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Sample records for zno layers grown

  1. Luminescence properties of ZnO layers grown on Si-on-insulator substrates

    International Nuclear Information System (INIS)

    Kumar, Bhupendra; Gong, Hao; Vicknesh, S.; Chua, S. J.; Tripathy, S.

    2006-01-01

    The authors report on the photoluminescence properties of polycrystalline ZnO thin films grown on compliant silicon-on-insulator (SOI) substrates by radio frequency magnetron sputtering. The ZnO thin films on SOI were characterized by micro-Raman and photoluminescence (PL) spectroscopy. The observation of E 2 high optical phonon mode near 438 cm -1 in the Raman spectra of the ZnO samples represents the wurtzite crystal structure. Apart from the near-band-edge free exciton (FX) transition around 3.35 eV at 77 K, the PL spectra of such ZnO films also showed a strong defect-induced violet emission peak in the range of 3.05-3.09 eV. Realization of such ZnO layers on SOI would be useful for heterointegration with SOI-based microelectronics and microelectromechanical systems

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

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    Shao-Ying Ting

    2012-01-01

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

  3. Growth and characterization of polar and nonpolar ZnO film grown on sapphire substrates by using atomic layer deposition

    International Nuclear Information System (INIS)

    Kim, Ki-Wook; Son, Hyo-Soo; Choi, Nak-Jung; Kim, Jihoon; Lee, Sung-Nam

    2013-01-01

    We investigated the electrical and the optical properties of polar and nonpolar ZnO films grown on sapphire substrates with different crystallographic planes. High resolution X-ray results revealed that polar c-plane (0001), nonpolar m-plane (10-10) and a-plane (11-20) ZnO thin films were grown on c-plane, m- and r-sapphire substrates by atomic layer deposition, respectively. Compared with the c-plane ZnO film, nonpolar m-plane and a-plane ZnO films showed smaller surface roughness and anisotropic surface structures. Regardless of ZnO crystal planes, room temperature photoluminescence spectra represented two emissions which consisted of the near bandedge (∼ 380 nm) and the deep level emission (∼ 500 nm). The a-plane ZnO films represented better optical and electrical properties than c-plane ZnO, while m-plane ZnO films exhibited poorer optical and electrical properties than c-plane ZnO. - Highlights: • Growth and characterization of a-, c- and m-plane ZnO film by atomic layer deposition. • The a-plane ZnO represented better optical and electrical properties than c-plane ZnO. • The m-plane ZnO exhibited poorer optical and electrical properties than c-plane ZnO

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

    International Nuclear Information System (INIS)

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

    2012-01-01

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

  5. Surface potential driven dissolution phenomena of [0 0 0 1]-oriented ZnO nanorods grown from ZnO and Pt seed layers

    Science.gov (United States)

    Seo, Youngmi; Kim, Jung Hyeun

    2011-06-01

    Highly oriented ZnO nanorods are synthesized hydrothermally on ZnO and Pt seed layers, and they are dissolved in KOH solution. The rods grown on ZnO seed layer show uniform dissolution, but those grown on Pt seed layer are rod-selectively dissolved. The ZnO nanorods from both seed layers show the same crystalline structure through XRD and Raman spectrometer data. However, the surface potential analysis reveals big difference for ZnO and Pt seed cases. The surface potential distribution is very uniform for the ZnO seed case, but it is much fluctuated on the Pt seed case. It suggests that the rod-selective dissolution phenomena on Pt seed case are likely due to the surface energy difference.

  6. Effects of ZnO Seed Layers Prepared with Various Precursor Concentrations on Structural and Defect Emission Properties of ZnO Nanorods Grown by Hydrothermal Method

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    Kim, Soaram; Nam, Giwoong; Leem, Jae-Young; Kim, Yangsoo [Inje University, Gimhae (Korea, Republic of); Kim, Ghun Sik; Yoon, Sung Pil [Korea Institute of Science and Technology, Seoul (Korea, Republic of)

    2013-07-15

    ZnO nanorods were grown by a hydrothermal method on ZnO seed layers that had previously been prepared from solutions containing various precursor concentrations. The effects of the ZnO seed layers prepared with various precursor concentrations on the structural and defect emissions of the ZnO nanorods were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) spectroscopy. The surface morphology of the ZnO seed layers changed with an increasing precursor concentration, and the diameters and densities of the ZnO nanorods depended on the morphologies of the ZnO seed layers. The ZnO seed layers prepared with various precursor concentrations affected the residual stress in the nanorods grown on the seed layers, the intensity and full widths at half maximum of the 2-theta angle in the XRD spectra for the nanorods, and the intensity and position of the defect emission peak in deep-level emission (DLE) PL spectra for the ZnO nanorods.

