Room-temperature ferromagnetism in pure and Co doped CeO2 powders

International Nuclear Information System (INIS)

Wen Qiye; Zhang Huaiwu; Song Yuanqiang; Yang Qinghui; Zhu Hao; Xiao, John Q

2007-01-01

We report the room-temperature (RT) ferromagnetism (FM) observed in pure and Co doped CeO 2 powder. An insulating nonmagnetic CeO 2 single crystal, after grinding into fine powder, shows an RT-FM with a small magnetization of 0.0045 emu g -1 . However, the CeO 2 powder became paramagnetic after oxygen annealing, which strongly suggests an oxygen vacancy meditated FM ordering. Furthermore, by doping Co into CeO 2 powder the FM can significantly enhance through a F-centre exchange (FCE) coupling mechanism, in which both oxygen vacancies and magnetic ions are involved. As the Co content increases, the FM of Co doped CeO 2 initially increases to a maximum 0.47 emu g -1 , and then degrades very quickly. The complex correlation between the Co content and saturation magnetization was well interpreted by supposing the coexistence of three subsets of Co ions in CeO 2 . Our results reveal that the large RT-FM observed in Co doped CeO 2 powder originates from a combination effect of oxygen vacancies and transition metal doping

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.

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

Effect of Co doping concentration on structural properties and optical parameters of Co-doped ZnO thin films by sol-gel dip-coating method.

Science.gov (United States)

Nam, Giwoong; Yoon, Hyunsik; Kim, Byunggu; Lee, Dong-Yul; Kim, Jong Su; Leem, Jae-Young

2014-11-01

The structural and optical properties of Co-doped ZnO thin films prepared by a sol-gel dip-coating method were investigated. X-ray diffraction analysis showed that the thin films were grown with a c-axis preferred orientation. The position of the (002) peak was almost the same in all samples, irrespective of the Co concentration. It is thus clear that Co doping had little effect on the position of the (002) peak. To confirm that Co2+ was substituted for Zn2+ in the wurtzite structure, optical measurements were conducted at room temperature by a UV-visible spectrometer. Three absorption peaks are apparent in the Co-doped ZnO thin films that do not appear for the undoped ZnO thin film. As the Co concentration was increased, absorption related to characteristic Co2+ transitions increased because three absorption band intensities and the area underneath the absorption wells between 500 and 700 nm increased with increasing Co concentration. The optical band gap and static dielectric constant decreased and the Urbach energy and extinction coefficient increased with increasing Co concentration.

On the sol-gel synthesis and thermal, structural, and magnetic studies of transition metal (Ni, Co, Mn) containing ZnO powders

Energy Technology Data Exchange (ETDEWEB)

Thota, Subhash; Dutta, Titas; Kumar, Jitendra [Materials Science Programme, Indian Institute of Technology Kanpur, Kanpur-208016 (India)

2006-03-01

Transition metal containing ZnO powders (Zn{sub 1-x}M{sub x}O, 0{<=}x{<=}0.30; M = Ni, Mn, Co) have been synthesized by a sol-gel process using zinc acetate dihydrate, respective acetate and oxalic acid as precursors with ethanol as a solvent. The process essentially involves gel formation, drying at 80 {sup 0}C for 24 h to provide the oxalate, and calcination at 500 {sup 0}C for 2 h to undergo an exothermic reaction and yield Zn{sub 1-x}M{sub x}O powder. Their XRD patterns correspond to a wurtzite hcp structure similar to that of pure ZnO, but with the lattice parameters varying slightly with type and extent of doping. It is shown that the dissolution of nickel and cobalt in ZnO is less than 10 at.%, whereas that of manganese lies between 10 and 15 at.%. Other phases that emerge include NiO (hexagonal, a = 2.954 A, c = 7.236 A), ZnCo{sub 2}O{sub 4} (cubic, a = 8.094 A) and ZnMnO{sub 3} (cubic, a = 8.35 A) in the Ni, Co and Mn containing ZnO systems, respectively. Observations of hysteresis loops both at 10 and 320 K and the nature of ESR spectra provide evidence for the ferromagnetic state in nickel containing ZnO powder. Besides, the deviation occurs in the magnetization versus temperature curves in zero field cooled (ZFC) and field cooled (FC) conditions (blocking temperature T{sub B} being 32 K for 5 at.% Ni). The magnetic behaviour of manganese and cobalt doped zinc oxide is, however, different, namely (i) no hysteresis loops (ii) decrease in magnetization with increase of Mn or Co content, and (iii) identical M-T curves under ZFC and FC conditions. The inverse susceptibility versus temperature curves of Zn{sub 1-x}Mn{sub x}O compounds reveal ferrimagnetism with Neel temperature T{sub N} of 4 K for x = 0.02, but antiferromagnetism for x = 0.15 and 0.25 with Curie-Weiss temperature of -43 and -30 K, respectively.

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

International Nuclear Information System (INIS)

Pan, Zhanchang; Luo, Junming; Tian, Xinlong; Wu, Shoukun; Chen, Chun; Deng, Jianfeng; Xiao, Chumin; Hu, Guanghui; Wei, Zhigang

2014-01-01

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

On single doping and co-doping of spray pyrolysed ZnO films: Structural, electrical and optical characterisation

International Nuclear Information System (INIS)

Vimalkumar, T.V.; Poornima, N.; Jinesh, K.B.; Kartha, C. Sudha; Vijayakumar, K.P.

2011-01-01

In this paper we present studies on ZnO thin films (prepared using Chemical Spray pyrolysis (CSP) technique) doped in two different ways; in one set, 'single doping' using indium was done while in the second set, 'co-doping' using indium and fluorine was adopted. In the former case, effect of in-situ as well as ex-situ doping using In was analyzed. Structural (XRD studies), electrical (I-V measurements) and optical characterizations (through absorption, transmission and photoluminescence studies) of the films were done. XRD analysis showed that, for spray-deposited ZnO films, ex-situ doping using Indium resulted in preferred (0 0 2) plane orientation, while in-situ doping caused preferred orientation along (1 0 0), (0 0 2), (1 0 1) planes; however for higher percentage of in-situ doping, orientation of grains changed from (0 0 2) plane to (1 0 1) plane. The co-doped films had (0 0 2) and (1 0 1) planes. Lowest resistivity (2 x 10 -3 Ω cm) was achieved for the films, doped with 1% Indium through in-situ method. Photoluminescence (PL) emissions of ex-situ doped and co-doped samples had two peaks; one was the 'near band edge' emission (NBE) and the other was the 'blue-green' emission. But interestingly the PL emission of in-situ doped samples exhibited only the 'near band edge' emission. Optical band gap of the films increased with doping percentage, in all cases of doping.

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.

TUNABLE MAGNETIC AND ELECTRICAL PROPERTIES OF Co-DOPED ZnO FILMS BY VARYING OXYGEN PARTIAL PRESSURE

OpenAIRE

L. G. WANG; H. W. ZHANG; X. L. TANG; Y. X. LI; Z. Y. ZHONG

2011-01-01

High quality Co-doped ZnO films with good reproducibility have been prepared under different oxygen partial pressure by radio-frequency magnetron sputtering. These films were characterized using numerous characterization techniques including X-ray diffraction, electrical transport, and magnetization measurements. The effect of oxygen partial pressure on the structural, magnetic, and electrical properties of Co-doped ZnO films has been systematically studied. It was found that the structural, ...

Characteristics of hydrogen co-doped ZnO : Al thin films

International Nuclear Information System (INIS)

Lee, S H; Lee, T S; Lee, K S; Cheong, B; Kim, W M; Kim, Y D

2008-01-01

ZnO films co-doped with H and Al (HAZO) were prepared by sputtering ZnO targets containing 1 wt% Al 2 O 3 on Corning glass at a substrate temperature of 150 deg. C with Ar and H 2 /Ar gas mixtures. The effects of hydrogen addition to Al-doped ZnO (AZO) films with low Al content on the electrical, the optical and the structural properties of the as-grown films as well as the vacuum- and air-annealed films were examined. Secondary ion mass spectroscopy analysis showed that the hydrogen concentration increased with increasing H 2 in sputter gas. For the as-deposited films, the free carrier number increased with increasing H 2 . The Hall mobility increased at low hydrogen content, reaching a maximum before decreasing with a further increase of H 2 content in sputter gas. Annealing at 300 deg. C resulted in the removal of hydrogen, causing a decrease in the carrier concentration. It was shown that hydrogen might exist as single isolated interstitial hydrogen bound with oxygen, thereby acting like an anionic dopant. Also, it was shown that the addition of hydrogen to ZnO films doped with low metallic dopant concentration could yield transparent conducting films with very low absorption loss as well as with proper electrical properties, which is suitable for thin film solar cell applications

Structural, optical and magnetic properties of nanocrystalline Co-doped ZnO thin films grown by sol-gel

Energy Technology Data Exchange (ETDEWEB)

Kayani, Zohra Nazir; Shah, Iqra; Zulfiqar, Bareera; Sabah, Aneeqa [Lahore College for Women Univ., Lahore (Pakistan); Riaz, Saira; Naseem, Shahzad [Univ. of the Punjab, Lahore (Pakistan). Centre of Excellence in Solid State Physics

2018-04-01

Cobalt-doped ZnO thin films have been deposited using a sol-gel route by changing the number of coats on the substrate from 6 to 18. This project deals with various film thicknesses by increasing the number of deposited coats. The effect of thickness on structural, magnetic, surface morphology and optical properties of Co-doped ZnO thin film was studied. The crystal structure of the Co-doped ZnO films was investigated by X-ray diffraction. The films have polycrystalline wurtzite hexagonal structures. A Co{sup 2+} ion takes the place of a Zn{sup 2+} ion in the lattice without creating any distortion in its hexagonal wurtzite structure. An examination of the optical transmission spectra showed that the energy band gap of the Co-doped ZnO films increased from 3.87 to 3.97 eV with an increase in the number of coatings on the substrate. Ferromagnetic behaviour was confirmed by measurements using a vibrating sample magnetometer. The surface morphology of thin films was assessed by scanning electron microscope. The grain size on the surface of thin films increased with an increase in the number of coats.

Enhanced room temperature ferromagnetism in electrodeposited Co-doped ZnO nanostructured thin films by controlling the oxygen vacancy defects

Energy Technology Data Exchange (ETDEWEB)

Simimol, A. [Nanomaterials Research Lab, Surface Engineering Division, CSIR-National Aerospace Laboratories, Post Bag No. 1779, Bangalore 560017 (India); Department of Physics, National Institute of Technology Calicut, Calicut 673601 (India); Anappara, Aji A. [Department of Physics, National Institute of Technology Calicut, Calicut 673601 (India); Greulich-Weber, S. [Department of Physics, Nanophotonic Materials, Faculty of Science, University of Paderborn, 33095 Paderborn (Germany); Chowdhury, Prasanta [Nanomaterials Research Lab, Surface Engineering Division, CSIR-National Aerospace Laboratories, Post Bag No. 1779, Bangalore 560017 (India); Barshilia, Harish C., E-mail: harish@nal.res.in

2015-06-07

We report the growth of un-doped and cobalt doped ZnO nanostructures fabricated on FTO coated glass substrates using electrodeposition method. A detailed study on the effects of dopant concentration on morphology, structural, optical, and magnetic properties of the ZnO nanostructures has been carried out systematically by varying the Co concentration (c.{sub Co}) from 0.01 to 1 mM. For c.{sub Co }≤ 0.2 mM, h-wurtzite phase with no secondary phases of Co were present in the ZnO nanostructures. For c.{sub Co} ≤ 0.2 mM, the photoluminescence spectra exhibited a decrease in the intensity of ultraviolet emission as well as band-gap narrowing with an increase in dopant concentration. All the doped samples displayed a broad emission in the visible range and its intensity increased with an increase in Co concentration. It was found that the defect centers such as oxygen vacancies and zinc interstitials were the source of the visible emission. The X-ray photoelectron spectroscopy studies revealed, Co was primarily in the divalent state, replacing the Zn ion inside the tetrahedral crystal site of ZnO without forming any cluster or secondary phases of Co. The un-doped ZnO nanorods exhibited diamagnetic behavior and it remained up to a c.{sub Co} of 0.05 mM, while for c.{sub Co }> 0.05 mM, the ZnO nanostructures exhibited ferromagnetic behavior at room temperature. The coercivity increased to 695 G for 0.2 mM Co-doped sample and then it decreased for c.{sub Co }> 0.2 mM. Our results illustrate that up to a threshold concentration of 0.2 mM, the strong ferromagnetism is due to the oxygen vacancy defects centers, which exist in the Co-doped ZnO nanostructures. The origin of strong ferromagnetism at room temperature in Co-doped ZnO nanostructures is attributed to the s-d exchange interaction between the localized spin moments resulting from the oxygen vacancies and d electrons of Co{sup 2+} ions. Our findings provide a new insight for tuning the

Local fields in Co and Mn Co-doped ZnO

Energy Technology Data Exchange (ETDEWEB)

Sato, W., E-mail: wsato@se.kanazawa-u.ac.jp [Kanazawa University, Institute of Science and Engineering (Japan); Kano, Y.; Suzuki, T.; Nakagawa, M. [Kanazawa University, Graduate School of Natural Science and Technology (Japan); Kobayashi, Y. [The University of Electro-Communications, Department of Engineering Science (Japan)

2016-12-15

The magnetic properties of ZnO co-doped with 5 at. % Co and 5 at. % Mn(Zn{sub 0.90}Co{sub 0.05}Mn{sub 0.05}O) synthesized by a solid-state reaction were investigated by means of {sup 57}Co emission Mössbauer spectroscopy. The majority of the probe ions (80 %) residing in defect-free substitutional Zn sites take the oxidation state of {sup 57}Fe {sup 2+}, and the others presumably form local defects taking the state of {sup 57}Fe {sup 3+} at room temperature. Both components show doublets, and RT ferromagnetism was thus absent in the sample. For the measurement at 10 K, spectral broadening was observed, implying a possible presence of a weak magnetic component.

Enhancement of ferromagnetic properties in Zn0.98Cu0.02O by additional Co doping

International Nuclear Information System (INIS)

Liu, Huilian; Zhang, Xu; Liu, Hongbo; Yang, Jinghai; Liu, Yang; Liu, Xiaoyan; Gao, Ming; Wei, Maobin; Cheng, Xin; Wang, Jian

2013-01-01

Highlights: •The samples were synthesized by sol–gel technology to dope up to 3% Co in ZnCuO. •After Co doped into Zn 0.98 Cu 0.02 O sample photoluminescence shows an increase in green emission. •The saturation magnetization increased with Co doping. -- Abstract: Zn 0.98 Cu 0.02 O and Zn 0.95 Cu 0.02 Co 0.03 O powders were synthesized by sol–gel method, and the effects of Co codoping on the structure, optical and magnetic properties of the Zn 0.98 Cu 0.02 O powders were studied in detail. The X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurement shows the Zn 0.98 Cu 0.02 O and Zn 0.95 Cu 0.02 Co 0.03 O powders were single phase with the ZnO wurtzite structure, and there was no ferromagnetic-related secondary phase in these powders. Moreover, these powders exhibited ferromagnetism at the room temperature investigated by the magnetic measurement, and the ferromagnetism of the Zn 0.98 Cu 0.02 O and Zn 0.95 Cu 0.02 Co 0.03 O samples were originated from the fact that the Cu ions and Co, Cu ions doped into the ZnO lattices, respectively. In addition, the saturation magnetization (Ms) was significantly increased with Co codoping due to the increased density of oxygen vacancies

Effect of cobalt doping on the mechanical properties of ZnO nanowires

Energy Technology Data Exchange (ETDEWEB)

Vahtrus, Mikk; Šutka, Andris [Institute of Physics, University of Tartu, W. Ostwaldi 1, 50412 Tartu (Estonia); Polyakov, Boris [Institute of Solid State Physics, University of Latvia, Kengaraga 8, LV-1063 Riga (Latvia); Oras, Sven; Antsov, Mikk [Institute of Physics, University of Tartu, W. Ostwaldi 1, 50412 Tartu (Estonia); Doebelin, Nicola [RMS Foundation, Bischmattstrasse 12, Bettlach 2544 (Switzerland); Institute of Geological Sciences, University of Bern, Baltzerstrasse 1–3, Bern 3012 (Switzerland); Lõhmus, Rünno; Nõmmiste, Ergo [Institute of Physics, University of Tartu, W. Ostwaldi 1, 50412 Tartu (Estonia); Vlassov, Sergei, E-mail: vlassovs@ut.ee [Institute of Physics, University of Tartu, W. Ostwaldi 1, 50412 Tartu (Estonia)

2016-11-15

In this work, we investigate the influence of doping on the mechanical properties of ZnO nanowires (NWs) by comparing the mechanical properties of pure and Co-doped ZnO NWs grown in similar conditions and having the same crystallographic orientation [0001]. The mechanical characterization included three-point bending tests made with atomic force microscopy and cantilever beam bending tests performed inside scanning electron microscopy. It was found that the Young's modulus of ZnO NWs containing 5% of Co was approximately a third lower than that of the pure ZnO NWs. Bending strength values were comparable for both materials and in both cases were close to theoretical strength indicating high quality of NWs. Dependence of mechanical properties on NW diameter was found for both doped and undoped ZnO NWs. - Highlights: •Effect of Co doping on the mechanical properties of ZnO nanowires is studied. •Co substitutes Zn atoms in ZnO crystal lattice. •Co addition affects crystal lattice parameters. •Co addition results in significantly decreased Young's modulus of ZnO. •Bending strength for doped and undoped wires is close to the theoretical strength.

Synergistic effect of indium and gallium co-doping on the properties of RF sputtered ZnO thin films

Science.gov (United States)

Shaheera, M.; Girija, K. G.; Kaur, Manmeet; Geetha, V.; Debnath, A. K.; Karri, Malvika; Thota, Manoj Kumar; Vatsa, R. K.; Muthe, K. P.; Gadkari, S. C.

2018-04-01

ZnO thin films were synthesized using RF magnetron sputtering, with simultaneous incorporation of Indium (In) and Gallium (Ga). The structural, optical, chemical composition and surface morphology of the pure and co-doped (IGZO) thin films were characterized by X-Ray diffraction (XRD), UV-visible spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), and Raman spectroscopy. XRD revealed that these films were oriented along c-axis with hexagonal wurtzite structure. The (002) diffraction peak in the co-doped sample was observed at 33.76° with a slight shift towards lower 2θ values as compared to pure ZnO. The surface morphology of the two thin films was observed to differ. For pure ZnO films, round grains were observed and for IGZO thin films round as well as rod type grains were observed. All thin films synthesized show excellent optical properties with more than 90% transmission in the visible region and band gap of the films is observed to decrease with co-doping. The co doping of In and Ga is therefore expected to provide a broad range optical and physical properties of ZnO thin films for a variety of optoelectronic applications.

Effect of strain on the structural and optical properties of Cu-N co-doped ZnO thin films

International Nuclear Information System (INIS)

Zhao Yue; Zhou Mintao; Li Zhao; Lv Zhiyong; Liang Xiaoyan; Min Jiahua; Wang Linjun; Shi Weimin

2011-01-01

Polycrystalline ZnO thin films co-doped with Cu and N have been obtained by chemical bath deposition. Introduction of Cu and N causes the change of strained stress in ZnO films, which subsequently affects the structural and optical properties. The dependence of structural and optical properties of the ZnO films on lattice strained stress is investigated by XRD measurement, SEM, PL spectrum, optical reflection and Raman spectrum. The result of photoluminescence of Cu-N co-doped ZnO films indicates that the UV emission peaks shift slightly towards higher energy side with decrease in tensile strain and vise versa. The blue-shift of the absorption edge and up-shift of E2 (high) mode of the films can be observed in the optical reflection and Raman spectra. - Highlights: →Cu-N co-doped ZnO is first prepared by the wet chemical method. → Stress is produced by the introduction of Cu and N atoms. → Effect of stress on the structural and optical properties of ZnO film is investigated. → Cu concentration will be used to control the structural and optical properties.

A Mössbauer and magnetic study of ball milled Fe-doped ZnO Powders

Energy Technology Data Exchange (ETDEWEB)

Zamora, Ligia E., E-mail: ligia.zamora@correounivalle.edu.co; Paz, J. C.; Piamba, J. F.; Tabares, J. A.; Alcázar, G. A. Pérez [Universidad del Valle, Departamento de física (Colombia)

2015-06-15

The structural and magnetic properties of Fe-doped ZnO are reported in this study, as obtained by mechanical alloying from elemental powders of ZnO and Fe. The properties of Zn{sub 0.90}Fe{sub 0.10}O samples alloying while varying the milling time (6, 12, 24 and 36 h) are also reported. The Rietveld refinement of X-ray Diffraction (XRD) patterns revealed that the system presents two structures: the würtzite structure of ZnO and the bcc structure of α-Fe. The Mössbauer spectra show that the samples present three components: a ferromagnetic component, associated with the Fe phase and two paramagnetic components, associated with the Fe atoms, which penetrate inside the ZnO matrix behaving as Fe{sup 3+} and Fe{sup 2+}. The milling time contributes to an increase in the paramagnetic sites, and a solubility limit of the Fe atoms in the ZnO lattice was detected. The VSM measurements at room temperature detected ferromagnetic behavior with a saturation magnetization of 11 emu/g and a coercive field of 330 Oe for the sample alloyed over 24 h. A similar behavior was shown by the other samples.

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.

Electrochemical investigation of the properties of Co doped ZnO nanoparticle as a corrosion inhibitive pigment for modifying corrosion resistance of the epoxy coating

International Nuclear Information System (INIS)

Rostami, M.; Rasouli, S.; Ramezanzadeh, B.; Askari, A.

2014-01-01

Highlights: • Corrosion inhibitive pigment based on ZnOCo was synthesized through combustion method. • Doping ZnO nanoparticle with Co enhanced its inhibition properties considerably. • ZnOCo nanoparticle could enhance corrosion protective performance of epoxy coating. • Co doped ZnO nanoparticles behaved as efficient barrier and inhibitive pigment. - Abstract: Co doped ZnO nanoparticles were synthesized by combustion method. Then, the epoxy nanocomposites were prepared using various amounts of nanoparticles. Salt spray and electrochemical impedance spectroscopy (EIS) were used in order to investigate the corrosion inhibition effects of nanoparticles on the steel substrate. The morphology and composition of the films precipitated on the steel surface were investigated by scanning electron microscope (SEM) and energy dispersive spectroscopy. Results revealed that the corrosion inhibition properties of ZnO nanoparticle were significantly enhanced after doping with Co. Moreover, Co doped ZnO nanoparticles enhanced the corrosion resistance of the epoxy coating effectively

Development of transparent conductive indium and fluorine co-doped ZnO thin films: Effect of F concentration and post-annealing temperature

Energy Technology Data Exchange (ETDEWEB)

Hadri, A. [University Mohammed V, Faculty of Sciences, Physics Department, LPM, B.P. 1014, Rabat (Morocco); Taibi, M. [University of Mohammed V, LPCMIN, Ecole Normale Superieure, Rabat (Morocco); Loghmarti, M.; Nassiri, C.; Slimani Tlemçani, T. [University Mohammed V, Faculty of Sciences, Physics Department, LPM, B.P. 1014, Rabat (Morocco); Mzerd, A., E-mail: mzerd@yahoo.fr [University Mohammed V, Faculty of Sciences, Physics Department, LPM, B.P. 1014, Rabat (Morocco)

2016-02-29

In the present work ZnO, In doped ZnO and In-F co-doped ZnO (IFZO) films were synthesized on heated glass substrates (350 °C) by the chemical spray technique. The effect of fluorine concentration on the structural, morphological, optical and electrical properties was studied. It was observed from X-ray diffraction (XRD) that the films have a polycrystalline structure and the intensity of the peaks depend on the doping and co-doping concentration. No diffraction peak related to dopants in XRD patterns along with shift in peaks angles to ZnO proved that In and F ions were doped into ZnO thin films. The Raman spectra confirm the hexagonal structure of the as-deposited films, and demonstrated an enhancement of the surface phonon mode of doped and co-doped films as compared to undoped films. The as-deposited films showed an average transmittance above 70%, in the wavelength range of 400–800 nm. A minimum electrical resistivity, in the order of 5.2 × 10{sup −} {sup 2} Ω cm was obtained for the IFZO thin film with 5 at.% F doping. Moreover, the electrical properties of doped and co-doped films were enhanced after post-deposition annealing. It was found that post-annealed thin films at 350 °C showed a decrease of one order of magnitude of the resistivity values. Such a transparent and conducting thin film can be suitable for optical and electrical applications owing to their low resistivity combined with high transmittance in the visible range. - Highlights: • Conductive transparent ZnO, IZO, IFZO thin films were deposited by spray pyrolysis. • Doping and co-doping affect morphology and optoelectrical properties. • As deposited film with high fluorine content exhibited high carrier mobility (55 cm{sup 2} V{sup −} {sup 1} s{sup −} {sup 1}). • Correlation between intrinsic defects and carrier mobility was observed. • Post-annealing in Ar atmosphere improves conductivity.

Efficient photocatalytic performance enhancement in Co-doped ZnO nanowires coupled with CuS nanoparticles

Science.gov (United States)

Li, Wei; Wang, Guojing; Feng, Yimeng; Li, Zhengcao

2018-01-01

In this research, a kind of highly efficient semiconductor photocatalyst was fabricated by depositing CuS nanoparticles uniformly on the surface of Co-doped ZnO nanowires. ZnO nanowires were synthesized by hydrothermal method and CuS nanoparticles were modified by successive ionic layer adsorption and reaction (SILAR). By conducting methyl orange (MO) degradation experiments under the illumination of visible light, the photocatalytic activity of Co-doped ZnO nanowires modified with CuS nanoparticles was found to be nearly three times active when compared to bare ZnO nanowires. Its superior photocatalytic performance has two main reasons. The doped Co2+ ions can inhibit the recombination of photo-generated electron-hole pairs and decrease the optical bandgap, while the p-n heterostructure can enhance the visible light absorption ability and promote the separation of photo-excited charge carriers. Furthermore, the effect of the amount of deposited CuS nanoparticles on the photocatalysis was also investigated. The photocatalytic efficiency firstly raised along with the increment of SILAR cycle times and reached a maximum at 10 cycles but then decreased as the cycle times continue to increase. This originates from that an excessive amount of CuS would not only cover the active reacting sites, but also serve as recombination centers. Overall, this new nanostructure is expected to work as an efficient photocatalyst.

Al-doped ZnO mechanical milled powders for dye sensitized cells

International Nuclear Information System (INIS)

Damonte, L.C.; Donderis, V.; Ferrari, S.; Orozco, J.; Hernandez-Fenollosa, M.A.

2010-01-01

Mixtures of Al 2 O 3 and ZnO powders were prepared by mechanical milling. The resulting samples were analyzed and characterized by X-ray diffraction (XRD), positron annihilation lifetime spectroscopy (PALS), scanning electron microscopy (SEM) and optical reflection spectroscopy (OPS). XRD and PALS measurements confirm Al incorporation into ZnO wurtzite structure. Powders obtained from Al 2 O 3 precursors display better reflectivity than those prepared from Al metal so they might be better materials for implementation in photovoltaic solar devices.

Systematic approach on the fabrication of Co doped ZnO semiconducting nanoparticles by mixture of fuel approach for Antibacterial applications

Science.gov (United States)

Rajendar, V.; Dayakar, T.; Shobhan, K.; Srikanth, I.; Venkateswara Rao, K.

2014-11-01

Zinc oxide (ZnO) is a wide band gap semiconductor (3.2 eV) with a high exciton binding energy (60 meV), where it has wide applications in advanced spintronic devices. The theoretical prediction of room temperature ferromagnetism and also antibacterial activity will be possible through the investigation of diluted magnetic semiconductors (DMS), such as transition metal doped ZnO, especially Cobalt doped ZnO. The aim of the work is the synthesis of Cobalt (Co) doped ZnO nanopowders were prepared Zn1-xCoxO (0 ⩽ x ⩾ 0.09) nanopowders from Sol-Gel auto combustion method have been synthesized with precursors such as Zinc and Cobalt nitrates with the assistance Ammonium acetate & Urea as fuel by increasing the cobalt concentration in zinc oxide and their structural, morphological, optical, Thermal, magnetic and antibacterial properties were studied by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), Transmission Electron microscope (TEM), UV-visible spectroscopy, thermo gravimetric/differential thermal analysis (TG/DTA) and vibrating sample magneto meter (VSM). From the antibacterial studies, against gram positive Bacillus subtilis bacteria is most abundant bacteria in soil and indoor atmosphere, which affects the stored spintronic devices so that the devices should be made with antibacterial activity of DMS like Co doped ZnO. In this article is found that ZnO:Co nanopowders with higher Co doping level (0.07 and 0.09 wt%) exhibit good antibacterial efficiency. The magnetization curves obtained using vibrating sample magnetometer (VSM) show a sign of strong room temperature ferromagnetic behavior when the Co doping level is 0.05 wt% and a weak room temperature ferromagnetic behavior Co doping level is below 0.07 wt%, and also they found to exhibit antiferromagnetic and paramagnetic properties, when the Co doping levels are 0.07 and 0.09 wt%, respectively, to enhance and increase the special magnetic and antibacterial property for

Al-doped ZnO mechanical milled powders for dye sensitized cells

Energy Technology Data Exchange (ETDEWEB)

Damonte, L.C., E-mail: damonte@fisica.unlp.edu.a [Departamento de Fisica, UNLP, IFLP-CCT-CONICET, C.C.67(1900), La Plata (Argentina); Dto. de Fisica Aplicada, Universidad Politecnica de Valencia, Cami de Vera s/n, 46022 Valencia (Spain); Donderis, V. [Dto. de Ingenieria Electrica, Universidad Politecnica de Valencia, Cami de Vera s/n, 46022 Valencia (Spain); Ferrari, S. [Departamento de Fisica, UNLP, IFLP-CCT-CONICET, C.C.67(1900), La Plata (Argentina); Orozco, J. [ITM, Universidad Politecnica de Valencia, Cami de Vera s/n, 46022 Valencia (Spain); Hernandez-Fenollosa, M.A. [Dto. de Fisica Aplicada, Universidad Politecnica de Valencia, Cami de Vera s/n, 46022 Valencia (Spain)

2010-04-16

Mixtures of Al{sub 2}O{sub 3} and ZnO powders were prepared by mechanical milling. The resulting samples were analyzed and characterized by X-ray diffraction (XRD), positron annihilation lifetime spectroscopy (PALS), scanning electron microscopy (SEM) and optical reflection spectroscopy (OPS). XRD and PALS measurements confirm Al incorporation into ZnO wurtzite structure. Powders obtained from Al{sub 2}O{sub 3} precursors display better reflectivity than those prepared from Al metal so they might be better materials for implementation in photovoltaic solar devices.

Properties of fluorine and tin co-doped ZnO thin films deposited by sol–gel method

International Nuclear Information System (INIS)

Pan, Zhanchang; Zhang, Pengwei; Tian, Xinlong; Cheng, Guo; Xie, Yinghao; Zhang, Huangchu; Zeng, Xiangfu; Xiao, Chumin; Hu, Guanghui; Wei, Zhigang

2013-01-01

Highlights: •F and Sn co-doped ZnO thin films were synthesized by sol–gel method. •The effects of different F doping concentrations were investigated. •The co-doped nanocrystals exhibit good crystal quality. •The origin of the photoluminescence emissions was discussed. •The films showed high transmittance and low resistivity. -- Abstract: Highly transparent and conducting fluorine (F) and tin (Sn) co-doped ZnO (FTZO) thin films were deposited on glass substrates by the sol–gel processing. The structure and morphology of the films are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) with various F doping concentrations. SEM images showed that the hexagonal ZnO crystals were well-arranged on the glass substrates and the HRTEM images indicated that the individual nanocrystals are highly oriented and exhibited a perfect lattice structure. Owing to its high carrier concentration and mobility, as well as good crystal quality, a minimum resistivity of 1 × 10 −3 Ω cm was obtained from the FTZO thin film with 3% F doping, and the average optical transmittance in the entire visible wavelength region was higher than 90%. The X-ray photoelectron spectroscopy (XPS) study confirmed the substitution of Zn 2+ by Sn ions and Room temperature photoluminescence (PL) observed for pure and FTZO thin films suggested the films exhibit a good crystallinity with a very low defect concentration

Single and couple doping ZnO nanocrystals characterized by positron techniques

Science.gov (United States)

Pasang, Tenzin; Namratha, Keerthiraj; Guagliardo, Paul; Byrappa, Kullaiah; Ranganathaiah, Chikkakuntappa; Samarin, S.; Williams, J. F.

2015-04-01

Zinc oxide (ZnO) nanocrystals have been synthesized using a mild hydrothermal process using low temperatures and pressures with the advantages of free growth catalyst, low cost and alternative technology. Positron annihilation lifetime spectroscopy and coincidence Doppler broadening (CDB) spectroscopic methods have been used to investigate the roles of single- and co-dopants and native defects of the ZnO nanocrystals controlled by the synthesis process. It is shown that single Ag1+ and Pd2+ dopants occupy interstitial sites of the ZnO lattice and single Ru3+ doping replaces Zn vacancies substitutionally with a significant effect on the CDB momentum ratio curves when compared using ZnO as the reference spectrum. The co-doping of the ZnO lattice with (Sn4+ + Co2+) shows similar CDB ratios as Ru3+ single-doping. Also co-doping with (Ag1+ + Pd2+) or (Ag1+ + W6+) shows significant decreases in the band gap energy up to about 12.6% compared to single doping. The momentum ratio curves, referenced to undoped ZnO, indicate dopants in interstitial and substitutional sites. The presence of transition metal ions interstitially will trap electrons which resist the recombination of electrons and in turn affect the conductivity of the material.

Single and couple doping ZnO nanocrystals characterized by positron techniques

International Nuclear Information System (INIS)

Pasang, Tenzin; Namratha, Keerthiraj; Byrappa, Kullaiah; Guagliardo, Paul; Ranganathaiah, Chikkakuntappa; Samarin, S; Williams, J F

2015-01-01

Zinc oxide (ZnO) nanocrystals have been synthesized using a mild hydrothermal process using low temperatures and pressures with the advantages of free growth catalyst, low cost and alternative technology. Positron annihilation lifetime spectroscopy and coincidence Doppler broadening (CDB) spectroscopic methods have been used to investigate the roles of single- and co-dopants and native defects of the ZnO nanocrystals controlled by the synthesis process. It is shown that single Ag 1+ and Pd 2+ dopants occupy interstitial sites of the ZnO lattice and single Ru 3+ doping replaces Zn vacancies substitutionally with a significant effect on the CDB momentum ratio curves when compared using ZnO as the reference spectrum. The co-doping of the ZnO lattice with (Sn 4+ + Co 2+ ) shows similar CDB ratios as Ru 3+ single-doping. Also co-doping with (Ag 1+ + Pd 2+ ) or (Ag 1+ + W 6+ ) shows significant decreases in the band gap energy up to about 12.6% compared to single doping. The momentum ratio curves, referenced to undoped ZnO, indicate dopants in interstitial and substitutional sites. The presence of transition metal ions interstitially will trap electrons which resist the recombination of electrons and in turn affect the conductivity of the material. (paper)

The effect of Co and In combinational or individual doping on the structural, optical and selective sensing properties of ZnO nanoparticles

CSIR Research Space (South Africa)

Maswanganye, MW

2017-08-01

Full Text Available , is found to increase the response to all stimuli to higher values than undoped or singly doped ZnO sensors at the expense of selectivity where In-Co-ZnO as well as undoped ZnO and Co-ZnO sensors have similar selectivity value of below 44% to CO. In-doped Zn...

Comparative investigation on cation-cation (Al-Sn) and cation-anion (Al-F) co-doping in RF sputtered ZnO thin films: Mechanistic insight

Energy Technology Data Exchange (ETDEWEB)

Mallick, Arindam; Basak, Durga, E-mail: sspdb@iacs.res.in

2017-07-15

Highlights: • Comparative study on Al, Al-Sn and Al-F doped ZnO films has been carried out. • High transparent Al-F co-doped film shows three times enhanced carrier density. • Al-F co-doped film shows larger carrier relaxation time. • Al-Sn co-doped films shows carrier transport dominated by impurity scattering. • Al-F co-doped ZnO film can be applied as transparent electrode. - Abstract: Herein, we report a comparative mechanistic study on cation-cation (Al-Sn) and cation-anion (Al-F) co-doped nanocrystalline ZnO thin films grown on glass substrate by RF sputtering technique. Through detailed analyses of crystal structure, surface morphology, microstructure, UV-VIS-NIR transmission-reflection and electrical transport property, the inherent characteristics of the co-doped films were revealed and compared. All the nanocrystalline films retain the hexagonal wurtzite structure of ZnO and show transparency above 90% in the visible and NIR region. As opposed to expectation, Al-Sn (ATZO) co-doped film show no enhanced carrier concentration consistent with the probable formation of SnO{sub 2} clusters supported by the X-ray photoelectron spectroscopy study. Most interestingly, it has been found that Al-F (AFZO) co-doped film shows three times enhanced carrier concentration as compared to Al doped and Al-Sn co-doped films attaining a value of ∼9 × 10{sup 20} cm{sup −3} due to the respective cation and anion substitution. The carrier relaxation time increases in AFZO while it decreases significantly for ATZO film consistent with the concurrence of the impurity scattering in the latter.

Preparation of nanometer sized Mn doped Zn based oxides powder for DMS applications

CSIR Research Space (South Africa)

Das, J

2009-01-01

Full Text Available In order to study the size dependent DMS (Diluted Magnetic Semiconductor) behavior of Mn doped ZnO, the authors have systematically prepared a series of nanosized green powder based on Mn doped ZnO (Zn 1-x Mn x O, where x=0.02 - 0.1) materials using...

Structural and magnetic Properties of Mn, Co, Ni doped ZnO ...

African Journals Online (AJOL)

It is abundant, cost effective, non-toxic and also it is used in many bio-medical applications. ... The XRD of Mn-doped ZnO nanocrystals shows hexagonal structure. ... The TM doped ZnO nanocrystals shows weak ferromagnetic properties at ...

Structural, chemical and magnetic properties of secondary phases in Co-doped ZnO

DEFF Research Database (Denmark)

Ney, A; Kovács, András; Ney, V

2011-01-01

, chemical and magnetic properties of Co-doped ZnO samples. It can be established on a quantitative basis that the superparamagnetic (SPM) behavior observed by integral superconducting quantum interference device magnetometry is not an intrinsic property of the material but stems from precipitations...

Impacts of Co doping on ZnO transparent switching memory device characteristics

Energy Technology Data Exchange (ETDEWEB)

Simanjuntak, Firman Mangasa; Wei, Kung-Hwa [Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Prasad, Om Kumar [Department of Electrical Engineering and Computer Science, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Panda, Debashis [Department of Electronics Engineering, National Institute of Science and Technology, Berhampur, Odisha 761008 (India); Lin, Chun-An; Tsai, Tsung-Ling; Tseng, Tseung-Yuen, E-mail: tseng@cc.nctu.edu.tw [Department of Electronics Engineering and Institute of Electronics, National Chiao Tung University, Hsinchu 30010, Taiwan (China)

2016-05-02

The resistive switching characteristics of indium tin oxide (ITO)/Zn{sub 1−x}Co{sub x}O/ITO transparent resistive memory devices were investigated. An appropriate amount of cobalt dopant in ZnO resistive layer demonstrated sufficient memory window and switching stability. In contrast, pure ZnO devices demonstrated a poor memory window, and using an excessive dopant concentration led to switching instability. To achieve suitable memory performance, relying only on controlling defect concentrations is insufficient; the grain growth orientation of the resistive layer must also be considered. Stable endurance with an ON/OFF ratio of more than one order of magnitude during 5000 cycles confirmed that the Co-doped ZnO device is a suitable candidate for resistive random access memory application. Additionally, fully transparent devices with a high transmittance of up to 90% at wavelength of 550 nm have been fabricated.

Room temperature ferromagnetism in nano-crystalline Co:ThO2 powders

International Nuclear Information System (INIS)

Bhide, M.K.; Kadam, R.M.; Godbole, S.V.; Tyagi, A.K.; Salunke, H.G.

2012-01-01

The major interest in dilute magnetic semiconductors (DMS's) had been directed towards the synthesis of room temperature ferromagnetic (RTF) materials for their potential applications in spintronic devices. Room temperature (RT) ferromagnetism was initially reported in Co doped TiO 2 , ZnO 2 and SnO 2 thin films and in the recent past in transition metal doped wide band gap materials. In the present paper we report the synthesis of Co doped ThO 2 nano powders by urea combustion method. The XRD characterization of 300℃ annealed samples confirmed formation of ThO 2 in the cubic phase and the average crystallite size obtained using Scherrer's formula was around 6 nm

Effect of co-doping process on topography, optical and electrical properties of ZnO nanostructured

Science.gov (United States)

Mohamed, R.; Mamat, M. H.; Malek, M. F.; Ismail, A. S.; Yusoff, M. M.; Syamsir, S. A.; Khusaimi, Z.; Rusop, M.

2018-05-01

We investigated of Undoped ZnO and Magnesium (Mg)-Aluminium (Al) co-doped Zinc Oxide (MAZO) nanostructured films were prepared by sol gel spin coating technique. The surface topography was analyzed using Atomic Force Microscopy (AFM). Based on the AFM results, Root Mean Square (RMS) of MAZO films have rougher surface compared to pure ZnO films. The optical and electrical properties of thin film samples were characterized using Uv-Vis spectroscopy and two point probes, current-voltage (I-V) measurements. The transmittance spectra for both thin samples was above 80% in the visible wavelength. The MAZO film shows the highest conductivity compared to pure ZnO films. This result indicates that the improvement of carrier mobility throughout doping process and possibly contribute by extra ion charge.

Characterization of Mn doped ZnO nanopowder

Energy Technology Data Exchange (ETDEWEB)

Schlenker, Eva; Bakin, Andrey; Al-Suleiman, Mohamed; Wehmann, Hergo-Heinrich; Waag, Andreas [Institute of Semiconductor Technology, TU Braunschweig (Germany); Schmid, Herbert; Mader, Werner [Institute for Inorganic Chemistry, University Bonn (Germany); Bremers, Heiko; Hangleiter, Andreas [Institute of Applied Physics, TU Braunschweig (Germany)

2008-07-01

In the quest of materials for spintronic applications, diluted magnetic semiconductors recently attracted much attention. The main challenge is finding a ferromagnetic material with Curie temperature T{sub c}>300 K whose magnetic properties can be controlled electrically. The interest was particularly focused on Zn(TM)O since theoretical calculations predict that ZnO containing Mn could exhibit ferromagnetism with T{sub c} above room temperature. In the present study, the structural and magnetic properties of Mn doped ZnO nanopowder are investigated and compared to undoped ZnO crystals. Doping of ZnO with Mn results in increased lattice constants as revealed by XRD. However, an inhomogeneous distribution of the Mn dopants within the nanopowder was revealed by energy-dispersive X-ray and electron energy-loss spectroscopy. Magnetic properties are investigated by means of SQUID measurements on aggregates of powder particles as well as by MFM to study the behavior of single grains. The MFM image differs significantly from the topography as imaged by AFM and suggests the existence of long-ranging magnetic signals emerging from the sample.

Nanoparticles of ZnO doped with Mn: structural and morphological characteristics

Energy Technology Data Exchange (ETDEWEB)

Bonifacio, Maria Aparecida Ribeiro; Lira, Helio de Lucena; Gama, Lucianna, E-mail: m_aparecidaribeiro@yahoo.com.br [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Departamento de Engenharia de Materiais; Neiva, Laedna Souto [Universidade Federal do Cariri (UFCA), Juazeiro do Norte, CE (Brazil). Unidade Academica de Materiais; Kiminami, Ruth H. G. A. [Universidade Federal de Sao Carlos (USCar), SP (Brazil). Departamento de Engenharia de Materiais

2017-07-15

In this study, the effects of dopant concentrations on the structural and morphological characteristics of Zn{sub 1-x}Mn{sub x} O powders (x= 0.025, 0.05, 0.075, and 0.1 mole) synthesized by the Pechini method has been investigated. The powder was characterized by X-ray diffraction (XRD), Brunauer-Emmet-Teller (BET) specific surface, energy dispersive X-ray (EDX), scanning electron microscopy (SEM) and Spectroscopy with Fourier transform (FTIR). An XRD analysis of the powder showed the formation of ZnO phase with a typical single phase wurtzite structure. The EDX analysis revealed Mn incorporated in the ZnO structure. The particle size calculated by BET ranged from 24 to 63 nm, confirming the nanometric size of the powder particles. The SEM analysis revealed irregular shaped particle agglomerates and the presence of nanosheets. From FTIR it was confirmed the wurtzite structure in ZnO and ZnO nanoparticles doped with Mn. (author)

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

Doping effects of Co2+ ions on ZnO nanorods and their photocatalytic properties

International Nuclear Information System (INIS)

Qiu Xiaoqing; Li Guangshe; Sun Xuefei; Li Liping; Fu Xianzhi

2008-01-01

A series of Zn 1-x Co x O nanorods with dopant content ranging from x = 0.00 to 0.10 was prepared by a wet chemical method. All Zn 1-x Co x O samples were investigated by x-ray diffraction, transmission electron microscopy, energy-dispersion x-ray line mapping analysis, and UV-visible absorption spectroscopy. It was found that Co 2+ ions were homogeneously substituted for Zn 2+ ions in ZnO nanorods. Rhodamine B degradation was used as a probe reaction to evaluate the effect of Co 2+ doping on ZnO nanorods and photocatalytic performance under UV light and visible light irradiation. Co 2+ ions acted as the trapping or recombination centers for electrons and holes, leading to a reduction in photodegradation efficiency under UV light illumination. Alternatively, Co 2+ ions enhanced the optical absorption and produced the photoinduced carriers under visible illumination in terms of two charge transfer transitions involving Co 2+ ions. Consequently, Co 2+ ions substituted in the lattice of ZnO nanorods significantly improved the visible light photocatalytic activity

Structural and magnetic properties of Co-doped ZnO thin films grown by ultrasonic spray pyrolysis method

Science.gov (United States)

Baghdad, R.; Lemée, N.; Lamura, G.; Zeinert, A.; Hadj-Zoubir, N.; Bousmaha, M.; Bezzerrouk, M. A.; Bouyanfif, H.; Allouche, B.; Zellama, K.

2017-04-01

Cobalt-doped ZnO thin films with several different percentage of Co from 0 up to 15 at% were synthesized via a cheap, simple and versatile method i.e. ultrasonic spray pyrolysis at atmospheric pressure and a substrate temperature of 350 °C. The structure of the as-prepared samples was characterized by X-ray diffraction (XRD), Raman spectroscopy and FTIR. The Co-doping effect is revealed by the presence of three additional peaks around 235, 470 and 538 cm-1 respect to the Raman spectra of the unsubstituted film. Fourier transform infrared spectroscopy (FTIR) put in evidence the decrease of the bond force constant f with increasing Co-doping. By ultra-violet visible near infrared (UV-Vis-NIR) spectroscopy on Co-doped samples it was possible to show the presence of additional absorption bands at approximately 570, 620 and 660 nm suggesting that Co2+ ions do not change their oxidation when substituted to zinc and the ZnO lattice does not change its wurtzite structure as well. Finally, all our samples exhibit a paramagnetic behavior without any trace of intrinsic room temperature ferromagnetism.

