relevance to the food chain.

  14. High-performance zno transistors processed via an aqueous carbon-free metal oxide precursor route at temperatures between 80-180 °c

    KAUST Repository

    Lin, Yenhung

    2013-06-25

    An aqueous and carbon-free metal-oxide precursor route is used in combination with a UV irradiation-assisted low-temperature conversion method to fabricate low-voltage ZnO transistors with electron mobilities exceeding 10 cm2/Vs at temperatures <180°C. Because of its low temperature requirements the method allows processing of high-performance transistors onto temperature sensitive substrates such as plastic. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Coherent acoustic phonon oscillation accompanied with backward acoustic pulse below exciton resonance in a ZnO epifilm on oxide-buffered Si(1 1 1)

    International Nuclear Information System (INIS)

    Lin, Ja-Hon; Shen, Yu-Kai; Lu, Chia-Hui; Chen, Yao-Hui; Chang, Chun-peng; Liu, Wei-Rein; Hsu, Chia-Hung; Lee, Wei-Chin; Hong, Minghwei; Kwo, Jueinai-Raynien; Hsieh, Wen-Feng

    2016-01-01

    Unlike coherent acoustic phonons (CAPs) generated from heat induced thermal stress by the coated Au film, we demonstrated the oscillation from c-ZnO epitaxial film on oxide buffered Si through a degenerate pump–probe technique. As the excited photon energy was set below the exciton resonance, the electronic stress that resulted from defect resonance was used to induce acoustic wave. The damped oscillation revealed a superposition of a high frequency and long decay CAP signal with a backward propagating acoustic pulse which was generated by the absorption of the penetrated pump beam at the Si surface and selected by the ZnO layer as the acoustic resonator. (paper)

  16. Identification of vacancy defect complexes in transparent semiconducting oxides ZnO, In2O3 and SnO2

    International Nuclear Information System (INIS)

    Makkonen, Ilja; Korhonen, Esa; Prozheeva, Vera; Tuomisto, Filip

    2016-01-01

    Positron annihilation spectroscopy, when combined with supporting high-quality modeling of positron states and annihilation in matter, is a powerful tool for detailed defect identification of vacancy-type defects in semiconductors and oxides. Here we demonstrate that the Doppler broadening of the positron annihilation radiation is a very sensitive means for observing the oxygen environment around cation vacancies, the main open-volume defects trapping positrons in measurements made for transparent semiconducting oxides. Changes in the positron annihilation signal due to external manipulation such as irradiation and annealing can be correlated with the associated changes in the sizes of the detected vacancy clusters. Our examples for ZnO, In 2 O 3 and SnO 2 demonstrate that oxygen vacancies in oxides can be detected directly using positron annihilation spectroscopy when they are complexed with cation vacancies. (paper)

  17. Identification of vacancy defect complexes in transparent semiconducting oxides ZnO, In2O3 and SnO2

    Science.gov (United States)

    Makkonen, Ilja; Korhonen, Esa; Prozheeva, Vera; Tuomisto, Filip

    2016-06-01

    Positron annihilation spectroscopy, when combined with supporting high-quality modeling of positron states and annihilation in matter, is a powerful tool for detailed defect identification of vacancy-type defects in semiconductors and oxides. Here we demonstrate that the Doppler broadening of the positron annihilation radiation is a very sensitive means for observing the oxygen environment around cation vacancies, the main open-volume defects trapping positrons in measurements made for transparent semiconducting oxides. Changes in the positron annihilation signal due to external manipulation such as irradiation and annealing can be correlated with the associated changes in the sizes of the detected vacancy clusters. Our examples for ZnO, In2O3 and SnO2 demonstrate that oxygen vacancies in oxides can be detected directly using positron annihilation spectroscopy when they are complexed with cation vacancies.

  18. Spectroscopy of photonic band gaps in mesoporous one-dimensional photonic crystals based on aluminum oxide

    International Nuclear Information System (INIS)

    Gorelik, V.S.; Voinov, Yu.P.; Shchavlev, V.V.; Bi, Dongxue; Shang, Guo Liang; Fei, Guang Tao

    2017-01-01

    Mesoporous one-dimensional photonic crystals based on aluminum oxide have been synthesized by electrochemical etching method. Reflection spectra of the obtained mesoporous samples in a wide spectral range that covers several band gaps are presented. Microscopic parameters of photonic crystals are calculated and corresponding reflection spectra for the first six band gaps are presented.

  19. Synthesis and characterization of ZnO thin film by low cost modified SILAR technique

    Directory of Open Access Journals (Sweden)

    Haridas D. Dhaygude

    2016-03-01

    Full Text Available The ZnO thin film is prepared on Fluorine Tin Oxide (FTO coated glass substrate by using SILAR deposition technique containing ZnSO4.7H2O and NaOH as precursor solution with 150 deeping cycles at 70 °C temperature. Nanocrystalline diamond like ZnO thin film is characterized by different characterization techniques such as X-ray diffraction (XRD, Fourier transform (FT Raman spectrometer, Field Emission Scanning Electron Microscopy (FE-SEM with Energy dispersive X-Ray Analysis (EDAX, optical absorption, surface wettability and photoelectrochemical cell performance measurement. The X-ray diffraction analysis shows that the ZnO thin film is polycrystalline in nature having hexagonal crystal structure. The FT-Raman scattering exhibits a sharp and strong mode at 383 cm−1 which confirms hexagonal ZnO nanostructure. The surface morphology study reveals that deposited ZnO film consists of nanocrystalline diamond like morphology all over the substrate. The synthesized thin film exhibited absorption wavelength around 309 nm. Optical study predicted the direct band gap and band gap energy of this film is found to be 3.66 eV. The photoelectrochemical cell (PEC parameter measurement study shows that ZnO sample confirmed the highest values of, short circuit current (Isc - 629 mAcm−2, open circuit voltage (Voc - 878 mV, fill factor (FF - 0.48, and maximum efficiency (η - 0.89%, respectively.

  20. ZnO thin films on single carbon fibres fabricated by Pulsed Laser Deposition (PLD)

    Energy Technology Data Exchange (ETDEWEB)

    Krämer, André; Engel, Sebastian [Otto Schott Institute of Materials Research (OSIM), Friedrich Schiller University Jena, Löbdergraben 32, 07743 Jena (Germany); Sangiorgi, Nicola [Institute of Science and Technology for Ceramics – National Research Council of Italy (CNR-ISTEC), via Granarolo 64, 48018 Faenza, RA (Italy); Department of Chemical Science and Technologies, University of Rome Tor Vergata, via della Ricerca Scientifica, 00133 Rome (Italy); Sanson, Alessandra [Institute of Science and Technology for Ceramics – National Research Council of Italy (CNR-ISTEC), via Granarolo 64, 48018 Faenza, RA (Italy); Bartolomé, Jose F. [Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas (CSIC), C/Sor Juana Inés de la Cruz 3, 28049 Madrid (Spain); Gräf, Stephan, E-mail: stephan.graef@uni-jena.de [Otto Schott Institute of Materials Research (OSIM), Friedrich Schiller University Jena, Löbdergraben 32, 07743 Jena (Germany); Müller, Frank A. [Otto Schott Institute of Materials Research (OSIM), Friedrich Schiller University Jena, Löbdergraben 32, 07743 Jena (Germany); Center for Energy and Environmental Chemistry Jena (CEEC Jena), Friedrich Schiller University Jena, Philosophenweg 7a, 07743 Jena (Germany)

    2017-03-31

    Highlights: • Carbon fibres were entirely coated with thin films consisting of aligned ZnO crystals. • A Q-switched CO2 laser was utilised as radiation source. • Suitability of ZnO thin films on carbon fibres as photo anodes for DSSC was studied. - Abstract: Single carbon fibres were 360° coated with zinc oxide (ZnO) thin films by pulsed laser deposition using a Q-switched CO{sub 2} laser with a pulse duration τ ≈ 300 ns, a wavelength λ = 10.59 μm, a repetition frequency f{sub rep} = 800 Hz and a peak power P{sub peak} = 15 kW in combination with a 3-step-deposition technique. In a first set of experiments, the deposition process was optimised by investigating the crystallinity of ZnO films on silicon and polished stainless steel substrates. Here, the influence of the substrate temperature and of the oxygen partial pressure of the background gas were characterised by scanning electron microscopy and X-ray diffraction analyses. ZnO coated carbon fibres and conductive glass sheets were used to prepare photo anodes for dye-sensitised solar cells in order to investigate their suitability for energy conversion devices. To obtain a deeper insight of the electronic behaviour at the interface between ZnO and substrate I–V measurements were performed.

  1. Chemical route to synthesis of mesoporous ZnO thin films and their liquefied petroleum gas sensor performance

    International Nuclear Information System (INIS)

    Dhawale, D.S.; Lokhande, C.D.

    2011-01-01

    Highlights: → Low temperature synthesis of mesoporous ZnO thin films by CBD method with urea containing bath. → Wurtzite crystal structure of mesoporous ZnO has been confirmed from the XRD study. → SEM images reveal the formation of hydrophobic mesoporous ZnO thin films. → Maximum LPG response of 52% has been achieved with high stability. - Abstract: In the present work, we report base free chemical bath deposition (CBD) of mesoporous zinc oxide (ZnO) thin films from urea containing bath for liquefied petroleum gas (LPG) sensor application. Mesoporous morphology with average pore size ∼2 μm and wurtzite crystal structure are confirmed from scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The surface of ZnO is hydrophobic with water contact angle 128 ± 1 o . Optical study reveals the presence of direct bad gap with energy 3.24 eV. The gas sensing study reveals the mesoporous ZnO is highly selective towards LPG as compared with CO 2 and maximum LPG response of 52% is achieved upon the exposure of 3900 ppm LPG at 573 K as well as good reproducibility and short response/recovery times.

  2. Ag nanoparticles-decorated ZnO nanorod array on a mechanical flexible substrate with enhanced optical and antimicrobial properties

    Science.gov (United States)

    Chen, Yi; Tse, Wai Hei; Chen, Longyan; Zhang, Jin

    2015-03-01

    Heteronanostructured zinc oxide nanorod (ZnO NR) array are vertically grown on polydimethylsiloxane (PDMS) through a hydrothermal method followed by an in situ deposition of silver nanoparticles (Ag NPs) through a photoreduction process. The Ag-ZnO heterostructured nanorods on PDMS are measured with an average diameter of 160 nm and an average length of 2 μm. ZnO NRs measured by high-resolution transmission electron microscope (HRTEM) shows highly crystalline with a lattice fringe of 0.255 nm, which corresponds to the (0002) planes in ZnO crystal lattice. The average diameter of the Ag NPs in situ deposited on the ZnO NRs is estimated at 22 ± 2 nm. As compared to the bare ZnO NRs, the heterostructured Ag-ZnO nanorod array shows enhanced ultraviolet (UV) absorption at 440 nm, and significant emission in the visible region (λem = 542 nm). In addition, the antimicrobial efficiency of Ag-ZnO heterostructured nanorod array shows obvious improvement as compared to bare ZnO nanorod array. The cytotoxicity of ZnO nanorod array with and without Ag NPs was studied by using 3 T3 mouse fibroblast cell line. No significant toxic effect is imposed on the cells.

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

    OpenAIRE

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

    2013-01-01

    ZnO films with thickness of ~80 nm were grown by pulsed laser deposition (PLD) on MgO (1 0 0) single crystal and amorphous fused silica (FS) substrates. Structural studies of ZnO films and a high quality reference ZnO single crystal were performed by slow positron implantation spectroscopy (SPIS). It was found that ZnO films exhibit significantly higher density of defects than the reference ZnO crystal. Moreover, the ZnO film deposited on MgO substrate exhibits higher concentration of defects...

  4. Growth and characterization of ZnO nanowires for optical applications

    International Nuclear Information System (INIS)

    AlSalhi, M S; Atif, M; Ansari, A A; Khun, K; Ibupoto, Z H; Willander, M

    2013-01-01

    In the present work, cerium oxide CeO 2 nanoparticles were synthesized by the sol–gel method and used for the growth of ZnO nanorods. The synthesized nanoparticles were studied by x-ray diffraction (XRD) and Raman spectroscopic techniques. Furthermore, these nanoparticles were used as the seed layer for the growth of ZnO nanorods by following the hydrothermal growth method. The structural study of ZnO nanorods was carried out by means of field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM) and XRD techniques. This study demonstrated that the grown ZnO nanorods are well aligned, uniform, of good crystal quality and have diameters of less than 200 nm. Energy dispersive x-ray (EDX) analysis revealed that the ZnO nanorods are composed only of zinc, cerium as the seed atom, and oxygen atoms, with no other impurities in the grown nanorods. Moreover, a photoluminescence (PL) approach was applied for the optical characterization, and it was observed that the near-band-edge (NBE) emission was the same as that of the zinc acetate seed layer, however the green and orange/red emission peaks were slightly raised due to possibly higher levels of defects in the cerium oxide seeded ZnO nanorods. This study provides an alternative approach for the controlled synthesis of ZnO nanorods using cerium oxide nanoparticles as the seed nucleation layer, improving both the morphology of the nanorods and the performance of devices based upon them. (paper)

  5. Femtosecond UV laser non-ablative surface structuring of ZnO crystal: impact on exciton photoluminescence

    Energy Technology Data Exchange (ETDEWEB)

    Museur, Luc [Laboratoire de Physique des Lasers (LPL), UMR 7538 CNRS, Institut Galilee, Universite Paris 13, 93430 Villetaneuse (France); Michel, Jean-Pierre [Laboratoire des Proprietes Mecaniques et Thermodynamiques des Materiaux (LPMTM), UMR 9001 CNRS, Institut Galilee, Universite Paris 13, 93430 Villetaneuse (France); Portes, Patrick; Kanaev, Andrei V. [Laboratoire d' Ingenierie des Materiaux et des Hautes Pressions (LIMHP), UMR 1311 CNRS, Institut Galilee, Universite Paris 13, 93430 Villetaneuse (France); Englezis, Apostolis; Stassinopoulos, Andreas; Anglos, Demetrios [Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas (IESL-FORTH), 71110 Heraklion, Crete (Greece)

    2010-03-15

    The ultraviolet (UV) laser irradiation (248 nm) of monocrystalline wurtzite ZnO with 450 fs pulses results in surface modification. A formation of two orthogonal ripple structures with a period of 400-500 nm was observed oriented parallel and perpendicular to the laser beam polarization. The UV exciton emission obtained on the irradiated domains is found greatly enhanced locally up to {approx}10{sup 3} times. The photoluminescence band is redshifted by 2-3 nm and 40% narrower (full width at half-maximum), while at the same time the E{sub 2} (439 cm{sup -1}) Raman band intensity increases up to {approx}50 times. The process is found irreversible with the threshold fluence of 11 mJ/cm{sup 2}, which is considerably lower than the ablation threshold 115 mJ/cm{sup 2}. Fine surface nanostructuring on the scale of {approx}10 nm may be responsible for the observed effect. (c) 2008 Optical Society of America.

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

    Energy Technology Data Exchange (ETDEWEB)

    Oral, A. Yavuz [Department of Materials Science and Engineering, Gebze Institute of Technology, Gebze 41400 (Turkey)]. E-mail: aoral@gyte.edu.tr; Bahsi, Z. Banu [Department of Materials Science and Engineering, Gebze Institute of Technology, Gebze 41400 (Turkey); Aslan, M. Hasan [Department of Physics, Gebze Institute of Technology, Gebze 41400 (Turkey)

    2007-03-15

    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.

  7. Comparison of modification strategies towards enhanced charge carrier separation and photocatalytic degradation activity of metal oxide semiconductors (TiO2, WO3 and ZnO)

    Science.gov (United States)

    Kumar, S. Girish; Rao, K. S. R. Koteswara

    2017-01-01

    Metal oxide semiconductors (TiO2, WO3 and ZnO) finds unparalleled opportunity in wastewater purification under UV/visible light, largely encouraged by their divergent admirable features like stability, non-toxicity, ease of preparation, suitable band edge positions and facile generation of active oxygen species in the aqueous medium. However, the perennial failings of these photocatalysts emanates from the stumbling blocks like rapid charge carrier recombination and meager visible light response. In this review, tailoring the surface-bulk electronic structure through the calibrated and veritable approaches such as impurity doping, deposition with noble metals, sensitizing with other compounds (dyes, polymers, inorganic complexes and simple chelating ligands), hydrogenation process (annealing under hydrogen atmosphere), electronic integration with other semiconductors, modifying with carbon nanostructures, designing with exposed facets and tailoring with hierarchical morphologies to overcome their critical drawbacks are summarized. Taking into account the materials intrinsic properties, the pros and cons together with similarities and striking differences for each strategy in specific to TiO2, WO3 & ZnO are highlighted. These subtlety enunciates the primacy for improving the structure-electronic properties of metal oxides and credence to its fore in the practical applications. Future research must focus on comparing the performances of ZnO, TiO2 and WO3 in parallel to get insight into their photocatalytic behaviors. Such comparisons not only reveal the changed surface-electronic structure upon various modifications, but also shed light on charge carrier dynamics, free radical generation, structural stability and compatibility for photocatalytic reactions. It is envisioned that these cardinal tactics have profound implications and can be replicated to other semiconductor photocatalysts like CeO2, In2O3, Bi2O3, Fe2O3, BiVO4, AgX, BiOX (X = Cl, Br & I), Bi2WO6, Bi2MoO6

  8. Effect of ZnO on phase emergence, microstructure and surface modifications of calcium phosphosilicate glass/glass-ceramics having iron oxide

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, K.; Dixit, A.; Bhattacharya, S.; Jagannath [Technical Physics and Prototype Engineering Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Deo, M.N. [High Pressure Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Kothiyal, G.P., E-mail: gpkoth@barc.gov.in [Technical Physics and Prototype Engineering Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

    2010-03-01

    The effect of ZnO on phase emergence and microstructure properties of glass and glass-ceramics with composition 25SiO{sub 2}-50CaO-15P{sub 2}O{sub 5}-(10 - x)Fe{sub 2}O{sub 3}-xZnO (where x = 0, 2, 5, 7 mol%) has been studied. They have been characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Surface modifications of these glass-ceramics in simulated body fluid have been studied using Fourier transform infrared reflection spectroscopy (FTIR), XPS and SEM. Results have shown a decrease in the fraction of non-bridging oxygen with increase in zinc oxide content. Emergence of crystalline phases in glass-ceramics at different heat treatment temperatures was studied using XRD. When glass is heat treated at 800 deg. C calcium phosphate, hematite and magnetite are developed as major phases in the glass-ceramics samples with ZnO up to 5 mol%. In addition to these, calcium silicate (Ca{sub 3}Si{sub 2}O{sub 7}) phase is also observed when glass is heat treated at 1000 deg. C. The microstructure of the glass-ceramics heat treated at 800 deg. C exhibits the formation of nano-size (40-50 nm) grains. On heat treatment at 1000 deg. C crystallites grow to above 50 nm size and more than one phase are observed in the microstructure. The formation of thin flake-like structure with coarse particles is observed at high zinc oxide concentration (x = 7 mol%). In vitro studies have shown the surface modifications and formation of Ca-P-rich layer on the glass-ceramics when immersed in simulated body fluids (SBF) for different durations. The bioactive response was found to depend on ZnO content.

  9. Effect of ZnO on phase emergence, microstructure and surface modifications of calcium phosphosilicate glass/glass-ceramics having iron oxide

    International Nuclear Information System (INIS)

    Sharma, K.; Dixit, A.; Bhattacharya, S.; Jagannath; Deo, M.N.; Kothiyal, G.P.

    2010-01-01

    The effect of ZnO on phase emergence and microstructure properties of glass and glass-ceramics with composition 25SiO 2 -50CaO-15P 2 O 5 -(10 - x)Fe 2 O 3 -xZnO (where x = 0, 2, 5, 7 mol%) has been studied. They have been characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Surface modifications of these glass-ceramics in simulated body fluid have been studied using Fourier transform infrared reflection spectroscopy (FTIR), XPS and SEM. Results have shown a decrease in the fraction of non-bridging oxygen with increase in zinc oxide content. Emergence of crystalline phases in glass-ceramics at different heat treatment temperatures was studied using XRD. When glass is heat treated at 800 deg. C calcium phosphate, hematite and magnetite are developed as major phases in the glass-ceramics samples with ZnO up to 5 mol%. In addition to these, calcium silicate (Ca 3 Si 2 O 7 ) phase is also observed when glass is heat treated at 1000 deg. C. The microstructure of the glass-ceramics heat treated at 800 deg. C exhibits the formation of nano-size (40-50 nm) grains. On heat treatment at 1000 deg. C crystallites grow to above 50 nm size and more than one phase are observed in the microstructure. The formation of thin flake-like structure with coarse particles is observed at high zinc oxide concentration (x = 7 mol%). In vitro studies have shown the surface modifications and formation of Ca-P-rich layer on the glass-ceramics when immersed in simulated body fluids (SBF) for different durations. The bioactive response was found to depend on ZnO content.

  10. Radiation defects in oxide crystals doped with rare earth ions

    NARCIS (Netherlands)

    Matkovskii, A; Durygin, A; Suchocki, A; Sugak, D; Wallrafen, F; Vakiv, M

    1999-01-01

    The nature of stable and transient color centers in Y3Al5O12, Gd3Ca5O12, YAlO3 and LiNbO3 crystals is studied. The color centers are created by various types of irradiation. The effect of irradiation on crystal optical properties in visible and ultraviolet range is presented.

  11. Defect free C-axis oriented zinc oxide (ZnO) films grown at room temperature using RF magnetron sputtering

    International Nuclear Information System (INIS)

    Kunj, Saurabh; Sreenivas, K.

    2016-01-01

    Radio frequency Magnetron sputtering technique was employed to fabricate ZnO thin films on quartz substrate at room temperature. The effect of varying oxygen to argon (O_2/Ar) gas ratio on the structural and photoluminescence properties of the film is analyzed.X-ray diffraction (XRD) spectra reveals the formation of hexagonal wurtzite structured ZnO thin films with preferred orientation along (002) plane. Photoluminescence (PL) characterization reveals the preparation of highly crystalline films exhibiting intense Ultraviolet (UV) emission with negligible amount of defects as indicated by the absence of Deep Level Emission (DLE) in the PL spectra.

  12. Defect free C-axis oriented zinc oxide (ZnO) films grown at room temperature using RF magnetron sputtering

    Science.gov (United States)

    Kunj, Saurabh; Sreenivas, K.

    2016-05-01

    Radio frequency Magnetron sputtering technique was employed to fabricate ZnO thin films on quartz substrate at room temperature. The effect of varying oxygen to argon (O2/Ar) gas ratio on the structural and photoluminescence properties of the film is analyzed.X-ray diffraction (XRD) spectra reveals the formation of hexagonal wurtzite structured ZnO thin films with preferred orientation along (002) plane. Photoluminescence (PL) characterization reveals the preparation of highly crystalline films exhibiting intense Ultraviolet (UV) emission with negligible amount of defects as indicated by the absence of Deep Level Emission (DLE) in the PL spectra.

  13. Defect free C-axis oriented zinc oxide (ZnO) films grown at room temperature using RF magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Kunj, Saurabh, E-mail: saurabhkunj22@gmail.com; Sreenivas, K. [Department of Physics & Astrophysics, University of Delhi, Delhi-110007 (India)

    2016-05-23

    Radio frequency Magnetron sputtering technique was employed to fabricate ZnO thin films on quartz substrate at room temperature. The effect of varying oxygen to argon (O{sub 2}/Ar) gas ratio on the structural and photoluminescence properties of the film is analyzed.X-ray diffraction (XRD) spectra reveals the formation of hexagonal wurtzite structured ZnO thin films with preferred orientation along (002) plane. Photoluminescence (PL) characterization reveals the preparation of highly crystalline films exhibiting intense Ultraviolet (UV) emission with negligible amount of defects as indicated by the absence of Deep Level Emission (DLE) in the PL spectra.

  14. DFT calculations on electronic properties of ZnO thin films deposited by spray pyrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Cordeiro, J.M.; Reynoso, V.C.; Azevedo, D.H.M. [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), SP (Brazil)

    2016-07-01

    Full text: Introduction - Thin films of Zinc oxide (ZnO) has a wide range of technological applications, as transparent conducting electrodes in solar cells, flat panel displays, and sensors, for example. More recently applications in optoelectronics, like light emitter diodes and laser diodes, due to its large band gap, are been explored. Studies of ZnO thin films are important for these applications. Methodology - In this study thin films of ZnO have been deposited by spray pyrolysis on glass substrate. The films were characterized by XRD and UV-VIS techniques and the electronic properties as a function of the film thickness have been investigated by DFT calculations with B3LYP hybrid potential implemented in the CRYSTAL09 code. Results - The diffractograms obtained for the ZnO thin films as a function of the thickness are shown. The films exhibit a hexagonal wurtzite structure with preferred c-axis orientation in (002) direction of ZnO crystal. A quantum mechanical approach based on the periodic Density Functional Theory (DFT), with B3LYP hybrid potential was used to investigate the electronic structure of the films as a function of the thickness. The CRYSTAL09 code has been used for the calculations on the wurtzite hexagonal structure of ZnO - spatial group P63mc. For optimizing the geometry of the pure ZnO crystal, the experimental lattice parameters were got as follows: a= 0.325 nm, b= 0.325 nm, c= 0.5207 nm with c/a= 1.602. Considering to the calculations of the band structure, it is suggested that the semiconducting properties of ZnO arises from the overlapping of the 4s orbital of the conducting band of Zn and the 2p orbital of the top of valence band of O. Conclusions - The structure of ZnO thin film deposited on glass substrate present preferential orientation in (002) direction. Variation in the optical properties as a function of the film thickness was observed. The band gap energy was determined from optical analysis to be ∼ 3.27 eV. The refractive

  15. Carbon dioxide adsorption on a ZnO(101[combining macron]0) substrate studied by infrared reflection absorption spectroscopy.

    Science.gov (United States)

    Buchholz, Maria; Weidler, Peter G; Bebensee, Fabian; Nefedov, Alexei; Wöll, Christof

    2014-01-28

    The adsorption of carbon dioxide on the mixed-terminated ZnO(101[combining macron]0) surface of a bulk single crystal was studied by UHV Infrared Reflection Absorption Spectroscopy (IRRAS). In contrast to metals, the classic surface selection rule for IRRAS does not apply to bulk oxide crystals, and hence vibrational bands can also be observed for s-polarized light. Although this fact substantially complicates data interpretation, a careful analysis allows for a direct determination of the adsorbate geometry. Here, we demonstrate the huge potential of IR-spectroscopy for investigations on oxide single crystal surfaces by considering all three components of the incident polarized light separately. We find that the tridentate (surface) carbonate is aligned along the [0001] direction. A comparison to data reported previously for CO2 adsorbed on the surfaces of ZnO nanoparticles provides important insight into the role of defects in the surface chemistry of powder particles.

  16. The formation of crystals in glasses containing rare earth oxides

    Energy Technology Data Exchange (ETDEWEB)

    Fadzil, Syazwani Mohd [Pohang University of Science and Technology (POSTECH), Pohang (Korea, Republic of); Hrma, Pavel [Pohang University of Science and Technology (POSTECH), Pohang, South Korea and Pacific Northwest National Laboratory, Richland, Washington (United States); Crum, Jarrod [Pacific Northwest National Laboratory, Richland, Washington (United States); Siong, Khoo Kok; Ngatiman, Mohammad Fadzlee; Said, Riduan Mt [National University of Malaysia, Bandar Baru Bangi, Selangor (Malaysia)

    2014-02-12

    Korean spent nuclear fuel will reach the capacity of the available temporary storage by 2016. Pyroprocessing and direct disposal seems to be an alternative way to manage and reuse spent nuclear fuel while avoiding the wet reprocessing technology. Pyroprocessing produces several wastes streams, including metals, salts, and rare earths, which must be converted into stabilized form. A suitable form for rare earth immobilization is borosilicate glass. The borosilicate glass form exhibits excellent durability, allows a high waste loading, and is easy to process. In this work, we combined the rare earths waste of composition (in wt%) 39.2Nd{sub 2}O{sub 3}–22.7CeO{sub 2}–11.7La{sub 2}O{sub 3}–10.9PrO{sub 2}–1.3Eu{sub 2}O{sub 3}–1.3Gd{sub 2}O{sub 3}–8.1Sm{sub 2}O{sub 3}–4.8Y{sub 2}O{sub 3} with a baseline glass of composition 60.2SiO{sub 2}–16.0B{sub 2}O{sub 3}–12.6Na{sub 2}O–3.8Al{sub 2}O{sub 3}–5.7CaO–1.7ZrO{sub 2}. Crystallization in waste glasses occurs as the waste loading increases. It may produce complicate glass processing and affect the product quality. To study crystal formation, we initially made glasses containing 5%, 10% and 15% of La{sub 2}O{sub 3} and then glasses with 5%, 10% and 15% of the complete rare earth mix. Samples were heat-treated for 24 hours at temperatures 800°C to 1150°C in 50°C increments. Quenched samples were analyzed using an optical microscope, scanning electron microscope with energy dispersive spectroscopy, and x-ray diffraction. Stillwellite (LaBSiO{sub 5}) and oxyapatite (Ca{sub 2}La{sub 8}Si{sub 6}O{sub 26}) were found in glasses containing La{sub 2}O{sub 3}, while oxyapatite (Ca{sub 2}La{sub 8}Si{sub 6}O{sub 26} and NaNd{sub 9}Si{sub 6}O{sub 26}) precipitated in glasses with additions of mixed rare earths. The liquidus temperature (T{sub L}) of the glasses containing 5%, 10% and 15% La{sub 2}O{sub 3} were 800°C, 959°C and 986°C, respectively; while T{sub L} was 825°C, 1059°C and 1267°C for glasses

  17. Structural, Optical and Electrical Properties of Transparent Conducting Oxide Based on Al Doped ZnO Prepared by Spray Pyrolysis

    Directory of Open Access Journals (Sweden)

    Abdeslam DOUAYAR

    2014-05-01

    Full Text Available Aluminum doped zinc oxide (AZO thin films were deposited on glass substrates at 350 °C by spray pyrolysis technique. X-ray diffraction patterns show that the undoped and AZO films exhibit the hexagonal wűrtzite crystal structure with a preferential orientation along 2 direction. AFM images showed that AZO film with 3 % of Al has a uniform grain sizes with a surface roughness of about 24 nm. All films present a high transmittance in the visible range. Both undoped and AZO films were n-type degenerate semiconductor and the best electrical resistivity value was around 8.0 ´ 10- 2 W.cm obtained for 3 % Al content.

  18. Fast response of carbon monoxide gas sensors using a highly porous network of ZnO nanoparticles decorated on 3D reduced graphene oxide

    Science.gov (United States)

    Ha, Nguyen Hai; Thinh, Dao Duc; Huong, Nguyen Thanh; Phuong, Nguyen Huy; Thach, Phan Duy; Hong, Hoang Si

    2018-03-01

    Zinc oxide (ZnO) nanoparticles loaded onto 3D reduced graphene oxide (3D-RGO) for carbon monoxide (CO) sensing were synthesized using hydrothermal method. The highly porous ZnO/3D-RGO configuration was stable without collapsing and was deposited on the micro-heater of the CO gas sensor. The resulting CO gas sensor displayed high sensitivity, fast response/recovery, and good linearity. The sensor achieved a response value of 85.2% for 1000 ppm CO at a working temperature of 200 °C. The response and recovery times of the sensor were 7 and 9 s for 1000 ppm CO at 200 °C. Similarly, the response value, response time, and recovery time of the sensor at room temperature were 27.5%, 14 s, and 15 s, respectively. The sensor demonstrated a distinct response to various CO concentrations in the range of 1-1000 ppm and good selectivity toward CO gas. In addition, the sensor exhibited good repeatability in multi-cycle and long-term stability.

  19. Hydrothermally grown ZnO nanorods on self-source substrate and their field emission

    International Nuclear Information System (INIS)

    Liu, J P; Xu, C X; Zhu, G P; Li, X; Cui, Y P; Yang, Y; Sun, X W

    2007-01-01

    Vertically aligned zinc oxide nanorod arrays were grown directly using a zinc foil as both source and substrate in pure water at low temperature by a simple hydrothermal reaction. The morphology and crystal structure of the ZnO nanorod arrays were examined by scanning electron microscopy, transmission electron microscopy and x-ray diffraction, respectively. The nanorods grew along the [0 0 0 1] direction and were 80 nm in diameter and almost 2 μm in length. Directly employing the zinc foil substrate as cathode, the field emission (FE) of the ZnO nanorods presented a two-stage slope behaviour in a ln(J/E 2 )-1/E plot according to the Fowler-Nordheim equation. The FE behaviour was investigated by considering the action of the defects in ZnO nanorods based on the measurement of the photoluminescence

  20. Growth of Comb-like ZnO Nanostructures for Dye-sensitized Solar Cells Applications

    Directory of Open Access Journals (Sweden)

    Umar Ahmad

    2009-01-01

    Full Text Available Abstract Dye-sensitized solar cells (DSSCs were fabricated by using well-crystallized ZnO nanocombs directly grown onto the fluorine-doped tin oxide (FTO via noncatalytic thermal evaporation process. The thin films of as-grown ZnO nanocombs were used as photoanode materials to fabricate the DSSCs, which exhibited an overall light to electricity conversion efficiency of 0.68% with a fill factor of 34%, short-circuit current of 3.14 mA/cm2, and open-circuit voltage of 0.671 V. To the best of our knowledge, this is first report in which thin film of ZnO nanocombs was used as photoanode materials to fabricate the DSSCs.

  1. Development of zinc oxide nanoparticle by sonochemical method and study of their physical and optical properties

    International Nuclear Information System (INIS)

    Khan, Samreen Heena; Suriyaprabha, R.; Pathak, Bhawana; Fulekar, M. H.

    2016-01-01

    With the miniaturization of crystal size, the fraction of under-coordinated surface atoms becomes dominant, and hence, materials in the nano-regime behave very differently from the similar material in a bulk. Zinc oxide (ZnO), particularly, exhibits extraordinary properties such as a wide direct band gap (3.37 eV), large excitation binding energy (60 meV), low refractive index (1.9), stability to intense ultraviolet (UV) illumination, resistance to high-energy irradiation, and lower toxicity as compared to other semiconductors. This very property makes Zinc Oxide a potential candidate in many application fields, particularly as a prominent semiconductor. Zinc Oxide plays a significant role in many technological advances with its application in semiconductor mediated photocatalytic processes and sensor, solar cells and others. In present study, Zinc Oxide (ZnO) has been synthesized using three different precursors by sonochemical method. Zinc Acetate Dihydrate, Zinc Nitrate Hexahydrate and Zinc Sulphate Heptahydrate used as a precursor for the synthesis process. The synthesized ZnO nanoparticle has been found under the range of ∼50 nm. Zinc oxide nanoparticles were characterized using different characterizing tools. The as-synthesized ZnO was characterized by Fourier Transform-Infrared Spectroscopy (FT-IR) for the determination of functional group; Scanning Electron Microscopy equipped with Energy Dispersive Spectroscopy (SEM-EDS) for Morphology and elemental detection respectively, Transmission Electron Microscopy for Particle size distribution and morphology and X-Ray Diffraction (XRD) for the confirmation of crystal structure of the nanomaterial. The optical properties of the ZnO were examined by UV-VIS spectroscopy equipped with Diffuse Reflectance spectroscopy (DRS) confirmed the optical band gap of ZnO-3 around 3.23 eV resembles with the band gap of bulk ZnO (3.37eV). The TEM micrograph of the as-synthesized material showed perfectly spherical shaped

  2. Development of zinc oxide nanoparticle by sonochemical method and study of their physical and optical properties

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Samreen Heena, E-mail: samreen.heena.khan@gmail.com; Suriyaprabha, R. [Centre for Nanosciences, Central University of Gujarat, Gandhinagar, India- 382030 (India); Pathak, Bhawana, E-mail: bhawana.pathak@cug.ac.in; Fulekar, M. H., E-mail: mhfulekar@yahoo.com [School of Environment and Sustainable Development, Central University of Gujarat, Gandhinagar, India- 382030 (India)

    2016-04-13

    With the miniaturization of crystal size, the fraction of under-coordinated surface atoms becomes dominant, and hence, materials in the nano-regime behave very differently from the similar material in a bulk. Zinc oxide (ZnO), particularly, exhibits extraordinary properties such as a wide direct band gap (3.37 eV), large excitation binding energy (60 meV), low refractive index (1.9), stability to intense ultraviolet (UV) illumination, resistance to high-energy irradiation, and lower toxicity as compared to other semiconductors. This very property makes Zinc Oxide a potential candidate in many application fields, particularly as a prominent semiconductor. Zinc Oxide plays a significant role in many technological advances with its application in semiconductor mediated photocatalytic processes and sensor, solar cells and others. In present study, Zinc Oxide (ZnO) has been synthesized using three different precursors by sonochemical method. Zinc Acetate Dihydrate, Zinc Nitrate Hexahydrate and Zinc Sulphate Heptahydrate used as a precursor for the synthesis process. The synthesized ZnO nanoparticle has been found under the range of ∼50 nm. Zinc oxide nanoparticles were characterized using different characterizing tools. The as-synthesized ZnO was characterized by Fourier Transform-Infrared Spectroscopy (FT-IR) for the determination of functional group; Scanning Electron Microscopy equipped with Energy Dispersive Spectroscopy (SEM-EDS) for Morphology and elemental detection respectively, Transmission Electron Microscopy for Particle size distribution and morphology and X-Ray Diffraction (XRD) for the confirmation of crystal structure of the nanomaterial. The optical properties of the ZnO were examined by UV-VIS spectroscopy equipped with Diffuse Reflectance spectroscopy (DRS) confirmed the optical band gap of ZnO-3 around 3.23 eV resembles with the band gap of bulk ZnO (3.37eV). The TEM micrograph of the as-synthesized material showed perfectly spherical shaped

  3. ZnO Coatings with Controlled Pore Size, Crystallinity and Electrical Conductivity

    Directory of Open Access Journals (Sweden)

    Roman SCHMACK

    2016-05-01

    Full Text Available Zinc oxide is a wide bandgap semiconductor with unique optical, electrical and catalytic properties. Many of its practical applications rely on the materials pore structure, crystallinity and electrical conductivity. We report a synthesis method for ZnO films with ordered mesopore structure and tuneable crystallinity and electrical conductivity. The synthesis relies on dip-coating of solutions containing micelles of an amphiphilic block copolymer and complexes of Zn2+ ions with aliphatic ligands. A subsequent calcination at 400°C removes the template and induces crystallization of the pore walls. The pore structure is controlled by the template polymer, whereas the aliphatic ligands control the crystallinity of the pore walls. Complexes with a higher thermal stability result in ZnO films with a higher content of residual carbon, smaller ZnO crystals and therefore lower electrical conductivity. The paper discusses the ability of different types of ligands to assist in the synthesis of mesoporous ZnO and relates the structure and thermal stability of the precursor complexes to the crystallinity and electrical conductivity of the zinc oxide.DOI: http://dx.doi.org/10.5755/j01.ms.22.1.8634

  4. Structural, spectroscopic and anti-microbial inspection of PEG capped ZnO nanoparticles for biomedical applications

    Science.gov (United States)

    Meshram, J. V.; Koli, V. B.; Kumbhar, S. G.; Borde, L. C.; Phadatare, M. R.; Pawar, S. H.