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

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

    2009-07-30

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

  8. Effects of buffer layer annealing temperature on the structural and optical properties of hydrothermal grown ZnO

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    Zhao, X.Q.; Kim, C.R.; Lee, J.Y.; Heo, J.H.; Shin, C.M. [Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Obang-dong, Gimhae, Gyeongnam 621-749 (Korea, Republic of); Ryu, H., E-mail: hhryu@inje.ac.kr [Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Obang-dong, Gimhae, Gyeongnam 621-749 (Korea, Republic of); Chang, J.H. [Major of Nano Semiconductor, Korea Maritime University, 1 Dongsam-dong, Yeongdo-Ku, Busan 606-791 (Korea, Republic of); Lee, H.C. [Department of Mechatronics Engineering, Korea Maritime University, 1 Dongsam-dong, Yeongdo-Ku, Busan 606-791 (Korea, Republic of); Son, C.S. [Department of Electronic Materials Engineering, Silla University, Gwaebeop-dong, Sasang-gu, Busan 617-736 (Korea, Republic of); Lee, W.J. [Department of Nano Engineering, Dong-Eui University, 995 Eomgwangno, Busanjin-gu, Busan 614-714 (Korea, Republic of); Jung, W.G. [School of Advanced Materials Engineering, Kookmin University, 861-1 Jeongneung-dong, Seongbuk-gu, Seoul 136-702 (Korea, Republic of); Tan, S.T. [Institute of Microelectronics, 11 Science Park Road, Science Park II, Singapore 117685 (Singapore); Zhao, J.L. [School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore); Sun, X.W. [Institute of Microelectronics, 11 Science Park Road, Science Park II, Singapore 117685 (Singapore); School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore)

    2009-02-01

    ZnO was deposited on bare Si(1 0 0), as-deposited, and annealed ZnO/Si(1 0 0) substrates by hydrothermal synthesis. The effects of a ZnO buffer layer and its thermal annealing on the properties of the ZnO deposited by hydrothermal synthesis were studied. The grain size and root mean square (RMS) roughness values of the ZnO buffer layer increased after thermal annealing of the buffer layer. The effect of buffer layer annealing temperature on the structural and optical properties was investigated by photoluminescence, X-ray diffraction, atomic force microscopy, and scanning electron microscopy. Hydrothermal grown ZnO deposited on ZnO/Si(1 0 0) annealed at 750 deg. C with the concentration of 0.3 M exhibits the best structural and optical properties.

  9. 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.

  10. Influence of seed layer treatment on low temperature grown ZnO nanotubes: Performances in dye sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Ameen, Sadia [Energy Materials and Surface Science Laboratory, Solar Energy Research Center, School of Chemical Engineering, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Akhtar, M. Shaheer [School of Semiconductor and Chemical Engineering and Solar Energy Research Center, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); New and Renewable Energy Material Development Center (NewREC), Chonbuk National University, Buan-gun, Jeonbuk (Korea, Republic of); Kim, Young Soon [Energy Materials and Surface Science Laboratory, Solar Energy Research Center, School of Chemical Engineering, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Yang, O-Bong [School of Semiconductor and Chemical Engineering and Solar Energy Research Center, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Shin, Hyung-Shik, E-mail: hsshin@jbnu.ac.k [Energy Materials and Surface Science Laboratory, Solar Energy Research Center, School of Chemical Engineering, Chonbuk National University, Jeonju 561-756 (Korea, Republic of)

    2011-01-01

    Non-aligned and highly densely aligned ZnO nanotube (NTs), synthesized by low temperature solution method were applied as photoanode materials for the fabrication of efficient dye-sensitized solar cells (DSSCs). The crystalline and the morphological analysis revealed that the grown aligned ZnO NTs possessed a typical hexagonal crystal structure of outer and inner diameter {approx}250 nm and {approx}100 nm, respectively. ZnO seeding on FTO substrates is an essential step to achieve the aligned ZnO NTs. A DSSC fabricated with aligned ZnO NTs photoanode achieved high solar-to-electricity conversion efficiency of {approx}2.2% with short circuit current (J{sub SC}) of 5.5 mA/cm{sup 2}, open circuit voltage (V{sub OC}) of 0.65 V and fill factor (FF) of 0.61. Significantly, the aligned ZnO NTs photoanode showed three times improved solar-to-electricity conversion efficiency than DSSC fabricated with non-aligned ZnO NTs. The enhanced performances were credited to the aligned morphology of ZnO NTs which executed the high charge collection and the transfer of electrons at the interfaces of ZnO NTs and electrolyte layer.

  11. ZnO nanostructures directly grown on paper and bacterial cellulose substrates without any surface modification layer.

    Science.gov (United States)

    Costa, Saionara V; Gonçalves, Agnaldo S; Zaguete, Maria A; Mazon, Talita; Nogueira, Ana F

    2013-09-21

    In this report, hierarchical ZnO nano- and microstructures were directly grown for the first time on a bacterial cellulose substrate and on two additional different papers by hydrothermal synthesis without any surface modification layer. Compactness and smoothness of the substrates are two important parameters that allow the growth of oriented structures.