Properties of Mn-doped ZnO nanopowder

Energy Technology Data Exchange (ETDEWEB)

Schlenker, E.; Bakin, A.; Wehmann, H.H.; Al-Suleiman, M.; Waag, A. [Technical University Braunschweig, Institute of Semiconductor Technology, Braunschweig (Germany); Schmid, H.; Mader, W. [Universitaet Bonn, Institut fuer Anorganische Chemie, Bonn (Germany); Bremers, H.; Hangleiter, A. [Technical University Braunschweig, Institute of Applied Physics, Braunschweig (Germany); Luedke, J.; Albrecht, M. [Physikalisch-Technische Bundesanstalt (PTB), Braunschweig (Germany)

2008-06-15

The structural and magnetic properties of Mn-doped ZnO nanopowder are investigated and compared to undoped ZnO crystals. Mn incorporation leads to an increase in the lattice constants as revealed by X-ray diffraction measurements. An inhomogeneous distribution of the Mn atoms within the nanopowder was detected by energy-dispersive X-ray and electron-energy-loss spectroscopy measurements. Magnetic features are investigated by means of SQUID magnetometry on ensembles of powder particles as well as by magnetic force microscopy to study the behavior of single grains. (orig.)

Soft x-ray absorption spectroscopy on Co doped ZnO: structural distortions and electronic structure

International Nuclear Information System (INIS)

Kowalik, I A; Guziewicz, E; Godlewski, M; Arvanitis, D

2016-01-01

We present soft x-ray absorption spectra from a series of Co doped ZnO films. We discuss systematic variations of the Co L-edge white line intensity and multiplet features for this series of samples. We document sizeable differences in the electronic state of the Co ionic cores, as well as in the local environment of the host lattice atoms, characterised by means of x-ray absorption spectra at the O K-edge and Zn L-edges. Model calculations allow to correlate the observed effects to small structural distortions of the ZnO lattice. (paper)

Antibacterial properties of F-doped ZnO visible light photocatalyst

Energy Technology Data Exchange (ETDEWEB)

Podporska-Carroll, Joanna, E-mail: joannapcarroll@gmail.com [Center for Research in Engineering Surface Technology (CREST), DIT FOCAS Institute, Kevin St., Dublin (Ireland); Myles, Adam [Center for Research in Engineering Surface Technology (CREST), DIT FOCAS Institute, Kevin St., Dublin (Ireland); School of Chemical and Pharmaceutical Sciences, Dublin Institute of Technology, Kevin St., Dublin (Ireland); Quilty, Brid [School of Biotechnology, Dublin City University, Dublin (Ireland); McCormack, Declan E.; Fagan, Rachel [Center for Research in Engineering Surface Technology (CREST), DIT FOCAS Institute, Kevin St., Dublin (Ireland); School of Chemical and Pharmaceutical Sciences, Dublin Institute of Technology, Kevin St., Dublin (Ireland); Hinder, Steven J. [The Surface Analysis Laboratory, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom); Dionysiou, Dionysios D., E-mail: dionysios.d.dionysiou@uc.edu [Environmental Engineering and Science Program, Department of Biomedical, Chemical and Environmental Engineering (DBCEE), 705 Engineering Research Center, University of Cincinnati, Cincinnati, OH 45221-0012 (United States); Pillai, Suresh C., E-mail: Pillai.Suresh@itsligo.ie [Center for Research in Engineering Surface Technology (CREST), DIT FOCAS Institute, Kevin St., Dublin (Ireland); Nanotechnology Research Group, Department of Environmental Science, PEM Centre, Institute of Technology Sligo, Sligo (Ireland)

2017-02-15

Highlights: • F doped ZnO nano-powders were obtained by a modified sol–gel method. • These materials were found to be effective against S. aureus and E. coli. • Enhanced visible light photocatalytic and antimicrobial properties were obtained. • The toxic effect of ZnO on bacteria can be due to the release of zinc cations. • Production of reactive oxidation species influences bacterial viability. - Abstract: Nanocrystalline ZnO photocatalysts were prepared by a sol–gel method and modified with fluorine to improve their photocatalytic anti-bacterial activity in visible light. Pathogenic bacteria such as Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) were employed to evaluate the antimicrobial properties of synthesized materials. The interaction with biological systems was assessed by analysis of the antibacterial properties of bacteria suspended in 2% (w/w) powder solutions. The F-doping was found to be effective against S. aureus (99.99% antibacterial activity) and E. coli (99.87% antibacterial activity) when irradiated with visible light. Production of reactive oxygen species is one of the major factors that negatively impact bacterial growth. In addition, the nanosize of the ZnO particles can also be toxic to microorganisms. The small size and high surface-to-volume ratio of the ZnO nanoparticles are believed to play a role in enhancing antimicrobial activity.

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).

Carbon doped ZnO: Synthesis, characterization and interpretation

International Nuclear Information System (INIS)

Mishra, D.K.; Mohapatra, J.; Sharma, M.K.; Chattarjee, R.; Singh, S.K.; Varma, Shikha; Behera, S.N.; Nayak, Sanjeev K.; Entel, P.

2013-01-01

A novel thermal plasma in-flight technique has been adopted to synthesize nanocrystalline ZnO and carbon doped nanocrystalline ZnO matrix. Transmission electron microscopy (TEM) studies on these samples show the average particle sizes to be around 32 nm for ZnO and for carbon doped ZnO. An enhancement of saturation magnetization in nanosized carbon doped ZnO matrix by a factor of 3.8 has been found in comparison to ZnO nanoparticles at room temperature. Raman measurement clearly indicates the presence of Zn–C complexes surrounded by ZnO matrix in carbon doped ZnO. This indicates that the ferromagnetic signature in carbon doped ZnO arises from the creation of defects or the development of oxy-carbon clusters, in the carbon doped ZnO system. Theoretical studies based on density functional theory also support the experimental analyses. - Highlights: ► Synthesis of nanocrystalline ZnO and carbon doped ZnO matrix by inflight thermal plasma reactor. ► Enhancement of ferromagnetism in nanosized carbon doped ZnO in comparison to ZnO nanoparticles. ► Raman measurement indicates the presence of Zn–C complexes surrounded by ZnO matrix. ► Ferromagnetic signature in carbon doped ZnO arises from the development of oxy-carbon clusters. ► DFT supports experimental evidence of ferromagnetism in C doped ZnO nanoparticles.

Effect of Al and Fe doping in ZnO on magnetic and magneto-transport properties

International Nuclear Information System (INIS)

Kumar, Santosh; Deepika; Tripathi, Malvika; Vaibhav, Pratyush; Kumar, Aman; Kumar, Ritesh; Choudhary, R.J.; Phase, D.M.

2016-01-01

The structural, magnetic and magneto-transport of undoped ZnO, Zn_0_._9_7Al_0_._0_3O, Zn_0_._9_5Fe_0_._0_5O and Zn_0_._9_2Al_0_._0_3Fe_0_._0_5O thin films grown on Si(100) substrate using pulsed laser deposition were investigated. The single phase nature of the films is confirmed by X-ray diffraction and Raman spectroscopy measurements. The possibility of Fe metal cluster in Fe doped/co-doped films is ruled out by Fe 2p core level photoelectron spectra. From O 1s core level spectra it is observed that oxygen vacancy is present in all the films. The undoped ZnO film shows magnetic ordering below ∼175 K, whereas Fe doped/codoped samples show magnetic ordering even at 300 K. The Al doped sample reveals paramagnetic behavior. The magneto-transport measurements suggest that the mobile carriers undergo exchange interaction with local magnetic moments. - Highlights: • Al, Fe, Al–Fe co-doped and undoped films of ZnO are deposited on Si by PLD. • Single phase (002) oriented Wurtzite ZnO phase is formed for all films. • Fe doped and Fe–Al co-doped ZnO films reveal magnetic hysteresis at 300 K. • Negative magnetoresistance is observed in undoped and Fe–Al co-doped ZnO film. • It is apparent that charge carriers are coupled with the local magnetic moment.

Effect of Al and Fe doping in ZnO on magnetic and magneto-transport properties

Energy Technology Data Exchange (ETDEWEB)

Kumar, Santosh, E-mail: skphysics@yahoo.co.in [Department of Physics, College of Commerce, Arts & Science, Patna 800020, Bihar (India); Deepika [Department of Physics, College of Commerce, Arts & Science, Patna 800020, Bihar (India); Tripathi, Malvika [UGC DAE, Consortium for scientific research, Indore 452001, Madhya Pradesh (India); Vaibhav, Pratyush [Jaypee University of Engineering and Technology, Guna 473226, Madhya Pradesh (India); Kumar, Aman [Indian Institute of Technology, Roorkee (India); Kumar, Ritesh [Department of Physics, College of Commerce, Arts & Science, Patna 800020, Bihar (India); Choudhary, R.J., E-mail: ram@csr.res.in [UGC DAE, Consortium for scientific research, Indore 452001, Madhya Pradesh (India); Phase, D.M. [UGC DAE, Consortium for scientific research, Indore 452001, Madhya Pradesh (India)

2016-12-01

The structural, magnetic and magneto-transport of undoped ZnO, Zn{sub 0.97}Al{sub 0.03}O, Zn{sub 0.95}Fe{sub 0.05}O and Zn{sub 0.92}Al{sub 0.03}Fe{sub 0.05}O thin films grown on Si(100) substrate using pulsed laser deposition were investigated. The single phase nature of the films is confirmed by X-ray diffraction and Raman spectroscopy measurements. The possibility of Fe metal cluster in Fe doped/co-doped films is ruled out by Fe 2p core level photoelectron spectra. From O 1s core level spectra it is observed that oxygen vacancy is present in all the films. The undoped ZnO film shows magnetic ordering below ∼175 K, whereas Fe doped/codoped samples show magnetic ordering even at 300 K. The Al doped sample reveals paramagnetic behavior. The magneto-transport measurements suggest that the mobile carriers undergo exchange interaction with local magnetic moments. - Highlights: • Al, Fe, Al–Fe co-doped and undoped films of ZnO are deposited on Si by PLD. • Single phase (002) oriented Wurtzite ZnO phase is formed for all films. • Fe doped and Fe–Al co-doped ZnO films reveal magnetic hysteresis at 300 K. • Negative magnetoresistance is observed in undoped and Fe–Al co-doped ZnO film. • It is apparent that charge carriers are coupled with the local magnetic moment.

Spectroscopic investigation of an intrinsic room temperature ferromagnetism in Co doped ZnO nanoparticles

Energy Technology Data Exchange (ETDEWEB)

N, Srinatha [Department of Physics, JB Campus, Bangalore University, Bangalore 560056 (India); Angadi, Basavaraj, E-mail: brangadi@gmail.com [Department of Physics, JB Campus, Bangalore University, Bangalore 560056 (India); Nair, K.G.M. [UGC-DAE-CSR, Kalpakkam Node, Kalpakkam, Kokilamedu 603 102 (India); Deshpande, Nishad G.; Shao, Y.C.; Pong, Way-Faung [Department of Physics, Tamkang University, Tamsui, Taipei 251, Taiwan (China)

2014-08-15

Highlights: • For the first time L-Valine was used as a fuel to synthesize Co:ZnO nanoparticles by solution combustion method. • Single phase and ferromagnetic nature were confirmed through XRD, SQUID, NEXAFS and XMCD. • Through NEXAFS and XMCD, the effect of ‘Co’ substitution at O K-edge, Co L{sub 3,2} edge, Zn L{sub 3,2} edge have been investigated. • Spectral features of NEXAFS and XMCD confirms an intrinsic RTFM by substitution of ‘Co{sup 2+}’ at ‘Zn{sup 2+}’ site and rules out the presence of secondary phases. - Abstract: Pure and Co substituted ZnO nano crystalline particles were prepared by solution combustion technique using L-Valine as a fuel. As synthesized powder samples were characterized by X-ray diffractometer and SQUID magnetometer to confirm the formation of single phase wurtzite structure and to study the bulk magnetic response of the sample, respectively. Magnetic studies show that Co doped ZnO nanoparticles exhibit ferromagnetism (FM) at room temperature (RT). Furthermore, the electronic structure and element specific magnetic properties were investigated by near-edge X-ray absorption fine structure (NEXAFS) and X-ray magnetic circular dichroism (XMCD) measurements, respectively. The effect of Co substitution on the spectral features of Co–ZnO at O K-edge, Co L{sub 3,2} edge, Zn L{sub 3,2} edge have been investigated. The spectral features of NEXAFS at Co L{sub 3,2} edge is entirely different from the spectral features of metallic clusters and other impurity phases, which rules out the presence of impurity phases. The valence state of ‘Co’ ion is found to be in +2 state. The FM nature of the sample was confirmed through XMCD spectra, which is due to the incorporation of divalent ‘Co’ ions. Hence the presented results confirm the substitution of ‘Co’ ions at ‘Zn’ site in the host lattice, which is responsible for the RTFM.

Nature of ferromagnetic coupling in Cobalt-doped ZnO; Ursache der magnetischen Kopplung in Kobalt-dotiertem ZnO

Energy Technology Data Exchange (ETDEWEB)

Nielsen, K W

2007-12-12

Aim of this thesis was on the one hand to produce Co doped ZnO films, which exhibit a ferromagnetic signal and on the other hand to study the cause of the magnetic coupling. For this purpose Zn{sub 0.95}Co{sub 0.05} films wer fabricated by pulsed laser deposition. Three different substrate materials ((0001)ZnO, (0001)Al{sub 2}O{sub 3}, and (0001)ScAlMgO{sub 4}) were applied anf the growth temperature T{sub g} varied between 300 C and 600 C. Furthermore non-transition-metal doped films were grown at T{sub g}=320 C. By means of X-ray diffractometry the samples were studied concerning their structure, phase purity, and mosaicism. In the films on ZnO a foreign phase was detected, which can be explained by metallic Co inclusions. An estimation of the particle sizes yielded diameters between 2.2 nm and 5.4 nm. With SQID magnetometry measurements of the magnetization M were performed in dependence on the magnetic field H and the temperature T. At 300 K in all Co doped samples on ZnO and in samples on Al{sub 2}O{sub 3} and ScAlMgO{sub 4} with T{sub g}<400 C in the M(H) curves a distinct magnetic moment was observed, which cannot be explained by paramagnetic CO{sup 2+}. The magnetization measurements prove the existence of superparamegnetic nanoparticles. By means of high-resolution transmission electron microscopy it was possible to detect the Co inclusions in the Co doped film on ZnO with T{sub g}=500 C. For the Co and the non-transition-metal-doped samples on Al{sub 2}O{sub 3} and ScAlMgO{sub 4} with T{sub g}=320 C the electric trasnport properties were determined in dependence on H and T.

The influence of Co content on the luminescence properties of Co-doped ZnO nanoparticles

Science.gov (United States)

Guo, Shuxia; Jiang, Haitao

2018-04-01

Co-doped ZnO nanoparticles have been synthesized by co-precipitation technique. Photoluminescence spectra change in the range from 350 nm to 600 nm and remain unchanged at about 690 nm with the Co content increase. The UV emission is assigned to exciton emission. The density of band-edge states increases with Co content. The blue emission could be ascribed to the recombination of electrons in Co+ ions and holes in the valence band, whose relative intensity and full-width at half-maximum (FWHM) increase with the increase of cobalt concentration. The red emission results from the intra-d-shell emission at Co, which is independent of Co content. The relative density and energy-level position of green emission centers are also influenced by Co content.

Structural and optical analysis of ZnBeMgO powder and thin films

International Nuclear Information System (INIS)

Panwar, Neeraj; Liriano, J.; Katiyar, Ram S.

2011-01-01

Research highlights: → Structural and optical studies of Zn 1-x-y Be x Mg y O (0 ≤ x ≤0.10; 0 ≤ y ≤ 0.20) powders and thin films. → Raman studies of the pure ZnO powder showed all the characteristic peaks of the wurtzite hexagonal structure and with (Be, Mg) co-doping new modes appeared which can be attributed to arise as a result of doping effect. → The XRD of the films prepared from the powders using pulsed laser deposition (PLD) technique exhibited the preferential orientation and with doping the (0 0 0 2) peak also shifts to higher 2θ values suggesting the incorporation of Be/Mg at the Zn-site. → From the UV-visible optical band gap measurement it was noticed that the band gap of the pristine ZnO film is 3.3 eV which enhanced up to 4.51 eV for Zn 0.7 Be 0.1 Mg 0.2 O film which lies in the solar blind region and is very useful for the deep UV detection. - Abstract: We here report the structural and optical studies of Zn 1-x-y Be x Mg y O (0 ≤ x ≤ 0.15; 0 ≤ y ≤ 0.20) powders and thin films. From the Rietveld refinement of the powder X-ray diffraction (XRD) patterns it was revealed that the value of 'a' lattice parameter remains almost unchanged whereas 'c' parameter reduces with Be and Mg co-doping in ZnO. The Zn-O bond length also decreases in co-doped samples. Raman studies of the pure ZnO powder showed all the characteristic peaks of the wurtzite hexagonal structure and with (Be, Mg) co-doping new modes appeared which can be attributed to arise as a result of substitution. The XRD of the films prepared from the powders using pulsed laser deposition (PLD) technique exhibited the preferential orientation and with increase in co-doping the (0 0 0 2) peak also shifts to higher 2θ values suggesting the incorporation of Be/Mg at the Zn-site. From the UV-visible optical transmittance measurement it was noticed that the band gap of the pristine ZnO film is 3.3 eV which enhanced up to 4.51 eV for Zn 0.7 Be 0.1 Mg 0.2 O film which lies in the

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

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Shibu Saha

2011-12-01

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

Intrinsic and spatially nonuniform ferromagnetism in Co-doped ZnO films

Science.gov (United States)

Tseng, L. T.; Suter, A.; Wang, Y. R.; Xiang, F. X.; Bian, P.; Ding, X.; Tseng, A.; Hu, H. L.; Fan, H. M.; Zheng, R. K.; Wang, X. L.; Salman, Z.; Prokscha, T.; Suzuki, K.; Liu, R.; Li, S.; Morenzoni, E.; Yi, J. B.

2017-09-01

Co doped ZnO films have been deposited by a laser-molecular beam epitaxy system. X-ray diffraction and UV spectra analysis show that Co effectively substitutes the Zn site. Transmission electron microscopy (TEM) and secondary ion mass spectroscopy analysis indicate that there are no clusters. Co dopants are uniformly distributed in ZnO film. Ferromagnetic ordering is observed in all samples deposited under an oxygen partial pressure, PO2=10-3 , 10-5, and 10-7 torr, respectively. However, the magnetization of PO2=10-3 and 10-5 is very small at room temperature. At low temperature, the ferromagnetic ordering is enhanced. Muon spin relaxation (μ SR ) measurements confirm the ferromagnetism in all samples, and the results are consistent with magnetization measurements. From μ SR and TEM analysis, the film deposited under PO2=10-7 torr shows intrinsic ferromagnetism. However, the volume fraction of the ferromagnetism phase is approximately 70%, suggesting that the ferromagnetism is not carrier mediated. Resistivity versus temperature measurements indicate Efros variable range hopping dominates the conductivity. From the above results, we can confirm that a bound magnetic polaron is the origin of the ferromagnetism.

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.

Sulfur and Nitrogen co-doped graphene quantum dot decorated ZnO nanorod/polymer hybrid flexible device for photosensing applications

Energy Technology Data Exchange (ETDEWEB)

Hmar, Jehova Jire L.; Majumder, Tanmoy; Dhar, Saurab; Mondal, Suvra Prakash, E-mail: suvraphy@gmail.com

2016-08-01

S and N co-doped graphene quantum dots (S,N-GQDs) have been synthesized by a hydrothermal process. S,N-GQDs are made up of 1–5 monolayer of graphene with average diameter 13.3 nm. The absorption peaks at 336 and 621 nm, are attributed to n → Π{sup ⁎} transitions of electrons in C=O and S=O bonds, respectively. S,N-GQDs are highly luminescent and showed excitation dependent emission behaviors. Hybrid photosensing device has been fabricated with S,N-GQD sensitized ZnO nanorods and a conjugated polymer poly(3-hexylthiophene) (P3HT). S,N-GQD decorated ZnO nanorod demonstrated higher photoresponse compared to pristine ZnO nanorod based device. S,N-GQD/ZnO nanorod hybrid device showed superior incident photon to electron conversion efficiency (IPCE), photoresponsivity and detectivity compared to the control samples. The flexibility study of the samples has been monitored by measuring current-voltage characteristics at different bending angles. - Highlights: • S and N co-doped graphene quantum dots (S,N-GQDs) were synthesized. • ZnO nanorods were grown on ITO coated flexible PET substrates. • S,N-GQDs were attached with ZnO nanorods and used as a green sensitizer. • Photosensing properties of S,N-GQD/ZnO and P3HT polymer hybrid device was studied.

Formation of p-type ZnO thin film through co-implantation

Science.gov (United States)

Chuang, Yao-Teng; Liou, Jhe-Wei; Woon, Wei-Yen

2017-01-01

We present a study on the formation of p-type ZnO thin film through ion implantation. Group V dopants (N, P) with different ionic radii are implanted into chemical vapor deposition grown ZnO thin film on GaN/sapphire substrates prior to thermal activation. It is found that mono-doped ZnO by N+ implantation results in n-type conductivity under thermal activation. Dual-doped ZnO film with a N:P ion implantation dose ratio of 4:1 is found to be p-type under certain thermal activation conditions. Higher p-type activation levels (1019 cm-3) under a wider thermal activation range are found for the N/P dual-doped ZnO film co-implanted by additional oxygen ions. From high resolution x-ray diffraction and x-ray photoelectron spectroscopy it is concluded that the observed p-type conductivities are a result of the promoted formation of PZn-4NO complex defects via the concurrent substitution of nitrogen at oxygen sites and phosphorus at zinc sites. The enhanced solubility and stability of acceptor defects in oxygen co-implanted dual-doped ZnO film are related to the reduction of oxygen vacancy defects at the surface. Our study demonstrates the prospect of the formation of stable p-type ZnO film through co-implantation.

Magnetic properties of sol-gel synthesized C-doped ZnO nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Dung, Nguyen Duc, E-mail: dung.nguyenduc@hust.edu.vn [Advanced Institute of Science and Technology (AIST), Hanoi University of Science and Technology, No.1 Dai Co Viet, Hanoi (Viet Nam); Son, Cao Thai; Loc, Pham Vu; Cuong, Nguyen Huu; Kien, Pham The; Huy, Pham Thanh [Advanced Institute of Science and Technology (AIST), Hanoi University of Science and Technology, No.1 Dai Co Viet, Hanoi (Viet Nam); Ha, Ngo Ngoc [International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology, No.1 Dai Co Viet, Hanoi (Viet Nam)

2016-05-25

ZnO doping with Carbon (C-doped ZnO) materials were prepared by sol-gel technique following with a heat treatment process. Single phase of Wurtzite crystal structure of ZnO was concluded via x-ray diffraction (XRD) with a large amount of excess C tracking by energy dispersive X-ray spectroscopy (EDX) analysis. Two types of ZnO crystals (twinning particles) with different grain sizes and shapes were identified via scanning electron microscopy (FE-SEM). The first type has a smaller grain size of about 20 nm and hexagonal shape. And the second type has a larger grain size of about 80–120 nm and round shape. C substitutions of both Zn and O sites to form C–O and C–Zn bonds were conclusively confirmed via x-ray photoelectron spectroscope (XPS). Experimental evidences for the co-existence of different ferromagnetic phases in the materials are reported and discussed. Two Curie points at high temperatures (>500 °C) are presented. A metamagnetic transition was observed at magnetic field H = 19.2 kOe which was related to the co-existence of ferromagnetic phases. These involve in the formation of twinning C-doped ZnO nanoparticles. - Highlights: • Formation of sol-gel prepared single phase wurtzite ZnO nanoparticles. • Two morphological C-doped ZnO nanoparticles of different grain sizes. • The room temperature ferromagnetism. • An abnormal metamagnetic transition at magnetic field H = 19.2 kOe. • Two different Curie points (T{sub C}) at 500–600 °C.

Relative Humidity Sensing Properties Of Cu2O Doped ZnO Nanocomposite

International Nuclear Information System (INIS)

Pandey, N. K.; Tiwari, K.; Tripathi, A.; Roy, A.; Rai, A.; Awasthi, P.

2009-01-01

In this paper we report application of Cu 2 O doped ZnO composite prepared by solid state reaction route as humidity sensor. Pellet samples of ZnO-Cu 2 O nanocrystalline powders with 2, 5 and 10 weight% of Cu 2 O in ZnO have been prepared. Pellets have been annealed at temperatures of 200-500 deg. C and exposed to humidity. It is observed that as relative humidity increases, resistance of the pellet decreases for the humidity from 10% to 90%. Sample with 5% of Cu 2 O doped in ZnO and annealed at 500 deg. C shows best results with sensitivity of 1.50 MΩ/%RH. In this case the hysteresis is low and the reproducibility high, making it the suitable candidate for humidity sensing.

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.

Theoretical study of the multiferroic properties in M-doped (M=Co, Cr, Mg) ZnO thin films

Energy Technology Data Exchange (ETDEWEB)

Bahoosh, S.G. [Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle (Germany); Apostolov, A.T. [University of Architecture, Civil Engineering and Geodesy, Faculty of Hydrotechnics, Department of Physics, 1, Hristo Smirnenski Blvd., 1046 Sofia (Bulgaria); Apostolova, I.N. [University of Forestry, Faculty of Forest Industry, 10, Kl. Ohridsky Blvd., 1756 Sofia (Bulgaria); Trimper, S. [Institute of Physics, Martin-Luther-University, D-06099 Halle (Germany); Wesselinowa, Julia M. [University of Sofia, Department of Physics, Blvd. J. Bouchier 5, 1164 Sofia (Bulgaria)

2015-01-01

The origin of multiferroism is still an open problem in ZnO. We propose a microscopic model to clarify the occurrence of multiferroism in this material. Using Green's function technique we study the influence of ion doping and size effects on the magnetization and polarization of ZnO thin films. The calculations for magnetic Co- and Cr-ions are based on the s–d model, the transverse Ising model in terms of pseudo-spins and a biquadratic magnetoelectric coupling, whereas in case of nonmagnetic Mg-ions the model takes into account the Coulomb interaction and an indirect coupling between the pseudo-spins via the conduction electrons. We show that the magnetization M exhibits a maximum for a fixed concentration of the doping ions. Furthermore M increases with decreasing film thickness N. The polarization increases with increasing concentration of the dopant and decreasing N. The results are in good agreement with the experimental data. - Highlights: • The paper analyzes the multiferroic properties of doped ZnO thin films by a microscopic model. • The magnetization exhibits a maximum at a fixed doping concentration. • The polarization increases with growing dopant concentration. • The ferroelectric transition temperature is enhanced for increasing dopant concentration.

Influence of Al doping on structural and optical properties of Mg–Al co-doped ZnO thin films prepared by sol–gel method

International Nuclear Information System (INIS)

Fang, Dongyu; Lin, Kui; Xue, Tao; Cui, Can; Chen, Xiaoping; Yao, Pei; Li, Huijun

2014-01-01

Highlights: • Mg–Al co-doped ZnO thin films were prepared by sol–gel spin coating method. • The effects of Al doping on structural and optical properties of AMZO thin films were investigated. • The EDS spectra confirmed presence of Mg and Al elements in AMZO thin films. • The optical band gap of AMZO thin films increased with Al doping concentration increased. • The origin of the photoluminescence emissions was discussed. -- Abstract: Mg–Al co-doped ZnO (AMZO) thin films were successfully deposited onto quartz glass substrates by sol–gel spin coating method. The structure, surface morphology, composition, optical transmittance, and photoluminescence properties of AMZO thin films were characterized through X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy, UV–VIS–NIR spectrophotometry, and fluorescence spectrophotometry. The results indicated that AMZO thin films exhibited preferred orientation growth along the c-axis, and the full width at half maximum of the (0 0 2) diffraction peak decreased first and subsequently increased, reaching a minimum of approximately 0.275° at 3% Al content. The calculated crystallite size increased from 30.21 nm to 40.73 nm. Al doping content increased from 1% to 3% and subsequently reached 19.33 nm for Al doping content at 5%. The change in lattice parameters was demonstrated by the c/a ratio, residual stress, bond length, and volume per unit cell. EDS analysis confirmed the presence of Mg and Al elements in ZnO thin films. The atomic percentage of Mg and Al elements was nearly equal to their nominal stoichiometry within the experimental error. In addition, the optical transmittance of AMZO thin films was over 85% in the visible region, and the optical band gap increased with increasing Al doping concentration. Room temperature photoluminescence showed ultraviolet emission peak and defect emission peak. The defect emission peak of

Microstructure and magnetic properties of Co-doped ZnO films deposited by gas flow sputtering

Energy Technology Data Exchange (ETDEWEB)

Sakuma, H., E-mail: hsakuma@cc.utsunomiya-u.ac.jp [Research Division of Functional Materials Design, Utsunomiya University, 7-1-2 Yoto, Utsunomiya 321-8585 (Japan); Watanabe, Y. [Research Division of Functional Materials Design, Utsunomiya University, 7-1-2 Yoto, Utsunomiya 321-8585 (Japan); Aramaki, K.; Yun, K.S. [Sony Chemical and Information Device Corporation, 1078 Kamiishikawa, Kanuma 322-8503 (Japan); Ishii, K. [Research Division of Functional Materials Design, Utsunomiya University, 7-1-2 Yoto, Utsunomiya 321-8585 (Japan); Ikeda, Y.; Kondo, H. [Sony Chemical and Information Device Corporation, 1078 Kamiishikawa, Kanuma 322-8503 (Japan)

2010-10-15

Co-doped ZnO films with a Co concentration of 8-20 at.% were fabricated using the low-energy process of gas flow sputtering. X-ray diffraction, X-ray photoelectron spectroscopy, and optical absorption measurements revealed that the Co ions replace Zn ions in the ZnO matrix and that the Co ions have an oxidation state of 2+. The magnetic properties of the film depend on the Co concentration. The plots of magnetization and inverse susceptibility vs. temperature indicate that the film with a high Co concentration (20 at.%) contains a ferromagnetic component, while that with a low Co concentration (8 at.%) contains an antiferromagnetic component. The film with an intermediate Co concentration (10 at.%) contains a ferromagnetic component with a low Curie temperature. Hysteresis was not found in magnetization curves for all the samples, including the sample at 5 K. The films exhibited a high resistivity of 4 x 10{sup 7}-2 x 10{sup 8} {Omega} cm at room temperature, and carrier-mediated magnetism is not likely to be applicable for the mechanisms of the magnetism in the films.

Microstructure and magnetic properties of Co-doped ZnO films deposited by gas flow sputtering

International Nuclear Information System (INIS)

Sakuma, H.; Watanabe, Y.; Aramaki, K.; Yun, K.S.; Ishii, K.; Ikeda, Y.; Kondo, H.

2010-01-01

Co-doped ZnO films with a Co concentration of 8-20 at.% were fabricated using the low-energy process of gas flow sputtering. X-ray diffraction, X-ray photoelectron spectroscopy, and optical absorption measurements revealed that the Co ions replace Zn ions in the ZnO matrix and that the Co ions have an oxidation state of 2+. The magnetic properties of the film depend on the Co concentration. The plots of magnetization and inverse susceptibility vs. temperature indicate that the film with a high Co concentration (20 at.%) contains a ferromagnetic component, while that with a low Co concentration (8 at.%) contains an antiferromagnetic component. The film with an intermediate Co concentration (10 at.%) contains a ferromagnetic component with a low Curie temperature. Hysteresis was not found in magnetization curves for all the samples, including the sample at 5 K. The films exhibited a high resistivity of 4 x 10 7 -2 x 10 8 Ω cm at room temperature, and carrier-mediated magnetism is not likely to be applicable for the mechanisms of the magnetism in the films.

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.

Doping of ZnO with Mn or Co: Two different behaviours for the same synthesis approach

Directory of Open Access Journals (Sweden)

Peiteado, M.

2010-02-01

Full Text Available In the last years the research in ZnO has seen a period of intensive work which can be attributed to the new available synthesis methods and characterization techniques. New potential applications have thus emerged for ZnO-based ceramics, provided that a stable and reproducible doping would be achieved. However this still represents a major challenge. In this new trend, Mn and Co represent a couple of interesting candidates for the obtaining of new ZnO-doped structures. But although a lot of work has been done in the past with both systems, a detailed analysis of the specialized literature yet reveals a worrisome lack of knowledge about these materials. In the present contribution the diffusion behavior and the solid state reactivity of both Zn-Mn-O and Zn-Co-O systems is analyzed in order to determine the possibility of obtaining a homogeneous doping of ZnO. The obtained results indicate that, whereas a stable Co:ZnO solid solution is easily attainable, the achievement of a homogeneous Mn:ZnO solid solution would be restricted to severe experimental conditions that limit its application for practical purposes.

En los últimos años, la investigación entorno al ZnO ha experimentado un periodo de intensa labor que bien puede atribuirse a los nuevos métodos de síntesis y a las nuevas técnicas de caracterización disponibles. En consecuencia han surgido nuevas aplicaciones potenciales para los materiales basados en ZnO, siempre y cuando se alcance un dopado estable y reproducible del cerámico. Sin embargo, esto es algo que todavía supone un serio reto. Dentro de esta nueva tendencia, el Mn y el Co representan un par de candidatos interesantes para la obtención de nuevas estructuras de ZnO dopado. Sin embargo, aunque se ha trabajado con ambos sistemas desde hace bastante tiempo, lo cierto es que un análisis detallado de la literatura especializada de los últimos años todavía revela un serio desconocimiento entorno a dichos

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.

In vitro antibacterial activity of ZnO and Nd doped ZnO nanoparticles against ESBL producing Escherichia coli and Klebsiella pneumoniae

Science.gov (United States)

Hameed, Abdulrahman Syedahamed Haja; Karthikeyan, Chandrasekaran; Ahamed, Abdulazees Parveez; Thajuddin, Nooruddin; Alharbi, Naiyf S.; Alharbi, Sulaiman Ali; Ravi, Ganasan

2016-04-01

Pure ZnO and Neodymium (Nd) doped ZnO nanoparticles (NPs) were synthesized by the co-precipitation method. The synthesized nanoparticles retained the wurtzite hexagonal structure. From FESEM studies, ZnO and Nd doped ZnO NPs showed nanorod and nanoflower like morphology respectively. The FT-IR spectra confirmed the Zn-O stretching bands at 422 and 451 cm-1 for ZnO and Nd doped ZnO NPs respectively. From the UV-VIS spectroscopic measurement, the excitonic peaks were found around 373 nm and 380 nm for the respective samples. The photoluminescence measurements revealed that the broad emission was composed of ten different bands due to zinc vacancies, oxygen vacancies and surface defects. The antibacterial studies performed against extended spectrum β-lactamases (ESBLs) producing strains of Escherichia coli and Klebsiella pneumoniae showed that the Nd doped ZnO NPs possessed a greater antibacterial effect than the pure ZnO NPs. From confocal laser scanning microscopic (CLSM) analysis, the apoptotic nature of the cells was confirmed by the cell shrinkage, disorganization of cell wall and cell membrane and dead cell of the bacteria. SEM analysis revealed the existence of bacterial loss of viability due to an impairment of cell membrane integrity, which was highly consistent with the damage of cell walls.

A dual-colored bio-marker made of doped ZnO nanocrystals

Energy Technology Data Exchange (ETDEWEB)

Wu, Y L; Zeng, X T [Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, 638075 (Singapore); Fu, S; Kwek, L C [National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, 637616 (Singapore); Tok, A I Y; Boey, F C Y [School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore); Lim, C S [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore)

2008-08-27

Bio-compatible ZnO nanocrystals doped with Co, Cu and Ni cations, surface capped with two types of aminosilanes and titania are synthesized by a soft chemical process. Due to the small particle size (2-5 nm), surface functional groups and the high photoluminescence emissions at the UV and blue-violet wavelength ranges, bio-imaging on human osteosarcoma (Mg-63) cells and histiocytic lymphoma U-937 monocyte cells showed blue emission at the nucleus and bright turquoise emission at the cytoplasm simultaneously. This is the first report on dual-color bio-images labeled by one semiconductor nanocrystal colloidal solution. Bright green emission was detected on mung bean seedlings labeled by all the synthesized ZnO nanocrystals. Cytotoxicity tests showed that the aminosilanes capped nanoparticles are non-toxic. Quantum yields of the nanocrystals varied from 79% to 95%. The results showed the potential of the pure ZnO and Co-doped ZnO nanocrystals for live imaging of both human cells and plant systems.

Influence of doping of Mn{sup +2} and Co{sup +2} in ZnO synthesized by combustion reaction for use in DMS; Influencia da dopagem do Mn{sup +2} e Co{sup +2} no ZnO sintetizado por reacao de combustao para uso em SMD

Energy Technology Data Exchange (ETDEWEB)

Torquato, R.; Costa, A.C.F.M. [Universidade Federal de Campina Grande (UFCG), Campina Grande, PB (Brazil). Departamento de Engenharia de Materiais; Shirsath, S.E. [Department of Physics, Vivekanand College, Aurangabad, MS (India); Kiminami, R.H.A. [Universidade Federal de Sao Carlos (UFSCar), SP (Brazil). Departamento de Engenharia de Materiais

2011-07-01

ZnO is a semiconducting ceramics used for development of electrical devices such as varistors, chemical sensors, piezoelectric transducers and diluted magnetic semiconductors. So this paper proposes to investigate the influence of doping of 0.1 mol of Mn{sup +2} and Co{sup +2} on the structure, morphology and magnetic measurements of ZnO synthesized by combustion reaction in DMS applications. The resulting samples were characterized by XRD, SEM, BET, VSM. The combustion temperature for samples doped with Mn and Co were 512 deg C and 397 °C, respectively. XRD results for both samples showed the formation of ZnO as the major phase, with crystallite size of 21nm and 23nm and a surface area of 59 and 17 m2/g for samples doped with Mn{sup +2} and Co{sup +2}, respectively. The magnetic measurements showed values of saturation magnetization and coercive force of 12 and 3 emu/g, and 94 and 237Oe, respectively. (author)

Doping effect on the optical properties of ZnO nanostructures

Energy Technology Data Exchange (ETDEWEB)

Stoehr, M. [Frederick Seitz Materials Research Laboratory, University of Illinois,104 South Goodwin Avenue, Urbana, IL 61801 (United States); Institut Universitaire de Technologie, Universite de Haute Alsace, 61 rue Albert Camus, 68093 Mulhouse Cedex (France); Juillaguet, S. [Groupe d' Etude des Semi-conducteurs, Universite Montpellier II, Place Eugene Bataillon, 34095 Montpellier Cedex 5 (France); Kyaw, T.M.; Wen, J.G. [Institut Universitaire de Technologie, Universite de Haute Alsace, 61 rue Albert Camus, 68093 Mulhouse Cedex (France)

2007-04-15

High quality undoped and Ga{sub 2}O{sub 3} or In{sub 2}O{sub 3} doped ZnO nanostructures are grown by chemical vapor transport and condensation. The doping effect on the optical properties is investigated by photoluminescence. At room temperature, photoluminescence on Ga{sub 2}O{sub 3} doped ZnO nanostructures reveals an enhancement of the ultraviolet near band edge emission at 390 nm, while the intensity of the deep level emission at 530 nm weakens. At 5 K, an intense neutral-donor-bound exciton (D{sup 0}X) line dominates the undoped and doped ZnO photoluminescence spectra. The presence of well resolved two-electron satellite lines allow to determine the type of donors. At 5 K, the results indicate that ZnO nanostructures grown with 10% of Ga{sub 2}O{sub 3} display an excellent optical quality, proved by an intense D{sup 0}X line, a high intensity ratio between the D{sup 0}X line and the deep level emission as well as the presence of numerous phonon replicas of the main lines. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Al-doped ZnO nanofilms: Synthesis and characterization

Energy Technology Data Exchange (ETDEWEB)

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

2010-12-15

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

Defects induced ferromagnetism in Mn doped ZnO

Energy Technology Data Exchange (ETDEWEB)

Chattopadhyay, S.; Neogi, S.K. [Department of Physics, University of Calcutta, 92A P C Road, Kolkata 700009 (India); Sarkar, A. [Department of Physics, Bangabasi Morning College, Kolkata 700009 (India); Mukadam, M.D.; Yusuf, S.M. [Solid State Physics Division, Bhaba Atomic Research Centre, Mumbai 400085 (India); Banerjee, A. [Department of Physics, University of Calcutta, 92A P C Road, Kolkata 700009 (India); Bandyopadhyay, S., E-mail: sbaphy@caluniv.ac.i [Department of Physics, University of Calcutta, 92A P C Road, Kolkata 700009 (India)

2011-02-15

Single phase Mn doped (2 at%) ZnO samples have been synthesized by the solid-state reaction technique. Before the final sintering at 500 {sup o}C, the mixed powders have been milled for different milling periods (6, 24, 48 and 96 h). The grain sizes of the samples are very close to each other ({approx}32{+-}4 nm). However, the defective state of the samples is different from each other as manifested from the variation of magnetic properties and electrical resistivity with milling time. All the samples have been found to be ferromagnetic with clear hysteresis loops at room temperature. The maximum value for saturation magnetization (0.11 {mu}{sub B}/Mn atom) was achieved for 96 h milled sample. Electrical resistivity has been found to increase with increase in milling time. The most resistive sample bears the largest saturation magnetization. Variation of average positron lifetime with milling time bears a close similarity with that of the saturation magnetization. This indicates the key role played by open volume vacancy defects, presumably zinc vacancies near grain surfaces, in inducing ferromagnetic order in Mn doped ZnO. To attain optimum defect configuration favorable for ferromagnetism in this kind of samples proper choice of milling period and annealing conditions is required. - Research highlights: 2 at% Mn doped ZnO samples are single phase. All the samples exhibit ferromagnetism at room temperature. Correlation between saturation magnetization and positron annihilation lifetime established.

Defects induced ferromagnetism in Mn doped ZnO

International Nuclear Information System (INIS)

Chattopadhyay, S.; Neogi, S.K.; Sarkar, A.; Mukadam, M.D.; Yusuf, S.M.; Banerjee, A.; Bandyopadhyay, S.

2011-01-01

Single phase Mn doped (2 at%) ZnO samples have been synthesized by the solid-state reaction technique. Before the final sintering at 500 o C, the mixed powders have been milled for different milling periods (6, 24, 48 and 96 h). The grain sizes of the samples are very close to each other (∼32±4 nm). However, the defective state of the samples is different from each other as manifested from the variation of magnetic properties and electrical resistivity with milling time. All the samples have been found to be ferromagnetic with clear hysteresis loops at room temperature. The maximum value for saturation magnetization (0.11 μ B /Mn atom) was achieved for 96 h milled sample. Electrical resistivity has been found to increase with increase in milling time. The most resistive sample bears the largest saturation magnetization. Variation of average positron lifetime with milling time bears a close similarity with that of the saturation magnetization. This indicates the key role played by open volume vacancy defects, presumably zinc vacancies near grain surfaces, in inducing ferromagnetic order in Mn doped ZnO. To attain optimum defect configuration favorable for ferromagnetism in this kind of samples proper choice of milling period and annealing conditions is required. - Research highlights: → 2 at% Mn doped ZnO samples are single phase. → All the samples exhibit ferromagnetism at room temperature. → Correlation between saturation magnetization and positron annihilation lifetime established.

Influences of Co doping on the structural and optical properties of ZnO nanostructured

Science.gov (United States)

Majeed Khan, M. A.; Wasi Khan, M.; Alhoshan, Mansour; Alsalhi, M. S.; Aldwayyan, A. S.

2010-07-01

Pure and Co-doped ZnO nanostructured samples have been synthesized by a chemical route. We have studied the structural and optical properties of the samples by using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), field-emission transmission electron microscope (FETEM), energy-dispersive X-ray (EDX) analysis and UV-VIS spectroscopy. The XRD patterns show that all the samples are hexagonal wurtzite structures. Changes in crystallite size due to mechanical activation were also determined from X-ray measurements. These results were correlated with changes in particle size followed by SEM and TEM. The average crystallite sizes obtained from XRD were between 20 to 25 nm. The TEM images showed the average particle size of undoped ZnO nanostructure was about 20 nm whereas the smallest average grain size at 3% Co was about 15 nm. Optical parameters such as absorption coefficient ( α), energy band gap ( E g ), the refractive index ( n), and dielectric constants ( σ) have been determined using different methods.

Effect of iron doping concentration on magnetic properties of ZnO nanoparticles

International Nuclear Information System (INIS)

Sharma, Prashant K.; Dutta, Ranu K.; Pandey, Avinash C.; Layek, Samar; Verma, H.C.

2009-01-01

The ZnO:Fe nanoparticles of mean size 3-10 nm were synthesized at room temperature by simple co-precipitation method. The crystallite structure, morphology and size estimation were performed by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM). The wurtzite structure of ZnO gradually degrades with the increasing Fe doping concentration. The magnetic behavior of the nanoparticles of ZnO with varying Fe doping concentration was investigated using a vibrating sample magnetometer (VSM). Initially these nanoparticles showed strong ferromagnetic behavior, however at higher doping percentage of Fe, the ferromagnetic behavior was suppressed and paramagnetic nature was observed. The enhanced antiferromagnetic interaction between neighboring Fe-Fe ions suppressed the ferromagnetism at higher doping concentrations of Fe. Room-temperature Moessbauer spectroscopy investigation showed Fe 3+ nature of the iron atom in ZnO matrix.

Dopants incorporation in ZnO mechanical milled powders sensed by positrons

International Nuclear Information System (INIS)

Damonte, L. C.; Donderis, V.; Hernandez Fenollosa, M. A.

2007-01-01

M-doped ZnO (M: Cd, Mg) powders obtained by mechanical milling were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and positron lifetime annihilation spectroscopy (PALS). The mixing of the oxides is followed by means of XRD and SEM. As milling proceeds, a clear reduction of grain size and homogenization are observed. The evolution of annihilation parameters with milling time and cation content were analyzed and related with the kind of mechanical induced defect involved. Ternary oxides Zn 1-x M x O were efficiency obtained for certain compositions. The results showed that positrons constitute a well suited probe to characterize the cation substitution in the ZnO oxide lattice.

Dopants incorporation in ZnO mechanical milled powders sensed by positrons

Energy Technology Data Exchange (ETDEWEB)

Damonte, L. C., E-mail: damonte@fisica.unlp.edu.ar; Donderis, V.; Hernandez Fenollosa, M. A. [Universidad Politecnica de Valencia, Departamento de Fisica Aplicada (Spain)

2007-09-15

M-doped ZnO (M: Cd, Mg) powders obtained by mechanical milling were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and positron lifetime annihilation spectroscopy (PALS). The mixing of the oxides is followed by means of XRD and SEM. As milling proceeds, a clear reduction of grain size and homogenization are observed. The evolution of annihilation parameters with milling time and cation content were analyzed and related with the kind of mechanical induced defect involved. Ternary oxides Zn{sub 1-x}M{sub x}O were efficiency obtained for certain compositions. The results showed that positrons constitute a well suited probe to characterize the cation substitution in the ZnO oxide lattice.