    2018-04-01

    Zinc oxide (ZnO) nanoparticles (NPs) have a wide range of biomedical applications. Present study demonstrates the new methodology in sol-gel technology for synthesizing Polyethylene glycol (PEG) capped ZnO NPs and its size effect on anti-microbial activity. The reaction time was increased from 1 h to 5 h for the synthesis of ZnO NPs at 130 °C. The size of PEG capped ZnO NPs is increased from 10 to 84 nm by increasing the reaction upto 5 h. The x-ray diffraction studies and transmission electron microscopy analysis reveals the phase purity and hexagonal wurtzite crystal structure with uniform PEG capping on the surface of ZnO NPs. UV–visible spectroscopy exhibits the peak at 366 nm which is attributed to ZnO NPs. No adverse effect is observed in case of absorbance spectroscopy. Further, Fourier transforms infrared spectroscopy and thermo gravimetric analysis depicts the adsorption of PEG molecules on the ZnO NPs surface. The anti-microbial activities for both Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria were studied by optical density (OD) mesurement. The remarkable anti-microbial activity was observed for PEG capped ZnO NPs synthesized at 1 h reaction time showing higher activity in comparison with that synthesized from 2 h to 5 h reaction time. The microbial growth was found to be inhibited after 10 h OD measurement for both the bacteria. The anti-microbial activity may be attributed to the generation of ROS and H2O2. However, these generated species plays a vital role in inhibition of microbial growth. Hence, PEG capped ZnO NPs has promising biomedical applications.

  5. Influence of electron irradiation on hydrothermally grown zinc oxide single crystals

    International Nuclear Information System (INIS)

    Lu, L W; So, C K; Zhu, C Y; Gu, Q L; Fung, S; Ling, C C; Li, C J; Brauer, G; Anwand, W; Skorupa, W

    2008-01-01

    The resistivity of hydrothermally grown ZnO single crystals increased from ∼10 3 Ω cm to ∼10 6 Ω cm after 1.8 MeV electron irradiation with a fluence of ∼10 16 cm −2 , and to ∼10 9 Ω cm as the fluence increased to ∼10 18 cm −2 . Defects in samples were studied by thermally stimulated current (TSC) spectroscopy and positron lifetime spectroscopy (PLS). After the electron irradiation with a fluence of 10 18 cm −2 , the normalized TSC signal increased by a factor of ∼100. A Zn vacancy was also introduced by the electron irradiation, though with a concentration lower than expected. After annealing in air at 400 °C, the resistivity and the deep traps concentrations recovered to the levels of the as-grown sample, and the Zn vacancy was removed

  6. Influence of electron irradiation on hydrothermally grown zinc oxide single crystals

    Science.gov (United States)

    Lu, L. W.; So, C. K.; Zhu, C. Y.; Gu, Q. L.; Li, C. J.; Fung, S.; Brauer, G.; Anwand, W.; Skorupa, W.; Ling, C. C.

    2008-09-01

    The resistivity of hydrothermally grown ZnO single crystals increased from ~103 Ω cm to ~106 Ω cm after 1.8 MeV electron irradiation with a fluence of ~1016 cm-2, and to ~109 Ω cm as the fluence increased to ~1018 cm-2. Defects in samples were studied by thermally stimulated current (TSC) spectroscopy and positron lifetime spectroscopy (PLS). After the electron irradiation with a fluence of 1018 cm-2, the normalized TSC signal increased by a factor of ~100. A Zn vacancy was also introduced by the electron irradiation, though with a concentration lower than expected. After annealing in air at 400 °C, the resistivity and the deep traps concentrations recovered to the levels of the as-grown sample, and the Zn vacancy was removed.

  7. Kinetic studies on the degradation of crystal violet by the Fenton oxidation process.

    Science.gov (United States)

    Wu, H; Fan, M M; Li, C F; Peng, M; Sheng, L J; Pan, Q; Song, G W

    2010-01-01

    The degradation of dye crystal violet (CV) by Fenton oxidation process was investigated. The UV-Vis spectrogram has shown that CV can be degraded effectively by Fenton oxidation process. Different system variables namely initial H(2)O(2) concentration, initial Fe(2 + ) concentration and reaction temperature, which have effect on the degradation of CV by Fenton oxidation process, have been studied systematically. The degradation kinetics of CV was also elucidated based on the experimental data. The degradation of CV obeys the first-order reaction kinetics. The kinetic model can be described as k=1.5 exp(-(7.5)/(RT))[H(2)O(2)](0)(0.8718)[Fe(2+)](0)(0.5062). According to the IR spectrogram, it is concluded that the benzene ring of crystal violet has been destroyed by Fenton oxidation. The result will be useful in treating dyeing wastewater containing CV by Fenton oxidation process.

  8. Synthesis and crystal kinetics of cerium oxide nanocrystallites prepared by co-precipitation process

    International Nuclear Information System (INIS)

    Shih, C.J.; Chen, Y.J.; Hon, M.H.

    2010-01-01

    Cerium oxide nanocrystallites were synthesized at a relatively low temperature using cerium nitrate as starting materials in a water solution by a co-precipitation process. Effect of calcination temperature on the crystallite growth of cerium oxide nano-powders was investigated by X-ray diffraction, transmission electron microscopy and electron diffraction. The crystallization temperature of the cerium oxide powders was estimated to be about 273 K by XRD analysis. When calcined from 473 to 1273 K, the crystallization of the face-centered cubic phase was observed by XRD. The crystallite size of the cerium oxide increased from 10.0 to 43.8 nm with calcining temperature increasing from 673 to 1273 K. The activation energy for growth of cerium oxide nanoparticles was found to be 16.0 kJ mol -1 .

  9. Synthesis and crystal kinetics of cerium oxide nanocrystallites prepared by co-precipitation process

    Energy Technology Data Exchange (ETDEWEB)

    Shih, C.J., E-mail: cjshih@kmu.edu.tw [Department of Fragrance and Cosmetics Science, Kaohsiung Medical University, 100 Shi-Chuan 1st Road, Kaohsiung 807, Taiwan (China); Chen, Y.J. [Institute of Biomedical Sciences, National Sun Yat-Sen University, Kaohsiung 804, Taiwan (China); Hon, M.H. [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan (China)

    2010-05-15

    Cerium oxide nanocrystallites were synthesized at a relatively low temperature using cerium nitrate as starting materials in a water solution by a co-precipitation process. Effect of calcination temperature on the crystallite growth of cerium oxide nano-powders was investigated by X-ray diffraction, transmission electron microscopy and electron diffraction. The crystallization temperature of the cerium oxide powders was estimated to be about 273 K by XRD analysis. When calcined from 473 to 1273 K, the crystallization of the face-centered cubic phase was observed by XRD. The crystallite size of the cerium oxide increased from 10.0 to 43.8 nm with calcining temperature increasing from 673 to 1273 K. The activation energy for growth of cerium oxide nanoparticles was found to be 16.0 kJ mol{sup -1}.

  10. UiO-66-NH2 Metal-Organic Framework (MOF) Nucleation on TiO2, ZnO, and Al2O3 Atomic Layer Deposition-Treated Polymer Fibers: Role of Metal Oxide on MOF Growth and Catalytic Hydrolysis of Chemical Warfare Agent Simulants.

    Science.gov (United States)

    Lee, Dennis T; Zhao, Junjie; Oldham, Christopher J; Peterson, Gregory W; Parsons, Gregory N

    2017-12-27

    Metal-organic frameworks (MOFs) chemically bound to polymeric microfibrous textiles show promising performance for many future applications. In particular, Zr-based UiO-66-family MOF-textiles have been shown to catalytically degrade highly toxic chemical warfare agents (CWAs), where favorable MOF/polymer bonding and adhesion are attained by placing a nanoscale metal-oxide layer on the polymer fiber preceding MOF growth. To date, however, the nucleation mechanism of Zr-based MOFs on different metal oxides and how product performance is affected are not well understood. Herein, we provide new insight into how different inorganic nucleation films (i.e., Al 2 O 3 , ZnO, or TiO 2 ) conformally coated on polypropylene (PP) nonwoven textiles via atomic layer deposition (ALD) influence the quality, overall surface area, and the fractional yield of UiO-66-NH 2 MOF crystals solvothermally grown on fiber substrates. Of the materials explored, we find that TiO 2 ALD layers lead to the most effective overall MOF/fiber adhesion, uniformity, and a rapid catalytic degradation rate for a CWA simulant, dimethyl p-nitrophenyl phosphate (DMNP) with t 1/2 = 15 min, 580-fold faster than the catalytic performance of untreated PP textiles. Interestingly, compared to ALD TiO 2 and Al 2 O 3 , ALD ZnO induces a larger MOF yield in solution and mass loading on PP fibrous mats. However, this larger MOF yield is ascribed to chemical instability of the ZnO layer under MOF formation condition, leading to Zn 2+ ions that promote further homogeneous MOF growth. Insights presented here improve understanding of compatibility between active MOF materials and substrate surfaces, which we believe will help advanced MOF composite materials for a variety of useful functions.

  11. The influence of defect drift in external electric field on green luminescence of ZnO single crystals

    International Nuclear Information System (INIS)

    Korsunska, N.O.; Borkovska, L.V.; Bulakh, B.M.; Khomenkova, L.Yu.; Kushnirenko, V.I.; Markevich, I.V.

    2003-01-01

    In nominally undoped Zn O single crystals, the influence of electric field on photoluminescence in visible wavelength range was investigated. A well-known broad unstructured band consisting of green and orange ones was observed. It was found that the action of direct electric field of about 100 V/cm at 600-700 deg. C resulted in the increase of green band intensity near the cathode and its decrease near the anode, while orange band intensity was not influenced by this treatment. The redistribution of green band intensity along the sample under electric field is accounted for by drift of zinc interstitials from the anode to the cathode. It is supposed that emitting centres responsible for green luminescence are complex defects including zinc interstitials

  12. Crystal size effect on the electrochemical oxidation of formate on carbon-supported palladium nanoparticles

    International Nuclear Information System (INIS)

    Santos, Rayana Marcela Izidoro da Silva; Nakazato, Roberto Zenhei; Ciapina, Eduardo Goncalves

    2016-01-01

    Full text: The electrochemical oxidation of formate in alkaline electrolytes has emerged an a promising anodic reaction in the Direct Formate Fuel Cells[1]. Although palladium is considered to be one of the best electro catalyst for the oxidation of formate, important structure-activity relationships are still not understood. In the present work, we investigated the effect of the size of the palladium crystals in the electrochemical oxidation of formate in 0.1 mol L -1 KOH. Carbon-supported palladium nanoparticles (Pd/C) were prepared by chemical reduction of palladium (II) chloride in aqueous media by sodium borohydride in the presence of varying quantities of sodium citrate in the reaction media to obtain metallic crystals with distinct sizes. Analysis of the X-ray diffraction profile revealed the presence of palladium crystals in the range of 6 to 19 nm. Potentiostatic oxidation of formate on the distinct Pd/C samples revealed a volcano-like dependence of the specific activity with the size of the palladium crystals, presenting the highest activity for crystals around 7.5 nm. Reference: [1] A.M. Bartrom, J.L. Haan, The direct formate fuel cell with an alkaline anion exchange membrane, J. Power Sources. 214 (2012) 68-74. (author)

  13. Effects of preannealing temperature of ZnO thin films on the performance of dye-sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Kao, M.C.; Chen, H.Z.; Young, S.L. [Hsiuping Institute of Technology, Department of Electronic Engineering, Taichung (China)

    2010-03-15

    The preferred (002) orientation zinc oxide (ZnO) nanocrystalline thin films have been deposited on FTO-coated glass substrates by sol-gel spin-coating technology and rapid thermal annealing for use in dye-sensitized solar cells (DSSC). The effects of preannealing temperature (100 and 300 C) on the microstructure, morphology and optical properties of ZnO thin films were studied. The ZnO thin films were characterized by X-ray diffraction (XRD), scanning electron microscopic (SEM) and Brunauer-Emmett-Teller (BET) analysis. The photoelectric performance of DSSC was studied by I-V curve and the incident photon-to-current conversion efficiency (IPCE), respectively. From the results, the intensities of (002) peaks of ZnO thin films increases with increasing preannealing temperature from 100 C to 300 C. The increase in pore size and surface area of ZnO films crystallized at the increased preannealing temperature contributed to the improvement on the absorption of N3 dye onto the films, the short-circuit photocurrent (J{sub sc}) and open-circuit voltage (V{sub oc}) of DSSC. The higher efficiency ({eta}) of 2.5% with J{sub sc} and V{sub oc} of 8.2 mA/cm{sup 2} and 0.64 V, respectively, was obtained by the ZnO film preannealed at 300 C. (orig.)

  14. Residual stress and bending strength of ZnO films deposited on polyimide sheet by RF sputtering system

    Energy Technology Data Exchange (ETDEWEB)

    Kusaka, Kazuya, E-mail: kusaka@tokushima-u.ac.jp [Institute of Technology and Science, Tokushima University, 2-1, Minamijosanjima, Tokushima, Tokushima 7708506 (Japan); Maruoka, Yutaka, E-mail: ymaruoka1116@gmail.com [Graduate School of Advanced Technology and Science, Tokushima University, 2-1, Minamijosanjima, Tokushima, Tokushima 7708506 (Japan); Matsue, Tatsuya, E-mail: tmatsue@mat.niihama-nct.ac.jp [Department of Environmental Materials Engineering National Institute of Technology, NIIHAMA College, 7-1, Yakumo-cho, Niihama, Ehime 7928580 (Japan)

    2016-05-15

    Zinc oxide (ZnO) films were deposited on a soft polyimide sheet substrate by radio frequency sputtering with a ZnO powder target, and the films' crystal orientations and residual stress were investigated using x-ray diffraction as a function of substrate temperature. C-axis oriented ZnO films were achieved using this ZnO powder target method. The ZnO films exhibited high compressive residual stresses between −0.7 and −1.4 GPa. Finally, the authors examined the strength of the obtained film by applying tensile bending loads. No cracks were observed on the surfaces of the ZnO films after a bending test using cylinders with diameters >25 mm. After a bending test using a cylinder with a diameter of 19 mm, large cracks were formed on the films. Therefore, the authors concluded that the tensile bending strength of the obtained films was greater than ∼420 MPa.

  15. Effects of growth duration on the structural and optical properties of ZnO nanorods grown on seed-layer ZnO/polyethylene terephthalate substrates

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Y.I.; Shin, C.M.; Heo, J.H. [Department of Nano Systems Engineering, Center for Nano Manufacturing Inje University, Gimhae, Gyeongnam 621-749 (Korea, Republic of); Ryu, H., E-mail: hhryu@inje.ac.kr [Department of Nano Systems Engineering, Center for Nano Manufacturing Inje University, Gimhae, Gyeongnam 621-749 (Korea, Republic of); Lee, W.J. [Department of Nano Engineering, Dong-Eui University, Busan 614-714 (Korea, Republic of); Chang, J.H. [Major of Nano Semiconductor, Korea Maritime University, Busan 606-791 (Korea, Republic of); Son, C.S. [Department of Electronic Materials Engineering, Silla University, Busan 617-736 (Korea, Republic of); Yun, J. [Department of Nano Science and Engineering, Institute of Advanced Materials Kyungnam University, Changwon, Gyeongnam 631-701 (Korea, Republic of)

    2011-10-01

    Well-aligned single crystalline zinc oxide (ZnO) nanorods were successfully grown, by hydrothermal synthesis at a low temperature, on flexible polyethylene terephthalate (PET) substrates with a seed layer. Photoluminescence (PL), field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) measurements were used to analyze the optical and structural properties of ZnO nanorods grown for various durations from 0.5 h to 10 h. Regular and well-aligned ZnO nanorods with diameters ranging from 62 nm to 127 nm and lengths from 0.3 {mu}m to 1.65 {mu}m were formed after almost 5 h of growth. The growth rate of ZnO grown on PET substrates is lower than that grown on Si (1 0 0) substrates. Enlarged TEM images show that the tips of the ZnO nanorods grown for 6 h have a round shape, whereas the tips grown for 10 h are sharpened. The crystal properties of ZnO nanorods can be tuned by using the growth duration as a growth condition. The XRD and PL results indicate that the structural and optical properties of the ZnO nanorods are most improved after 5 h and 6 h of growth, respectively.

  16. Bias-polarity-dependent UV/visible transferable electroluminescence from ZnO nanorod array LED with graphene oxide electrode supporting layer

    Science.gov (United States)

    Liu, Weizhen; Wang, Wei; Xu, Haiyang; Li, Xinghua; Yang, Liu; Ma, Jiangang; Liu, Yichun

    2015-09-01

    A simple top electrode preparation process, employing continuous graphene oxide films as electrode supporting layers, was adopted to fabricate a ZnO nanorod array/p-GaN heterojunction LED. The achieved LED demonstrated different electroluminescence behaviors under forward and reverse biases: a yellow-red emission band was observed under forward bias, whereas a blue-UV emission peak was obtained under reverse bias. Electroluminescence spectra under different currents and temperatures, as well as heterojunction energy-band alignments, reveal that the yellow-red emission under forward bias originates from recombinations related to heterointerface defects, whereas the blue-UV electroluminescence under reverse bias is ascribed to transitions from near-band-edge and Mg-acceptor levels in p-GaN.

  17. Preparation of ZnO nanocrystals via ultrasonic irradiation

    DEFF Research Database (Denmark)

    Qian, D.; Jiang, Jianzhong; Hansen, P. L.

    2003-01-01

    A simple and rapid process has been developed for the preparation of nanometer-sized ZnO crystals via ultrasonic irradiation, by which pure ZnO nanocrystals with an average size of 6 nm and narrow size distribution can be synthesized in a short time and without using any solvents for the precipit......A simple and rapid process has been developed for the preparation of nanometer-sized ZnO crystals via ultrasonic irradiation, by which pure ZnO nanocrystals with an average size of 6 nm and narrow size distribution can be synthesized in a short time and without using any solvents...

  18. Preparation and characterization of ZnO transparent semiconductor thin films by sol-gel method

    International Nuclear Information System (INIS)

    Tsay, Chien-Yie; Fan, Kai-Shiung; Chen, Sih-Han; Tsai, Chia-Hao

    2010-01-01

    Transparent semiconductor thin films of zinc oxide (ZnO) were deposited onto alkali-free glass substrates by the sol-gel method and spin-coating technique. In this study, authors investigate the influence of the heating rate of the preheating process (4 or 10 o C/min) on the crystallization, surface morphology, and optical properties of sol-gel derived ZnO thin films. The ZnO sol was synthesized by dissolving zinc acetate dehydrate in ethanol, and then adding monoethanolamine. The as-coated films were preheated at 300 o C for 10 min and annealed at 500 o C for 1 h in air ambiance. Experimental results indicate that the heating rate of the preheating process strongly affected the surface morphology and transparency of ZnO thin film. Specifically, a heating rate of 10 o C/min for the preheating process produces a preferred orientation along the (0 0 2) plane and a high transmittance of 92% at a wavelength of 550 nm. Furthermore, this study reports the fabrication of thin-film transistors (TFTs) with a transparent ZnO active channel layer and evaluates their electrical performance.

  19. Synthesis, effect of capping agents, structural, optical and photoluminescence properties of ZnO nanoparticles

    International Nuclear Information System (INIS)

    Singh, A.K.; Viswanath, V.; Janu, V.C.

    2009-01-01

    Zinc oxide nanoparticles were synthesized using chemical method in alcohol base. During synthesis three capping agents, i.e. triethanolamine (TEA), oleic acid and thioglycerol, were used and the effect of concentrations was analyzed for their effectiveness in limiting the particle growth. Thermal stability of ZnO nanoparticles prepared using TEA, oleic acid and thioglycerol capping agents, was studied using thermogravimetric analyzer (TGA). ZnO nanoparticles capped with TEA showed maximum weight loss. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for structural and morphological characterization of ZnO nanoparticles. Particle size was evaluated using effective mass approximation method from UV-vis spectroscopy and Scherrer's formula from XRD patterns. XRD analysis revealed single crystal ZnO nanoparticles of size 12-20 nm in case of TEA capping. TEA, oleic acid and thioglycerol capped synthesized ZnO nanoparticles were investigated at room temperature photoluminescence for three excitation wavelengths i.e. 304, 322 and 325 nm, showing strong peaks at about 471 nm when excited at 322 and 325 nm whereas strong peak was observed at 411 for 304 nm excitation.

  20. On-chip surface modified nanostructured ZnO as functional pH sensors

    International Nuclear Information System (INIS)

    Zhang, Qing; Liu, Wenpeng; Sun, Chongling; Zhang, Hao; Pang, Wei; Zhang, Daihua; Duan, Xuexin

    2015-01-01

    Zinc oxide (ZnO) nanostructures are promising candidates as electronic components for biological and chemical applications. In this study, ZnO ultra-fine nanowire (NW) and nanoflake (NF) hybrid structures have been prepared by Au-assisted chemical vapor deposition (CVD) under ambient pressure. Their surface morphology, lattice structures, and crystal orientation were investigated by scanning electron microscopy (SEM), x-ray diffraction (XRD), and transmission electron microscopy (TEM). Two types of ZnO nanostructures were successfully integrated as gate electrodes in extended-gate field-effect transistors (EGFETs). Due to the amphoteric properties of ZnO, such devices function as pH sensors. We found that the ultra-fine NWs, which were more than 50 μm in length and less than 100 nm in diameter, performed better in the pH sensing process than NW–NF hybrid structures because of their higher surface-to-volume ratio, considering the Nernst equation and the Gouy–Chapman–Stern model. Furthermore, the surface coating of (3-Aminopropyl)triethoxysilane (APTES) protects ZnO nanostructures in both acidic and alkaline environments, thus enhancing the device stability and extending its pH sensing dynamic range. (paper)

  1. Controlled Al3+ Incorporation in the ZnO Lattice at 188 °C by Soft Reactive Co-Sputtering for Transparent Conductive Oxides

    Directory of Open Access Journals (Sweden)

    Salvatore Sanzaro

    2016-06-01

    Full Text Available Transparent conductive oxide (TCO layers, to be implemented in photo-anodes for dye-sensitized solar cells (DSCs, were prepared by co-deposition of ZnO and Al using pulsed-direct current (DC-magnetron reactive sputtering processes. The films were deposited at low deposition temperatures (RT-188 °C and at fixed working pressure (1.4 Pa using soft power loading conditions to avoid intrinsic extra-heating. To compensate the layer stoichiometry, O2 was selectively injected close to the sample in a small percentage (Ar:O2 = 69 sccm:2 sccm. We expressly applied the deposition temperature as a controlling parameter to tune the incorporation of the Al3+ species in the targeted position inside the ZnO lattice. With this method, Aluminum-doped Zinc Oxide films (ZnO:Al were grown following the typical wurtzite structure, as demonstrated by X-ray Diffraction analyses. A combination of micro-Raman, X-ray photoelectron spectroscopy (XPS and spectroscopic ellipsometry (SE analyses has shown that the incorporated host-atoms are Al3+ species in Zn2+ substitutional position; their amount increases following a direct monotonic trend with the deposition temperature. Correspondently, the c-axis strain into the layer decreases due to the progressive ordering of the lattice structure and reducing clustering phenomena. The maximum average Al content inside the film was ~2%, as measured by energy dispersive X-ray (EDX spectroscopy, with a uniform distribution of the dopant species along the layer thickness traced by depth-profile XPS analyses. The optimised ZnO:Al layer, deposited at a rate of ~7 nm/min, exhibits high transmittance in the visible range (~85% and low resistivity values (~13 mΩ × cm. The material therefore fulfils all the requirements to be candidate as TCO for low-cost DSCs on flexible substrates for large area technologies.

  2. Zinc oxide crystal whiskers as a novel sorbent for solid-phase extraction of flavonoids.

    Science.gov (United States)

    Wang, Licheng; Shangguan, Yangnan; Hou, Xiudan; Jia, Yong; Liu, Shujuan; Sun, Yingxin; Guo, Yong

    2017-08-15

    As a novel solid-phase extraction material, zinc oxide crystal whiskers were used to extract flavonoid compounds and showed good extraction abilities. X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy and surface area/pore volume characterized the sorbent. The zinc oxide was packed into a solid-phase extraction micro-column and its extraction ability was evaluated by four model flavonoid compounds. The sample loading and elution parameters were optimized and the zinc oxide based analytical method for flavonoids was established. It showed that the method has wide linearities from 1 to 150μg/L and low limits of detection at 0.25μg/L. The relative standard deviations of a single column repeatability and column to column reproducibility were less than 6.8% and 10.6%. Several real samples were analyzed by the established method and satisfactory results were obtained. The interactions between flavonoids and zinc oxide were calculated and proved to be from the Van der Waals' forces between the 4p and 5d orbitals from zinc atom and the neighboring π orbitals from flavonoid phenyl groups. Moreover, the zinc oxide crystal whiskers showed good stability and could be reused more than 50 times under the operation conditions. This work proves that the zinc oxide crystal whiskers are a good candidate for flavonoids enrichment. Copyright © 2017. Published by Elsevier B.V.

  3. Controlling growth rate anisotropy for formation of continuous ZnO thin films from seeded substrates

    International Nuclear Information System (INIS)

    Zhang, R H; Slamovich, E B; Handwerker, C A

    2013-01-01

    Solution-processed zinc oxide (ZnO) thin films are promising candidates for low-temperature-processable active layers in transparent thin film electronics. In this study, control of growth rate anisotropy using ZnO nanoparticle seeds, capping ions, and pH adjustment leads to a low-temperature (90 ° C) hydrothermal process for transparent and high-density ZnO thin films. The common 1D ZnO nanorod array was grown into a 2D continuous polycrystalline film using a short-time pure solution method. Growth rate anisotropy of ZnO crystals and the film morphology were tuned by varying the chloride (Cl − ) ion concentration and the initial pH of solutions of zinc nitrate and hexamethylenetetramine (HMTA), and the competitive adsorption effects of Cl − ions and HMTA ligands on the anisotropic growth behavior of ZnO crystals were proposed. The lateral growth of nanorods constituting the film was promoted by lowering the solution pH to accelerate the hydrolysis of HMTA, thereby allowing the adsorption effects from Cl − to dominate. By optimizing the growth conditions, a dense ∼100 nm thickness film was fabricated in 15 min from a solution of [Cl − ]/[Zn 2+ ] = 1.5 and pH= 4.8 ± 0.1. This film shows >80% optical transmittance and a field-effect mobility of 2.730 cm 2 V −1 s −1 at zero back-gate bias. (paper)

  4. The thickness of native oxides on aluminum alloys and single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Evertsson, J., E-mail: jonas.evertsson@sljus.lu.se [Division of Synchrotron Radiation Research, Lund University, Box 118, 221 00 Lund (Sweden); Bertram, F. [Division of Synchrotron Radiation Research, Lund University, Box 118, 221 00 Lund (Sweden); Zhang, F. [KTH Royal Institute of Technology, Department of Chemistry, Division of Surface and Corrosion Science, Drottning Kristinas Vg 51, 100 44 Stockholm (Sweden); Rullik, L.; Merte, L.R.; Shipilin, M. [Division of Synchrotron Radiation Research, Lund University, Box 118, 221 00 Lund (Sweden); Soldemo, M.; Ahmadi, S. [KTH Royal Institute of Technology, ICT, Material Physics, 16440 Kista (Sweden); Vinogradov, N.; Carlà, F. [ESRF, B.P. 220, 38043 Grenoble (France); Weissenrieder, J.; Göthelid, M. [KTH Royal Institute of Technology, ICT, Material Physics, 16440 Kista (Sweden); Pan, J. [KTH Royal Institute of Technology, Department of Chemistry, Division of Surface and Corrosion Science, Drottning Kristinas Vg 51, 100 44 Stockholm (Sweden); Mikkelsen, A. [Division of Synchrotron Radiation Research, Lund University, Box 118, 221 00 Lund (Sweden); Nilsson, J.-O. [Sapa Technology, Kanalgatan 1, 612 31 Finspång (Sweden); Lundgren, E. [Division of Synchrotron Radiation Research, Lund University, Box 118, 221 00 Lund (Sweden)

    2015-09-15

    Highlights: • We have determined the native oxide film thickness on several Al samples. • The results obtained from XRR and XPS show excellent agreement. • The results obtained from EIS show consistently thinner oxide films. • The oxides on the alloys are thicker than the oxides on the single crystals. - Abstract: We present results from measurements of the native oxide film thickness on four different industrial aluminum alloys and three different aluminum single crystals. The thicknesses were determined using X-ray reflectivity, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy. In addition, atomic force microscopy was used for micro-structural studies of the oxide surfaces. The reflectivity measurements were performed in ultra-high vacuum, vacuum, ambient, nitrogen and liquid water conditions. The results obtained using X-ray reflectivity and X-ray photoelectron spectroscopy demonstrate good agreement. However, the oxide thicknesses determined from the electrochemical impedance spectroscopy show a larger discrepancy from the above two methods. In the present contribution the reasons for this discrepancy are discussed. We also address the effect of the substrate type and the presence of water on the resultant oxide thickness.

  5. Low temperature delayed recombination decay in complex oxide scintillating crystals

    Czech Academy of Sciences Publication Activity Database

    Mihóková, Eva; Jarý, Vítězslav; Schulman, L. S.; Nikl, Martin

    2014-01-01

    Roč. 61, č. 1 (2014), 257-261 ISSN 0018-9499 R&D Projects: GA MŠk LH12150; GA MŠk LH12185 Grant - others:AVČR(CZ) M100101212 Institutional support: RVO:68378271 Keywords : luminescence * oxides * scintillator * tunneling Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.283, year: 2014

  6. Synthesis of highly conductive thin-walled Al-doped ZnO single-crystal microtubes by a solid state method

    Science.gov (United States)

    Hu, Shuopeng; Wang, Yue; Wang, Qiang; Xing, Cheng; Yan, Yinzhou; Jiang, Yijian

    2018-06-01

    ZnO has attracted considerable attention in fundamental studies and practical applications for the past decade due to its outstanding performance in gas sensing, photocatalytic degradation, light harvesting, UV-light emitting/lasing, etc. The large-sized thin-walled ZnO (TW-ZnO) microtube with stable and rich VZn-related acceptors grown by optical vapor supersaturated precipitation (OVSP) is a novel multifunctional optoelectronic material. Unfortunately, the OVSP cannot achieve doping due to the vapor growth process. To obtain doped TW-ZnO microtubes, a solid state method is introduced in this work to achieve thin-walled Al-doping ZnO (TW-ZnO:Al) microtubes with high electrical conductivity. The morphology and microstructures of ZnO:Al microtubes are similar to undoped ones. The Al3+ ions are confirmed to substitute Zn2+ sites and Zn(0/-1) vacancies in the lattice of ZnO by EDS, XRD, Raman and temperature-dependent photoluminescence analyses. The Al dopant acting as a donor level offers massive free electrons to increase the carrier concentrations. The resistivity of the ZnO:Al microtube is reduced down to ∼10-3 Ω·cm, which is one order of magnitude lower than that of the undoped microtube. The present work provides a simple way to achieve doped ZnO tubular components for potential device applications in optoelectronics.

  7. Eliminating Crystals in Non-Oxide Optical Fiber Preforms and Optical Fibers

    Science.gov (United States)

    Tucker, Dennis S.; LaPointe, Michael R.

    2012-01-01

    Non ]oxide fiber optics such as heavy metal fluoride and chalcogenide glasses are extensively used in infrared transmitting applications such as communication systems, chemical sensors, and laser fiber guides for cutting, welding and medical surgery. The addition of rare earths such as erbium, enable these materials to be used as fiber laser and amplifiers. Some of these glasses however are very susceptible to crystallization. Even small crystals can lead to light scatter and a high attenuation coefficient, limiting their usefulness. Previously two research teams found that microgravity suppressed crystallization in heavy metal fluoride glasses. Looking for a less expensive method to suppress crystallization, ground based research was performed utilizing an axial magnetic field. The experiments revealed identical results to those obtained via microgravity processing. This research then led to a patented process for eliminating crystals in optical fiber preforms and the resulting optical fibers. In this paper, the microgravity results will be reviewed as well as patents and papers relating to the use of magnetic fields in various material and glass processing applications. Finally our patent to eliminate crystals in non ]oxide glasses utilizing a magnetic field will be detailed.

  8. Preparation of Zinc Oxide (ZnO) Thin Film as Transparent Conductive Oxide (TCO) from Zinc Complex Compound on Thin Film Solar Cells: A Study of O2 Effect on Annealing Process

    Science.gov (United States)

    Muslih, E. Y.; Kim, K. H.

    2017-07-01

    Zinc oxide (ZnO) thin film as a transparent conductive oxide (TCO) for thin film solar cell application was successfully prepared through two step preparations which consisted of deposition by spin coating at 2000 rpm for 10 second and followed by annealing at 500 °C for 2 hours under O2 and ambient atmosphere. Zinc acetate dehydrate was used as a precursor which dissolved in ethanol and acetone (1:1 mol) mixture in order to make a zinc complex compound. In this work, we reported the O2 effect, reaction mechanism, structure, morphology, optical and electrical properties. ZnO thin film in this work shows a single phase of wurtzite, with n-type semiconductor and has band gap, carrier concentration, mobility, and resistivity as 3.18 eV, 1.21 × 10-19cm3, 11 cm2/Vs, 2.35 × 10-3 Ωcm respectively which is suitable for TCO at thin film solar cell.

  9. Studying Impact of Different Precipitating Agents on Crystal Structure, Morphology and Photocatalytic Activity of Bismuth Oxide

    Directory of Open Access Journals (Sweden)

    Yayuk Astuti

    2017-10-01

    How to Cite: Astuti, Y., Arnelli, Pardoyo, Fauziyah, A., Nurhayati, S., Wulansari, A.D., Andianingrum, R., Widiyandari, H., Bhaduri, G.A. (2017. Studying Impact of Different Precipitating Agents on Crystal Structure, Morphology and Photocatalytic Activity of Bismuth Oxide. Bulletin of Chemical Reaction Engineering & Catalysis, 12 (3: 478-484 (doi:10.9767/bcrec.12.3.1144.478-484

  10. Hysteresis losses in iron oxide nanoparticles prepared by glass crystallization or wet chemical precipitation

    International Nuclear Information System (INIS)

    Mueller, Robert; Dutz, Silvio; Hergt, Rudolf; Schmidt, Christopher; Steinmetz, Hanna; Zeisberger, Matthias; Gawalek, Wolfgang

    2007-01-01

    Ferrofluids were prepared from glass crystallized as well as wet precipitated iron oxide particles. Comparing hysteresis losses versus applied field amplitude from particles in immobilized state (powder) and in fluid state (ferrofluid) shows in some cases anomalous large losses at low magnetic fields. The influence of texture on the losses was investigated

  11. DT fusion neutron irradiation of ORNL magnesium oxide crystals and BNL--LASL superconductor wires

    International Nuclear Information System (INIS)

    MacLean, S.C.

    1978-01-01

    The DT fusion neutron irradiation of two ORNL magnesium oxide crystals and eleven BNL-LASL superconductor wires is described. The sample position and neutron dose record are given. The maximum neutron fluence on any sample was 2.16 x 10 16 neutrons/cm 2

  12. Crystallization and unusual rheological behavior in poly(ethylene oxide)–clay nanocomposites

    KAUST Repository

    Kelarakis, Antonios; Giannelis, Emmanuel P.