  12. A Comparative Study on Structural and Optical Properties of ZnO Micro-Nanorod Arrays Grown on Seed Layers Using Chemical Bath Deposition and Spin Coating Methods

    Directory of Open Access Journals (Sweden)

    Sibel MORKOÇ KARADENİZ

    2016-11-01

    Full Text Available In this study, Zinc Oxide (ZnO seed layers were prepared on Indium Tin Oxide (ITO substrates by using Chemical Bath Deposition (CBD method and Sol-gel Spin Coating (SC method. ZnO micro-nanorod arrays were grown on ZnO seed layers by using Hydrothermal Synthesis method. Seed layer effects of structural and optical properties of ZnO arrays were characterized. X-ray diffractometer (XRD, Scanning Electron Microscopy (SEM and Ultraviolet Visible (UV-Vis Spectrometer were used for analyses. ZnO micro-nanorod arrays consisted of a single crystalline wurtzite ZnO structure for each seed layer. Besides, ZnO rod arrays were grown smoothly and vertically on SC seed layer, while ZnO rod arrays were grown randomly and flower like structures on CBD seed layer. The optical absorbance peaks found at 422 nm wavelength in the visible region for both ZnO arrays. Optical bandgap values were determined by using UV-Vis measurements at 3.12 and 3.15 eV for ZnO micro-nanorod arrays on CBD seed layer and for ZnO micro-nanorod arrays on SC-seed layer respectively.DOI: http://dx.doi.org/10.5755/j01.ms.22.4.13443

  13. Effect of reactant concentration on the structural properties of hydrothermally-grown ZnO rods on seed-layer ZnO / polyethylene terephthalate substrates

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Y. I.; Shin, C. M.; Heo, J. H.; Ryu, H. [Inje University, Gimhae (Korea, Republic of); Lee, W. J. [Dong-Eui University, Busan (Korea, Republic of); Son, C. S. [Silla University, Busan (Korea, Republic of); Choi, H. [Pukyong National University, Busan (Korea, Republic of)

    2011-09-15

    The morphology and the structural properties were studied for zinc-oxide (ZnO) rods hydrothermally grown on seed-layer ZnO/polyethylene terephthalate (PET) substrates at various reactant concentrations. Dissolved solutions with de-ionized water, zinc nitrate hexahydrate (Zn(NO{sub 3}){sub 2}{center_dot}6H{sub 2}O, ZNH) and hexamethylenetetramine (C{sub 6}H{sub 12}N{sub 4}, HMT) were employed as reactants for hydrothermal growth of ZnO. The transparency of the mixtures (ZNH+HMT) with increasing reactant concentration from 0.025 to 0.25 M changed from transparent to translucent to opaque (white colors) due to Zn(OH){sub 2} precipitates. When the concentration was increased, the density of the ZnO rods increased, and the morphology of the ZnO rods changed from a hexagonal flat-end shape to a sharp-end or flake-like structure. The sharp-end rods with increasing concentration from 0.1 to 0.15 M resulted from the etching process at a lower pH condition (less than pH 6) after the ZnO rod growth, and the flake-like structure was due to a high growth rate. The ZnO seed layer might have improved the alignment of ZnO rods and made a high density of ZnO rods. In addition, the structural properties were improved at lower concentrations by inserting a seed layer.

  14. Evolution of microstructure and related optical properties of ZnO grown by atomic layer deposition

    Directory of Open Access Journals (Sweden)

    Adib Abou Chaaya

    2013-10-01

    Full Text Available A study of transmittance and photoluminescence spectra on the growth of oxygen-rich ultra-thin ZnO films prepared by atomic layer deposition is reported. The structural transition from an amorphous to a polycrystalline state is observed upon increasing the thickness. The unusual behavior of the energy gap with thickness reflected by optical properties is attributed to the improvement of the crystalline structure resulting from a decreasing concentration of point defects at the growth of grains. The spectra of UV and visible photoluminescence emissions correspond to transitions near the band-edge and defect-related transitions. Additional emissions were observed from band-tail states near the edge. A high oxygen ratio and variable optical properties could be attractive for an application of atomic layer deposition (ALD deposited ultrathin ZnO films in optical sensors and biosensors.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-10-01

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

  16. Characterization of ZnO film grown on polycarbonate by atomic layer deposition at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Gyeong Beom; Han, Gwon Deok; Shim, Joon Hyung; Choi, Byoung-Ho, E-mail: bhchoi@korea.ac.kr [School of Mechanical Engineering, Korea University, Seoul 136-707 (Korea, Republic of)

    2015-01-15

    ZnO is an attractive material for use in various technological products such as phosphors, gas sensors, and transparent conductors. Recently, aluminum-doped zinc oxide has received attention as a potential replacement for indium tin oxide, which is one of the transparent conductive oxides used in flat panel displays, organic light-emitting diodes, and organic solar cells. In this study, the characteristics of ZnO films deposited on polycarbonate (PC) substrates by atomic layer deposition (ALD) are investigated for various process temperatures. The growth mechanism of these films was investigated at low process temperatures using x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS). XRD and XPS were used to determine the preferred orientation and chemical composition of the films, respectively. Furthermore, the difference of the deposition mechanisms on an amorphous organic material, i.e., PC substrate and an inorganic material such as silicon was discussed from the viewpoint of the diffusion and deposition of precursors. The structure of the films was also investigated by chemical analysis in order to determine the effect of growth temperature on the films deposited by ALD.