Thermal growth and cathodoluminescence of Bi doped ZnO nanowires and rods

International Nuclear Information System (INIS)

Aleman, B; Hidalgo, P; Fernandez, P; Piqueras, J

2009-01-01

Bi doped ZnO nanowires and rods have been grown by a catalyst free evaporation-deposition method with precursors containing either ZnO and Bi 2 O 3 or ZnS and Bi 2 O 3 powders. The use of ZnS as a precursor was found to lead to a higher density of nano- and microstructures at lower temperatures than by using ZnO. Energy dispersive x-ray spectroscopy (EDS) shows that the Bi content in the wires and rods is in the range 0.15-0.35 at%. Bi incorporation was found to induce a red shift of the near band gap luminescence but no quantitative correlation between the shift and the amount of Bi, as measured by EDS, was observed. The I-V curves of single Bi doped wires had linear behaviour at low current and non-linear behaviour for high currents, qualitatively similar to that of undoped wires.

Thermal growth and cathodoluminescence of Bi doped ZnO nanowires and rods

Energy Technology Data Exchange (ETDEWEB)

Aleman, B; Hidalgo, P; Fernandez, P; Piqueras, J, E-mail: balemanl@fis.ucm.e [Departamento de Fisica de Materiales, Facultad de Ciencias FIsicas, Universidad Complutense de Madrid, 28040 Madrid (Spain)

2009-11-21

Bi doped ZnO nanowires and rods have been grown by a catalyst free evaporation-deposition method with precursors containing either ZnO and Bi{sub 2}O{sub 3} or ZnS and Bi{sub 2}O{sub 3} powders. The use of ZnS as a precursor was found to lead to a higher density of nano- and microstructures at lower temperatures than by using ZnO. Energy dispersive x-ray spectroscopy (EDS) shows that the Bi content in the wires and rods is in the range 0.15-0.35 at%. Bi incorporation was found to induce a red shift of the near band gap luminescence but no quantitative correlation between the shift and the amount of Bi, as measured by EDS, was observed. The I-V curves of single Bi doped wires had linear behaviour at low current and non-linear behaviour for high currents, qualitatively similar to that of undoped wires.

Investigation on structural and electrical properties of Fe doped ZnO nanoparticles synthesized by solution combustion method

International Nuclear Information System (INIS)

Ram, Mast; Bala, Kanchan; Sharma, Hakikat; Kumar, Arun; Negi, N. S.

2016-01-01

In the present study, nanoparticles of Fe doped zinc oxide (ZnO) [Zn_1_-_xFe_xO where x=0.0, 0.01, 0.02, 0.03 and 0.05] were prepared by cost effective solution combustion method. The powder X-ray diffractometry confirms the formation of single phase wurtzite structure. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to investigate the micrsostructure of Fe-doped ZnO nanoparticles. The DC electrical conductivity was found to increase with temperature and measurement was carried out in the temperature range of 300-473K. DC electrical conductivity increases with temperature and decreases with Fe doping concentration.

Evaluation of gas-sensing properties of ZnO nanostructures electrochemically doped with Au nanophases

Directory of Open Access Journals (Sweden)

Elena Dilonardo

2016-01-01

Full Text Available A one-step electrochemical method based on sacrificial anode electrolysis (SAE was used to deposit stabilized gold nanoparticles (Au NPs directly on the surface of nanostructured ZnO powders, previously synthesized through a sol–gel process. The effect of thermal annealing temperatures (300 and 550 °C on chemical, morphological, and structural properties of pristine and Au-doped ZnO nancomposites (Au@ZnO was investigated. Transmission and scanning electron microscopy (TEM and SEM, as well as X-ray photoelectron spectroscopy (XPS, revealed the successful deposition of nanoscale gold on the surface of spherical and rod-like ZnO nanostructures, obtained after annealing at 300 and 550 °C, respectively. The pristine ZnO and Au@ZnO nanocomposites are proposed as active layer in chemiresistive gas sensors for low-cost processing. Gas-sensing measurements towards NO2 were collected at 300 °C, evaluating not only the Au-doping effect, but also the influence of the different ZnO nanostructures on the gas-sensing properties.

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 ...

Preparation and characterization of electrodeposited ZnO and ZnO:Co nanorod films for heterojunction diode applications

Energy Technology Data Exchange (ETDEWEB)

Caglar, Yasemin, E-mail: yasemincaglar@anadolu.edu.tr [Anadolu University, Science Faculty, Physics Department, Eskisehir (Turkey); Arslan, Andaç [Eskisehir Osmangazi University, Art and Science Faculty, Chemistry Department, Eskisehir (Turkey); Ilican, Saliha [Anadolu University, Science Faculty, Physics Department, Eskisehir (Turkey); Hür, Evrim [Eskisehir Osmangazi University, Art and Science Faculty, Chemistry Department, Eskisehir (Turkey); Aksoy, Seval; Caglar, Mujdat [Anadolu University, Science Faculty, Physics Department, Eskisehir (Turkey)

2013-10-15

Highlights: •Undoped and Co-doped ZnO films were deposited on p-Si by electrodeposition method. •The effects of Co doping on some properties of ZnO films were investigated. •ZnO morphology was converted uniform multi-oriented rods with incorporation of Co. •Co-doped ZnO nanorod films showed a multi-oriented spear-like structure. -- Abstract: Well-aligned undoped and Co-doped nanorod ZnO films were grown by electrochemical deposition onto p-Si substrates from an aqueous route. Aqueous solution of Zn(NO{sub 3}){sub 2}⋅6H{sub 2}O and hexamethylenetetramine (HMT) were prepared using triple distilled water. Two different atomic ratios of Co(NO{sub 3}){sub 2}⋅6H{sub 2}O were used as a dopant element. Electrodepositions were carried out in a conventional three electrode cell for the working electrode (p-Si), reference electrode (Ag/AgCl, sat.) and counter electrode (platin wire). The effects of Co doping on the structural, morphological and electrical properties of ZnO films were investigated. X-ray diffraction (XRD) measurement showed that the undoped ZnO nanorod film was crystallized in the hexagonal wurtzite phase and presented a preferential orientation along the c-axis. Only one peak, corresponding to the (0 0 2) phase, appeared on the diffractograms. The lattice parameters and texture coefficient values were calculated. The nanorods were confirmed by the field emission scanning electron microscopy (FE-SEM) measurements. The FE-SEM image showed that the ZnO nanorods grow uniformly on the substrates, providing a surface with fairly homogeneous roughness. The surface morphology was transformed into uniform multi-oriented rods with incorporation of Co. Co-doped ZnO nanorod films showed a multi-oriented spear-like structure. The diffuse reflectance spectra of the films were measured and the optical band gap values were determined using Kubelka–Munk theory. The van der Pauw method was used to measure the sheet resistance of the films. The sheet resistance

Positron annihilation spectroscopy in doped p-type ZnO

Science.gov (United States)

Majumdar, Sayanee; Sanyal, D.

2011-07-01

Positron annihilation lifetime (PAL) spectroscopy has been used to investigate the vacancy type defect of the Li and N doped ZnO. The mono-vacancies, shallow -vacancies and open volume defects have been found in both the Li and N doped ZnO. The mono-vacancies, shallow-vacancies and open volume defects increase in N-doped ZnO as the size of N is quite high compared to Li. Positron annihilation study showed that the doping above 1-3% Li and 3-4% N in ZnO are not required in order to achieve low resistivity, high hole concentration and good mobility.

Resistive switching: An investigation of the bipolar–unipolar transition in Co-doped ZnO thin films

International Nuclear Information System (INIS)

Santos, Daniel A.A.; Zeng, Hao; Macêdo, Marcelo A.

2015-01-01

Highlights: • A purely bipolar behavior on a Co-doped ZnO thin film has been demonstrated. • We have shown what can happen if a unipolar test is performed in a purely bipolar device. • An explanation for how a sample can show a purely bipolar switching behavior was suggested. • An important open issue about resistive switching effect was put in debate. - Abstract: In order to investigate the resistive switching effect we built devices in a planar structure in which two Al contacts were deposited on the top of the film and separated by a small gap using a shadow mask. Therefore, two samples of 10% Co-doped ZnO thin films were sputtered on glass substrate. High resolution X-ray diffraction (HRXRD) revealed a highly c-axis oriented crystalline structure, without secondary phase. The high resolution scanning electron microscopy (HRSEM) showed a flat surface with good coverage and thickness about 300 nm. A Keithley 2425 semiconductor characterization system was used to perform the resistive switching tests in the bipolar and unipolar modes. Considering only the effect of compliance current (CC), the devices showed a purely bipolar behavior since an increase in CC did not induce a transition to unipolar behavior

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

Directory of Open Access Journals (Sweden)

Min-Kyeong Song

2015-01-01

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

Effect of Co and O defects on ferromagnetism in Co-doped ZnO: An X-ray absorption spectroscopic investigation

Science.gov (United States)

Singhal, Rishi K.; Jakhar, Narendra; Samariya, A.; Dolia, S. N.; Kumar, Sudhish

2018-02-01

Understanding of origin of ferromagnetism in dilute magnetic oxides (DMO's) has become one of the most challenging research problems in condensed matter physics. Here we are reporting a detailed study of magnetic properties and electronic structure of two 5% Co-doped ZnO samples (the as-prepared sample Zn0.95Co0.05O and the hydrogenated sample Zn0.95Co0.05O:H). The as-prepared sample is found to be paramagnetic while through hydrogenation, we observed inducement of remarkable ferromagnetism in it. The H-mediated magnetic transition is accompanied by electronic structure modifications with no structural deviations. To get in-depth information into electronic structure correlations of the observed ferromagnetism, we have investigated their electronic properties in detail. For this purpose, we have employed the site-selective and element-sensitive X-ray-absorption spectroscopy (XAS) in the vicinity of the Cobalt L2,3 edge, the oxygen K edge, and the Zinc L3 edge using synchrotron radiation. The Co L2,3 edge spectra clearly show that Co dopants reside at the Zn sites for both these samples and that they are tetrahedrally coordinated with the ligand O atoms. Very minor changes are observed in the Zn L3 edge spectra. However, the O 1s edge spectra display dominant additional components in the ferromagnetic hydrogenated sample Zn0.95Co0.05O:H, not observed in the as-prepared non-magnetic sample Zn0.95Co0.05O. We conclude that the observed spectral features can be attributed to the presence of O vacancies and the hybridization of Co 3d states with O 2p vacancy states. These two factors together are likely to play important role in inducement of ferromagnetic ordering in this Co-doped ZnO system. However, which of these two weighs more in this mechanism, cannot be pinpointed and more studies are required in this regard.

High-quality ZnO growth, doping, and polarization effect

Science.gov (United States)

Kun, Tang; Shulin, Gu; Jiandong, Ye; Shunming, Zhu; Rong, Zhang; Youdou, Zheng

2016-03-01

The authors have reported their recent progress in the research field of ZnO materials as well as the corresponding global advance. Recent results regarding (1) the development of high-quality epitaxy techniques, (2) the defect physics and the Te/N co-doping mechanism for p-type conduction, and (3) the design, realization, and properties of the ZnMgO/ZnO hetero-structures have been shown and discussed. A complete technology of the growth of high-quality ZnO epi-films and nano-crystals has been developed. The co-doping of N plus an iso-valent element to oxygen has been found to be the most hopeful path to overcome the notorious p-type hurdle. High mobility electrons have been observed in low-dimensional structures utilizing the polarization of ZnMgO and ZnO. Very different properties as well as new physics of the electrons in 2DEG and 3DES have been found as compared to the electrons in the bulk. Project supported by the National Natural Science Foundation of China (Nos. 61025020, 61274058, 61322403, 61504057, 61574075), the Natural Science Foundation of Jiangsu Province (Nos. BK2011437, BK20130013, BK20150585), the Priority Academic Program Development of Jiangsu Higher Education Institutions, and the Fundamental Research Funds for the Central Universities.

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.

Synthesis and characterization of Mn-doped ZnO column arrays

International Nuclear Information System (INIS)

Yang Mei; Guo Zhixing; Qiu Kehui; Long Jianping; Yin Guangfu; Guan Denggao; Liu Sutian; Zhou Shijie

2010-01-01

Mn-doped ZnO column arrays were successfully synthesized by conventional sol-gel process. Effect of Mn/Zn atomic ratio and reaction time were investigated, and the morphology, tropism and optical properties of Mn-doped ZnO column arrays were characterized by SEM, XRD and photoluminescence (PL) spectroscopy. The result shows that a Mn/Zn atomic ratio of 0.1 and growth time of 12 h are the optimal condition for the preparation of densely distributed ZnO column arrays. XRD analysis shows that Mn-doped ZnO column arrays are highly c-axis oriented. As for Mn-doped ZnO column arrays, obvious increase of photoluminescence intensity is observed at the wavelength of ∼395 nm and ∼413 nm, compared to pure ZnO column arrays.

Synthesis Structural and Optical Properties Of (Co, Al) co-doped ZnO Nano Particles

Science.gov (United States)

Swapna, P.; Venkatramana Reddy, S.

2018-02-01

We prepared (Co, Al) co-doped ZnO nanostructures using the method chemical co-precipitation successfully, at room temperature using PEG (Poly ethylene glycol) as stabilizing agent. Samples are prepared with different concentrations by keeping aluminium at 5 mol percent constant and varying the concentration of cobalt from 1 to 5 mol percent. After the preparation all the samples are carefully subjected to characterizations such as XRD, SEM with EDS, TEM, PL and UV-VIS-NIR. XRD pattern shows that all the samples possess hexagonal wurtzite crystal structure having no secondary phases pertaining to Al or cobalt, which shows successful dissolution of the dopents. TEM results shows the accurate size of particles and is confirmed the XRD data. SEM images of all the samples shows that particles are in nearly spherical shape, EDS spectrum reveals that incorporation of cobalt and aluminum in host lattice. PL spectrum shows that all the samples containing two prominent peaks centered at 420 nm and 446 nm. UV-VIS-NIR spectra has shown three absorptions peaks in the range of wavelength 550 nm to 700 nm, which are ascribed as typical d-d transitions of cobalt ions.

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

Influence of Mn and Co on structural and morphological characteristics of ZnO synthesized by combustion reaction

International Nuclear Information System (INIS)

Torquato, R.A.; Costa, C.F.M.; Kiminami, R.H.A.

2010-01-01

This study aims to evaluate the effect of doping of 0.2 mol of Mn and Co on structural and morphological characteristics of ZnO synthesized by combustion reaction. During the synthesis was the measurement of temperature and time of the combustion flame. The samples were characterized by XRD, SEM, particle size distribution and nitrogen adsorption (BET). The maximum temperature the reactions were 428 deg C and 436 deg C, reaction time, and 115 and 0 seconds for the samples doped with Mn and Co, respectively. The XRD data showed that for both impurities were formed only ZnO phase. For Co were formed secondary phase CoO. The crystallite size and surface area were 18 nm and 22 nm, and 52 and 38 m2/g for ZnO doped with Mn and Co, respectively. (author)

Defect induced activation of Raman silent modes in rf co-sputtered Mn doped ZnO thin films

Energy Technology Data Exchange (ETDEWEB)

Yadav, Harish Kumar [Department of Physics and Astrophysics, University of Delhi, Delhi-110007 (India); Sreenivas, K [Department of Physics and Astrophysics, University of Delhi, Delhi-110007 (India); Katiyar, R S [Department of Physics, University of Puerto Rico, San Juan, PR 00931-3343 (Puerto Rico); Gupta, Vinay [Department of Physics and Astrophysics, University of Delhi, Delhi-110007 (India)

2007-10-07

We study the influence of Mn doping on the vibrational properties of rf sputtered ZnO thin films. Raman spectra of the Mn doped ZnO samples reveal two additional vibrational modes, in addition to the host phonon modes, at 252 and 524 cm{sup -1}. The intensity of the additional modes increases continuously with Mn concentration in ZnO and can be used as an indication of Mn incorporation in ZnO. The modes are assigned to the activation of ZnO silent modes due to relaxation of Raman selection rules produced by the breakdown of the translational symmetry of the crystal lattice with the incorporation of Mn at the Zn site. Furthermore, the A{sub 1} (LO) mode is observed with very high intensity in the Raman spectra of undoped ZnO thin film and is attributed to the built-in electric field at the grain boundaries.

Defect induced activation of Raman silent modes in rf co-sputtered Mn doped ZnO thin films

International Nuclear Information System (INIS)

Yadav, Harish Kumar; Sreenivas, K; Katiyar, R S; Gupta, Vinay

2007-01-01

We study the influence of Mn doping on the vibrational properties of rf sputtered ZnO thin films. Raman spectra of the Mn doped ZnO samples reveal two additional vibrational modes, in addition to the host phonon modes, at 252 and 524 cm -1 . The intensity of the additional modes increases continuously with Mn concentration in ZnO and can be used as an indication of Mn incorporation in ZnO. The modes are assigned to the activation of ZnO silent modes due to relaxation of Raman selection rules produced by the breakdown of the translational symmetry of the crystal lattice with the incorporation of Mn at the Zn site. Furthermore, the A 1 (LO) mode is observed with very high intensity in the Raman spectra of undoped ZnO thin film and is attributed to the built-in electric field at the grain boundaries

Structural, optical and magnetic properties of Co doped ZnO DMS nanoparticles by microwave irradiation method

Science.gov (United States)

Guruvammal, D.; Selvaraj, S.; Meenakshi Sundar, S.

2018-04-01

Microwave irradiation method is employed to synthesis of Zn1-xCoxO (x = 0.001-0.004) nanoparticles and investigate their structural, optical and magnetic properties using various characterization techniques. Structural studies reveal single phase hexagonal structure with average crystallite size 18-28 nm. FTIR study identifies the functional group present in the samples. The incorporation of Co2+ ions into the ZnO lattice is confirmed through XRD and UV-Vis studies. PL spectra exhibit a strong emission peak in UV region and a defect related visible emission peak in orange red region. These peaks are attributed to near band edge emission and the presence of oxygen related defects in the samples respectively. The blue shift observed in the UV emission peak shows an increase in the carrier concentration caused by the interstitial incorporation of ions into the ZnO lattice. The oxygen related defect is also confirmed through a peak obtained around g factor 1.9933 in ESR studies. Further, the number of spin contributing the ESR signal demonstrates the dependence of the strength of ferromagnetism on the concentration of oxygen ion vacancies. The VSM, ESR and PL measurements confirm the origin of RTFM of Co doped ZnO nanoparticles from the exchange interaction between the localized spin moments resulting from oxygen vacancies. The reason for the obtained super paramagnetic nature for x = 0.002 and x = 0.003 may be either due to some of nanoparticles or due to the weakly coupled Co ions in the Zn2+ site in the ZnO lattice. Further, the ferromagnetic behavior arises again for x = 0.004 due to the incorporation of Co2+ ions in the interstitial positions.

Enhancement in visible light-responsive photocatalytic activity by embedding Cu-doped ZnO nanoparticles on multi-walled carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Ahmad, M., E-mail: mzkhm73@gmail.com [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan); State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Ahmed, E., E-mail: profejaz@gmail.com [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan); Hong, Z.L.; Jiao, X.L. [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Abbas, T. [Institute of Industrial Control System, Rawalpindi (Pakistan); Khalid, N.R. [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan); State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)

2013-11-15

Copper doped ZnO nanoparticles embedded on multi-walled carbon nanotubes (CNTs) were successfully synthesized using a facile, nontoxic sol method. The resulting visible light-responsive Cu-doped ZnO/CNTs composites were characterized using powder X-ray diffraction (XRD), high resolution transmission electron microscope (HR-TEM), transmission electron microscope (TEM), scanning electron microscope (SEM) with energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS) and Brunauer Emmett Teller (BET) surface area analyzer. Optical properties of Cu-doped ZnO/CNTs nanocomposites, studied using UV–vis diffuse reflectance spectroscopy and photoluminescence spectroscopy (PL), which exhibited extended light absorption in visible light region and possessed better charge separation capability, respectively as compared to Cu-doped ZnO, pure ZnO and ZnO/CNTs composite. The photocatalytic activity was tested by degradation of methyl orange (MO) dye under visible light irradiation. The results demonstrated that Cu-doped ZnO/CNTs nanocomposites effectively bleached out MO, showing an impressive photocatalytic enhancement over ZnO, commercial ZnO, Cu-doped ZnO nanoparticles and ZnO/CNTs nanocomposites. Chemical oxygen demand (COD) of textile wastewater was also measured before and after the photocatalysis experiment under sunlight to evaluate the mineralization of wastewater. The significant decrease in COD of the treated effluent revealed a complete destruction of the organic molecules along with color removal. This dramatically enhanced photoactivity of nanocomposite photocatalysts was attributed to greater adsorptivity of dyes, extended light absorption and increased charge separation efficiency due to excellent electrical properties of carbon nanotubes and the large surface area.

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.

Photoluminescence quenching and enhanced spin relaxation in Fe doped ZnO nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Ovhal, Manoj M.; Santhosh Kumar, A. [Department of Materials Engineering, Defence Institute of Advanced Technology, Girinagar, Pune 411025 (India); Khullar, Prerna [School of Materials Science and Technology, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India); Kumar, Manjeet [Department of Materials Engineering, Defence Institute of Advanced Technology, Girinagar, Pune 411025 (India); Abhyankar, A.C., E-mail: ashutoshabhyankar@gmail.com [Department of Materials Engineering, Defence Institute of Advanced Technology, Girinagar, Pune 411025 (India)

2017-07-01

Cost-effective ultrasonically assisted precipitation method is utilized to synthesize Zinc oxide (ZnO) nanoparticles (NPs) at room temperature and the effect of Iron (Fe) doping on structural, optical and spin relaxation properties also presented. As-synthesized pure and Fe doped ZnO NPs possess a perfect hexagonal growth habit of wurtzite zinc oxide, along the (101) direction of preference. With Fe doping, ‘c/a’ ratio and compressive lattice strain in ZnO NPs are found to reduce and increase, respectively. Raman studies demonstrate that the E{sub 1} longitudinal optical (LO) vibrational mode is very weak in pure which remarkably enhanced with Fe doping into ZnO NPs. The direct band gap energy (E{sub g}) of the ZnO NPs has been increased from 3.02 eV to 3.11 eV with Fe doping. A slight red-shift observed with strong green emission band, in photoluminescence spectra, is strongly quenched in 6 wt.% Fe doped ZnO NPs. The field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) reveals spherical shape of ZnO NPs with 60–70 nm, which reduces substantially on Fe doping. The energy dispersive X-ray spectrum and elemental mapping confirms the homogeneous distribution of Fe in ZnO NPs. Moreover, the specific relaxation rate (R{sub 2sp} = 1/T{sub 2}) has been measured using Carr-Purcell-Meiboom-Gill (CPMG) method and found to be maximum in 6 wt.% Fe doped ZnO NPs. Further, the correlation of structural, optical and dynamic properties is proposed. - Highlights: • Pure ZnO and Fe doped ZnO NPs were successfully prepared by cost effective ultrasonically assisted precipitation method. • The optical band gap of ZnO has been enhanced form 3.02–3.11 eV with Fe doping. • PL quenching behaviour has been observed with Fe{sup 3+} ions substitution in ZnO lattice. • Specific relaxation rate (R{sub 2sp} = 1/T{sub 2}) has been varied with Fe doping and found to be maximum in 6 wt.% Fe doped ZnO NPs.

Formation of polar surfaces in microstructured ZnO by doping with Cu and applications in photocatalysis using visible light

International Nuclear Information System (INIS)

Pawar, Rajendra C.; Choi, Da-Hyun; Lee, Jai-Sung; Lee, Caroline S.

2015-01-01

We report the synthesis of copper-doped zinc oxide microstructures with a large amount of polar surfaces using a single-step facile chemical method by collecting powders of zinc oxide (ZnO) microstructures. It was found that rod-like morphology of ZnO transformed into disk and sphere-like structure with nanosheets. Hollow disk-like structures were formed due to the surface etching properties of Cl − ions in the copper chloride precursor. The photocatalytic degradation of methylene blue (MB) and rhodamine B (RhB) dyes was measured under irradiation with visible light using the structures as catalysts. The Cu-doped ZnO exhibited better photodegradation properties than did undoped ZnO. The enhanced performance is attributed to the existence of (001) polar surfaces, oxygen vacancies, and increased optical absorbance at visible wavelengths, which is consistent with the field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), room temperature photoluminescence (PL), and optical absorbance measurements. These favorable photocatalytic properties of the doped microstructures demonstrate their potential for use in wastewater treatment. - Graphical abstract: Graphical abstract shows the electron transfer mechanism under visible light for Cu-doped ZnO microstructures and the photocatalytic degradation of dye. - Highlights: • Cu induced microstructures of ZnO with polar surfaces. • Methylene blue degradation under visible light irradiation. • Room temperature ferromagnetism due to oxygen vacancies in ZnO. • 7% Cu–ZnO has highest photocatalytic activity

Magnetoresistance of magnetically doped ZnO films

Energy Technology Data Exchange (ETDEWEB)

Behan, A J; Mokhtari, A; Blythe, H J; Fox, A M; Gehring, G A [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom); Ziese, M, E-mail: G.A.Gehring@sheffield.ac.u [Division of Superconductivity and Magnetism, University of Leipzig, D-04103, Leipzig (Germany)

2009-08-26

Magnetoresistance measurements have been made at 5 K on doped ZnO thin films grown by pulsed laser deposition. ZnCoO, ZnCoAlO and ZnMnAlO samples have been investigated and compared to similar films containing no transition metal dopants. It is found that the Co-doped samples with a high carrier concentration have a small negative magnetoresistance, irrespective of their magnetic moment. On decreasing the carrier concentration, a positive contribution to the magnetoresistance appears and a further negative contribution. This second, negative contribution, which occurs at very low carrier densities, correlates with the onset of ferromagnetism due to bound magnetic polarons suggesting that the negative magnetoresistance results from the destruction of polarons by a magnetic field. An investigation of the anisotropic magnetoresistance showed that the orientation of the applied magnetic field, relative to the sample, had a large effect. The results for the ZnMnAlO samples showed less consistent trends.

Preparation and characterization of Ce-doped ZnO nanofibers by an electrospinning method

Directory of Open Access Journals (Sweden)

Jong-Pil Kim

2011-02-01

Full Text Available ZnO and Ce-doped ZnO Nanofibers on (111 Pt/SiO2/Si substrates were produced using an electrospinning technique. The as-prepared composite fibres were subjected to high-temperature calcination to produce inorganic fibers. After calcining at a temperature of 500 °C, the average diameter of the ZnO and Ce-doped ZnO nanofibers were determined to be 170 nm and 225 nm, respectively. The average grain size of the ZnO and Ce-doped ZnO nanofibers were about 50 nm and 57 nm, respectively. The microstructure, chemical bonding state and photoluminescence of the produced ZnO and Ce-doped ZnO nanofibers were investigated. The Ce-doped ZnO nanofiber can be assigned to the presence of Ce ions on substitutional sites of Zn ions and the Ce3+ state from X-ray photoelectron spectra. Compared with PL spectra of ZnO nanofibers, the peak position of the UV emission of the Ce-doped ZnO nanofibers is sharply suppressed while the green emission band is highly enhanced.

Synthesis, characterization and electrochemical behavior of Sb-doped ZnO microsphere film

Energy Technology Data Exchange (ETDEWEB)

Li, Qian [Department of Materials Science and Engineering, State Key Laboratory of Silicon Materials, Cyrus Tang Center for Sensor Materials and Applications, Zhejiang University, Hangzhou, 310027 (China); Cheng, Kui, E-mail: chengkui@zju.edu.cn [Department of Materials Science and Engineering, State Key Laboratory of Silicon Materials, Cyrus Tang Center for Sensor Materials and Applications, Zhejiang University, Hangzhou, 310027 (China); Weng, Wenjian, E-mail: wengwj@zju.edu.cn [Department of Materials Science and Engineering, State Key Laboratory of Silicon Materials, Cyrus Tang Center for Sensor Materials and Applications, Zhejiang University, Hangzhou, 310027 (China); The Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai, 200050 (China); Du, Piyi; Han, Gaorong [Department of Materials Science and Engineering, State Key Laboratory of Silicon Materials, Cyrus Tang Center for Sensor Materials and Applications, Zhejiang University, Hangzhou, 310027 (China)

2013-10-01

Sb-doped ZnO microsphere film was fabricated by a carboxylate ion assisted hydrothermal route coupled with a post-calcination process. The structure, chemical composition and optical band gap of the Sb-doped ZnO microsphere film were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, inductively couple plasma optical emission spectroscopy and UV–visible spectrophotometry, and compared with the un-doped ZnO microsphere film. The results suggest that the formation of zinc–antimony tartrate complex species during hydrothermal growth is the key to realize Sb-doped ZnO microstructures, and the present hydrothermal method with post-calcination is an effective way to dope Sb into ZnO. Furthermore, the Sb-doped ZnO microsphere film based electrochemical biosensor exhibits a good sensing performance for the detection of hydrogen peroxide, with a sensitivity of 271 μA mM{sup −1} cm{sup −2} which is more than three times higher than that of the un-doped ZnO biosensor. - Highlights: • Sb-doped ZnO microsphere (SZM) films were grown by hydrothermal deposition. • Carboxylate ions were used to form complex during hydrothermal growth. • The formation of Zn–Sb tartrate complex is the key to realize SZM. • The biosensors based on SZM film are feasible and sensitive to detect H{sub 2}O{sub 2}. • The Sb doping could improve the electrochemical property of ZnO.

Atomic layer deposition of Al-doped ZnO thin films

Energy Technology Data Exchange (ETDEWEB)

Tynell, Tommi; Yamauchi, Hisao; Karppinen, Maarit; Okazaki, Ryuji; Terasaki, Ichiro [Department of Chemistry, Aalto University, FI-00076 Aalto (Finland); Department of Physics, Nagoya University, Nagoya 464-8602 (Japan)

2013-01-15

Atomic layer deposition has been used to fabricate thin films of aluminum-doped ZnO by depositing interspersed layers of ZnO and Al{sub 2}O{sub 3} on borosilicate glass substrates. The growth characteristics of the films have been investigated through x-ray diffraction, x-ray reflection, and x-ray fluorescence measurements, and the efficacy of the Al doping has been evaluated through optical reflectivity and Seebeck coefficient measurements. The Al doping is found to affect the carrier density of ZnO up to a nominal Al dopant content of 5 at. %. At nominal Al doping levels of 10 at. % and higher, the structure of the films is found to be strongly affected by the Al{sub 2}O{sub 3} phase and no further carrier doping of ZnO is observed.

Explanation of ferromagnetism origin in C-doped ZnO by first principle calculations

International Nuclear Information System (INIS)

El Amiri, A.; Lassri, H.; Hlil, E.K.; Abid, M.

2015-01-01

By ab-initio calculations, we systematically study possible source of ferromagnetism C-doped ZnO compound. The electronic structure and magnetic properties of C-doped ZnO with / without ZnO host and C defects were investigated using the Korringa–Kohn–Rostoker (KKR) method combined with coherent potential approximation (CPA). We show that Zn vacancy and presence of C defects (substitutional, interstitial or combination of both) induce the ferromagnetism in C-doped ZnO. From density of state (DOS) analysis, we show that p–p interaction between C atoms and/or C and O atoms is the mechanism of ferromagnetic coupling in C-doped ZnO. - Highlights: • We study the effect of ZnO host and C defects on ferromagnetism in C-doped ZnO. • Details of KKR method calculations performed to investigate both magnetic and electronic structures. • Magnetic moments, total and partial DOS for C-doped ZnO are well calculated and discussed. • Based on DOS calculations we interpret a origin of ferromagnetism in C-doped ZnO. • Mechanism of ferromagnetic coupling is well proposed

Explanation of ferromagnetism origin in C-doped ZnO by first principle calculations

Energy Technology Data Exchange (ETDEWEB)

El Amiri, A., E-mail: aelamiri@casablanca.ma [Laboratoire de Physique Fondamentale et Appliquée (LPFA), Faculté des Sciences Ain Chock, Université Hassan II, B.P. 5366 Mâarif, Casablanca, Maroc (Morocco); Lassri, H. [Laboratoire de Physique des Matériaux, Micro-électronique, Automatique et Thermique (LPMMAT). Faculté des Sciences Ain Chock, Université Hassan II, B.P. 5366 Mâarif, Casablanca, Maroc (Morocco); Hlil, E.K. [Institut Néel, CNRS et Université Joseph Fourier, BP 166, 38042 Grenoble (France); Abid, M. [Laboratoire de Physique Fondamentale et Appliquée (LPFA), Faculté des Sciences Ain Chock, Université Hassan II, B.P. 5366 Mâarif, Casablanca, Maroc (Morocco)

2015-01-15

By ab-initio calculations, we systematically study possible source of ferromagnetism C-doped ZnO compound. The electronic structure and magnetic properties of C-doped ZnO with / without ZnO host and C defects were investigated using the Korringa–Kohn–Rostoker (KKR) method combined with coherent potential approximation (CPA). We show that Zn vacancy and presence of C defects (substitutional, interstitial or combination of both) induce the ferromagnetism in C-doped ZnO. From density of state (DOS) analysis, we show that p–p interaction between C atoms and/or C and O atoms is the mechanism of ferromagnetic coupling in C-doped ZnO. - Highlights: • We study the effect of ZnO host and C defects on ferromagnetism in C-doped ZnO. • Details of KKR method calculations performed to investigate both magnetic and electronic structures. • Magnetic moments, total and partial DOS for C-doped ZnO are well calculated and discussed. • Based on DOS calculations we interpret a origin of ferromagnetism in C-doped ZnO. • Mechanism of ferromagnetic coupling is well proposed.

Synthesis and characterization of ZnO and Ni doped ZnO nanorods by thermal decomposition method for spintronics application

International Nuclear Information System (INIS)

Saravanan, R.; Santhi, Kalavathy; Sivakumar, N.; Narayanan, V.; Stephen, A.

2012-01-01

Zinc oxide nanorods and diluted magnetic semiconducting Ni doped ZnO nanorods were prepared by thermal decomposition method. This method is simple and cost effective. The decomposition temperature of acetate and formation of oxide were determined by TGA before the actual synthesis process. The X-ray diffraction result indicates the single phase hexagonal structure of zinc oxide. The transmission electron microscopy and scanning electron microscopy images show rod like structure of ZnO and Ni doped ZnO samples with the diameter ∼ 35 nm and the length in few micrometers. The surface analysis was performed using X-ray photoelectron spectroscopic studies. The Ni doped ZnO exhibits room temperature ferromagnetism. This diluted magnetic semiconducting Ni doped ZnO nanorods finds its application in spintronics. - Highlights: ► The method used is very simple and cost effective compared to all other methods for the preparation DMS materials. ► ZnO and Ni doped ZnO nanorods ► Ferromagnetism at room temperature

Investigation of structural, surface morphological, optical properties and first-principles study on electronic and magnetic properties of (Ce, Fe)-co doped ZnO

International Nuclear Information System (INIS)

Arul Mary, J.; Judith Vijaya, J.; Bououdina, M.; John Kennedy, L.; Daie, J.H.; Song, Y.

2015-01-01

We report on the synthesis of ((Zn 1−2x Ce x Fe x ) O (x=0.00, 0.01, 0.02, 0.03, 0.04 and 0.05)) nanoparticles via microwave combustion by using urea as a fuel. To understand how the dopant influenced the structural, magnetic and optical properties of nanoparticles, it was characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectra and vibrating sample magnetometer (VSM). The stability and magnetic properties of Ce and Fe co-doped ZnO were probed by first principle calculations. From the analysis of X-ray diffraction, the samples are identified with the wurtzite crystal structure. The change in lattice parameters, micro-strain, and a small shift in XRD peaks confirms the substitution of co dopants into the ZnO lattice. Morphological investigation of the products revealed the existence of irregular shapes, such as spherical, spherodial and hexagonal. DRS measurements showed a decrease in the energy gap with increasing dopants contents, probably due to an increase in the lattice parameters. PL spectra consist of visible emission, due to the electronic defects, which are related to deep level emissions, such as oxide antisite (O Zn ), interstitial zinc (Zn i ), interstitial oxygen (O i ) and zinc vacancy (V Zn ). Magnetic measurements showed a ferromagnetic behavior for all the doped samples at room temperature. The first principle calculation results showed that the Ce governs the stability, while the Fe adjusts the magnetic characteristics in the Ce and Fe co-doped ZnO

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

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.

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.

Synthesis of Cu and Ce co-doped ZnO nanoparticles: crystallographic, optical, molecular, morphological and magnetic studies

Directory of Open Access Journals (Sweden)

Rawat Mohit

2017-07-01

Full Text Available In the present research work, crystallographic, optical, molecular, morphological and magnetic properties of Zn1-xCuxO (ZnCu and Zn1-x-yCeyCuxO (ZnCeCu nanoparticles have been investigated. Polyvinyl alcohol (PVA coated ZnCu and ZnCeCu nanoparticles have been synthesized by chemical sol-gel method and thoroughly studied using various characterization techniques. X-ray diffraction pattern indicates the wurtzite structure of the synthesized ZnCu and ZnCeCu particles. Transmission electron microscopy analysis shows that the synthesized ZnCu and ZnCeCu particles are of spherical shape, having average sizes of 27 nm and 23 nm, respectively. The incorporation of Cu and Ce in the ZnO lattice has been confirmed through Fourier transform infrared spectroscopy. Room temperature photoluminescence spectra of the ZnO doped with Cu and co-doped Ce display two emission bands, predominant ultra-violet near-band edge emission at 409.9 nm (3 eV and a weak green-yellow emission at 432.65 nm (2.27 eV. Room temperature magnetic study confirms the diamagnetic behavior of ZnCu and ferromagnetic behavior of ZnCeCu.

Structural and Magnetic Properties of Mn doped ZnO Thin Film Deposited by Pulsed Laser Deposition

KAUST Repository

Baras, Abdulaziz

2011-07-01

Diluted magnetic oxide (DMO) research is a growing field of interdisciplinary study like spintronic devices and medical imaging. A definite agreement among researchers concerning the origin of ferromagnetism in DMO has yet to be reached. This thesis presents a study on the structural and magnetic properties of DMO thin films. It attempts to contribute to the understanding of ferromagnetism (FM) origin in DMO. Pure ZnO and Mn doped ZnO thin films have been deposited by pulsed laser deposition (PLD) using different deposition conditions. This was conducted in order to correlate the change between structural and magnetic properties. Structural properties of the films were characterized using x-ray diffraction (XRD) and scanning electron microscopy (SEM). The superconducting quantum interference device (SQUID) was used to investigate the magnetic properties of these films. The structural characterizations showed that the quality of pure ZnO and Mn doped ZnO films increased as oxygen pressure (PO) increased during deposition. All samples were insulators. In Mn doped films, Mn concentration decreased as PO increased. The Mn doped ZnO samples were deposited at 600˚C and oxygen pressure from 50-500mTorr. All Mn doped films displayed room temperature ferromagnetism (RTFM). However, at 5 K a superparamagnetic (SPM) behavior was observed in these samples. This result was accounted for by the supposition that there were secondary phase(s) causing the superparamagnetic behavior. Our findings hope to strengthen existing research on DMO origins and suggest that secondary phases are the core components that suppress the ferromagnetism. Although RTFM and SPM at low temperature has been observed in other systems (e.g., Co doped ZnO), we are the first to report this behavior in Mn doped ZnO. Future research might extend the characterization and exploration of ferromagnetism in this system.

High sensitivity ethanol gas sensor based on Sn - doped ZnO under visible light irradiation at low temperature

Energy Technology Data Exchange (ETDEWEB)

Zhang, Peishuo; Pan, Guofeng; Zhang, Bingqiang; Zhen, Jiali; Sun, Yicai, E-mail: pgf@hebut.edu.cn [Institute of Microelectronic, Hebei University of Technology, Tianjin (China)

2014-07-15

Pure ZnO and 5at%, 7at%, 9at% Sn - doped ZnO materials are prepared by the chemical co - precipitation method. They were annealed by furnace at temperature range of 300 - 700ºC in air for 1h. The ZnO materials are characterized by X - ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that the Sn - doped ZnO materials appear rough porous structures. The maximum sensitivity can be achieved by doping the amount of 7 at%. It has much better sensing performance towards ethanol vapor under visible light irradiation. The response and recovery time are ~1s and ~5s, respectively. The mechanism for the improvement in the sensing properties can be explained with the surface adsorption theory and the photoactivation theory. (author)

Mass production and photoelectric performances of P and Al Co-doped ZnO nanocrystals under different cooling post-processes

International Nuclear Information System (INIS)

Deng, Ya-Juan; Lu, Yi; Liu, Jin-Ku; Yang, Xiao-Hong

2015-01-01

The phosphorus and aluminum co-doped in zinc oxide (ZnO) called PAZO nano-crystals (NCs) have been mass synthesized by a combustion method, which shows a preferable photocatalytic capability and conductive ability. This article focuses on the properties of PAZO NCs experienced by three cooling-down aftertreatments, which were the normalizing, quenching and annealing process, respectively. The influences of different cooling processes on the photocatalytic and conductive performances are discussed in details. From the research, we found the quenched-PAZO NCs showed the most unappealing photocatalysis and conductivity, because excessive defects as the recombination center of electron–hole pairs were generated in the quenching process. - Graphical abstract: This research focuses on the PAZO NCs experienced by different cooling-down aftertreatments, which were the normalizing, quenching and annealing process, respectively. The quenched-PAZO NCs had the most unappealing photocatalysis and conductivity, because of generating excessive defects as the recombination center of electron–hole pairs in the quenching process. - Highlights: • We presented a method to mass synthesize co-doped P and Al in ZnO nanocrystals. • The PAZO NCs have novel photoelectric performances. • The cooling post-process influence on the photoelectric properties was studied. • The excessive defects decline the photocatalytic and conductive activities

Y-Doped ZnO Nanorods by Hydrothermal Method and Their Acetone Gas Sensitivity

Directory of Open Access Journals (Sweden)

Peng Yu

2013-01-01

Full Text Available Pure and yttrium- (Y- doped (1 at%, 3 at%, and 7 at% ZnO nanorods were synthesized using a hydrothermal process. The crystallography and microstructure of the synthesized samples were characterized by X-ray diffraction (XRD, scanning electron microscopy (SEM, and energy dispersive X-ray spectroscopy (EDX. Comparing with pure ZnO nanorods, Y-doped ZnO exhibited improved acetone sensing properties. The response of 1 at% Y-doped ZnO nanorods to 100 ppm acetone is larger than that of pure ZnO nanorods. The response and recovery times of 1 at% Y-doped ZnO nanorods to 100 ppm acetone are about 30 s and 90 s, respectively. The gas sensor based on Y-doped ZnO nanorods showed good selectivity to acetone in the interfere gases of ammonia, benzene, formaldehyde, toluene, and methanol. The formation mechanism of the ZnO nanorods was briefly analyzed.

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.

Investigation of structural, surface morphological, optical properties and first-principles study on electronic and magnetic properties of (Ce, Fe)-co doped ZnO

Energy Technology Data Exchange (ETDEWEB)

Arul Mary, J. [Catalysis and Nanomaterials Research Laboratory, Department of Chemistry Loyola College, Chennai 600 034 (India); Judith Vijaya, J., E-mail: jjvijayaloyola@yahoo.co.in [Catalysis and Nanomaterials Research Laboratory, Department of Chemistry Loyola College, Chennai 600 034 (India); Bououdina, M. [Departments of Physics, College of Science, University of Bahrain, PO Box 32038 Kingdom of Bahrain (Bahrain); John Kennedy, L. [Materials Division, School of Advanced Sciences, Vellore Institute of Technology (VIT) University, Chennai Campus, Chennai 600 127 (India); Daie, J.H.; Song, Y. [School of Materials Science and Engineering, Harbin Institute of Technology at Weihai, 2 West Wenhua Road, Weiahi 264209 (China)

2015-01-01

We report on the synthesis of ((Zn{sub 1−2x}Ce{sub x}Fe{sub x}) O (x=0.00, 0.01, 0.02, 0.03, 0.04 and 0.05)) nanoparticles via microwave combustion by using urea as a fuel. To understand how the dopant influenced the structural, magnetic and optical properties of nanoparticles, it was characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectra and vibrating sample magnetometer (VSM). The stability and magnetic properties of Ce and Fe co-doped ZnO were probed by first principle calculations. From the analysis of X-ray diffraction, the samples are identified with the wurtzite crystal structure. The change in lattice parameters, micro-strain, and a small shift in XRD peaks confirms the substitution of co dopants into the ZnO lattice. Morphological investigation of the products revealed the existence of irregular shapes, such as spherical, spherodial and hexagonal. DRS measurements showed a decrease in the energy gap with increasing dopants contents, probably due to an increase in the lattice parameters. PL spectra consist of visible emission, due to the electronic defects, which are related to deep level emissions, such as oxide antisite (O{sub Zn}), interstitial zinc (Zn{sub i}), interstitial oxygen (O{sub i}) and zinc vacancy (V{sub Zn}). Magnetic measurements showed a ferromagnetic behavior for all the doped samples at room temperature. The first principle calculation results showed that the Ce governs the stability, while the Fe adjusts the magnetic characteristics in the Ce and Fe co-doped ZnO.

Superior sinterability of nano-crystalline gadolinium doped ceria powders synthesized by co-precipitation method

International Nuclear Information System (INIS)

Hari Prasad, D.; Kim, H.-R.; Park, J.-S.; Son, J.-W.; Kim, B.-K.; Lee, H.-W.; Lee, J.-H.

2010-01-01

Reduced sintering temperature of doped ceria can greatly simplify the fabrication process of solid oxide fuel cells (SOFCs) by utilizing the co-firing of all cell components with a single step. In the present study, nano-crystalline gadolinium doped ceria (GDC) powders of high sinterability at lower sintering temperature has been synthesized by co-precipitation at room temperature. The successful synthesis of nano-crystalline GDC was confirmed by XRD, TEM and Raman spectroscopy analysis. Dilatometry studies showed that GDC prepared by this method can be fully densified (97% relative density) at a sintering temperature of 950 o C which is fairly lower than ever before. It has also been found that the sintered samples have a higher ionic conductivity of 1.64 x 10 -2 S cm -1 at 600 o C which is suitable for the intermediate temperature SOFC application.

Preparation of Aligned ZnO Nanorod Arrays on Sn-Doped ZnO Thin Films by Sonicated Sol-Gel Immersion Fabricated for Dye-Sensitized Solar Cell

Directory of Open Access Journals (Sweden)

I. Saurdi

2014-01-01

Full Text Available Aligned ZnO Nanorod arrays are deposited on the Sn-doped ZnO thin film via sonicated sol-gel immersion method. The structural, optical, and electrical properties of the Sn-doped ZnO thin films were investigated. Results show that the Sn-doped ZnO thin films with small grain size (~20 nm, high average transmittance (96% in visible region, and good resistivity 7.7 × 102 Ω·cm are obtained for 2 at.% Sn doping concentration. The aligned ZnO nanorod arrays with large surface area were also obtained for 2 at.% Sn-doped ZnO thin film. They were grown on sol-gel derived Sn-doped ZnO thin film, which acts as a seed layer, via sonicated sol-gel immersion method. The grown aligned ZnO nanorod arrays show high transmittance at visible region. The fabricated dye-sensitised solar cell based on the 2.0 at.% Sn-doped ZnO thin film with aligned ZnO nanorod arrays exhibits improved current density, open-circuit voltage, fill factor, and conversion efficiency compared with the undoped ZnO and 1 at.% Sn-doped ZnO thin films.