    2011-01-01

    We report a systematic study of the crystallization and rheological behavior of poly(ethylene oxide) (PEO)-clay nanocomposites. To that end a series of nanocomposites based on PEOs of different molecular weight (103 < MW < 105 g/mol) and clay

  13. Oxidation kinetics of crystal violet by potassium permanganate in acidic medium

    Science.gov (United States)

    Khan, Sameera Razi; Ashfaq, Maria; Mubashir; Masood, Summyia

    2016-05-01

    The oxidation kinetics of crystal violet (a triphenylmethane dye) by potassium permanganate was focused in an acidic medium by the spectrophotometric method at 584 nm. The oxidation reaction of crystal violet by potassium permanganate is carried out in an acidic medium at different temperatures ranging within 298-318 K. The kinetic study was carried out to investigate the effect of the concentration, ionic strength and temperature. The reaction followed first order kinetics with respect to potassium permanganate and crystal violet and the overall rate of the reaction was found to be second order. Thermodynamic activation parameters like the activation energy ( E a), enthalpy change (Δ H*), free energy change (Δ G*), and entropy change (Δ S*) have also been evaluated.

  14. Ultrasonic synthesis of fern-like ZnO nanoleaves and their enhanced photocatalytic activity

    International Nuclear Information System (INIS)

    Ma, Qing Lan; Xiong, Rui; Zhai, Bao-gai; Huang, Yuan Ming

    2015-01-01

    Graphical abstract: - Highlights: • Fern-like ZnO nanoleaves were synthesized by ultrasonicating Zn microcrystals in water. • A fern-like ZnO nanoleaf is a self-assembly of ZnO nanoplates along one ZnO nanorod. • Fern-like ZnO nanoleaves exhibit enhanced photocatalytic activity than ZnO nanocrystals. • The branched hierarchical structures are responsible for the enhanced photocatalytic activity. - Abstract: Two-dimensional fern-like ZnO nanoleaves were synthesized by ultrasonicating zinc microcrystals in water. The morphology, crystal structure, optical property and photocatalytic activity of the fern-like ZnO nanoleaves were characterized with scanning electron microscopy, X-ray diffraction, transmission electron microscopy, photoluminescence spectroscopy and ultraviolet–visible spectroscopy, respectively. It is found that one fern-like ZnO nanoleaf is composed of one ZnO nanorod as the central trunk and a number of ZnO nanoplates as the side branches in opposite pairs along the central ZnO nanorod. The central ZnO nanorod in the fern-like nanoleaves is about 1 μm long while the side-branching ZnO nanoplates are about 100 nm long and 20 nm wide. Further analysis has revealed that ZnO nanocrystals are the building blocks of the central ZnO nanorod and the side-branching ZnO nanoplates. Under identical conditions, fern-like ZnO nanoleaves exhibit higher photocatalytic activity in photodegrading methyl orange in aqueous solution than spherical ZnO nanocrystals. The first-order photocatalytic rate constant of the fern-like ZnO nanoleaves is about four times as large as that of the ZnO nanoparticles. The branched architecture of the hierarchical nanoleaves is suggested be responsible for the enhanced photocatalytic activity of the fern-like ZnO nanoleaves

  15. Construction of an interatomic potential for zinc oxide surfaces by high-dimensional neural networks

    Energy Technology Data Exchange (ETDEWEB)

    Artrith, Nongnuch; Morawietz, Tobias; Behler, Joerg [Lehrstuhl fuer Theoretische Chemie, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)

    2011-07-01

    Zinc oxide (ZnO) is a technologically important material with many applications, e.g. in heterogeneous catalysis. For theoretical studies of the structural properties of ZnO surfaces, defects, and crystal structures it is necessary to simulate large systems over long time-scales with sufficient accuracy. Often, the required system size is not accessible by computationally rather demanding density-functional theory (DFT) calculations. Recently, artificial Neural Networks (NN) trained to first principles data have shown to provide accurate potential-energy surfaces (PESs) for condensed systems. We present the construction and analysis of a NN PES for ZnO. The structural and energetic properties of bulk ZnO and ZnO surfaces are investigated using this potential and compared to DFT calculations.

  16. Control of N/N2 species ratio in NO plasma for p-type doping of ZnO

    International Nuclear Information System (INIS)

    Chen Xingyou; Zhang Zhenzhong; Jiang Mingming; Wang Shuangpeng; Li Binghui; Shan Chongxin; Liu Lei; Zhao Dongxu; Shen Dezhen; Yao Bin

    2011-01-01

    Nitrogen-doped ZnO thin films were grown on c-plane sapphire (Al 2 O 3 ) substrates via plasma-assisted molecular beam epitaxy using plasma activated nitric oxide (NO) as the oxygen source and dopant. X-ray diffraction measurements indicate that a small NO flux benefits the crystal quality of the thin films. Hall effect measurements indicate that the electron density of the ZnO films decreases gradually with decreasing NO flux, and the conduction reverses to p-type at a certain flux. Optical emission spectra indicate that the N atom content in the NO plasma increases with decreasing NO flux, and the origin of this is discussed. X-ray photoelectron spectroscopy measurements demonstrate that the number of N atom occupied O sites in the ZnO lattice increases correspondingly.

  17. The Mobility Enhancement of Indium Gallium Zinc Oxide Transistors via Low-temperature Crystallization using a Tantalum Catalytic Layer

    OpenAIRE

    Shin, Yeonwoo; Kim, Sang Tae; Kim, Kuntae; Kim, Mi Young; Oh, Saeroonter; Jeong, Jae Kyeong

    2017-01-01

    High-mobility indium gallium zinc oxide (IGZO) thin-film transistors (TFTs) are achieved through low-temperature crystallization enabled via a reaction with a transition metal catalytic layer. For conventional amorphous IGZO TFTs, the active layer crystallizes at thermal annealing temperatures of 600??C or higher, which is not suitable for displays using a glass substrate. The crystallization temperature is reduced when in contact with a Ta layer, where partial crystallization at the IGZO bac...

  18. Spatial atomic layer deposition on flexible porous substrates: ZnO on anodic aluminum oxide films and Al2O3 on Li ion battery electrodes

    International Nuclear Information System (INIS)

    Sharma, Kashish; Routkevitch, Dmitri; Varaksa, Natalia; George, Steven M.

    2016-01-01

    Spatial atomic layer deposition (S-ALD) was examined on flexible porous substrates utilizing a rotating cylinder reactor to perform the S-ALD. S-ALD was first explored on flexible polyethylene terephthalate polymer substrates to obtain S-ALD growth rates on flat surfaces. ZnO ALD with diethylzinc and ozone as the reactants at 50 °C was the model S-ALD system. ZnO S-ALD was then performed on nanoporous flexible anodic aluminum oxide (AAO) films. ZnO S-ALD in porous substrates depends on the pore diameter, pore aspect ratio, and reactant exposure time that define the gas transport. To evaluate these parameters, the Zn coverage profiles in the pores of the AAO films were measured using energy dispersive spectroscopy (EDS). EDS measurements were conducted for different reaction conditions and AAO pore geometries. Substrate speeds and reactant pulse durations were defined by rotating cylinder rates of 10, 100, and 200 revolutions per minute (RPM). AAO pore diameters of 10, 25, 50, and 100 nm were utilized with a pore length of 25 μm. Uniform Zn coverage profiles were obtained at 10 RPM and pore diameters of 100 nm. The Zn coverage was less uniform at higher RPM values and smaller pore diameters. These results indicate that S-ALD into porous substrates is feasible under certain reaction conditions. S-ALD was then performed on porous Li ion battery electrodes to test S-ALD on a technologically important porous substrate. Li 0.20 Mn 0.54 Ni 0.13 Co 0.13 O 2 electrodes on flexible metal foil were coated with Al 2 O 3 using 2–5 Al 2 O 3 ALD cycles. The Al 2 O 3 ALD was performed in the S-ALD reactor at a rotating cylinder rate of 10 RPM using trimethylaluminum and ozone as the reactants at 50 °C. The capacity of the electrodes was then tested versus number of charge–discharge cycles. These measurements revealed that the Al 2 O 3 S-ALD coating on the electrodes enhanced the capacity stability. This S-ALD process could be extended to roll-to-roll operation for

  19. Crystal growth and scintillation properties of multi-component oxide single crystals: Ce:GGAG and Ce:La-GPS

    Energy Technology Data Exchange (ETDEWEB)

    Yoshikawa, A., E-mail: yoshikawa@imr.tohoku.ac.jp [Institute for Materials Research (IMR), Tohoku University, Sendai 980-8577 (Japan); New Industry Creation Hatchery Center (NICHe), Tohoku University, Sendai 980-8579 (Japan); C& A Corporation, 6-6-40 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579 (Japan); Kamada, K. [New Industry Creation Hatchery Center (NICHe), Tohoku University, Sendai 980-8579 (Japan); C& A Corporation, 6-6-40 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579 (Japan); Kurosawa, S. [Institute for Materials Research (IMR), Tohoku University, Sendai 980-8577 (Japan); New Industry Creation Hatchery Center (NICHe), Tohoku University, Sendai 980-8579 (Japan); Shoji, Y. [Institute for Materials Research (IMR), Tohoku University, Sendai 980-8577 (Japan); C& A Corporation, 6-6-40 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579 (Japan); Yokota, Y. [New Industry Creation Hatchery Center (NICHe), Tohoku University, Sendai 980-8579 (Japan); Chani, V.I. [Institute for Materials Research (IMR), Tohoku University, Sendai 980-8577 (Japan); Nikl, M. [Institute of Physics, AS CR, Cukrovarnická 10, 162 53 Prague (Czech Republic)

    2016-01-15

    Crystal growth by micro-pulling-down, Czochralski, and floating zone methods and scintillation properties of Ce:Gd{sub 3}(Ga,Al){sub 5}O{sub 12} (Ce:GGAG) multi-component oxide garnets, and Ce:Gd{sub 2}Si{sub 2}O{sub 7} (Ce:GPS) or Ce:(La,Gd){sub 2}Si{sub 2}O{sub 7} (Ce:La-GPS) pyro-silicates are reviewed. GGAG crystals demonstrated practically linear dependences of some of the parameters including lattice constant, emission wavelength, and band gap on Ga content. However, emission intensity, light yield and energy resolution showed maxima for intermediate compositions. GGAG crystals had the highest light yield of 56,000 photon/MeV for Ga content of 2.7 atoms per garnet formula unit. Similarly the light yield and energy resolution of La-GPS showed the highest values of 40,000 photon/MeV and 4.4%@662 keV, respectively, for La-GPS containing 10% of La. Moreover, La-GPS demonstrated stable scintillation performance up to 200 °C.

  20. Improvement of physical properties of ZnO thin films by tellurium doping

    Energy Technology Data Exchange (ETDEWEB)

    Sönmezoğlu, Savaş, E-mail: svssonmezoglu@kmu.edu.tr; Akman, Erdi

    2014-11-01

    Highlights: • We report the synthesis of tellurium-doped zinc oxide (Te–ZnO) thin films using sol–gel method. • Highly c-axis oriented Te-doped ZnO thin films were grown on FTO glasses as substrate. • 1.5% Te-doping ratio could improve the physical properties of ZnO thin films. - Abstract: This investigation addressed the structural, optical and morphological properties of tellurium incorporated zinc oxide (Te–ZnO) thin films. The obtained results indicated that Te-doped ZnO thin films exhibit an enhancement of band gap energy and crystallinity compared with non-doped films. The optical transmission spectra revealed a shift in the absorption edge toward lower wavelengths. X-ray diffraction measurement demonstrated that the film was crystallized in the hexagonal (wurtzite) phase and presented a preferential orientation along the c-axis. The XRD obtained patterns indicate that the crystallite size of the thin films, ranging from 23.9 to 49.1 nm, changed with the Te doping level. The scanning electron microscopy and atomic force microscopy results demonstrated that the grain size and surface roughness of the thin films increased as the Te concentration increased. Most significantly, we demonstrate that it is possible to control the structural, optical and morphological properties of ZnO thin films with the isoelectronic Te-incorporation level.

  1. Fabrication of thin ZnO films with wide-range tuned optical properties by reactive magnetron sputtering

    Science.gov (United States)

    Davydova, A.; Tselikov, G.; Dilone, D.; Rao, K. V.; Kabashin, A. V.; Belova, L.

    2018-02-01

    We report the manufacturing of thin zinc oxide films by reactive magnetron sputtering at room temperature, and examine their structural and optical properties. We show that the partial oxygen pressure in DC mode can have dramatic effect on absorption and refractive index (RI) of the films in a broad spectral range. In particular, the change of the oxygen pressure from 7% to 5% can lead to either conventional crystalline ZnO films having low absorption and characteristic descending dependence of RI from 2.4-2.7 RIU in the visible to 1.8-2 RIU in the near-infrared (1600 nm) range, or to untypical films, composed of ZnO nano-crystals embedded into amorphous matrix, exhibiting unexpectedly high absorption in the visible-infrared region and ascending dependence of RI with values varying from 1.5 RIU in the visible to 4 RIU in the IR (1600 nm), respectively. Untypical optical characteristics in the second case are explained by defects in ZnO structure arising due to under-oxidation of ZnO crystals. We also show that the observed defect-related film structure remains stable even after annealing of films under relatively high temperatures (30 min under 450 °C). We assume that both types of films can be of importance for photovoltaic (as contact or active layers, respectively), as well as for chemical or biological sensing, optoelectronics etc.

  2. Characterization of Urea Versus hmta in the Preparation of Zinc Oxide NANOSTRUCTURES by Catalytic Immersion Method Grown on Gold-seeded Silicon Substrate

    International Nuclear Information System (INIS)

    Azlinda Abdul Aziz; Khusaimi, Z.; Rusop, M.

    2011-01-01

    Zinc oxide (ZnO) nano structured prepared by immersed method were successfully grown on gold-seeded silicon substrate using Zinc nitrate hexahydrate (Zn(NO 3 ) 2 .6H 2 O) as a precursor was stabilized by a non-toxic urea (CH 4 N 2 O) in a ratio of 1:2 and 1:1 ratio of hexamethylene tetraamine (HMTA). The effect of changing the stabilizer of ZnO solution on the crystal structure, morphology and photoluminescence properties of the resultant ZnO is investigated. X-ray diffraction of the synthesized ZnO shows hexagonal zincite structure. The morphology of the ZnO was characterizing using Field Emission Scanning Electron Microscope (FESEM). The growth of ZnO using urea as stabilizer shows the clusters of ZnO nano flower with serrated broad petals and sharp tips of approximately 25 nm were interestingly formed. ZnO in HMTA showed growth of nano rods. The structures has high surface area, is a potential metal oxide nano structures to be develop for optoelectronic devices and chemical sensors. The formation of ZnO nano structures is found to be significantly affected by the stabilizer. (author)

  3. Thorium/uranium mixed oxide nano-crystals: Synthesis, structural characterization and magnetic properties

    International Nuclear Information System (INIS)

    Hudry, Damien; Griveau, Jean-Christophe; Apostolidis, Christos; Colineau, Eric; Rasmussen, Gert; Walter, Olaf; Wang, Di; Venkata Sai Kiran Chakravadhaluna; Courtois, Eglantine; Kubel, Christian

    2014-01-01

    One of the primary aims of the actinide community within nano-science is to develop a good understanding similar to what is currently the case for stable elements. As a consequence, efficient, reliable and versatile synthesis techniques dedicated to the formation of new actinide-based nano-objects (e.g., nano-crystals) are necessary. Hence, a 'library' dedicated to the preparation of various actinide based nano-scale building blocks is currently being developed. Nano-scale building blocks with tunable sizes, shapes and compositions are of prime importance. So far, the non-aqueous synthesis method in highly coordinating organic media is the only approach which has demonstrated the capability to provide size and shape control of actinide-based nano-crystals (both for thorium and uranium, and recently extended to neptunium and plutonium). In this paper, we demonstrate that the non-aqueous approach is also well adapted to control the chemical composition of the nano-crystals obtained when mixing two different actinides. Indeed, the controlled hot co-injection of thorium acetylacetonate and uranyl acetate (together with additional capping agents) into benzyl ether can be used to synthesize thorium/uranium mixed oxide nano-crystals covering the full compositional spectrum. Additionally, we found that both size and shape are modified as a function of the thorium/uranium ratio. Finally, the magnetic properties of the different thorium/uranium mixed oxide nano-crystals were investigated. Contrary to several reports, we did not observe any ferromagnetic behavior. As a consequence, ferromagnetism cannot be described as a universal feature of nano-crystals of non-magnetic oxides as recently claimed in the literature. (authors)

  4. High temperature oxidation and crystallization behavior of phosphate glass compositions

    International Nuclear Information System (INIS)

    Russo, Diego; Rodriguez, Diego; Grumbaum, N.; Gonzalez Oliver, Carlos

    2003-01-01

    We analyzed the thermal transformation of three iron phosphate glasses having the following nominal compositions: M4 [70% P 2 O 5 , 30% Fe 2 O 3 ], M5 [85% M4, 15% UO 2 ] y M7 [69.7% P 2 O 5 , 28.6% Fe 2 O 3 , 1,7% Al 2 O 3 ]. Thermogravimetric analysis, DTA (differential thermal analysis) and SAXS (Small Angle X-ray Scattering) were performed.It was observed that it is easily possible to produce glasses in these systems having very low crystallinity.We could determine the final stable crystalline phases [Fe 4 (P 2 O 7 ) 3 , Fe(PO 3 ) 3 and Fe 3 (P 2 O 7 ) 2 ].The presence of uranium ions affects not only the redox effects but also the crystallization of the system.SAXS data obtained during the heating in vacuum up to ∼600degC, gave some variation of scattering intensities vs. scattering vector suggesting the development of an extra phase or some kind inhomogeneities that seems to disappear on heating

  5. Preparation of Carbon-Encapsulated ZnO Tetrahedron as an Anode Material for Ultralong Cycle Life Performance Lithium-ion Batteries

    International Nuclear Information System (INIS)

    Ren, Zhimin; Wang, Zhiyu; Chen, Chao; Wang, Jia; Fu, Xinxin; Fan, Chenyao; Qian, Guodong

    2014-01-01

    Highlights: • A novel architecture of 3D carbon framework to encapsulate ZnO nanocrystals was prepared. • The ZnO@C exhibits ultralong cycle life and high specific capacity when was used as anode. • The in situ carbonization leads to a strong connection between the carbon and ZnO. - ABSTRACT: In this paper we report a novel architecture of three-dimension (3D) carbon framework to encapsulate tetrahedron ZnO nanocrystals that serves as an anode material for lithium-ion batteries (LIBs). The ZnO@C composites are prepared via a simple internal-reflux method combined with subsequent calcination in argon. The amorphous carbon is formed on the surface of the ZnO crystals by in situ carbonization of the surfactant, which leads to a strong connection between the carbon framework and the active materials and guarantees faster charge transfer on the electrode. The ZnO crystal calcined at 500°C (ZnO@C-5) possesses regular tetrahedron shape with a side length of 150-200 nm and all of them are uniformly anchored among the network of amorphous carbon. The developed ZnO@C structures not only improve the electronic conductivity of the electrode, but they also offer a larger volume expansion of ZnO during cycling. As a result, the ZnO@C-5 demonstrates a higher reversible capacity, ultralong cycle life and better rate capability than that of the ZnO@C-7 and pure ZnO crystals. After 300 cycles, the ZnO@C-5 demonstrates a high capacity of 518 mAhg −1 at a current density of 110.7 mAg −1 . Moreover, this simple approach prepared the 3D composites architecture could shed light on the design and synthesis of other transition metal oxides for energy storage

  6. Indium-tin oxide surface treatments: Effects on the performance of liquid crystal devices

    International Nuclear Information System (INIS)

    Abderrahmen, A.; Romdhane, F.F.; Ben Ouada, H.; Gharbi, A.

    2006-01-01

    In this work, we investigate the effect of indium tin oxide (ITO) substrate cleaning on the surface properties. Wettability technique was used to measure the contact angle and the surface energy of the different treated ITO substrates. It is found that treatment with the methanol without dehydration gives the lowest water contact angle (most hydrophilic surface) and the highest surface energy compared to other solvents. This result was confirmed by impedance measurements performed on nematic liquid crystal cells with ITO electrodes. Indeed, we check the decrease of ionic entities in the interface ITO/liquid crystal. The polarity and dielectric parameters of the used solvents explain the obtained results

  7. Indium-tin oxide surface treatments: Effects on the performance of liquid crystal devices

    Energy Technology Data Exchange (ETDEWEB)

    Abderrahmen, A. [Laboratoire de physique et chimie des interfaces, Faculte des sciences, 5000, Monastir (Tunisia)]. E-mail: asma_abderrahmen@yahoo.fr; Romdhane, F.F. [Laboratoire de la matiere molle, Faculte des sciences, Tunis (Tunisia); Ben Ouada, H. [Laboratoire de physique et chimie des interfaces, Faculte des sciences, 5000, Monastir (Tunisia); Gharbi, A. [Laboratoire de la matiere molle, Faculte des sciences, Tunis (Tunisia)

    2006-03-15

    In this work, we investigate the effect of indium tin oxide (ITO) substrate cleaning on the surface properties. Wettability technique was used to measure the contact angle and the surface energy of the different treated ITO substrates. It is found that treatment with the methanol without dehydration gives the lowest water contact angle (most hydrophilic surface) and the highest surface energy compared to other solvents. This result was confirmed by impedance measurements performed on nematic liquid crystal cells with ITO electrodes. Indeed, we check the decrease of ionic entities in the interface ITO/liquid crystal. The polarity and dielectric parameters of the used solvents explain the obtained results.

  8. Study on Optoelectronic Characteristics of Sn-Doped ZnO Thin Films on Poly(ethylene terephthalate) and Indium Tin Oxide/Poly(ethylene terephthalate) Flexible Substrates

    Science.gov (United States)

    Cheng, Chi-Hwa; Chen, Mi; Chiou, Chin-Lung; Liu, Xing-Yang; Weng, Lin-Song; Koo, Horng-Show

    2013-05-01

    Transparent conductive oxides of Sn-doped ZnO (SZO) films with doping weight ratios of 2.0, 3.0, 4.0, and 5.0 wt % have been deposited on indium tin oxide (ITO)/poly(ethylene terephthalate) (PET) and PET flexible substrates at room temperature by pulsed laser deposition (PLD). Resultant films of SZO on ITO/PET and PET flexible substrates are amorphous in phase. It is found that undoped and SZO films on ITO/PET is anomalously better than films on PET in optical transmittance in the range of longer wavelength, possibly due to the refraction index difference between SZO, ITO films, and PET substrates, Burstein-Moss effect and optical interference of SZO/ITO bilayer films and substrate materials, and furthermore resulting in the decrement of reflection. The lowest electrical resistivity (ρ) of 4.0 wt % SZO films on flexible substrates of PET and ITO/PET are 3.8×10-2 and ρ= 1.2×10-2 Ω.cm, respectively. It is found that electrical and optical properties of the resultant films are greatly dependent on various amount of Sn element doping effect and substrate material characteristics.

  9. Structural, electrical, and dielectric properties of Cr doped ZnO thin films: Role of Cr concentration

    Energy Technology Data Exchange (ETDEWEB)

    Gürbüz, Osman, E-mail: osgurbuz@yildiz.edu.tr; Okutan, Mustafa

    2016-11-30

    Highlights: • Magnetic material of Cr and semiconductor material of ZnO were grown by the magnetron sputtering co-sputter technique. • Perfect single crystalline structures were grown. • DC and AC conductivity with dielectric properties as a function of frequency (f = 5Hz–13 MHz) at room temperature were measured and compared. • Cr doped ZnO can be used in microwave, sensor and optoelectronic devices as the electrical conductivity increases while dielectric constant decreases with the Cr content. - Abstract: An undoped zinc oxide (ZnO) and different concentrations of chromium (Cr) doped ZnO Cr{sub x}ZnO{sub 1−x} (x = 3.74, 5.67, 8.10, 11.88, and 15.96) thin films were prepared using a magnetron sputtering technique at room temperature. These films were characterized by X-ray diffraction (XRD), High resolution scanning electron microscope (HR-SEM), and Energy dispersive X-ray spectrometry (EDS). XRD patterns of all the films showed that the films possess crystalline structure with preferred orientation along the (100) crystal plane. The average crystallite size obtained was found to be between 95 and 83 nm which was beneficial in high intensity recording peak. Both crystal quality and crystallite sizes decrease with increasing Cr concentration. The crystal and grain sizes of the all film were investigated using SEM analysis. The surface morphology that is grain size changes with increase Cr concentration and small grains coalesce together to form larger grains for the Cr{sub 11.88}ZnO and Cr{sub 15.96}ZnO samples. Impedance spectroscopy studies were carried out in the frequencies ranging from 5 Hz to 13 MHz at room temperature. The undoped ZnO film had the highest dielectric value, while dielectric values of other films decreased as doping concentrations increased. Besides, the dielectric constants decreased whereas the loss tangents increased with increasing Cr content. This was considered to be related to the reduction of grain size as Cr content in ZnO

  10. Morphological transition of ZnO nanostructures influenced by magnesium doping

    International Nuclear Information System (INIS)

    Premkumar, T.; Zhou, Y.S.; Gao, Y.; Baskar, K.; Jiang, L.; Lu, Y.F.

    2012-01-01

    Wurtzite zinc oxide (ZnO) nanochains have been synthesized through high-pressure pulsed laser deposition. The chain-like ZnO nanostructures were obtained from magnesium (Mg) doped ZnO targets, whereas vertically aligned nanorods were obtained from primitive ZnO targets. The Mg doping has influenced the morphological transition of ZnO nanostructures from nanorods to nanochains. The field emission scanning electron microscope images revealed the growth of beaded ZnO nanochains. The ZnO nanochains of different diameters 40 and 120 nm were obtained. The corresponding micro-Raman spectra showed strong E 2H mode of ZnO, which confirmed the good crystallinity of the nanochains. In addition to near band edge emission at 3.28 eV, ZnO nanochains show broad deep level emission at 2.42 eV than that of ZnO nanorods.

  11. The influence of Al2O3, MgO and ZnO on the crystallization characteristics and properties of lithium calcium silicate glasses and glass-ceramics

    International Nuclear Information System (INIS)

    Salman, S.M.; Darwish, H.; Mahdy, E.A.

    2008-01-01

    The crystallization characteristics of glasses based on the Li 2 O-CaO-SiO 2 eutectic (954 ± 4 deg. C) system containing Al 2 O 3 , MgO and ZnO has been investigated by differential thermal analysis (DTA), X-ray diffraction analysis (XRD), and scanning electron microscopy (SEM). The partial replacement of Li 2 O by Al 2 O 3 and CaO by MgO or ZnO in the studied glass-ceramics led to the development of different crystalline phase assemblages, including lithium meta- and di-silicates, lithium calcium silicates, α-quartz, diopside, clinoenstatite, wollastonite, β-eucryptite ss, β-spodumene, α-tridymite, lithium zinc orthosilicate, hardystonite and willemite using various heat-treatment processes. The dilatometric thermal expansion of the glasses and their corresponding glass-ceramics were determined. A wide range of thermal expansion coefficient values were obtained for the investigated glasses and their corresponding crystalline products. The thermal expansion coefficients of the investigated glasses were decreased by Al 2 O 3 , MgO or ZnO additions. The α-values of the investigated glasses were ranged from (+18) to (+108) x 10 -7 K -1 (25-300 deg. C), while those of the glass-ceramics were (+3) to (+135) x 10 -7 K -1 (25-700 deg. C). The chemical durability of the glass-ceramics, towards the attack of 0.1N HCl solution, was markedly improved by Al 2 O 3 with MgO replacements. The composition containing 11.5 mol% Al 2 O 3 and 6.00 mol% MgO exhibited low thermal expansion values and good chemical durability

  12. Doping effect on SILAR synthesized crystalline nanostructured Cu-doped ZnO thin films grown on indium tin oxide (ITO) coated glass substrates and its characterization

    Science.gov (United States)

    Dhaygude, H. D.; Shinde, S. K.; Velhal, Ninad B.; Takale, M. V.; Fulari, V. J.

    2016-08-01

    In the present study, a novel chemical route is used to synthesize the undoped and Cu-doped ZnO thin films in aqueous solution by successive ionic layer adsorption and reaction (SILAR) method. The synthesized thin films are characterized by x-ray diffractometer (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive x-ray analysis (EDAX), contact angle goniometer and UV-Vis spectroscopic techniques. XRD study shows that the prepared films are polycrystalline in nature with hexagonal crystal structure. The change in morphology for different doping is observed in the studies of FE-SEM. EDAX spectrum shows that the thin films consist of zinc, copper and oxygen elements. Contact angle goniometer is used to measure the contact angle between a liquid and a solid interface and after detection, the nature of the films is initiated from hydrophobic to hydrophilic. The optical band gap energy for direct allowed transition ranging between 1.60-2.91 eV is observed.

  13. Growth Stresses in Thermally Grown Oxides on Nickel-Based Single-Crystal Alloys

    Science.gov (United States)

    Rettberg, Luke H.; Laux, Britta; He, Ming Y.; Hovis, David; Heuer, Arthur H.; Pollock, Tresa M.

    2016-03-01

    Growth stresses that develop in α-Al2O3 scale that form during isothermal oxidation of three Ni-based single crystal alloys have been studied to elucidate their role in coating and substrate degradation at elevated temperatures. Piezospectroscopy measurements at room temperature indicate large room temperature compressive stresses in the oxides formed at 1255 K or 1366 K (982 °C or 1093 °C) on the alloys, ranging from a high of 4.8 GPa for René N4 at 1366 K (1093 °C) to a low of 3.8 GPa for René N5 at 1255 K (982 °C). Finite element modeling of each of these systems to account for differences in coefficients of thermal expansion of the oxide and substrate indicates growth strains in the range from 0.21 to 0.44 pct at the oxidation temperature, which is an order of magnitude higher than the growth strains measured in the oxides on intermetallic coatings that are typically applied to these superalloys. The magnitudes of the growth strains do not scale with the parabolic oxidation rate constants measured for the alloys. Significant spatial inhomogeneities in the growth stresses were observed, due to (i) the presence of dendritic segregation and (ii) large carbides in the material that locally disrupts the structure of the oxide scale. The implications of these observations for failure during cyclic oxidation, fatigue cycling, and alloy design are considered.

  14. Positron annihilation spectroscopic study of hydrothermal grown n-type zinc oxide single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Hui, C.W.; Zhang, Z.D.; Zhou, T.J.; Ling, C.C.; Beling, C.D.; Fung, S. [Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong (China); Brauer, G.; Anwand, W.; Skorupa, W. [Institut fuer Ionenstrahlphysik und Materialforschung, Forschungszentrum Rossendorf, Postfach 510119, 01314 Dresden (Germany)

    2007-07-01

    Positron lifetime and coincidence Doppler broadening spectroscopic (CDBS) measurements were carried out to study the defects in two hydrothermal (HT) grown ZnO single crystal samples (HT1 and HT2) obtained from two companies. Single component model could offer good fittings to the room temperature spectra of HT1 and HT2, with the positron lifetimes equal to 199 ps and 181 ps respectively. These two lifetime components were associated with saturated positron trapping into two V{sub Zn}-related defects with different microstructures. The positron lifetimes of HT1 was found to be temperature independent. For the HT2 sample, the positron lifetime remained unchanged with T>200 K and decreased with decreasing temperature as T<200 K. This could be explained by the presence of an additional positron trap having similar electronic environment to that of the delocalized state and competing in trapping positrons with the 181 ps component at low temperatures. Positron-electron autocorrelation function, which was the fingerprint of the annihilation site, was extracted from the CDBS spectrum. The obtained autocorrelation functions of HT1 and HT2 at room temperature, and HT2 at 50 K had features consistent with the above postulates that the 181 ps and the 199 ps components had distinct microstructures and the low temperature positron trap existed in HT2. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. Characterization of Anodic Aluminum Oxide Membrane with Variation of Crystallizing Temperature for pH Sensor.

    Science.gov (United States)

    Yeo, Jin-Ho; Lee, Sung-Gap; Jo, Ye-Won; Jung, Hye-Rin

    2015-11-01

    We fabricated electrolyte-dielectric-metal (EDM) device incorporating a high-k Al2O3 sensing membrane from a porous anodic aluminum oxide (AAO) using a two step anodizing process for pH sensors. In order to change the properties of the AAO template, the crystallizing temperature was varied from 400 degrees C to 700 degrees C over 2 hours. The structural properties were observed by field emission scanning electron microscopy (FE-SEM). The pH sensitivity increased with an increase in the crystallizing temperature from 400 degrees C to 600 degrees C. However at 700 degrees C, deformation occurred. The porous AAO sensor with a crystallizing temperature of 600 degrees C displayed the good sensitivity and long-term stability and the values were 55.7 mV/pH and 0.16 mV/h, respectively.

  16. The crystal structure of tris(thenoyltrifluoroacetonato)bis(triphenylphosphine oxide)neodymium(III)

    International Nuclear Information System (INIS)

    Leipoldt, J.G.; Bok, L.D.C.; Laubscher, A.E.; Basson, S.S.

    1975-01-01

    The crystal structure of tris(thenoyltrifluoroacetonato)bis= x (triphenylphosphine oxide)neodymium(III), (Nd(TTa) 3 .2TPPO), has been determined by single crystal X-ray diffraction. A total number of 5505 independent reflections was used for the structure determination. The complex crystallized in the triclinic space group P 1 - with two molecules in the unit cell. The cell dimensions are a = 23.64 A, b Z= 12.15 A, C 11.19 A, α = 109.4 0 , β = 104.2 0 , γ = 90.8 0 . The final calculated R vale is 8.4%. The molecule is monomeric and the neodymium atom is coordinated to eight oxygen atoms (six from the three thenoyltrifluoroacetone groups and two from the two triphenylphosphine groups) which form a dodecahedron. The average neodymium-oxygen bond length is 2.44 A. (author)

  17. Preparation and properties of crystals of mixed refractory oxides with perovskite structure

    Energy Technology Data Exchange (ETDEWEB)

    Melekh, B T; Andreev, A A; Kartenko, N F; Pevtsov, A B; Trepakov, V A; Filin, Yu N [AN SSSR, Moscow. Fiziko-Tekhnicheskij Inst.

    1982-10-01

    Peculiar features of crystal growth of some complex refractory oxides with perovskite structure using the method of direct high-frequency melting in a cold container are studied. Melting, synthesis and directed crystallization have been conducted in the air. X-ray diffraction investigations of the prepared SrTiO/sub 3/, CaZrO/sub 3/, BaZrO/sub 3/, BaHFO/sub 3/, LaCrO/sub 3/, YCrO/sub 3/, ErCrO/sub 3/, La/sub 2/Ti/sub 2/O/sub 7/, LaTaO/sub 3/ and other oxides are conducted, lattice parameters are given. Optical spectra of absorption, photo- and thermoluminescence and thermostimulated currents are studied.

  18. Ni-Si oxide as an inducing crystallization source for making poly-Si

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Zhiguo; Liu, Zhaojun; Li, Juan; Wu, Chunya; Xiong, Shaozhen [Institute of Photo-electronics, Nankai University, Tianjin (China); Zhao, Shuyun; Wong, Man; Kwok, Hoi Sing [Department of Electronic and Computer Engineering, Hong Kong University of Science and Technology, Kowloon, Hong Kong (China)

    2010-04-15

    Nickel silicon oxide mixture was sputtered on a-Si with Ni-Si alloy target with Ni:Si weight ratio of 1:9 and used as a new inducing source for metal induced lateral crystallization (MILC). The characteristics of the resulted poly-Si materials induced by Ni-Si oxide with different thickness were nearly the same. This means the metal induced crystallization with this new inducing source has wide processing tolerance to make MILC poly-Si. Besides, it reduced the residual Ni content in the resulted poly-Si film. The transfer characteristic curve of poly-Si TFT and a TFT-OLED display demo made with this kind of new inducing source were also presented in this paper. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Selective tuning of high-Q silicon photonic crystal nanocavities via laser-assisted local oxidation.

    Science.gov (United States)

    Chen, Charlton J; Zheng, Jiangjun; Gu, Tingyi; McMillan, James F; Yu, Mingbin; Lo, Guo-Qiang; Kwong, Dim-Lee; Wong, Chee Wei

    2011-06-20

    We examine the cavity resonance tuning of high-Q silicon photonic crystal heterostructures by localized laser-assisted thermal oxidation using a 532 nm continuous wave laser focused to a 2.5 μm radius spot-size. The total shift is consistent with the parabolic rate law. A tuning range of up to 8.7 nm is achieved with ∼ 30 mW laser powers. Over this tuning range, the cavity Qs decreases from 3.2×10(5) to 1.2×10(5). Numerical simulations model the temperature distributions in the silicon photonic crystal membrane and the cavity resonance shift from oxidation.

  20. Surface conductivity of the single crystal aluminum oxide in vacuum and caesium vapors

    International Nuclear Information System (INIS)

    Vasilchenko, A.V.; Izhvanov, O.L.