  17. Strain-free GaN thick films grown on single crystalline ZnO buffer layer with in situ lift-off technique

    International Nuclear Information System (INIS)

    Lee, S. W.; Minegishi, T.; Lee, W. H.; Goto, H.; Lee, H. J.; Lee, S. H.; Lee, Hyo-Jong; Ha, J. S.; Goto, T.; Hanada, T.; Cho, M. W.; Yao, T.

    2007-01-01

    Strain-free freestanding GaN layers were prepared by in situ lift-off process using a ZnO buffer as a sacrificing layer. Thin Zn-polar ZnO layers were deposited on c-plane sapphire substrates, which was followed by the growth of Ga-polar GaN layers both by molecular beam epitaxy (MBE). The MBE-grown GaN layer acted as a protecting layer against decomposition of the ZnO layer and as a seeding layer for GaN growth. The ZnO layer was completely in situ etched off during growth of thick GaN layers at low temperature by hydride vapor phase epitaxy. Hence freestanding GaN layers were obtained for the consecutive growth of high-temperature GaN thick layers. The lattice constants of freestanding GaN agree with those of strain-free GaN bulk. Extensive microphotoluminescence study indicates that strain-free states extend throughout the high-temperature grown GaN layers

  18. Quantitative and simultaneous analysis of the polarity of polycrystalline ZnO seed layers and related nanowires grown by wet chemical deposition

    Science.gov (United States)

    Guillemin, Sophie; Parize, Romain; Carabetta, Joseph; Cantelli, Valentina; Albertini, David; Gautier, Brice; Brémond, Georges; Fong, Dillon D.; Renevier, Hubert; Consonni, Vincent

    2017-03-01

    The polarity in ZnO nanowires is an important issue since it strongly affects surface configuration and reactivity, nucleation and growth, electro-optical properties, and nanoscale-engineering device performances. However, measuring statistically the polarity of ZnO nanowire arrays grown by chemical bath deposition and elucidating its correlation with the polarity of the underneath polycrystalline ZnO seed layer grown by the sol-gel process represents a major difficulty. To address that issue, we combine resonant x-ray diffraction (XRD) at Zn K-edge using synchrotron radiation with piezoelectric force microscopy and polarity-sensitive chemical etching to statistically investigate the polarity of more than 107 nano-objects both on the macroscopic and local microscopic scales, respectively. By using high temperature annealing under an argon atmosphere, it is shown that the compact, highly c-axis oriented ZnO seed layer is more than 92% Zn-polar and that only a few small O-polar ZnO grains with an amount less than 8% are formed. Correlatively, the resulting ZnO nanowires are also found to be Zn-polar, indicating that their polarity is transferred from the c-axis oriented ZnO grains acting as nucleation sites in the seed layer. These findings pave the way for the development of new strategies to form unipolar ZnO nanowire arrays as a requirement for a number of nanoscale-engineering devices like piezoelectric nanogenerators. They also highlight the great advantage of resonant XRD as a macroscopic, non-destructive method to simultaneously and statistically measure the polarity of ZnO nanowire arrays and of the underneath ZnO seed layer.

  19. Effect of substrates and thickness on optical properties in atomic layer deposition grown ZnO thin films

    Science.gov (United States)

    Pal, Dipayan; Singhal, Jaya; Mathur, Aakash; Singh, Ajaib; Dutta, Surjendu; Zollner, Stefan; Chattopadhyay, Sudeshna

    2017-11-01

    Atomic Layer Deposition technique was used to grow high quality, very low roughness, crystalline, Zinc Oxide (ZnO) thin films on silicon (Si) and fused quartz (SiO2) substrates to study the optical properties. Spectroscopic ellipsometry results of ZnO/Si system, staggered type-II quantum well, demonstrate that there is a significant drop in the magnitudes of both the real and imaginary parts of complex dielectric constants and in near-band gap absorption along with a blue shift of the absorption edge with decreasing film thickness at and below ∼20 nm. Conversely, UV-vis absorption spectroscopy of ZnO/SiO2, thin type-I quantum well, consisting of a narrower-band gap semiconductor grown on a wider-band gap (insulator) substrate, shows the similar thickness dependent blue-shift of the absorption edge but with an increase in the magnitude of near-band gap absorption with decreasing film thickness. Thickness dependent blue shift, energy vs. 1/d2, in two different systems, ZnO/Si and ZnO/SiO2, show a difference in their slopes. The observed phenomena can be consistently explained by the corresponding exciton (or carrier/s) deconfinement and confinement effects at the ZnO/Si and ZnO/SiO2 interface respectively, where Tanguy-Elliott amplitude pre-factor plays the key role through the electron-hole overlap factor at the interface.