Mn-doped ZnO nanocrystals synthesized by sonochemical method: Structural, photoluminescence, and magnetic properties

Energy Technology Data Exchange (ETDEWEB)

Othman, A.A., E-mail: aaelho@yahoo.com [Assiut University, Faculty of Science, Department of Physics, Assiut 71516 (Egypt); Osman, M.A. [Assiut University, Faculty of Science, Department of Physics, Assiut 71516 (Egypt); Ibrahim, E.M.M. [Sohag University, Faculty of Science, Department of Physics, Sohag 82524 (Egypt); Ali, Manar A.; Abd-Elrahim, A.G. [Assiut University, Faculty of Science, Department of Physics, Assiut 71516 (Egypt)

2017-05-15

Highlights: • Mn-doped ZnO nanostructures were synthesized by the sonochemical method. • Structural, morphological, optical, photoluminescence and magnetic properties were investigated. • Mn-doped ZnO nanostructures reveal a blue shift of the optical band gap. • Photoluminescence spectra of Mn-doped ZnO nanostructures show quenching in the emission intensity. • Mn-doped ZnO nanostructures exhibit ferromagnetic ordering at room temperature. - Abstract: This work reports the synthesis of Mn-doped ZnO nanostructures using ice-bath assisted sonochemical technique. The impact of Mn-doping on structural, morphological, optical, and magnetic properties of ZnO nanostructures is studied. The morphological study shows that the lower doped samples possess mixtures of nanosheets and nanorods while the increase in Mn content leads to improvement of an anisotropic growth in a preferable orientation to form well-defined edge rods at Mn content of 0.04. UV–vis absorption spectra show that the exciton peak in the UV region is blue shifted due to Mn incorporation into the ZnO lattice. Doping ZnO with Mn ions leads to a reduction in the PL intensity due to a creation of more non-radiative recombination centers. The magnetic measurements show that the Mn-doped ZnO nanostructures exhibit ferromagnetic ordering at room temperature, as well as variation of the Mn content can significantly affect the ferromagnetic behavior of the samples.

Spectral features and antibacterial properties of Cu-doped ZnO nanoparticles prepared by sol-gel method

International Nuclear Information System (INIS)

Samavati, Alireza; Nur, Hadi; Othaman, Z; Ismail, A F; Mustafa, M K

2016-01-01

Zn 1−x Cu x O (x = 0.00, 0.01, 0.03, and 0.05) nanoparticles are synthesized via the sol-gel technique using gelatin and nitrate precursors. The impact of copper concentration on the structural, optical, and antibacterial properties of these nanoparticles is demonstrated. Powder x-ray diffraction investigations have illustrated the organized Cu doping into ZnO nanoparticles up to Cu concentration of 5% ( x = 0.05). However, the peak corresponding to CuO for x = 0.01 is not distinguishable. The images of field emission scanning electron microscopy demonstrate the existence of a nearly spherical shape with a size in the range of 30–52 nm. Doping Cu creates the Cu–O–Zn on the surface and results in a decrease in the crystallite size. Photoluminescence and absorption spectra display that doping Cu causes an increment in the energy band gap. The antibacterial activities of the nanoparticles are examined against Escherichia coli (Gram negative bacteria) cultures using optical density at 600 nm and a comparison of the size of inhibition zone diameter. It is found that both pure and doped ZnO nanoparticles indicate appropriate antibacterial activity which rises with Cu doping. (paper)

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.

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

DEFF Research Database (Denmark)

Han, Li; Van Nong, Ngo; Zhang, Wei

2014-01-01

The nanoparticles of Al-doped ZnO were successfully grown into rod-like and platelet-like morphologies by soft chemical routes. These powders were consolidated using spark plasma sintering (SPS) technique. The samples consolidated from rods and platelets exhibited characteristic structures...... consolidated from nanoparticles exhibited fine grains and highly distributed nanoprecipitates, resulting in a ZT value of 0.3 at 1223 K due to the lower thermal conductivity resulting from nanostructuring. Using the simple parabolic band model and Debye–Callaway thermal transport model, the anisotropic...

Role of nickel doping on structural, optical, magnetic properties and antibacterial activity of ZnO nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Vijayaprasath, G.; Murugan, R. [School of Physics, Alagappa University, Karaikudi 630 004, Tamil Nadu (India); Palanisamy, S.; Prabhu, N.M. [Department of Animal Health and Management, Alagappa University, Karaikudi 630 004, Tamil Nadu (India); Mahalingam, T. [Department of Electrical and Computer Engineering, Ajou University, Suwon 443-749 (Korea, Republic of); Hayakawa, Y. [Research Institute of Electronics, Shizuoka University, Hamamatsu 432-8011 (Japan); Ravi, G., E-mail: gravicrc@gmail.com [School of Physics, Alagappa University, Karaikudi 630 004, Tamil Nadu (India)

2016-04-15

Highlights: • The XRD analyses revealed that the synthesizes nickel doped ZnO (Zn{sub 1−x}Ni{sub x}O, x = 0.0, 0.03, 0.06 and 0.09) nanostructures have hexagonal wurtzite structure. • The photoluminescence measurements revealed that the broad emission was composed of different bands due to zinc and oxygen vacancies. • X-ray photoelectron spectroscopy (XPS) confirmed the Ni incorporation in ZnO lattice as Ni{sup 2+} ions. • Room temperature ferromagnetism was observed due to the oxygen vacancies and zinc interstitials are the main reasons for ferromagnetism in Ni doped ZnO NPs. - Abstract: Zn{sub 1−x}Ni{sub x}O nanoparticles were synthesized by co-precipitation method. The crystallite sizes of the synthesized samples found to decrease from 38 to 26 nm with increase in nickel concentration. FTIR spectra confirmed the presence of Zn−O stretching bands at 577, 573, 569 and 565 cm{sup −1} in the respective ZnO NPs. Optical absorption spectra revealed the red shifted and estimated band gap is found to decrease with increase of Ni doping concentration. The PL spectra of all the samples exhibited a broad emission at 390 nm in the visible range. The carriers (donors) bounded on the Ni sites were observed from the micro Raman spectroscopic studies. Pure and Ni doped ZnO NPs showed significant changes in the M–H loop, especially the diamagnetic behavior changed into ferromagnetic nature for Ni doped samples. The antiferromagnetic super-exchange interactions between Ni{sup 2+} ions is increased in higher Ni doped ZnO NPs and also their antibacterial activity has been studied.

Electronic structure, magnetic and structural properties of Ni doped ZnO nanoparticles

International Nuclear Information System (INIS)

Kumar, Shalendra; Vats, Prashant; Gautam, S.; Gupta, V.P.; Verma, K.D.; Chae, K.H.; Hashim, Mohd; Choi, H.K.

2014-01-01

Highlights: • XRD, and HR-TEM results show the single phase nature of Ni doped ZnO nanoparticles. • dc magnetization results indicate the RT-FM in Ni doped ZnO nanoparticles. • Ni L 3,2 edge NEXAFS spectra infer that Ni ions are in +2 valence state. • O K edge NEXAFS spectra show that O vacancy increases with Ni doping in ZnO. - Abstract: We report structural, magnetic and electronic structural properties of Ni doped ZnO nanoparticles prepared by auto-combustion method. The prepared nanoparticles were characterized by using X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), near edge X-ray absorption fine structure (NEXAFS) spectroscopy, and dc magnetization measurements. The XRD and HR-TEM results indicate that Ni doped ZnO nanoparticles have single phase nature with wurtzite lattice and exclude the presence of secondary phase. NEXAFS measurements performed at Ni L 3,2 -edges indicates that Ni ions are in +2 valence state and exclude the presence of Ni metal clusters. O K-edge NEXAFS spectra indicate an increase in oxygen vacancies with Ni-doping, while Zn L 3,2 -edge show the absence of Zn-vacancies. The magnetization measurements performed at room temperature shows that pure and Ni doped ZnO exhibits ferromagnetic behavior

Effect of (Mn,Cr) co-doping on structural, electronic and magnetic properties of zinc oxide by first-principles studies

Science.gov (United States)

Aimouch, D. E.; Meskine, S.; Boukortt, A.; Zaoui, A.

2018-04-01

In this study, structural, electronic and magnetic properties of Mn doped (ZnO:Mn) and (Mn,Cr) co-doped zinc oxide (ZnO:(Mn,Cr)) have been calculated with the FP-LAPW method by using the LSDA and LSDA+U approximations. Going through three configurations of Mn,Cr co-doped ZnO corresponding to three different distances between manganese and chromium, we have analyzed that ZnO:(Mn,Cr) system is more stable in its preferred configuration2. The lattice constant of undoped ZnO that has been calculated in this study is in a good agreement with the experimental and theoretical values. It was found to be increased by doping with Mn or (Mn,Cr) impurities. The band structure calculations showed the metallic character of Mn doped and Mn,Cr co-doped ZnO. As results, by using LSDA+U (U = 6eV), we show the half-metallic character of ZnO:Mn and ZnO:Mn,Cr. We present the calculated exchange couplings d-d of Mn doped ZnO which is in a good agreement with the former FPLO calculation data and the magnetization step measurement of the experimental work. The magnetic coupling between neighboring Mn impurities in ZnO is found to be antiferromagnetic. In the case of (Mn,Cr) co-doped ZnO, the magnetic coupling between Mn and Cr impurities is found to be antiferromagnetic for configuration1 and 3, and ferromagnetic for configuration2. Thus, the ferromagnetic coupling is weak in ZnO:Mn. Chromium co-doping greatly enhance the ferromagnetism, especially when using configuration2. At last, we present the 2D and 3D spin-density distribution of ZnO:Mn and ZnO:(Mn,Cr) where the ferromagnetic state in ZnO:(Mn,Cr) comes from the strong p-d and d-d interactions between 2p-O, 3d-Mn and 3d-Cr electrons. The results of our calculations suggest that the co-doping ZnO(Mn, Cr) can be among DMS behavior for spintronic applications.

First-principles study of doping effect on the phase transition of zinc oxide with transition metal doped

International Nuclear Information System (INIS)

Wu, Liang; Hou, Tingjun; Wang, Yi; Zhao, Yanfei; Guo, Zhenyu; Li, Youyong; Lee, Shuit-Tong

2012-01-01

Highlights: ► We study the doping effect on B4, B1 structures and phase transition of ZnO. ► We calculate the phase transition barrier and phase transition path of doped ZnO. ► The transition metal doping decreases the bulk modulus and phase transition pressure. ► The magnetic properties are influenced by the phase transition process. - Abstract: Zinc oxide (ZnO) is a promising material for its wide application in solid-state devices. With the pressure raised from an ambient condition, ZnO transforms from fourfold wurtzite (B4) to sixfold coordinated rocksalt (B1) structure. Doping is an efficient approach to improve the structures and properties of materials. Here we use density-functional theory (DFT) to study doped ZnO and find that the transition pressure from B4 phase to B1 phase of ZnO always decreases with different types of transition metal (V, Cr, Mn, Fe, Co, or Ni) doped, but the phase transition path is not affected by doping. This is consistent with the available experimental results for Mn-doped ZnO and Co-doped ZnO. Doping in ZnO causes the lattice distortion, which leads to the decrease of the bulk modulus and accelerates the phase transition. Mn-doped ZnO shows the strongest magnetic moment due to its half filled d orbital. For V-doped ZnO and Cr-doped ZnO, the magnetism is enhanced by phase transition from B4 to B1. But for Mn-doped ZnO, Fe-doped ZnO, Co-doped ZnO, and Ni-doped ZnO, B1 phase shows weaker magnetic moment than B4 phase. These results can be explained by the amount of charge transferred from the doped atom to O atom. Our results provide a theoretical basis for the doping approach to change the structures and properties of ZnO.

Tungsten-doped ZnO nanocomposite: Synthesis, characterization, and highly active photocatalyst toward dye photodegradation

Energy Technology Data Exchange (ETDEWEB)

Moafi, Hadi Fallah, E-mail: Fallah.m@guilan.ac.ir [Department of Chemistry, Faculty of Science, University of Guilan, P.O. Box 1914, Rasht (Iran, Islamic Republic of); Zanjanchi, Mohammad Ali; Shojaie, Abdollah Fallah [Department of Chemistry, Faculty of Science, University of Guilan, P.O. Box 1914, Rasht (Iran, Islamic Republic of)

2013-05-15

A series of W-doped ZnO nanocomposite with different W contents were synthesized by sol–gel method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma (ICP) and BET surface area measurement. The XRD results revealed that all the W-doped samples showed a hexagonal wurtzite structure. The results of EDS and XPS revealed that W was doped into ZnO structure. The particle size of doped ZnO is much smaller as compared to that of pure ZnO. The photocatalytic activity of undoped ZnO and W-doped ZnO was evaluated by the photodegradation of methylene blue in aqueous solution. The results show that the photocatalytic activity of the W-doped ZnO is much higher than that of undoped ZnO and the optimum percentage of doped W is 4 mol%. The enhanced photocatalytic activity of the W-ZnO samples may be related to the narrowing of the band gap, increase in the charge separation efficiency, particle size reduction and increase of the surface area. Highlights: ► W-doped ZnO nanocomposites were synthesized by a sol–gel method. ► The XRD results revealed that all the materials consisting of wurtzite structure. ► The sizes of the W-ZnO nanocomposite are 5–10 nm, obtained from TEM image. ► With W doping into ZnO photoinduced charge separation rate has been enhanced. ► Photocatalytic activity of the W-ZnO is much higher than that of undoped ZnO.

Tungsten-doped ZnO nanocomposite: Synthesis, characterization, and highly active photocatalyst toward dye photodegradation

International Nuclear Information System (INIS)

Moafi, Hadi Fallah; Zanjanchi, Mohammad Ali; Shojaie, Abdollah Fallah

2013-01-01

A series of W-doped ZnO nanocomposite with different W contents were synthesized by sol–gel method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma (ICP) and BET surface area measurement. The XRD results revealed that all the W-doped samples showed a hexagonal wurtzite structure. The results of EDS and XPS revealed that W was doped into ZnO structure. The particle size of doped ZnO is much smaller as compared to that of pure ZnO. The photocatalytic activity of undoped ZnO and W-doped ZnO was evaluated by the photodegradation of methylene blue in aqueous solution. The results show that the photocatalytic activity of the W-doped ZnO is much higher than that of undoped ZnO and the optimum percentage of doped W is 4 mol%. The enhanced photocatalytic activity of the W-ZnO samples may be related to the narrowing of the band gap, increase in the charge separation efficiency, particle size reduction and increase of the surface area. Highlights: ► W-doped ZnO nanocomposites were synthesized by a sol–gel method. ► The XRD results revealed that all the materials consisting of wurtzite structure. ► The sizes of the W-ZnO nanocomposite are 5–10 nm, obtained from TEM image. ► With W doping into ZnO photoinduced charge separation rate has been enhanced. ► Photocatalytic activity of the W-ZnO is much higher than that of undoped ZnO

Preparation of TiO2 Nanocrystallite Powders Coated with 9 mol% ZnO for Cosmetic Applications in Sunscreens

Directory of Open Access Journals (Sweden)

Moo-Chin Wang

2012-02-01

Full Text Available The preparation of TiO2 nanocrystallite powders coated with and without 9 mol% ZnO has been studied for cosmetic applications in sunscreens by a co-precipitation process using TiCl4 and Zn(NO32·6H2O as starting materials. XRD results show that the phases of anatase TiO2 and rutile TiO2 coexist for precursor powders without added ZnO (T-0Z and calcined at 523 to 973 K for 2 h. When the T-0Z precursor powders are calcined at 1273 K for 2 h, only the rutile TiO2 appears. In addition, when the TiO2 precursor powders contain 9 mol% ZnO (T-9Z are calcined at 873 to 973 K for 2 h, the crystallized samples are composed of the major phase of rutile TiO2 and the minor phases of anatase TiO2 and Zn2Ti3O8. The analyses of UV/VIS/NIR spectra reveal that the absorption of the T-9Z precursor powders after being calcined has a red-shift effect in the UV range with increasing calcination temperature. Therefore, the TiO2 nanocrystallite powders coated with 9 mol% ZnO can be used as the attenuate agent in the UV-A region for cosmetic applications in sunscreens.

Doping of ZnO nanowires using phosphorus diffusion from a spin-on doped glass source

International Nuclear Information System (INIS)

Bocheux, A.; Robin, I. C.; Bonaimé, J.; Hyot, B.; Feuillet, G.; Kolobov, A. V.; Fons, P.; Mitrofanov, K. V.; Tominaga, J.; Tamenori, Y.

2014-01-01

In this article, we report on ZnO nanowires that were phosphorus doped using a spin on dopant glass deposition and diffusion method. Photoluminescence measurements suggest that this process yields p-doped ZnO. The spatial location of P atoms was studied using x-ray near-edge absorption structure spectroscopy and it is concluded that the doping is amphoteric with P atoms located on both Zn and O sites

Sonochemical synthesis of Dy-doped ZnO nanostructures and their photocatalytic properties

Energy Technology Data Exchange (ETDEWEB)

Yayapao, Oranuch [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Thongtem, Titipun, E-mail: ttpthongtem@yahoo.com [Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Materials Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Phuruangrat, Anukorn, E-mail: phuruangrat@hotmail.com [Department of Materials Science and Technology, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112 (Thailand); Thongtem, Somchai [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Materials Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand)

2013-11-05

Highlights: •Undoped and Dy-doped ZnO used as photocatalysts. •They were synthesized by sonochemistry. •The promising materials for treatment of organic pollutants. -- Abstract: Dy-doped ZnO nanostructures were synthesized by a sonochemical method. The concentration effect of Dy on their phase, morphology, optical properties and photocatalytic activities was investigated. XRD patterns indicated that the as-synthesized 0–3% Dy-doped ZnO was hexagonal wurtzite structure. SEM and TEM show that the products were nanorods with their growth direction along the c axis. The photoluminescence spectrum of 3% Dy-doped ZnO, applied by Gaussian analysis, consists of three emission peaks at 376 nm, 448 nm and 487 nm. The photocatalytic activities of the as-synthesized products were determined from the degradation of methylene blue (C{sub 16}H{sub 18}N{sub 3}SCl) by UV radiation. In this research, the 3% Dy-doped ZnO showed the highest photocatalytic activity.

Sonochemical synthesis of Dy-doped ZnO nanostructures and their photocatalytic properties

International Nuclear Information System (INIS)

Yayapao, Oranuch; Thongtem, Titipun; Phuruangrat, Anukorn; Thongtem, Somchai

2013-01-01

Highlights: •Undoped and Dy-doped ZnO used as photocatalysts. •They were synthesized by sonochemistry. •The promising materials for treatment of organic pollutants. -- Abstract: Dy-doped ZnO nanostructures were synthesized by a sonochemical method. The concentration effect of Dy on their phase, morphology, optical properties and photocatalytic activities was investigated. XRD patterns indicated that the as-synthesized 0–3% Dy-doped ZnO was hexagonal wurtzite structure. SEM and TEM show that the products were nanorods with their growth direction along the c axis. The photoluminescence spectrum of 3% Dy-doped ZnO, applied by Gaussian analysis, consists of three emission peaks at 376 nm, 448 nm and 487 nm. The photocatalytic activities of the as-synthesized products were determined from the degradation of methylene blue (C 16 H 18 N 3 SCl) by UV radiation. In this research, the 3% Dy-doped ZnO showed the highest photocatalytic activity

Room temperature ferromagnetism in Mg-doped ZnO nanoparticles

International Nuclear Information System (INIS)

Singh, Jaspal; Vashihth, A.; Gill, Pritampal Singh; Verma, N. K.

2015-01-01

Zn 1-x Mg x O (x = 0, 0,10) nanoparticles were successfully synthesized using sol-gel method. X-ray diffraction (XRD) confirms that the synthesized nanoparticles possess wurtzite phase having hexagonal structure. Morphological analysis was carried out using transmission electron microscopy (TEM) which depicts the spherical morphology of ZnO nanoparticles. Energy dispersive spectroscopy (EDS) showed the presence of Mg in ZnO nanoparticles. Electron spin resonance (ESR) signal was found to be decreasing with increasing of Mg-doping concentration. The room temperature ferromagnetism was observed in undoped and Mg-doped ZnO nanoparticles. The increase of Mg-doping concentration resulted in decrease of saturation magnetization value which could be attributed to decrease of oxygen vacancies present in host nanoparticles

Mn doping in ZnO nanoparticles: effects investigated by positron lifetime and Doppler broadening studies

Energy Technology Data Exchange (ETDEWEB)

Roy, B.; Karmakar, B.; Pal, M. [Department of Physics, University of Burdwan, Golapbag, Burdwan (India); Nambissan, P.M.G. [Saha Institute of Nuclear Physics, Kolkata (India)

2009-11-15

Positron lifetime and Doppler broadening measurements in nanocrystalline zinc oxide (ZnO) indicated the negatively charged trivacancy-type defects V{sub Zn+O+Zn} as the predominant positron trapping sites within the nanocrystallites. They got converted to neutral divacancies (V{sub Zn+O}) on doping with manganese (Mn). Further doping resulted in the reduction of the size of the nanocrystallites. At still increased doping concentrations, a new phase ZnMn{sub 2}O{sub 4} was formed. It had a normal spinel structure with positron trapping centers at some of the tetrahedral and octahedral sites. X-ray diffraction and transmission electron micro-scopy studies confirmed these findings. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Al-Doped ZnO Monolayer as a Promising Transparent Electrode Material: A First-Principles Study

Directory of Open Access Journals (Sweden)

Mingyang Wu

2017-03-01

Full Text Available Al-doped ZnO has attracted much attention as a transparent electrode. The graphene-like ZnO monolayer as a two-dimensional nanostructure material shows exceptional properties compared to bulk ZnO. Here, through first-principle calculations, we found that the transparency in the visible light region of Al-doped ZnO monolayer is significantly enhanced compared to the bulk counterpart. In particular, the 12.5 at% Al-doped ZnO monolayer exhibits the highest visible transmittance of above 99%. Further, the electrical conductivity of the ZnO monolayer is enhanced as a result of Al doping, which also occurred in the bulk system. Our results suggest that Al-doped ZnO monolayer is a promising transparent conducting electrode for nanoscale optoelectronic device applications.

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.

Morphology evolution of hydrothermally grown ZnO nanostructures on gallium doping and their defect structures

Energy Technology Data Exchange (ETDEWEB)

Pineda-Hernandez, G. [Facultad de Ingenieria Quimica, Benemerita Universidad Autonoma de Puebla, C.P. 72570 Puebla, Pue. (Mexico); Escobedo-Morales, A., E-mail: alejandroescobedo@hotmail.com [Facultad de Ingenieria Quimica, Benemerita Universidad Autonoma de Puebla, C.P. 72570 Puebla, Pue. (Mexico); Pal, U. [Instituto de Fisica, Benemerita Universidad Autonoma de Puebla, Apdo. Postal J-48, C.P. 72570 Puebla, Pue. (Mexico); Chigo-Anota, E. [Facultad de Ingenieria Quimica, Benemerita Universidad Autonoma de Puebla, C.P. 72570 Puebla, Pue. (Mexico)

2012-08-15

In the present article, the effect of gallium doping on the morphology, structural, and vibrational properties of hydrothermally grown ZnO nanostructures has been studied. It has been observed that incorporated gallium plays an important role on the growth kinetics and hence on the morphology evolution of the ZnO crystals. Ga doping in high concentration results in the contraction of ZnO unit cell, mainly along c-axis. Although Ga has high solubility in ZnO, heavy doping promotes the segregation of Ga atoms as a secondary phase. Incorporated Ga atoms strongly affect the vibrational characteristics of ZnO lattice and induce anomalous Raman modes. Possible mechanisms of morphology evolution and origin of anomalous Raman modes in Ga doped ZnO nanostructures are discussed. -- Highlights: Black-Right-Pointing-Pointer Ga doped ZnO nanostructures were successfully grown by hydrothermal chemical route. Black-Right-Pointing-Pointer Ga doping has strong effect on the resulting morphology of ZnO nanostructures. Black-Right-Pointing-Pointer Anomalous vibrational modes in wurtzite ZnO lattice are induced by Ga doping. Black-Right-Pointing-Pointer Incorporated Ga atoms accommodate at preferential lattice sites.

Lattice locations and properties of Fe in Co/Fe co-implanted ZnO

DEFF Research Database (Denmark)

Gunnlaugsson, H.P.; Johnston, K.; Mølholt, T.E.

2012-01-01

The lattice locations and electronic configurations of Fe in 57Co/57Fe implanted ZnO (to (5‐6) × 1014 Fe/cm−2) have been studied by 57Fe Mössbauer emission spectroscopy. The spectra acquired upon room temperature implantation show ∼20% of the probe atoms as Fe2+ on perturbed Zn sites and the rema......The lattice locations and electronic configurations of Fe in 57Co/57Fe implanted ZnO (to (5‐6) × 1014 Fe/cm−2) have been studied by 57Fe Mössbauer emission spectroscopy. The spectra acquired upon room temperature implantation show ∼20% of the probe atoms as Fe2+ on perturbed Zn sites...... and the remaining fraction as Fe2+ in damage sites of interstitial character. After annealing at 773 K, ∼20% remain on crystalline sites, while the damage fraction has partly disappeared and instead a ∼30% fraction occurs as high‐spin Fe3+, presumably in precipitates. This suggests that precipitation of Co/Fe in ZnO...... likely takes place at relatively low temperatures, thus explaining some of the discrepancies in the literature regarding magnetic properties of 3d metal‐doped ZnO....

Mn{sup 2+} ions distribution in doped sol–gel deposited ZnO films

Energy Technology Data Exchange (ETDEWEB)

Stefan, Mariana, E-mail: mstefan@infim.ro [National Institute of Materials Physics, P.O. Box MG-7, 077125 Magurele (Romania); Ghica, Daniela; Nistor, Sergiu V.; Maraloiu, Adrian V. [National Institute of Materials Physics, P.O. Box MG-7, 077125 Magurele (Romania); Plugaru, Rodica [National Institute for R & D in Microtechnologies (IMT), Erou Iancu Nicolae Str. 126A, 077190 Bucharest (Romania)

2017-02-28

Highlights: • Several Mn{sup 2+} centers observed by EPR in sol–gel ZnO films. • Mn{sup 2+} ions localized at Zn{sup 2+} sites in ZnO grains and disordered ZnO phase. • Sixfold coordinated Mn{sup 2+} ions localized in inter-grain region. • Aggregated Mn in insular-like regions between ZnO grains in the ZnO:5%Mn film. • Aggregated Mn phase presence and distribution observed by EPR and EDX-STEM. - Abstract: The localization and distribution of the Mn{sup 2+} ions in two sol–gel deposited ZnO films doped with different manganese concentrations were investigated by electron paramagnetic resonance spectroscopy and analytical transmission electron microscopy. In the lightly doped sample the Mn{sup 2+} ions are mainly localized substitutionally at isolated tetrahedrally coordinated Zn{sup 2+} sites in both crystalline ZnO nanograins (34%) and surrounding disordered ZnO (52%). In the highly doped ZnO film, a much smaller proportion of manganese substitutes Zn{sup 2+} in the crystalline and disordered ZnO (10%). The main amount (85%) of manganese aggregates in a secondary phase as an insular-like distribution between the ZnO nanograins. The remaining Mn{sup 2+} ions (14% and 5% at low and high doping levels, respectively) are localized at isolated, six-fold coordinated sites, very likely in the disordered intergrain region. Annealing at 600 °C induced changes in the Mn{sup 2+} ions distribution, reflecting the increase of the ZnO crystallization degree, better observed in the lightly doped sample.

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

International Nuclear Information System (INIS)

Xu, Linhua; Zheng, Gaige; Zhao, Lilong; Pei, Shixin

2015-01-01

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

Dielectric and magnetic properties of (Zn, Co) co-doped SnO2 nanoparticles

International Nuclear Information System (INIS)

Rajwali, Khan; Fang Ming-Hu

2015-01-01

Polycrystalline samples of (Zn, Co) co-doped SnO 2 nanoparticles were prepared using a co-precipitation method. The influence of (Zn, Co) co-doping on electrical, dielectric, and magnetic properties was studied. All of the (Zn, Co) co-doped SnO 2 powder samples have the same tetragonal structure of SnO 2 . A decrease in the dielectric constant was observed with the increase of Co doping concentration. It was found that the dielectric constant and dielectric loss values decrease, while AC electrical conductivity increases with doping concentration and frequency. Magnetization measurements revealed that the Co doping SnO 2 samples exhibits room temperature ferromagnetism. Our results illustrate that (Zn, Co) co-doped SnO 2 nanoparticles have an excellent dielectric, magnetic properties, and high electrical conductivity than those reported previously, indicating that these (Zn, Co) co-doped SnO 2 materials can be used in the field of the ultrahigh dielectric material, high frequency device, and spintronics. (paper)

Efficient acetone sensor based on Ni-doped ZnO nanostructures prepared by spray pyrolysis technique

Science.gov (United States)

Darunkar, Swapnil S.; Acharya, Smita A.

2018-05-01

Ni-doped ZnO thin film was prepared by home-built spray pyrolysis unit for the detection of acetone at 300°C. Scanning electron microscopic (SEM) images of as-developed thin film of undoped ZnO exhibits large quantity of spherical, non-agglomerated particles with uniform size while in Ni-doped ZnO, particles are quite non-uniform in nature. The particle size estimated by using image J are obtained to be around 20-200 nm. Ni-doping effect on band gaps are determined by UV-vis optical spectroscopy and band gap of Ni-doped ZnO is found to be 3.046 eV. Nickel doping exceptionally enhances the sensing response of ZnO as compared to undoped ZnO system. The major role of the Ni-doping is to create more active sites for chemisorbed oxygen on the surface of sensor and correspondingly, to improve the sensing response. The 6 at.% of Ni-doped ZnO exhibits the highest response (92%) for 100 ppm acetone at 300 °C.

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

Room-temperature ferromagnetic properties of Cu-doped ZnO rod ...

Indian Academy of Sciences (India)

We have investigated properties of the Cu-doped ZnO crystalline film synthesized by the hydrothermal method. X-ray diffraction and X-ray ... DMSs are semiconducting alloys whose lattice is made up in part of substitutional magnetic ... investigate Cu-doped ZnO system (Hou et al 2007a, b), as. Cu is a potential magnetic ion ...

Synthesis of Doped and non-Doped Nano MgO Ceramic Membranes

Directory of Open Access Journals (Sweden)

Shiraz Labib

2013-12-01

Full Text Available Doped and non-doped MgO coated thin films on alumina substrates were prepared using a chelating sol-gel method under controlled conditions to prepare nanomaterials with unprecedented properties. The effect of doping of ZnO on thermal, surface and structural properties was investigated using DTA-TG, BET and XRD respectively. Also microstructural studies and coating thickness measurements of MgO thin film were conducted using SEM. An increase in the thermal stability of MgO with increasing ZnO doping percent was observed. The increase of ZnO doping percent showed a marked decrease in the average particle size of MgO powder as a result of the replacement of some Mg2+ by Zn2+ which has similar ionic radius as Mg2+. This decrease in particle size of MgO was also related to the decrease of the degree of MgO crystalinity. The increase of ZnO doping also showed a marked decrease in coating thickness values of the prepared membranes. This decrease was related to the  mechanism of ZnO doping into a MgO crystal lattice.

Photoelectrochemical performance of N-doped ZnO branched nanowire photoanodes

Directory of Open Access Journals (Sweden)

Shrok Allami

2017-10-01

Full Text Available A ZnO branched-nanowire (BNW photoanode was doped with N for use in a photoelectrochemical cell (PEC to generate H2 from water splitting. First, ZnO BNWs were synthesized by chemical bath deposition method. Two experimental methods were used for N-doping: the time-controlled direct-current glow discharge plasma (DCGDP and the DC magnetron plasma (DCMP methods, to optimize N-doping of the NW structure. X-ray photoelectron spectroscopy (XPS provided the N distribution and atomic percentage in the BNWs. The XPS results confirmed that N distribution into ZnO BNWs occurred by N substitution of O sites in the ZnO structure and through well-screened molecular N2. The morphologies and structures of the fabricated nanostructures were investigated by field-emission scanning electron microscopy and X-ray diffraction respectively. The photoanode performance was demonstrated in photoelectrochemical studies at various power densities under both dark and illuminated conditions. Increasing the N amount in the ZnO BNWs increased the photocurrent in the PEC. Keywords: Engineering, Condensed matter physics, Nanotechnology, Materials science

Structural, optical, and LED characteristics of ZnO and Al doped ZnO thin films

Science.gov (United States)

Sandeep, K. M.; Bhat, Shreesha; Dharmaprakash, S. M.

2017-05-01

ZnO (pristine) and Al doped ZnO (AZO) films were prepared using sol-gel spin coating method. The XRD analysis showed the enhanced compressive stress in AZO film. The presence of extended states below the conduction band edge in AZO accounts for the redshift in optical bandgap. The PL spectra of AZO showed significant blue emission due to the carrier recombination from defect states. The TRPL curves showed the dominant DAP recombination in ZnO film, whereas defect related recombination in Al doped ZnO film. Color parameters viz: the dominant wavelength, color coordinates (x,y), color purity, luminous efficiency and correlated color temperature (CCT) of ZnO and AZO films are calculated using 1931 (CIE) diagram. Further, a strong blue emission with color purity more than 96% is observed in both the films. The enhanced blue emission in AZO significantly increased the luminous efficiency (22.8%) compared to ZnO film (10.8%). The prepared films may be used as blue phosphors in white light generation.

A vanadium-doped ZnO nanosheets-polymer composite for flexible piezoelectric nanogenerators

Science.gov (United States)

Shin, Sung-Ho; Kwon, Yang Hyeog; Lee, Min Hyung; Jung, Joo-Yun; Seol, Jae Hun; Nah, Junghyo

2016-01-01

We report high performance flexible piezoelectric nanogenerators (PENGs) by employing vanadium (V)-doped ZnO nanosheets (NSs) and the polydimethylsiloxane (PDMS) composite structure. The V-doped ZnO NSs were synthesized to overcome the inherently low piezoelectric properties of intrinsic ZnO. Ferroelectric phase transition induced in the V-doped ZnO NSs contributed to significantly improve the performance of the PENGs after the poling process. Consequently, the PENGs exhibited high output voltage and current up to ~32 V and ~6.2 μA, respectively, under the applied strain, which are sufficient to directly turn on a number of light emitting diodes (LEDs). The composite approach for PENG fabrication is scalable, robust, and reproducible during periodic bending/releasing over extended cycles. The approach introduced here extends the performance limits of ZnO-based PENGs and demonstrates their potential as energy harvesting devices.We report high performance flexible piezoelectric nanogenerators (PENGs) by employing vanadium (V)-doped ZnO nanosheets (NSs) and the polydimethylsiloxane (PDMS) composite structure. The V-doped ZnO NSs were synthesized to overcome the inherently low piezoelectric properties of intrinsic ZnO. Ferroelectric phase transition induced in the V-doped ZnO NSs contributed to significantly improve the performance of the PENGs after the poling process. Consequently, the PENGs exhibited high output voltage and current up to ~32 V and ~6.2 μA, respectively, under the applied strain, which are sufficient to directly turn on a number of light emitting diodes (LEDs). The composite approach for PENG fabrication is scalable, robust, and reproducible during periodic bending/releasing over extended cycles. The approach introduced here extends the performance limits of ZnO-based PENGs and demonstrates their potential as energy harvesting devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07185b

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.

Modulation-Doped In2O3/ZnO Heterojunction Transistors Processed from Solution

KAUST Repository

Khim, Dongyoon

2017-03-15

This paper reports the controlled growth of atomically sharp In2 O3 /ZnO and In2 O3 /Li-doped ZnO (In2 O3 /Li-ZnO) heterojunctions via spin-coating at 200 °C and assesses their application in n-channel thin-film transistors (TFTs). It is shown that addition of Li in ZnO leads to n-type doping and allows for the accurate tuning of its Fermi energy. In the case of In2 O3 /ZnO heterojunctions, presence of the n-doped ZnO layer results in an increased amount of electrons being transferred from its conduction band minimum to that of In2 O3 over the interface, in a process similar to modulation doping. Electrical characterization reveals the profound impact of the presence of the n-doped ZnO layer on the charge transport properties of the isotype In2 O3 /Li-ZnO heterojunctions as well as on the operating characteristics of the resulting TFTs. By judicious optimization of the In2 O3 /Li-ZnO interface microstructure, and Li concentration, significant enhancement in both the electron mobility and TFT bias stability is demonstrated.

Modulation-Doped In2O3/ZnO Heterojunction Transistors Processed from Solution

KAUST Repository

Khim, Dongyoon; Lin, Yen-Hung; Nam, Sungho; Faber, Hendrik; Tetzner, Kornelius; Li, Ruipeng; Zhang, Qiang; Li, Jun; Zhang, Xixiang; Anthopoulos, Thomas D.

2017-01-01

This paper reports the controlled growth of atomically sharp In2 O3 /ZnO and In2 O3 /Li-doped ZnO (In2 O3 /Li-ZnO) heterojunctions via spin-coating at 200 °C and assesses their application in n-channel thin-film transistors (TFTs). It is shown that addition of Li in ZnO leads to n-type doping and allows for the accurate tuning of its Fermi energy. In the case of In2 O3 /ZnO heterojunctions, presence of the n-doped ZnO layer results in an increased amount of electrons being transferred from its conduction band minimum to that of In2 O3 over the interface, in a process similar to modulation doping. Electrical characterization reveals the profound impact of the presence of the n-doped ZnO layer on the charge transport properties of the isotype In2 O3 /Li-ZnO heterojunctions as well as on the operating characteristics of the resulting TFTs. By judicious optimization of the In2 O3 /Li-ZnO interface microstructure, and Li concentration, significant enhancement in both the electron mobility and TFT bias stability is demonstrated.

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

Energy Technology Data Exchange (ETDEWEB)

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

2015-07-15

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

Synthesis of S-doped ZnO by the interaction of sulfur with zinc salt in PEG200

International Nuclear Information System (INIS)

Xie, Xin-Yuan; Zhan, Pei; Li, Li-Yun; Zhou, Dan-Jie; Guo, Dan-Yi; Meng, Jian-Xin; Bai, Yan; Zheng, Wen-Jie

2015-01-01

Graphical abstract: S-doped ZnO nanoparticles (S-ZnO) were synthesized via a one-step and green method by using zinc acetate dihydrate as a precursor, S powder as a dopant and PEG200 as a solvent with the number of moles of sulfur (n S ) smaller than that of zinc salt (n Zn ). A possible mechanism was proposed to elucidate the formation of S-ZnO. PL spectra show strong green emission band, which could be applied to ZnO optoelectronic devices that work in the visible spectrum. - Highlights: • A green and one-step method was developed to synthesize S-doped ZnO nanoparticles. • The molar ratio of Zn(II) and S influences the composition of the products greatly. • The interactive mechanism of S with zinc salt in PEG was elucidated. • PL spectra of S-doped ZnO nanoparticles show strong green emission band. - Abstract: S-doped ZnO nanoparticles (S-ZnO) were synthesized via a one-step and green method. In this method, zinc acetate dihydrate was used as a precursor and sulfur was the dopant. The reaction between zinc salt and S occurred in PEG200 media. X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, UV–Vis spectroscopy and room temperature photoluminescence were used to characterize the products. The results show that the molar ratio of Zn(II) and S determines the composition, structure, surface morphology, and luminescence properties of the products greatly. When the number of moles of sulfur (n S ) is smaller than that of zinc salt (n Zn ), the products are S-ZnO with diameters of 40–55 nm and they have ultraviolet absorption peaks at 363 nm. The incorporation of S into ZnO is supported by broadening and lower Bragg angle shift in XRD pattern. FTIR spectra show that PEG200 adsorbs onto the surfaces of the S-ZnO as a capping agent. PL spectra show that the effective sulfur doping

High power density cell using nanostructured Sr-doped SmCoO3 and Sm-doped CeO2 composite powder synthesized by spray pyrolysis

Science.gov (United States)

Shimada, Hiroyuki; Yamaguchi, Toshiaki; Suzuki, Toshio; Sumi, Hirofumi; Hamamoto, Koichi; Fujishiro, Yoshinobu

2016-01-01

High power density solid oxide electrochemical cells were developed using nanostructure-controlled composite powder consisting of Sr-doped SmCoO3 (SSC) and Sm-doped CeO2 (SDC) for electrode material. The SSC-SDC nano-composite powder, which was synthesized by spray pyrolysis, had a narrow particle size distribution (D10, D50, and D90 of 0.59, 0.71, and 0.94 μm, respectively), and individual particles were spherical, composing of nano-size SSC and SDC fragments (approximately 10-15 nm). The application of the powder to a cathode for an anode-supported solid oxide fuel cell (SOFC) realized extremely fine cathode microstructure and excellent cell performance. The anode-supported SOFC with the SSC-SDC cathode achieved maximum power density of 3.65, 2.44, 1.43, and 0.76 W cm-2 at 800, 750, 700, and 650 °C, respectively, using humidified H2 as fuel and air as oxidant. This result could be explained by the extended electrochemically active region in the cathode induced by controlling the structure of the starting powder at the nano-order level.

A detailed study on Sn4+ doped ZnO for enhanced photocatalytic degradation

Science.gov (United States)

Beura, Rosalin; Pachaiappan, R.; Thangadurai, P.

2018-03-01

The samples of Sn4+ doped (1, 5, 10, 15, 20 & 30%) ZnO nanostructures were synthesized by a low temperature hydrothermal method. Structural analysis by XRD and Raman spectroscopy showed the hexagonal wurtzite phase of ZnO and the formation of a secondary phase Zn2SnO4 beyond 10% doping of Sn4+. Microstructural analysis by TEM also confirmed the wurtzite ZnO with rod as well as particle like structure. Presence of various functional groups (sbnd OH, sbnd CH, Znsbnd O) were confirmed by FTIR. Optical properties were studied by UV-vis absorption, photoluminescence emission spectroscopies and lifetime measurement. Band gap of the undoped and Sn4+ doped ZnO were analyzed by Tauc plot and it was observed that the band gap of the materials had slightly decreased from 3.2 to 3.16 eV and again increased to 3.23 eV with respect to the increase in the doping concentration from 1 to 30%. A significant change was also noticed in the photoluminescence emission properties of ZnO i.e. increase in the intensity of NBE emission and decrease in DLE, on subject to Sn4+ doping. Average PL lifetime had increased from 29.45 ns for ZnO to 30.62 ns upon 1% Sn ion doping in ZnO. Electrical properties studied by solid state impedance spectroscopy showed that the conductivity had increased by one order of magnitude (from 7.48×10-8 to 2.21×10-7 S/cm) on Sn4+ doping. Photocatalytic experiments were performed on methyl orange (MO) as a model industrial dye under UV light irradiation for different irradiation times. The optimum Sn4+ content in order to achieve highest photocatalytic activity was found to be 1% Sn 4+ doping. The enhancement was achieved due to a decrease in the band gap favoring the generation of electron-hole pairs and the enhanced PL life time that delays the recombination of these charge carrier formation. The third reason was that the increased electrical conductivity that indicated the faster charge transfer in this material to enhance the photocatalytic activity. The Sn

Synthesis and characterization of Mg-doped ZnO hollow spheres

International Nuclear Information System (INIS)

Hammad, Talaat M.; Salem, Jamil K.

2011-01-01

Mg-doped ZnO nanoparticles were synthesized by a simple chemical method at low temperature with Mg:Zn atomic ratio from 0 to 7%. The synthesis process is based on the hydrolysis of zinc acetate dihydrate and magnesium acetate tetrahydrate were heated under refluxing at 65 °C using methanol as a solvent. X-ray diffraction analysis reveals that the Mg-doped ZnO crystallizes in a wurtzite structure with crystal size of 5–12 nm. These nanocrystals self-aggregated themselves into hollow spheres of size of 800–1100 nm. High resolution transmission electron microscopy images show that each sphere is made up of numerous nanoparticles of average diameter 5–11 nm. The XRD patterns, SEM and TEM micrographs of doping of Mg in ZnO confirmed the formation of hollow spheres indicating that the Mg 2+ is successfully substituted into the ZnO host structure of the Zn 2+ site. Furthermore, the UV–Vis spectra and photoluminescence (PL) spectra of the ZnO nanoparticles were also investigated. The band gap of the nanoparticles can be tuned in the range of 3.36–3.55 eV by the use of the dopants.

Enhanced luminescence in Eu-doped ZnO nanocrystalline films

Energy Technology Data Exchange (ETDEWEB)

Suzuki, Keigo, E-mail: ksuzuki@murata.com; Murayama, Koji; Tanaka, Nobuhiko [Murata Manufacturing Co., Ltd., 10-1, Higashikotari 1-chome, Nagaokakyo, Kyoto 617-8555 (Japan)

2015-07-20

We found an enhancement of Eu{sup 3+} emissions in Eu-doped ZnO nanocrystalline films fabricated by microemulsion method. The Eu{sup 3+} emission intensities were increased by reducing annealing temperatures from 633 K to 533 K. One possible explanation for this phenomenon is that the size reduction enhances the energy transfer from ZnO nanoparticles to Eu{sup 3+} ions. Also, the shift of the charge-transfer band into the low-energy side of the absorption edge is found to be crucial, which seems to expedite the energy transfer from O atoms to Eu{sup 3+} ions. These findings will be useful for the material design of Eu-doped ZnO phosphors.

Improving the selective cancer killing ability of ZnO nanoparticles using Fe doping.

Science.gov (United States)

Thurber, Aaron; Wingett, Denise G; Rasmussen, John W; Layne, Janet; Johnson, Lydia; Tenne, Dmitri A; Zhang, Jianhui; Hanna, Charles B; Punnoose, Alex

2012-06-01

This work reports a new method to improve our recent demonstration of zinc oxide (ZnO) nanoparticles (NPs) selectively killing certain human cancer cells, achieved by incorporating Fe ions into the NPs. Thoroughly characterized cationic ZnO NPs (∼6 nm) doped with Fe ions (Zn(1-x )Fe (x) O, x = 0-0.15) were used in this work, applied at a concentration of 24 μg/ml. Cytotoxicity studies using flow cytometry on Jurkat leukemic cancer cells show cell viability drops from about 43% for undoped ZnO NPs to 15% for ZnO NPs doped with 7.5% Fe. However, the trend reverses and cell viability increases with higher Fe concentrations. The non-immortalized human T cells are markedly more resistant to Fe-doped ZnO NPs than cancerous T cells, confirming that Fe-doped samples still maintain selective toxicity to cancer cells. Pure iron oxide samples displayed no appreciable toxicity. Reactive oxygen species generated with NP introduction to cells increased with increasing Fe up to 7.5% and decreased for >7.5% doping.

Precipitated nickel doped ZnO nanoparticles with enhanced low temperature ethanol sensing properties

Directory of Open Access Journals (Sweden)

Umadevi Godavarti

2017-12-01

Full Text Available The Zn1-xNixO nanoparticles have been synthesized by novel co-precipitation method and systematically characterized by XRD, SEM, TEM and photo luminescence. The XRD patterns confirm the hexagonal wurzite structure without secondary phases in Ni substituted ZnO samples. SEM and TEM are used for the estimation of particle shape and size. In PL study there is a peak in the range of 380–390 nm in all samples that is attributed to the oxygen vacancies. Gas sensing tests reveal that Ni doped ZnO sensor has remarkably enhanced performance compared to pure ZnO detected at an optimum temperature 100 °C. It could detect ethanol gas in a wide concentration range with very high response, fast response–recovery time, good selectivity and stable repeatability. The possible sensing mechanism is discussed. The high response of ZnO Nanoparticles was attributed to large contacting surface area for electrons, oxygen, target gas molecule, and abundant channels for gas diffusion. The superior sensing features indicate the present Ni doped ZnO as a promising nanomaterial for gas sensors. The response time and recovery time of undoped is 75 s and 60 s and 0.25 at% Ni are found to be 60 s and 45 s at 100 °C respectively.