    1996-01-01

    Results of measurements of surface conductivity of single-crystal aluminum oxide samples in vacuum and cesium vapors at T=620 endash 830 K and P Cs =0.13 endash 2 Pa are shown in the paper. Analysis of caesium vapor influence is carried out and ultimate characteristics of samples conductivity under operation conditions in thermionic nuclear power system (NPP) TFE are estimated. copyright 1996 American Institute of Physics

  1. Growth of cadmium oxide whiskers on cadmium sulphide single crystals with copper as growth activator

    Energy Technology Data Exchange (ETDEWEB)

    Koparanova, N.; Simov, S. (Bylgarska Akademiya na Naukite, Sofia. Inst. po Fizika na Tvyrdoto Tyalo); Genchev, D. (Bylgarska Akademiya na Naukite, Sofia. Inst. za Yadrena Izsledvaniya i Yadrena Energetika); Metchenov, G. (Research Inst. of Criminalistics and Criminology, Sofia (Bulgaria))

    1985-02-01

    Some results on the growth and morphology of cadmium oxide whiskers, obtained on cadmium sulphide single crystals with copper as a growth activator, are presented in this work. Cadmium oxide whiskers have been obtained on brace 112-bar0 brace faces of cadmium sulphide plates with a copper layer deposited in advance. The whiskers grew during the annealing of the plates in a weak stream of technically pure argon at temperatures 670 to 730 deg C for 15 min to 3.5 h. Details about the procedure have been given elsewhere. The composition and morphology of the whiskers have been studied by an X-ray microanalyser JEOL 35 DDS and a scanning electron microscope JEOL, JSM 35. The optical microscopic observations have shown that after annealing, a gray-black granular layer is formed on the cadmium sulphide single crystals and this layer can easily be separated from the crystal substrate. Under the granular layer the crystal is heavily damaged. The whiskers grow on the granular layer and they are coloured yellow-brown or red-brown. The maximum whisker length attains several hundreds of micrometres and in some cases up to 1 mm or more.

  2. Growth of cadmium oxide whiskers on cadmium sulphide single crystals with copper as growth activator

    International Nuclear Information System (INIS)

    Koparanova, N.; Simov, S.

    1985-01-01

    Some results on the growth and morphology of cadmium oxide whiskers, obtained on cadmium sulphide single crystals with copper as a growth activator, are presented in this work. Cadmium oxide whiskers have been obtained on brace 112-bar0 brace faces of cadmium sulphide plates with a copper layer deposited in advance. The whiskers grew during the annealing of the plates in a weak stream of technically pure argon at temperatures 670 to 730 deg C for 15 min to 3.5 h. Details about the procedure have been given elsewhere. The composition and morphology of the whiskers have been studied by an X-ray microanalyser JEOL 35 DDS and a scanning electron microscope JEOL, JSM 35. The optical microscopic observations have shown that after annealing, a gray-black granular layer is formed on the cadmium sulphide single crystals and this layer can easily be separated from the crystal substrate. Under the granular layer the crystal is heavily damaged. The whiskers grow on the granular layer and they are coloured yellow-brown or red-brown. The maximum whisker length attains several hundreds of micrometres and in some cases up to 1 mm or more. (author)

  3. Crystallization and deuterium permeation behaviors of yttrium oxide coating prepared by metal organic decomposition

    Directory of Open Access Journals (Sweden)

    Takumi Chikada

    2016-12-01

    Full Text Available Yttrium oxide coatings were fabricated on reduced activation ferritic/martensitic steels by metal organic decomposition with a dip-coating technique, and their deuterium permeation behaviors were investigated. The microstructure of the coatings varied with heat-treatment temperature: amorphous at 670ºC (amorphous coating and crystallized at 700ºC (crystallized coating. Deuterium permeation flux of the amorphous coating was lower than the uncoated steel by a factor of 5 at 500ºC, while that of the crystallized coating was lower by a factor of around 100 at 400‒550ºC. The permeation fluxes of both coatings were drastically decreased during the measurements at higher temperatures by a factor of up to 790 for the amorphous coating and 1000 for the crystallized one, indicating a microstructure modification occurred by an effect of test temperature with hydrogen flux. Temperature dependence of deuterium diffusivity in the coatings suggests that the decrease of the permeation flux has been derived from a decrease of the diffusivity. Characteristic permeation behaviors were observed with different annealing conditions; however, they can be interpreted using the permeation mechanism clarified in the previous erbium oxide coating studies.

  4. The effect of crystal textures on the anodic oxidization of zirconium in a boiling nitric acid solution

    International Nuclear Information System (INIS)

    Kato, Chiaki; Ishijima, Yasuhiro; Ueno, Fumiyoshi; Yamamoto, Masahiro

    2016-01-01

    The effects of crystal textures and the potentials in the anodic oxidation of zirconium in a boiling nitric acid solution were investigated to study the stress corrosion cracking of zirconium in nitric acid solutions. The test specimen was machined such that the specimen surface was parallel to the rolling surface, arranged with a (0002) crystal texture. The potentials applied for the anodic oxidation of zirconium were set at 1.2, 1.4, and 1.5 V against a saturated KCl–Ag/AgCl electrode (SSE) in boiling 6 M HNO_3. The growth of the zirconium oxide film dramatically changed depending on the applied potential at a closed depassivation potential (1.47 V vs. SSE in this study). At 1.5 V, the zirconium oxide film rapidly grows, and its growth exhibits cyclic oxidation kinetics in accordance with a nearly cubic rate law. The zirconium oxide film grows according to the quantity of electric charge and the growth rate does not depend on the crystal texture in the pretransition region before the cyclic oxidation kinetics. However, the growth and cracking under the thick oxide film depend on the crystal texture in the transition region. On the normal direction side, the oxide film thickness decreases on average since some areas of the thick oxide film are separated from the specimen surface owing to the cracks in the thick oxide. On the rolling direction (RD) side, no cracks in the thick oxide film are observed, but cracks are found under the thick oxide film, which deeply propagate in metal matrix along the RD without an external stress. The cracks under the thick oxide film propagate to the center of the oxide layer. The crystal orientation relationship between the oxide layer and the zirconium matrix is (0002)_Z_r//(111)_Z_r_O_2, and the cracks in the oxide layer propagate in the (0002)_Z_r plane in the zirconium matrix. The oxide layer consists of string-like zirconium oxide and zirconium hydride. The string-like zirconium oxide contains orthorhombic ZrO_2 in addition

  5. Structural, morphological and electroluminescence studies of Zno:Co nanophosphor

    Science.gov (United States)

    Singh, Anju; Vishwakarma, H. L.

    2016-09-01

    The nanoparticles of zinc oxide (ZnO) doped with various concentrations of cobalt (Co) were synthesized by chemical precipitation method in the presence of capping agent polyvinylpyrrolidone (PVP). The effect of doping concentration on structural and morphological properties has been studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). Cell volume, bond length, texture coefficient, lattice constants and dislocation density are also studied. Here, we also compared the interplaner spacing and relative peak intensities from their standard values with different angles. Crystallite sizes have been calculated by Debye-Scherrer's formula whose values are decreasing with increase in cobalt content up to 3 %. It has been seen that the growth orientation of the prepared ZnO nanorods was (101). The XRD analysis also ensures that ZnO has a hexagonal (wurtzite) crystal structure. The electroluminescence (EL) cells were prepared by placing pure and cobalt-doped ZnO nanoparticles between ITO-coated conducting glass plate and aluminium foil. Alternating voltage of various frequencies was applied, and EL brightness at different voltages was measured and corresponding current was also recorded. The voltage dependence of electroluminescence (EL) brightness of the ZnO:Co shows exponential increase. The linear voltage-current characteristic indicates ohmic nature. The EL brightness at a particular voltage is found to increase by increasing Co doping, but for higher percentage of Co the EL brightness is reduced. It is also seen that Co does not influence the threshold voltage. The brightness is also affected by increasing the frequency of AC signal.

  6. Preparation and characterization of ALD deposited ZnO thin films studied for gas sensors

    Energy Technology Data Exchange (ETDEWEB)

    Boyadjiev, S.I., E-mail: boiajiev@gmail.com [MTA-BME Technical Analytical Chemistry Research Group, Szent Gellért tér 4, Budapest, H-1111 (Hungary); Georgi Nadjakov Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Blvd., 1784 Sofia (Bulgaria); Georgieva, V. [Georgi Nadjakov Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Blvd., 1784 Sofia (Bulgaria); Yordanov, R. [Department of Microelectronics, Technical University of Sofia, 8 Kliment Ohridski Blvd., 1756 Sofia (Bulgaria); Raicheva, Z. [Georgi Nadjakov Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Blvd., 1784 Sofia (Bulgaria); Szilágyi, I.M. [MTA-BME Technical Analytical Chemistry Research Group, Szent Gellért tér 4, Budapest, H-1111 (Hungary); Budapest University of Technology and Economics, Department of Inorganic and Analytical Chemistry, Szent Gellért tér 4, Budapest, H-1111 (Hungary)

    2016-11-30

    Highlights: • For the first time the gas sensing towards NO{sub 2} of very thin ALD ZnO films is studied. • The very thin ALD ZnO films showed excellent sensitivity to NO{sub 2} at room temperature. • These very thin film ZnO-based QCM sensors very well register even low concentrations. • The sensors have fully reversible sorption and are able to be recovered in short time. • Described fast and cost-effective ALD deposition of ZnO thin films for QCM gas sensor. - Abstract: Applying atomic layer deposition (ALD), very thin zinc oxide (ZnO) films were deposited on quartz resonators, and their gas sensing properties were studied using the quartz crystal microbalance (QCM) method. The gas sensing of the ZnO films to NO{sub 2} was tested in the concentration interval between 10 and 5000 ppm. On the basis of registered frequency change of the QCM, for each concentration the sorbed mass was calculated. Further characterization of the films was carried out by various techniques, i.e. by SEM-EDS, XRD, ellipsometry, and FTIR spectroscopy. Although being very thin, the films were gas sensitive to NO{sub 2} already at room temperature and could register very well as low concentrations as 100 ppm, while the sorption was fully reversible. Our results for very thin ALD ZnO films show that the described fast, simple and cost-effective technology could be implemented for producing gas sensors working at room temperature and being capable to detect in real time low concentrations of NO{sub 2}.

  7. Photo and radiation induced synthesis of (Ni, Zn)O or mixed NiO–ZnO oxides

    Czech Academy of Sciences Publication Activity Database

    Pavelková, T.; Procházková, L.; Čuba, V.; Múčka, V.; Pospíšil, M.; Jakubec, Ivo

    2015-01-01

    Roč. 304, č. 1 (2015), s. 245-250 ISSN 0236-5731 Institutional support: RVO:61388980 Keywords : Nickel oxide * Solid solution * Zinc oxide * Ionizing radiation * UV radiation * Chemical synthesis Subject RIV: CA - Inorganic Chemistry Impact factor: 0.983, year: 2015

  8. Acceptors in ZnO

    Energy Technology Data Exchange (ETDEWEB)

    McCluskey, Matthew D., E-mail: mattmcc@wsu.edu; Corolewski, Caleb D.; Lv, Jinpeng; Tarun, Marianne C.; Teklemichael, Samuel T. [Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164-2814 (United States); Walter, Eric D. [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States); Norton, M. Grant; Harrison, Kale W. [School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164-2920 (United States); Ha, Su [Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington 99164-6515 (United States)

    2015-03-21

    Zinc oxide (ZnO) has potential for a range of applications in the area of optoelectronics. The quest for p-type ZnO has focused much attention on acceptors. In this paper, Cu, N, and Li acceptor impurities are discussed. Experimental evidence indicates these point defects have acceptor levels 3.2, 1.4, and 0.8 eV above the valence-band maximum, respectively. The levels are deep because the ZnO valence band is quite low compared to conventional, non-oxide semiconductors. Using MoO{sub 2} contacts, the electrical resistivity of ZnO:Li was measured and showed behavior consistent with bulk hole conduction for temperatures above 400 K. A photoluminescence peak in ZnO nanocrystals is attributed to an acceptor, which may involve a Zn vacancy. High field (W-band) electron paramagnetic resonance measurements on the nanocrystals revealed an axial center with g{sub ⊥} = 2.0015 and g{sub //} = 2.0056, along with an isotropic center at g = 2.0035.

  9. The crystal chemistry and structural analysis of uranium oxide hydrates. Final report, May 15, 1995--December 31, 1997

    International Nuclear Information System (INIS)

    Miller, M.L.; Ewing, R.C.

    1998-01-01

    The purpose of this research program was to develop a thorough understanding of the crystal-chemical and crystal-structural systematics of uranyl oxide hydrates which are the initial corrosion products of the UO 2 in spent nuclear fuel and the principal phases in which actinides occur in the near surface environment. The scope of this program has been expanded to include all inorganic phases in which U 6+ plays a significant structural role; currently 183 phases with known crystal structures

  10. Dispersive solid-phase extraction for the determination of trace organochlorine pesticides in apple juices using reduced graphene oxide coated with ZnO nanocomposites as sorbent.

    Science.gov (United States)

    Sun, Ting; Sun, Hefeng; Zhao, Feng

    2017-09-01

    In this work, reduced graphene oxide coated with ZnO nanocomposites was used as an efficient sorbent of dispersive solid-phase extraction and successfully applied for the extraction of organochlorine pesticides from apple juice followed by gas chromatography with mass spectrometry. Several experimental parameters affecting the extraction efficiencies, including the amount of adsorbent, extraction time, and the pH of the sample solution, as well as the type and volume of eluent solvent, were investigated and optimized. Under the optimal experimental conditions, good linearity existed in the range of 1.0-200.0 ng/mL for all the analytes with the correlation coefficients (R 2 ) ranging from 0.9964 to 0.9994. The limits of detection of the method for the compounds were 0.011-0.053 ng/mL. Good reproducibilities were acquired with relative standard deviations below 8.7% for both intraday and interday precision. The recoveries of the method were in the range of 78.1-105.8% with relative standard deviations of 3.3-6.9%. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. The effect of the solution flow rate on the properties of zinc oxide (ZnO) thin films deposited by ultrasonic spray

    International Nuclear Information System (INIS)

    Attaf, A.; Benkhetta, Y.; Saidi, H.; Bouhdjar, A.; Bendjedidi, H.; Nouadji, M.; Lehraki, N.

    2015-01-01

    In this work, we used a system based on ultrasonic spray pyrolysis technique. By witch, we have deposited thin films of zinc oxide (ZnO) with the variation of solution flow rate from 50 ml / h to 150 ml / h, and set other parameters such as the concentration of the solution, the deposition time, substrate temperature and the nozzel -substrate distance. In order to study the influence of the solution flow rate on the properties of the films produced, we have several characterization techniques such as X-ray diffraction to determine the films structure, the scanning electron microscopy SEM for the morphology of the surfaces, EDS spectroscopy for the chemical composition, UV-Visible-Nir spectroscopy for determination the optical proprieties of thin films.The experimental results show that: the films have hexagonal structure at the type (wurtzite), the average size of grains varies from 20.11 to 32.45 nm, the transmittance of the films equals 80% in visible rang and the band gap is varied between 3.274 and 3.282 eV, when the solution flow rate increases from 50 to 150 ml/h

  12. The effect of the solution flow rate on the properties of zinc oxide (ZnO) thin films deposited by ultrasonic spray

    Science.gov (United States)

    Attaf, A.; Benkhetta, Y.; Saidi, H.; Bouhdjar, A.; Bendjedidi, H.; Nouadji, M.; Lehraki, N.

    2015-03-01

    In this work, we used a system based on ultrasonic spray pyrolysis technique. By witch, we have deposited thin films of zinc oxide (ZnO) with the variation of solution flow rate from 50 ml / h to 150 ml / h, and set other parameters such as the concentration of the solution, the deposition time, substrate temperature and the nozzel -substrate distance. In order to study the influence of the solution flow rate on the properties of the films produced, we have several characterization techniques such as X-ray diffraction to determine the films structure, the scanning electron microscopy SEM for the morphology of the surfaces, EDS spectroscopy for the chemical composition, UV-Visible-Nir spectroscopy for determination the optical proprieties of thin films.The experimental results show that: the films have hexagonal structure at the type (wurtzite), the average size of grains varies from 20.11 to 32.45 nm, the transmittance of the films equals 80% in visible rang and the band gap is varied between 3.274 and 3.282 eV, when the solution flow rate increases from 50 to 150 ml/h.

  13. Physiochemical Characterization of Iodine (V Oxide Part II: Morphology and Crystal Structure of Particulate Films

    Directory of Open Access Journals (Sweden)

    Brian K. Little

    2015-11-01

    Full Text Available In this study, the production of particulate films of iodine (V oxides is investigated. The influence that sonication and solvation of suspended particles in various alcohol/ketone/ester solvents have on the physical structure of spin or drop cast films is examined in detail with electron microscopy, powder x-ray diffraction, and UV-visible absorption spectroscopy. Results indicate that sonicating iodine oxides in alcohol mixtures containing trace amounts of water decreases deposited particle sizes and produces a more uniform film morphology. UV-visible spectra of the pre-cast suspensions reveal that for some solvents, the iodine oxide oxidizes the solvent, producing I2 and lowering the pH of the suspension. Characterizing the crystals within the cast films reveal their composition to be primarily HI3O8, their orientations to exhibit a preferential orientation, and their growth to be primarily along the ac-plane of the crystal, enhanced at higher spin rates. Spin-coating at lower spin rates produces laminate-like particulate films versus higher density, one-piece films of stacked particles produced by drop casting. The particle morphology in these films consists of a combination of rods, plates, cubes, and rhombohedra structure.

  14. Formation of ZnO at zinc oxidation by near- and supercritical water under the constant electric field

    Science.gov (United States)

    Shishkin, A. V.; Sokol, M. Ya.; Shatrova, A. V.; Fedyaeva, O. N.; Vostrikov, A. A.

    2014-12-01

    The work has detected an influence of a constant electric field (up to E = 300 kV/m) on the structure of a nanocrystalline layer of zinc oxide, formed on the surface of a planar zinc anode in water under supercritical (673 K and 23 MPa) and near-critical (673 K and 17. 5 MPa) conditions. The effect of an increase of zinc oxidation rate with an increase in E is observed under supercritical conditions and is absent at near-critical ones. Increase in the field strength leads to the formation of a looser structure in the inner part of the zinc oxide layer.

  15. Room temperature ferromagnetism in Cu doped ZnO

    Science.gov (United States)

    Ali, Nasir; Singh, Budhi; Khan, Zaheer Ahmed; Ghosh, Subhasis

    2018-05-01

    We report the room temperature ferromagnetism in 2% Cu doped ZnO films grown by RF magnetron sputtering in different argon and oxygen partial pressure. X-ray photoelectron spectroscopy was used to ascertain the oxidation states of Cu in ZnO. The presence of defects within Cu-doped ZnO films can be revealed by electron paramagnetic resonance. It has been observed that saturated magnetic moment increase as we increase the zinc vacancies during deposition.

  16. Luminescence and spectroscopic investigations on Gd3+ doped ZnO nanophosphor

    Directory of Open Access Journals (Sweden)

    G. Krishna Reddy

    2017-09-01

    Full Text Available The present paper describes the synthesis of 0.1 mol% Gadolinium (Gd doped Zinc oxide (ZnO nanophosphor by solution combustion method using Oxalyl dihydrazide (ODH fuel. Powder X-ray diffraction (PXRD peaks are well matched with the standard hexagonal wurtzite structure of ZnO (JCPDS card no. 36-1451. SEM and TEM analysis reveals porous morphology of as -formed sample with particles having narrow size distribution in the range ∼60–70 nm, in good agreement with XRD data. The PL spectrum of Gd doped ZnO sample exhibits an extra blue emission at 441 nm (∼2.81 eV in addition to the emission bands from undoped ZnO. From the TL data of ZnO:Gd nanophosphor with UV irradiation, it is observed that considerable amount of re-trapping is taking place in all the TL second order peaks. The EPR spectrum exhibits a number of resonance signals suggesting that Gd3+ ions are experiencing different crystal field strength and Zeeman interactions.

  17. Growth and characterization of ZnO thin films prepared by electrodeposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Fahoume, M.; Maghfoul, O.; Aggour, M. [L.P.M.C., Faculte des Sciences, Universite Ibn Tofail, BP. 133-14000 Kenitra (Morocco); Hartiti, B. [L.P.M.A.E.R., Faculte des Sciences et Techniques, B.P. 146 Mohammedia (Morocco); Chraibi, F.; Ennaoui, A. [L.P.M., Faculte des Sciences, Universite Mohammed V, BP.1014 Rabat (Morocco)

    2006-06-15

    ZnO thin films were deposited on either indium tin oxide-coated glass or copper substrate by the electrodeposition process, using zinc chloride and flowing air as precursors. The effect of pH on the structural and morphological ZnO films was studied and the optimum deposition conditions have been outlined. The kinetics of the growth of the films have been investigated. We note that the rate of deposition of ZnO in an acidic solution was larger than in a basic solution. The structure of the films was studied using X-ray diffractometry (XRD) and transmission electron microscopy (TEM). The surface morphology and thickness of the films were determined using scanning electron microscopy. The X-ray diffraction analysis shows that the films are polycrystalline with hexagonal crystal structure (zincite) at pH 4. The optical transmittance of ZnO decreases with varying film thickness. The optical energy bandgap was found to be 3.26eV. (author)

  18. Inactivation of bacterial biofilms using visible-light-activated unmodified ZnO nanorods

    Science.gov (United States)

    Aponiene, Kristina; Serevičius, Tomas; Luksiene, Zivile; Juršėnas, Saulius

    2017-09-01

    Various zinc oxide (ZnO) nanostructures are widely used for photocatalytic antibacterial applications. Since ZnO possesses a wide bandgap, it is believed that only UV light may efficiently assist bacterial inactivation, and diverse crystal lattice modifications should be applied in order to narrow the bandgap for efficient visible-light absorption. In this work we show that even unmodified ZnO nanorods grown by an aqueous chemical growth technique are found to possess intrinsic defects that can be activated by visible light (λ = 405 nm) and successfully applied for total inactivation of various highly resistant bacterial biofilms rather than more sensitive planktonic bacteria. Time-resolved fluorescence analysis has revealed that visible-light excitation creates long-lived charge carriers (τ > 1 μs), which might be crucial for destructive biochemical reactions achieving significant bacterial biofilm inactivation. ZnO nanorods covered with bacterial biofilms of Enterococcus faecalis MSCL 302 after illumination by visible light (λ = 405 nm) were inactivated by 2 log, and Listeria monocytogenes ATCL3C 7644 and Escherichia coli O157:H7 biofilms by 4 log. Heterogenic waste-water microbial biofilms, consisting of a mixed population of mesophilic bacteria after illumination with visible light were also completely destroyed.

  19. Thermal oxidative degradation behaviours of flame-retardant thermotropic liquid crystal copolyester/PET blends

    International Nuclear Information System (INIS)

    Du Xiaohua; Zhao Chengshou; Wang Yuzhong; Zhou Qian; Deng Yi; Qu Minghai; Yang Bing

    2006-01-01

    The flame retardancy and the thermal oxidative degradation behaviors of the blend of poly(ethylene terephthalate) (PET) with a kind of phosphorus-containing thermotropic liquid crystal copolyester (TLCP) with high flame retardancy (limited oxygen index, 70%) have been investigated by oxygen index test (LOI), UL-94 rating and thermogravimetric analysis (TGA) in air. The results show that TLCP can dramatically improve the flame retardancy and the melt dripping behavior of PET. Moreover, the apparent activation energies of thermal oxidative degradation of the blends were evaluated using Kissinger and Flynn-Wall-Ozawa methods. It is found that addition of TLCP improve thermal stability and restrain thermal decomposition of PET in air, especially at the primary degradation stage. Py-GC/MS analysis shows that there are remarkable changes in the pyrolysis products when TLCP are blended into PET. The interaction between TLCP and PET has changed their thermal oxidative degradation mechanism

  20. Photoreactivity of ZnO nanoparticles in visible light: Effect of surface states on electron transfer reaction

    International Nuclear Information System (INIS)

    Baruah, Sunandan; Dutta, Joydeep; Sinha, Sudarson Sekhar; Ghosh, Barnali; Pal, Samir Kumar; Raychaudhuri, A. K.

    2009-01-01

    Wide band gap metal oxide semiconductors such as zinc oxide (ZnO) show visible band photolysis that has been employed, among others, to degrade harmful organic contaminants into harmless mineral acids. Metal oxides show enhanced photocatalytic activity with the increase in electronic defects in the crystallites. By introducing defects into the crystal lattice of ZnO nanoparticles, we observe a redshift in the optical absorption shifting from the ultraviolet region to the visible region (400-700 nm), which is due to the creation of intermediate defect states that inhibit the electron hole recombination process. The defects were introduced by fast nucleation and growth of the nanoparticles by rapid heating using microwave irradiation and subsequent quenching during the precipitation reaction. To elucidate the nature of the photodegradation process, picosecond resolved time correlated single photon count (TCSPC) spectroscopy was carried out to record the electronic transitions resulting from the de-excitation of the electrons to their stable states. Photodegradation and TCSPC studies showed that defect engineered ZnO nanoparticles obtained through fast crystallization during growth lead to a faster initial degradation rate of methylene blue as compared to the conventionally synthesized nanoparticles

  1. Blue-emitting photoluminescence of rod-like and needle-like ZnO nanostructures formed by hot-water treatment of sol–gel derived coatings

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Wai Kian, E-mail: tanwaikian@cie.ignite.tut.ac.jp [Center for International Education, Toyohashi University of Technology, Aichi, Toyohashi 441-8580 (Japan); Kawamura, Go; Muto, Hiroyuki [Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, Aichi, Toyohashi 441-8580 (Japan); Abdul Razak, Khairunisak; Lockman, Zainovia [School of Materials and Mineral Resources, Universiti Sains Malaysia, Engineering Campus, Nibong Tebal, Pulau Pinang 14300 Malaysia (Malaysia); Matsuda, Atsunori, E-mail: matsuda@tut.ee.ac.jp [Center for International Education, Toyohashi University of Technology, Aichi, Toyohashi 441-8580 (Japan); Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, Aichi, Toyohashi 441-8580 (Japan)

    2015-02-15

    The morphological evolution of the zinc oxide (ZnO) nanostructures generated by hot-water treatment (HWT) of sol–gel derived coatings as a function of temperature from 30 to 90 °C was investigated. With increasing HWT temperature, the ZnO crystals evolved from nanoparticles to rod-like and needle-like nanostructures. High-resolution transmission electron microscope observations of rod-like and needle-like nanostructures generated at 60 and 90 °C indicated single crystal ZnO wurtzite structure was obtained. All the hot-water treated samples exhibited blue emission at approximately 440 nm in room temperature. The intensity of blue emission increased with higher HWT temperatures. The unique photoluminescence emission characteristic remained even after heat-treatment at 400 °C for 1 h. As the emission peak obtained in our work is approximately 440 nm (2.82 eV), the emission peak is corresponding to the electron transition from the interstitial Zn to the top of valence band. This facile formation of blue-emitting ZnO nanostructures at low-temperature can be utilized on substrate with low thermal stability for optoelectronic applications such as light emitting devices and biological fluorescence labeling. - Highlights: • Facile and novel formation of ZnO nanostructures by low temperature hot-water treatment. • No catalyst or inhibitor is used. • Evolution of ZnO nanostructures formation as a function of temperature is reported. • Dominant blue emissions are observed from the as-formed and annealed ZnO films. • Ultraviolet and visible emissions are observed for hot-water treated films.

  2. Effect of the substrate surface topology and temperature on the structural properties of ZnO layers obtained by plasma enhanced chemical vapour deposition

    Energy Technology Data Exchange (ETDEWEB)

    Kitova, S; Danev, G, E-mail: skitova@clf.bas.b [Acad. J .Malinowski Central Laboratory of Photoprocesses, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl.109, 1113 Sofia (Bulgaria)

    2010-04-01

    In this work thin ZnO layers were grown by metal-organic PECVD (RF 13.56 MHz) on Si wafers. Zn acetylacetonate was used as a precursor and oxygen as oxidant. A system for dosed injection of the precursor and oxidant into the plasma reactor was developed. The influence of the substrate surface topology and temperature on the structural properties of the deposited layers was studied. ZnO and graphite powder dispersions were used to modify the silicon wafers before starting the deposition process of the layers. Some of the ZnO layers were deposited on the back, unpolished, side of Si wafers. Depositions at 400 {sup 0}C were performed to examine the effect of the substrate temperatures on the layer growth. The film structure was examined by XRD and SEM. The results show that all layers are crystalline with hexagonal wurtzite structure. The crystallites are preferentially oriented along the c-axis direction perpendicular to the substrate surfaces. ZnO layers deposited on thin ZnO seed films and clean Si surface exhibit well-developed grain structures and more c-axis preferred phase with better crystal quality than that of the layers deposited on graphite seed layer or rough, unpolished Si wafer.

  3. The Synthesis and Characterization of Peach-Like ZnO

    International Nuclear Information System (INIS)

    Kamalianfar, A.; Halim, S. A.; Navasery, M.; Din Fasih, Ud; Lim, K. P.; Chen, S. K.; Jahromi, Siamak Pilban; Zahedi, J. A. M.

    2012-01-01

    Peach-like ZnO microstructures are synthesized using vapor phase transport on MgO (001) substrates with a copper oxide (60 nm) buffer layer. The structure and morphology of the product are investigated using an x-ray diffractometer (XRD) and a field-emission scanning electron microscope. The peaches have an average diameter of 3 μm and a wurtzite structure. To study the optical properties, photoluminescence (PL) and Raman spectroscopy are employed. A strong UV emission at 380 nm in the PL spectra is observed, and a sharp and dominant peak at 437 cm −1 in the Raman spectrum can be assigned to the good crystallization of obtained product. In addition, the growth mechanism of the peach-like ZnO structure is tentatively investigated based on the EDX analysis and growth time

  4. Control of N/N{sub 2} species ratio in NO plasma for p-type doping of ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Chen Xingyou [Key Laboratory of Excited State Processes and Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 3888 Dongnanhu Road, Changchun, 130033 (China); Graduate School of the Chinese Academy of Sciences, Beijing 100049 (China); Zhang Zhenzhong; Jiang Mingming; Wang Shuangpeng; Li Binghui; Shan Chongxin; Liu Lei; Zhao Dongxu; Shen Dezhen [Key Laboratory of Excited State Processes and Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 3888 Dongnanhu Road, Changchun, 130033 (China); Yao Bin [State Key Laboratory of Superhard Materials and College of Physics, Jilin University, Changchun 130023 (China)

    2011-09-01

    Nitrogen-doped ZnO thin films were grown on c-plane sapphire (Al{sub 2}O{sub 3}) substrates via plasma-assisted molecular beam epitaxy using plasma activated nitric oxide (NO) as the oxygen source and dopant. X-ray diffraction measurements indicate that a small NO flux benefits the crystal quality of the thin films. Hall effect measurements indicate that the electron density of the ZnO films decreases gradually with decreasing NO flux, and the conduction reverses to p-type at a certain flux. Optical emission spectra indicate that the N atom content in the NO plasma increases with decreasing NO flux, and the origin of this is discussed. X-ray photoelectron spectroscopy measurements demonstrate that the number of N atom occupied O sites in the ZnO lattice increases correspondingly.

  5. Determination of chemical state of Al doping element in ZnO layer

    International Nuclear Information System (INIS)

    Csik, A.; Toth, J.; Lovics, R.; Takats, V.; Hakl, J.; Vad, K.

    2011-01-01

    Complete text of publication follows. Transparent and conducting oxides (TCO) thin films are very important from the scientific and technological point of view. The coexistence of electrical conductivity and optical transparency in these materials makes it possible to use them in modern technologies: transparent electrodes for flat panel displays and photovoltaic cells, low emissivity windows, transparent thin films transistors, light emitting diodes. One of the important TCO semiconductors is the impurity-doped zinc-oxide (ZnO) layer, for example aluminium doped zinc-oxide layer (AZO), due to its unique physical and chemical properties. It has wide band gap (3.44 eV) and large exciton binding energy (60 meV). ZnO thin layers have a great interest for potential applications in optical and optoelectronic devices. Furthermore, high quality single crystal ZnO wafers has already been available as a result of new developments in ZnO growth technologies with the capability to scale up wafer size, which is an important factor for increasing efficiency of solar cells. Nonetheless, in order to enable the use of ZnO layers with enhanced electrical properties, higher conductivities can be obtained by doping with donor elements such as aluminium, gallium, indium, boron or fluorine. Investigation of p-type doping possibilities, diffusion processes and thermal stability of these layers are in the focus of interest in the interpretation of their optical and electrical properties, and the prediction of their lifetime. In our SNMS/SIMS-XPS laboratory, experiments on TCO layered structures were carried on. Depth profile and chemical state analyses of ZnO/AlO/ZnO layered structures were performed by Secondary Neutral Mass Spectrometry (SNMS) and X-ray photoelectron spectroscopy (XPS). The samples were produced by atomic layer deposition technique with the following layered structure: between a few hundred atomic layers of ZnO was an AlO atomic layer. The SNMS was used for depth

  6. Oxygen Barrier Properties and Melt Crystallization Behavior of Poly(ethylene terephthalate/Graphene Oxide Nanocomposites

    Directory of Open Access Journals (Sweden)

    Anna Szymczyk

    2015-01-01

    Full Text Available Poly(ethylene terephthalate nanocomposites with low loading (0.1–0.5 wt% of graphene oxide (GO have been prepared by using in situ polymerization method. TEM study of nanocomposites morphology has shown uniform distribution of highly exfoliated graphene oxide nanoplatelets in PET matrix. Investigations of oxygen permeability of amorphous films of nanocomposites showed that the nanocomposites had better oxygen barrier properties than the neat PET. The improvement of oxygen permeability for PET nanocomposite films over the neat PET is approximately factors of 2–3.3. DSC study on the nonisothermal crystallization behaviors proves that GO acts as a nucleating agent to accelerate the crystallization of PET matrix. The evolution of the lamellar nanostructure of nanocomposite and neat PET was monitored by SAXS during nonisothermal crystallization from the melt. It was found that unfilled PET and nanocomposite with the highest concentration of GO (0.5 wt% showed almost similar values of the long period (L=11.4 nm for neat PET and L=11.5 nm for PET/0.5GO.

  7. Influence of variation in the concentration of ammonium hydroxide on the size of ZnO crystal obtained by Microwave Chemical Bath Deposition

    International Nuclear Information System (INIS)

    Galeazzi, R; Díaz, T; García, G; Rivera, B L; Rosendo, E; López, R; Morales, N; González, C M

    2013-01-01

    Films of good crystalline quality of ZnO were successfully prepared using the microwave chemical bath deposition method at a temperature of 80 °C. Concentration of the basic precursor was varied systematically in order to obtain different degrees of acidity in the precursor solutions. Increasing the pH causes an increase in yield. This increase is reflected on the thickness of the deposit. The results of atomic force microscopy (AFM) show an increase in particle size with increasing pH in agreement with the results obtained by profilometry.

  8. Solid solutions of gadolinium doped zinc oxide nanorods by combined microwave-ultrasonic irradiation assisted crystallization

    Science.gov (United States)

    Kiani, Armin; Dastafkan, Kamran; Obeydavi, Ali; Rahimi, Mohammad

    2017-12-01

    Nanocrystalline solid solutions consisting of un-doped and gadolinium doped zinc oxide nanorods were fabricated by a modified sol-gel process utilizing combined ultrasonic-microwave irradiations. Polyvinylpyrrolidone, diethylene glycol, and triethylenetetramine respectively as capping, structure directing, and complexing agents were used under ultrasound dynamic aging and microwave heating to obtain crystalline nanorods. Crystalline phase monitoring, lattice parameters and variation, morphology and shape, elemental analysis, functional groups, reducibility, and the oxidation state of emerged species were examined by PXRD, FESEM, TEM, EDX, FTIR, micro Raman, H2-TPR, and EPR techniques. Results have verified that irradiation mechanism of gelation and crystallization reduces the reaction time, augments the crystal quality, and formation of hexagonal close pack structure of Wurtzite morphology. Besides, dissolution of gadolinium within host lattice involves lattice deformation, unit cell distortion, and angular position variation. Structure related shape and growth along with compositional purity were observed through microscopic and spectroscopic surveys. Furthermore, TPR and EPR studies elucidated more detailed behavior upon exposure to the exerted irradiations and subsequent air-annealing including the formed oxidation states and electron trapping centers, presence of gadolinium, zinc, and oxygen disarrays and defects, as well as alteration in the host unit cell via gadolinium addition.

  9. Crystal and molecular structure of dichlorodioxobis (triphenylphosphine oxide)uranium(VI)

    Energy Technology Data Exchange (ETDEWEB)

    Bombieri, G; Forsellini, E [Consiglio Nazionale delle Ricerche, Padua (Italy). Lab. di Chimica e Tecnologia dei Radioelementi; Day, J P; Azeez, W I

    1978-01-01

    The crystal structure of (UO/sub 2/Cl/sub 2/(PPh/sub 3/O)/sub 2/) has been determined from three-dimensional X-ray diffraction data. Crystals are triclinic, space group P1, with a = 10.0101(6), b = 10.2589(9), c = 9.2347(8) A, ..cap alpha.. = 110.093(6). ..beta.. = 92.129(6), and ..gamma.. = 78.384(6), and Z = 1. The structure has been solved by the heavy-atom method from counter data, and refined by least squares to a final R of 0.054. The coordination polyhedron around uranium is a distorted octahedron, with a linear uranyl group (U-O 1.764A) perpendicular to a plane in which the two chloride and two oxide ions trans to each other occupy the corners of a rectangle (U-O 2.300; U-Cl 2.645 A).