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

    International Nuclear Information System (INIS)

    Kim, Byunggu; Leem, Jae-Young

    2017-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-01-15

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

  2. Resistivity of atomic layer deposition grown ZnO: The influence of deposition temperature and post-annealing

    Energy Technology Data Exchange (ETDEWEB)

    Laube, J., E-mail: laube@imtek.de; Nübling, D.; Beh, H.; Gutsch, S.; Hiller, D.; Zacharias, M.

    2016-03-31

    Conductive zinc oxide (ZnO) films deposited by atomic layer deposition were studied as function of post-annealing treatments. Effusion experiments were conducted on ZnO films deposited at different temperatures. The influence of different annealing atmospheres on the resistivity of the films was investigated and compared to reference samples. It was found that the influence of the deposition temperature on the resistivity is much higher than that of subsequent annealings. This leads to the conclusion that reduction of the resistivity by diffusion of different gases, such as oxygen and hydrogen, into annealed ZnO films is unlikely. - Highlights: • Conformal growth of ZnO-ALD over a temperature range of 25 °C up to 300 °C. • Post-annealing in different atmospheres (H{sub 2}, O{sub 2}, vacuum) and temperatures. • Analysis of film-conductivity and effusion characteristic.

  3. Bipolar resistive switching characteristics of low temperature grown ZnO thin films by plasma-enhanced atomic layer deposition

    International Nuclear Information System (INIS)

    Zhang Jian; Yang Hui; Zhang Qilong; Dong Shurong; Luo, J. K.

    2013-01-01

    ZnO films deposited by plasma-enhanced atomic layer deposition (PEALD) have been used to investigate resistive memory behavior. The bipolar resistance switching properties were observed in the Al/PEALD-ZnO/Pt devices. The resistance ratio for the high and low resistance states (HRS/LRS) is more than 10 3 , better than ZnO devices deposited by other methods. The dominant conduction mechanisms of HRS and LRS are trap-controlled space charge limited current and Ohmic behavior, respectively. The resistive switching behavior is induced upon the formation/disruption of conducting filaments. This study demonstrated that the PEALD-ZnO films have better properties for the application in 3D resistance random access memory.

  4. Observation of dopant-profile independent electron transport in sub-monolayer TiO{sub x} stacked ZnO thin films grown by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Saha, D., E-mail: sahaphys@gmail.com, E-mail: pmisra@rrcat.gov.in; Misra, P., E-mail: sahaphys@gmail.com, E-mail: pmisra@rrcat.gov.in; Joshi, M. P.; Kukreja, L. M. [Laser Materials Processing Division, Raja Ramanna Centre for Advanced Technology, Indore 452 013 (India); Das, Gangadhar [Indus Synchrotrons Utilisation Division, Raja Ramanna Centre for Advanced Technology, Indore 452 013 (India)

    2016-01-18

    Dopant-profile independent electron transport has been observed through a combined study of temperature dependent electrical resistivity and magnetoresistance measurements on a series of Ti incorporated ZnO thin films with varying degree of static-disorder. These films were grown by atomic layer deposition through in-situ vertical stacking of multiple sub-monolayers of TiO{sub x} in ZnO. Upon decreasing ZnO spacer layer thickness, electron transport smoothly evolved from a good metallic to an incipient non-metallic regime due to the intricate interplay of screening of spatial potential fluctuations and strength of static-disorder in the films. Temperature dependent phase-coherence length as extracted from the magnetotransport measurement revealed insignificant role of inter sub-monolayer scattering as an additional channel for electron dephasing, indicating that films were homogeneously disordered three-dimensional electronic systems irrespective of their dopant-profiles. Results of this study are worthy enough for both fundamental physics perspective and efficient applications of multi-stacked ZnO/TiO{sub x} structures in the emerging field of transparent oxide electronics.

  5. Electrical and mechanical stability of aluminum-doped ZnO films grown on flexible substrates by atomic layer deposition

    International Nuclear Information System (INIS)

    Luka, G.; Witkowski, B.S.; Wachnicki, L.; Jakiela, R.; Virt, I.S.; Andrzejczuk, M.; Lewandowska, M.; Godlewski, M.