Effect of nickel doping concentration on structural and magnetic properties of ultrafine diluted magnetic semiconductor ZnO nanoparticles

International Nuclear Information System (INIS)

Sharma, Prashant K.; Dutta, Ranu K.; Pandey, Avinash C.

2009-01-01

The ZnO:Ni 2+ nanoparticles of mean size 2-12 nm were synthesized at room temperature by the simple co-precipitation method. The crystallite structure, morphology and size were determined by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). The wurtzite structure of ZnO gradually degrades with the increasing Ni doping concentration and an additional NiO-associated diffraction peak was observed above 15% of Ni 2+ doping. The change in magnetic behavior of the nanoparticles of ZnO with varying Ni 2+ doping concentration was investigated using a vibrating sample magnetometer (VSM). Initially, these nanoparticles showed strong ferromagnetic behavior, however, at higher doping percentage of Ni 2+ , the ferromagnetic behavior was suppressed and paramagnetic nature was observed. The enhanced antiferromagnetic interaction between neighboring Ni-Ni ions suppressed the ferromagnetism at higher doping concentrations of Ni 2+ .

Spectral features and antibacterial properties of Cu-doped ZnO nanoparticles prepared by sol-gel method

Science.gov (United States)

Alireza, Samavati; A, F. Ismail; Hadi, Nur; Z, Othaman; M, K. Mustafa

2016-07-01

Zn1-x Cu x O (x = 0.00, 0.01, 0.03, and 0.05) nanoparticles are synthesized via the sol-gel technique using gelatin and nitrate precursors. The impact of copper concentration on the structural, optical, and antibacterial properties of these nanoparticles is demonstrated. Powder x-ray diffraction investigations have illustrated the organized Cu doping into ZnO nanoparticles up to Cu concentration of 5% (x = 0.05). However, the peak corresponding to CuO for x = 0.01 is not distinguishable. The images of field emission scanning electron microscopy demonstrate the existence of a nearly spherical shape with a size in the range of 30-52 nm. Doping Cu creates the Cu-O-Zn on the surface and results in a decrease in the crystallite size. Photoluminescence and absorption spectra display that doping Cu causes an increment in the energy band gap. The antibacterial activities of the nanoparticles are examined against Escherichia coli (Gram negative bacteria) cultures using optical density at 600 nm and a comparison of the size of inhibition zone diameter. It is found that both pure and doped ZnO nanoparticles indicate appropriate antibacterial activity which rises with Cu doping. Project supported by the Universiti Teknologi Malaysia (UTM) (Grant No. R. J1300000.7809.4F626). Dr. Samavati is thankful to RMC for postdoctoral grants.

Structural, optical, photoluminescence and photocatalytic assessment of Sr-doped ZnO nanoparticles

International Nuclear Information System (INIS)

Pradeev Raj, K.; Sadaiyandi, K.; Kennedy, A.; Thamizselvi, R.

2016-01-01

ZnO nanoparticles (NPs) and Strontium doped ZnO nanoparticles (2–6 mol %) (SZ-NPs) were synthesized via Co-precipitation method. Synthesized samples were investigated by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Elemental dispersive spectroscopy (EDS), UV–visible, and Photoluminescence (PL) spectroscopy. Photocatalytic studies for Rhodamine B (RhB) dye in aqueous solution under UV–Vis radiation. XRD analysis confirms that all the samples have hexagonal wurtzite structure. The average crystallite size of the nanoparticles was in the range of 29–51 nm. From the Williamson –Hall (W-H) plot, a positive slope is inferred for pure and SZ-NPs, confirming the presence of tensile strain. SEM images reveal the synthesized NPs are in nanometer range with various shapes are observed. The presence of strontium (Sr) in the host lattice was confirmed by EDS spectroscopy. The optical analysis shows the absorption decreases on doping and shifts slightly towards the longer wavelength region. The band gap energy (Eg) decreases (3.32–3.03 eV) with the increase of Sr dopant concentration. The photoluminescence (PL) spectrum reveals the UV emission is strong near the band-edge region (NBE) (392 nm) and intrinsic defects resulted in series of Vis emissions around 400–560 nm. Kinetic studies on RhB dye indicates the degradation rate has increased with dopant concentration. The improved photocatalytic activity is observed due to the efficient charge separation, improved visible light absorption, inhibition of the electron-hole pair's recombination and better adsorptive of RhB dye molecule on the surface of SZ-NPs. Moreover, the reduction in the total organic carbon (TOC) results reveals the improved photocatalytic activity of strontium doped ZnO NPs. - Highlights: • Effective synthesis of ZnO and Sr−ZnO nanoparticles by co-precipitation method. • Samples were characterized by XRD, SEM, EDS, UV–Vis and PL technique. • Higher optical absorption and

Structural, optical, photoluminescence and photocatalytic assessment of Sr-doped ZnO nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Pradeev Raj, K., E-mail: pradeevraj@gmail.com [Research and Development Centre, Bharathiar University, Coimbatore, 641 046, Tamilnadu (India); Department of Physics, CSI College of Engineering, Ooty, The Nilgiris, 643 215, Tamil Nadu (India); Sadaiyandi, K. [Department of Physics, Alagappa Government Arts College, Karaikudi, Sivagangai, 630 003, Tamil Nadu (India); Kennedy, A. [Department of Physics, CSI College of Engineering, Ooty, The Nilgiris, 643 215, Tamil Nadu (India); Thamizselvi, R. [Department of Chemistry, L.R.G. Govt Arts College for Women, Tirupur, 641604, Tamil Nadu (India)

2016-11-01

ZnO nanoparticles (NPs) and Strontium doped ZnO nanoparticles (2–6 mol %) (SZ-NPs) were synthesized via Co-precipitation method. Synthesized samples were investigated by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Elemental dispersive spectroscopy (EDS), UV–visible, and Photoluminescence (PL) spectroscopy. Photocatalytic studies for Rhodamine B (RhB) dye in aqueous solution under UV–Vis radiation. XRD analysis confirms that all the samples have hexagonal wurtzite structure. The average crystallite size of the nanoparticles was in the range of 29–51 nm. From the Williamson –Hall (W-H) plot, a positive slope is inferred for pure and SZ-NPs, confirming the presence of tensile strain. SEM images reveal the synthesized NPs are in nanometer range with various shapes are observed. The presence of strontium (Sr) in the host lattice was confirmed by EDS spectroscopy. The optical analysis shows the absorption decreases on doping and shifts slightly towards the longer wavelength region. The band gap energy (Eg) decreases (3.32–3.03 eV) with the increase of Sr dopant concentration. The photoluminescence (PL) spectrum reveals the UV emission is strong near the band-edge region (NBE) (392 nm) and intrinsic defects resulted in series of Vis emissions around 400–560 nm. Kinetic studies on RhB dye indicates the degradation rate has increased with dopant concentration. The improved photocatalytic activity is observed due to the efficient charge separation, improved visible light absorption, inhibition of the electron-hole pair's recombination and better adsorptive of RhB dye molecule on the surface of SZ-NPs. Moreover, the reduction in the total organic carbon (TOC) results reveals the improved photocatalytic activity of strontium doped ZnO NPs. - Highlights: • Effective synthesis of ZnO and Sr−ZnO nanoparticles by co-precipitation method. • Samples were characterized by XRD, SEM, EDS, UV–Vis and PL technique. • Higher optical absorption

Enhancement of exciton radiative recombination for In-doped ZnO nanowires with aluminum cylindrical micropillars

Energy Technology Data Exchange (ETDEWEB)

Wang, Jen-Cheng; Liang, Yu-Ting; Cheng, Fang-Ching; Fang, Chia-Hui; Chen, Hung-Ing; Tsai, Chung-Yuan [Graduate Institute of Electro-Optical Engineering and Department of Electronic Engineering, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-Shan, Tao-Yuan 333, Taiwan, ROC (China); Jiang, Joe-Air [Department of Bio-Industrial Mechatronics Engineering, National Taiwan University, Taipei 106, Taiwan, ROC (China); Nee, Tzer-En, E-mail: neete@mail.cgu.edu.tw [Graduate Institute of Electro-Optical Engineering and Department of Electronic Engineering, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-Shan, Tao-Yuan 333, Taiwan, ROC (China)

2013-04-15

Zinc oxide (ZnO) has attracted intensive research effort in recent years, due to its unique properties and versatile applications. Recent work on the conservation of surface plasmon (SP) and light through period metal arrays has elucidated the propagation of SP resonance behavior. In this paper, we discuss the enhancement of exciton radiative recombination of the ZnO nanowires with Al cylindrical micropillars. Optical characterization of exciton interacted with SP resonance for indium-doped ZnO nanowires with Al cylindrical micropillars has been also investigated. From photoluminescence spectra of In-doped ZnO nanowires, it is found that the In-doped ZnO nanowires have a blue emission at 425 nm, which resulted from the ZnO band-to-band transition. Prior to the arrays of samples were annealed, a broad green emission centered at 500 nm was observed, which is attributed to ZnO native point defects. The relatively strong green band emission results from the radiative recombination that arises from the ionized oxygen vacancy and surface-defect related luminescence. Compare the In-doped ZnO on Si substrate, the enhancement of PL intensity for In-doped ZnO with deposited Al pattern film can be attributed to strong interaction with SP resonance and exciton over a broad temperature range. These experimental results indicate that Al cylindrical micropillars can significantly enhance carrier confinement and increase the quantum efficiency of In-doped ZnO/Al heterostructures due to the interaction of SP resonance between the In-doped ZnO nanowires and Al cylindrical micropillar structures, the surface-defect related luminescence, and the auxiliary test structures with variable micropillar parameters. -- Highlights: ► We examine the exciton radiative recombination of the ZnO nanowires. ► Al cylindrical micropillars affect the carrier recombination of ZnO/Al structures. ► The interaction of SP resonance between In-doped ZnO nanowire and Al pattern film. ► The carrier

First principles study of magneto-optical properties of Fe-doped ZnO

Energy Technology Data Exchange (ETDEWEB)

Shaoqiang, Guo [College of Science, Inner Mongolia University of Technology, Hohhot 010051 (China); Qingyu, Hou, E-mail: by0501119@126.com [College of Science, Inner Mongolia University of Technology, Hohhot 010051 (China); Zhenchao, Xu [College of Science, Inner Mongolia University of Technology, Hohhot 010051 (China); Chunwang, Zhao [College of Science, Inner Mongolia University of Technology, Hohhot 010051 (China); College of Arts and Sciences, Shanghai Maritime University, Shanghai 201306 (China)

2016-12-15

Studies on optical band gaps and absorption spectra of Fe-doped ZnO have conflicting conclusions, such as contradictory redshifted and blueshifted spectra. To solve this contradiction, we constructed models of un-doped and Fe-doped ZnO using first-principles theory and optimized the geometry of the three models. Electronic structures and absorption spectra were also calculated using the GGA+U method. Higher doping content of Fe resulted in larger volume of doped system, and higher total energy resulted in lower stability. Higher formation energy also led to more difficult doping. Meanwhile, the band gaps broadened and the absorption spectra exhibited an evident blue shift. The calculations were in good agreement with the experimental results. Given the unipolar structure of ZnO, four possible magnetic coupling configurations for Zn{sub 14}Fe{sub 2}O{sub 16} were calculated to investigate the magnetic properties. Results suggest that Fe doping can improve ferromagnetism in the ZnO system and that ferromagnetic stabilization was mediated by p–d exchange interaction between Fe-3d and O-2p orbitals. Therefore, the doped system is expected to obtain high stability and high Curie temperature of diluted magnetic semiconductor material, which are useful as theoretical bases for the design and preparation of the Fe-doped ZnO system’s magneto-optical properties. - Highlights: • A biomonitoring tool for the freshwater zone of template estuaries. • Water quality characterization related to nutrients and organic matter enrichment. • The percentage of a group of 24 tolerant species were capable of detecting the impairment of the water quality. • Characterization of morpho-functional traits of the selected tolerant species.

Doped titanium dioxide nanocrystalline powders with high photocatalytic activity

International Nuclear Information System (INIS)

Castro, A.L.; Nunes, M.R.; Carvalho, M.D.; Ferreira, L.P.; Jumas, J.-C.; Costa, F.M.; Florencio, M.H.

2009-01-01

Doped titanium dioxide nanopowders (M:TiO 2 ; M=Fe, Co, Nb, Sb) with anatase structure were successfully synthesized through an hydrothermal route preceded by a precipitation doping step. Structural and morphological characterizations were performed by powder XRD and TEM. Thermodynamic stability studies allowed to conclude that the anatase structure is highly stable for all doped TiO 2 prepared compounds. The photocatalytic efficiency of the synthesized nanopowders was tested and the results showed an appreciable enhancement in the photoactivity of the Sb:TiO 2 and Nb:TiO 2 , whereas no photocatalytic activity was detected for the Fe:TiO 2 and Co:TiO 2 nanopowders. These results were correlated to the doping ions oxidation states, determined by Moessbauer spectroscopy and magnetization data. - Graphical abstract: Doped titanium dioxide nanopowders (M:TiO 2 ; M=Fe, Co, Nb, Sb) with highly stable anatase structure were successfully synthesized through an hydrothermal route. The photocatalytic efficiencies of the synthesized nanopowders were tested and the results show an appreciable enhancement in the photoactivity of the Sb:TiO 2 and Nb:TiO 2 .

Half-metallic ferromagnetism in Cu-doped zinc-blende ZnO from first principles study

International Nuclear Information System (INIS)

Li, X.F.; Zhang, J.; Xu, B.; Yao, K.L.

2012-01-01

Electronic structures and magnetism of Cu-doped zinc-blende ZnO have been investigated by the first-principle method based on density functional theory (DFT). The results show that Cu can induce stable ferromagnetic ground state. The magnetic moment of supercell including single Cu atom is 1.0 μ B . Electronic structure shows that Cu-doped zinc-blende ZnO is a p-type half-metallic ferromagnet. The half-metal property is mainly attribute to the crystal field splitting of Cu 3d orbital, and the ferromagnetism is dominated by the hole-mediated double exchange mechanism. Therefore, Cu-doped zinc-blende ZnO should be useful in semiconductor spintronics and other applications. - Highlights: → Magnetism of Cu-doped zinc-blende ZnO. → Cu-doped zinc-blende ZnO shows interesting half-metal character. → Total energies calculations reveal that Cu can induce ferromagnetic ground state. → Ferromagnetism dominated by the hole-mediated double exchange mechanism.

Explanation of ferromagnetism origin in N-doped ZnO by first ...

Indian Academy of Sciences (India)

Moreover, ZnO doped with. 3d TM elements has been studied widely since the model calculation by Dietl et al predicted the possibility of ferro- magnetism in ZnO with a small amount of Mn as an impurity. [4]. However, TM doping often suffers from the problems related to precipitates or secondary phase formation undesir-.

Preparation, structural and optical characterization of ZnO, ZnO: Al nanopowder

Energy Technology Data Exchange (ETDEWEB)

Mohan, R. Raj [Department of ECE, Gojan School of Business and Technology, Chennai (India); Rajendran, K. [Department of Electronics, Government Arts College for Women, Ramanathapuram, TN (India); Sambath, K. [Department of ECS, Sri Krishna Arts and Science College, Coimbatore, TN (India)

2014-01-28

In this paper, ZnO and ZnO:Al nanopowders have been synthesized by low cost hydrothermal method. Zinc nitrate, hexamethylenetetramine (HMT) and aluminium nitrate are used as precursors for ZnO and AZO with different molar ratios. The structural and optical characterization of doped and un-doped ZnO powders have been investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDAX), photoluminescence (PL) and ultra violet visible (UV-Vis) absorption studies. The SEM results show that the hydrothermal synthesis can be used to obtain nanoparticles with different morphology. It is observed that the grain size of the AZO nanoparticles increased with increasing of Al concentration. The PL measurement of AZO shows that broad range of green emission around 550nm with high intensity. The green emission resulted mainly because of intrinsic defects.

Sonochemical synthesis and photocatalytic property of zinc oxide nanoparticles doped with magnesium(II)

International Nuclear Information System (INIS)

Lu, Xianyong; Liu, Zhaoyue; Zhu, Ying; Jiang, Lei

2011-01-01

Highlights: → Mg-doped ZnO nanoparticles were synthesized by sonochemical strategy. → Mg-doped ZnO nanoparticles present good photocatalytic properties. → The change of band gap contributes to their high efficiency in photocatalyst. -- Abstract: Mg-doped ZnO nanoparticles were successfully synthesized by sonochemical method. The products were characterized by scan electron microscopy (SEM) and X-ray powder diffraction (XRD). SEM images revealed that ZnO doped with Mg(II) nanoparticles and ZnO nanoparticles synthesized by the same strategy all had spherical topography. XRD patterns showed that the doped nanoparticles had the same crystals structures as the pure ZnO nanoparticles. The Mg-doped ZnO nanoparticles had larger lattice volume than the un-doped nanoparticles. X-ray photoelectron spectroscopy (XPS) not only demonstrated the moral ratio of Mg and Zn element on the surface of nanoparticles, but their valence in nanoparticles as well. The Mg-doped ZnO nanoparticles presented good properties in photocatalyst compared with pure ZnO nanoparticles.

Mg doping induced high structural quality of sol–gel ZnO nanocrystals: Application in photocatalysis

Energy Technology Data Exchange (ETDEWEB)

Abed, Chayma; Bouzidi, Chaker [Laboratoire de Physico-chimie des Matériaux Minéraux et leurs Applications, Centre National de Recherches en Sciences des Matériaux, BP 95, Hammam-Lif 2050 (Tunisia); 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, BP 95, Hammam-Lif 2050 (Tunisia); Département de Physique, Faculté des Sciences de Tunis, Université Tunis El Manar, Tunis 2092 (Tunisia); Gelloz, Bernard [Graduate School of Engineering, Nagoya University, 2-24-16 Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603 (Japan); Ferid, Mokhtar [Laboratoire de Physico-chimie des Matériaux Minéraux et leurs Applications, Centre National de Recherches en Sciences des Matériaux, BP 95, Hammam-Lif 2050 (Tunisia)

2015-09-15

Highlights: • ZnO nancrystals doped with Mg were prepared from sol–gel method. • Structural and optical properties of ZnO:Mg nanocrystals were investigated. • Good crystalline quality of ZnO nanocrystals was reported after Mg doping. • Good photocatalytic activity of Mg doped ZnO nanocrystals was demonstrated under sun light illumination. - Abstract: Undoped and Mg doped ZnO nanocrystals (NCs) ZnO:x%Mg (x = 1, 2, 3, and 5) were synthesized using sol–gel method. The structural and optical properties were investigated by X-ray diffraction (XRD), Raman spectroscopy, diffuse reflectivity, and photoluminescence (PL). XRD analysis demonstrates that all prepared samples present pure hexagonal wurtzite structure without any Mg related phases. The NCs size varies from 26.82 nm to 42.96 nm with Mg concentrations; it presents an optimal value for 2% of Mg. The Raman spectra are dominated by the E{sub 2high} mode. For highly Mg doping (5%), the occurrence of silent B{sub 1(low)} mode suggested that the Mg ions do substitute at Zn sites in the ZnO lattice The band gap energy was estimated from both Tauc and Urbach methods and found to be 3.39 eV for ZnO:2%Mg. The PL spectra exhibit two emission bands in the UV and visible range. Their evolution with Mg doping reveals the reduction of defect density in ZnO at low Mg doping by filling Zn vacancies. In addition, it was found that further Mg doping, above 2%, improves the photocatalytic activity of ZnO NCs for photodegradation of Rhodamine B (RhB) under sunlight irradiation. The efficient electron–hole separation is the main factor responsible for the enhancement of photocatalytic performance of Mg doped ZnO NCs. Through this work, we show that by varying the Mg contents in ZnO, this material can be a potential candidate for both optoelectronic and photocatalytic applications.

Ultraviolet Sensing by Al-doped ZnO Thin Films

International Nuclear Information System (INIS)

Rashid, A.R.A.; Menon, P.S.; Shaari, S.

2011-01-01

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

Enhanced photovoltaic performance of ZnO nanorod-based dye-sensitized solar cells by using Ga doped ZnO seed layer

Energy Technology Data Exchange (ETDEWEB)

Dou, Yuanyao [State Key Laboratory of Mechanical Transmission, Chongqing University, Chongqing 400044 (China); Department of Applied Physics, College of Physics, Chongqing University, Chongqing 401331 (China); Wu, Fang, E-mail: fang01234@163.com [State Key Laboratory of Mechanical Transmission, Chongqing University, Chongqing 400044 (China); Department of Applied Physics, College of Physics, Chongqing University, Chongqing 401331 (China); Mao, Caiying [Department of Applied Physics, College of Physics, Chongqing University, Chongqing 401331 (China); Fang, Liang, E-mail: lfang@cqu.edu.cn [State Key Laboratory of Mechanical Transmission, Chongqing University, Chongqing 400044 (China); Department of Applied Physics, College of Physics, Chongqing University, Chongqing 401331 (China); Guo, Shengchun [Department of Applied Physics, College of Physics, Chongqing University, Chongqing 401331 (China); Zhou, Miao [State Key Laboratory of Mechanical Transmission, Chongqing University, Chongqing 400044 (China)

2015-06-05

Highlights: • ZnO nanorods were grown on Ga-doped ZnO seed layers using hydrothermal method. • Using the ZnO nanorods as photoanodes for fabricated dye-sensitized solar cells. • The highest η of 1.23% can be achieved in a DSSC with 3 at.% Ga-doped in seeds. • The effects of ZnO seed layers on electron transport properties were investigated. • The enhancement performance of DSSCs contributed to higher dye loading and η{sub cc}. - Abstract: Zinc oxide (ZnO) nanorod arrays were grown on FTO substrates with a Ga-doped ZnO (GZO) seed layer by a hydrothermal method. GZO seed layers were obtained via sol–gel technology with Ga concentration in the range of 0–4 at.%. The dye sensitized solar cells (DSSCs) using ZnO nanorod arrays as the photoanode layers were prepared. The effect of Ga dopant concentrations in ZnO seed layer on the morphology features of ZnO nanorod arrays and the performance of DSSCs were systematically investigated. Results indicate that the average diameter and density of ZnO nanorod arrays decrease with increasing Ga concentration, but their length shows an opposite trend. The photocurrent density–voltage (J–V) characteristics reveal that the DSSCs with GZO seed layer exhibit significantly improved photovoltaic performance. In particular, the highest energy conversion efficiency (η) of 1.23% can be achieved in a DSSC with 3 at.% Ga doping, which is increased by 86.36% compared with that of the undoped DSSC. The external quantum efficiency (EQE) spectra and electrochemical impedance spectroscopy (EIS) were employed to explore the photon-to-electron conversion process in DSSCs. It is demonstrated that the performance enhancement of DSSCs based on GZO seed layer can be attributed to higher amount of dye loading, more efficient electron transportation and better electrons collection efficiency.

Thermal process induced change of conductivity in As-doped ZnO

Science.gov (United States)

Su, S. C.; Fan, J. C.; Ling, C. C.

2012-02-01

Arsenic-doped ZnO films were fabricated by radio frequency magnetron sputtering method with different substrate temperature TS. Growing with the low substrate temperature of TS=200°C yielded n-type semi-insulating sample. Increasing the substrate temperature would yield p-type ZnO film and reproducible p-type film could be produced at TS~450°C. Post-growth annealing of the n-type As-doped ZnO sample grown at the low substrate temperature (TS=200°C) in air at 500°C also converted the film to p-type conductivity. Further increasing the post-growth annealing temperature would convert the p-type sample back to n-type. With the results obtained from the studies of positron annihilation spectroscopy (PAS), photoluminescence (PL), cathodoluminescence (CL), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectroscopy (SIMS) and nuclear reaction analysis (NRA), we have proposed mechanisms to explain for the thermal process induced conduction type conversion as observed in the As-doped ZnO films.

Optoelectronic properties of doped hydrothermal ZnO thin films

KAUST Repository

Mughal, Asad J.

2017-03-10

Group III impurity doped ZnO thin films were deposited on MgAl2O3 substrates using a simple low temperature two-step deposition method involving atomic layer deposition and hydrothermal epitaxy. Films with varying concentrations of either Al, Ga, or In were evaluated for their optoelectronic properties. Inductively coupled plasma atomic emission spectroscopy was used to determine the concentration of dopants within the ZnO films. While Al and Ga-doped films showed linear incorporation rates with the addition of precursors salts in the hydrothermal growth solution, In-doped films were shown to saturate at relatively low concentrations. It was found that Ga-doped films showed the best performance in terms of electrical resistivity and optical absorbance when compared to those doped with In or Al, with a resistivity as low as 1.9 mΩ cm and an optical absorption coefficient of 441 cm−1 at 450 nm.

ZnO doped SnO2 nanoparticles heterojunction photo-catalyst for environmental remediation

International Nuclear Information System (INIS)

Lamba, Randeep; Umar, Ahmad; Mehta, S.K.; Kansal, Sushil Kumar

2015-01-01

ZnO doped SnO 2 nanoparticles were synthesized by facile and simple hydrothermal technique and used as an effective photocatalyst for the photocatalytic degradation of harmful and toxic organic dye. The prepared nanoparticles were characterized in detail using different techniques for morphological, structural and optical properties. The characterization results revealed that the synthesized nanoparticles possess both crystal phases of tetragonal rutile phase of pure SnO 2 and wurtzite hexagonal phase of ZnO. In addition, the nanoparticles were synthesized in very high quantity with good crystallinity. The photocatalytic activity of prepared nanoparticles was evaluated by the photocatalytic degradation of methylene blue (MB) dye. Detailed photocatalytic experiments based on the effects of irradiation time, catalyst dose and pH were performed and presented in this paper. The detailed photocatalytic experiments revealed that the synthesized ZnO doped SnO 2 nanoparticles heterojunction photocatalyst exhibit best photocatalytic performance when the catalyst dose was 0.25 g/L and pH = 10. ZnO doped SnO 2 nanoparticles heterojunction photocatalyst was also compared with commercially available TiO 2 (PC-50), TiO 2 (PC-500) and SnO 2 and interestingly ZnO doped SnO 2 nanoparticles exhibited superior photocatalytic performance. The presented work demonstrates that the prepared ZnO doped SnO 2 nanoparticles are promising material for the photocatalytic degradation of organic dyes and toxic chemicals. - Highlights: • Synthesis of well-crystalline ZnO-doped SnO 2 nanoparticles. • Excellent morphological, crystalline and photoluminescent properties. • Efficient environmental remediation using ZnO-doped SnO 2 nanoparticles.

Characteristics of strontium-doped ZnO films on love wave filter applications

International Nuclear Information System (INIS)

Water, Walter; Yan, Y.-S.

2007-01-01

The effect of dopant concentrations in strontium-doped ZnO films on Love wave filter characteristics was investigated. Strontium-doped ZnO films with a c-axis preferred orientation were grown on ST-cut quartz by radio frequency magnetron sputtering. The crystalline structures and surface morphology of films were studied by X-ray diffraction, scanning electron microscopy and atomic force microscopy. The electromechanical coupling coefficient, dielectric constant, and temperature coefficient of frequency of filters were then determined using a network analyzer. A uniform crystalline structure and smooth surface of the ZnO films were obtained at the 1-2 mol% strontium dopant level. The electromechanical coupling coefficient of the 1 mol% strontium-doped ZnO film reaches a maximum of 0.61%, and the temperature coefficient of frequency declines to + 12.87 ppm/deg. C at a 1.5 mol% strontium dopant level

Ferromagnetism in doped or undoped spintronics nanomaterials

Science.gov (United States)

Qiang, You

2010-10-01

Much interest has been sparked by the discovery of ferromagnetism in a range of oxide doped and undoped semiconductors. The development of ferromagnetic oxide semiconductor materials with giant magnetoresistance (GMR) offers many advantages in spintronics devices for future miniaturization of computers. Among them, TM-doped ZnO is an extensively studied n-type wide-band-gap (3.36 eV) semiconductor with a tremendous interest as future mini-computer, blue light emitting, and solar cells. In this talk, Co-doped ZnO and Co-doped Cu2O semiconductor nanoclusters are successfully synthesized by a third generation sputtering-gas-aggregation cluster technique. The Co-doped nanoclusters are ferromagnetic with Curie temperature above room temperature. Both of Co-doped nanoclusters show positive magnetoresistance (PMR) at low temperature, but the amplitude of the PMRs shows an anomalous difference. For similar Co doping concentration at 5 K, PMR is greater than 800% for Co-doped ZnO but only 5% for Co-doped Cu2O nanoclusters. Giant PMR in Co-doped ZnO which is attributed to large Zeeman splitting effect has a linear dependence on applied magnetic field with very high sensitivity, which makes it convenient for the future spintronics applications. The small PMR in Co-doped Cu2O is related to its vanishing density of states at Fermi level. Undoped Zn/ZnO core-shell nanoparticle gives high ferromagnetic properties above room temperature due to the defect induced magnetization at the interface.

Influence Al doped ZnO nanostructure on structural and optical properties

International Nuclear Information System (INIS)

Ramelan, Ari Handono; Wahyuningsih, Sayekti; Chasanah, Uswatul; Munawaroh, Hanik

2016-01-01

The preparation of Al-doped ZnO (AZO) thin films prepared by the spin-coating method was reported. Preparation of AZO was conducted by annealing treatment at a temperature of 700°C. While the spin-coating process of AZO thin films were done at 2000 and 3000 rpm respectively. The structural properties of ZnO were determined by X- ray diffraction (XRD) analysis. ZnOnanostructure was formed after annealed at atemperature of 400°C.The morphology of ZnO was determined by Scanning Electron Microscopy (SEM) showed the irregular morphology about 30-50µm in size. Al doped on ZnO influenced the optical properties of those material. Increasing Al contain on ZnO cause of shifting to the lower wavelength. The optical properties of the ZnO as well as AZO films showed that higher reflectance on the ultraviolet region so those materials were used as anti-reflecting agent.Al addition significantly enhance the optical transparency and induce the blue-shift in optical bandgap of ZnO films.

Synthesis characterization and sintering of cobalt-doped lanthanum chromite powders for use in SOFCs

International Nuclear Information System (INIS)

Yamagata, Chieko; Mello-Castanho, Sonia R.H.

2009-01-01

Doped lanthanum chromite is a promising as interconnect material because of its good conductivity at high temperatures and its stability in oxidizing and reducing atmospheres. Perovskite oxide powders of Co-doped lanthanum chromite were synthesized by dispersing precursor metal salt solutions in a polymer matrix followed by a thermal treatment. XRD patterns showed that a highly crystalline cobalt-doped lanthanum chromite was obtained. Fine perovskite powder with a surface area of 6.15 m 2 g -1 calcined at 700 deg C for 1 h, were obtained. After the sample sintered at 1450 deg C for 3h, the powder reached high densities exceeding 97% of the theoretical density. The proposed here has proved to be a very promising technique for the synthesis of lanthanum chromite powders. (author)

Magnetism in V-/Mn-doped ZnO layers fabricated on sapphire

Energy Technology Data Exchange (ETDEWEB)

Mofor, A.C.; El-Shaer, A.; Schlenker, E.; Bakin, A.; Waag, A. [Technical University Braunschweig, Institute of Semiconductor Technology, Braunschweig (Germany); Reuss, F.; Kling, R.; Schoch, W.; Limmer, W. [University Ulm, Department of Semiconductor Physics, Ulm (Germany); Ahlers, H.; Siegner, U.; Sievers, S.; Albrecht, M. [Physikalisch-Technische Bundesanstalt (PTB), Braunschweig (Germany); Eisenmenger, J.; Mueller, T.; Ziemann, P. [University Ulm, Department of Solid State Physics, Ulm (Germany); Huebel, A.; Denninger, G. [Universitaet Stuttgart, 2. Physkalisches Institut, Stuttgart (Germany)

2007-07-15

Doping ZnO with transition metals (TM) is an obvious approach to produce diluted magnetic semiconductors for magnetoelectronic and spintronic applications. We have carried out experimental studies on the fabrication and characterisation of Mn-doped ZnO layers and V-doped ZnO layers and nanorods, the results of which are reviewed in this paper. From SQUID measurements, both epitaxial and implanted ZnMnO layers show paramagnetic behaviour. Epitaxial ZnVO layers show ferromagnetic SQUID signals, but the presence of any secondary phases in the ZnVO layers may not be ruled out. We also show that the used Al{sub 2}O{sub 3} substrates produce a ferromagnetic SQUID signal, that complicates the analysis of magnetisation data and hence the confirmation of ferromagnetism only from SQUID results. (orig.)

Trivalent dopants on ZnO semiconductor obtained by mechanical milling

Energy Technology Data Exchange (ETDEWEB)

Damonte, L.C., E-mail: damonte@fisica.unlp.edu.a [Dto. De Fisica, UNLP, IFLP-CONICET, C.C.67 (1900) La Plata (Argentina); Dto. De Fisica Aplicada, Universidad Politecnica de Valencia, Valencia (Spain); Donderis, V. [Dto. De Ingenieria Electrica, Universidad Politecnica de Valencia, Cami de Vera s/n, 46071 Valencia (Spain); Hernandez-Fenollosa, M.A. [Dto. De Fisica Aplicada, Universidad Politecnica de Valencia, Valencia (Spain)

2009-08-26

Al-doped ZnO powders were obtained by mechanical milling. This n-type oxide material is of interest for application in electronic devices as solar cells. The incorporation of the metal dopant into the ZnO wurtzite structure has been verified by X-ray diffraction, positron annihilation spectroscopy and optical analysis. The optical reflection measurements were strongly affected by the Al incorporation. The positron annihilation spectroscopy constituted an adequate probe to sense the cation substitution in the doped semiconductor.

Trivalent dopants on ZnO semiconductor obtained by mechanical milling

International Nuclear Information System (INIS)

Damonte, L.C.; Donderis, V.; Hernandez-Fenollosa, M.A.

2009-01-01

Al-doped ZnO powders were obtained by mechanical milling. This n-type oxide material is of interest for application in electronic devices as solar cells. The incorporation of the metal dopant into the ZnO wurtzite structure has been verified by X-ray diffraction, positron annihilation spectroscopy and optical analysis. The optical reflection measurements were strongly affected by the Al incorporation. The positron annihilation spectroscopy constituted an adequate probe to sense the cation substitution in the doped semiconductor.

Structural and optical properties of Na-doped ZnO films

Science.gov (United States)

Akcan, D.; Gungor, A.; Arda, L.

2018-06-01

Zn1-xNaxO (x = 0.0-0.05) solutions have been synthesized by the sol-gel technique using Zinc acetate dihydrate and Sodium acetate which were dissolved into solvent and chelating agent. Na-doped ZnO nanoparticles were obtained from solutions to find phase and crystal structure. Na-doped ZnO films have been deposited onto glass substrate by using sol-gel dip coating system. The effects of dopant concentration on the structure, morphology, and optical properties of Na-doped ZnO thin films deposited on glass substrate are investigated. Characterization of Zn1-xNaxO nanoparticles and thin films are examined using differential thermal analysis (DTA)/thermogravimetric analysis (TGA), Scanning electron microscope (SEM) and X-Ray diffractometer (XRD). Optical properties of Zn1-xNaxO thin films were obtained by using PG Instruments UV-Vis-NIR spectrophotometer in 190-1100 nm range. The structure, morphology, and optical properties of thin films are presented.

Magnetic Properties of Gadolinium-Doped ZnO Films and Nanostructures

KAUST Repository

Roqan, Iman S.

2016-08-29

The magnetic properties of Gd-doped ZnO films and nanostructures are important to the development of next-generation spintronic devices. Here, we elucidate the significant role played by Gd-oxygen-deficiency defects in mediating/inducing ferromagnetic coupling in in situ Gd-doped ZnO thin films deposited at low oxygen pressure by pulsed laser deposition (PLD). Samples deposited at higher oxygen pressures exhibited diamagnetic responses. Vacuum annealing was used on these diamagnetic samples (grown at a relatively high oxygen pressures) to create oxygen- deficiency defects with the aim of demonstrating reproducibility of room-temperature ferromagnetism (RTFM). Samples annealed at oxygen environment exhibited super‐ paramagnetism and blocking-temperature effects. The samples possessed secondary phases; Gd segregation led to superparamagnetism. Theoretical studies showed a shift of the 4f level of Gd to the conduction band minimum (CBM) in Gd-doped ZnO nanowires, which led to an overlap with the Fermi level, resulting in strong exchange coupling and consequently RTFM.

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.

Effect of Ga doping and point defect on magnetism of ZnO

Energy Technology Data Exchange (ETDEWEB)

Hou, Qingyu [College of Science, Inner Mongolia University of Technology, 010051 Hohhot (China); Zhao, Chunwang, E-mail: cwzhao@shmtu.edu.cn [College of Arts and Sciences, Shanghai Maritime University, 201306 Shanghai (China); Jia, Xiaofang; Qu, Lingfeng [College of Science, Inner Mongolia University of Technology, 010051 Hohhot (China)

2017-02-01

The combined influence mechanism of Ga doping and Zn vacancy or O vacancy on magnetism of ZnO is studied using the first-principle calculation. The coexistence of Ga doping and Zn vacancy can achieve a Curie temperature higher than room temperature and the Ga doped ZnO system is a p-type diluted degenerate semiconductor with metalized ferromagnetism. The magnetism of the doping system of Ga doping and Zn vacancy is mainly contributed by double-exchange interaction through the holes of Zn vacancy taking carrier as medium. However, the system of Ga doping and O vacancy is non-magnetic. In the coexistence of Ga doping and Zn vacancy or O vacancy, a close relative distance between doping and vacancy will reduce the formation energy of the doping system but increase the easiness of doping and vacancy, as well as enhance the stability of the doping system.

Transport and structural characterization of solution-processable doped ZnO nanowires

KAUST Repository

Noriega, Rodrigo

2009-08-18

The use of ZnO nanowires has become a widespread topic of interest in optoelectronics. In order to correctly assess the quality, functionality, and possible applications of such nanostructures it is important to accurately understand their electrical and optical properties. Aluminum- and gallium-doped crystalline ZnO nanowires were synthesized using a low-temperature solution-based process, achieving dopant densities of the order of 1020 cm-3. A non-contact optical technique, photothermal deflection spectroscopy, is used to characterize ensembles of ZnO nanowires. By modeling the free charge carrier absorption as a Drude metal, we are able to calculate the free carrier density and mobility. Determining the location of the dopant atoms in the ZnO lattice is important to determine the doping mechanisms of the ZnO nanowires. Solid-state NMR is used to distinguish between coordination environments of the dopant atoms.

Surfactant-assisted carbon doping in ZnO nanowires using Poly Ethylene Glycol (PEG)

Energy Technology Data Exchange (ETDEWEB)

Amanullah, Malik; Javed, Qurat-ul-Ain, E-mail: Quratulain@sns.nust.edu.pk; Rizwan, Syed

2016-09-01

Zinc Oxide (ZnO) provides unique properties owing to its wide bandgap, large resistivity range and possibility to tune the physical properties. The surfactant assisted carbon doping was made possible due to the lowering of surface energy. The ZnO and carbon doped ZnO (C-ZnO) nanowires fabricated by hydrothermal process, Poly Ethylene Glycol (PEG) is used as surfactant in hydrothermal synthesis followed by post growth annealing treatment at 600 °C–700 °C. At 5%–10% of diluted PEG carbon is doped in ZnO. The crystallinity, structural morphology and elemental composition analysis for ZnO and C-ZnO nanowires were carried out using X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy techniques respectively. Carbon doping in ZnO nanowires in the presence of different percentage of surfactant is explained by calculating the change in surface energy with respect to change in PEG molecule concentration. It was found that the surface energy per molecule modulates from 3.92 × 10{sup −8} J/m{sup 2} to 8.16 × 10{sup −7} J/m{sup 2} in the PEG concentration range between 5% and 10%. Our results provides a new theoretical calculations, implemented on real system, to observe the details of PEG-assisted Carbon doping in II-VI semiconductor nanowires. - Highlights: • ZnO and C-ZnO was synthesized by PEG assisted post growth annealing process. • At 5% and 10% of PEG successful synthesis of C-ZnO was found. • XRD, SEM and EDX characterizations confirm the successful synthesis of ZnO and C-ZnO. • Change in surface energy with respect to PEG molecule concentration was calculated.

Sustainable synthesis of metals-doped ZnO nanoparticles from zinc-bearing dust for photodegradation of phenol

International Nuclear Information System (INIS)

Wu, Zhao-Jin; Huang, Wei; Cui, Ke-Ke; Gao, Zhi-Fang; Wang, Ping

2014-01-01

Highlights: • Multi-doped ZnO (M-ZnO) was prepared from Zn-bearing dust for waste-cleaning-waste. • All the dopants M (Fe, Mg, Ca and Al) and Zn are recovered from the dust. • Doping by the dust-derived M expands excitability of ZnO to visible light region. • M-ZnO has good catalytic activity in the degradation of phenol under visible light. - Abstract: A novel strategy of waste-cleaning-waste is proposed in the present work. A metals-doped ZnO (M-ZnO, M = Fe, Mg, Ca and Al) nanomaterial has been prepared from a metallurgical zinc-containing solid waste “fabric filter dust” by combining sulfolysis and co-precipitation processes, and is found to be a favorable photocatalyst for photodegradation of organic substances in wastewater under visible light irradiation. All the zinc and dopants (Fe, Mg, Ca and Al) for preparing M-ZnO are recovered from the fabric filter dust, without any addition of chemical as elemental source. The dust-derived M-ZnO samples deliver single phase indexed as the hexagonal ZnO crystal, with controllable dopants species. The photocatalytic activity of the dust-derived M-ZnO samples is characterized by photodegradation of phenol aqueous solution under visible light irradiation, giving more prominent photocatalytic behaviors than undoped ZnO. Such enhancements may be attributed to incorporation of the dust-derived metal elements (Fe, Mg, Ca and Al) into ZnO structure, which lead to the modification of band gap and refinement of grain size. The results show a feasibility to utilize the industrial waste as a resource of photodegradating organic substances in wastewater treatments

Improving the conductance of ZnO thin film doping with Ti by using a cathodic vacuum arc deposition process

International Nuclear Information System (INIS)

Wu, Chun-Sen; Lin, Bor-Tsuen; Jean, Ming-Der

2011-01-01

The Ti-doped ZnO films compared to un-doped ZnO films were deposited onto Corning XG glass substrates by using a cathodic vacuum arc deposition process in a mixture of oxygen and argon gases. The structural, electrical and optical properties of un-doped and Ti-doped ZnO films have been investigated. When the Ti target power is about 750 W, the incorporation of titanium atoms into zinc oxide films is obviously effective. Additionally, the resistivity of un-doped ZnO films is high and reduces to a value of 3.48 x 10 -3 Ω-cm when Ti is incorporated. The Ti doped in the ZnO films gave rise to the improvement of the conductivity of the films obviously. The Ti-doped ZnO films have > 85% transmittance in a range of 400-700 nm.

Synergistic effects of Mo and F doping on the quality factor of ZnO thin films prepared by a fully automated home-made nebulizer spray technique

Science.gov (United States)

Ravichandran, K.; Dineshbabu, N.; Arun, T.; Manivasaham, A.; Sindhuja, E.

2017-01-01

Transparent conducting oxide films of undoped, Mo doped, Mo + F co-doped ZnO were deposited using a facile homemade nebulizer spray pyrolysis technique. The effects of Mo and F doping on the structural, optical, electrical and surface morphological properties were investigated using XRD, UV-vis-NIR spectroscopy, I-V and Hall probe techniques, FESEM and AFM, and XPS, respectively. The XRD analysis confirms that all the films are well crystallized with hexagonal wurtzite structure. All the synthesized samples exhibit high transmittance (above 85%) in the visible region. The current-voltage (I-V) characteristics show the ohmic conduction nature of the films. The Hall probe measurements show that the synergistic effects of Mo and F doping cause desirable improvements in the quality factor of the ZnO films. A minimum resistivity of 5.12 × 10-3 Ω cm with remarkably higher values of mobility and carrier concentration is achieved for Mo (2 at.%) + F (15 at.%) co-doped ZnO films. A considerable variation in the intensity of deep level emission caused by Mo and F doping is observed in the photoluminescence (PL) studies. The presence of the constituent elements in the samples is confirmed by XPS analysis.

Neutron scintillator using Ga-doped ZnO phosphor with high detection efficiency

International Nuclear Information System (INIS)

Koyama, Shin; Kinoshita, Atsushi; Fujiwara, Akihiko; Kobayashi, Haruki; Takei, Yoshinori; Nanto, Hidehito; Katagiri, Masaki

2009-01-01

Zinc Oxide (ZnO) family phosphors as phosphor for neutron detector have prepared using Spark Plasma Sintering (SPS) method. The optical properties of ZnO phosphor prepared are investigated. The following results were obtained. Two dominant photoluminescence (PL) emission peaks at 395 nm and 495 nm were observed. The lifetime of the PL emission peak at 395 nm (UV emission band) is about 20 ns, which is suitable for neutron detection. The Ga (30 mol%)-doped ZnO phosphor exhibited an intense UV emission band without the visible emission band. The Ga-doped ZnO phosphor can be prepared at the atmospheric pressure of about 8 Pa using SPS method. It was found that the PL intensity of UV emission band is increased with improving the crystallinity of the ZnO phosphor. (author)

The structural, electronic and optical properties of Nd doped ZnO using first-principles calculations

Science.gov (United States)

Wen, Jun-Qing; Zhang, Jian-Min; Chen, Guo-Xiang; Wu, Hua; Yang, Xu

2018-04-01

The density functional theory calculations using general gradient approximation (GGA) applying Perdew-Burke-Ernzerhof (PBE) as correlation functional have been systematically performed to research the formation energy, the electronic structures, band structures, total and partial DOS, and optical properties of Nd doping ZnO with the content from 6.25% to 12.5%. The formation energies are negative for both models, which show that two structures are energetically stable. Nd doping ZnO crystal is found to be a direct band gap semiconductor and Fermi level shifts upward into conduction band, which show the properties of n-type semiconductor. Band structures are more compact after Nd doping ZnO, implying that Nd doping induces the strong interaction between different atoms. Nd doping ZnO crystal presents occupied states at near Fermi level, which mainly comes from the Nd 4f orbital. The calculated optical properties imply that Nd doping causes a red-shift of absorption peaks, and enhances the absorption of the visible light.

Substrate effect on the room-temperature ferromagnetism in un-doped ZnO films

Science.gov (United States)

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

2012-07-01

Room-temperature ferromagnetism was achieved in un-doped ZnO films on silicon and quartz substrates. Photoluminescence measurement and positron annihilation analysis suggested that the ferromagnetism was originated from singly occupied oxygen vacancies (roughly estimated as ˜0.55 μB/vacancy), created in ZnO films by annealing in argon. The saturated magnetization of ZnO films was enhanced from ˜0.44 emu/g (on quartz) to ˜1.18 emu/g (on silicon) after annealing at 600 °C, as silicon acted as oxygen getter and created more oxygen vacancies in ZnO films. This study clarified the origin of ferromagnetism in un-doped ZnO and provides an idea to enhance the ferromagnetism.