  10. Crystal orientation dependent thermoelectric properties of highly oriented aluminum-doped zinc oxide thin films

    KAUST Repository

    Abutaha, Anas I.

    2013-02-06

    We demonstrate that the thermoelectric properties of highly oriented Al-doped zinc oxide (AZO) thin films can be improved by controlling their crystal orientation. The crystal orientation of the AZO films was changed by changing the temperature of the laser deposition process on LaAlO3 (100) substrates. The change in surface termination of the LaAlO3 substrate with temperature induces a change in AZO film orientation. The anisotropic nature of electrical conductivity and Seebeck coefficient of the AZO films showed a favored thermoelectric performance in c-axis oriented films. These films gave the highest power factor of 0.26 W m−1 K−1 at 740 K.

  11. Far from the equilibrium crystallization of oxide quantum dots in dried inorganic gels

    Science.gov (United States)

    Costille, B.; Dumoulin, M.; Ntsame Abagha, A. M.; Thune, E.; Guinebretière, R.

    2018-06-01

    We synthesized, through the sol-gel process, far from the equilibrium amorphous materials in which heterogeneous crystallization allowed the formation of oxide quantum dots. The isothermal evolutions of the mean size of the nanocrystals and the crystallinity of the materials were determined through x-ray diffraction experiments. The heterogeneous crystallization is characterized by a kinetic behavior that is far from that expected, according to the classical nucleation theory. We demonstrate that the evolution of the crystallinity is characterized by an Avrami exponent largely smaller than 1. Finally, nanocrystals exhibiting a size significantly below their Bohr radius are obtained and the number of these nanocrystals increases during isothermal treatment, whereas their mean size remains quasi-constant.

  12. Low Temperature Synthesis of Metal Oxides by a Supercritical Seed Enhanced Crystallization (SSEC) Process

    DEFF Research Database (Denmark)

    Jensen, Henrik; Brummerstedt Iversen, Steen; Joensen, Karsten Dan

    2006-01-01

    A novel method for producing crystalline nanosized metal oxides by a Supercritical Seed Enhanced Crystallization (SSEC) Process has been developed. The process is a modified sol-gel process taking place at temperatures as low as 95 ºC with supercritical CO2 as solvent and polypropylene as seeding...... material. The nanocrystalline product is obtained without having to resort to costly post-reaction processing and the product is obtained directly after the SSEC process. TiO2 powders produced by the SSEC process were shown to have a crystallinity of 60 % and a crystal size of 7.3 ± 2.6 nm....... The crystallinity can be controlled by changing the heating rate of the initial formation of the nanoparticles and the morphology can be altered by changing the process time....

  13. crystal

    Science.gov (United States)

    Yu, Yi; Huang, Yisheng; Zhang, Lizhen; Lin, Zhoubin; Sun, Shijia; Wang, Guofu

    2014-07-01

    A Nd3+:Na2La4(WO4)7 crystal with dimensions of ϕ 17 × 30 mm3 was grown by the Czochralski method. The thermal expansion coefficients of Nd3+:Na2La4(WO4)7 crystal are 1.32 × 10-5 K-1 along c-axis and 1.23 × 10-5 K-1 along a-axis, respectively. The spectroscopic characteristics of Nd3+:Na2La4(WO4)7 crystal were investigated. The Judd-Ofelt theory was applied to calculate the spectral parameters. The absorption cross sections at 805 nm are 2.17 × 10-20 cm2 with a full width at half maximum (FWHM) of 15 nm for π-polarization, and 2.29 × 10-20 cm2 with a FWHM of 14 nm for σ-polarization. The emission cross sections are 3.19 × 10-20 cm2 for σ-polarization and 2.67 × 10-20 cm2 for π-polarization at 1,064 nm. The fluorescence quantum efficiency is 67 %. The quasi-cw laser of Nd3+:Na2La4(WO4)7 crystal was performed. The maximum output power is 80 mW. The slope efficiency is 7.12 %. The results suggest Nd3+:Na2La4(WO4)7 crystal as a promising laser crystal fit for laser diode pumping.

  14. Electrochemical and hydrothermal deposition of ZnO on silicon: from continuous films to nanocrystals

    International Nuclear Information System (INIS)

    Balucani, M.; Nenzi, P.; Chubenko, E.; Klyshko, A.; Bondarenko, V.

    2011-01-01

    This article presents the study of the electrochemical deposition of zinc oxide from the non-aqueous solution based on dimethyl sulfoxide and zinc chloride into the porous silicon matrix. The features of the deposition process depending on the thickness of the porous silicon layer are presented. It is shown that after deposition process the porous silicon matrix is filled with zinc oxide nanocrystals with a diameter of 10–50 nm. The electrochemically deposited zinc oxide layers on top of porous silicon are shown to have a crystalline structure. It is also shown that zinc oxide crystals formed by hydrothermal method on the surface of electrochemically deposited zinc oxide film demonstrate ultra-violet luminescence. The effect of the porous silicon layer thickness on the morphology of the zinc oxide is shown. The structures obtained demonstrated two luminescence bands peaking at the 375 and 600 nm wavelengths. Possible applications of ZnO nanostructures, porous and continuous polycrystalline ZnO films such as gas sensors, light-emitting diodes, photovoltaic devices, and nanopiezo energy generators are considered. Aspects of integration with conventional silicon technology are also discussed.

  15. Ultrasonic-assisted fabrication of superhydrophobic ZnO nanowall ...

    Indian Academy of Sciences (India)

    The results suggested that the synergistic effect of the aluminium oxide seed layer and sonochemical process can enable the formation of ZnO nanowall structures favourable for superhydrophobic property. A possible growth mechanism of ZnO nanowalls formation during sonication process has been discussed in detail.

  16. Synthesis from zinc oxalate, growth mechanism and optical properties of ZnO nano/micro structures

    Energy Technology Data Exchange (ETDEWEB)

    Raj, C. Justin; Varma, K.B.R. [Materials Research Centre, Indian Institute of Science, Bangalore 560 012 (India); Joshi, R.K. [Special Center for Nano Sciences, Jawaharlal Nehru University, New Delhi 110067 (India)

    2011-11-15

    We report the synthesis of various morphological micro to nano structured zinc oxide crystals via simple precipitation technique. The growth mechanisms of the zinc oxide nanostructures such as snowflake, rose, platelets, porous pyramid and rectangular shapes were studied in detail under various growth conditions. The precursor powders were prepared using several zinc counter ions such as chloride, nitrate and sulphate along with oxalic acid as a precipitating agent. The precursors were decomposed by heating in air resulting in the formation of different shapes of zinc oxide crystals. Variations in ZnO nanostructural shapes were possibly due to the counter ion effect. Sulphate counter ion led to unusual rose-shape morphology. Strong ultrasonic treatment on ZnO rose shows that it was formed by irregular arrangement of micro to nano size hexagonal zinc oxide platelets. The X-ray diffraction studies confirmed the wurzite structure of all zinc oxide samples synthesized using different zinc counter ions. Functional groups of the zinc oxalate precursor and zinc oxide were identified using micro Raman studies. The blue light emission spectra of the various morphologies were recorded using luminescence spectrometer. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Crystallization of oxidized, moderately hydrous arc basalt at mid-to-lower crustal pressures

    Science.gov (United States)

    Blatter, D. L.; Sisson, T. W.; Hankins, W. B.

    2012-12-01

    Decades of experimental work show that dry, reduced, subalkaline basalts differentiate to produce tholeiitic (high Fe/Mg) daughter liquids, however the influences of H2O and oxidation on differentiation paths are not well established. Accordingly, we performed crystallization experiments on a relatively magnesian basalt (8.7 wt% MgO) typical of mafic lavas erupted in the Cascades magmatic arc near Mount Rainier, Washington. Starting material was synthesized with 3 wt% H2O and run in 2.54 cm piston-cylinder vessels at 900, 700, and 400 MPa and 1200 to 925 degrees C. Samples were contained in Au75Pd25 capsules pre-saturated with Fe by reaction with magnetite at controlled fO2. Oxygen fugacity was controlled during high-pressure syntheses by the double capsule method using Re-ReO2 plus H2O-CO2 vapor in the outer capsule, mixed to match the expected fH2O of the vapor-undersaturated sample. Crystallization was similar at all pressures with a high temperature interval consisting of augite + olivine + orthopyroxene + Cr-spinel (in decreasing abundance). With decreasing temperature, plagioclase crystallizes, FeTi-oxides replace spinel, olivine dissolves, and finally amphibole appears. Liquids at 900 MPa track along Miyashiro's (1974) tholeiitic vs. calc-alkaline boundary, whereas those at 700 and 400 MPa become calc-alkaline by ~57 wt% SiO2 and greater. Although these evolved liquids are similar in most respects to common calc-alkaline andesites, they differ in having low-CaO due to early and abundant crystallization of augite prior to plagioclase, with the result that they become peraluminous (ASI: Al/(Na+K+Ca)>1) by ~55 wt% SiO2, similar to liquids reported in other studies of the high-pressure crystallization of hydrous basalts (Müntener and Ulmer, 2006 and references therein). A compilation of >7000 analyses of volcanic and intrusive rocks from the Cascades and the Sierra Nevada batholith shows that ASI in arc magmas increases continuously and linearly with SiO2 from

  18. Polycaprolactone-templated reduced-graphene oxide liquid crystal nanofibers towards biomedical applications

    DEFF Research Database (Denmark)

    Jalili-Firoozinezhad, Sasan; Hasan Mohamadzadeh Moghadam, Mohamad; Ghanian, Mohammad Hossein

    2017-01-01

    Here, we report a facile method to generate electrically conductive nanofibers by coating and subsequently chemically reducing graphene oxide (GO) liquid crystals on a polycaprolactone (PCL) mat. Ultra large GO sheets obtained are in favor of charge carrier mobility and oriented morphology...... of the GO coating. We showed that coating the reduced GO (rGO) not only retains the three-dimensional topography, fiber orientation and size of the template PCL, but also makes it electroconductive. Our preliminary in vitro assessments using mesenchymal stem cells revealed no induced cytotoxicity yet...... increased cellular metabolism on PCL-templated rGO fibers....

  19. Single Crystal Growth of Pure Co3+ Oxidation State Material LaSrCoO4

    Directory of Open Access Journals (Sweden)

    Hanjie Guo

    2016-08-01

    Full Text Available We report on the single crystal growth of the single-layer perovskite cobaltate LaSrCoO4 that was grown by the optical floating zone method using high oxygen pressures. Phase purity and single crystallinity were confirmed by X-ray diffraction techniques. The pure Co3+ oxidation state was confirmed by X-ray absorbtion spectroscopy measurements. A transition to a spin glass state is observed at ∼7 K in magnetic susceptibility and specific heat measurements.

  20. Photoelectrocatrocatalytic hydrolysis of starch by using sprayed ZnO thin films

    Science.gov (United States)

    Sapkal, R. T.; Shinde, S. S.; Rajpure, K. Y.; Bhosale, C. H.

    2013-05-01

    Thin films of zinc oxide have been deposited onto glass/FTO substrates at optimized 400 °C by using a chemical spray pyrolysis technique. Deposited films are character photocatalytic activity by using XRD, an SEM, a UV-vis spectrophotometer, and a PEC single-cell reactor. Films are polycrystalline and have a hexagonal (wurtzite) crystal structure with c-axis (002) orientation growth perpendicular to the substrate surface. The observed direct band gap is about 3.22 eV for typical films prepared at 400 °C. The photocatalytic activity of starch with a ZnO photocatalyst has been studied by using a novel photoelectrocatalytic process.

  1. Inductive crystal field control in layered metal oxides with correlated electrons

    International Nuclear Information System (INIS)

    Balachandran, P. V.; Cammarata, A.; Rondinelli, J. M.; Nelson-Cheeseman, B. B.; Bhattacharya, A.

    2014-01-01

    We show that the NiO 6 crystal field energies can be tailored indirectly via heterovalent A cation ordering in layered (La,A)NiO 4 Ruddlesden–Popper (RP) oxides, where A = Sr, Ca, or Ba, using density functional calculations. We leverage as a driving force the electrostatic interactions between charged [LaO] 1+ and neutral [AO] 0 planes to inductively tune the Ni–O bond distortions, without intentional doping or epitaxial strain, altering the correlated d-orbital energies. We use this strategy to design cation ordered LaCaNiO 4 and LaBaNiO 4 with distortions favoring enhanced Ni e g orbital polarization, and find local electronic structure signatures analogous to those in RP La-cuprates, i.e., parent phases of the high-temperature superconducting oxides

  2. Inductive crystal field control in layered metal oxides with correlated electrons

    Energy Technology Data Exchange (ETDEWEB)

    Balachandran, P. V.; Cammarata, A.; Rondinelli, J. M., E-mail: jrondinelli@nortwestern.edu [Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104 (United States); Nelson-Cheeseman, B. B. [School of Engineering, University of St. Thomas, St. Paul, Minnesota 55105 (United States); Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Bhattacharya, A. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

    2014-07-01

    We show that the NiO{sub 6} crystal field energies can be tailored indirectly via heterovalent A cation ordering in layered (La,A)NiO{sub 4} Ruddlesden–Popper (RP) oxides, where A = Sr, Ca, or Ba, using density functional calculations. We leverage as a driving force the electrostatic interactions between charged [LaO]{sup 1+} and neutral [AO]{sup 0} planes to inductively tune the Ni–O bond distortions, without intentional doping or epitaxial strain, altering the correlated d-orbital energies. We use this strategy to design cation ordered LaCaNiO{sub 4} and LaBaNiO{sub 4} with distortions favoring enhanced Ni e{sub g} orbital polarization, and find local electronic structure signatures analogous to those in RP La-cuprates, i.e., parent phases of the high-temperature superconducting oxides.

  3. Crystallization of the NADH-oxidizing domain of the Na+-translocating NADH:ubiquinone oxidoreductase from Vibrio cholerae

    International Nuclear Information System (INIS)

    Tao, Minli; Türk, Karin; Diez, Joachim; Grütter, Markus G.; Fritz, Günter; Steuber, Julia

    2006-01-01

    The FAD domain of the NqrF subunit from the Na + -translocating NADH dehydrogenase from V. cholerae has been purified and crystallized. A complete data set was recorded at 3.1 Å. The Na + -translocating NADH:quinone oxidoreductase (Na + -NQR) from pathogenic and marine bacteria is a respiratory complex that couples the exergonic oxidation of NADH by quinone to the transport of Na + across the membrane. The NqrF subunit oxidizes NADH and transfers the electrons to other redox cofactors in the enzyme. The FAD-containing domain of NqrF has been expressed, purified and crystallized. The purified NqrF FAD domain exhibited high rates of NADH oxidation and contained stoichiometric amounts of the FAD cofactor. Initial crystallization of the flavin domain was achieved by the sitting-drop technique using a Cartesian MicroSys4000 robot. Optimization of the crystallization conditions yielded yellow hexagonal crystals with dimensions of 30 × 30 × 70 µm. The protein mainly crystallizes in long hexagonal needles with a diameter of up to 30 µm. Crystals diffract to 2.8 Å and belong to space group P622, with unit-cell parameters a = b = 145.3, c = 90.2 Å, α = β = 90, γ = 120°

  4. Microwave synthesis and photocatalytic activities of ZnO bipods with different aspect ratios

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Fazhe; Zhao, Zengdian [Analysis and Testing Center, Shandong University of Technology, Zibo 255100 (China); Qiao, Xueliang, E-mail: xuelqiao@163.com [State Key Laboratory of Plastic Forming Simulation and Die and Mould Technology, Huazhong University of Science and Technology, Wuhan 430074, Hubei (China); Tan, Fatang; Wang, Wei [State Key Laboratory of Plastic Forming Simulation and Die and Mould Technology, Huazhong University of Science and Technology, Wuhan 430074, Hubei (China)

    2016-02-15

    Highlights: • We synthesized linked ZnO nanorods by a facile microwave method. • The effect of reaction parameters on ZnO was investigated. • ZnO bipods with different aspect ratios were prepared. • The photocatalytic performance of ZnO bipods was evaluated. - Abstract: Linked ZnO nanorods have been successfully prepared via a facile microwave method without any post-synthesis treatment. The X-ray diffraction (XRD) patterns indicated the precursor had completely transformed into the pure ZnO crystal. The images of field emitting scanning electron microscope (FESEM) and transmission electron microscope (TEM) showed that linked ZnO nanorods consisted predominantly of ZnO bipods. The formation process of the ZnO bipods was clearly discussed. ZnO bipods with different aspect ratios have been obtained by tuning the concentrations of reagents and microwave power. Moreover, the photocatalytic performance of ZnO bipods with different aspect ratios for degradation of methylene blue was systematically evaluated. The results of photocatalytic experiments showed that the photocatalytic activity increased with the aspect ratios of ZnO bipods increased. The reason is that ZnO bipods with larger aspect ratio have higher surface area, which can absorb more MB molecules to react with ·OH radicals.

  5. Correlation of electrolyte-derived inclusions to crystallization in the early stage of anodic oxide film growth on titanium

    Energy Technology Data Exchange (ETDEWEB)

    Jaeggi, C., E-mail: christian.jaeggi@empa.ch [Empa, Swiss Federal Laboratories for Materials Testing and Research, Advanced Materials Processing Laboratory, Feuerwerkerstrasse 39, CH-3602 Thun (Switzerland); Parlinska-Wojtan, M., E-mail: magdalena.parlinska@empa.ch [Empa, Swiss Federal Laboratories for Materials Testing and Research, Center for Electron Microscopy, Ueberlandstrasse 129, CH-8600 Duebendorf (Switzerland); Kern, P., E-mail: Philippe.Kern@neopac.ch [Empa, Swiss Federal Laboratories for Materials Testing and Research, Laboratory for Mechanics of Materials and Nanostructures, Feuerwerkerstrasse 39, CH-3602 Thun (Switzerland)

    2012-01-01

    Pure titanium has been subjected to anodization in sulfuric and phosphoric acid. For a better understanding of the oxide growth and properties of the final film, with a particular interest focused on the solution anions in the early stage of crystallization, microstructural analyses (Raman, Transmission Electron Microscopy [TEM]) of the oxide films were correlated to chemical depth profiling by glow discharge optical emission spectroscopy (GDOES). Raman spectroscopy shows that crystallization of the oxide films starts at potentials as low as 10-20 V. The onset of crystallization and the ongoing increase in crystallinity with increasing anodization potentials had already earlier been correlated to ac-impedance measurements [Jaeggi et al., Surf. Interface Anal. 38 (2006) 182]. TEM observations show a clear difference in the early phase of crystallization between oxides grown in 1 M sulfuric acid compared to 1 M phosphoric acid. Moreover, independent of electrolyte type, nano-sized pores from oxygen bubbles formation were revealed in the central part of the films. Until now, oxygen bubbles inside an anodically grown oxide have not been observed before without the presence of crystalline regions nearby. A growth model is proposed, in which the different starting locations of crystallization inside the films are correlated to the presence of the acid anions as residues in the film, as found by GDOES chemical depth-profiling.

  6. Hydrothermal Growth of Vertically Aligned ZnO Nanorods Using a Biocomposite Seed Layer of ZnO Nanoparticles.

    Science.gov (United States)

    Ibupoto, Zafar Hussain; Khun, Kimleang; Eriksson, Martin; AlSalhi, Mohammad; Atif, Muhammad; Ansari, Anees; Willander, Magnus

    2013-08-19

    Well aligned ZnO nanorods have been prepared by a low temperature aqueous chemical growth method, using a biocomposite seed layer of ZnO nanoparticles prepared in starch and cellulose bio polymers. The effect of different concentrations of biocomposite seed layer on the alignment of ZnO nanorods has been investigated. ZnO nanorods grown on a gold-coated glass substrate have been characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques. These techniques have shown that the ZnO nanorods are well aligned and perpendicular to the substrate, and grown with a high density and uniformity on the substrate. Moreover, ZnO nanorods can be grown with an orientation along the c -axis of the substrate and exhibit a wurtzite crystal structure with a dominant (002) peak in an XRD spectrum and possessed a high crystal quality. A photoluminescence (PL) spectroscopy study of the ZnO nanorods has revealed a conventional near band edge ultraviolet emission, along with emission in the visible part of the electromagnetic spectrum due to defect emission. This study provides an alternative method for the fabrication of well aligned ZnO nanorods. This method can be helpful in improving the performance of devices where alignment plays a significant role.

  7. Hydrothermal Growth of Vertically Aligned ZnO Nanorods Using a Biocomposite Seed Layer of ZnO Nanoparticles

    Directory of Open Access Journals (Sweden)

    Zafar Hussain Ibupoto

    2013-08-01

    Full Text Available Well aligned ZnO nanorods have been prepared by a low temperature aqueous chemical growth method, using a biocomposite seed layer of ZnO nanoparticles prepared in starch and cellulose bio polymers. The effect of different concentrations of biocomposite seed layer on the alignment of ZnO nanorods has been investigated. ZnO nanorods grown on a gold-coated glass substrate have been characterized by X-ray diffraction (XRD and field emission scanning electron microscopy (FESEM techniques. These techniques have shown that the ZnO nanorods are well aligned and perpendicular to the substrate, and grown with a high density and uniformity on the substrate. Moreover, ZnO nanorods can be grown with an orientation along the c-axis of the substrate and exhibit a wurtzite crystal structure with a dominant (002 peak in an XRD spectrum and possessed a high crystal quality. A photoluminescence (PL spectroscopy study of the ZnO nanorods has revealed a conventional near band edge ultraviolet emission, along with emission in the visible part of the electromagnetic spectrum due to defect emission. This study provides an alternative method for the fabrication of well aligned ZnO nanorods. This method can be helpful in improving the performance of devices where alignment plays a significant role.

  8. Surface functionalization of carbon nanofibers by sol-gel coating of zinc oxide

    Energy Technology Data Exchange (ETDEWEB)

    Shao Dongfeng [Key Laboratory of Eco-textiles, Ministry of Education, Jiangnan University, Wuxi 214122 (China); Changzhou Textile Garment Institute, Changzhou 213164 (China); Wei Qufu [Key Laboratory of Eco-textiles, Ministry of Education, Jiangnan University, Wuxi 214122 (China)], E-mail: qfwei@jiangnan.edu.cn; Zhang Liwei; Cai Yibing; Jiang Shudong [Key Laboratory of Eco-textiles, Ministry of Education, Jiangnan University, Wuxi 214122 (China)

    2008-08-15

    In this paper the functional carbon nanofibers were prepared by the carbonization of ZnO coated PAN nanofibers to expand the potential applications of carbon nanofibers. Polyacrylonitrile (PAN) nanofibers were obtained by electrospinning. The electrospun PAN nanofibers were then used as substrates for depositing the functional layer of zinc oxide (ZnO) on the PAN nanofiber surfaces by sol-gel technique. The effects of coating, pre-oxidation and carbonization on the surface morphology and structures of the nanofibers were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Scanning electron microscopy (SEM), respectively. The results of SEM showed a significant increase of the size of ZnO nanograins on the surface of nanofibers after the treatments of coating, pre-oxidation and carbonization. The observations by SEM also revealed that ZnO nanoclusters were firmly and clearly distributed on the surface of the carbon nanofibers. FTIR examination also confirmed the deposition of ZnO on the surface of carbon nanofibers. The XRD analysis indicated that the crystal structure of ZnO nanograins on the surface of carbon nanofibers.

  9. Experimental and numerical optical characterization of plasmonic copper nanoparticles embedded in ZnO fabricated by ion implantation and annealing

    Energy Technology Data Exchange (ETDEWEB)

    Le, Khai Q. [Faculty of Science and Technology, Hoa Sen University, Ho Chi Minh City (Viet Nam); Department of Physics, Faculty of Science, Jazan University, P.O. Box 114, 45142 Jazan (Saudi Arabia); Nguyen, Hieu P.T. [Department of Electrical and Computer Engineering, New Jersey Institute of Technology, NJ 07102 (United States); Ngo, Quang Minh [Institute of Material Sciences, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay, Hanoi (Viet Nam); Canimoglu, Adil [Nigde University, Faculty of Arts and Sciences, Physics Department, Nigde (Turkey); Can, Nurdogan, E-mail: cannurdogan@yahoo.com [Celal Bayar University, Faculty of Arts and Sciences, Department of Physics, Muradiye, Manisa (Turkey); Department of Physics, Faculty of Science, Jazan University, P.O. Box 114, 45142 Jazan (Saudi Arabia)

    2016-06-05

    Here we describe the successfully fabrication of metal nanoparticle crystals by implanting copper (Cu) ions into single zinc oxide (ZnO) crystals with ion energy of 400 keV at ion doses of 1 × 10{sup 16} to 1 × 10{sup 17} ions/cm{sup 2}. After implantation and post-annealing treatment, the Cu implanted ZnO produces a broad range of luminescence emissions, ranging from green to yellow. A green luminescence peak at 550 nm could be ascribed to the isolated Cu ions. The changes in luminescence emission bands between the initial implant and annealed suggest that the implants give rise to clustering Cu nanoparticles in the host matrix but that the annealing process dissociates these. Numerical modelling of the Cu nanoparticles was employed to simulate their optical properties including the extinction cross section, electron energy loss spectroscopy and cathodoluminescence. We demonstrate that the clustering of nanoparticles generates Fano resonances corresponding to the generation of multiple resonances, while the isolation of nanoparticles results in intensity amplification. - Highlights: • We present the fabrication of metal nanoparticle crystals by implanting Cu into ZnO. • The luminescence properties were studied at different annealing temperature. • Numerical modelling of the Cu nanoparticles was employed. • We demonstrate that the clustering of nanoparticles generates Fano resonances.

  10. Pressure effect on ionic conductivity in yttrium-oxide-doped single-crystal zirconium oxide

    International Nuclear Information System (INIS)

    Park, E.T.; Park, J.H.

    1998-06-01

    In this study, the authors investigated the effect of pressure on the ionic conductivity of a 9.5 mol% yttria-stabilized zirconia (YSZ) single crystal. The experiment was conducted in the elastic region, and the oxygen ion transport number was unity (t ion > 0.99999). A conventional four-probe DC method was used to measure the ionic conductivity of the rectangular-shaped sample under uniaxial pressures up to 600 atm at 750 C in air. Measured ionic conductivity decreased as applied pressure increased. Based on henry Eyring's absolute reaction rate theory, which states that the calculated activation volume has a positive value (ΔV 2 = 2.08 cm 3 /mol of O -2 ) for oxygen ion transport in the fluoride cubic lattice, they concluded that the results they obtained could be explained by an oxygen ion transport mechanism. This mechanism can explain the fact that the interionic distance increases during oxygen ion transport from one unit cell to neighboring unit cells

  11. Clustered atom-replaced structure in single-crystal-like metal oxide

    Science.gov (United States)

    Araki, Takeshi; Hayashi, Mariko; Ishii, Hirotaka; Yokoe, Daisaku; Yoshida, Ryuji; Kato, Takeharu; Nishijima, Gen; Matsumoto, Akiyoshi

    2018-06-01

    By means of metal organic deposition using trifluoroacetates (TFA-MOD), we replaced and localized two or more atoms in a single-crystalline structure having almost perfect orientation. Thus, we created a new functional structure, namely, clustered atom-replaced structure (CARS), having single-crystal-like metal oxide. We replaced metals in the oxide with Sm and Lu and localized them. Energy dispersive x-ray spectroscopy results, where the Sm signal increases with the Lu signal in the single-crystalline structure, confirm evidence of CARS. We also form other CARS with three additional metals, including Pr. The valence number of Pr might change from 3+ to approximately 4+, thereby reducing the Pr–Ba distance. We directly observed the structure by a high-angle annular dark-field image, which provided further evidence of CARS. The key to establishing CARS is an equilibrium chemical reaction and a combination of additional larger and smaller unit cells to matrix cells. We made a new functional metal oxide with CARS and expect to realize CARS in other metal oxide structures in the future by using the above-mentioned process.

  12. Crystal Structural Effect of AuCu Alloy Nanoparticles on Catalytic CO Oxidation

    International Nuclear Information System (INIS)

    Zhan, Wangcheng; Wang, Jinglin; Wang, Haifeng; Zhang, Jinshui; Liu, Xiaofei

    2017-01-01

    Controlling the physical and chemical properties of alloy nanoparticles (NPs) is an important approach to optimize NP catalysis. Unlike other tuning knobs, such as size, shape, and composition, crystal structure has received limited attention and not been well understood for its role in catalysis. This deficiency is mainly due to the difficulty in synthesis and fine-tuning of the NPs’ crystal structure. Here, Exemplifying by AuCu alloy NPs with face centered cubic (fcc) and face centered tetragonal (fct) structure, we demonstrate a remarkable difference in phase segregation and catalytic performance depending on the crystal structure. During the thermal treatment in air, the Cu component in fcc-AuCu alloy NPs segregates more easily onto the alloy surface as compared to that in fct-AuCu alloy NPs. As a result, after annealing at 250 °C in air for 1 h, the fcc- and fct-AuCu alloy NPs are phase transferred into Au/CuO and AuCu/CuO core/shell structures, respectively. More importantly, this variation in heterostructures introduces a significant difference in CO adsorption on two catalysts, leading to a largely enhanced catalytic activity of AuCu/CuO NP catalyst for CO oxidation. Furthermore, the same concept can be extended to other alloy NPs, making it possible to fine-tune NP catalysis for many different chemical reactions.

  13. Crystallization and unusual rheological behavior in poly(ethylene oxide)–clay nanocomposites

    KAUST Repository

    Kelarakis, Antonios

    2011-05-01

    We report a systematic study of the crystallization and rheological behavior of poly(ethylene oxide) (PEO)-clay nanocomposites. To that end a series of nanocomposites based on PEOs of different molecular weight (103 < MW < 105 g/mol) and clay surface modifier was synthesized and characterized. Incorporation of organoclays with polar (MMT-OH) or aromatic groups (MMT-Ar) suppresses the crystallization of polymer chains in low MW PEO, but does not significantly affect the crystallization of high MW matrices. In addition, the relative complex viscosity of the nanocomposites based on low MW PEO increases significantly, but the effect is less pronounced at higher MWs. The viscosity increases in the series MMT-Alk < MMT-OH < MMT-Ar. In contrast to the neat PEO which exhibits a monotonic decrease of viscosity with temperature, all nanocomposites show an increase after a certain temperature. This is the first report of such dramatic enhancements in the viscoelasticity of nanocomposites, which are reversible, are based on a simple polymer matrix and are true in a wide temperature range. © 2011 Elsevier Ltd. All rights reserved.

  14. Crystal Structural Effect of AuCu Alloy Nanoparticles on Catalytic CO Oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Zhan, Wangcheng [East China Univ. of Science and Technology, Shanghai (China); Wang, Jinglin [East China Univ. of Science and Technology, Shanghai (China); Wang, Haifeng [East China Univ. of Science and Technology, Shanghai (China); Zhang, Jinshui [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Liu, Xiaofei [East China Univ. of Science and Technology, Shanghai (China); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Zhang, Pengfei [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Chi, Miaofang [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Guo, Yanglong [East China Univ. of Science and Technology, Shanghai (China); Guo, Yun [East China Univ. of Science and Technology, Shanghai (China); Lu, Guanzhong [East China Univ. of Science and Technology, Shanghai (China); Sun, Shouheng [Brown Univ., Providence, RI (United States); Dai, Sheng [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States); Zhu, Huiyuan [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-06-07

    Controlling the physical and chemical properties of alloy nanoparticles (NPs) is an important approach to optimize NP catalysis. Unlike other tuning knobs, such as size, shape, and composition, crystal structure has received limited attention and not been well understood for its role in catalysis. This deficiency is mainly due to the difficulty in synthesis and fine-tuning of the NPs’ crystal structure. Here, Exemplifying by AuCu alloy NPs with face centered cubic (fcc) and face centered tetragonal (fct) structure, we demonstrate a remarkable difference in phase segregation and catalytic performance depending on the crystal structure. During the thermal treatment in air, the Cu component in fcc-AuCu alloy NPs segregates more easily onto the alloy surface as compared to that in fct-AuCu alloy NPs. As a result, after annealing at 250 °C in air for 1 h, the fcc- and fct-AuCu alloy NPs are phase transferred into Au/CuO and AuCu/CuO core/shell structures, respectively. More importantly, this variation in heterostructures introduces a significant difference in CO adsorption on two catalysts, leading to a largely enhanced catalytic activity of AuCu/CuO NP catalyst for CO oxidation. Furthermore, the same concept can be extended to other alloy NPs, making it possible to fine-tune NP catalysis for many different chemical reactions.

  15. Crystallization Behavior of Poly(ethylene oxide) in Vertically Aligned Carbon Nanotube Array.

    Science.gov (United States)

    Sheng, Jiadong; Zhou, Shenglin; Yang, Zhaohui; Zhang, Xiaohua

    2018-03-27

    We investigate the effect of the presence of vertically aligned multiwalled carbon nanotubes (CNTs) on the orientation of poly(ethylene oxide) (PEO) lamellae and PEO crystallinity. The high alignment of carbon nanotubes acting as templates probably governs the orientation of PEO lamellae. This templating effect might result in the lamella planes of PEO crystals oriented along a direction parallel to the long axis of the nanotubes. The presence of aligned carbon nanotubes also gives rise to the decreases in PEO crystallinity, crystallization temperature, and melting temperature due to the perturbation of carbon nanotubes to the crystallization of PEO. These effects have significant implications for controlling the orientation of PEO lamellae and decreasing the crystallinity of PEO and thickness of PEO lamellae, which have significant impacts on ion transport in PEO/CNT composite and the capacitive performance of PEO/CNT composite. Both the decreased PEO crystallinity and the orientation of PEO lamellae along the long axes of vertically aligned CNTs give rise to the decrease in the charge transfer resistance, which is associated with the improvements in the ion transport and capacitive performance of PEO/CNT composite.

  16. Design of photonic crystal surface emitting lasers with indium-tin-oxide top claddings

    Science.gov (United States)

    Huang, Shen-Che; Hong, Kuo-Bin; Chiu, Han-Lun; Lan, Shao-Wun; Chang, Tsu-Chi; Li, Heng; Lu, Tien-Chang

    2018-02-01

    Electrically pumped GaAs-based photonic crystal surface emitting lasers were fabricated using a simple fabrication process by directly capping the indium-tin-oxide transparent conducting thin film as the top cladding layer upon a photonic crystal layer. Optimization of the separate-confinement heterostructures of a laser structure is crucial to improving characteristics by providing advantageous optical confinements. The turn-on voltage, series resistance, threshold current, and slope efficiency of the laser with a 100 × 100 μm2 photonic crystal area operated at room temperature were 1.3 V, 1.5 Ω, 121 mA, and 0.2 W/A, respectively. Furthermore, we demonstrated a single-lobed lasing wavelength of 928.6 nm at 200 mA and a wavelength redshift rate of 0.05 nm/K in temperature-dependent measurements. The device exhibited the maximum output power of approximately 400 mW at an injection current of 2 A; moreover, divergence angles of less than 1° for the unpolarized circular-shaped laser beam were measured at various injection currents. Overall, the low threshold current, excellent beam quality, small divergence, high output power, and high-operating-temperature (up to 343 K) of our devices indicate that they can potentially fill the requirements for next-generation light sources and optoelectronic devices.

  17. Crystal Structure of Mammalian Cysteine dioxygenase: A Novel Mononuclear Iron Center for Cysteine Thiol Oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Simmons,C.; Liu, Q.; Huang, Q.; Hao, Q.; Begley, T.; Karplus, P.; Stipanuk, M.

    2006-01-01

    Cysteine dioxygenase is a mononuclear iron-dependent enzyme responsible for the oxidation of cysteine with molecular oxygen to form cysteinesulfinate. This reaction commits cysteine to either catabolism to sulfate and pyruvate or to the taurine biosynthetic pathway. Cysteine dioxygenase is a member of the cupin superfamily of proteins. The crystal structure of recombinant rat cysteine dioxygenase has been determined to 1.5 Angstroms resolution, and these results confirm the canonical cupin {beta}-sandwich fold and the rare cysteinyl-tyrosine intramolecular crosslink (between Cys93 and Tyr157) seen in the recently reported murine cysteine dioxygenase structure. In contrast to the catalytically inactive mononuclear Ni(II) metallocenter present in the murine structure, crystallization of a catalytically competent preparation of rat cysteine dioxygenase revealed a novel tetrahedrally coordinated mononuclear iron center involving three histidines (His86, His88, and His140) and a water molecule. Attempts to acquire a structure with bound ligand using either co-crystallization or soaks with cysteine revealed the formation of a mixed disulfide involving Cys164 near the active site, which may explain previously observed substrate inhibition. This work provides a framework for understanding the molecular mechanisms involved in thiol dioxygenation and sets the stage for exploring the chemistry of both the novel mononuclear iron center and the catalytic role of the cysteinyl-tyrosine linkage.