    2014-01-01

    Highlights: • Transparent and conductive ZnO:Al films were grown by atomic layer deposition. • The films were grown on flexible substrates at low growth temperatures (110–140 °C). • So-obtained films have low resistivities, of the order of 10 −3 Ω cm. • Bending tests indicated a critical bending radius of ≈1.2 cm. • Possible sources of the film resistivity changes upon bending are proposed. - Abstract: Aluminum-doped zinc oxide (AZO) films were grown on polyethylene terephthalate (PET) substrates by atomic layer deposition (ALD) at low deposition temperatures (110–140 °C). The films have low resistivities, ∼10 −3 Ω cm, and high transparency (∼90%) in the visible range. Bending tests indicated a critical bending radius of ≈1.2 cm, below which the resistivity changes became irreversible. The films deposited on PET with additional buffer layer are more stable upon bending and temperature changes

  6. Hybrid Organic/ZnO p-n Junctions with n-Type ZnO Grown by Atomic Layer Deposition

    Science.gov (United States)

    Łuka, G.; Krajewski, T.; Szczerbakow, A.; Łusakowska, E.; Kopalko, K.; Guziewicz, E.; Wachnicki, Ł.; Szczepanik, A.; Godlewski, M.; Fidelus, J. D.

    2008-11-01

    We report on fabrication of hybrid inorganic-on-organic thin film structures with polycrystalline zinc oxide films grown by atomic layer deposition technique. ZnO films were deposited on two kinds of thin organic films, i.e. pentacene and poly(dimethylosiloxane) elastomer with a carbon nanotube content (PDMS:CNT). Surface morphology as well as electrical measurements of the films and devices were analyzed. The current density versus voltage (I-V) characteristics of ITO/pentacene/ZnO/Au structure show a low-voltage switching phenomenon typical of organic memory elements. The I-V studies of ITO/PDMS:CNT/ZnO/Au structure indicate some charging effects in the system under applied voltages.

  7. ZnO based nanowires grown by chemical vapour deposition for selective hydrogenation of acetylene alcohols

    NARCIS (Netherlands)

    Protasova, L.N.; Rebrov, E.; Choy, K.L.; Pung, S.Y.; Engels, V.; Cabaj, M.; Wheatley, A.E.H.; Schouten, J.C.

    2011-01-01

    Vertically aligned ZnO nanowires (NWs) with a length of 1.5–10 µm and a mean diameter of ca. 150 nm were grown by chemical vapour deposition onto a c-oriented ZnO seed layer which was deposited by atomic layer deposition on Si substrates. The substrates were then spin-coated with an ethanol solution

  8. Different defect levels configurations between double layers of nanorods and film in ZnO grown on c-Al2O3 by MOCVD

    International Nuclear Information System (INIS)

    Wu, Bin; Zhang, Yuantao; Shi, Zhifeng; Li, Xiang; Cui, Xijun; Zhuang, Shiwei; Zhang, Baolin; Du, Guotong

    2014-01-01

    Epitaxial ZnO structures with inherent two layers of nanorods layer on film layer were fabricated on c-Al 2 O 3 by metal-organic chemical vapor deposition (MOCVD) and studied by photoluminescence. Specially, photoluminescence spectra for the film layer were obtained by rendering the excitation from the substrate side. Different defect levels configurations between nanorods and film were revealed. Zinc vacancies tend to form in top nanorods layer, whereas abundant zinc–oxygen divacancies accumulate in bottom film layer. An acceptor state with activation energy of ∼200 meV is exclusive to the film layer. The stacking fault related acceptor and Al introduced donor are present in both layers. Besides, two other defect related donors contained in the nanorods layer perhaps also exist within the film layer. - Highlights: • Inherent double layer ZnO of nanorods on film layer were studied by PL. • V Zn tend to form in the nanorods layer, and V ZnO accumulate in the film layer. • An acceptor with activation energy of ∼200 meV is exclusive to the film layer. • Pure NBE emission without DLE in RT PL spectrum does not mean good crystallinity

  9. Studies of surface morphology and optical properties of ZnO nanostructures grown on different molarities of TiO_2 seed layer

    International Nuclear Information System (INIS)

    Asib, N. A. M.; Afaah, A. N.; Aadila, A.; Khusaimi, Z.; Rusop, M.

    2016-01-01

    Titanium dioxide (TiO_2) seed layer was prepared by using sol-gel spin-coating technique, followed by growth of 0.01 M of Zinc oxide (ZnO) nanostructures by solution-immersion. The molarities of TiO_2 seed layer were varied from 1.1 M to 0.100 M on glass substrates. The nanostructures thin films were characterized by Field Emission Scanning Electrons Microscope (FESEM), Photoluminescence (PL) spectroscopy and Ultraviolet-Visible (UV-Vis) spectroscopy. FESEM images demonstrate that needle-like ZnO nanostructures are formed on all TiO_2 seed layer. The smallest diameter of needle-like ZnO nanostructures (90.3 nm) were deposited on TiO_2 seed layer of 0.100 M. PL spectra of the TiO_2: ZnO nanostructures thin films show the blue shifted emissions in the UV regions compared to the ZnO thin film. Meanwhile, UV-vis spectra of films display high absorption in the UV region and high trasparency in the visible region. The highest absorbance at UV region was recorded for sample which has 0.100 M of TiO_2 seed layer.