Efficiency of Nb-Doped ZnO Nanoparticles Electrode for Dye-Sensitized Solar Cells Application

Science.gov (United States)

Anuntahirunrat, Jirapat; Sung, Youl-Moon; Pooyodying, Pattarapon

2017-09-01

The technological of Dye-sensitized solar cells (DSSCs) had been improved for several years. Due to its simplicity and low cost materials with belonging to the part of thin films solar cells. DSSCs have numerous advantages and benefits among the other types of solar cells. Many of the DSSC devices had use organic chemical that produce by specific method to use as thin film electrodes. The organic chemical that widely use to establish thin film electrodes are Zinc Oxide (ZnO), Titanium Dioxide (TiO2) and many other chemical substances. Zinc oxide (ZnO) nanoparticles had been used in DSSCs applications as thin film electrodes. Nanoparticles are a part of nanomaterials that are defined as a single particles 1-100 nm in diameter. From a few year ZnO widely used in DSSC applications because of its optical, electrical and many others properties. In particular, the unique properties and utility of ZnO structure. However the efficiency of ZnO nanoparticles based solar cells can be improved by doped various foreign impurity to change the structures and properties. Niobium (Nb) had been use as a dopant of metal oxide thin films. Using specification method to doped the ZnO nanoparticles thin film can improved the efficiencies of DSSCs. The efficiencies of Nb-doped ZnO can be compared by doping 0 at wt% to 5 at wt% in ZnO nanoparticles thin films that prepared by the spin coating method. The thin film electrodes doped with 3 at wt% represent a maximum efficiencies with the lowest resistivity of 8.95×10-4 Ω·cm.

Strong compensation hinders the p-type doping of ZnO: a glance over surface defect levels

Science.gov (United States)

Huang, B.

2016-07-01

We propose a surface doping model of ZnO to elucidate the p-type doping and compensations in ZnO nanomaterials. With an N-dopant, the effects of N on the ZnO surface demonstrate a relatively shallow acceptor level in the band gap. As the dimension of the ZnO materials decreases, the quantum confinement effects will increase and render the charge transfer on surface to influence the shifting of Fermi level, by evidence of transition level changes of the N-dopant. We report that this can overwhelm the intrinsic p-type conductivity and transport of the ZnO bulk system. This may provide a possible route of using surface doping to modify the electronic transport and conductivity of ZnO nanomaterials.

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.

Synthesis and Characterization of Molybdenum Doped ZnO Thin Films by SILAR Deposition Method

Science.gov (United States)

Radha, R.; Sakthivelu, A.; Pradhabhan, D.

2016-08-01

Molybdenum (Mo) doped zinc oxide (ZnO) thin films were deposited on the glass substrate by Successive Ionic Layer Adsorption and Reaction (SILAR) deposition method. The effect of Mo dopant concentration of 5, 6.6 and 10 mol% on the structural, morphological, optical and electrical properties of n-type Mo doped ZnO films was studied. The X-ray diffraction (XRD) results confirmed that the Mo doped ZnO thin films were polycrystalline with wurtzite structure. The field emission scanning electron microscopy (FESEM) studies shows that the surface morphology of the films changes with Mo doping. A blue shift of the optical band gap was observed in the optical studies. Effect of Mo dopant concentration on electrical conductivity was studied and it shows comparatively high electrical conductivity at 10 mol% of Mo doping concentration.

Synthesis, microstructural characterization and optical properties of undoped, V and Sc doped ZnO thin films

International Nuclear Information System (INIS)

Amezaga-Madrid, P.; Antunez-Flores, W.; Ledezma-Sillas, J.E.; Murillo-Ramirez, J.G.; Solis-Canto, O.; Vega-Becerra, O.E.; Martinez-Sanchez, R.; Miki-Yoshida, M.

2011-01-01

Research highlights: → Undoped, V and Sc doped ZnO thin films by Aerosol Assisted Chemical Vapour Deposition. → Optimum substrate temperatures of 673 K and 623 K for Sc and V doped films. → Around one third of the dopants in solution were deposited into the films. → Crystallite and grain size decreased with the increase of dopant concentration. → Optical band gap increased from 3.29 to 3.32 eV for undoped to 7 Sc/Zn at. %. - Abstract: Many semiconductor oxides (ZnO, TiO 2 , SnO 2 ) when doped with a low percentage of non-magnetic (V, Sc) or magnetic 3d (Co, Mn, Ni, Fe) cation behave ferromagnetically. They have attracted a great deal of interest due to the integration of semiconducting and magnetic properties in a material. ZnO is one of the most promising materials to carry out these tasks in view of the fact that it is optically transparent and has n or p type conductivity. Here, we report the synthesis, microstructural characterization and optical properties of undoped, V and Sc doped zinc oxide thin films. ZnO based thin films with additions of V and Sc were deposited by the Aerosol Assisted Chemical Vapour Deposition method. V and Sc were incorporated separately in the precursor solution. The films were uniform, transparent and non-light scattering. The microstructure of the films was characterized by Grazing Incidence X-ray Diffraction, Scanning Electron Microscopy, and Scanning Probe Microscopy. Average grain size and surface rms roughness were estimated by the measurement of Atomic Force Microscopy. The microstructure of doped ZnO thin films depended on the type and amount of dopant material incorporated. The optical properties were determined from specular reflectance and transmittance spectra. Results were analyzed to determine the optical constant and band gap of the films. An increase in the optical band gap with the content of Sc dopant was obtained.

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

A highly selective and wide range ammonia sensor—Nanostructured ZnO:Co thin film

International Nuclear Information System (INIS)

Mani, Ganesh Kumar; Rayappan, John Bosco Balaguru

2015-01-01

Graphical abstract: - Highlights: • Cobalt doped nanostructured ZnO thin films were spray deposited on glass substrates. • Co-doped ZnO film was highly selective towards ammonia than ethanol, methanol, etc. • The range of ammonia detection was improved significantly by doping cobalt in ZnO. - Abstract: Ammonia sensing characteristics of undoped and cobalt (Co)-doped nanostructured ZnO thin films were investigated. Polycrystalline nature with hexagonal wurtzite structure and high crystalline quality with dominant (0 0 2) plane orientation of Co-doped ZnO film were confirmed by the X-ray diffractogram. Scanning electron micrographs of the undoped film demonstrated the uniform deposition of sphere-shaped grains. But, smaller particles with no clear grain boundaries were observed for Co-doped ZnO thin film. Band gap values were found to be 3.26 eV and 3.22 eV for undoped and Co-doped ZnO thin films. Ammonia sensing characteristics of Co-doped ZnO film at room temperature were investigated in the concentration range of 15–1000 ppm. Variation in the sensing performances of Co-doped and pure ZnO thin films has been analyzed and compared

Boron doped nanostructure ZnO films deposited by ultrasonic spray pyrolysis

Energy Technology Data Exchange (ETDEWEB)

Karakaya, Seniye, E-mail: seniyek@ogu.edu.tr; Ozbas, Omer

2015-02-15

Highlights: • Nanostructure undoped and boron doped ZnO films were deposited by USP technique. • Influences of doping on the surface and optical properties of the ZnO films were investigated. • XRD spectra of the films exhibited a variation in crystalline quality depending on the B content. - Abstract: ZnO is an II–VI compound semiconductor with a wide direct band gap of 3.3 eV at room temperature. Doped with group III elements (B, Al or Ga), it becomes an attractive candidate to replace tin oxide (SnO{sub 2}) or indium tin oxide (ITO) as transparent conducting electrodes in solar cell devices and flat panel display due to competitive electrical and optical properties. In this work, ZnO and boron doped ZnO (ZnO:B) films have been deposited onto glass substrates at 350 ± 5 °C by a cost-efficient ultrasonic spray pyrolysis technique. The optical, structural, morphological and electrical properties of nanostructure undoped and ZnO:B films have been investigated. Electrical resistivity of films has been analyzed by four-probe technique. Optical properties and thicknesses of the films have been examined in the wavelength range 1200–1600 nm by using spectroscopic ellipsometry (SE) measurements. The optical constants (refractive index (n) and extinction coefficient (k)) and the thicknesses of the films have been fitted according to Cauchy model. The optical method has been used to determine the band gap value of the films. Transmission spectra have been taken by UV spectrophotometer. It is found that both ZnO and ZnO:B films have high average optical transmission (≥80%). X-ray diffraction (XRD) patterns indicate that the obtained ZnO has a hexagonal wurtzite type structure. The morphological properties of the films were studied by atomic force microscopy (AFM). The surface morphology of the nanostructure films is found to depend on the concentration of B. As a result, ZnO:B films are promising contender for their potential use as transparent window layer and

Annealed Ce{sup 3+}-doped ZnO flower-like morphology synthesized by chemical bath deposition method

Energy Technology Data Exchange (ETDEWEB)

Koao, Lehlohonolo F., E-mail: koaolf@ufs.ac.za [Department of Physics, University of the Free State (Qwa Qwa campus), Private Bag X13, Phuthaditjhaba 9866 (South Africa); Dejene, Francis B.; Tsega, Moges [Department of Physics, University of the Free State (Qwa Qwa campus), Private Bag X13, Phuthaditjhaba 9866 (South Africa); Swart, Hendrik C. [Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein 9300 (South Africa)

2016-01-01

We have successfully synthesized ZnO:xmol% Ce{sup 3+} (0≤x≤10 mol%) doped nanopowders via the chemical bath deposition method (CBD) technique at low temperature (80 °C) and annealed in air at 700 °C. The X-ray diffraction patterns showed that all the undoped and Ce-doped ZnO nanopowders have a hexagonal wurtzite polycrystalline structure with an average crystallite size of about 46 nm. Weak diffraction peaks related mainly to cerium oxide were also detected at higher concentrations of Ce{sup 3+} (x=5–10 mol%). The scanning electron microscopy study revealed that the nanopowder samples were assembled in flower-shaped undoped ZnO and pyramid-shaped Ce{sup 3+}-doped ZnO nanostructures. The UV–vis spectra showed that the absorption edges shifted slightly to the longer wavelengths with the increase in the Ce{sup 3+} ions concentration. Moreover, the photoluminescence (PL) results showed a relative weak visible emission for the Ce{sup 3+}-doped ZnO nanoparticles compared to the undoped ZnO. The effects of Ce{sup 3+}-doping on the structure and PL of ZnO nanopowders are discussed in detail.

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

Energy Technology Data Exchange (ETDEWEB)

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

2012-10-01

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

Thermoelectric properties of In{sub 0.2}Co{sub 4}Sb{sub 12} skutterudites with embedded PbTe or ZnO nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Chubilleau, C.; Lenoir, B.; Candolfi, C.; Masschelein, P. [Université de Lorraine, CNRS, UMR 7198, Institut Jean Lamour, Parc de Saurupt, 54011 Nancy (France); Dauscher, A., E-mail: anne.dauscher@univ-lorraine.fr [Université de Lorraine, CNRS, UMR 7198, Institut Jean Lamour, Parc de Saurupt, 54011 Nancy (France); Guilmeau, E. [Laboratoire CRISMAT, UMR 6508, 6 boulevard Maréchal Juin, 14050 Caen Cedex (France); Godart, C. [ICMPE-CMTR, CNRS-UMR 7182, 2-8 rue H. Dunant, 94320 Thiais (France)

2014-03-15

Highlights: • Fabrication of nanostructured skutterudites ZnO or PbTe/In{sub 0.2}Co{sub 4}Sb{sub 12.} • Thermal conductivity modeling accounts for experimental results. • Greater lattice thermal conductivity decrease in In{sub 0.2}Co{sub 4}Sb{sub 12} than in CoSb{sub 3}. • A max ZT of 1.05 is obtained at 700 K in a 2 wt% ZnO-containing sample. -- Abstract: Transport properties of the skutterudite compound In{sub 0.2}Co{sub 4}Sb{sub 12} containing ZnO or PbTe nano-sized particles (2–12 wt%) were investigated by means of electrical resistivity, thermopower and thermal conductivity between 5 and 800 K. The composite powders were prepared by freeze-drying the nanoparticles with micron-sized In{sub 0.2}Co{sub 4}Sb{sub 12} powders. Densification was achieved by spark plasma sintering. All composites were characterized by X-ray powder diffraction and scanning electron microscopy. All the transport coefficients show similar temperature dependences suggesting little influence of the nature, semiconducting or insulating, of the nanoparticles. Both the electrical and the thermal conductivities decrease with increasing the PbTe or ZnO content. The impact of ZnO and PbTe on the thermal conductivity was modelled based on the Debye model taking into account a relaxation time constant reflecting phonon scattering by spherical nanoparticles. A maximum dimensionless figure of merit ZT of 1.05 at 700 K was achieved in a sample containing 2 wt% ZnO, a value quite similar to that of the reference In{sub 0.2}Co{sub 4}Sb{sub 12} compound.

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.

Direct observation of hopping induced spin polarization current in oxygen deficient Co-doped ZnO by Andreev reflection technique

Energy Technology Data Exchange (ETDEWEB)

Yang, Kung-Shang; Huang, Tzu-Yu; Dwivedi, G.D. [Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan (China); Lin, Lu-Kuei; Lee, Shang-Fan [Taiwan Institute of Physics, Academia Sinica, Taipei, Taiwan (China); Sun, Shih-Jye [Department of Applied Physics, National Kaohsiung University, Kaohsiung, Taiwan (China); Chou, Hsiung, E-mail: hchou@mail.nsysu.edu.tw [Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan (China)

2017-07-01

Highlights: • Co-doped ZnO thin-films were grown with varying V{sub O} concentartion. • PCAR measurements were done to study the SPC. • High spin polarization was observed above a certain V{sub O} concentartion. • High V{sub O} samples provide a high density of completed percolation path. • This complete percolation path gives rise to high SPC. - Abstract: Oxygen vacancy induced ferromagnetic coupling in diluted magnetic oxide (DMO) semiconductors have been reported in several studies, but technologically more crucial spin-polarized current (SPC) is still under-developed in DMOs. Few studies have claimed that VRH mechanism can originate the SPC, but, how VRH mechanism associated with percolation path, is not clearly understood. We used Point-contact Andreev reflection (PCAR) technique to probe the SPC in Co-doped ZnO (CZO) films. Since the high resistance samples cause broadening in conductance(G)-voltage(V) curves, which may result in an unreliable evaluation of spin polarization, we include two extra parameters, (i) effective temperature and (ii) spreading resistance, for the simulation to avoid the uncertainty in extracting spin polarization. The effective G-V curves and higher spin polarization can be obtained above a certain oxygen vacancy concentration. The number of completed and fragmentary percolation paths is proportional to the concentration of oxygen vacancies. For low oxygen vacancy samples, the Pb-tip has a higher probability of covering fragmentary percolation paths than the complete ones, due to its small contact size. The completed paths may remain independent of one another and get polarized in different directions, resulting in lower spin-polarization value. High oxygen vacancy samples provide a high density of completed path, most of them link to one another by crossing over, and gives rise to high spin-polarization value.

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

Investigations on photoelectrochemical performance of boron doped ZnO nanorods synthesized by facile hydrothermal technique

Science.gov (United States)

Sharma, Akash; Chakraborty, Mohua; Thangavel, R.

2018-05-01

Undoped and 10% Boron (B)-doped Zinc Oxide nanorods (ZnO NRs) on Tin doped Indium Oxide (ITO) coated glass substrates were synthesized using facile sol-gel, spin coating and hydrothermal method. The impact of adding Boron on the structural, optical properties, surface morphology and photoelectrochemical (PEC) performances of the ZnO NRs have been investigated. The XRD pattern confirmed the formation of pure hexagonal phase with space group P63mc (186). The same can also be clearly observed form the FESEM images. The UV-Vis study shows the narrowing in band gap from 3.22 eV to 3.19 eV with incorporation of Boron in ZnO matrix. The B-doped ZnO NRs sample shows an enhanced photocurrent density of 1.31 mA/cm2 at 0.5 V (vs. Ag/AgCl), which is more than 171% enhancement compared to bare ZnO NRs (0.483 mA/cm2) in 0.1 M Na2SO4 aqueous solution. The results clearly indicates that the boron doped ZnO NRs can be used as an efficient photoelectrode material for photoelectrochemical cell.

Structural and plasmonic properties of noble metal doped ZnO nanomaterials

Science.gov (United States)

Pathak, Trilok K.; Swart, H. C.; Kroon, R. E.

2018-04-01

Noble metal doped ZnO has been synthesized by the combustion method and the effect of different metals (Ag, Au, Pd) on the structural, morphological, optical, photoluminescence and localized surface plasmon resonance (LSPR) properties has been investigated. X-ray diffraction analysis revealed that the ZnO had a hexagonal wurtzite structure and the crystallite sizes were affected by the doping. The formation of noble metal nanoparticles (NPs) was investigated using transmission electron microscopy and diffuse reflectance spectra. The LSPR of the metallic NPs was predicted using Mie theory calculations. The absorption spectra were calculated using the Kubelka-Munk function and the optical bandgap varied from 3.06 to 3.18 eV for the different doping materials. The experimental results suggest that the origin of enhanced emission was due to direct interaction between the laser photons and the noble material NPs which in turn leads to photoemission transfer of electrons from the noble metals NPs to the conduction band of ZnO.

The electronic, magnetic and optical properties of ZnO doped with doubles impurities (Cr, Fe): An LDA-SIC and Monte Carlo study

Energy Technology Data Exchange (ETDEWEB)

Salmani, El Mehdi, E-mail: elmehdisalmani@gmail.com [LMPHE, Faculté des Sciences, Université Mohammed V, Rabat (Morocco); Laghrissi, Ayoub; Lamouri, Rachida; Ez-Zahraouy, Hamid [LMPHE, Faculté des Sciences, Université Mohammed V, Rabat (Morocco); Benyoussef, Abdelilah [Institute for Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Académie Hassan II des Sciences et Techniques, Rabat (Morocco)

2017-01-15

Electronic structure, magnetic and optical properties of ZnO doped with single and double impurities Zn{sub 1−x}Cr{sub x}O, Zn{sub 1−x}Fe{sub x}O, and Zn{sub 1−2x}Cr{sub x}Fe{sub x}O (x=0.03 and 0.06) are investigated using first-principles calculations. Based on the Korringa–Kohn–Rostoker method combined with the coherent potential approximation, we investigated the half-metallic ferromagnetic behavior of doubles impurities (Cr, Fe) doped ZnO. To support our results, we apply the self-interaction-corrected local density approximation (SIC-LDA) to study the electronic structure, optical and magnetic properties of Co-doped ZnO with doubles impurities (Cr, Fe) showing that the half-metallic ferromagnetic state still persists. The stability of the ferromagnetic state compared with the spin-glass state is investigated by comparing their total energies. The exchange interactions obtained from first principle calculations and used in a classical Ising model by a Monte Carlo approach resulted in ferromagnetic states with high Neel temperature. - Highlights: • The electronic structure calculations for ZnO doped with doubles impurities (Cr, Fe) have been discussed. • The half-metallic aspect was proven to take place for doubles impurities (Cr, Fe) codoped ZnO. • The doubles impurities (Cr, Fe)impurities are shown to introduce the necessary magnetic moment that makes ZnO good candidates for spintronic applications.

Effect of Er3+ doping on structural, morphological and photocatalytical properties of ZnO thin films

Science.gov (United States)

Bouhouche, S.; Bensouici, F.; Toubane, M.; Azizi, A.; Otmani, A.; Chebout, K.; Kezzoula, F.; Tala-Ighil, R.; Bououdina, M.

2018-05-01

In this research work, structure, microstructure, optical and photocatalytic properties of undoped and Erbium doped nanostructured ZnO thin films prepared by sol-gel dip-coating are investigated. X-ray diffraction (XRD) analysis indicates that the deposited films crystallize within the hexagonal wurtzite-type structure with a preferential growth orientation along (002) plane. Morphological observations using scanning electron microscopy (SEM) reveal important influence of Er concentration; displaying homogeneous and dense aspect for undoped to 0.3% then grid-like morphology for 0.4 and 0.5%. UV/vis/NIR transmittance spectroscopy spectra display a transmittance over 70%, and small variation in the energy gap energy 3.263–3.278 eV. Wettability test of ZnO thin films surface ranges from hydrophilic aspect for pure ZnO to hydrophobic one for Er doped ZnO, and the contact angle is found to increase from 58.7° for pure ZnO up to 98.4° for 0.4% Er doped ZnO. The photocatalytic activity measurements evaluated using the degradation of methylene blue (MB) under UV light irradiation demonstrate that undoped ZnO film shows higher photocatalytic activity compared to Er doped ZnO films, which may be attributed to the deterioration of films’crystallinity resulting in lower transmittance.

Mixed Zn and O substitution of Co and Mn in ZnO

CERN Document Server

Pereira, Lino Miguel da Costa; Decoster, Stefan; Correia, João Guilherme; Amorim, Lígia Marina; da Silva, Manuel Ribeiro; Araújo, João Pedro; Vantomme, André

2011-01-01

The physical properties of an impurity atom in a semiconductor are primarily determined by the lattice site it occupies. In general, this occupancy can be correctly predicted based on chemical intuition, but not always. We report on one such exception in the dilute magnetic semiconductors Co- and Mn-doped ZnO, experimentally determining the lattice location of Co and Mn using $\\beta$-emission channeling from the decay of radioactive $^{61}$Co and $^{56}$Mn implanted at the ISOLDE facility at CERN. Surprisingly, in addition to the majority substituting for Zn, we find up to 18% (27%) of the Co (Mn) atoms in O sites, which is virtually unaffected by thermal annealing up to 900 °C. We discuss how this anion site configuration, which had never been considered before for any transition metal in any metal oxide material, may in fact have a low formation energy. This suggests a change in paradigm regarding transition-metal incorporation in ZnO and possibly other oxides and wide-gap semiconductors.

Pure and Sn-doped ZnO films produced by pulsed laser deposition

DEFF Research Database (Denmark)

Holmelund, E.; Schou, Jørgen; Tougaard, S.

2002-01-01

A new technique, metronome doping, has been used for doping of films during pulsed laser deposition (PLD). This technique makes it possible to dope continuously during film growth with different concentrations of a dopant in one deposition sequence. Films of pure and doped ZnO have been produced...

Investigation of structural and optical properties of CaTiO3 powders doped with Mg2+ and Eu3+ ions

International Nuclear Information System (INIS)

Oliveira, Larissa H.; Savioli, Julia; Moura, Ana P. de; Nogueira, Içamira C.; Li, Maximo S.; Longo, Elson; Varela, José A.; Rosa, Ieda L.V.

2015-01-01

In this work, CaTiO 3 powders doped with Mg 2+ ions and CaTiO 3 powders co-doped with Mg 2+ and Eu 3+ ions were prepared by the polymeric precursor method (PPM). These powders were characterized by different characterization techniques to study the influence of Mg 2+ doping as well as Mg 2+ and Eu 3+ co-doping in structural and optical properties of CaTiO 3 perovskite-type structure. The Rietveld refinement and Micro-Raman analyses suggested the substitution Mg 2+ and Eu 3+ ions in the A-site of CaTiO 3 perovskite. The influence of Mg 2+ doping can be detected by the displacement of calcium and oxygen atomic positions when compared to the non-doped CaTiO 3 powder. When Eu 3+ ions are added to the A-site of this perovskite the excess of positive charge can be compensated by the formation of calcium vacancies. Luminescence data showed that Ca 1-x Mg x TiO 3 and Ca 1x Mg x/2 Eu 2y/3 TiO 3 powders are potential materials for fabrication of lighting devices based on near-UV and blue LED using an excitation wavelength of 397 and/or 450 nm. - Highlights: • CaTiO 3 co-doped with Mg 2+ and Eu 3+ were obtained by the Polymeric Precursor Method. • Incorporation of Mg 2+ and Eu 3+ ions in the CaTiO 3 lattice. • Enhancement of the Eu 3+ photoluminescence

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.

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

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.

Synthesis and characterization of Mn-doped ZnO diluted magnetic semiconductors

Energy Technology Data Exchange (ETDEWEB)

Abdel-Galil, A. [Solid State Physics and Accelerators Department, NCRRT, Atomic Energy Authority, Cairo (Egypt); Balboul, M.R., E-mail: m_balboul@yahoo.com [Solid State Physics and Accelerators Department, NCRRT, Atomic Energy Authority, Cairo (Egypt); Sharaf, A. [Radiation Engineering Department, NCRRT, Atomic Energy Authority, Cairo (Egypt)

2015-11-15

In the present work undoped and Mn doped ZnO nanoparticles (ZnO:Mn), diluted magnetic semiconductors, were successfully synthesized by the sol–gel method at room temperature. The morphology of ZnO nanoparticles constituted by flower-like structures with hexagonal morphologies that changed significantly after the incorporation of Mn. Rietveld refinements results showed that Mn ions are successfully doped into ZnO matrix without altering its wurtzite phase. Meanwhile, Raman spectroscopy analyses confirm the wurtzite structure of undoped ZnO and ZnO:Mn nanoparticles. The lattice parameters increase with increasing Mn content due to the large ionic radius of Mn{sup 2+} compared to that of Zn{sup 2+}. Electron spin resonance measurements were performed to gain information about oxidation state and site occupancy of the magnetic Mn ions in the ZnO lattice. Moreover, UV–vis absorption spectra have been utilized to calculate the optical band gap of the undoped ZnO and ZnO:Mn nanoparticles before and after different γ-irradiation doses. The band gap of ZnO:Mn (2%) is 2.62 eV which is noticeably smaller than the 3.26 eV of undoped ZnO. The thermal decomposition properties of the prepared nanoparticle samples were also studied using simultaneous Thermogravimetric analysis in temperature range from 30 to 500 °C.

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.

Sn-doped ZnO nanopetal networks for efficient photocatalytic degradation of dye and gas sensing applications

Energy Technology Data Exchange (ETDEWEB)

Bhatia, Sonik, E-mail: sonikbhatia@gmail.com [Department of Physics, Kanya Maha Vidyalaya, Vidyalaya Marg, Jalandhar, 144004 (India); Verma, Neha [Department of Physics, Kanya Maha Vidyalaya, Vidyalaya Marg, Jalandhar, 144004 (India); Bedi, R.K. [Satyam Institute of Engineering and Technology, Amritsar, 143107, Punjab (India)

2017-06-15

Highlights: • Tin doped ZnO nanoparticles were synthesized by simple combustion method and doctor blade technique. • Different concentrations of Sn (0.5 at. wt%, 1.0 at. wt%, 2.0 at. wt%, 3.0 at. wt%) were used as dopants. • 2.0% of Sn-doped ZnO nanoparticles exhibiting complete photodegradation of DR-31 dye under UV irradiation. Photocatalytic activities for all the samples were observed in 60 min. • The sensing performance showed 5% volume of ethanol and acetone and gases could be detected with sensitivity of 86.80% and 84.40% respectively. - Abstract: Nowadays, tremendous increase in environmental issue is an alarming threat to the ecosystem. This paper reports, rapid synthesis and characterization for tin doped ZnO nanoparticles prepared by simple combustion method and doctor blade technique. The prepared nanoparticles were characterized by several techniques in terms of their morphological, structural, compositional, optical, photocatalytic and gas sensing properties. These detailed characterization confirmed that all the synthesized nanoparticles are well crystalline and having good optoelectronic properties. Herein, different concentrations of Sn (0.5 at. wt%, 1.0 at. wt%, 2.0 at. wt%, 3.0 at. wt%) were used as dopants (SZ1–SZ4). The morphology of synthesized technique confirmed that the petal-shaped nanoparticles has high surface area and are well crystalline. In order to develop smart and functional nano-device, the prepared powder was coated on glass substrate by doctor blade technique and fabricated device was sensed for ethanol and acetone gas at different operating temperatures (300–500{sup °}C). It is noteworthy that morphology of the nanoparticles of the sensitive layer is maintained after different concentration of Sn. High sensitivity is the main cause of high surface area and tin doping. PL intensity near 598 nm of SZ3 is greater than other Sn-doped ZnO which indicates more oxygen vacancies of SZ3 is responsible for enhanced gas

Oxygen vacancy-induced ferromagnetism in un-doped ZnO thin films

Science.gov (United States)

Zhan, Peng; Wang, Weipeng; Liu, Can; Hu, Yang; Li, Zhengcao; Zhang, Zhengjun; Zhang, Peng; Wang, Baoyi; Cao, Xingzhong

2012-02-01

ZnO films became ferromagnetic when defects were introduced by thermal-annealing in flowing argon. This ferromagnetism, as shown by the photoluminescence measurement and positron annihilation analysis, was induced by the singly occupied oxygen vacancy with a saturated magnetization dependent positively on the amount of this vacancy. This study clarified the origin of the ferromagnetism of un-doped ZnO thin films and provides possibly an alternative way to prepare ferromagnetic ZnO films.

A simple photolytic reactor employing Ag-doped ZnO nanowires for water purification

Energy Technology Data Exchange (ETDEWEB)

Udom, Innocent; Zhang, Yangyang [Clean Energy Research Center, College of Engineering, University of South Florida, Tampa, FL 33620 (United States); Ram, Manoj K., E-mail: mkram@usf.edu [Clean Energy Research Center, College of Engineering, University of South Florida, Tampa, FL 33620 (United States); Stefanakos, Elias K. [Clean Energy Research Center, College of Engineering, University of South Florida, Tampa, FL 33620 (United States); Hepp, Aloysius F. [Department of Chemical and Biomedical Engineering, University of South Florida, Tampa, Fl 33620 (United States); Elzein, Radwan; Schlaf, Rudy [Department of Electrical Engineering, University of South Florida, Tampa, Fl 33620 (United States); Goswami, D. Yogi [NASA Glenn Research Center, Research and Technology Directorate, MS 302-1, 21000 Brookpark Road, Cleveland, OH 44135 (United States)

2014-08-01

Well-aligned native zinc oxide (ZnO) and silver-doped ZnO (Ag-ZnO) films were deposited on borosilicate glass via a simple, low-cost, low-temperature, scalable hydrothermal process. The as-synthesized ZnO and Ag-ZnO films were characterized by X-ray diffraction; scanning electron microscopy, UV–visible spectroscopy, and Fourier transform infrared spectroscopy. A simple photolytic reactor was fabricated and later used to find the optimum experimental conditions for photocatalytic performance. The photodegradation of methyl orange in water was investigated using as-prepared ZnO and Ag-ZnO nanowires, and was compared to P25 (a commercial photocatalyst) in both visible and UV radiations. The P25 and Ag-ZnO showed a similar photodegradation performance under UV light, but Ag-ZnO demonstrated superior photocatalytic activity under visible irradiation. The optimized doping of Ag in Ag-ZnO enhanced photocatalytic activity in a simple reactor design and indicated potential applicability of Ag-ZnO for large-scale purification of water under solar irradiation. - Highlights: • Well-aligned zinc oxide (ZnO) and silver-doped ZnO (Ag-ZnO) nanowires were developed. • Simple and effective photolytic reactor was fabricated for water purification. • Ag-ZnO demonstrated superior photocatalytic activity under visible irradiation. • Amount of Ag atoms in Ag-ZnO nanowires is a key to increase photocatalytic activity.

A simple photolytic reactor employing Ag-doped ZnO nanowires for water purification

International Nuclear Information System (INIS)

Udom, Innocent; Zhang, Yangyang; Ram, Manoj K.; Stefanakos, Elias K.; Hepp, Aloysius F.; Elzein, Radwan; Schlaf, Rudy; Goswami, D. Yogi

2014-01-01

Well-aligned native zinc oxide (ZnO) and silver-doped ZnO (Ag-ZnO) films were deposited on borosilicate glass via a simple, low-cost, low-temperature, scalable hydrothermal process. The as-synthesized ZnO and Ag-ZnO films were characterized by X-ray diffraction; scanning electron microscopy, UV–visible spectroscopy, and Fourier transform infrared spectroscopy. A simple photolytic reactor was fabricated and later used to find the optimum experimental conditions for photocatalytic performance. The photodegradation of methyl orange in water was investigated using as-prepared ZnO and Ag-ZnO nanowires, and was compared to P25 (a commercial photocatalyst) in both visible and UV radiations. The P25 and Ag-ZnO showed a similar photodegradation performance under UV light, but Ag-ZnO demonstrated superior photocatalytic activity under visible irradiation. The optimized doping of Ag in Ag-ZnO enhanced photocatalytic activity in a simple reactor design and indicated potential applicability of Ag-ZnO for large-scale purification of water under solar irradiation. - Highlights: • Well-aligned zinc oxide (ZnO) and silver-doped ZnO (Ag-ZnO) nanowires were developed. • Simple and effective photolytic reactor was fabricated for water purification. • Ag-ZnO demonstrated superior photocatalytic activity under visible irradiation. • Amount of Ag atoms in Ag-ZnO nanowires is a key to increase photocatalytic activity

Facile hydrothermal synthesis of mn doped ZnO nanopencils for development of amperometric glucose biosensors

Science.gov (United States)

Shukla, Mayoorika; Pramila; Agrawal, Jitesh; Dixit, Tejendra; Palani, I. A.; Singh, Vipul

2018-05-01

Mn doped ZnO nanopencils were synthesized via low temperature hydrothermal process for fabrication of enzymatic electrochemical glucose biosensor. The KMnO4 was found to play a dual role in modifying morphology and inducing Mn doping. Interestingly, two different types of morphologies viz nanorods and nanopencils along with Mn doping in the later were obtained. Incorporation of Mn has shown a tremendous effect on the morphological variations, repression of defects and electrochemical charge transfer at electrode electrolyte interface. The possible reason behind obtained morphological changes has been proposed which in turn were responsible for the improvement in the different figure of merits of as fabricated enzymatic electrochemical biosensor. There has been a 17 fold enhancement in the sensitivity of the as fabricated glucose biosensor from ZnO nanorods to Mn doped ZnO nanopencils which can be attributed to morphological variation and Mn doping.

Effect of hydrogen doping on the properties of Al and F co-doped ZnO films for thin film silicon solar cell applications

Energy Technology Data Exchange (ETDEWEB)

Wang, Fang-Hsing, E-mail: fansen@dragon.nchu.edu.tw; Yang, Tung-Hsin

2016-04-30

Aluminum and fluorine co-doped zinc oxide (AFZO) thin films were prepared in Ar + H{sub 2} atmospheres by rf magnetron sputtering at room temperature. The structural, electrical, and optical properties of the prepared films were investigated using X-ray diffraction, scanning electron microscopy, atomic force microscopy, Hall-effect measurement, X-ray photoelectron spectroscopy, and ultraviolet–visible spectrometry, and their dependence on deposition atmosphere (i.e. H{sub 2} / (H{sub 2} + Ar) ratio) was studied. The resulting films showed a (0 0 2) diffraction peak, indicating a typical wurtzite structure, and the optimal film crystallinity was obtained with the H{sub 2} / (H{sub 2} + Ar) ratio of 3%. The electrical resistivity of AFZO films decreased to 9.16 × 10{sup −4} Ω-cm, which was lower than ZnO:Al and ZnO:F films due to double doping effect of Al and F. The resistivity further decreased to below 5 × 10{sup −4} Ω-cm for the AFZO film with the H{sub 2} / (H{sub 2} + Ar) ratio of 3%–5%. All the films regardless of hydrogen content displayed high transmittances (> 92%) in the visible wavelength range. Applying the developed AFZO films as front transparent electrodes, amorphous Si thin film solar cells were fabricated and the open-circuit voltage, fill factor, and efficiency of the cell with the hydrogenated AFZO film were improved in contrast to those without the hydrogenated film. - Highlights: • H{sub 2} doping improves optoelectronic properties of Al, F co-doped ZnO (AFZO) films. • Resistivity of AFZO films decreases to 4.4 × 10{sup −4} Ω-cm with the 3% H{sub 2}/(Ar + H{sub 2}) ratio. • AFZO films show high average visible transmittances of above 92%. • Efficiency of a-Si thin film solar cells is improved by AFZO:H as front electrode.

Combined effect of oxygen deficient point defects and Ni doping in radio frequency magnetron sputtering deposited ZnO thin films

Energy Technology Data Exchange (ETDEWEB)

Saha, B., E-mail: biswajit.physics@gmail.com [Thin Film and Nano Science Laboratory, Department of Physics, Jadavpur University, 700 032 Kolkata (India); Department of Physics, National Institute of Technology Agartala, Jirania 799046, Tripura (India); Das, N.S.; Chattopadhyay, K.K. [Thin Film and Nano Science Laboratory, Department of Physics, Jadavpur University, 700 032 Kolkata (India)

2014-07-01

Ni doped ZnO thin films with oxygen deficiency have been synthesized on glass substrates by radio frequency magnetron sputtering technique using argon plasma. The combined effect of point defects generated due to oxygen vacancies and Ni doping on the optical and electrical properties of ZnO thin films has been studied in this work. Ni doping concentrations were varied and the structural, optical and electrical properties of the films were studied as a function of doping concentrations. The films were characterized with X-ray diffractometer, UV–Vis–NIR spectrophotometer, X-ray photoelectron spectroscopy, atomic force microscopy and electrical conductivity measurements. Oxygen deficient point defects (Schottky defects) made the ZnO thin film highly conducting while incorporation of Ni dopant made it more functional regarding their electrical and optical properties. The films were found to have tunable electrical conductivity with Ni doping concentrations. - Highlights: • ZnO thin films prepared by radio frequency magnetron sputtering technique • Synthesis process was stimulated to introduce Schottky-type point defects. • Point defects and external doping of Ni made ZnO thin films more functional. • Point defect induced high electrical conductivity in ZnO thin film. • Significant shift in optical bandgap observed in ZnO with Ni doping concentrations.

Highly doped ZnO films deposited by spray-pyrolysis. Design parameters for optoelectronic applications

Energy Technology Data Exchange (ETDEWEB)

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

2016-04-30

Synthesis and preparation of ZnO films are relevant subjects for obtaining transparent and conducting layers with interesting applications in optoelectronics and photovoltaics. Optimization of parameters such as dopant type and concentration, deposition time and substrate temperature is important for obtaining ZnO layers with optimal properties. In this work we present a study about the induced effects of deposition time on optical and electrical properties of ZnO thin films. These films were deposited by spray pyrolysis of a suitable Zn precursor, obtained through the sol–gel method. The deposition time has direct incidence on internal stress in the crystal structure, generating defects that may affect transparency and electrical transport into the layers. We performed mosaicity measurements, through X-ray diffraction, and used it as a tool to get an insight on structural characteristics and homogeneity of ZnO layers. Also, through this technique, we analyzed thickness and doping effects on crystallinity and carrier transport properties. - Highlights: • Al-doped ZnO films with high conductivity and moderate Hall mobility were obtained. • Mosaicity between crystalline domains increased with film thickness. • Lattice parameters a and c diminished linearly as a function of Al concentration. • First steps for developing porous silicon/doped ZnO heterojunctions were presented.

Highly doped ZnO films deposited by spray-pyrolysis. Design parameters for optoelectronic applications

International Nuclear Information System (INIS)

Garcés, F.A.; Budini, N.; Schmidt, J.A.; Arce, R.D.

2016-01-01

Synthesis and preparation of ZnO films are relevant subjects for obtaining transparent and conducting layers with interesting applications in optoelectronics and photovoltaics. Optimization of parameters such as dopant type and concentration, deposition time and substrate temperature is important for obtaining ZnO layers with optimal properties. In this work we present a study about the induced effects of deposition time on optical and electrical properties of ZnO thin films. These films were deposited by spray pyrolysis of a suitable Zn precursor, obtained through the sol–gel method. The deposition time has direct incidence on internal stress in the crystal structure, generating defects that may affect transparency and electrical transport into the layers. We performed mosaicity measurements, through X-ray diffraction, and used it as a tool to get an insight on structural characteristics and homogeneity of ZnO layers. Also, through this technique, we analyzed thickness and doping effects on crystallinity and carrier transport properties. - Highlights: • Al-doped ZnO films with high conductivity and moderate Hall mobility were obtained. • Mosaicity between crystalline domains increased with film thickness. • Lattice parameters a and c diminished linearly as a function of Al concentration. • First steps for developing porous silicon/doped ZnO heterojunctions were presented.

Enhanced piezoelectric output voltage and Ohmic behavior in Cr-doped ZnO nanorods

International Nuclear Information System (INIS)

Sinha, Nidhi; Ray, Geeta; Godara, Sanjay; Gupta, Manoj K.; Kumar, Binay

2014-01-01

Highlights: • Low cost highly crystalline Cr-doped ZnO nanorods were synthesized. • Enhancement in dielectric, piezoelectric and ferroelectric properties were observed. • A high output voltage was obtained in AFM. • Cr-doping resulted in enhanced conductivity and better Ohmic behavior in ZnO/Ag contact. - Abstract: Highly crystalline Cr-doped ZnO nanorods (NRs) were synthesized by solution technique. The size distribution was analyzed by high resolution tunneling electron microscope (HRTEM) and particle size analyzer. In atomic force microscope (AFM) studies, peak to peak 8 mV output voltage was obtained on the application of constant normal force of 25 nN. It showed high dielectric constant (980) with phase transition at 69 °C. Polarization vs. electric field (P–E) loops with remnant polarization (6.18 μC/cm 2 ) and coercive field (0.96 kV/cm) were obtained. In I–V studies, Cr-doping was found to reduce the rectifying behavior in the Ag/ZnO Schottky contact which is useful for field effect transistor (FET) and solar cell applications. With these excellent properties, Cr-doped ZnO NRs can be used in nanopiezoelectronics, charge storage and ferroelectric applications

Exploration of Al-Doped ZnO in Photovoltaic Thin Films

Science.gov (United States)

Ciccarino, Christopher; Sahiner, M. Alper

The electrical properties of Al doped ZnO-based thin films represent a potential advancement in the push for increasing solar cell efficiency. Doping with Aluminum will theoretically decrease resistivity of the film and therefore achieve this potential as a viable option in the P-N junction phase of photovoltaic cells. The n-type semi-conductive characteristics of the ZnO layer will theoretically be optimized with the addition of Aluminum carriers. In this study, Aluminum doping concentrations ranging from 1-3% by mass were produced, analyzed, and compared. Films were developed onto ITO coated glass using the Pulsed Laser Deposition technique. Target thickness was 250 nm and ellipsometry measurements showed uniformity and accuracy in this regard. Active dopant concentrations were determined using Hall Effect measurements. Efficiency measurements showed possible applications of this doped compound, with upwards of 7% efficiency measured, using a Keithley 2602 SourceMeter set-up. XRD scans showed highly crystalline structures, with effective Al intertwining of the hexagonal wurtzile ZnO molecular structure. This alone indicates a promising future of collaboration between these two materials.

Effect of bismuth doping on the ZnO nanocomposite material and study of its photocatalytic activity under UV-light

International Nuclear Information System (INIS)

Chandraboss, V.L.; Natanapatham, L.; Karthikeyan, B.; Kamalakkannan, J.; Prabha, S.; Senthilvelan, S.

2013-01-01

Graphical abstract: The hetero-junctions that are formed between the ZnO and the Bi provide an internal electric field that facilitates separation of the electron-hole pairs and induces faster carrier migration. Thus they often enhanced photocatalytic reaction. - Highlights: • Bi-doped ZnO nanocomposite material was prepared by precipitation method. • Characterized by XRD, HR-SEM with EDX, UV–visible DRS and FT-RAMAN analysis. • Bi-doped ZnO nanocomposite material was used to photodegradation of Congo red. • Mechanism and photocatalytic effect of nanocomposite material have been discussed. - Abstract: Bismuth (Bi)-doped ZnO nanocomposite material was prepared by precipitation method with doping precursors of bismuth nitrate pentahydrate and oxalic acid, characterized by X-ray diffraction (XRD), High Resolution-Scanning Electron Microscopy (HR-SEM) with Energy Dispersive X-ray (EDX) analysis, UV–visible Diffuse Reflectance Spectroscopy (UV–visible DRS) and Fourier Transform-Raman (FT-RAMAN) analysis. The enhanced photocatalytic activity of the Bi-doped ZnO is demonstrated through photodegradation of Congo red under UV-light irradiation. The mechanism of photocatalytic effect of Bi-doped ZnO nanocomposite material has been discussed

First-principles research on the optical and electrical properties and mechanisms of In-doped ZnO

Science.gov (United States)

Hou, Qingyu; Xi, Dongmin; Li, Wenling; Jia, Xiaofang; Xu, Zhenchao

2018-05-01

The absorption spectra and conductivity of In-doped ZnO still exhibit differences. To resolve this contradiction, the ZnO supercell models with different In doping amounts and the Zn0.9375In0.0625(Zni)0.0625O supercell model were both constructed. When the geometrical structure of all the models was optimized, the GGA + U and GGA used to calculate the energy. In the range of In doping used in this study, the formation energy of In-doped ZnO under Zn-rich conditions is lower than that under O-rich conditions, thereby implying a more stability of In-doped ZnO under Zn-rich than that under O-rich. With the increased In doping content, the volume and the formation energy of the doped system increase, the doped systems become unstable, and doping becomes difficult. Furthermore, the band gaps are narrowed, and the red shift of absorption spectrum is enhanced. In the In doping amount ranging within 0.01389-0.05556, the electron effective mass decreases first and subsequently increases, and the electron concentration increases. The mobility and conductivity also increase first and subsequently decrease. These results are in accordance with the experimental results. The volume of Zn0.9375In0.0625(Zni)0.0625O with the coexistence of In replacing Zn and interstitial Zn is large. The band gap is widened and the absorption spectrum is blue-shifted in the UV region.

The electrical properties of low pressure chemical vapor deposition Ga doped ZnO thin films depending on chemical bonding configuration

Energy Technology Data Exchange (ETDEWEB)

Jung, Hanearl [School of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749 (Korea, Republic of); Kim, Doyoung [School of Electrical and Electronic Engineering, Ulsan College, 57 Daehak-ro, Nam-gu, Ulsan 680-749 (Korea, Republic of); Kim, Hyungjun, E-mail: hyungjun@yonsei.ac.kr [School of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749 (Korea, Republic of)

2014-04-01

Highlights: • Undoped and Ga doped ZnO thin films were deposited using DEZ and TMGa. • Effects of Ga doping using TMGa in Ga doped ZnO were investigated. • Degraded properties from excessive doping were analyzed using chemical bondings. - Abstract: The electrical and chemical properties of low pressure chemical vapor deposition (LP-CVD) Ga doped ZnO (ZnO:Ga) films were systematically investigated using Hall measurement and X-ray photoemission spectroscopy (XPS). Diethylzinc (DEZ) and O{sub 2} gas were used as precursor and reactant gas, respectively, and trimethyl gallium (TMGa) was used as a Ga doping source. Initially, the electrical properties of undoped LP-CVD ZnO films depending on the partial pressure of DEZ and O{sub 2} ratio were investigated using X-ray diffraction (XRD) by changing partial pressure of DEZ from 40 to 140 mTorr and that of O{sub 2} from 40 to 80 mTorr. The resistivity was reduced by Ga doping from 7.24 × 10{sup −3} Ω cm for undoped ZnO to 2.05 × 10{sup −3} Ω cm for Ga doped ZnO at the TMG pressure of 8 mTorr. The change of electric properties of Ga doped ZnO with varying the amount of Ga dopants was systematically discussed based on the structural crystallinity and chemical bonding configuration, analyzed by XRD and XPS, respectively.