  18. Effects of surface crystallization and oxidation in nanocrystalline FeNbCuSiB(P) ribbons

    Energy Technology Data Exchange (ETDEWEB)

    Butvinová, B., E-mail: beata.butvinova@savba.sk [Institute of Physics SAS, Dúbravská cesta 9, 845 11 Bratislava (Slovakia); Butvin, P. [Institute of Physics SAS, Dúbravská cesta 9, 845 11 Bratislava (Slovakia); Brzózka, K. [Department of Physics, University of Technology and Humanities in Radom, Krasickiego 54, 26-600 Radom (Poland); Kuzminski, M. [Institute of Physics PAS, Al. Lotnikow 36/42, 02-668 Warsaw (Poland); Maťko, I.; Švec Sr, P. [Institute of Physics SAS, Dúbravská cesta 9, 845 11 Bratislava (Slovakia); Chromčíková, M. [Institute of Inorg. Chem. SAS, Centrum VILA, Študentská 2, 911 50 Trenčín (Slovakia)

    2017-02-15

    Si-poor Fe{sub 74}Nb{sub 3}Cu{sub 1}Si{sub 8}B{sub 14−x}P{sub x}, (x=0, 3) nanocrystalline ribbon-form alloys often form surfaces, which exert in-plane force on underlying ribbon interior when nanocrystallized in even modest presence of oxygen. Mostly unwanted hard-ribbon-axis magnetic anisotropy is standard result. Essential sources of the surface-caused stress have been sought and influence of P instead of B substitution on this effect was studied too. Preferred surface crystallization (PSC) was found to be the major reason. However P substitution suppresses PSC and promotes Fe-oxide formation, which eases the stress, softens the surfaces and provides different annealing evolution of surface properties. - Highlights: • Ar anneal of low-Si FeNbCuBSi ribbons produce surfaces that stress ribbon interior. • The stress comes mainly from preferred crystallization of surfaces. • Partial substitution of B by P changes annealing evolution of surface properties. • Without P, more crystalline surfaces significantly reduce ribbon's elasticity. • P suppresses surface crystallinity, promotes oxides and reduces mutual stress.

  19. Three-dimensional hole transport in nickel oxide by alloying with MgO or ZnO

    Science.gov (United States)

    Alidoust, Nima; Carter, Emily A.

    2015-11-01

    It has been shown previously that the movement of a hole in nickel oxide is confined to two dimensions, along a single ferromagnetic plane. Such confinement may hamper hole transport when NiO is used as a p-type transparent conductor in various solar energy conversion technologies. Here, we use the small polaron model, along with unrestricted Hartree-Fock and complete active space self-consistent field calculations to show that forming substitutional MxNi1-xO alloys with M = Mg or Zn reduces the barrier for movement of a hole away from the ferromagnetic plane to which it is confined. Such reduction occurs for hole transfer alongside one or two M ions that have been substituted for Ni ions. Furthermore, the Mg and Zn ions do not trap holes on O sites in their vicinity, and NiO's transparency is preserved upon forming the alloys. Thus, forming MxNi1-xO alloys with M = Mg or Zn may enhance NiO's potential as a p-type transparent conducting oxide, by disrupting the two-dimensional confinement of holes in pure NiO.

  20. ZnO quantum dots–decorated ZnO nanowires for the enhancement of antibacterial and photocatalytic performances

    International Nuclear Information System (INIS)

    Wu, Jyh Ming; Tsay, Li-Yi

    2015-01-01

    We demonstrate highly antibacterial activities for killing off Staphylococcus aureus and Escherichia coli using ZnO nanowires decorated with ZnO quantum dots (so-called ZnO QDs/NWs) under visible-light irradiation and dark conditions. The average size of the ZnO QDs is in the range of 3–5 nm; these were uniformly dispersed on the ZnO nanowires’ surface to form the ZnO QDs/NWs. A significant blue-shift effect was observed using photoluminescence (PL) spectra. The size of the ZnO QDs is strongly dependent on the material’s synthesis time. The ZnO QDs/NWs exhibited an excellent photocatalytic activity under visible-light irradiation. The ZnO QDs’ active sites (i.e. the O–H bond and Zn"2"+) accelerate the photogenerated-carrier migration from the QDs to the NWs. As a consequence, the electrons reacted with the dissolved oxygen to form oxygen ions and produced hydroperoxyl radicals to enhance photocatalytic activity. The antibacterial activities (as indicated by R-factor-inhibiting activity) of the ZnO QDs/NWs for killing off Staphylococcus aureus and Escherichia coli is around 4.9 and 5.5 under visible-light irradiation and dark conditions, respectively. The hydroxyl radicals served as an efficient oxidized agent for decomposing the organic dye and microorganism species. The antibacterial activities of the ZnO QDs/NWs in the dark may be attributed to the Zn"2"+ ions that were released from the ZnO QDs and infused into the microbial solution against the growth of bacteria thus disrupting the microorganism. The highly antibacterial and photocatalytic activity of the ZnO QDs/NWs can be well implanted on a screen window, thus offering a promising solution to inhibit the spread of germs under visible-light and dark conditions. (paper)

  1. Exploring the potential of laser assisted flow deposition grown ZnO for photovoltaic applications

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, J., E-mail: joana.catarina@ua.pt [Departamento de Física & I3N, Universidade de Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro (Portugal); Cerqueira, A.F.R.; Sousa, M.G.; Santos, N.F. [Departamento de Física & I3N, Universidade de Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro (Portugal); Pimentel, A.; Fortunato, E. [CENIMAT/I3N, Departamento de Ciência dos Materiais, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Cunha, A.F. da; Monteiro, T.; Costa, F.M. [Departamento de Física & I3N, Universidade de Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro (Portugal)

    2016-07-01

    Zinc oxide (ZnO) is a widely studied wide band gap semiconductor with applications in several fields, namely to enhance solar cells efficiency. Its ability to be grown in a wide variety of nanostructured morphologies, allowing the designing of the surface area architecture constitutes an important advantage over other semiconductors. Laser assisted flow deposition (LAFD) is a recently developed growth method, based on a vapour-solid mechanism, which proved to be a powerful approach in the production of ZnO micro/nanostructures with different morphologies as well as high crystallinity and optical quality. In the present work we report the use of the LAFD technique to grow functional ZnO nanostructures (nanoparticles and tetrapods) working as nano templates to improve the dye-sensitized solar cells (DSSCs) efficiency. The structural and morphological characterization of the as-grown ZnO crystals were performed by X-ray diffraction and electron microscopy, respectively, and the optical quality was assessed by photoluminescence spectroscopy. DSSCs were produced using a combination of these nanostructures, which were subsequently sensitized with N719 dye. An efficiency of ∼3% was achieved under simulated AM 1.5 illumination conditions for a dye loading time of 1 h. - Highlights: • Laser assisted flow deposition proved to be an efficient technique to produce high quality ZnO. • Active layer formed by an interconnected network of tetrapods and a small amount of nanoparticles. • Efficiency of ∼3% obtained under simulated AM 1.5 illumination conditions.

  2. Controlled reduction and oxidation of La0.85Sr0.15MnO3 single crystals

    International Nuclear Information System (INIS)

    De Leon-Guevara, A.M.; Berthet, P.; Berthon, J.; Millot, F.; Revcolevschi, A.

    1997-01-01

    La 0.85 Sr 0.15 MnO 3 single crystals were grown by the floating zone method. They can be reversibly reduced under controlled oxygen partial pressure. Their defect chemistry is investigated together with the evolution of their cell parameters and that of their electric conductivity which is very sensitive to their oxygen content. On the other hand, stoichiometric crystals can be oxidized with a slow kinetics making possible the preparation of diphasic materials. (orig.)

  3. Mid-temperature deep removal of hydrogen sulfide on rare earth (RE = Ce, La, Sm, Gd) doped ZnO supported on KIT-6: Effect of RE dopants and interaction between active phase and support matrix

    Science.gov (United States)

    Li, Lu; Zhou, Pin; Zhang, Hongbo; Meng, Xianglong; Li, Juexiu; Sun, Tonghua

    2017-06-01

    Rare earth oxides (RE = Ce, La, Sm and Gd) doped ZnO supported on KIT-6 sorbents (RE-ZnO/KIT-6) were synthesized by sol-gel method and their performance for deep removal of H2S (bellow 0.1 ppmv) from gas stream at medium temperature was tested. The RE dopants (except Ce) significantly enhance the deep desulfurization capacity of ZnO/KIT-6 sorbent and maintained higher sulfur uptake capacities upon multiple cycles of regeneration by a simple thermal oxidation in 10 v% of O2 in N2 atmosphere. The results of SAXS, XRD, N2 physisorption, TEM, FIIR, and XPS implied that the KIT-6 structure of loading metal oxides remained intact. It was found that RE could hinder the ZnO crystal ripening during calcination resulted in smaller ZnO particles, enhance the interaction of ZnO and silica matrix to improve the dispersion of active phase on KIT-6. Furthermore, by increasing the outlayer electron density of Zn atom and oxygen transfer ability, the synergistic effect considered to be favorable for RE-ZnO/KIT-6 sulfidation. Even though the performance of improving ZnO dispersion was weaker than that of Sm and Gd, La-ZnO/KIT-6 performs the best deep desulfurizers by changing the surface chemical atmosphere for ZnO. Steam in the gas stream inhibited the capture of H2S by ZnO in the sorbents, in the case of La-ZnO/KIT-6, the steam content should control as lower as 5 v% to ensure the desulfurization efficiency and precision.

  4. From Bloch to random lasing in ZnO self-assembled nanostructures

    DEFF Research Database (Denmark)

    Garcia-Fernandez, Pedro David; Cefe, López

    2013-01-01

    In this paper, we present measurements on UV lasing in ZnO ordered and disordered nanostructures. Bloch lasing is achieved in the ordered structures by exploiting very low group-velocity Bloch modes in ZnO photonic crystals. In the second case, random lasing is observed in ZnO photonic glasses. We...... study the lasing threshold in both cases and its dependence on the structural parameters. Finally, we present the transition from Bloch to random lasing by deliberately doping a ZnO inverse photonic crystal with a controlled amount of lattice vacancies effectively converting it into a translationally...

  5. Application of Chemical Doping and Architectural Design Principles To Fabricate Nanowire Co2Ni3ZnO8 Arrays for Aqueous Asymmetric Supercapacitors.

    Science.gov (United States)

    Liu, Qi; Yang, Bin; Liu, Jingyuan; Yuan, Yi; Zhang, Hongsen; Liu, Lianhe; Wang, Jun; Li, Rumin

    2016-08-10

    Electrode materials derived from transition metal oxides have a serious problem of low electron transfer rate, which restricts their practical application. However, chemically doped graphene transforms the chemical bonding configuration to enhance electron transfer rate and, therefore, facilitates the successful fabrication of Co2Ni3ZnO8 nanowire arrays. In addition, the Co2Ni3ZnO8 electrode materials, considered as Ni and Zn ions doped into Co3O4, have a high electron transfer rate and electrochemical response capability, because the doping increases the degree of crystal defect and reaction of Co/Ni ions with the electrolyte. Hence, the Co2Ni3ZnO8 electrode exhibits a high rate property and excellent electrochemical cycle stability, as determined by electrochemical analysis of the relationship between specific capacitance, IR drop, Coulomb efficiency, and different current densities. From the results of a three-electrode system of electrochemical measurement, the Co2Ni3ZnO8 electrode demonstrates a specific capacitance of 1115 F g(-1) and retains 89.9% capacitance after 2000 cycles at a current density of 4 A g(-1). The energy density of the asymmetric supercapacitor (AC//Co2Ni3ZnO8) is 54.04 W h kg(-1) at the power density of 3200 W kg(-1).

  6. Short review of high-pressure crystal growth and magnetic and electrical properties of solid-state osmium oxides

    Energy Technology Data Exchange (ETDEWEB)

    Yamaura, Kazunari, E-mail: YAMAURA.Kazunari@nims.go.jp [Superconducting Properties Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Graduate School of Chemical Sciences and Engineering, Hokkaido University, North 10 West 8, Kita-ku, Sapporo, Hokkaido 060-0810 (Japan)

    2016-04-15

    High-pressure crystal growth and synthesis of selected solid-state osmium oxides, many of which are perovskite-related types, are briefly reviewed, and their magnetic and electrical properties are introduced. Crystals of the osmium oxides, including NaOsO{sub 3}, LiOsO{sub 3}, and Na{sub 2}OsO{sub 4}, were successfully grown under high-pressure and high-temperature conditions at 6 GPa in the presence of an appropriate amount of flux in a belt-type apparatus. The unexpected discovery of a magnetic metal–insulator transition in NaOsO{sub 3}, a ferroelectric-like transition in LiOsO{sub 3}, and high-temperature ferrimagnetism driven by a local structural distortion in Ca{sub 2}FeOsO{sub 6} may represent unique features of the osmium oxides. The high-pressure and high-temperature synthesis and crystal growth has played a central role in the development of solid-state osmium oxides and the elucidation of their magnetic and electronic properties toward possible use in multifunctional devices. - Graphical Abstract: Flux-grown crystals of NaOsO{sub 3} under high-pressure and high-temperature conditions in a belt-type apparatus. The crystal shows a magnetically driven metal–insulator transition at a temperature of 410 K. - Highlights: • Short review of high-pressure crystal growth of solid-state osmium oxides. • Wide variety of magnetic properties of solid-state osmium oxides. • Perovskite and related dense structures stabilized at 3–17 GPa.

  7. Comparison of modification strategies towards enhanced charge carrier separation and photocatalytic degradation activity of metal oxide semiconductors (TiO{sub 2}, WO{sub 3} and ZnO)

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, S. Girish [Department of Physics, Indian Institute of Science, Bengaluru, 560012 Karnataka (India); Department of Chemistry, School of Engineering and Technology, CMR University, Bengaluru, 562149, Karnataka (India); Rao, K.S.R. Koteswara, E-mail: raoksrk@gmail.com [Department of Physics, Indian Institute of Science, Bengaluru, 560012 Karnataka (India)

    2017-01-01

    Graphical abstract: Semiconductor metal oxides: Modifications, charge carrier dynamics and photocatalysis. - Highlights: • TiO{sub 2}, WO{sub 3} and ZnO based photocatalysis is reviewed. • Advances to improve the efficiency are emphasized. • Differences and similarities in the modifications are highlighted. • Charge carrier dynamics for each strategy are discussed. - Abstract: Metal oxide semiconductors (TiO{sub 2}, WO{sub 3} and ZnO) finds unparalleled opportunity in wastewater purification under UV/visible light, largely encouraged by their divergent admirable features like stability, non-toxicity, ease of preparation, suitable band edge positions and facile generation of active oxygen species in the aqueous medium. However, the perennial failings of these photocatalysts emanates from the stumbling blocks like rapid charge carrier recombination and meager visible light response. In this review, tailoring the surface-bulk electronic structure through the calibrated and veritable approaches such as impurity doping, deposition with noble metals, sensitizing with other compounds (dyes, polymers, inorganic complexes and simple chelating ligands), hydrogenation process (annealing under hydrogen atmosphere), electronic integration with other semiconductors, modifying with carbon nanostructures, designing with exposed facets and tailoring with hierarchical morphologies to overcome their critical drawbacks are summarized. Taking into account the materials intrinsic properties, the pros and cons together with similarities and striking differences for each strategy in specific to TiO{sub 2}, WO{sub 3} & ZnO are highlighted. These subtlety enunciates the primacy for improving the structure-electronic properties of metal oxides and credence to its fore in the practical applications. Future research must focus on comparing the performances of ZnO, TiO{sub 2} and WO{sub 3} in parallel to get insight into their photocatalytic behaviors. Such comparisons not only reveal

  8. Processing of ZnO nanocrystals by solochemical technique

    International Nuclear Information System (INIS)

    Gusatti, M.; Speckhahn, R.; Silva, L.A.; Rosario, J.A.; Lima, R.B.; Kuhnen, N.C.; Riella, H.G.; Campos, C.E.M.

    2009-01-01

    In the present work, we report the synthesis of high quality ZnO nanocrystals by solochemical technique. This synthetic strategy has been shown to have advantages over other methods of producing nanostructures in terms of low cost, efficiency, simplicity and uniformity of crystal structure. Zinc chloride solution at room temperature was mixed with sodium hydroxide solution at 50°C to produce ZnO nanocrystals. Transmission electronic microscopy (TEM) and X-ray powder diffraction (XRD) were used to characterize the ZnO nanocrystals obtained. The structure of ZnO was refined by the Rietveld Method from X-ray diffraction data. These methods showed that the product consisted of pure ZnO nanocrystals and has, predominantly, a rod-like morphology. (author)

  9. Heterogeneous Reaction of SO2 on Manganese Oxides: the Effect of Crystal Structure and Relative Humidity.

    Science.gov (United States)

    Yang, Weiwei; Zhang, Jianghao; Ma, Qingxin; Zhao, Yan; Liu, Yongchun; He, Hong

    2017-07-03

    Manganese oxides from anthropogenic sources can promote the formation of sulfate through catalytic oxidation of SO 2 . In this study, the kinetics of SO 2 reactions on MnO 2 with different morphologies (α, β, γ and δ) was investigated using flow tube reactor and in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). Under dry conditions, the reactivity towards SO 2 uptake was highest on δ-MnO 2 but lowest on β-MnO 2 , with a geometric uptake coefficient (γ obs ) of (2.42 ± 0.13) ×10 -2 and a corrected uptake coefficient (γ c ) of (1.48 ± 0.21) ×10 -6 for the former while γ obs of (3.35 ± 0.43) ×10 -3 and γ c of (7.46 ± 2.97) ×10 -7 for the latter. Under wet conditions, the presence of water altered the chemical form of sulfate and was in favor for the heterogeneous oxidation of SO 2 . The maximum sulfate formation rate was reached at 25% RH and 45% for δ-MnO 2 and γ-MnO 2 , respectively, possibly due to their different crystal structures. The results suggest that morphologies and RH are important factors influencing the heterogeneous reaction of SO 2 on mineral aerosols, and that aqueous oxidation process involving transition metals of Mn might be a potential important pathway for SO 2 oxidation in the atmosphere.

  10. High temperature oxidation behavior of aluminide on a Ni-based single crystal superalloy in different surface orientations

    Institute of Scientific and Technical Information of China (English)

    Fahamsyah H.Latief; Koji Kakehi; El-Sayed M.Sherif

    2014-01-01

    An investigation on oxidation behavior of coated Ni-based single crystal superalloy in different surface orientations has been carried out at 1100 1C. It has been found that the {100} surface shows a better oxidation resistance than the {110} one, which is attributed that the {110}surface had a slightly higher oxidation rate when compared to the {100} surface. The experimental results also indicated that the anisotropic oxidation behavior took place even with a very small difference in the oxidation rates that was found between the two surfaces. The differences of the topologically close packed phase amount and its penetration depth between the two surfaces, including the ratio of α-Al2O3 after 500 h oxidation, were responsible for the oxidation anisotropy.

  11. Analysis of thermal treatment effects upon optico-luminescent and scintillation characteristics of oxide and chalcogenide crystals

    International Nuclear Information System (INIS)

    Ryzhikov, Vladimir D.; Grinyov, Boris V.; Pirogov, Evgeniy N.; Galkin, Sergey N.; Nagornaya, Lyudmila L.; Bondar, Vladimir G.; Babiychuk, Inna P.; Krivoshein, Vadim I.; Silin, Vitaliy I.; Lalayants, Alexandr I.; Voronkin, Evgeniy F.; Katrunov, Konstantin A.; Onishchenko, Gennadiy M.; Vostretsov, Yuriy Ya.; Malyi, Pavel Yu.; Lisetskaya, Elena K.; Lisetskii, Longin N.

    2005-01-01

    This work has been aimed at analyzing the effects of various thermal treatment factors upon optical-luminescent, scintillation and other functional characteristics of complex oxide and chalcogenide crystals. The crystals considered in this work are scintillators with intrinsic (PWO, CWO, BGO), activator (GSO:Ce) or complex-defect ZnSe(Te) type of luminescence. Important factors of thermal treatment are not only the temperature and its variation with time, but also the chemical composition of the annealing medium, its oxidation-reduction properties

  12. Green Synthesized Zinc Oxide (ZnO Nanoparticles Induce Oxidative Stress and DNA Damage in Lathyrus sativus L. Root Bioassay System

    Directory of Open Access Journals (Sweden)

    Kamal K. Panda

    2017-05-01

    Full Text Available Zinc oxide nanoparticles (ZnONP-GS were synthesised from the precursor zinc acetate (Zn(CH3COO2 through the green route using the milky latex from milk weed (Calotropis gigantea L. R. Br by alkaline precipitation. Formation of the ZnONP-GS was monitored by UV-visible spectroscopy followed by characterization and confirmation by energy-dispersive X-ray spectroscopy (EDX, transmission electron microscopy (TEM, and X-ray diffraction (XRD. Both the ZnONP-GS and the commercially available ZnONP-S (Sigma-Aldrich and cationic Zn2+ from Zn(CH3COO2 were tested in a dose range of 0–100 mg·L−1 for their potency (i to induce oxidative stress as measured by the generation reactive oxygen species (ROS: O2•−, H2O2 and •OH, cell death, and lipid peroxidation; (ii to modulate the activities of antioxidant enzymes: catalase (CAT, superoxide dismutase (SOD, guaiacol peroxidase (GPX, and ascorbate peroxidase (APX; and (iii to cause DNA damage as determined by Comet assay in Lathyrus sativus L. root bioassay system. Antioxidants such as Tiron and dimethylthiourea significantly attenuated the ZnONP-induced oxidative and DNA damage, suggesting the involvement of ROS therein. Our study demonstrated that both ZnONP-GS and ZnONP-S induced oxidative stress and DNA damage to a similar extent but were significantly less potent than Zn2+ alone.

  13. Green Synthesized Zinc Oxide (ZnO) Nanoparticles Induce Oxidative Stress and DNA Damage in Lathyrus sativus L. Root Bioassay System.

    Science.gov (United States)

    Panda, Kamal K; Golari, Dambaru; Venugopal, A; Achary, V Mohan M; Phaomei, Ganngam; Parinandi, Narasimham L; Sahu, Hrushi K; Panda, Brahma B

    2017-05-18

    Zinc oxide nanoparticles (ZnONP-GS) were synthesised from the precursor zinc acetate (Zn(CH₃COO)₂) through the green route using the milky latex from milk weed ( Calotropis gigantea L. R. Br) by alkaline precipitation. Formation of the ZnONP-GS was monitored by UV-visible spectroscopy followed by characterization and confirmation by energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Both the ZnONP-GS and the commercially available ZnONP-S (Sigma-Aldrich) and cationic Zn 2+ from Zn(CH₃COO)₂ were tested in a dose range of 0-100 mg·L -1 for their potency (i) to induce oxidative stress as measured by the generation reactive oxygen species (ROS: O₂ •- , H₂O₂ and • OH), cell death, and lipid peroxidation; (ii) to modulate the activities of antioxidant enzymes: catalase (CAT), superoxide dismutase (SOD), guaiacol peroxidase (GPX), and ascorbate peroxidase (APX); and (iii) to cause DNA damage as determined by Comet assay in Lathyrus sativus L. root bioassay system. Antioxidants such as Tiron and dimethylthiourea significantly attenuated the ZnONP-induced oxidative and DNA damage, suggesting the involvement of ROS therein. Our study demonstrated that both ZnONP-GS and ZnONP-S induced oxidative stress and DNA damage to a similar extent but were significantly less potent than Zn 2+ alone.

  14. Micro-nano zinc oxide film fabricated by biomimetic mineralization: Designed architectures for SERS substrates

    Science.gov (United States)

    Lu, Fei; Guo, Yue; Wang, Yunxin; Song, Wei; Zhao, Bing

    2018-05-01

    In this study, we have investigated the effect of the surface morphologies of the zinc oxide (ZnO) substrates on surface enhanced Raman spectroscopy (SERS). During synthetic process, the self-assembly monolayers (SAMs) with different terminal groups are used as templates to induce the nucleation and growth of Zn(NO3)2·6H2O crystals, then different morphologies micro-nano ZnO powders are obtained by annealing Zn(NO3)2·6H2O crystals at 450 °C. The products obtained at different conditions are characterized by means of X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM) and Raman spectra. The as-prepared ZnO micro-sized particles have been used the efficient Surface enhanced Raman scattering (SERS) substrates, and the SERS signals of 4-mercaptopyridine (Mpy) probe molecules are much influenced by the morphologies of the ZnO structures. Results indicated that the more (0001) facets appear in the of ZnO morphology, the greater degree of charge-transfer (PCT) for the SERS enhancement on the surface of semiconductors is achieved. The chemical interaction between ZnO structures and Mpy molecules plays a very important role in the SERS enhancement.

  15. Phenoxo bridged dinuclear Zn(II) Schiff base complex as new precursor for preparation zinc oxide nanoparticles: Synthesis, characterization, crystal structures and photoluminescence studies

    Energy Technology Data Exchange (ETDEWEB)

    Saeednia, S., E-mail: sami_saeednia@yahoo.com [Department of Chemistry, Faculty of Science, Vali-e-Asr University of Rafsanjan, Rafsanjan 77188-97111 (Iran, Islamic Republic of); Iranmanesh, P. [Department of physics, Faculty of Science, Vali-e-Asr University of Rafsanjan, Rafsanjan 77188-97111 (Iran, Islamic Republic of); Ardakani, M. Hatefi; Mohammadi, M.; Norouzi, Gh. [Department of Chemistry, Faculty of Science, Vali-e-Asr University of Rafsanjan, Rafsanjan 77188-97111 (Iran, Islamic Republic of)

    2016-06-15

    Highlights: • A novel nano-scale Zn(II) complex was synthesized by solvothermal method. • Chemical structure of the nanostructures was characterized as well as bulk complex. • The photoluminescence property of the complex was investigated at room temperature. • The thermogravimetry and differential thermal analysis were carried out. • Thermal decomposition of the nanostructures was prepared zinc oxide nanoparticles. - Abstract: Nanoparticles of a novel Zn(II) Schiff base complex, [Zn(HL)NO{sub 3}]{sub 2} (1), (H{sub 2}L = 2-[(2-hydroxy-propylimino) methyl] phenol), was synthesized by using solvothermal method. Shape, morphology and chemical structure of the synthesized nanoparticles were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Fourier Transform Infrared Spectoscopy (FT-IR) and UV–vis spectroscopy. Structural determination of compound 1 was determined by single-crystal X-ray diffraction. The results were revealed that the zinc complex is a centrosymmetric dimer in which deprotonated phenolates bridge the two five-coordinate metal atoms and link the two halves of the dimer. The thermal stability of compound 1 was analyzed by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The effect of the initial substrates concentration and reaction time on size and morphology of compound 1 nanostructure was investigated as well. Furthermore, the luminescent properties of the complex 1 were examined. ZnO nanoparticles with diameter between 15 and 20 nm were simply synthesized by solid-state transformation of compound 1 at 700 °C.

  16. Photoluminescence measurements of ZnO heterostructures

    International Nuclear Information System (INIS)

    Adachi, Yutaka; Sakaguchi, Isao; Ohashi, Naoki; Haneda, Hajime; Ryoken, Haruki; Takenaka, Tadashi

    2003-01-01

    ZnO thin films were grown on TbAlO 3 single crystal substrates by pulsed laser deposition. In photoluminescence (PL) measurements, strong emissions from TbAlO 3 were observed with the emission from ZnO when the film thickness was less than 100 nm. The relationship between the ZnO film thickness and the emission intensity from TbAlO 3 was investigated in order to determine the penetration depth of excitation light. Information on the heterostructures ranging from the surface to a depth of 300 nm was obtained by PL measurements in this study, and the absorption coefficient for a wavelength of 325 nm was estimated to be 1.31x10 5 cm -1 . (author)

  17. High-Performance Schottky Diode Gas Sensor Based on the Heterojunction of Three-Dimensional Nanohybrids of Reduced Graphene Oxide-Vertical ZnO Nanorods on an AlGaN/GaN Layer.

    Science.gov (United States)

    Minh Triet, Nguyen; Thai Duy, Le; Hwang, Byeong-Ung; Hanif, Adeela; Siddiqui, Saqib; Park, Kyung-Ho; Cho, Chu-Young; Lee, Nae-Eung

    2017-09-13

    A Schottky diode based on a heterojunction of three-dimensional (3D) nanohybrid materials, formed by hybridizing reduced graphene oxide (RGO) with epitaxial vertical zinc oxide nanorods (ZnO NRs) and Al 0.27 GaN 0.73 (∼25 nm)/GaN is presented as a new class of high-performance chemical sensors. The RGO nanosheet layer coated on the ZnO NRs enables the formation of a direct Schottky contact with the AlGaN layer. The sensing results of the Schottky diode with respect to NO 2 , SO 2 , and HCHO gases exhibit high sensitivity (0.88-1.88 ppm -1 ), fast response (∼2 min), and good reproducibility down to 120 ppb concentration levels at room temperature. The sensing mechanism of the Schottky diode can be explained by the effective modulation of the reverse saturation current due to the change in thermionic emission carrier transport caused by ultrasensitive changes in the Schottky barrier of a van der Waals heterostructure between RGO and AlGaN layers upon interaction with gas molecules. Advances in the design of a Schottky diode gas sensor based on the heterojunction of high-mobility two-dimensional electron gas channel and highly responsive 3D-engineered sensing nanomaterials have potential not only for the enhancement of sensitivity and selectivity but also for improving operation capability at room temperature.

  18. Enhanced ultraviolet photo-response in Dy doped ZnO thin film

    Science.gov (United States)

    Kumar, Pawan; Singh, Ranveer; Pandey, Praveen C.

    2018-02-01

    In the present work, a Dy doped ZnO thin film deposited by the spin coating method has been studied for its potential application in a ZnO based UV detector. The investigations on the structural property and surface morphology of the thin film ensure that the prepared samples are crystalline and exhibit a hexagonal crystal structure of ZnO. A small change in crystallite size has been observed due to Dy doping in ZnO. AFM analysis ascertains the grain growth and smooth surface of the thin films. The Dy doped ZnO thin film exhibits a significant enhancement in UV region absorption as compared to the pure ZnO thin film, which suggests that Dy doped ZnO can be used as a UV detector. Under UV irradiation of wavelength 325 nm, the photocurrent value of Dy doped ZnO is 105.54 μA at 4.5 V, which is 31 times greater than that of the un-doped ZnO thin film (3.39 μA). The calculated value of responsivity is found to increase significantly due to the incorporation of Dy in the ZnO lattice. The observed higher value of photocurrent and responsivity could be attributed to the substitution of Dy in the ZnO lattice, which enhances the conductivity, electron mobility, and defects in ZnO and benefits the UV sensing property.

  19. Crystal growth, structural, optical, thermal, mechanical, laser damage threshold and electrical properties of triphenylphosphine oxide 4-nitrophenol (TP4N) single crystals for nonlinear optical applications

    Science.gov (United States)

    Karuppasamy, P.; Senthil Pandian, Muthu; Ramasamy, P.; Verma, Sunil

    2018-05-01

    The optically good quality single crystals of triphenylphosphine oxide 4-nitrophenol (TP4N) with maximum dimension of 15 × 10 × 5 mm3 were grown by slow evaporation solution technique (SEST) at room temperature. The cell dimensions of the grown TP4N crystal were confirmed by single crystal X-ray diffraction (SXRD) and the crystalline purity was confirmed and planes were indexed by powder X-ray diffraction (PXRD) analysis. Functional groups of TP4N crystal were confirmed by Fourier transform infrared (FTIR) spectral analysis. The optical transmittance of the grown crystal was determined by the UV-Vis NIR spectral analysis and it has good optical transparency in the entire visible region. The band tail (Urbach) energy of the grown crystal was analyzed and it appears to be minimum, which indicates that the TP4N has good crystallinity. The position of valence band (Ev) and conduction band (Ec) of the TP4N have been determined from the electron affinity energy (EA) and the ionization energy (EI) of its elements and using the optical band gap. The thermal behaviour of the grown crystal was investigated by thermogravimetric and differential thermal analysis (TG-DTA). Vickers microhardness analysis was carried out to identify the mechanical stability of the grown crystal and their indentation size effect (ISE) was explained by the Meyer's law (ML), Hays-Kendall's (HK) approach, proportional specimen resistance (PSR) model, modified PSR model (MPSR), elastic/plastic deformation (EPD) model and indentation induced cracking (IIC) model. Chemical etching study was carried out to find the etch pit density (EPD) of the grown crystal. Laser damage threshold (LDT) value was measured by using Nd:YAG laser (1064 nm). The dielectric permittivity (ε՛) and dielectric loss (tan δ) as a function of frequency was measured. The electronic polarizability (α) of the TP4N crystal was calculated. It is well matched to the value which was calculated from Clausius-Mossotti relation

  20. Zirconium oxide crystal phase: The role of the pH and time to attain the final pH for precipitation of the hydrous oxide

    International Nuclear Information System (INIS)

    Srinivasan, R.; Harris, M.B.; Simpson, S.F.; De Angelis, R.J.; Davis, B.H.

    1988-01-01

    Precipitated hydrous zirconium oxide can be calcined to produce either a monoclinic or tetragonal product. It has been observed that the time taken to attain the final pH of the solution in contact with the precipitate plays a dominant role in determining the crystal structure of the zirconium oxide after calcination at 500 0 C. The dependence of crystal structure on the rate of precipitation is observed only in the pH range 7--11. Rapid precipitation in this pH range yields predominately monoclinic zirconia, whereas slow (8 h) precipitation produces the tetragonal phase. At pH of approximately 13.0, only the tetragonal phase is formed from both slowly and rapidly precipitated hydrous oxide. The present results, together with earlier results, show that both the pH of the supernatant liquid and the time taken to attain this pH play dominant roles in determining the crystal structure of zirconia that is formed after calcination of the hydrous oxide. The factors that determine the crystal phase are therefore imparted in a mechanism of precipitation that depends upon the pH, and it is inferred that it is the hydroxyl concentration that is the dominant factor

  1. Growth and characterization of polar and nonpolar ZnO film grown on sapphire substrates by using atomic layer deposition

    International Nuclear Information System (INIS)

    Kim, Ki-Wook; Son, Hyo-Soo; Choi, Nak-Jung; Kim, Jihoon; Lee, Sung-Nam

    2013-01-01

    We investigated the electrical and the optical properties of polar and nonpolar ZnO films grown on sapphire substrates with different crystallographic planes. High resolution X-ray results revealed that polar c-plane (0001), nonpolar m-plane (10-10) and a-plane (11-20) ZnO thin films were grown on c-plane, m- and r-sapphire substrates by atomic layer deposition, respectively. Compared with the c-plane ZnO film, nonpolar m-plane and a-plane ZnO films showed smaller surface roughness and anisotropic surface structures. Regardless of ZnO crystal planes, room temperature photoluminescence spectra represented two emissions which consisted of the near bandedge (∼ 380 nm) and the deep level emission (∼ 500 nm). The a-plane ZnO films represented better optical and electrical properties than c-plane ZnO, while m-plane ZnO films exhibited poorer optical and electrical properties than c-plane ZnO. - Highlights: • Growth and characterization of a-, c- and m-plane ZnO film by atomic layer deposition. • The a-plane ZnO represented better optical and electrical properties than c-plane ZnO. • The m-plane ZnO exhibited poorer optical and electrical properties than c-plane ZnO

  2. Improved photovoltaic performance from inorganic perovskite oxide thin films with mixed crystal phases

    Science.gov (United States)

    Chakrabartty, Joyprokash; Harnagea, Catalin; Celikin, Mert; Rosei, Federico; Nechache, Riad

    2018-05-01

    Inorganic ferroelectric perovskites are attracting attention for the realization of highly stable photovoltaic cells with large open-circuit voltages. However, the power conversion efficiencies of devices have been limited so far. Here, we report a power conversion efficiency of 4.20% under 1 sun illumination from Bi-Mn-O composite thin films with mixed BiMnO3 and BiMn2O5 crystal phases. We show that the photocurrent density and photovoltage mainly develop across grain boundaries and interfaces rather than within the grains. We also experimentally demonstrate that the open-circuit voltage and short-circuit photocurrent measured in the films are tunable by varying the electrical resistance of the device, which in turn is controlled by externally applying voltage pulses. The exploitation of multifunctional properties of composite oxides provides an alternative route towards achieving highly stable, high-efficiency photovoltaic solar energy conversion.

  3. Resistive Switching Characteristics in Electrochemically Synthesized ZnO Films

    Directory of Open Access Journals (Sweden)

    Shuhan Jing

    2015-04-01

    Full Text Available The semiconductor industry has long been seeking a new kind of non-volatile memory technology with high-density, high-speed, and low-power consumption. This study demonstrated the electrochemical synthesis of ZnO films without adding any soft or hard templates. The effect of deposition temperatures on crystal structure, surface morphology and resistive switching characteristics were investigated. Our findings reveal that the crystallinity, surface morphology and resistive switching characteristics of ZnO thin films can be well tuned by controlling deposition temperature. A conducting filament based model is proposed to explain the switching mechanism in ZnO thin films.