  10. Photoelectrochemical and Raman characterization of nanocrystalline CdS grown on ZnO by successive ionic layer adsorption and reaction method

    Energy Technology Data Exchange (ETDEWEB)

    Kozytskiy, A.V. [L.V. Pysarzhevsky Institute of Physical Chemistry of National Academy of Sciences of Ukraine, 31 Nauky Av., 03028 Kyiv (Ukraine); Stroyuk, O.L., E-mail: stroyuk@inphyschem-nas.kiev.ua [L.V. Pysarzhevsky Institute of Physical Chemistry of National Academy of Sciences of Ukraine, 31 Nauky Av., 03028 Kyiv (Ukraine); Kuchmiy, S.Ya. [L.V. Pysarzhevsky Institute of Physical Chemistry of National Academy of Sciences of Ukraine, 31 Nauky Av., 03028 Kyiv (Ukraine); Mazanik, A.V.; Poznyak, S.K. [Belarusian State University, Nezalezhnastsi Av. 4, Minsk 220030 (Belarus); Streltsov, E.A., E-mail: streltea@bsu.by [Belarusian State University, Nezalezhnastsi Av. 4, Minsk 220030 (Belarus); Kulak, A.I., E-mail: kulak@igic.bas-net.by [Institute of General and Inorganic Chemistry, National Academy of Sciences of Belarus, Surganova str., 9/1, Minsk 220072 (Belarus); Korolik, O.V. [Belarusian State University, Nezalezhnastsi Av. 4, Minsk 220030 (Belarus); Dzhagan, V.M., E-mail: dzhagan@isp.kiev.ua [V.E. Lashkaryov Institute of Semiconductor Physics of National Academy of Sciences of Ukraine, 41 Nauky Av., 03028 Kyiv (Ukraine)

    2014-07-01

    Properties of CdS nanoparticles (NPs) grown by successive ionic layer adsorption and reaction (SILAR) method on the surface of electrodeposited ZnO films were studied by Raman, photocurrent and UV–Vis absorption spectroscopies. The CdS nanoparticles deposited at a SILAR cycle number (N) from 5 to 10 exhibit a broadening of the band gap (E{sub g}) by 0.17–0.31 eV as compared with that of the CdS particles grown at N = 30. The size quantization of the interband transition energy in CdS nanoparticles is in accordance with the Raman spectroscopic data demonstrating a considerable increase in the LO peak intensity with increasing the N from 5 to 10 as a result of transition to resonant light scattering. The spectral width of the LO peak decreases from 50 to 15 cm{sup −1} as the N increases from 5 to 30 reflecting a less pronounced effect of the nanoparticle surface on the phonon scattering. A large spectral width of the Raman peaks is assumed to originate from a complex structure of the CdS nanoparticles comprising crystallinity domains that can affect the phonon confinement. The photocurrent spectroscopy of ZnO/CdS heterostructures showed that the band gap of CdS NPs deposited at N > 20 is smaller by ∼ 0.08 eV than that of bulk cadmium sulfide. It was concluded that this effect is not associated with photoexcitation of structural defects but rather reflects intrinsic electronic properties of SILAR-deposited CdS nanoparticles. - Highlights: • Visible-light-sensitive ZnO/CdS heterostructures were prepared by SILAR. • A large Raman peak width originates from a complex structure of CdS nanoparticles. • Vibrational properties of CdS nanoparticles depend on SILAR cycle number.

  11. Photoelectrochemical and Raman characterization of nanocrystalline CdS grown on ZnO by successive ionic layer adsorption and reaction method

    International Nuclear Information System (INIS)

    Kozytskiy, A.V.; Stroyuk, O.L.; Kuchmiy, S.Ya.; Mazanik, A.V.; Poznyak, S.K.; Streltsov, E.A.; Kulak, A.I.; Korolik, O.V.; Dzhagan, V.M.

    2014-01-01

    Properties of CdS nanoparticles (NPs) grown by successive ionic layer adsorption and reaction (SILAR) method on the surface of electrodeposited ZnO films were studied by Raman, photocurrent and UV–Vis absorption spectroscopies. The CdS nanoparticles deposited at a SILAR cycle number (N) from 5 to 10 exhibit a broadening of the band gap (E g ) by 0.17–0.31 eV as compared with that of the CdS particles grown at N = 30. The size quantization of the interband transition energy in CdS nanoparticles is in accordance with the Raman spectroscopic data demonstrating a considerable increase in the LO peak intensity with increasing the N from 5 to 10 as a result of transition to resonant light scattering. The spectral width of the LO peak decreases from 50 to 15 cm −1 as the N increases from 5 to 30 reflecting a less pronounced effect of the nanoparticle surface on the phonon scattering. A large spectral width of the Raman peaks is assumed to originate from a complex structure of the CdS nanoparticles comprising crystallinity domains that can affect the phonon confinement. The photocurrent spectroscopy of ZnO/CdS heterostructures showed that the band gap of CdS NPs deposited at N > 20 is smaller by ∼ 0.08 eV than that of bulk cadmium sulfide. It was concluded that this effect is not associated with photoexcitation of structural defects but rather reflects intrinsic electronic properties of SILAR-deposited CdS nanoparticles. - Highlights: • Visible-light-sensitive ZnO/CdS heterostructures were prepared by SILAR. • A large Raman peak width originates from a complex structure of CdS nanoparticles. • Vibrational properties of CdS nanoparticles depend on SILAR cycle number