Photocatalytic degradation of Reactive Black 5 and Malachite Green with ZnO and lanthanum doped nanoparticles

International Nuclear Information System (INIS)

Kaneva, N; Bojinova, A; Papazova, K

2016-01-01

Here we report the preparation of ZnO particles with different concentrations of La 3 + doping (0, 0.5 and 1 wt%) via sol-gel method. The nanoparticles are synthesized directly from Zn(CH 3 COO) 2 .2H 2 O in the presence of 1-propanol and triethylamine at 80°C. The conditions are optimized to obtain particles of uniform size, easy to isolate and purify. The nanoparticles are characterized by SEM, XRD and UV-Vis analysis. The photocatalytic properties of pure and La-doped ZnO are studied in the photobleaching of Malachite Green (MG) and Reactive Black 5 (RB5) dyes in aqueous solutions upon UV illumination. It is observed that the rate constant increases with the La loading up to 1 wt%. The doping helps to achieve complete mineralization of MG within a short irradiation time. 1 wt% La-doped ZnO nanoparticles show highest photocatalytic activity. The La 3+ doped ZnO particles degrade faster RB5 than MG. The reason is weaker N=N bond in comparison with the C-C bond between the central carbon atom and N,N-dimethylaminobenzyl in MG. The as-prepared ZnO particles can find practical application in photocatalytic purification of textile wastewaters. (paper)

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

KAUST Repository

Venkatesh, S.

2016-03-24

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

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

Energy Technology Data Exchange (ETDEWEB)

Venkatesh, S.; Baras, A.; Roqan, I. S., E-mail: Iman.roqan@kaust.edu.sa [Physical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900 (Saudi Arabia); Lee, J.-S. [Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States)

2016-03-15

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

Low-frequency zone boundary phonons in Li doped ZnO ceramics

Science.gov (United States)

Yadav, Harish Kumar; Sreenivas, K.; Gupta, Vinay; Katiyar, R. S.

2008-09-01

Room temperature Raman spectra of Li doped ZnO (Zn1-xLixO) ceramics with varying Li concentrations (x =0.0, 0.05, 0.10, and 0.15) are investigated in this study. Four peaks were identified at 96.6, 127, 157, and 194 cm-1 in the Li doped samples. The peaks at 127, 157, and 194 cm-1 are assigned to zone boundary phonons in ZnO [J. M. Calleja and M. Cardona, Phys. Rev. B 16, 3753 (1977)], and appear due to disorder in ZnO lattice with Li incorporation. Lithium, owing to its smaller radius, adjusts itself anywhere in the ZnO lattice and breaks the crystal translational symmetry to a large extent, compared to other dopants. Disorder in the lattice is seen to be finely modulated with varying Li content. The peak at 96.6 cm-1 is hypothesized to be a projection of the vibrational motion of Li atoms at lower frequencies, which contributes in a major fashion at higher frequencies, due to its lighter mass than Zn or O atoms.

NIR to visible upconversion in Er3+/Yb3+ co-doped CaYAl3O7 phosphor obtained by solution combustion process

International Nuclear Information System (INIS)

Singh, Vijay; Rai, Vineet Kumar; Al-Shamery, Katharina; Nordmann, Joerg; Haase, Markus

2011-01-01

Using the combustion synthesis, CaYAl 3 O 7 :Er 3+ phosphor powders co-doped with Yb 3+ have been prepared at low temperatures (550 o C) in a few minutes. Formation of the compound was confirmed by X-ray powder diffraction. Near-infrared to visible upconversion fluorescence emission in the Er 3+ doped CaYAl 3 O 7 phosphor powder has been observed. The effect of co-doping with triply ionized ytterbium in the CaYAl 3 O 7 :Er 3+ phosphor has been studied and the process involved is discussed. - Highlights: → The green emitting up-conversion CaYAl 3 O 7 :Er 3+ phosphor powders co-doped with Yb 3+ have been prepared by easy combustion method. → The combustion method is a simple, energy saving, fast and economical viable process. → The luminescence intensity in the co-doped phosphor is enhanced by several times compared to that of the singly (Er 3+ ) doped phosphor.

Photocatalytic degradation of the Paracetamol drug using Lanthanum doped ZnO nanoparticles and their in-vitro cytotoxicity assay

International Nuclear Information System (INIS)

Shakir, Mohammad; Faraz, Mohd; Sherwani, Mohd Asif; Al-Resayes, Saud I.

2016-01-01

The doping of semiconductor by rare earth metals nanoparticles is an effective way for increasing photocatalytic activity. Zinc oxide and Lanthanum doped Zinc oxide nanoparticles were synthesized by modifying the gel-combustion method. It was found that La can greatly enhance the cytotoxicity and photocatalytic activity of ZnO nanoparticles towards various cell lines and Paracetamol drug. These nanoparticles were characterized by various spectroscopic and other techniques which clearly revealed the presence of lanthanum ions. The absorption edge shifts towards the visible region after doping with La ions. This shift shows that the doping of La ions is favorable for absorbing the visible light. The comparative photocatalytic and cytotoxicity activity revealed that La doped ZnO nanoparticles remarkably enhanced activities as compared to the ZnO nanoparticles. The outcome of these studies offers valuable for planning La doped ZnO nanoparticles having cytotoxicity and photocatalytic activities helpful for the formulation of anticancer product and waste water remediation.

Photocatalytic degradation of the Paracetamol drug using Lanthanum doped ZnO nanoparticles and their in-vitro cytotoxicity assay

Energy Technology Data Exchange (ETDEWEB)

Shakir, Mohammad, E-mail: shakir078@yahoo.com [Department of Chemistry, Aligarh Muslim University, Aligarh 202002 (India); Faraz, Mohd [Department of Chemistry, Aligarh Muslim University, Aligarh 202002 (India); Sherwani, Mohd Asif [Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh 202002 (India); Al-Resayes, Saud I. [Department of Chemistry, College of Science, King Saud University, Riyadh 11451 (Saudi Arabia)

2016-08-15

The doping of semiconductor by rare earth metals nanoparticles is an effective way for increasing photocatalytic activity. Zinc oxide and Lanthanum doped Zinc oxide nanoparticles were synthesized by modifying the gel-combustion method. It was found that La can greatly enhance the cytotoxicity and photocatalytic activity of ZnO nanoparticles towards various cell lines and Paracetamol drug. These nanoparticles were characterized by various spectroscopic and other techniques which clearly revealed the presence of lanthanum ions. The absorption edge shifts towards the visible region after doping with La ions. This shift shows that the doping of La ions is favorable for absorbing the visible light. The comparative photocatalytic and cytotoxicity activity revealed that La doped ZnO nanoparticles remarkably enhanced activities as compared to the ZnO nanoparticles. The outcome of these studies offers valuable for planning La doped ZnO nanoparticles having cytotoxicity and photocatalytic activities helpful for the formulation of anticancer product and waste water remediation.

Sputter deposited gallium doped ZnO for TCO applications

Energy Technology Data Exchange (ETDEWEB)

Dietrich, Marc; Kronenberger, Achim; Polity, Angelika; Meyer, Bruno [I. Physikalisches Institut, Justus Liebig Universitaet Giessen (Germany); Blaesing, Juergen; Krost, Alois [FNW/IEP/AHE, Otto-von-Guericke Universitaet Magdeburg (Germany)

2010-07-01

Transparent conducting oxides to be used for flat panel or display applications should exhibit low electrical resistivity in line with a high optical transmission in the visible spectral range. Today indium-tin-oxide is the material which meets these requirements best. However, the limited availability of indium makes it useful to search for alternatives and ZnO doped with group III elements are promising candidates. While the Al doping in high concentrations causes problems due to the formation of insulating Al-oxides, Gallium related oxides are typically n-type conducting wide band gap semiconductors. Therefore we deposited Gallium doped ZnO thin films on quartz and sapphire substrates by radio frequency magnetron sputtering with a ZnO/Ga{sub 2}O{sub 3}(3at%) composite target. The substrate temperature and the oxygen flow during the sputtering process were varied to optimise the layer properties. Introducing oxygen to the sputtering gas allowed to vary the resistivity of the films by three orders of magnitude from about 1 {omega}cm down to less than 1 m{omega}cm.

Ionized zinc vacancy mediated ferromagnetism in copper doped ZnO thin films

Directory of Open Access Journals (Sweden)

Shi-Yi Zhuo

2012-03-01

Full Text Available This paper reports the origin of ferromagnetism in Cu-doped ZnO thin films. Room-temperature ferromagnetism is obtained in all the thin films when deposited at different oxygen partial pressure. An obviously enhanced peak corresponding to zinc vacancy is observed in the photoluminescence spectra, while the electrical spin resonance measurement implies the zinc vacancy is negative charged. After excluding the possibility of direct exchange mechanisms (via free carriers, we tentatively propose a quasi-indirect exchange model (via ionized zinc vacancy for Cu-doped ZnO system.

Formulation and Characterization of Cu Doped ZnO Thick Films as LPG Gas Sensor

Directory of Open Access Journals (Sweden)

A. V. PATIL

2010-12-01

Full Text Available Thick films of pure and various concentrations (1 wt. %, 3 wt. %, 5 wt. %, 7 wt. % and 10 wt. % of Cu-doped ZnO were prepared on alumina substrates using a screen printing technique. These films were fired at a temperature of 700ºC for two hours in an air atmosphere. Morphological, compositional and structural properties of the samples were obtained using the scanning electron microscopy (SEM, Energy dispersive spectroscopy (EDAX and X-ray diffraction techniques respectively. The LPG gas sensing properties of these thick films were investigated at different operating temperatures and LPG gas concentrations. The surface resistance of thick films decreases when exposed to LPG gas. The Cu doped films show significant sensitivity to LPG gas than pure ZnO film. 5 wt. % Cu-doped ZnO film was found to be more sensitive (87.3 % to LPG gas exposed at 300 oC than other doping concentrations with fast response and recovery time.

Optoelectronic properties of doped hydrothermal ZnO thin films

KAUST Repository

Mughal, Asad J.; Carberry, Benjamin; Oh, Sang Ho; Myzaferi, Anisa; Speck, James S.; Nakamura, Shuji; DenBaars, Steven P.

2017-01-01

, or In were evaluated for their optoelectronic properties. Inductively coupled plasma atomic emission spectroscopy was used to determine the concentration of dopants within the ZnO films. While Al and Ga-doped films showed linear incorporation rates

Synthesis and cathodoluminescence of Sb/P co-doped GaN nanowires

International Nuclear Information System (INIS)

Wang, Zaien; Liu, Baodan; Yuan, Fang; Hu, Tao; Zhang, Guifeng; Dierre, Benjamin; Hirosaki, Naoto; Sekiguchi, Takashi; Jiang, Xin

2014-01-01

Sb/P co-doped Gallium Nitride (GaN) nanowires were synthesized via a simple chemical vapor deposition (CVD) process by heating Ga 2 O 3 and Sb powders in NH 3 atmosphere. Scanning electron microscope (SEM), X-ray diffraction (XRD), transmission electron microscope (TEM) and energy dispersive X-ray spectroscopy (EDS) measurements confirmed the as-synthesized products were Sb/P co-doped GaN nanowires with rough morphology and hexagonal wurtzite structure. Room temperature cathodoluminescence (CL) demonstrated that an obvious band shift of GaN nanowires can be observed due to Sb/P co-doping. Possible explanation for the growth and luminescence mechanism of Sb/P co-doped GaN nanowires was discussed. Highlight: • Sb/P co-doped GaN nanowires were synthesized through a well-designed multi-channel chemical vapor deposition (CVD) process. • Sb/P co-doping leads to the crystallinity deterioration of GaN nanowires. • Sb/P co-doping caused the red-shift of GaN nanowires band-gap in UV range. • Compared with Sb doping, P atoms are more easy to incorporate into the GaN lattice

Enhanced local piezoelectric response in the erbium-doped ZnO nanostructures prepared by wet chemical synthesis

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Reza Zamiri

2017-03-01

Full Text Available Pure and erbium (Er doped ZnO nanostructures were prepared by simple and cost effective wet chemical precipitation method. The successful doping with phase purity of prepared ZnO nanostructure was confirmed by X-ray diffraction (XRD and their Rietveld analysis. The change in structural morphology of nanoscale features of prepared ZnO nanopowders on Er doping was observed from their scanning electron microscopy (SEM images. The presence of Er in prepared ZnO nanopowder was further confirmed from corresponding energy dispersive X-ray spectroscopy (EDX spectra of scanned SEM images. Piezoelectric properties of before (green samples and after sintering of consolidated compact of synthesized nanopowders were successfully measured. The out-of-plane (effective longitudinal and in-plane (effective shear coefficients of the samples were estimated from the local piezoresponse.

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

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Tamil Many K Thandavan

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

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

Science.gov (United States)

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

2015-01-01

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

Ferromagnetism in Gd doped ZnO nanowires: A first principles study

KAUST Repository

Aravindh, S. Assa

2014-12-19

In several experimental studies, room temperature ferromagnetism in Gd-doped ZnO nanostructures has been achieved. However, the mechanism and the origin of the ferromagnetism remain controversial. We investigate the structural, magnetic, and electronic properties of Zn 48O48 nanowires doped with Gd, using density functional theory. Our findings indicate that substitutionally incorporated Gd atoms prefer occupying the surface Zn sites. Moreover, the formation energy increases with the distance between Gd atoms, signifying that no Gd-Gd segregation occurs in the nanowires within the concentration limit of ≤2%. Gd induces ferromagnetism in ZnO nanowires with magnetic coupling energy up to 21 meV in the neutral state, which increases with additional electron and O vacancy, revealing the role of carriers in magnetic exchange. The potential for achieving room temperature ferromagnetism and high TC in ZnO:Gd nanowires is evident from the large ferromagnetic coupling energy (200 meV) obtained with the O vacancy. Density of states shows that Fermi level overlaps with Gd f states with the introduction of O vacancy, indicating the possibility of s-f coupling. These results will assist in understanding experimental findings in Gd-doped ZnO nanowires.

Ferromagnetism in Gd doped ZnO nanowires: A first principles study

KAUST Repository

Aravindh, S. Assa; Schwingenschlö gl, Udo; Roqan, Iman S.

2014-01-01

In several experimental studies, room temperature ferromagnetism in Gd-doped ZnO nanostructures has been achieved. However, the mechanism and the origin of the ferromagnetism remain controversial. We investigate the structural, magnetic, and electronic properties of Zn 48O48 nanowires doped with Gd, using density functional theory. Our findings indicate that substitutionally incorporated Gd atoms prefer occupying the surface Zn sites. Moreover, the formation energy increases with the distance between Gd atoms, signifying that no Gd-Gd segregation occurs in the nanowires within the concentration limit of ≤2%. Gd induces ferromagnetism in ZnO nanowires with magnetic coupling energy up to 21 meV in the neutral state, which increases with additional electron and O vacancy, revealing the role of carriers in magnetic exchange. The potential for achieving room temperature ferromagnetism and high TC in ZnO:Gd nanowires is evident from the large ferromagnetic coupling energy (200 meV) obtained with the O vacancy. Density of states shows that Fermi level overlaps with Gd f states with the introduction of O vacancy, indicating the possibility of s-f coupling. These results will assist in understanding experimental findings in Gd-doped ZnO nanowires.

Improving ultraviolet photodetection of ZnO nanorods by Cr doped ZnO encapsulation process

Science.gov (United States)

Safa, S.; Mokhtari, S.; Khayatian, A.; Azimirad, R.

2018-04-01

Encapsulated ZnO nanorods (NRs) with different Cr concentration (0-4.5 at.%) were prepared in two different steps. First, ZnO NRs were grown by hydrothermal method. Then, they were encapsulated by dip coating method. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy, and ultraviolet (UV)-visible spectrophotometer analyses. XRD analysis proved that Cr incorporated into the ZnO structure successfully. Based on optical analysis, band gap changes in the range of 2.74-3.84 eV. Finally, UV responses of all samples were deeply investigated. It revealed 0.5 at.% Cr doped sample had the most photocurrent (0.75 mA) and photoresponsivity (0.8 A/W) of all which were about three times greater than photocurrent and photoresponsivity of the undoped sample.

Improved electrical conduction properties in unintentionally-doped ZnO thin films treated by rapid thermal annealing

International Nuclear Information System (INIS)

Lee, Youngmin; Lee, Choeun; Shim, Eunhee; Jung, Eiwhan; Lee, Jinyong; Kim, Deukyoung; Lee, Sejoon; Fu, Dejun; Yoon, Hyungdo

2011-01-01

The effects of thermal treatments on the electrical conduction properties for the unintentionally doped ZnO thin films were investigated. Despite the decreased carrier density in the annealed ZnO thin films, the conductivity was increased because the contribution of the effective carrier mobility to the conductivity of the unintentionally-doped ZnO thin films is greater than that of the carrier density. The resistivity exponentially decreased with increasing RTA temperature, and this result was confirmed to come from the enhanced effective carrier-mobility, which originated from the increased crystallite size in the annealed ZnO thin films.

Improved electrical conduction properties in unintentionally-doped ZnO thin films treated by rapid thermal annealing

Energy Technology Data Exchange (ETDEWEB)

Lee, Youngmin; Lee, Choeun; Shim, Eunhee; Jung, Eiwhan; Lee, Jinyong; Kim, Deukyoung; Lee, Sejoon [Dongguk University-Seoul, Seoul (Korea, Republic of); Fu, Dejun [Wuhan University, Wuhan (China); Yoon, Hyungdo [Korea Electronics Technology Institute, Seongnam (Korea, Republic of)

2011-10-15

The effects of thermal treatments on the electrical conduction properties for the unintentionally doped ZnO thin films were investigated. Despite the decreased carrier density in the annealed ZnO thin films, the conductivity was increased because the contribution of the effective carrier mobility to the conductivity of the unintentionally-doped ZnO thin films is greater than that of the carrier density. The resistivity exponentially decreased with increasing RTA temperature, and this result was confirmed to come from the enhanced effective carrier-mobility, which originated from the increased crystallite size in the annealed ZnO thin films.

Realizing luminescent downshifting in ZnO thin films by Ce doping with enhancement of photocatalytic activity

Science.gov (United States)

Narayanan, Nripasree; Deepak, N. K.

2018-04-01

ZnO thin films doped with Ce at different concentration were deposited on glass substrates by spray pyrolysis technique. XRD analysis revealed the phase purity and polycrystalline nature of the films with hexagonal wurtzite geometry and the composition analysis confirmed the incorporation of Ce in the ZnO lattice in the case of doped films. Crystalline quality and optical transmittance diminished while electrical conductivity enhanced with Ce doping. Ce doping resulted in a red-shift of optical energy gap due to the downshift of the conduction band minimum after merging with Ce related impurity bands formed below the conduction band in the forbidden gap. In the room temperature photoluminescence spectra, UV emission intensity of the doped films decreased while the intensity of the visible emission band increased drastically implying the degradation in crystallinity as well as the incorporation of defect levels capable of luminescence downshifting. Ce doping showed improvement in photocatalytic efficiency by effectively trapping the free carriers and then transferring for dye degradation. Thus Ce doped ZnO thin films are capable of acting as luminescent downshifters as well as efficient photocatalysts.

Role of vacancy defects in Al doped ZnO thin films for optoelectronic devices

Science.gov (United States)

Rotella, H.; Mazel, Y.; Brochen, S.; Valla, A.; Pautrat, A.; Licitra, C.; Rochat, N.; Sabbione, C.; Rodriguez, G.; Nolot, E.

2017-12-01

We report on the electrical, optical and photoluminescence properties of industry-ready Al doped ZnO thin films grown by physical vapor deposition, and their evolution after annealing under vacuum. Doping ZnO with Al atoms increases the carrier density but also favors the formation of Zn vacancies, thereby inducing a saturation of the conductivity mechanism at high aluminum content. The electrical and optical properties of these thin layered materials are both improved by annealing process which creates oxygen vacancies that releases charge carriers thus improving the conductivity. This study underlines the effect of the formation of extrinsic and intrinsic defects in Al doped ZnO compound during the fabrication process. The quality and the optoelectronic response of the produced films are increased (up to 1.52 mΩ \\cdotcm and 3.73 eV) and consistent with the industrial device requirements.

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

Energy Technology Data Exchange (ETDEWEB)

Pathak, Trilok Kumar [Semiconductor Research Lab, Department of Physics, Gurukula Kangri University, Haridwar (India); Kumar, Vinod, E-mail: vinod.phy@gmail.com [Department of Physics, University of the Free State, Bloemfontein (South Africa); Swart, H.C., E-mail: swarthc@ufs.ac.za [Department of Physics, University of the Free State, Bloemfontein (South Africa); Purohit, L.P., E-mail: proflppurohitphys@gmail.com [Semiconductor Research Lab, Department of Physics, Gurukula Kangri University, Haridwar (India)

2016-01-01

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

UV shielding with visible transparency based properties of poly (styrene-co-acrylonitrile)/Ag doped ZnO nanocomposite

Science.gov (United States)

Singh, Rajender; Verma, Karan; Singh, Tejbir; Barman, P. B.; Sharma, Dheeraj

2018-02-01

Development of ultraviolet (UV) shielding with visible transparency based thermoplastic polymer nanocomposite (PNs) presents an important requisite in terms of their efficiency and cost. Present study contributed for the same approach by dispersion of Ag doped ZnO nanoparticles upto 10 wt% in poly (styrene-co-acrylonitrile) matrix by insitu emulsion polymerization method. The crystal and chemical structure of PNs has been analyzed by x-ray diffraction (XRD) and fourier infrared spectrometer (FTIR) techniques. The morphological and elemental information of synthesized nanomaterial has been studied by field emission scanning electron microscope (FESEM) and energy dispersive spectroscopy (EDS) technique. The optical properties of PNs has been studied by UV-visible spectroscopy technique. The incorporation of nanoparticles in polymer matrix absorb the complete UV light with visible transparency. The present reported polymer nanocomposite (PNs) have tuned refractive index with UV blocking and visible transparency based properties which can serve as a viable alternative as compared to related conventional materials.

Effect of Ag Doping on the Electronic Structure and Optical Properties of ZnO(0001 Surface

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Xiang Qian

2018-01-01

Full Text Available Using first-principle calculations, the geometrical structure, the electronic and optical properties of Ag-doped ZnO(0001 surface have been investigated. We found that Ag-doped ZnO(0001 surface is more easily formed on the first layer. On the other hand, the doped surface has gradually become an equipotential body, showing obvious metallic characteristics. We found that a new peak appeared in the low energy region after Ag doping, which was mainly due to the electron transition between the two orbital levels of Ag-4d and O-2p.

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

Science.gov (United States)

Giri, Pushpa; Chakrabarti, P.

2016-05-01

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

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.

Electron paramagnetic resonance in Cu-doped ZnO

Science.gov (United States)

Buchheit, R.; Acosta-Humánez, F.; Almanza, O.

2016-04-01

In this work, ZnO and Cu-doped ZnO nanoparticles (Zn1-xCuxO, x = 3%), with a calcination temperature of 500∘C were synthesized using the sol-gel method. The particles were analyzed using atomic absorption spectroscopy (AAS), X-ray diffraction (XRD) and electron paramagnetic resonance (EPR) at X-band, measurement in a temperature range from 90 K to room temperature. AAS confirmed a good correspondence between the experimental doping concentration and the theoretical value. XRD reveals the presence of ZnO phase in hexagonal wurtzite structure and a nanoparticle size for the samples synthesized. EPR spectroscopy shows the presence of point defects in both samples with g-values of g = 1.959 for shallow donors and g = 2.004 for ionized vacancies. It is important when these materials are required have been used as catalysts, as suggested that it is not necessary prepare them at higher temperature. A simulation of the Cu EPR signal using an anisotropic spin Hamiltonian was performed and showed good coincidence with the experimental spectra. It was shown that Cu2+ ions enter interstitial octahedral sites of orthorhombic symmetry in the wurtzite crystal structure. Temperature dependence of the EPR linewidth and signal intensity shows a paramagnetic behavior of the sample in the measurement range. A Néel temperature TN = 78 ± 19 K was determined.

Epitaxial growth of Sb-doped nonpolar a-plane ZnO thin films on r-plane sapphire substrates by RF magnetron sputtering

Energy Technology Data Exchange (ETDEWEB)

Chen, Hou-Guang, E-mail: houguang@isu.edu.tw [Department of Materials Science and Engineering, I-Shou University, Kaohsiung 840, Taiwan (China); Hung, Sung-Po [Department of Materials Science and Engineering, I-Shou University, Kaohsiung 840, Taiwan (China)

2014-02-15

Highlights: ► Sb-doped nonpolar a-plane ZnO layers were epitaxially grown on sapphire substrates. ► Crystallinity and electrical properties were studied upon growth condition and doping concentration. ► The out-of-plane lattice spacing of ZnO films reduces monotonically with increasing Sb doping level. ► The p-type conductivity of ZnO:Sb film is closely correlated with annealing condition and Sb doping level. -- Abstract: In this study, the epitaxial growth of Sb-doped nonpolar a-plane (112{sup ¯}0) ZnO thin films on r-plane (11{sup ¯}02) sapphire substrates was performed by radio-frequency magnetron sputtering. The influence of the sputter deposition conditions and Sb doping concentration on the microstructural and electrical properties of Sb-doped ZnO epitaxial films was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and the Hall-effect measurement. The measurement of the XRD phi-scan indicated that the epitaxial relationship between the ZnO:Sb layer and sapphire substrate was (112{sup ¯}0){sub ZnO}//(11{sup ¯}02){sub Al{sub 2O{sub 3}}} and [11{sup ¯}00]{sub ZnO}//[112{sup ¯}0]{sub Al{sub 2O{sub 3}}}. The out-of-plane a-axis lattice parameter of ZnO films was reduced monotonically with the increasing Sb doping level. The cross-sectional transmission electron microscopy (XTEM) observation confirmed the absence of any significant antimony oxide phase segregation across the thickness of the Sb-doped ZnO epitaxial film. However, the epitaxial quality of the films deteriorated as the level of Sb dopant increased. The electrical properties of ZnO:Sb film are closely correlated with post-annealing conditions and Sb doping concentrations.

Significant enhancement of room temperature ferromagnetism in surfactant coated polycrystalline Mn doped ZnO particles

Energy Technology Data Exchange (ETDEWEB)

Jayakumar, O.D. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Gopalakrishnan, I.K. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)]. E-mail: ikgopal@barc.gov.in; Sudakar, C. [Department of Physics and Astronomy, Wayne State University, Detroit, MI 48201 (United States); Kadam, R.M. [Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Kulshreshtha, S.K. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)

2007-07-12

We report a surfactant assisted synthesis of Mn doped ZnO polycrystalline samples showing robust room temperature ferromagnetism as characterized by X-ray diffraction analysis, transmission electron microscopy, electron paramagnetic resonance and DC magnetization measurements. This surfactant assisted synthesis method, developed by us, is found to be highly reproducible. Further, it can also be extended to the synthesis of other transition metal doped ZnO.

Enhancement in the structure quality of ZnO nanorods by diluted Co dopants: Analyses via optical second harmonic generation

International Nuclear Information System (INIS)

Liu, Chung-Wei; Hsiao, Chih-Hung; Chang, Shoou-Jinn; Brahma, Sanjaya; Chang, Feng Ming; Wang, Peng Han; Lo, Kuang-Yao

2015-01-01

We report a systematic study about the effect of cobalt concentration in the growth solution over the crystallization, growth, and optical properties of hydrothermally synthesized Zn 1−x Co x O [0 ≤ x ≤ 0.40, x is the weight (wt.) % of Co in the growth solution] nanorods. Dilute Co concentration of 1 wt. % in the growth solution enhances the bulk crystal quality of ZnO nanorods, and high wt. % leads to distortion in the ZnO lattice that depresses the crystallization, growth as well as the surface structure quality of ZnO. Although, Co concentration in the growth solution varies from 1 to 40 wt. %, the real doping concentration is limited to 0.28 at. % that is due to the low growth temperature of 80 °C. The enhancement in the crystal quality of ZnO nanorods at dilute Co concentration in the solution is due to the strain relaxation that is significantly higher for ZnO nanorods prepared without, and with high wt. % of Co in the growth solution. Second harmonic generation is used to investigate the net dipole distribution from these coatings, which provides detailed information about bulk and surface structure quality of ZnO nanorods at the same time. High quality ZnO nanorods are fabricated by a low-temperature (80 °C) hydrothermal synthesis method, and no post synthesis treatment is needed for further crystallization. Therefore, this method is advantageous for the growth of high quality ZnO coatings on plastic substrates that may lead toward its application in flexible electronics

Morphology-controllable of Sn doped ZnO nanorods prepared by spray pyrolysis for transparent electrode application

Science.gov (United States)

Hameed, M. Shahul; Princice, J. Joseph; Babu, N. Ramesh; Zahirullah, S. Syed; Deshmukh, Sampat G.; Arunachalam, A.

2018-05-01

Transparent conductive Sn doped ZnO nanorods have been deposited at various doping level by spray pyrolysis technique on glass substrate. The structural, surface morphological and optical properties of these films have been investigated with the help of X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscope (AFM) and UV-Vis spectrophotometer respectively. XRD patterns revealed a successful high quality growth of single crystal ZnO nanorods with hexagonal wurtzite structure having (002) preferred orientation. The scanning electron microscope (SEM) image of the prepared films exposed the uniform distribution of Sn doped ZnO nanorod shaped grains. All these films were highly transparent in the visible region with average transmittance of 90%.

Effects of Cr-doping on the photoluminescence and ferromagnetism at room temperature in ZnO nanomaterials prepared by soft chemistry route

International Nuclear Information System (INIS)

Wang Baiqi; Iqbal, Javed; Shan Xudong; Huang Guowei; Fu Honggang; Yu Ronghai; Yu Dapeng

2009-01-01

The pure and Cr-doped ZnO nanomaterials were prepared by soft chemistry route. The crystallinity and morphology of as-prepared ZnO nanomaterials were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM), which show that Cr-doping could influence crystal and improve the oriented growth of ZnO nanomaterials. The amount of contents and valence state of Cr ions were investigated by energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), which demonstrate that the Cr ions are uniformly doped about 2 atm% in each nanowire and are in +3 valence state in doped ZnO nanomaterials. The effect of Cr-doping on the photoluminescence (PL) and magnetic properties of as-prepared ZnO nanomaterials were principally investigated at room temperature. The Cr-doping can adjust the energy level of ZnO nanocrystal and increase the amount of defects and oxygen vacancies, which lead to shift in the emission peak position in ultraviolet (UV) region and enhance the PL performance in visible light (VL) region of ZnO nanomaterials. In addition, the presence of Cr dopant in ZnO structures establishes the room-temperature ferromagnetism, which is possibly related to the existence of defects and oxygen vacancies as well as due to exchange interaction between Cr 3d and O 2p spin moments

Positron annihilation studies of vacancy-type defects and room temperature ferromagnetism in chemically synthesized Li-doped ZnO nanocrystals

International Nuclear Information System (INIS)

Ghosh, S.; Khan, Gobinda Gopal; Mandal, K.; Thapa, Samudrajit; Nambissan, P.M.G.

2014-01-01

Highlights: • Evidence of zinc vacancy-induced intrinsic ferromagnetism in Li-doped ZnO. • Modification of defects and properties through alkali metal substitution. • Study of defect-modification using positron annihilation spectroscopy. • New way to prepare ZnO-based magnetic semiconductor for spintronic applications. -- Abstract: In this article, we have investigated the effects of Li incorporation on the lattice defects and room-temperature d 0 ferromagnetic behaviour in ZnO nanocrystals by correlating X-ray photoelectron, photoluminescence and positron annihilation spectroscopic study in details. It is found that at low doping level ( 1+ is an effective substituent of Zn site, but it prefers to occupy the interstitial positions when Li-doping exceeds 7 at.% resulting in lattice expansion and increase of particle sizes. The pristine ZnO nanocrystals exhibit ferromagnetic behaviour which is further enhanced significantly after few percentage of Li-doping in ZnO. The magnitude of both saturation magnetizations (M S ) as well as the Curie temperature (T C ) are found to increase considerably up to Li concentration of 10 at.% and then started to decrease on further Li-doping. The gradual enhancement of Zn vacancy (V Zn ) defects in ZnO nanocrystals due to Li substitution as confirmed from photoluminescence and positron annihilation spectroscopy measurements might be responsible to induce paramagnetic moments within ZnO host. The ferromagnetic exchange interaction between the localised moments of V Zn defects can be mediated though the holes arising due to Li-substitutional (Li Zn ) acceptor defects within ZnO. Hence, Li doping in ZnO favours in stabilizing considerable V Zn defects and thus helps to sustain long-range high-T C ferromagnetism in ZnO which can be a promising material in future spintronics

Spatially Correlated, Single Nanomaterial-Level Structural and Optical Profiling of Cu-Doped ZnO Nanorods Synthesized via Multifunctional Silicides

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Johnson Truong

2018-04-01

Full Text Available We demonstrate a straightforward and effective method to synthesize vertically oriented, Cu-doped ZnO nanorods (NRs using a novel multipurpose platform of copper silicide nanoblocks (Cu3Si NBs preformed laterally in well-defined directions on Si. The use of the surface-organized Cu3Si NBs for ZnO NR growth successfully results in densely assembled Cu-doped ZnO NRs on each NB platform, whose overall structures resemble thick bristles on a brush head. We show that Cu3Si NBs can uniquely serve as a catalyst for ZnO NRs, a local dopant source of Cu, and a prepatterned guide to aid the local assembly of the NRs on the growth substrate. We also ascertain the crystalline structures, optical properties, and spectroscopic signatures of the Cu-doped ZnO NRs produced on the NBs, both at each module of NRs/NB and at their ensemble level. Subsequently, we determine their augmented properties relative to the pristine form of undoped ZnO NRs and the source material of Cu3Si NBs. We provide spatially correlated structural and optical data for individual modules of Cu-doped ZnO NRs assembled on a Cu3Si NB by resolving them along the different positions on the NB. Ensemble-averaged versus individual behaviors of Cu-doped ZnO NRs on Cu3Si NBs are then compared. We further discuss the potential impact of such ZnO-derived NRs on their relatively unexplored biological and biomedical applications. Our efforts will be particularly useful when exploiting each integrated module of self-aligned, Cu-doped ZnO NRs on a NB as a discretely addressable, active element in solid-state sensors and miniaturized luminescent bioprobes.

Positron annihilation studies of vacancy-type defects and room temperature ferromagnetism in chemically synthesized Li-doped ZnO nanocrystals

Energy Technology Data Exchange (ETDEWEB)

Ghosh, S., E-mail: sghoshphysics@gmail.com [S.N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700098 (India); Khan, Gobinda Gopal [Centre for Research in Nanoscience and Nanotechnology, University of Calcutta, Technology Campus, Block JD2, Sector III, Salt Lake City, Kolkata 700098 (India); Mandal, K. [S.N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700098 (India); Thapa, Samudrajit; Nambissan, P.M.G. [Centre for Research in Nanoscience and Nanotechnology, University of Calcutta, Technology Campus, Block JD2, Sector III, Salt Lake City, Kolkata 700098 (India); Saha Institute of Nuclear Physics, Sector 1, Block AF, Bidhannagar, Kolkata 700064 (India)

2014-03-25

Highlights: • Evidence of zinc vacancy-induced intrinsic ferromagnetism in Li-doped ZnO. • Modification of defects and properties through alkali metal substitution. • Study of defect-modification using positron annihilation spectroscopy. • New way to prepare ZnO-based magnetic semiconductor for spintronic applications. -- Abstract: In this article, we have investigated the effects of Li incorporation on the lattice defects and room-temperature d{sup 0} ferromagnetic behaviour in ZnO nanocrystals by correlating X-ray photoelectron, photoluminescence and positron annihilation spectroscopic study in details. It is found that at low doping level (<7 at.%), Li{sup 1+} is an effective substituent of Zn site, but it prefers to occupy the interstitial positions when Li-doping exceeds 7 at.% resulting in lattice expansion and increase of particle sizes. The pristine ZnO nanocrystals exhibit ferromagnetic behaviour which is further enhanced significantly after few percentage of Li-doping in ZnO. The magnitude of both saturation magnetizations (M{sub S}) as well as the Curie temperature (T{sub C}) are found to increase considerably up to Li concentration of 10 at.% and then started to decrease on further Li-doping. The gradual enhancement of Zn vacancy (V{sub Zn}) defects in ZnO nanocrystals due to Li substitution as confirmed from photoluminescence and positron annihilation spectroscopy measurements might be responsible to induce paramagnetic moments within ZnO host. The ferromagnetic exchange interaction between the localised moments of V{sub Zn} defects can be mediated though the holes arising due to Li-substitutional (Li{sub Zn}) acceptor defects within ZnO. Hence, Li doping in ZnO favours in stabilizing considerable V{sub Zn} defects and thus helps to sustain long-range high-T{sub C} ferromagnetism in ZnO which can be a promising material in future spintronics.

Electrical properties of lightly Ga-doped ZnO nanowires

Science.gov (United States)

Alagha, S.; Heedt, S.; Vakulov, D.; Mohammadbeigi, F.; Senthil Kumar, E.; Schäpers, Th; Isheim, D.; Watkins, S. P.; Kavanagh, K. L.

2017-12-01

We investigated the growth, crystal structure, elemental composition and electrical transport characteristics of ZnO nanowires, a promising candidate for optoelectronic applications in the UV-range. Nominally-undoped and Ga-doped ZnO nanowires were grown by metal-organic chemical vapor deposition. Photoluminescence measurements confirmed the incorporation of Ga via donor-bound exciton emission. With atom-probe tomography we estimated an upper limit of the Ga impurity concentration ({10}18 {{cm}}-3). We studied the electrical transport characteristics of these nanowires with a W-nanoprobe technique inside a scanning electron microscope and with lithographically-defined contacts allowing back-gated measurements. An increase in apparent resistivity by two orders of magnitude with decreasing radius was measured with both techniques with a much larger distribution width for the nanoprobe method. A drop in the effective carrier concentration and mobility was found with decreasing radius which can be attributed to carrier depletion and enhanced scattering due to surface states. Little evidence of a change in resistivity was observed with Ga doping, which indicates that the concentration of native or background dopants is higher than the Ga doping concentration.

Ferromagnetism in Gd doped ZnO nanowires: A first principles study

Energy Technology Data Exchange (ETDEWEB)

Aravindh, S. Assa; Schwingenschloegl, Udo, E-mail: udo.schwingenschloegl@kaust.edu.sa, E-mail: iman.roqan@kaust.edu.sa; Roqan, Iman S., E-mail: udo.schwingenschloegl@kaust.edu.sa, E-mail: iman.roqan@kaust.edu.sa [Physical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900 (Saudi Arabia)

2014-12-21

In several experimental studies, room temperature ferromagnetism in Gd-doped ZnO nanostructures has been achieved. However, the mechanism and the origin of the ferromagnetism remain controversial. We investigate the structural, magnetic, and electronic properties of Zn{sub 48}O{sub 48} nanowires doped with Gd, using density functional theory. Our findings indicate that substitutionally incorporated Gd atoms prefer occupying the surface Zn sites. Moreover, the formation energy increases with the distance between Gd atoms, signifying that no Gd-Gd segregation occurs in the nanowires within the concentration limit of ≤2%. Gd induces ferromagnetism in ZnO nanowires with magnetic coupling energy up to 21 meV in the neutral state, which increases with additional electron and O vacancy, revealing the role of carriers in magnetic exchange. The potential for achieving room temperature ferromagnetism and high T{sub C} in ZnO:Gd nanowires is evident from the large ferromagnetic coupling energy (200 meV) obtained with the O vacancy. Density of states shows that Fermi level overlaps with Gd f states with the introduction of O vacancy, indicating the possibility of s-f coupling. These results will assist in understanding experimental findings in Gd-doped ZnO nanowires.

Preparation, structural and luminescent properties of nanocrystalline ZnO films doped Ag by close space sublimation method

Science.gov (United States)

Khomchenko, Viktoriya; Mazin, Mikhail; Sopinskyy, Mykola; Lytvyn, Oksana; Dan'ko, Viktor; Piryatinskii, Yurii; Demydiuk, Pavlo

2018-05-01

The simple way for silver doping of ZnO films is presented. The ZnO films were prepared by reactive rf-magnetron sputtering on silicon and sapphire substrates. Ag doping is carried out by sublimation of the Ag source located at close space at atmospheric pressure in air. Then the ZnO and ZnO-Ag films were annealed in wet media. The microstructure and optical properties of the films were compared and studied by atomic force microscopy (AFM), X-ray diffraction (XRD), photoluminescence (PL) and cathodoluminescence (CL). XRD results indicated that all the ZnO films have a polycrystalline hexagonal structure and a preferred orientation with the c-axis perpendicular to the substrate. The annealing and Ag doping promote increasing grain's sizes and modification of grain size distribution. The effect of substrate temperature, substrate type, Ag doping and post-growth annealing of the films was studied by PL spectroscopy. The effect of Ag doping was obvious and identical for all the films, namely the wide visible bands of PL spectra are suppressed by Ag doping. The intensity of ultraviolet band increased 15 times as compared to their reference films on sapphire substrate. The ultraviolet/visible emission ratio was 20. The full width at half maximum (FWHM) for a 380 nm band was 14 nm, which is comparable with that of epitaxial ZnO. The data implies the high quality of ZnO-Ag films. Possible mechanisms to enhance UV emission are discussed.

Activities towards p-type doping of ZnO

International Nuclear Information System (INIS)

Brauer, G; Kuriplach, J; Ling, C C; Djurisic, A B

2011-01-01

Zinc oxide (ZnO) is an interesting and promising semiconductor material for many potential applications, e.g. in opto-electronics and for sensor devices. However, its p-type doping represents a challenging problem, and the physical reasons of its mostly n-type conductivity are not perfectly clear at present. Efforts to achieve p-type conductivity by ion implantation are reviewed, and ways to achieve p-type ZnO nanorods and thin films through various growth conditions are summarized. Then, issues associated with the preparation of Schottky contacts is discussed in some detail as this is a requirement of the device formation process. Finally, the possible incorporation of hydrogen and nitrogen into structural defects, which can act as trapping sites for positrons, is discussed in the context of experimental and theoretical positron results and the estimated H and N content in a variety of ZnO materials.

Activities towards p-type doping of ZnO

Energy Technology Data Exchange (ETDEWEB)

Brauer, G [Institut fuer Ionenstrahlphysik und Materialforschung, Forschungszentrum Dresden-Rossendorf, Postfach 510119, D-01314 Dresden (Germany); Kuriplach, J [Department of Low Temperature Physics, Charles University, V Holetovickach 2, CZ-18000 Prague (Czech Republic); Ling, C C; Djurisic, A B, E-mail: g.brauer@fzd.de [Department of Physics, University of Hong Kong, Pokfulam Road (Hong Kong)

2011-01-10

Zinc oxide (ZnO) is an interesting and promising semiconductor material for many potential applications, e.g. in opto-electronics and for sensor devices. However, its p-type doping represents a challenging problem, and the physical reasons of its mostly n-type conductivity are not perfectly clear at present. Efforts to achieve p-type conductivity by ion implantation are reviewed, and ways to achieve p-type ZnO nanorods and thin films through various growth conditions are summarized. Then, issues associated with the preparation of Schottky contacts is discussed in some detail as this is a requirement of the device formation process. Finally, the possible incorporation of hydrogen and nitrogen into structural defects, which can act as trapping sites for positrons, is discussed in the context of experimental and theoretical positron results and the estimated H and N content in a variety of ZnO materials.

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

Electrodeposition of Cu-doped ZnO nanowire arrays and heterojunction formation with p-GaN for color tunable light emitting diode applications

International Nuclear Information System (INIS)

Lupan, O.; Pauporté, T.; Viana, B.; Aschehoug, P.

2011-01-01

Highlights: ► High quality copper-doped zinc oxide nanowires were electrochemically grown at low temperature. ► ZnO:Cu nanowires have been epitaxially grown on Mg-doped p-GaN single-crystalline layers. ► The (ZnO:Cu NWs)/(p-GaN:Mg) heterojunction was used to fabricate a light-emitting diode structure. ► The photo- and electroluminescence emission was red-shifted to the violet spectral region compared to pure ZnO. ► The results are of importance for band-gap engineering of ZnO and for color-tunable LED. - Abstract: Copper-doped zinc oxide (ZnO:Cu) nanowires (NWs) were electrochemically deposited at low temperature on fluor-doped tin oxide (FTO) substrates. The electrochemical behavior of the Cu–Zn system for Cu-doped ZnO electrodeposition was studied and the electrochemical reaction mechanism is discussed. The synthesized ZnO arrayed layers were investigated by using SEM, XRD, EDX, photoluminescence and Raman techniques. X-ray diffraction analysis demonstrates a decrease in the lattice parameters of Cu-doped ZnO NWs. Structural analyses show that the nanomaterial is of hexagonal structure with the Cu incorporated in ZnO NWs probably by substituting zinc in the host lattice. Photoluminescence studies on pure and Cu-doped ZnO NWs shows that the near band edge emission is red-shifted by about 5 or 12 nm depending on Cu(II) concentration in the electrolytic bath solution (3 or 6 μmol l −1 ). Cu-doped ZnO NWs have been also epitaxially grown on Mg doped p-GaN single-crystalline layers and the (ZnO:Cu NWs)/(p-GaN:Mg) heterojunction has been used to fabricate a light-emitting diode (LED) structure. The emission was red-shifted to the visible violet spectral region compared to pure ZnO. The present work demonstrates the ability of electrodeposition to produce high quality ZnO nanowires with tailored optical properties by doping. The obtained results are of great importance for further studies on bandgap engineering of ZnO, for color-tunable LED applications

Upconversion in rare earth ions doped TeO2-ZnO glass

International Nuclear Information System (INIS)

Mohanty, Deepak Kumar; Rai, Vineet Kumar

2012-01-01

The Er 3+ /Yb 3+ doped/codoped TeO 2 -ZnO glasses have been fabricated by conventional melt and quenching technique. The absorption spectra of the doped/codoped glasses have been performed. The visible upconversion emissions of both doped and codoped glasses have been observed using 808 nm diode laser excitation. The process involved in upconversion emissions has been discussed in detail. (author)

Structural and Optical Properties of Eu Doped ZnO Nanorods prepared by Pulsed Laser Deposition

KAUST Repository

Alarawi, Abeer

2014-06-23

Nano structured wide band gap semiconductors have attracted attention of many researchers due to their potential electronic and optoelectronic applications. In this thesis, we report successful synthesis of well aligned Eu doped ZnO nano-rods prepared, for the first time to our knowledge, by pulsed laser deposition (PLD) without any catalyst. X-ray diffraction (XRD) patterns shows that these Eu doped ZnO nanorods are grown along the c-axis of ZnO wurtzite structure. We have studied the effect of the PLD growth conditions on forming vertically aligned Eu doped ZnO nanorods. The structural properties of the material are investigated using a -scanning electron microscope (SEM). The PLD parameters must be carefully controlled in order to obtain c-axis oriented ZnO nanorods on sapphire substrates, without the use of any catalyst. The experiments conducted in order to identify the optimal growth conditions confirmed that, by adjusting the target-substrate distance, substrate temperature, laser energy and deposition duration, the nanorod size could be successfully controlled. Most importantly, the results indicated that the photoluminescence (PL) properties reflect the quality of the ZnO nanorods. These parameters can change the material’s structure from one-dimensional to two-dimensional however the laser energy and frequency affect the size and the height of the nanorods; the xygen pressure changes the density of the nanorods.