  4. Oriented ZnO nanostructures and their application in photocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    Man, Minh Tan [Department of Physics, Research Institute of Physics and Chemistry, Chonbuk National University, Jeonju 54896 (Korea, Republic of); Kim, Ji-Hee [Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Suwon 16419 (Korea, Republic of); Sungkyunkwan University (SKKU), Suwon, 16419 (Korea, Republic of); Jeong, Mun Seok [Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Suwon 16419 (Korea, Republic of); Department of Energy Science, Sungkyunkwan University, Suwon, 16419 (Korea, Republic of); Do, Anh-Thu Thi [Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Caugiay, Hanoi (Viet Nam); Lee, Hong Seok, E-mail: hslee1@jbnu.ac.kr [Department of Physics, Research Institute of Physics and Chemistry, Chonbuk National University, Jeonju 54896 (Korea, Republic of)

    2017-05-15

    We report a chemical bath deposition approach for the preparation of large arrays of oriented ZnO nanostructures by activated substrate processes, and precipitated ZnO nanorods by passive occupation of the crystal surface. Photoluminescence dynamics showed that various visible emission characteristics associated with defects such as oxygen vacancy, zinc interstitial or their complexes. In addition, the precipitated ZnO nanorods exhibited excellent performance in the adsorption and photocatalytic decomposition of organic dyes, achieving 95% photodegradation of Rhodamine 6B. Moreover, oxygen defects function as trap sites with strong adsorption abilities towards organic dyes and showed high performance in the photocatalytic degradation of the dye molecules.

  5. Hydrogen-Induced Plastic Deformation in ZnO

    Science.gov (United States)

    Lukáč, F.; Čížek, J.; Vlček, M.; Procházka, I.; Anwand, W.; Brauer, G.; Traeger, F.; Rogalla, D.; Becker, H.-W.

    In the present work hydrothermally grown ZnO single crystals covered with Pd over-layer were electrochemically loaded with hydrogen and the influence of hydrogen on ZnO micro structure was investigated by positron annihilation spectroscopy (PAS). Nuclear reaction analysis (NRA) was employed for determination of depth profile of hydrogen concentration in the sample. NRA measurements confirmed that a substantial amount of hydrogen was introduced into ZnO by electrochemical charging. The bulk hydrogen concentration in ZnO determined by NRA agrees well with the concentration estimated from the transported charge using the Faraday's law. Moreover, a subsurface region with enhanced hydrogen concentration was found in the loaded crystals. Slow positron implantation spectroscopy (SPIS) investigations of hydrogen-loaded crystal revealed enhanced concentration of defects in the subsurface region. This testifies hydrogen-induced plastic deformation of the loaded crystal. Absorbed hydrogen causes a significant lattice expansion. At low hydrogen concentrations this expansion is accommodated by elastic straining, but at higher concentrations hydrogen-induced stress exceeds the yield stress in ZnO and plastic deformation of the loaded crystal takes place. Enhanced hydrogen concentration detected in the subsurface region by NRA is, therefore, due to excess hydrogen trapped at open volume defects introduced by plastic deformation. Moreover, it was found that hydrogen-induced plastic deformation in the subsurface layer leads to typical surface modification: formation of hexagonal shape pyramids on the surface due to hydrogen-induced slip in the [0001] direction.

  6. Morphological Development of Melt Crystallized Poly(propylene oxide) by In Situ AFM: Formation of Banded Spherulites

    NARCIS (Netherlands)

    Beekmans, L.G.M.; Hempenius, Mark A.; Vancso, Gyula J.

    2004-01-01

    The morphology of poly(propylene oxide) (PPO) crystals grown from the melt was investigated. The spherulites of the optically pure S polymers displayed a regular pattern of concentric rings as observed by polarizing optical microscopy, while the stereocopolymer developed irregularly banded, or

  7. High mobility In2O3:H transparent conductive oxides prepared by atomic layer deposition and solid phase crystallization

    NARCIS (Netherlands)

    Macco, B.; Wu, Y.; Vanhemel, D.; Kessels, W.M.M.

    2014-01-01

    The preparation of high-quality In2O3:H, as transparent conductive oxide (TCO), is demonstrated at low temperatures. Amorphous In2O3:H films were deposited by atomic layer deposition at 100 °C, after which they underwent solid phase crystallization by a short anneal at 200 °C. TEM analysis has shown

  8. One-step green synthesis of cuprous oxide crystals with truncated octahedra shapes via a high pressure flux approach

    International Nuclear Information System (INIS)

    Li Benxian; Wang Xiaofeng; Xia Dandan; Chu Qingxin; Liu Xiaoyang; Lu Fengguo; Zhao Xudong

    2011-01-01

    Cuprous oxide (Cu 2 O) was synthesized via reactions between cupric oxide (CuO) and copper metal (Cu) at a low temperature of 300 deg. C. This progress is green, environmentally friendly and energy efficient. Cu 2 O crystals with truncated octahedra morphology were grown under high pressure using sodium hydroxide (NaOH) and potassium hydroxide (KOH) with a molar ratio of 1:1 as a flux. The growth mechanism of Cu 2 O polyhedral microcrystals are proposed and discussed. - Graphical Abstract: The Cu 2 O crystals with truncated octahedral shape were one-step synthesized in high yield via high pressure flux method for the first time, which is green and environmentally friendly. The mechanisms of synthesis and crystal growth were discussed in this paper. Highlights: → Cuprous oxide was one-step green synthesized by high pressure flux method. → The approach was based on the reverse dismutation reactions between cupric oxide and copper metal. → This progress is green, environmentally friendly and energy efficient. → The synthesized Cu2O crystals were of truncated octahedra morphology.

  9. Compositional Tuning, Crystal Growth, and Magnetic Properties of Iron Phosphate Oxide

    Science.gov (United States)

    Tarne, Michael

    Iron phosphate oxide, Fe3PO4O 3, is a crystalline solid featuring magnetic Fe3+ ions on a complex lattice composed of closely-spaced triangles. Previous work from our research group on this compound has proposed a helical magnetic structure below T = 163 K attributed to J1 - J2 competing interactions between nearest-neighbor and next-nearest-neighbor iron atoms. This was based on neutron powder diffraction featuring unique broad, flat-topped magnetic reflections due to needle-like magnetic domains. In order to confirm the magnetic structure and origins of frustration, this thesis will expand upon the research focused on this compound. The first chapter focuses on single crystal growth of Fe3PO 4O3. While neutron powder diffraction provides insight to the magnetic structure, powder and domain averaging obfuscate a conclusive structure for Fe3PO4O3 and single crystal neutron scattering is necessary. Due to the incongruency of melting, single crystal growth has proven challenging. A number of techniques including flux growth, slow cooling, and optical floating zone growth were attempted and success has been achieved via heterogenous chemical vapor transport from FePO 4 using ZrCl4 as a transport agent. These crystals are of sufficient size for single crystal measurements on modern neutron diffractometers. Dilution of the magnetic sublattice in frustrated magnets can also provide insight into the nature of competing spin interactions. Dilution of the Fe 3+ lattice in Fe3PO4O3 is accomplished by substituting non-magnetic Ga3+ to form the solid solution series Fe3-xGaxPO4O3 with x = 0, 0.012, 0.06, 0.25, 0.5, 1.0, 1.5. The magnetic susceptibility and neutron powder diffraction data of these compounds are presented. A dramatic decrease of the both the helical pitch length and the domain size is observed with increasing x; for x > 0.5, the compounds lack long range magnetic order. The phases that do exhibit magnetic order show a decrease in helical pitch with increasing x

  10. A framework for analysing relationships between chemical composition and crystal structure in metal oxides

    International Nuclear Information System (INIS)

    Thomas, N.W.

    1991-01-01

    A computer program has been written to characterize the coordination polyhedra of metal cations in terms of their volumes and polyhedral elements, i.e. corners, edges and faces. The sharing of these corners, edges and faces between polyhedra is also quantitatively monitored. In order to develop the methodology, attention is focused on ternary oxides containing the Al 3+ ion, whose structures were retrieved from the Inorganic Crystal Structure Database (ICSD). This also permits an objective assessment of the applicability of Pauling's rules. The influence of ionic valence on the structures of these compounds is examined, by calculating electrostatic bond strengths. Although Pauling's second rule is not supported in detail, the calculation of oxygen-ion valence reveals a basic structural requirement, that the average calculated oxygen-ion valence in any ionic oxide structure is equal to 2. The analysis is further developed to define a general method for the prediction of novel chemical compositions likely to adopt a given desired structure. The polyhedral volumes of this structure are calculated, and use is made of standard ionic radii for cations in sixfold coordination. The electroneutrality principle is invoked to take valence considerations into account. This method can be used to guide the development of new compositions of ceramic materials with certain desirable physical properties. (orig.)

  11. Optical and luminescence properties of zinc oxide (Review)

    Science.gov (United States)

    Rodnyi, P. A.; Khodyuk, I. V.

    2011-11-01

    We generalize and systematize basic experimental data on optical and luminescence properties of ZnO single crystals, thin films, powders, ceramics, and nanocrystals. We consider and study mechanisms by which two main emission bands occur, a short-wavelength band near the fundamental absorption edge and a broad long-wavelength band, the maximum of which usually lies in the green spectral range. We determine a relationship between the two luminescence bands and study in detail the possibility of controlling the characteristics of ZnO by varying the maximum position of the short-wavelength band. We show that the optical and luminescence characteristics of ZnO largely depend on the choice of the corresponding impurity and the parameters of the synthesis and subsequent treatment of the sample. Prospects for using zinc oxide as a scintillator material are discussed. Additionally, we consider experimental results that are of principal interest for practice.

  12. Group one impurities in single crystalline Zinc Oxide

    OpenAIRE

    Johansen, Klaus Magnus Håland

    2011-01-01

    Zinc Oxide (ZnO) has been used as a material in many different technologies from pharmaceuticals to electronics. This exciting material can also be utilized as a wide band gap semiconductor for application in optoelectronic devices. The availability of Zn, the possibility to grow single crystal bulk material and the exitonic binding energy of 60 meV makes this material especially interesting. Even though the material has been studied already since the late 1920s there are still some fundament...

  13. Synthesis and Characterization of ZNO/MN Nanocomposite by using Sol-Gel Method

    Science.gov (United States)

    Ningsih, S. K. W.; Bahrizal, B.; Nasra, E.; Nizar, U. K.; Farisya, R.

    2018-04-01

    Zink oxide doped Mn nanocomposites were synthesized by simple sol-gel method at low temperature by using combination of aquadest with methanol as the solvent and ethylene glycol as the additive. Zink acetate dehydrate and manganese chloride tetrahydrate were used as the precursors. Composition dopants were 1,3,5,and 7%. The crystals were formed by drying at 110°C for 1 hour, after which they were heated at ± 500°C for 2 hours. The as-prepared ZnO/Mn nanocomposites were characterized by X-ray diffraction (XRD) and UV Diffuse Reflectance Spectrometer (UVDRS). The XRD patterns of the ZnO nanocrystals showed that they are mostly hexagonal wurtzite with specific peaks at 2θ = 31, 34, 36, 47, 56, 63, 66 dan 69. The sizes of the ZnO doped Mn particles produced with 1%, 3%, 5% and 7% were18-95; 17-87; 18-96 19-98 nm, respectively. UVDRS analysis showed that the band gap of the ZnO were 2,60; 2,90; 2,99 dan 3,01 eV for 1%, 3%, 5% and 7% Mn respectively.

  14. Simulation of pure and defective wurtzite-type ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Maldonado, Frank; Stashans, Arvids [Grupo de FisicoquImica de Materiales, Instituto de Quimica Aplicada, Universidad Tecnica Particular de Loja, Apartado 11-01-608, Loja (Ecuador)], E-mail: arvids@utpl.edu.ec

    2009-12-15

    Changes in the structural and electronic properties of zinc oxide (ZnO) due to the O vacancy and F-centre were studied using a semi-empirical quantum-chemical approach based on Hartree-Fock theory. A periodic supercell of 128 atoms was exploited throughout the study. The semi-empirical parameters for the Zn atom are obtained by reproducing the main properties of the ZnO crystal as well as the first three ionization potentials of the Zn atom. The perturbation imposed by the defect leads to atomic relaxation, which is computed and discussed in detail. It is found that electron density redistribution in the vicinity of defects plays an important role in the determination of atomic movements. The introduction of an oxygen vacancy generates a local one-electron energy level placed below the conduction band while the presence of an F-centre produces a local energy level just above the upper valence band of the material. The deep situation of the local energy level corresponding to the F-centre implies that the F-centre cannot serve as a source of unintentional n-type electrical conductivity in ZnO. Changes in the chemical bonding are observed, showing that it becomes slightly more covalent because of oxygen-vacancy-type defects.

  15. Simulation of pure and defective wurtzite-type ZnO

    International Nuclear Information System (INIS)

    Maldonado, Frank; Stashans, Arvids

    2009-01-01

    Changes in the structural and electronic properties of zinc oxide (ZnO) due to the O vacancy and F-centre were studied using a semi-empirical quantum-chemical approach based on Hartree-Fock theory. A periodic supercell of 128 atoms was exploited throughout the study. The semi-empirical parameters for the Zn atom are obtained by reproducing the main properties of the ZnO crystal as well as the first three ionization potentials of the Zn atom. The perturbation imposed by the defect leads to atomic relaxation, which is computed and discussed in detail. It is found that electron density redistribution in the vicinity of defects plays an important role in the determination of atomic movements. The introduction of an oxygen vacancy generates a local one-electron energy level placed below the conduction band while the presence of an F-centre produces a local energy level just above the upper valence band of the material. The deep situation of the local energy level corresponding to the F-centre implies that the F-centre cannot serve as a source of unintentional n-type electrical conductivity in ZnO. Changes in the chemical bonding are observed, showing that it becomes slightly more covalent because of oxygen-vacancy-type defects.

  16. Photocatalysis and Bandgap Engineering Using ZnO Nanocomposites

    Directory of Open Access Journals (Sweden)

    Muhammad Ali Johar

    2015-01-01

    Full Text Available Nanocomposites have a great potential to work as efficient, multifunctional materials for energy conversion and photoelectrochemical reactions. Nanocomposites may reveal more improved photocatalysis by implying the improvements of their electronic and structural properties than pure photocatalyst. This paper presents the recent work carried out on photoelectrochemical reactions using the composite materials of ZnO with CdS, ZnO with SnO2, ZnO with TiO2, ZnO with Ag2S, and ZnO with graphene and graphene oxide. The photocatalytic efficiency mainly depends upon the light harvesting span of a material, lifetime of photogenerated electron-hole pair, and reactive sites available in the photocatalyst. We reviewed the UV-Vis absorption spectrum of nanocomposite and photodegradation reported by the same material and how photodegradation depends upon the factors described above. Finally the improvement in the absorption band edge of nanocomposite material is discussed.

  17. Fabrication of Well-Aligned ZnO Nanorods Using a Composite Seed Layer of ZnO Nanoparticles and Chitosan Polymer.

    Science.gov (United States)

    Khun, Kimleang; Ibupoto, Zafar Hussain; AlSalhi, Mohamad S; Atif, Muhammad; Ansari, Anees A; Willander, Magnus

    2013-09-30

    In this study, by taking the advantage of both inorganic ZnO nanoparticles and the organic material chitosan as a composite seed layer, we have fabricated well-aligned ZnO nanorods on a gold-coated glass substrate using the hydrothermal growth method. The ZnO nanoparticles were characterized by the Raman spectroscopic techniques, which showed the nanocrystalline phase of the ZnO nanoparticles. Different composites of ZnO nanoparticles and chitosan were prepared and used as a seed layer for the fabrication of well-aligned ZnO nanorods. Field emission scanning electron microscopy, energy dispersive X-ray, high-resolution transmission electron microscopy, X-ray diffraction, and infrared reflection absorption spectroscopic techniques were utilized for the structural characterization of the ZnO nanoparticles/chitosan seed layer-coated ZnO nanorods on a gold-coated glass substrate. This study has shown that the ZnO nanorods are well-aligned, uniform, and dense, exhibit the wurtzite hexagonal structure, and are perpendicularly oriented to the substrate. Moreover, the ZnO nanorods are only composed of Zn and O atoms. An optical study was also carried out for the ZnO nanoparticles/chitosan seed layer-coated ZnO nanorods, and the obtained results have shown that the fabricated ZnO nanorods exhibit good crystal quality. This study has provided a cheap fabrication method for the controlled morphology and good alignment of ZnO nanorods, which is of high demand for enhancing the working performance of optoelectronic devices.

  18. Fabrication of Well-Aligned ZnO Nanorods Using a Composite Seed Layer of ZnO Nanoparticles and Chitosan Polymer

    Directory of Open Access Journals (Sweden)

    Anees A. Ansari

    2013-09-01

    Full Text Available In this study, by taking the advantage of both inorganic ZnO nanoparticles and the organic material chitosan as a composite seed layer, we have fabricated well-aligned ZnO nanorods on a gold-coated glass substrate using the hydrothermal growth method. The ZnO nanoparticles were characterized by the Raman spectroscopic techniques, which showed the nanocrystalline phase of the ZnO nanoparticles. Different composites of ZnO nanoparticles and chitosan were prepared and used as a seed layer for the fabrication of well-aligned ZnO nanorods. Field emission scanning electron microscopy, energy dispersive X-ray, high-resolution transmission electron microscopy, X-ray diffraction, and infrared reflection absorption spectroscopic techniques were utilized for the structural characterization of the ZnO nanoparticles/chitosan seed layer-coated ZnO nanorods on a gold-coated glass substrate. This study has shown that the ZnO nanorods are well-aligned, uniform, and dense, exhibit the wurtzite hexagonal structure, and are perpendicularly oriented to the substrate. Moreover, the ZnO nanorods are only composed of Zn and O atoms. An optical study was also carried out for the ZnO nanoparticles/chitosan seed layer-coated ZnO nanorods, and the obtained results have shown that the fabricated ZnO nanorods exhibit good crystal quality. This study has provided a cheap fabrication method for the controlled morphology and good alignment of ZnO nanorods, which is of high demand for enhancing the working performance of optoelectronic devices.

  19. Anodized ZnO nanostructures for photoelectrochemical water splitting

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Mao-Chia [Institute of Materials Science and Engineering, National Central University, Taoyuan 32001, Taiwan (China); Wang, TsingHai [Department of Biomedical Engineering and Environment Sciences, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Wu, Bin-Jui [Institute of Materials Science and Engineering, National Central University, Taoyuan 32001, Taiwan (China); Lin, Jing-Chie, E-mail: jclin4046@gmail.com [Institute of Materials Science and Engineering, National Central University, Taoyuan 32001, Taiwan (China); Wu, Ching-Chen [Green Energy and Environment Research Laboratories, Industrial Technology Research Institute, Hsinchu 310, Taiwan (China)

    2016-01-01

    Highlights: • ZnO nanostructures were synthesized by electrochemical anodic process. • The parameter of ZnO nanostructure was anodic potential. • The model of growth of ZnO nanostructure was investigated. - Abstract: Zinc oxide (ZnO) nanostructures were fabricated on the polished zinc foil by anodic deposition in an alkaline solution containing 1.0 M NaOH and 0.25 M Zn(NO{sub 3}){sub 2}. Potentiostatic anodization was conducted at two potentials (−0.7 V in the passive region and −1.0 V in the active region vs. SCE) which are higher than the open circuit potential (−1.03 V vs. SCE) and as-obtained ZnO nanostrcutures were investigated focusing on their structural, optical, electrical and photoelectrochemical (PEC) characteristics. All samples were confirmed ZnO by X-ray photoelectron spectroscopy and Raman spectra. Observations in the SEM images clearly showed that ZnO nanostructures prepared at −0.7 V vs. SCE were composed of nanowires at while those obtained at −1.0 V vs. SCE possessed nanosheets morphology. Result from transmission electron microscope and X-ray diffraction patterns suggested that the ZnO nanowires belonged to single crystalline with a preferred orientation of (0 0 2) whereas the ZnO nanosheets were polycrystalline. Following PEC experiments indicated that ZnO nanowires had higher photocurrent density of 0.32 mA/cm{sup 2} at 0.5 V vs. SCE under 100 mW/cm{sup 2} illumination. This value was about 1.9 times higher than that of ZnO nanosheets. Observed higher photocurrent was likely due to the single crystalline, preferred (0 0 2) orientation, higher carrier concentration and lower charge transfer resistance.

  20. Trioctylphosphine-assisted morphology control of ZnO nanoparticles

    Science.gov (United States)

    Hong, Yun-Kun; Cho, GeonHee; Park, YoonSu; Oh, Soong Ju; Ha, Don-Hyung

    2018-06-01

    This study investigates the morphological change in colloidal ZnO nanoparticles (NPs) synthesized with trioctylphosphine (TOP). The addition of TOP to the synthesis causes an evolution in the shape of ZnO NPs to tadpole-like particles from quasi-spherical particles at 300 °C. The total length of the tadpole-like ZnO NPs can be modified by controlling the molar ratio of TOP to oleylamine (OLAM). The tadpole-like particles are elongated as the concentration of TOP increased but decreased when the addition of TOP is excessive. These tadpole-like ZnO NPs transform to quasi-spherical NPs regardless of the amount of TOP at a reaction time of 3 h at 300 °C. At 200 °C, the effect of TOP on the ZnO NP synthesis differs from that at 300 °C. The ZnO NPs synthesized by controlling the molar ratios of surfactant ligands (TOP:OLAM = 2:100 and 70:100) at 200 °C share similar amorphous structures, while a crystalline ZnO phase is formed when the reaction time is 3 h. X-ray photoelectron spectroscopy analysis shows that TOP influences the oxidation of ZnO and suggests that a combination of OLAM and TOP plays a role in controlling the shape of ZnO NPs. These results provide critical insights to the utilization of TOP for a shape controlling ligand in ZnO NPs and suggest a new route to design oxide NPs.

  1. Electrical characterization of ZnO nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Schlenker, E.; Bakin, A.; Postels, B.; Mofor, A.C.; Wehmann, H.H.; Waag, A. [Institute of Semiconductor Technology, Technical University Braunschweig, Hans-Sommer-Strasse 66, 38106 Braunschweig (Germany); Weimann, T.; Hinze, P. [Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig (Germany)

    2007-05-15

    Zinc oxide (ZnO) nanorods were grown by a wet chemical approach and by vapor phase transport. To explore the electrical properties of individual nanostructures current-voltage (I-V) characteristics were obtained by using an atomic force microscope (AFM) with a conductive tip or by detaching the nanorods from the growth substrate, transferring them to an isolating substrate and contacting them with evaporated Ti/Au electrodes patterned by electron-beam lithography. The AFM-approach only yields a Schottky diode behavior, while the Ti/Au forms ohmic contacts to the ZnO. For the latter method the obtained I-V curves reveal a resistivity of the nanorods in the order of 10{sup -5} {omega} cm which is unusually low for undoped ZnO. We therefore assume the existence of a highly conductive surface channel. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Simple Response Surface Methodology: Investigation on Advance Photocatalytic Oxidation of 4-Chlorophenoxyacetic Acid Using UV-Active ZnO Photocatalyst.

    Science.gov (United States)

    Lee, Kian Mun; Hamid, Sharifah Bee Abd

    2015-01-19

    The performance of advance photocatalytic degradation of 4-chlorophenoxyacetic acid (4-CPA) strongly depends on photocatalyst dosage, initial concentration and initial pH. In the present study, a simple response surface methodology (RSM) was applied to investigate the interaction between these three independent factors. Thus, the photocatalytic degradation of 4-CPA in aqueous medium assisted by ultraviolet-active ZnO photocatalyst was systematically investigated. This study aims to determine the optimum processing parameters to maximize 4-CPA degradation. Based on the results obtained, it was found that a maximum of 91% of 4-CPA was successfully degraded under optimal conditions (0.02 g ZnO dosage, 20.00 mg/L of 4-CPA and pH 7.71). All the experimental data showed good agreement with the predicted results obtained from statistical analysis.

  3. Photoluminescent ZnO Nanoparticles and Their Biological Applications

    Directory of Open Access Journals (Sweden)

    Zheng-Yong Zhang

    2015-05-01

    Full Text Available During the past decades, numerous achievements concerning luminescent zinc oxide nanoparticles (ZnO NPs have been reported due to their improved luminescence and good biocompatibility. The photoluminescence of ZnO NPs usually contains two parts, the exciton-related ultraviolet (UV emission and the defect-related visible emission. With respect to the visible emission, many routes have been developed to synthesize and functionalize ZnO NPs for the applications in detecting metal ions and biomolecules, biological fluorescence imaging, nonlinear multiphoton imaging, and fluorescence lifetime imaging. As the biological applications of ZnO NPs develop rapidly, the toxicity of ZnO NPs has attracted more and more attention because ZnO can produce the reactive oxygen species (ROS and release Zn2+ ions. Just as a coin has two sides, both the drug delivery and the antibacterial effects of ZnO NPs become attractive at the same time. Hence, in this review, we will focus on the progress in the synthetic methods, luminescent properties, and biological applications of ZnO NPs.

  4. Study of the effect of ZnO film on some properties of clear and color window glass

    Science.gov (United States)

    Hamead, Alaa A. Abdul; Ahmed, Sura S.; Khdheer, Mena F.

    2018-05-01

    In the current research, a samples of transparent color and colorless window glass were prepared, (includes metal transition oxides) for construction applications. A nano-film layer of zinc oxide ZnO was deposited by spray pyrolysis technique for use in sustainability applications prepared. Structural properties (x-ray diffraction XRD, scanning electron microscopy SEM and atomic force microscopy AFM), and thermal properties, as well as optical properties and the effect of weathering conditions on applied film on clear and colored glass were examined. The results showed that the deposition film had a thickness of less than 90nm and that it was crystallized with high optical transparently, that was not significantly affected after deposited the ZnO nano film. While thermal insulation decreased significantly after deposition, and the effect of the weather conditions was very low as the ZnO coating was not affected, as the thermal insulation did not change after exposure to accelerated air conditions. Make it suitable in glass applications for buildings in vertical construction.

  5. Application of zinc oxide quantum dots in food safety

    Science.gov (United States)

    Zinc oxide quantum dots (ZnO QDs) are nanoparticles of purified powdered ZnO. The ZnO QDs were directly added into liquid foods or coated on the surface of glass jars using polylactic acid (PLA) as a carrier. The antimicrobial activities of ZnO QDs against Listeria monocytogenes, Salmonella Enteriti...

  6. Performance of Cr-doped ZnO for acetone sensing

    Energy Technology Data Exchange (ETDEWEB)

    Al-Hardan, N.H., E-mail: naif_imen@ukm.my [Institute of Microengineering and Nanoelectronics (IMEN), Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Abdullah, M.J.; Aziz, A. Abdul [School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia)

    2013-04-01

    Zinc oxide (ZnO) doped with chromium (Cr) was synthesized by reactive co-sputtering for gas sensing applications. The effect of varying the contents of Cr (from 1 to 4 at%) on the ZnO gas sensor response was studied. X-ray diffraction analysis reveals the high orientation of c-axis of the prepared films. The optimum operating temperature of the undoped ZnO was 400 °C and shifted to 300 °C for the Cr-doped ZnO under the acetone vapour. The 1% Cr doping ZnO gas sensor was most sensitive for the acetone vapour. The ability of the 1% Cr-doped ZnO to produce repeatable results under different acetone vapour concentrations was tested. The timing properties of the doped Cr ZnO gas sensor were 70 and 95 s for the rise and recovery time respectively.

  7. Controllable synthesis of periodic flower-like ZnO nanostructures on Si subwavelength grating structures

    International Nuclear Information System (INIS)

    Ko, Yeong Hwan; Leem, Jung Woo; Yu, Jae Su

    2011-01-01

    We report on the periodic well-defined flower-like zinc oxide (ZnO) nanostructures (NSs) self-assembled through a simple hydrothermal method using silicon (Si) subwavelength grating (SWG) structures. The Si SWGs serve as building blocks for constructing a two-dimensional (2D) periodic architecture to integrate the one-dimensional (1D) ZnO NSs. Various controlled morphologies of ZnO NSs with high crystallinity are obtained by changing the growth conditions. For 1D ZnO NSs integrated on periodic hexagonal Si SWG structures, the reflection characteristics are investigated in comparison with the conventional ZnO nanorod (NR) arrays. For a three-dimensional (3D) flower-like ZnO NS on Si SWGs, a relatively low total reflectance of < 8% at wavelengths of 300-1050 nm is achieved compared to the ZnO NRs on Si substrate.

  8. The Mobility Enhancement of Indium Gallium Zinc Oxide Transistors via Low-temperature Crystallization using a Tantalum Catalytic Layer.

    Science.gov (United States)

    Shin, Yeonwoo; Kim, Sang Tae; Kim, Kuntae; Kim, Mi Young; Oh, Saeroonter; Jeong, Jae Kyeong

    2017-09-07

    High-mobility indium gallium zinc oxide (IGZO) thin-film transistors (TFTs) are achieved through low-temperature crystallization enabled via a reaction with a transition metal catalytic layer. For conventional amorphous IGZO TFTs, the active layer crystallizes at thermal annealing temperatures of 600 °C or higher, which is not suitable for displays using a glass substrate. The crystallization temperature is reduced when in contact with a Ta layer, where partial crystallization at the IGZO back-channel occurs with annealing at 300 °C, while complete crystallization of the active layer occurs at 400 °C. The field-effect mobility is significantly boosted to 54.0 cm 2 /V·s for the IGZO device with a metal-induced polycrystalline channel formed at 300 °C compared to 18.1 cm 2 /V·s for an amorphous IGZO TFT without a catalytic layer. This work proposes a facile and effective route to enhance device performance by crystallizing the IGZO layer with standard annealing temperatures, without the introduction of expensive laser irradiation processes.

  9. Flame synthesis of zinc oxide nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Merchan-Merchan, Wilson, E-mail: wmerchan-merchan@ou.edu [School of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK 73019 (United States); Farahani, Moien Farmahini [School of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK 73019 (United States)

    2013-02-01

    Highlights: Black-Right-Pointing-Pointer We report a single-step flame method for the synthesis of Zn oxide nanocrystals. Black-Right-Pointing-Pointer Diverse flame positions lead to a variation of Zn oxide nanocrystal growth. Black-Right-Pointing-Pointer The synthesized crystals have polyhedral, pipet- and needle-like shape. Black-Right-Pointing-Pointer High length-to-diameter aspect-ratio crystals appear in a higher temperature flame. Black-Right-Pointing-Pointer The crystal growth mechanism corresponds to vapor-to-solid conversion. - Abstract: Distinctive zinc oxide (ZnO) nanocrystals were synthesized on the surface of Zn probes using a counter-flow flame medium formed by methane/acetylene and oxygen-enriched air streams. The source material, a zinc wire with a purity of {approx}99.99% and diameter of 1 mm, was introduced through a sleeve into the oxygen rich region of the flame. The position of the probe/sleeve was varied within the flame medium resulting in growth variation of ZnO nanocrystals on the surface of the probe. The shape and structural parameters of the grown crystals strongly depend on the flame position. Structural variations of the synthesized crystals include single-crystalline ZnO nanorods and microprisms (ZMPs) (the ZMPs have less than a few micrometers in length and several hundred nanometers in cross section) with a large number of facets and complex axial symmetry with a nanorod protruding from their tips. The protruding rods are less than 100 nm in diameter and lengths are less than 1 {mu}m. The protruding nanorods can be elongated several times by increasing the residence time of the probe/sleeve inside the oxygen-rich flame or by varying the flame position. At different flame heights, nanorods having higher length-to-diameter aspect-ratio can be synthesized. A lattice spacing of {approx}0.26 nm was measured for the synthesized nanorods, which can be closely correlated with the (0 0 2) interplanar spacing of hexagonal ZnO (Wurtzite) cells

  10. Molecular-level chemistry of model single-crystal oxide surfaces with model halogenated compounds

    Science.gov (United States)

    Adib, Kaveh

    Synchrotron-based X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption (TPD) and low energy electron diffraction (LEED) have been used to investigate, at a molecular level, the chemistry of different terminations of single crystal iron-oxide surfaces with probe molecules (CCl4 and D2O). Comparisons of the reactivity of these surfaces towards CCl4, indicate that the presence of an uncapped surface Fe cation (strong Lewis acid site) and an adjacent oxygen site capped by that cation can effect the C-Cl bond cleavage in CCl4, resulting in dissociatively adsorbed Cl-adatoms and carbon-containing fragments. If in addition to these sites, an uncapped surface oxygen (Lewis base) site is also available, the carbon-containing moiety can then move that site, coordinate itself with that uncapped oxygen, and stabilize itself. At a later step, the carbon-containing fragment may form a strong covalent bond with the uncapped oxygen and may even abstract that surface oxygen. On the other hand, if an uncapped oxygen is not available to stabilize the carbon-containing fragment, the surface coordination will not occur and upon the subsequent thermal annealing of the surface the Cl-adatoms and the carbon-containing fragments will recombine and desorb as CCl4. Finally, the presence of surface deuteroxyls blocking the strong Lewis acid and base sites of the reactive surface, passivates this surface. Such a deuteroxylated surface will be unreactive towards CCl 4. Such a molecular level understanding of the surface chemistry of metal-oxides will have applications in the areas of selective catalysis, including environmental catalysis, and chemical sensor technology.

  11. Hierarchical structures of ZnO spherical particles synthesized solvothermally

    Science.gov (United States)

    Saito, Noriko; Haneda, Hajime

    2011-12-01

    We review the solvothermal synthesis, using a mixture of ethylene glycol (EG) and water as the solvent, of zinc oxide (ZnO) particles having spherical and flower-like shapes and hierarchical nanostructures. The preparation conditions of the ZnO particles and the microscopic characterization of the morphology are summarized. We found the following three effects of the ratio of EG to water on the formation of hierarchical structures: (i) EG restricts the growth of ZnO microcrystals, (ii) EG promotes the self-assembly of small crystallites into spheroidal particles and (iii) the high water content of EG results in hollow spheres.

  12. Photonic Crystals: Tunable Design of Structural Colors Produced by Pseudo-1D Photonic Crystals of Graphene Oxide (Small 25/2016).

    Science.gov (United States)

    Tong, Liping; Qi, Wei; Wang, Mengfan; Huang, Renliang; Su, Rongxin; He, Zhimin

    2016-07-01

    The production of structural colors based on graphene oxide (GO) pseudo-one-dimensional photonic crystals (p1D-PhCs) in the visible spectrum is reported on page 3433 by W. Qi and co-workers. The structural colors could be tuned by simply changing either the volume or concentration of the aqueous GO dispersion. Moreover, GO p1D-PhCs exhibit visible and rapid responsiveness to humidity. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Enhanced antimicrobial activity in biosynthesized ZnO nanoparticles

    Science.gov (United States)

    Kumari, Niraj; Kumari, Priti; Jha, Anal K.; Prasad, K.

    2018-05-01

    Biological synthesis of different metallic and/or oxide nanoparticles and their applications especially in agriculture and biomedical sciences are gaining prominence nowadays due to their handy and reproducible synthetic protocols which are cost-effective and eco-friendly. In this work, green synthesis of zinc oxide nanoparticles (ZnO NPs) using the alcoholic extract of Azadirachta indica as a reducing and stabilizing agent has been presented. Formation of ZnO NPs was confirmed by X-ray diffraction, scanning and transmission electron microscopy techniques. The phytochemicals responsible for nano-transformation were principally alkaloids, flavanoids, terpenoids, tannins and organic acids present in the Azadirachta indica leaves. The synthesized ZnO NPs were used for antimicrobial assays by disc diffusion method against Staphylococcus aureus and Candida albicans. Results showed that ZnO NPs may act as antimicrobial agent especially against skin infections.

  14. Laser-induced grating in ZnO

    DEFF Research Database (Denmark)

    Ravn, Jesper N.

    1992-01-01

    A simple approach for the calculation of self-diffraction in a thin combined phase and amplitude grating is presented. The third order nonlinearity, the electron-hole recombination time, and the ambipolar diffusion coefficient in a ZnO crystal are measured by means of laser-induced self-diffracti......A simple approach for the calculation of self-diffraction in a thin combined phase and amplitude grating is presented. The third order nonlinearity, the electron-hole recombination time, and the ambipolar diffusion coefficient in a ZnO crystal are measured by means of laser-induced self...

  15. Al-doped ZnO seed layer-dependent crystallographic control of ZnO nanorods by using electrochemical deposition

    Energy Technology Data Exchange (ETDEWEB)

    Son, Hyo-Soo; Choi, Nak-Jung [Department of Nano-Optical Engineering, Korea Polytechnic University, Siheung 429-793 (Korea, Republic of); Kim, Kyoung-Bo [Department of Metallurgical and Materials Engineering, Inha Technical College, Incheon 402-752 (Korea, Republic of); Kim, Moojin [Department of Renewable Energy, Jungwon University, Goesan-gun, Chungbuk 367-805 (Korea, Republic of); Lee, Sung-Nam, E-mail: snlee@kpu.ac.kr [Department of Nano-Optical Engineering, Korea Polytechnic University, Siheung 429-793 (Korea, Republic of)

    2016-10-15

    Highlights: • Polar and semipolar ZnO NRs were successfully achieved by hydrothermal synthesis. • Semipolar and polar ZnO NRs were grown on ZnO and AZO/m-sapphire, respectively. • Al % of AZO/m-sapphire enhanced the lateral growth rate of polar ZnO NRs. - Abstract: We investigated the effect of an Al-doped ZnO film on the crystallographic direction of ZnO nanorods (NRs) using electrochemical deposition. From high-solution X-ray diffraction measurements, the crystallographic plane of ZnO NRs grown on (1 0 0) ZnO/m-plane sapphire was (1 0 1). The surface grain size of the (100) Al-doped ZnO (AZO) film decreased with increasing Al content in the ZnO seed layer, implying that the Al dopant accelerated the three-dimensional (3D) growth of the AZO film. In addition, it was found that with increasing Al doping concentration of the AZO seed layer, the crystal orientation of the ZnO NRs grown on the AZO seed layer changed from [1 0 1] to [0 0 1]. With increasing Al content of the nonpolar (1 0 0) AZO seed layer, the small surface grains with a few crystallographic planes of the AZO film changed from semipolar (1 0 1) ZnO NRs to polar (0 0 1) ZnO NRs due to the increase of the vertical [0 0 1] growth rate of the ZnO NRs owing to excellent electrical properties.

  16. Effect of growth temperature on photoluminescence and piezoelectric characteristics of ZnO nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Water, Walter [Institute of Electro-Optical and Materials Science, National Formosa University, Yunlin 632, Taiwan (China); Fang, T.-H. [Institute of Electro-Optical and Materials Science, National Formosa University, Yunlin 632, Taiwan (China); Institute of Mechanical and Electromechanical Engineering, National Formosa University, Yunlin 632, Taiwan (China)], E-mail: fang.tehua@msa.hinet.net; Ji, L.-W.; Lee, C.-C. [Institute of Electro-Optical and Materials Science, National Formosa University, Yunlin 632, Taiwan (China)

    2009-02-25

    ZnO nanowire arrays were synthesized on Au-coated silicon (1 0 0) substrates by using vapour-liquid-solid process in this work. The effect of growth temperatures on the crystal structure and the surface morphology of ZnO nanowires were investigated by X-ray diffraction and scanning electron microscope. The absorption and optical characteristics of the nanowires were examined by Ultraviolet/Visible spectroscopy, and photoluminescence, respectively. The photoluminescence results exhibited ZnO nanowires had an ultraviolet and blue emission at 383 and 492 nm. Then a nanogenerator with ZnO nanowire arrays was fabricated and demonstrated Schottky-like current-voltage characteristics.

  17. Selective growth of ZnO thin film nanostructures: Structure, morphology and tunable optical properties

    Energy Technology Data Exchange (ETDEWEB)

    Krishnakanth, Katturi Naga; Sunandana, C. S. [School of Physics, University of Hyderabad, Hyderabad-50046 (India); Rajesh, Desapogu, E-mail: rajesh.esapogu@gmail.com, E-mail: mperd@nus.edu.sg [School of Physics, University of Hyderabad, Hyderabad-50046 (India); Dept. of Mechanical Engineering, National University of Singapore (Singapore)

    2016-05-23

    The ZnO nanostructures (spherical, rod shape) have been successfully fabricated via a thermal evaporation followed by dip coating method. The pure, doped ZnO thin films were characterized by X-ray powder diffraction (XRD) and field emission scanning electron microscopy (FESEM) and UV-Vis spectroscopy, respectively. A possible growth mechanism of the spherical, rod shape ZnO nanostructures are discussed. XRD patterns revealed that all films consist of pure ZnO phase and were well crystallized with preferential orientation towards (002) direction. Doping by PVA, PVA+Cu has effective role in the enhancement of the crystalline quality and increases in the band gap.

  18. Mid-temperature deep removal of hydrogen sulfide on rare earth (RE = Ce, La, Sm, Gd) doped ZnO supported on KIT-6: Effect of RE dopants and interaction between active phase and support matrix

    Energy Technology Data Exchange (ETDEWEB)

    Li, Lu; Zhou, Pin; Zhang, Hongbo; Meng, Xianglong; Li, Juexiu; Sun, Tonghua, E-mail: sunth@sjtu.edu.cn

    2017-06-15

    Highlights: • Various rare earth (RE)-doped ZnO/KIT-6 sorbents were prepared via sol-gel method. • La showed the highest efficiency on promoting ZnO/KIT-6 desulfurization activity. • The morphology of ZnO on KIT-6 played a crucial role for the reactivity. • The most initial factor of improving reactivity by RE was surface chemical property. • Crystallinity, host-guest interaction were also important to ZnO state on support. - Abstract: Rare earth oxides (RE = Ce, La, Sm and Gd) doped ZnO supported on KIT-6 sorbents (RE-ZnO/KIT-6) were synthesized by sol-gel method and their performance for deep removal of H{sub 2}S (bellow 0.1 ppmv) from gas stream at medium temperature was tested. The RE dopants (except Ce) significantly enhance the deep desulfurization capacity of ZnO/KIT-6 sorbent and maintained higher sulfur uptake capacities upon multiple cycles of regeneration by a simple thermal oxidation in 10 v% of O{sub 2} in N{sub 2} atmosphere. The results of SAXS, XRD, N{sub 2} physisorption, TEM, FIIR, and XPS implied that the KIT-6 structure of loading metal oxides remained intact. It was found that RE could hinder the ZnO crystal ripening during calcination resulted in smaller ZnO particles, enhance the interaction of ZnO and silica matrix to improve the dispersion of active phase on KIT-6. Furthermore, by increasing the outlayer electron density of Zn atom and oxygen transfer ability, the synergistic effect considered to be favorable for RE-ZnO/KIT-6 sulfidation. Even though the performance of improving ZnO dispersion was weaker than that of Sm and Gd, La-ZnO/KIT-6 performs the best deep desulfurizers by changing the surface chemical atmosphere for ZnO. Steam in the gas stream inhibited the capture of H{sub 2}S by ZnO in the sorbents, in the case of La-ZnO/KIT-6, the steam content should control as lower as 5 v% to ensure the desulfurization efficiency and precision.

  19. Mid-temperature deep removal of hydrogen sulfide on rare earth (RE = Ce, La, Sm, Gd) doped ZnO supported on KIT-6: Effect of RE dopants and interaction between active phase and support matrix

    International Nuclear Information System (INIS)

    Li, Lu; Zhou, Pin; Zhang, Hongbo; Meng, Xianglong; Li, Juexiu; Sun, Tonghua

    2017-01-01

    Highlights: • Various rare earth (RE)-doped ZnO/KIT-6 sorbents were prepared via sol-gel method. • La showed the highest efficiency on promoting ZnO/KIT-6 desulfurization activity. • The morphology of ZnO on KIT-6 played a crucial role for the reactivity. • The most initial factor of improving reactivity by RE was surface chemical property. • Crystallinity, host-guest interaction were also important to ZnO state on support. - Abstract: Rare earth oxides (RE = Ce, La, Sm and Gd) doped ZnO supported on KIT-6 sorbents (RE-ZnO/KIT-6) were synthesized by sol-gel method and their performance for deep removal of H 2 S (bellow 0.1 ppmv) from gas stream at medium temperature was tested. The RE dopants (except Ce) significantly enhance the deep desulfurization capacity of ZnO/KIT-6 sorbent and maintained higher sulfur uptake capacities upon multiple cycles of regeneration by a simple thermal oxidation in 10 v% of O 2 in N 2 atmosphere. The results of SAXS, XRD, N 2 physisorption, TEM, FIIR, and XPS implied that the KIT-6 structure of loading metal oxides remained intact. It was found that RE could hinder the ZnO crystal ripening during calcination resulted in smaller ZnO particles, enhance the interaction of ZnO and silica matrix to improve the dispersion of active phase on KIT-6. Furthermore, by increasing the outlayer electron density of Zn atom and oxygen transfer ability, the synergistic effect considered to be favorable for RE-ZnO/KIT-6 sulfidation. Even though the performance of improving ZnO dispersion was weaker than that of Sm and Gd, La-ZnO/KIT-6 performs the best deep desulfurizers by changing the surface chemical atmosphere for ZnO. Steam in the gas stream inhibited the capture of H 2 S by ZnO in the sorbents, in the case of La-ZnO/KIT-6, the steam content should control as lower as 5 v% to ensure the desulfurization efficiency and precision.

  20. Study of quartz crystal microbalance NO2 sensor coated with sputtered indium tin oxide film

    Science.gov (United States)

    Georgieva, V.; Aleksandrova, M.; Stefanov, P.; Grechnikov, A.; Gadjanova, V.; Dilova, T.; Angelov, Ts

    2014-12-01

    A study of NO2 gas sorption ability of thin indium tin oxide (ITO) deposited on 16 MHz quartz crystal microbalance (QCM) is presented. ITO films are grown by RF sputtering of indium/tin target with weight proportion 95:5 in oxygen environment. The ITO films have been characterized by X-ray photoelectron spectroscopy measurements. The ITO surface composition in atomic % is defined to be: In-40.6%, Sn-4.3% and O-55%. The thickness and refractive index of the films are determined by ellipsometric method. The frequency shift of QCM-ITO is measured at different NO2 concentrations. The QCM-ITO system becomes sensitive at NO2 concentration >= 500 ppm. The sorbed mass for each concentration is calculated according the Sauerbrey equation. The results indicated that the 1.09 ng of the gas is sorbed into 150 nm thick ITO film at 500 ppm NO2 concentration. When the NO2 concentration increases 10 times the calculated loaded mass is 5.46 ng. The sorption process of the gas molecules is defined as reversible. The velocity of sorbtion /desorption processes are studied, too. The QCM coated with thin ITO films can be successfully used as gas sensors for detecting NO2 in the air at room temperature.

  1. Study of quartz crystal microbalance NO2 sensor coated with sputtered indium tin oxide film

    International Nuclear Information System (INIS)

    Georgieva, V; Gadjanova, V; Angelov, Ts; Aleksandrova, M; Acad. Georgi Bonchev str.bl. 11, 1113, Sofia (Bulgaria))" data-affiliation=" (Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. Georgi Bonchev str.bl. 11, 1113, Sofia (Bulgaria))" >Stefanov, P; Acad. Georgi Bonchev str.bl. 11, 1113, Sofia (Bulgaria))" data-affiliation=" (Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. Georgi Bonchev str.bl. 11, 1113, Sofia (Bulgaria))" >Dilova, T; Grechnikov, A

    2014-01-01

    A study of NO 2 gas sorption ability of thin indium tin oxide (ITO) deposited on 16 MHz quartz crystal microbalance (QCM) is presented. ITO films are grown by RF sputtering of indium/tin target with weight proportion 95:5 in oxygen environment. The ITO films have been characterized by X-ray photoelectron spectroscopy measurements. The ITO surface composition in atomic % is defined to be: In-40.6%, Sn-4.3% and O-55%. The thickness and refractive index of the films are determined by ellipsometric method. The frequency shift of QCM-ITO is measured at different NO 2 concentrations. The QCM-ITO system becomes sensitive at NO 2 concentration ≥ 500 ppm. The sorbed mass for each concentration is calculated according the Sauerbrey equation. The results indicated that the 1.09 ng of the gas is sorbed into 150 nm thick ITO film at 500 ppm NO 2 concentration. When the NO 2 concentration increases 10 times the calculated loaded mass is 5.46 ng. The sorption process of the gas molecules is defined as reversible. The velocity of sorbtion /desorption processes are studied, too. The QCM coated with thin ITO films can be successfully used as gas sensors for detecting NO 2 in the air at room temperature

  2. Modification of mechanical properties of single crystal aluminum oxide by ion beam induced structural changes

    International Nuclear Information System (INIS)

    Ensinger, W.; Nowak, R.; Horino, Y.; Baba, K.

    1993-01-01

    The mechanical behaviour of ceramics is essentially determined by their surface qualities. As a surface modification technique, ion implantation provides the possibility to modify the mechanical properties of ceramics. Highly energetic ions are implanted into the near-surface region of a material and modify its composition and structure. Ions of aluminum, oxygen, nickel and tantalum were implanted into single-crystal α-aluminum oxide. Three-point bending tests showed that an increase in flexural strength of up to 30% could be obtained after implantation of aluminum and oxygen. Nickel and tantalum ion implantation increased the fracture toughness. Indentation tests with Knoop and Vickers diamonds and comparison of the lengths of the developed radial cracks showed that ion implantation leads to a reaction in cracking. The observed effects are assigned to radiation induced structural changes of the ceramic. Ion bombardment leads to radiation damage and formation of compressive stress. In case of tantalum implantation, the implanted near-surface zone becomes amorphous. These effects make the ceramic more resistant to fracture. (orig.)

  3. Optimization of a Liquid Crystal-based Sensory Platform for Monitoring Enzymatic Glucose Oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Yibin; Jang, Chang-Hyun [Gachon University, Seongnam (Korea, Republic of)

    2016-05-15

    Managing glucose levels in human blood is extremely important for the treatment of diabetes. Here, an innovative sensory strategy has been developed to monitor the enzymatic activities of glucose and glucose oxidase by using confined liquid crystal (LC) birefringent droplet patterns. Acidic products released during the glucose oxidation process lead to a slight decrease in the pH of aqueous systems that can be monitored by pH-sensitive LC materials. Of the existing pH-sensitive LC materials, dodecanoic acid-doped 4-cyano-4'-pentylbiphenyl is inexpensive and easily adjusted to satisfy the 7.4 ± 0.05 pH requirement of human blood. Moreover, the orientational alignment of capillary-confined pH-responsive LCs can be disrupted at the aqueous/LC interface following a slight decrease in the critical pH of aqueous reaction systems, which results in an optical signal that can be observed with the naked eye by using polarizing optical microscopy. Based on the stable LC droplet patterns generated by the cylindrical confinement system, the functionalized LCs can selectively detect glucose at concentrations as low as 0.1 pM. This study further advances the previously reported LC-based glucose monitoring systems by reducing production costs and instituting a smarter LC sensory design. This improved system shows potential for the use in clinical bioassay applications.

  4. Structure and photoluminescence properties of Ag-coated ZnO nano-needles

    Energy Technology Data Exchange (ETDEWEB)

    Li Xiaozhu, E-mail: Lixiaozhu1019@21cn.com [Department of Physics, Shaoguan University, Shaoguan, Guangdong 512005 (China) and Department of Physics and Key Laboratory of Acoustic and Photonic Materials and Devices of Ministry of Education, Wuhan University, Wuhan, Hubei 430072 (China); Wang Yongqian [Engineering Research Center of Nano-Geomaterials of Ministry of Education (China University of Geosciences), Wuhan, Hubei 430074 (China)

    2011-05-12

    Highlights: > ZnO nano-needles were synthesized by thermal oxidation. > Their surfaces were coated with Ag by pulse electro-deposition technique. > The uncoated and coated ZnO nano-needles were characterized. > The results showed that the prepared ZnO nano-needles have been coated with Ag successfully. > The photoluminescence spectrums of ZnO nano-needles with Ag-coated and uncoated were analyzed, finding that the Ag-coated ZnO nano-needles can increase the absorption of UV light. - Abstract: A large number of zinc oxide (ZnO) nano-needles were synthesized by thermal oxidation of pure zinc. The surfaces of ZnO nano-needles were coated with a layer of Ag by pulse electro-deposition technique. The uncoated and coated ZnO nano-needles were characterized by using the X-ray diffraction and the scanning electron microscope (SEM). The results showed that the uncoated samples were close-packed hexagonal structure, which showed needle-like morphology. Their average diameter is about 40 nm, lengths up to 5 {mu}m. At the same time we observed that the prepared ZnO nano-needles have been coated with Ag successfully. The photoluminescence spectrums of ZnO nano-needles with Ag-coated and uncoated were analyzed, finding that the uncoated ZnO nano-needles have two fluorescence peaks at 388 nm and 470.8 nm, respectively, the relative intensity of 143.4 and 93.61; and the Ag-coated ZnO nano-needles showed a pair of strong peaks at 387.4 nm and 405.2 nm, the relative intensity of 1366 and 1305, respectively, indicating that the Ag-coated ZnO nano-needles can increase the absorption of UV light.

  5. Structure and photoluminescence properties of Ag-coated ZnO nano-needles

    International Nuclear Information System (INIS)

    Li Xiaozhu; Wang Yongqian

    2011-01-01

    Highlights: → ZnO nano-needles were synthesized by thermal oxidation. → Their surfaces were coated with Ag by pulse electro-deposition technique. → The uncoated and coated ZnO nano-needles were characterized. → The results showed that the prepared ZnO nano-needles have been coated with Ag successfully. → The photoluminescence spectrums of ZnO nano-needles with Ag-coated and uncoated were analyzed, finding that the Ag-coated ZnO nano-needles can increase the absorption of UV light. - Abstract: A large number of zinc oxide (ZnO) nano-needles were synthesized by thermal oxidation of pure zinc. The surfaces of ZnO nano-needles were coated with a layer of Ag by pulse electro-deposition technique. The uncoated and coated ZnO nano-needles were characterized by using the X-ray diffraction and the scanning electron microscope (SEM). The results showed that the uncoated samples were close-packed hexagonal structure, which showed needle-like morphology. Their average diameter is about 40 nm, lengths up to 5 μm. At the same time we observed that the prepared ZnO nano-needles have been coated with Ag successfully. The photoluminescence spectrums of ZnO nano-needles with Ag-coated and uncoated were analyzed, finding that the uncoated ZnO nano-needles have two fluorescence peaks at 388 nm and 470.8 nm, respectively, the relative intensity of 143.4 and 93.61; and the Ag-coated ZnO nano-needles showed a pair of strong peaks at 387.4 nm and 405.2 nm, the relative intensity of 1366 and 1305, respectively, indicating that the Ag-coated ZnO nano-needles can increase the absorption of UV light.

  6. Structural and optical properties of Na doped ZnO nanocrystals: Application to solar photocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    Tabib, Asma; Bouslama, Wiem [Laboratoire de Physico-Chimie des Matériaux Minéraux et leurs Applications, Centre National de Recherches en Sciences des Matériaux, B.P. 95 Hammam-Lif, 2050 (Tunisia); Sieber, Brigitte; Addad, Ahmed [UMET, UMR, CNRS 8207, Université Lille 1, 59665 Villeneuve d’Ascq Cédex (France); Elhouichet, Habib, E-mail: habib.elhouichet@fst.rnu.tn [Laboratoire de Physico-Chimie des Matériaux Minéraux et leurs Applications, Centre National de Recherches en Sciences des Matériaux, B.P. 95 Hammam-Lif, 2050 (Tunisia); Département de Physique, Faculté des Sciences de Tunis, University of Tunis, ElManar 2092 (Tunisia); Férid, Mokhtar [Laboratoire de Physico-Chimie des Matériaux Minéraux et leurs Applications, Centre National de Recherches en Sciences des Matériaux, B.P. 95 Hammam-Lif, 2050 (Tunisia); Boukherroub, Rabah [Institut d’Electronique de Microélectronique et de Nanotechnologie (IEMN), UMR, CNRS, 8520 Avenue Pointcarré, BP 60069, 59652 Villeneuve d’Ascq (France)

    2017-02-28

    Highlights: • Na doped ZnO nanocrystals were prepared via sol–gel method. • A substitution of Zn{sup 2+} by Na{sup +} was demonstrated. • Low Na concentration induces higher photocatalytic activity under solar irradiation. • Oxygen vacancies guided the processes of charge separation. - Abstract: Na doped ZnO nanocrystals (NCs) were successfully produced by sol–gel process and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution TEM (HRTEM), Raman scattering, UV–vis diffuse reflectance spectroscopy and photoluminescence (PL). XRD analysis indicated that all the prepared samples present pure hexagonal wurtzite structure without any Na related phases. The lattice distortion, calculated using Williamson hall equation, induces stress and a reduction of NCs size from 71.4 to 24.5 nm. TEM images showed NCs with hexagonal shape and a rather uniform size distribution. The selected area electron diffraction (SAED) patterns confirmed the high crystal quality along the 〈101〉 direction and is consistent with the hexagonal wurtzite structure of ZnO. The Raman spectra are dominated by E{sub 2}{sup high} mode of ZnO. High Na doping shows the occurrence of anomalous local vibrational Raman modes close to 270 and 513 cm{sup −1} that are related to intrinsic host lattice defects and distortion, respectively. Optical band gap was found to vary with Na content. Photoluminescence (PL) spectra indicate the presence of a high density of defects in ZnO NCs which are mainly oxygen vacancies. Finally, the obtained NCs were used as a photocatalyst to degrade Rhodamine B (RhB) in solution, under solar irradiation. Na doping enhances the photocatalytic activity of ZnO NCs till an optimum concentration of 0.5% where a full degradation was observed after 120 min of sun light irradiation. Furthermore, this sample presents a good cycling stability and reusability. Based on scavangers test, it was found that both superoxide and

  7. Investigation of distribution microhomogeneity of doped elements in oxide single crystals by means of LMA-AES

    International Nuclear Information System (INIS)

    Nikolova, L.; Krasnobaeva, N.; Manuilov, N.

    1989-01-01

    The distribution of V and Ti in oxide single crystals Al 2 O 3 :V 3+ , Y 3 Al 5 O 12 :V 3+ , Al 2 O 3 :Ti 3+ , Y 3 Al 5 O 12 :Ti 3+ is investigated by laser emission microspectral analysis with photographic registration of spectra. Single crystals have been grown by the method of vertical directed crystallization (method of Bridgman-Stockbarger). For evaluation of microhomogeneity of the investigated elements distribution the following statistical methods are applied: one-way variance analysis, two-way variance analysis, regression models and gradient method. A PC programme package is developed allowing to process photoregistration data, to choose the internal standard line by scatter diagrams, to perform all statistical analysis and to plot the distribution diagrams of the elements in the samples. 2 refs. (author)

  8. Atomic layer deposition of B-doped ZnO using triisopropyl borate as the boron precursor and comparison with Al-doped ZnO

    NARCIS (Netherlands)

    Garcia - Alonso, D.; Potts, S.E.; Helvoirt, van C.A.A.; Verheijen, M.A.; Kessels, W.M.M.

    2015-01-01

    Doped ZnO films are an important class of transparent conductive oxides, with many applications demanding increased growth control and low deposition temperatures. Therefore, the preparation of B-doped ZnO films by atomic layer deposition (ALD) at 150 °C was studied. The B source was triisopropyl

  9. Photoluminescence emission at room temperature in zinc oxide nano-columns

    International Nuclear Information System (INIS)

    Rocha, L.S.R.; Deus, R.C.; Foschini, C.R.; Moura, F.; Garcia, F. Gonzalez; Simões, A.Z.

    2014-01-01

    Highlights: • ZnO nanoparticles were obtained by microwave-hydrothermal method. • X-ray diffraction reveals a hexagonal structure. • Photoluminescence emission evidenced two absorption peaks, at around 480 nm and 590 nm wavelengths. - Abstract: Hydrothermal microwave method (HTMW) was used to synthesize crystalline zinc oxide (ZnO) nano-columns at the temperature of 120 °C with a soaking time of 8 min. ZnO nano-columns were characterized by using X-ray analyses (XRD), infrared spectroscopy (FT-IR), thermogravimetric analyses (TG-DTA), field emission gun and transmission electron microscopy (FEG-SEM and TEM) and photoluminescence properties (PL). XRD results indicated that the ZnO nano-columns are free of any impurity phase and crystallize in the hexagonal structure. Typical FT-IR spectra for ZnO nano-columns presented well defined bands, indicating a substantial short-range order in the system. PL spectra consist of a broad band at 590 nm and narrow band at 480 nm corresponding to a near-band edge emission related to the recombination of excitons and level emission related to structural defects. These results show that the HTMW synthesis route is rapid, cost effective, and could be used as an alternative to obtain ZnO nano-columns in the temperature of 120 °C for 8 min

  10. Effect of incorporation of zinc oxide nanoparticles on mechanical properties of conventional glass ionomer cements.

    Science.gov (United States)

    Panahandeh, Narges; Torabzadeh, Hassan; Aghaee, Mohammadamin; Hasani, Elham; Safa, Saeed

    2018-01-01

    The aim of this study is to investigate the physical properties of conventional and resin-modified glass ionomer cements (GICs) compared to GICs supplemented with zinc oxide (ZnO) nanofiller particles at 5% (w/w). In this in vitro study, ZnO nanoparticles of different morphologies (nanospherical, nanorod, and nanoflower) were incorporated to glass ionomer powder. The samples were subjected to the flexural strength ( n = 20) and surface hardness test ( n = 12) using a universal testing machine and a Vickers hardness machine, respectively. Surface analysis and crystal structure of samples were performed with scanning electron microscope and X-radiation diffraction, respectively. The data were analyzed using one-way ANOVA, Shapiro-Wilk, and Tukey's tests ( P glass ionomer containing nanoparticles was not significantly different from the control group ( P > 0.05). The surface hardness of the glass ionomer containing nanospherical or nanoflower ZnO was significantly lower than the control group ( P glass ionomer containing nanorod ZnO was not significantly different from the control group ( P = 0.868). Incorporation of nanospherical and nanoflower ZnO to glass ionomer decreased their surface hardness, without any changes on their flexural strength. Incorporation of nanorod ZnO particles caused no effect on the mechanical properties.

  11. Photoluminescence emission at room temperature in zinc oxide nano-columns

    Energy Technology Data Exchange (ETDEWEB)

    Rocha, L.S.R.; Deus, R.C. [Universidade Estadual Paulista – Unesp, Faculdade de Engenharia de Guaratinguetá, Av. Dr. Ariberto Pereira da Cunha, 333, Bairro Portal das Colinas, CEP 12516-410 Guaratinguetá, SP (Brazil); Foschini, C.R. [Universidade Estadual Paulista – Unesp, Instituto de Química, Laboratório Interdisciplinar em Cerâmica (LIEC), Rua Professor Francisco Degni s/n, CEP 14800-90 Araraquara, SP (Brazil); Moura, F.; Garcia, F. Gonzalez [Universidade Federal de Itajubá – Unifei, Campus Itabira, Rua São Paulo, 377, Bairro Amazonas, CEP 35900-37 Itabira, MG (Brazil); Simões, A.Z., E-mail: alezipo@yahoo.com [Universidade Estadual Paulista – Unesp, Faculdade de Engenharia de Guaratinguetá, Av. Dr. Ariberto Pereira da Cunha, 333, Bairro Portal das Colinas, CEP 12516-410 Guaratinguetá, SP (Brazil)

    2014-02-01

    Highlights: • ZnO nanoparticles were obtained by microwave-hydrothermal method. • X-ray diffraction reveals a hexagonal structure. • Photoluminescence emission evidenced two absorption peaks, at around 480 nm and 590 nm wavelengths. - Abstract: Hydrothermal microwave method (HTMW) was used to synthesize crystalline zinc oxide (ZnO) nano-columns at the temperature of 120 °C with a soaking time of 8 min. ZnO nano-columns were characterized by using X-ray analyses (XRD), infrared spectroscopy (FT-IR), thermogravimetric analyses (TG-DTA), field emission gun and transmission electron microscopy (FEG-SEM and TEM) and photoluminescence properties (PL). XRD results indicated that the ZnO nano-columns are free of any impurity phase and crystallize in the hexagonal structure. Typical FT-IR spectra for ZnO nano-columns presented well defined bands, indicating a substantial short-range order in the system. PL spectra consist of a broad band at 590 nm and narrow band at 480 nm corresponding to a near-band edge emission related to the recombination of excitons and level emission related to structural defects. These results show that the HTMW synthesis route is rapid, cost effective, and could be used as an alternative to obtain ZnO nano-columns in the temperature of 120 °C for 8 min.

  12. Facile crystal-structure-controlled synthesis of iron oxides for adsorbents and anode materials of lithium batteries

    International Nuclear Information System (INIS)

    Luo, Yao; Liu, Lihu; Qiao, Wencan; Liu, Fan; Zhang, Yashan; Tan, Wenfeng; Qiu, Guohong

    2016-01-01

    Iron oxides exhibit excellent physicochemical properties as functional materials because of the diversity of crystal structure. Nano-sized iron oxides, including akaganite (β-FeOOH), maghemite (γ-Fe_2O_3), ferrihydrite (Fe_5HO_8∙4H_2O) and hematite (α-Fe_2O_3), were prepared by a facile reflux treatment of iron powder in NaClO solution at 50 °C for 12 h. The crystal structures were controlled by adjusting the pH values of reaction systems. Akaganite, maghemite, ferrihydrite, and hematite were formed when pHs were adjusted to 2–4, 6, 8, and 10, respectively. They showed excellent adsorption performance for As(III), and the adsorption capacity was affected by crystal structure as well as specific surface area. The maximum adsorption capacity for akaganite, maghemite, ferrihydrite, and hematite reached 89.8, 79.1, 78.4, and 63.4 mg g"−"1, respectively. Hematite showed lithium storage capacity of 2043 mAh g"−"1 for the first cycle and then kept stable after twenty cycles at a current density of 100 mA g"−"1. The discharge specific capacity stabilized at 639 mAh g"−"1 after 100 cycles. The as-prepared iron oxides might be applied as potential adsorbents and anode materials for rechargeable lithium-ion battery. - Highlights: • Nano-sized ferric oxides were fabricated by refluxing iron powder in NaClO solutions. • Crystal structures were controlled by adjusting pHs from 2.0 to 10.0 in systems. • Akaganite exhibited the largest As(III) adsorption capacity of 89.8 mg g"−"1. • Hematite had lithium storage capacity of 639 mAh g"−"1 after 100 cycles.

  13. Sonicated sol–gel preparation of nanoparticulate ZnO thin films with various deposition speeds: The highly preferred c-axis (0 0 2) orientation enhances the final properties

    International Nuclear Information System (INIS)

    Malek, M.F.; Mamat, M.H.; Khusaimi, Z.; Sahdan, M.Z.; Musa, M.Z.; Zainun, A.R.; Suriani, A.B.; Md Sin, N.D.; Abd Hamid, S.B.; Rusop, M.

    2014-01-01

    Highlights: • Minimum stress of highly c-axis oriented ZnO was grown at suitable deposition speed. • The ZnO crystal orientation was influenced by strain/stress of the film. • Minimum stress/strain of ZnO film leads to lower defects. • Bandgap and defects were closely intertwined with strain/stress. • We report additional optical and electrical properties based on deposition speed. -- Abstract: Zinc oxide (ZnO) thin films have been deposited onto glass substrates at various deposition speeds by a sonicated sol–gel dip-coating technique. This work studies the effects of deposition speed on the crystallisation behaviour and optical and electrical properties of the resulting films. X-ray diffraction (XRD) analysis showed that thin films were preferentially oriented along the (0 0 2) c-axis direction of the crystal. The transformation sequence of strain and stress effects in ZnO thin films has also been studied. The films deposited at a low deposition speed exhibited a large compressive stress of 0.78 GPa, which decreased to 0.43 GPa as the deposition speed increased to 40 mm/min. Interestingly, the enhancement in the crystallinity of these films led to a significant reduction in compressive stress. All films exhibited an average transmittance of greater than 90% in the visible region, with absorption edges at ∼380 nm. The photoluminescence (PL) measurements indicated that the intensity of the emission peaks varied significantly with deposition speed. The optical band gap energy (E g ) was evaluated as 3.276–3.289 eV, which increased with decreasing compressive stress along the c-axis. The energy band gap of the resulting ZnO films was found to be strongly influenced by the preferred c-axis (0 0 2) orientation

  14. Editorial: dose-dependent ZnO particle-induced acute phase response in humans warrants re-evaluation of occupational exposure limits for metal oxides

    DEFF Research Database (Denmark)

    Vogel, Ulla Birgitte; Cassee, Flemming R.

    2018-01-01

    in autonomic imbalance and particle-induced pulmonary inflammation and acute phase response.The acute phase response is the systemic response to acute and chronic inflammatory states caused by for example bacterial infection, virus infection, trauma and infarction. It is characterized by differential...... studies and SAA has been causally related to the formation of plaques in the aorta in animal studies.In a recent paper in Particle and Fibre Toxicology, Christian Monse et al. provide evidence that inhalation of ZnO nanoparticles induces dose-dependent acute phase response in humans at dose levels well...

  15. Optical properties of oxide magnetic ZnO, Zn{sub 0.95}Mn{sub 0.05}O and Cu{sub 2}O nanopowders

    Energy Technology Data Exchange (ETDEWEB)

    Sokolov, V.I., E-mail: visokolov@imp.uran.r [Institute of Metal Physics UD RAS, S.Kovalevskaya Str. 18, 620041 Yekaterinburg (Russian Federation); Yermakov, A.Ye.; Uimin, M.A.; Mysik, A.A. [Institute of Metal Physics UD RAS, S.Kovalevskaya Str. 18, 620041 Yekaterinburg (Russian Federation); Pustovarov, V.A. [Ural State Technical University, Mira Street 19, 620002 Yekaterinburg (Russian Federation); Chukichev, M.V. [M.V. Lomonosov Moscow State University, Physics Faculty, 119991 Moscow (Russian Federation); Gruzdev, N.B. [Institute of Metal Physics UD RAS, S.Kovalevskaya Str. 18, 620041 Yekaterinburg (Russian Federation)

    2009-12-15

    ZnO, Zn{sub 0.95}Mn{sub 0.05}O and Cu{sub 2}O nanocrystals are synthesized. Excitonic lines in absorption spectra of these materials are detected. In photoluminescence and photoluminescence excitation spectra of Zn{sub 0.95}Mn{sub 0.05}O the dangling bond hybrid (DBH) state is found. It has splitted out from the top of the valence band due to the hybridization between d-states of the Mn impurity and the p-states of oxygen.

  16. Size dependent emission stimulation in ZnO nanosheets

    International Nuclear Information System (INIS)

    Torchynska, T.V.; El Filali, B.

    2014-01-01

    Photoluminescence (PL), X ray diffraction (XRD) and Raman scattering have been studied in crystalline ZnO nanosheets (NSs) of different sizes, estimated by scanning electronic microscopy (SEM). ZnO NSs with the size from the range of 60–600 nm were created by the electrochemical (anodization) method and followed thermal annealing at 400 °C for 2 h in ambient air. XRD study confirms the wurtzite structure of ZnO NSs and has revealed that the lattice parameters increase monotonically with decreasing NS sizes. Simultaneously the intensity of a set of Raman peaks increases and Raman peaks shift into the low energy range. The surface phonon has been detected in smallest size ZnO NSs. Two types of PL bands deal with a set of phonon replicas of free excitons and the defect related emission have been detected in ZnO NSs. The intensity enhancement of exciton- and defect-related PL bands with decreasing ZnO NS sizes has been detected. The intensity stimulation of exciton-related PL bands is attributed to the realization of the week confinement and the exciton-light coupling with the formation of polariton in small size ZnO NSs of 67–170 nm. The intensity rising of defect-related PL bands is attributed to the concentration enlargement of surface defects when the surface to volume ration increases at decreasing ZnO NS sizes. Numerical simulations of radiative lifetimes and exciton radiative recombination rates in ZnO NSs for different emission wavelengths have been done using the exciton-light coupling model. Then the experimental and numerically simulated PL results have been compared and discussed. - Highlights: • Optical and structural investigations of the ZnO nanosheets with the sizes 60–600 nm. • The enlargement of interplanar distances in the wurtzite ZnO crystal lattice is detected. • The change of optic phonon energy and surface phonon appearing are reveled. • ZnO emission stimulation at the week confinement and electron-light coupling with the

  17. Effects of seed layers on controlling of the morphology of ZnO nanostructures and superhydrophobicity of ZnO nanostructure/stearic acid composite films

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jing; Liu, Zhihua, E-mail: sdwfliu@163.com; Liu, Junqi; E, Lei; Liu, Zhifeng, E-mail: tjulzf@163.com

    2016-11-01

    Hydrophobic ZnO self-cleaning thin films with the nanobundles and nanocarpets structures fabricated on indium tin oxides (ITO) glass substrate are reported. The water contact angle of ZnO nanobundles and nanocarpets structures (79° and 67° respectively) is higher than that of unmodified ZnO nanorods. A subsequent chemical treatment with stearic acid (SA) contributed to a superhydrophobic surface with a water contact angle of 159°. Its superhydrophobic property is originated from the nanobundles or nanocarpets structures and surface energy of SA/ZnO nanobundles and SA/ZnO nanocarpets composite nanostructures. Moreover, this promising ZnO nanostructured materials show an important application in self-cleaning smart coatings. - Highlights: • PEG and CTAB are firstly introduced to modify the morphology of ZnO seed layers. • ZnO nanobundles and nanocarpets obtained from different seed layers. • Superhydrophobic surfaces obtained by chemcial treatment using SA.

  18. Structural and optical properties of pure and copper doped zinc oxide nanoparticles

    Science.gov (United States)

    Sajjad, Muhammad; Ullah, Inam; Khan, M. I.; Khan, Jamshid; Khan, M. Yaqoob; Qureshi, Muhammad Tauseef

    2018-06-01

    Pure and copper-doped zinc oxide nanoparticles (NPs) have been synthesized via chemical co-precipitation method where hydrazine is used as reducing agent and aqueous extract of Euphorbia milii plant as capping agent. Main objectives of the reported work are to investigate the effect of copper doping on crystal structure of ZnO nanoparticles; to study the effect of copper doping on optical band gap of ZnO nanoparticles and photoluminescence (PL) study of pure and copper-doped ZnO nanoparticles. To achieve the aforementioned objectives, XRD and SEM tests were performed for the identification and confirmation of crystal structure and morphology of the prepared samples. From XRD data the average grain size for pure ZnO was observed to be 24.62 nm which was first decreased to 18.9