Enhanced Photocatalytic Activity of Rare Earth Metal (Nd and Gd doped ZnO Nanostructures

Directory of Open Access Journals (Sweden)

P. Logamani

2017-06-01

Full Text Available Presence of harmful organic pollutants in wastewater effluents causes serious environmental problems and therefore purification of this contaminated water by a cost effective treatment method is one of the most important issue which is in urgent need of scientific research. One such promising treatment technique uses semiconductor photocatalyst for the reduction of recalcitrant pollutants in water. In the present work, rare earth metals (Nd and Gd doped ZnO nanostructured photocatalyst have been synthesized by wet chemical method. The prepared samples were characterized by X-ray diffraction (XRD, Field Emission Scanning Electron Microscopy (FESEM and energy dispersive X-ray spectroscopy (EDS. The XRD results showed that the prepared samples were well crystalline with hexagonal Wurtzite structure. The results of EDS revealed that rare earth elements were doped into ZnO structure. The effect of rare earth dopant on morphology and photocatalytic degradation properties of the prepared samples were studied and discussed. The results revealed that the rare earth metal doped ZnO samples showed enhanced visible light photocatalytic activity for the degradation of methylene blue dye than pure nano ZnO photocatalyst.

Synthesis and characterization of single-phase Mn-doped ZnO

Science.gov (United States)

Chattopadhyay, S.; Dutta, S.; Banerjee, A.; Jana, D.; Bandyopadhyay, S.; Chattopadhyay, S.; Sarkar, A.

2009-05-01

Different samples of Zn 1-xMn xO series have been prepared using conventional solid-state sintering method. We identified up to what extent doping will enable us to synthesize single-phase polycrystalline Mn-doped ZnO sample, which is one of the prerequisites for dilute magnetic semiconductor, and we have analyzed its some other physical aspects. In synthesizing the samples, proportion of Mn varies from 1 to 5 at%. However, the milling time varied (6, 12, 24, 48 and 96 h) only for 2 at% Mn-doped samples while for other samples (1, 3, 4 and 5 at% Mn doped) the milling time has been fixed to 96 h. Room-temperature X-ray diffraction (XRD) data reveal that all of the prepared samples up to 3 at% of Mn doping exhibit wurtzite-type structure, and no segregation of Mn and/or its oxides has been found. The 4 at% Mn-doped samples show a weak peak of ZnMn 2O 4 apart from the other usual peaks of ZnO and the intensity of this impurity peak has been further increased for 5 at% of Mn doping. So beyond 3 at% doping, single-phase behavior is destroyed. Band gap for all the 2 at% Mn-doped samples has been estimated to be between 3.21 and 3.19 eV and the reason for this low band gap values has been explained through the grain boundary trapping model. The room-temperature resistivity measurement shows an increase of resistivity up to 48 h of milling and with further milling it saturates. The defect state of these samples has been investigated using the positron annihilation lifetime (PAL) spectroscopy technique. Here all the relevant lifetime parameters of positron i.e. free annihilation ( τ1) at defect site ( τ2) and average ( τav) increases with milling time.

Synthesis and characterization of single-phase Mn-doped ZnO

International Nuclear Information System (INIS)

Chattopadhyay, S.; Dutta, S.; Banerjee, A.; Jana, D.; Bandyopadhyay, S.; Chattopadhyay, S.; Sarkar, A.

2009-01-01

Different samples of Zn 1-x Mn x O series have been prepared using conventional solid-state sintering method. We identified up to what extent doping will enable us to synthesize single-phase polycrystalline Mn-doped ZnO sample, which is one of the prerequisites for dilute magnetic semiconductor, and we have analyzed its some other physical aspects. In synthesizing the samples, proportion of Mn varies from 1 to 5 at%. However, the milling time varied (6, 12, 24, 48 and 96 h) only for 2 at% Mn-doped samples while for other samples (1, 3, 4 and 5 at% Mn doped) the milling time has been fixed to 96 h. Room-temperature X-ray diffraction (XRD) data reveal that all of the prepared samples up to 3 at% of Mn doping exhibit wurtzite-type structure, and no segregation of Mn and/or its oxides has been found. The 4 at% Mn-doped samples show a weak peak of ZnMn 2 O 4 apart from the other usual peaks of ZnO and the intensity of this impurity peak has been further increased for 5 at% of Mn doping. So beyond 3 at% doping, single-phase behavior is destroyed. Band gap for all the 2 at% Mn-doped samples has been estimated to be between 3.21 and 3.19 eV and the reason for this low band gap values has been explained through the grain boundary trapping model. The room-temperature resistivity measurement shows an increase of resistivity up to 48 h of milling and with further milling it saturates. The defect state of these samples has been investigated using the positron annihilation lifetime (PAL) spectroscopy technique. Here all the relevant lifetime parameters of positron i.e. free annihilation (τ 1 ) at defect site (τ 2 ) and average (τ av ) increases with milling time.

Aluminium doping induced enhancement of p-d coupling in ZnO

International Nuclear Information System (INIS)

Cong, G W; Peng, W Q; Wei, H Y; Liu, X L; Wu, J J; Han, X X; Zhu, Q S; Wang, Z G; Ye, Z Z; Lu, J G; Zhu, L P; Qian, H J; Su, R; Hong, C H; Zhong, J; Ibrahim, K; Hu, T D

2006-01-01

Valence-band type Auger lines in Al doped and undoped ZnO were comparatively studied with the corresponding core level x-ray photoelectron spectrography (XPS) spectra as references. Then the shift trend of energy levels in the valence band was that p and p-s-d states move upwards but e and p-d states downwards with increasing Al concentration. The decreased energy of the Zn 3d state is larger than the increased energy of the O 2p state, indicating the lowering of total energy. This may indicate that Al doping could induce the enhancement of p-d coupling in ZnO, which originates from stronger Al-O hybridization. The shifts of these states and the mechanism were confirmed by valence band XPS spectra and O K-edge x-ray absorption spectrography (XAS) spectra. Finally, some previously reported phenomena are explained based on the Al doping induced enhancement of p-d coupling

Influence of Fe-doping on the structural, optical and magnetic properties of ZnO nanoparticles

International Nuclear Information System (INIS)

Liu Changzhen; Meng Dawei; Pang Haixia; Wu Xiuling; Xie Jing; Yu Xiaohong; Chen Long; Liu Xiaoyang

2012-01-01

Zn 1–x Fe x O (x=0–0.05) nanoparticles were synthesized without a catalyst by a two-step method. Fe was doped into ZnO by a source of metallic Fe sheets in a solid–liquid system at 80 °C, and the Zn 1−x Fe x O nanoparticles were obtained by annealing at 300 °C. X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy were used to characterize the structural properties of the as-grown Zn 1−x Fe x O. The optical properties were determined by Infrared and Ultraviolet–visible spectroscopy. The results confirm that the crystallinity of the ZnO is deteriorated due to Fe-doping. XPS results show that there is a mixture of Fe 0+ and the Fe 3+ in the representative Zn 0.95 Fe 0.05 O sample. The optical band gap of Zn 1−x Fe x O is enhanced with increasing of Fe-doping. Room temperature ferromagnetism was observed in all the Fe-doped ZnO samples. - Highlights: ► Zn 1−x Fe x O nanoparticles were synthesized with a simple two-step method. ► The Zn 1−x Fe x O predecessors were synthesized at a low temperature. ► Fe element was readily doped from the source of metallic Fe sheet. ► All the Fe doping ZnO samples have room temperature ferromagnetism. ► The structural and properties of the Zn 1−x Fe x O are regular with different x.

Title: Using Alignment and 2D Network Simulations to Study Charge Transport Through Doped ZnO Nanowire Thin Film Electrodes

KAUST Repository

Phadke, Sujay

2011-09-30

Factors affecting charge transport through ZnO nanowire mat films were studied by aligning ZnO nanowires on substrates and coupling experimental measurements with 2D nanowire network simulations. Gallium doped ZnO nanowires were aligned on thermally oxidized silicon wafer by shearing a nanowire dispersion in ethanol. Sheet resistances of nanowire thin films that had current flowing parallel to nanowire alignment direction were compared to thin films that had current flowing perpendicular to nanowire alignment direction. Perpendicular devices showed ∼5 fold greater sheet resistance than parallel devices supporting the hypothesis that aligning nanowires would increase conductivity of ZnO nanowire electrodes. 2-D nanowire network simulations of thin films showed that the device sheet resistance was dominated by inter-wire contact resistance. For a given resistivity of ZnO nanowires, the thin film electrodes would have the lowest possible sheet resistance if the inter-wire contact resistance was one order of magnitude lower than the single nanowire resistance. Simulations suggest that the conductivity of such thin film devices could be further enhanced by using longer nanowires. Solution processed Gallium doped ZnO nanowires are aligned on substrates using an innovative shear coating technique. Nanowire alignment has shown improvement in ZnO nanowire transparent electrode conductivity. 2D network simulations in conjunction with electrical measurements have revealed different regimes of operation of nanowire thin films and provided a guideline for improving electrical performance of nanowire electrodes. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Genesis of flake-like morphology and dye-sensitized solar cell performance of Al-doped ZnO particles: a study

International Nuclear Information System (INIS)

Sengupta, D.; Mondal, B.; Mukherjee, K.

2017-01-01

In dye-sensitized solar cell (DSSC) application, the particulate morphologies of photo-anode facilitate efficient dye loading and thus lead to better photo-conversion efficiency than their thin film counterpart. However, till date, the electronic and optical properties as well as the DSSC application of Al-doped ZnO (AZO) particles as photo-anode material is studied less than thin films. Herein, phase formation behavior, morphology evolution, optical properties, and dye-sensitized solar cell performance of wet chemically prepared ZnO and AZO (dopant level: 1–4 mol%) particles are studied. It is found that Al doping modulates significantly the ZnO morphology which in turn results the maximum dye adsorption as well as best photo-conversion efficiency at optimum dopant concentration. Specifically, the nanoparticle of ZnO turns predominantly to flake-like morphology with a higher surface area when 2 mol% Al is doped. Such morphology modulation is expected, since the crystallinity, lattice parameters, and lattice strain of ZnO changes appreciably with Al doping. The variations of optical properties (absorbance, diffused reflectance, and band gap) of AZO materials as compared to primitive ZnO are also identified through UV-vis studies. An attempt is made here to correlate the structural features with the photovoltaic performances of ZnO and AZO.

Genesis of flake-like morphology and dye-sensitized solar cell performance of Al-doped ZnO particles: a study

Energy Technology Data Exchange (ETDEWEB)

Sengupta, D.; Mondal, B.; Mukherjee, K., E-mail: kalisadhanm@yahoo.com [CSIR-Central Mechanical Engineering Research Institute, Centre for Advanced Materials Processing (India)

2017-03-15

In dye-sensitized solar cell (DSSC) application, the particulate morphologies of photo-anode facilitate efficient dye loading and thus lead to better photo-conversion efficiency than their thin film counterpart. However, till date, the electronic and optical properties as well as the DSSC application of Al-doped ZnO (AZO) particles as photo-anode material is studied less than thin films. Herein, phase formation behavior, morphology evolution, optical properties, and dye-sensitized solar cell performance of wet chemically prepared ZnO and AZO (dopant level: 1–4 mol%) particles are studied. It is found that Al doping modulates significantly the ZnO morphology which in turn results the maximum dye adsorption as well as best photo-conversion efficiency at optimum dopant concentration. Specifically, the nanoparticle of ZnO turns predominantly to flake-like morphology with a higher surface area when 2 mol% Al is doped. Such morphology modulation is expected, since the crystallinity, lattice parameters, and lattice strain of ZnO changes appreciably with Al doping. The variations of optical properties (absorbance, diffused reflectance, and band gap) of AZO materials as compared to primitive ZnO are also identified through UV-vis studies. An attempt is made here to correlate the structural features with the photovoltaic performances of ZnO and AZO.

Effect of calcination temperature on the structural, optical and magnetic properties of pure and Fe-doped ZnO nanoparticles

Directory of Open Access Journals (Sweden)

Pal Singh Raminder Preet

2016-06-01

Full Text Available In the present study, pure ZnO and Fe-doped ZnO (Zn0.97Fe0.03O nanoparticles were synthesized by simple coprecipitation method with zinc acetate, ferric nitrate and sodium hydroxide precursors. Pure ZnO and Fe-doped ZnO were further calcined at 450 °C, 600 °C and 750 °C for 2 h. The structural, morphological and optical properties of the samples were characterized by X-ray diffractometer (XRD, scanning electron microscope (SEM, energy dispersive spectroscopy (EDS and UV-Vis absorption spectroscopy. The X-ray diffraction studies revealed that the as-synthesized pure and doped ZnO nanoparticles have hexagonal wurtzite structure. The average crystallite size was calculated using Debye-Scherrer’s formula. The particle size was found to be in nano range and increased with an increase in calcination temperature. SEM micrographs confirmed the formation of spherical nanoparticles. Elemental compositions of various elements in pure and doped ZnO nanoparticles were determined by EDX spectroscopy. UV-Vis absorption spectra showed red shift (decrease in band gap with increasing calcination temperature. Effect of calcination on the magnetic properties of Fe-doped ZnO sample was also studied using vibrating sample magnetometer (VSM. M-H curves at room temperature revealed that coercivity and remanent polarization increase with an increase in calcination temperature from 450 °C to 750 °C, whereas reverse effect was observed for magnetization saturation.

Role of Fe doping on structural and vibrational properties of ZnO nanostructures

Energy Technology Data Exchange (ETDEWEB)

Pandiyarajan, T.; Udayabhaskar, R.; Karthikeyan, B. [National Institute of Technology, Department of Physics, Tiruchirappalli (India)

2012-05-15

In this report, Raman and Fourier Transform Infrared (FTIR) measurements were carried out to study the phonon modes of pure and Fe doped ZnO nanoparticles. The nanoparticles were prepared by sol-gel technique at room temperature. The X-ray diffraction measurements reveal that the nanoparticles are in hexagonal wurtzite structure and doping makes the shrinkage of the lattice parameters, whereas there is no alteration in the unit cell. Raman measurements show both E{sub 2}{sup low} and E{sub 2}{sup High} optical phonon mode is shifted towards lower wave number with Fe incorporation and explained on the basis of force constant variation, stress measurements, respectively. In addition, Fe related local vibrational modes (LVM) were observed for higher concentration of Fe doping. FTIR spectra reveal a band at 444 cm{sup -1} which is specific to E{sub 1} (TO) mode; a red-shift of this mode in Fe doped samples and some surface phonon modes were observed. Furthermore, the observation of additional IR modes, which is considered to have an origin related to Fe dopant in the ZnO nanostructures, is also reported. These additional mode features can be regarded as an indicator for the incorporation of Fe ions into the lattice position of the ZnO nanostructures. (orig.)

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

International Nuclear Information System (INIS)

Ilyas, Usman; Rawat, R.S.; Roshan, G.; Tan, T.L.; Lee, P.; Springham, S.V.; Zhang, Sam; Fengji Li; Chen, R.; Sun, H.D.

2011-01-01

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

Magnetic and optical properties of manganese doped ZnO nanoparticles synthesized by sol-gel technique

KAUST Repository

Omri, Karim; El Ghoul, Jaber; Lemine, O. M.; Bououdina, M.; Zhang, Bei; El Mir, Lassaad

2013-01-01

Mn doped ZnO nanoparticles with different doping concentration (1, 2, 3, 4, 5 at.%) were prepared by sol-gel method using supercritical drying conditions of ethyl alcohol. The structural, morphological, optical and magnetic properties of the as-prepared nanoparticles were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV measurements and superconducting quantum interference device (SQUID). The structural properties showed that the undoped and Mn doped ZnO nanoparticles exhibit hexagonal wurtzite structure. From the optical studies, the transmittance in UV region was decreased with the increase of Mn concentration. For Mn doped ZnO nanoparticles the optical band gap varies between 3.34 eV and 3.22 eV. It was found that the doping Mn 2+ ions have a significant influence on the optical properties. The magnetic characterization of the samples with 1% and 5% Mn concentrations reveal diamagnetic behavior for the first one and the presence of both paramagnetic and ferromagnetic behavior for the second. The room ferromagnetic component is due to the presence of the secondary phase ZnOMn3 which is confirmed by XRD study. © 2013 Elsevier Ltd. All rights reserved.

Magnetic and optical properties of manganese doped ZnO nanoparticles synthesized by sol-gel technique

KAUST Repository

Omri, Karim

2013-08-01

Mn doped ZnO nanoparticles with different doping concentration (1, 2, 3, 4, 5 at.%) were prepared by sol-gel method using supercritical drying conditions of ethyl alcohol. The structural, morphological, optical and magnetic properties of the as-prepared nanoparticles were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV measurements and superconducting quantum interference device (SQUID). The structural properties showed that the undoped and Mn doped ZnO nanoparticles exhibit hexagonal wurtzite structure. From the optical studies, the transmittance in UV region was decreased with the increase of Mn concentration. For Mn doped ZnO nanoparticles the optical band gap varies between 3.34 eV and 3.22 eV. It was found that the doping Mn 2+ ions have a significant influence on the optical properties. The magnetic characterization of the samples with 1% and 5% Mn concentrations reveal diamagnetic behavior for the first one and the presence of both paramagnetic and ferromagnetic behavior for the second. The room ferromagnetic component is due to the presence of the secondary phase ZnOMn3 which is confirmed by XRD study. © 2013 Elsevier Ltd. All rights reserved.

Transparent conductive Ga-doped ZnO films fabricated by MOCVD

Energy Technology Data Exchange (ETDEWEB)

Behrends, Arne; Wagner, Alexander; Al-Suleiman, Mohamed Aid Mansur; Waag, Andreas; Bakin, Andrey [Institute of Semiconductor Technology, University of Technology Braunschweig, Hans-Sommer-Str. 66, 38106 Braunschweig (Germany); Lugauer, Hans-Juergen; Strassburg, Martin; Walter, Robert; Weimar, Andreas [OSRAM Opto Semiconductors GmbH, Leibnizstr. 4, 93055 Regensburg (Germany)

2012-04-15

Transparent conductive oxides (TCOs) are used for a variety of different applications, e.g., in solar cells and light emitting diodes (LEDs). Mostly, sputtering is used, which often results in a degradation of the underlying semiconductor material. In this work we report on a ''soft'' method for the fabrication of ZnO films as TCO layers by using metal organic chemical vapor deposition (MOCVD) at particularly low temperatures. The MOCVD approach has been studied focusing on the TCO key issues: fabrication temperature, morphology, optical, and electrical properties. Very smooth ZnO films with rms values down to 0.8 nm were fabricated at a substrate temperature of only 300 C. Ga-doping is well controllable even for high carrier concentrations up to 2 x 10{sup 20} cm{sup -3}, which is above the Mott-density leading to metallic-like behavior of the films. Furthermore all films show excellent optical transparency in the visible spectral range. As a consequence, our MOCVD approach is well suited for the soft fabrication of ZnO-based TCO layers. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Preparation and photocatalytic activity of B, Y co-doped nanosized TiO_2 catalyst

Institute of Scientific and Technical Information of China (English)

石中亮; 刘富梅; 姚淑华

2010-01-01

The catalysts of un-doped, single-doped and co-doped titanium dioxide (TiO2) powders were prepared by sol-gel method with Ti(OC4H9)4 as a raw material. The photocatalytic decomposition of phenol in aqueous solution under UV light was used as a probe reaction to evaluate their photocatalytic activities. The effects of B, Y co-doping on the crystallite sizes, crystal pattern, surface composition, and optical property of the catalyst were investigated by thermogravimetric differential thermal analysis, X-ray d...

Effect of heavy Ag doping on the physical properties of ZnO

Science.gov (United States)

Hou, Qingyu; Zhao, Chunwang; Jia, Xiaofang; Xu, Zhenchao

2018-04-01

The band structure, density of state and absorption spectrum of Zn1‑xAgxO (x = 0.02778, 0.04167) were calculated. Results indicated that a higher doping content of Ag led to a higher total energy, lower stability, higher formation energy, narrower bandgap, more significant red shift of the absorption spectrum, higher relative concentration of free hole, smaller hole effective mass, lower mobility and better conductivity. Furthermore, four types of model with the same doping content of double Ag-doped Zn1‑xAgxO (x = 0.125) but different manners of doping were established. Two types of models with different doping contents of double Ag-doped Zn1‑xAgxO (x = 0.0626, 0.0833) but the same manner of doping, were also established. Under the same doping content and different ordering occupations in Ag double doping, the doped system almost caused magnetic quenching upon the nearest neighbor -Ag-O-Ag- bonding at the direction partial to the a- or b-axis. Upon the next-nearest neighbor of -Ag-O-Zn-O-Ag- bonding at the direction partial to the c-axis, the total magnetic moment of the doped system increased, and the doped system reached a Curie temperature above the room-temperature. All these results indicated that the magnetic moments of Ag double-doped ZnO systems decreased with increased Ag doping content. Within the range of the mole number of the doping content of 0.02778-0.04167, a greater Ag doping content led to a narrower bandgap of the doped system and a more significant red shift in the absorption spectrum. The absorption spectrum of the doped ZnO system with interstitial Ag also shows a red shift.

Photoluminescence study of novel phosphorus-doped ZnO nanotetrapods synthesized by chemical vapour deposition

International Nuclear Information System (INIS)

Yu Dongqi; Hu Lizhong; Qiao Shuangshuang; Zhang Heqiu; Fu Qiang; Chen Xi; Sun Kaitong; Len, Song-En Andy; Len, L K

2009-01-01

Novel phosphorus-doped and undoped single crystal ZnO nanotetrapods were fabricated on sapphire by a simple chemical vapour deposition method, using phosphorus pentoxide (P 2 O 5 ) as the dopant source. The optical properties of the samples were investigated by photoluminescence (PL) spectroscopy. Low-temperature PL measurements of phosphorus-doped and undoped samples were compared, and the results indicated a decrease in deep level defects due to the incorporation of a phosphorus acceptor dopant. The PL spectrum of the phosphorus-doped sample at 10 K exhibited several acceptor-bound exciton related emission peaks. The effect of phosphorus doping on the optical characteristics of the samples was investigated by excitation intensity and temperature dependent PL spectra. The acceptor-binding energies of the phosphorus dopant were estimated to be about 120 meV, in good agreement with the corresponding theoretical and experimental values in phosphorus-doped ZnO films and nanowires.

The structural, electrical and optical properties of Mg-doped ZnO with different interstitial Mg concentration

Energy Technology Data Exchange (ETDEWEB)

Hu, Yonghong, E-mail: hchyh@njust.edu.cn [School of Nuclear Technology and Chemistry & Biology, Hubei University of Science and Technology, Xianning 437100 (China); Institute of Optoelectronics & Nanomaterials, College of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Zeng, Haibo [Institute of Optoelectronics & Nanomaterials, College of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Du, Jifu [School of Nuclear Technology and Chemistry & Biology, Hubei University of Science and Technology, Xianning 437100 (China); Hu, Ziyu [Beijing Computational Science Research Center, Beijing 100084 (China); Zhang, Shengli [Institute of Optoelectronics & Nanomaterials, College of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China)

2016-10-01

Through first principle calculations, we studied the structural, electronic and optical properties of ZnO doped by interstitial Mg. With the increase of Mg content (x), the derivations of lattice parameters from the wurtzite ZnO become more and more significant. The Mg-doped ZnO with x below 15.79% is found to be n-type semiconductor. The minimum of energy band gap and light transmittance in high energy region (7.5–25 eV) decrease while the conductivity and refractive index increase with increasing x. Further increasing x up to 20%, the Mg-doped ZnO is found to be direct-band-gap semiconductor with great structural derivation from wurtzite phase. The light transmittance increases while the refractive index decreases with the increase of x due to the change of geometry and electronic structure. So, it’s concluded that the electronic and optical properties of ZnO doped by interstitial Mg may be greatly influenced by Mg content. - Graphical abstract: The minimum of energy gap decreases while the corresponding relative number of electrons into the conduction bands increases when the interstitial Mg content x in Mg-doped ZnO increases (0 ≤ x ≤ 15.79%). - Highlights: • The energy band gap decreases with the increase of interstitial Mg content from 5.88% to 15.79%. • The conductivity increases with the increase of interstitial Mg content from 5.88% to 15.79%. • The Mg{sub x}Zn{sub 1-x}O (interstitial Mg content x= 20%) is found to be a direct-band-gap semiconductor. • The light transmittance decreases with the increase of interstitial Mg content from 5.88% to 15.79%. • The refractive index increases with the increase of interstitial Mg content from 5.88% to 15.79%.

Fabrication and Characterization of Highly Oriented N-Doped ZnO Nanorods by Selective Area Epitaxy

Directory of Open Access Journals (Sweden)

Yang Zhang

2015-01-01

Full Text Available High-quality nitrogen-doped ZnO nanorods have been selectively grown on patterned and bare ZnO templates by the combination of nanoimprint lithography and chemical vapor transport methods. The grown nanorods exhibited uniformity in size and orientation as well as controllable density and surface-to-volume ratio. The structural and optical properties of ZnO nanorods and the behaviour of N dopants have been investigated by means of the scanning electron microscope, photoluminescence (PL spectra, and Raman scattering spectra. The additional vibration modes observed in Raman spectra of N-doped ZnO nanorods provided solid evidence of N incorporation in ZnO nanorods. The difference of excitonic emissions from ZnO nanorods with varied density and surface-to-volume ratio suggested the different spatial distribution of intrinsic defects. It was found that the defects giving rise to acceptor-bound exciton (A0X emission were most likely to distribute in the sidewall surface with nonpolar characteristics, while the donor bound exciton (D0X emission related defects distributed uniformly in the near top polar surface.

Inhibition of growth of S. epidermidis by hydrothermally synthesized ZnO nanoplates

Science.gov (United States)

Abinaya, C.; Mayandi, J.; Osborne, J.; Frost, M.; Ekstrum, C.; Pearce, J. M.

2017-07-01

The antibacterial effect of zinc oxide (ZnO#1) as prepared and annealed (ZnO#2) at 400 °C, Cu doped ZnO (CuZnO), and Ag doped ZnO (AgZnO) nanoplates on Staphylococcus epidermidis was investigated for the inhibition and inactivation of cell growth. The results shows that pure ZnO and doped ZnO samples exhibited antibacterial activity against Staphylococcus epidermidis (S. epidermidis) as compared to tryptic soy broth (TSB). Also it is observed that S. epidermidis was extremely sensitive to treatment with ZnO nanoplates and it is clear that the effect is not purely depend on Cu/Ag. Phase identification of a crystalline material and unit cell dimensions were studied by x-ray powder diffraction (XRD). The scanning electron microscopy (SEM) provides information on sample’s surface topography and the EDX confirms the presence of Zn, O, Cu and Ag. X-ray photo-electron spectroscopy (XPS) was used to analyze the elemental composition and electronic state of the elements that exist within the samples. These studies confirms the formation of nanoplates and the presence of Zn, O, Ag, Cu with the oxidation states  +2, -2, 0 and  +2 respectively. These results indicates promising antibacterial applications of these ZnO-based nanoparticles synthesized with low-cost hydrothermal methods.

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.

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.

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.

Cation vacancies and electrical compensation in Sb-doped thin-film SnO2 and ZnO

International Nuclear Information System (INIS)

Korhonen, E; Prozheeva, V; Tuomisto, F; Bierwagen, O; Speck, J S; White, M E; Galazka, Z; Liu, H; Izyumskaya, N; Avrutin, V; Özgür, Ü; Morkoç, H

2015-01-01

We present positron annihilation results on Sb-doped SnO 2 and ZnO thin films. The vacancy types and the effect of vacancies on the electrical properties of these intrinsically n-type transparent semiconducting oxides are studied. We find that in both materials low and moderate Sb-doping leads to formation of vacancy clusters of variable sizes. However, at high doping levels cation vacancy defects dominate the positron annihilation signal. These defects, when at sufficient concentrations, can efficiently compensate the n-type doping produced by Sb. This is the case in ZnO, but in SnO 2 the concentrations appear too low to cause significant compensation. (invited article)

Cation vacancies and electrical compensation in Sb-doped thin-film SnO2 and ZnO

Science.gov (United States)

Korhonen, E.; Prozheeva, V.; Tuomisto, F.; Bierwagen, O.; Speck, J. S.; White, M. E.; Galazka, Z.; Liu, H.; Izyumskaya, N.; Avrutin, V.; Özgür, Ü.; Morkoç, H.

2015-02-01

We present positron annihilation results on Sb-doped SnO2 and ZnO thin films. The vacancy types and the effect of vacancies on the electrical properties of these intrinsically n-type transparent semiconducting oxides are studied. We find that in both materials low and moderate Sb-doping leads to formation of vacancy clusters of variable sizes. However, at high doping levels cation vacancy defects dominate the positron annihilation signal. These defects, when at sufficient concentrations, can efficiently compensate the n-type doping produced by Sb. This is the case in ZnO, but in SnO2 the concentrations appear too low to cause significant compensation.

p-type ZnO films with solid-source phosphorus doping by molecular-beam epitaxy

International Nuclear Information System (INIS)

Xiu, F.X.; Yang, Z.; Mandalapu, L.J.; Liu, J.L.; Beyermann, W. P.

2006-01-01

Phosphorus-doped p-type ZnO films were grown on r-plane sapphire substrates using molecular-beam epitaxy with a solid-source GaP effusion cell. X-ray diffraction spectra and reflection high-energy electron diffraction patterns indicate that high-quality single crystalline (1120) ZnO films were obtained. Hall and resistivity measurements show that the phosphorus-doped ZnO films have high hole concentrations and low resistivities at room temperature. Photoluminescence (PL) measurements at 8 K reveal a dominant acceptor-bound exciton emission with an energy of 3.317 eV. The acceptor energy level of the phosphorus dopant is estimated to be 0.18 eV above the valence band from PL spectra, which is also consistent with the temperature dependence of PL measurements

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

International Nuclear Information System (INIS)

Fujimoto, Yutaka; Yanagida, Takayuki; Yokota, Yuui; Chani, Valery; Yoshikawa, Akira; Sekiwa, Hideyuki

2011-01-01

The present study describes the first detailed evaluation of the rise and the decay time of scintillation phenomenon in In 3+ - and Ga 3+ -doped ZnO thin films with different dopant concentrations. In 3+ -(25, 55, and 141 ppm) and Ga 3+ -(33, 67, 333, and 1374 ppm) doped ZnO films were grown by the Liquid Phase Epitaxy (LPE) method. The characterization was performed using the pulse X-ray equipped streak camera system. Both the rise and the decay times were shortened considerably with increasing content of In 3+ and Ga 3+ in the films. However, the scintillation light yield under 241 Am α-ray excitation reduced when concentration of In 3+ and Ga 3+ in the ZnO films was high. (author)

Structural and room temperature ferromagnetic properties of Ni doped ZnO nanoparticles via low-temperature hydrothermal method

Energy Technology Data Exchange (ETDEWEB)

Xu, Kun; Liu, Changzhen, E-mail: liuchangzhen94@163.com; Chen, Rui; Fang, Xiaoxiang; Wu, Xiuling; Liu, Jie

2016-12-01

A series of Zn{sub 1−x}Ni{sub x}O (x=0, 1%, 3%, 5%) nanoparticles have been synthesized via a low-temperature hydrothermal method. Influence of Ni doping concentration on the structure, morphology, optical properties and magnetism of the samples was investigated by means of X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, UV–vis spectrophotometer and vibrating sample magnetometer instruments. The results show that the undoped and doped ZnO nanoparticles are both hexagonal wurtzite structures. The surface analysis was performed using X-ray photoelectron spectroscopic studies. The images of SEM reveal that the structure of pure ZnO and Ni doped samples are nanoparticles which intended to form flakes with thickness of few nanometers, being overlain with each one to develop the network with some pores and voids. Based on the ultraviolet–visible (UV–vis) spectroscopy analysis, it indicates that the band gap energy decreases with the increasing concentration of Ni. Furthermore, The Ni doped ZnO samples didn't exhibit higher ultraviolet-light-driven photocatalytic activity compared to the undoped ZnO sample. Vibrating sample magnetometer was used for the magnetic property investigations, and the result indicates that room temperature ferromagnetism property of 3% Ni doped sample is attributed to oxygen vacancy and interaction between doped ions.

The effects of ZnO buffer layers on the properties of phosphorus doped ZnO thin films grown on sapphire by pulsed laser deposition

International Nuclear Information System (INIS)

Kim, K-W; Lugo, F J; Lee, J H; Norton, D P

2012-01-01

The properties of phosphorus doped ZnO thin films grown on sapphire by pulsed laser deposition were examined, specifically focusing on the effects of undoped ZnO buffer layers. In particular, buffer layers were grown under different conditions; the transport properties of as-deposited and rapid thermal annealed ZnO:P films were then examined. As-deposited films showed n-type conductivity. After rapid thermal annealing, the film on buffer layer grown at a low temperature showed the conversion of carrier type to p-type for specific growth conditions while the films deposited on buffer layer grown at a high temperature remained n-type regardless of growth condition. The films deposited on buffer layer grown at a low temperature showed higher resistivity and more significant change of the transport properties upon rapid thermal annealing. These results suggest that more dopants are incorporated in films with higher defect density. This is consistent with high resolution x-ray diffraction results for phosphorus doped ZnO films on different buffer layers. In addition, the microstructure of phosphorus doped ZnO films is substantially affected by the buffer layer.

Synthesis of Mn doped ZnO nanoparticles with biocompatible capping

International Nuclear Information System (INIS)

Sharda; Jayanthi, K.; Chawla, Santa

2010-01-01

Free standing nanoparticles of ZnO doped with transition metal ion Mn have been prepared by solid state reaction method at 500 deg. C. X-ray diffraction (XRD) analysis confirmed high quality monophasic wurtzite hexagonal structure with particle size of 50 nm and no signature of dopant as separate phase. Incorporation of Mn has been confirmed with EDS. Bio-inorganic interface was created by capping the nanoparticles with heteromultifunctional organic stabilizer mercaptosuccinic acid (MSA). The surface morphological studies by scanning electron microscopy (SEM) showed formation of spherical particles and the nanoballs grow in size uniformly with MSA capping. MSA capping has been confirmed with thermo gravimetric analysis (TGA) and FTIR. Photoluminescence (PL) studies show that the ZnO:Mn 2+ particles are excitable by blue light and emits in orange and red. Occurrence of room temperature ferromagnetism in Mn doped ZnO makes such biocompatible luminescent magnetic nanoparticles very promising material.

Green method for producing hierarchically assembled pristine porous ZnO nanoparticles with narrow particle size distribution

International Nuclear Information System (INIS)

Escobedo-Morales, A.; Téllez-Flores, D.; Ruiz Peralta, Ma. de Lourdes; Garcia-Serrano, J.; Herrera-González, Ana M.; Rubio-Rosas, E.; Sánchez-Mora, E.; Olivares Xometl, O.

2015-01-01

A green method for producing pristine porous ZnO nanoparticles with narrow particle size distribution is reported. This method consists in synthesizing ZnO 2 nanopowders via a hydrothermal route using cheap and non-toxic reagents, and its subsequent thermal decomposition at low temperature under a non-protective atmosphere (air). The morphology, structural and optical properties of the obtained porous ZnO nanoparticles were studied by means of powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and nitrogen adsorption–desorption measurements. It was found that after thermal decomposition of the ZnO 2 powders, pristine ZnO nanoparticles are obtained. These particles are round-shaped with narrow size distribution. A further analysis of the obtained ZnO nanoparticles reveals that they are hierarchical self-assemblies of primary ZnO particles. The agglomeration of these primary particles at the very early stage of the thermal decomposition of ZnO 2 powders provides to the resulting ZnO nanoparticles a porous nature. The possibility of using the synthesized porous ZnO nanoparticles as photocatalysts has been evaluated on the degradation of rhodamine B dye. - Highlights: • A green synthesis method for obtaining porous ZnO nanoparticles is reported. • The obtained ZnO nanoparticles have narrow particle size distribution. • This method allows obtaining pristine ZnO nanoparticles avoiding unintentional doping. • A growth mechanism for the obtained porous ZnO nanoparticles is proposed

Red luminescence from hydrothermally synthesized Eu-doped ZnO ...

Indian Academy of Sciences (India)

Administrator

turally characterized by X-ray diffraction, transmission electron microscopy ... II–VI compound semiconductor with large exciton binding .... ions occupy a site with inversion symmetry and 617 nm ... TEM image of Eu-doped ZnO nanoparticles with (a) 1⋅2 at. .... Jacquier B, Lebrasseur E, Guy S, Belarouci A and Menchini F.

Photocatalytic activity of ZnO doped with Ag on the degradation of endocrine disrupting under UV irradiation and the investigation of its antibacterial activity

Energy Technology Data Exchange (ETDEWEB)

Bechambi, Olfa [Université de Tunis El Manar, Faculté des Sciences de Tunis, Laboratoire de Chimie des Matériaux et Catalyse, 2092, Tunis (Tunisia); Chalbi, Manel [Laboratoire de Bioprocédés Environnementaux, Centre de Biotechnologie de Sfax, B.P. 1177, 3018 Sfax (Tunisia); Najjar, Wahiba, E-mail: najjarwahiba2014@gmail.com [Université de Tunis El Manar, Faculté des Sciences de Tunis, Laboratoire de Chimie des Matériaux et Catalyse, 2092, Tunis (Tunisia); Sayadi, Sami [Laboratoire de Bioprocédés Environnementaux, Centre de Biotechnologie de Sfax, B.P. 1177, 3018 Sfax (Tunisia)

2015-08-30

Graphical abstract: - Highlights: • A series of Ag-doped ZnO were synthesized via hydrothermal method. • Effect of doping with silver on the textural, structural optical properties of ZnO. • The photocatalytic activity has been tested using bisphenol A and nonylphenol. • The highest degradation efficiency was obtained with 1% Ag. • Ag doping enhances the photocatalytic and antibacterial activities of ZnO. - Abstract: Ag-doped ZnO photocatalysts with different Ag molar content (0.0, 0.5, 1.0, 2.0 and 4.0%) were prepared via hydrothermal method. The X-ray diffraction (XRD), Nitrogen physisorption at 77 K, Fourier transformed infrared spectroscopy (FTIR), UV–-Visible spectroscopy, Photoluminescence spectra (PL) and Raman spectroscopy were used to characterize the structural, textural and optical properties of the samples. The results showed that Ag-doping does not change the average crystallite size with the Ag low content (≤1.0%) but slightly decreases with Ag high content (>1.0%). The specific surface area (S{sub BET}) increases with the increase of the Ag content. The band gap values of ZnO are decreased with the increase of the Ag doping level. The results of the photocatalytic degradation of bisphenol A (BPA) and nonylphenol (NP) in aqueous solutions under UV irradiation and in the presence of hydrogen peroxide (H{sub 2}O{sub 2}) showed that silver ions doping greatly improved the photocatalytic efficiency of ZnO. The TOC conversion BPA and NP are 72.1% and 81.08% respectively obtained using 1% Ag-doped ZnO. The enhancement of photocatalytic activity is ascribed to the fact that the modification of ZnO with an appropriate amount of Ag can increase the separation efficiency of the photogenerated electrons-holes in ZnO. The antibacterial activity of the catalysts which uses Escherichia coli as a model for Gram-negative bacteria confirmed that Ag-doped ZnO possessed more antibacterial activity than the pure ZnO.

Photocatalytic activity of ZnO doped with Ag on the degradation of endocrine disrupting under UV irradiation and the investigation of its antibacterial activity

International Nuclear Information System (INIS)

Bechambi, Olfa; Chalbi, Manel; Najjar, Wahiba; Sayadi, Sami

2015-01-01

Graphical abstract: - Highlights: • A series of Ag-doped ZnO were synthesized via hydrothermal method. • Effect of doping with silver on the textural, structural optical properties of ZnO. • The photocatalytic activity has been tested using bisphenol A and nonylphenol. • The highest degradation efficiency was obtained with 1% Ag. • Ag doping enhances the photocatalytic and antibacterial activities of ZnO. - Abstract: Ag-doped ZnO photocatalysts with different Ag molar content (0.0, 0.5, 1.0, 2.0 and 4.0%) were prepared via hydrothermal method. The X-ray diffraction (XRD), Nitrogen physisorption at 77 K, Fourier transformed infrared spectroscopy (FTIR), UV–-Visible spectroscopy, Photoluminescence spectra (PL) and Raman spectroscopy were used to characterize the structural, textural and optical properties of the samples. The results showed that Ag-doping does not change the average crystallite size with the Ag low content (≤1.0%) but slightly decreases with Ag high content (>1.0%). The specific surface area (S BET ) increases with the increase of the Ag content. The band gap values of ZnO are decreased with the increase of the Ag doping level. The results of the photocatalytic degradation of bisphenol A (BPA) and nonylphenol (NP) in aqueous solutions under UV irradiation and in the presence of hydrogen peroxide (H 2 O 2 ) showed that silver ions doping greatly improved the photocatalytic efficiency of ZnO. The TOC conversion BPA and NP are 72.1% and 81.08% respectively obtained using 1% Ag-doped ZnO. The enhancement of photocatalytic activity is ascribed to the fact that the modification of ZnO with an appropriate amount of Ag can increase the separation efficiency of the photogenerated electrons-holes in ZnO. The antibacterial activity of the catalysts which uses Escherichia coli as a model for Gram-negative bacteria confirmed that Ag-doped ZnO possessed more antibacterial activity than the pure ZnO

ZnO and Al doped ZnO thin films deposited by Spray Plasma: Effect of the growth time and Al doping on microstructural, optical and electrical properties

International Nuclear Information System (INIS)

Baba, Kamal; Lazzaroni, Claudia; Nikravech, Mehrdad

2015-01-01

Nanostructured zinc oxide (ZnO) and Al doped ZnO (ZnO:Al) thin films are deposited on glass substrate by the Spray Plasma technique. Zinc nitrate and aluminium nitrate are used as Zn and Al precursors, respectively. The effect of the growth time on structural and optical properties of undoped films is studied by X-ray diffraction, atomic force microscopy, and UV–Vis spectroscopy. The effect of Al doping on microstructural, optical and electrical characteristics of ZnO:Al films is also investigated. The results show that the grain size and the film thickness both increase with the growth time. The band gap of the layers varies from 3.17 to 3.24 eV depending on the thickness. The increase of the Al doping results in the enlargement of the peak (002) and the shift of its position to higher 2θ values. Average optical transmittance decreases from 90 to 65% with the growth time because of the thickness increase while there is no significant influence of the aluminium doping on the transmittance which is above 80% in most of the visible and near-IR range for all ZnO:Al films. The electrical properties characterized by Hall measurements show that all the deposited films exhibit high resistivity, between 4 and 10 4 Ω cm. The carrier concentration decreases from 2.10 19 to 2.10 13 cm −3 when the concentration of Al increases from 1.5 to 5 atm%. - Highlights: • The original Spray Plasma technique is used for ZnO and ZnO:Al thin film deposition. • Investigation of the effect of growth time and Al doping on the structural and optical properties • Increase of grain size and film thickness with the growth time • Optical transmittance decreases from 90 to 65% with the growth time and is above 80% for ZnO:Al films in UV–Vis-NIR range. • The peak position of the (002) plane is shifted to high 2θ values with Al doping.

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

C, N co-doped TiO_2/TiC_0_._7N_0_._3 composite coatings prepared from TiC_0_._7N_0_._3 powder using ball milling followed by oxidation

International Nuclear Information System (INIS)

Hao, Liang; Wang, Zhenwei; Zheng, Yaoqing; Li, Qianqian; Guan, Sujun; Zhao, Qian; Cheng, Lijun; Lu, Yun; Liu, Jizi

2017-01-01

Highlights: • TiO_2/TiC_0_._7N_0_._3 coatings were prepared by ball milling followed by oxidation. • In situ co-doping of C and N with simultaneous TiO_2 formation was observed. • Improved photocatalytic activity under UV/visible light was noticed. • Synergism in co-doping and heterojunction formation promoted carrier separation. - Abstract: Ball milling followed by heat oxidation was used to prepared C, N co-doped TiO_2 coatings on the surfaces of Al_2O_3 balls from TiC_0_._7N_0_._3 powder. The as-prepared coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible spectrophotometer (UV–vis). The results show that continuous TiC_0_._7N_0_._3 coatings were formed after ball milling. C, N co-doped TiO_2/TiC_0_._7N_0_._3 composite coatings were prepared after the direct oxidization of TiC_0_._7N_0_._3 coatings in the atmosphere. However, TiO_2 was hardly formed in the surface layer of TiC_0_._7N_0_._3 coatings within a depth less than 10 nm during the heat oxidation of TiC_0_._7N_0_._3 coatings in carbon powder. Meanwhile, the photocatalytic activity evaluation of these coatings was conducted under the irradiation of UV and visible light. All the coatings showed photocatalytic activity in the degradation of MB no matter under the irradiation of UV or visible light. The C, N co-doped TiO_2/TiC_0_._7N_0_._3 composite coatings showed the most excellent performance. The enhancement under visible light irradiation should attribute to the co-doping of carbon and nitrogen, which enhances the absorption of visible light. The improvement of photocatalytic activity under UV irradiation should attribute to the synergistic effect of C, N co-doping, the formation of rutile-anatase mixed phases and the TiO_2/TiC_0_._7N_0_._3 composite microstructure.

Tuning the nanostructures and optical properties of undoped and N-doped ZnO by supercritical fluid treatment

Science.gov (United States)

Li, Yaping; Wang, Hui-Qiong; Chu, Tian-Jian; Li, Yu-Chiuan; Li, Xiaojun; Liao, Xiaxia; Wang, Xiaodan; Zhou, Hua; Kang, Junyong; Chang, Kuan-Chang; Chang, Ting-Chang; Tsai, Tsung-Ming; Zheng, Jin-Cheng

2018-05-01

Treatment of ZnO films in a supercritical fluid (SCF) has been reported to improve the performance of devices in which the treated ZnO films are incorporated; however, the mechanism of this improvement remains unclear. In this paper, we study the transformation of the surface morphologies and emission properties of ZnO films before and after SCF treatment, establishing the relationship between the treated and untreated structures and thereby enabling tuning of the catalytic or opto-electronic performance of ZnO films or ZnO-film-based devices. Both undoped and N-doped ZnO nanostructures generated by SCF treatment of films are investigated using techniques to characterize their surface morphology (scanning electron microscopy (SEM) and atomic force microscopy (AFM)) as well as room-temperature photoluminescence (RT-PL) spectroscopy. The water-mixed supercritical CO2 (W-SCCO2) technology was found to form nanostructures in ZnO films through a self-catalyzed process enabled by the Zn-rich conditions in the ZnO films. The W-SCCO2 was also found to promote the inhibition of defect luminescence by introducing -OH groups onto the films. Two models are proposed to explain the effects of the treatment with W-SCCO2. This work demonstrates that the W-SCCO2 technology can be used as an effective tool for the nanodesign and property enhancement of functional metal oxides.

Boron-doped MnTe semiconductor-sensitized ZnO solar cells

Indian Academy of Sciences (India)

Administrator

The B-doped MnTe semiconductor was grown on ZnO using two stages of the ... nanoparticles (NPs), i.e. MnTe and MnTe2 were observed with a diameter range of approximately ..... Kongkanand A, Tvrdy K, Takechi K, Kuno M and Kamat P.