  12. Reduced defect densities in the ZnO epilayer grown on Si substrates by laser-assisted molecular-beam epitaxy using a ZnS epitaxial buffer layer

    International Nuclear Information System (INIS)

    Onuma, T.; Chichibu, S.F.; Uedono, A.; Yoo, Y.-Z.; Chikyow, T.; Sota, T.; Kawasaki, M.; Koinuma, H.

    2004-01-01

    Nonradiative photoluminescence (PL) lifetime (τ nr ) and point defect density in the (0001) ZnO epilayer grown on (111) Si substrates by laser-assisted molecular-beam epitaxy (L-MBE) using a (0001) ZnS epitaxial buffer layer were compared with those in the ZnO films on (111) and (001) Si substrates prepared by direct transformation of ZnS epilayers on Si by thermal oxidation [Yoo et al., Appl. Phys. Lett. 78, 616 (2001)]. Both the ZnO films exhibited excitonic reflectance anomalies and corresponding PL peaks at low temperature, and the density or size of vacancy-type point defects (Zn vacancies), which were measured by the monoenergetic positron annihilation measurement, in the L-MBE epilayer was lower than that in the films prepared by the oxidation transformation. The ZnO epilayer grown on a (0001) ZnS epitaxial buffer on (111) Si exhibited longer τ nr of 105 ps at room temperature

  13. Electrical properties of ZnO thin films grown by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Pagni, O. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Somhlahlo, N.N. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Weichsel, C. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Leitch, A.W.R. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa)]. E-mail: andrew.leitch@nmmu.ac.za

    2006-04-01

    We report on the electrical characterization of ZnO films grown by MOCVD on glass and sapphire substrates. After correcting our temperature variable Hall measurements by applying the standard two-layer model, which takes into account an interfacial layer, scattering mechanisms in the ZnO films were studied as well as donor activation energies determined. ZnO films grown at different oxygen partial pressures indicated the importance of growth conditions on the defect structure by means of their conductivities and conductivity activation energies.

  14. Electrical properties of ZnO thin films grown by MOCVD

    International Nuclear Information System (INIS)

    Pagni, O.; Somhlahlo, N.N.; Weichsel, C.; Leitch, A.W.R.

    2006-01-01

    We report on the electrical characterization of ZnO films grown by MOCVD on glass and sapphire substrates. After correcting our temperature variable Hall measurements by applying the standard two-layer model, which takes into account an interfacial layer, scattering mechanisms in the ZnO films were studied as well as donor activation energies determined. ZnO films grown at different oxygen partial pressures indicated the importance of growth conditions on the defect structure by means of their conductivities and conductivity activation energies

  15. Synthesis and microstructural characterization of growth direction controlled ZnO nanorods using a buffer layer

    International Nuclear Information System (INIS)

    Park, Dong Jun; Kim, Dong Chan; Lee, Jeong Yong; Cho, Hyung Koun

    2006-01-01

    The growth direction and morphology of one-dimensional ZnO nanostructures grown by metal-organic chemical vapour deposition (MOCVD) were modulated by changing the growth temperature of previously deposited ZnO buffer layers that were used as a template. The ZnO nanorods grown on the low-temperature deposited buffer layer were regularly inclined with respect to the substrate surface and show in-plane alignment with azimuthally six-fold symmetry. In contrast, deposition of the buffer layer at higher growth temperature led to the formation of vertically well-aligned ZnO nanorods. In addition, the ZnO nanorods grown on the buffer layer deposited at low growth temperature show a growth direction of [1 0 1-bar 0], unlike the conventional ZnO nanorods showing a growth direction of [0001]. The microstructural analysis and atomic modelling of the formation of regularly inclined nanorods using transmission electron microscopy are presented

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-04-19

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

  17. Studies on morphology, electrical and optical characteristics of Al-doped ZnO thin films grown by atomic layer deposition

    Science.gov (United States)

    Chen, Li; Chen, Xinliang; Zhou, Zhongxin; Guo, Sheng; Zhao, Ying; Zhang, Xiaodan

    2018-03-01

    Al doped ZnO (AZO) films deposited on glass substrates through the atomic layer deposition (ALD) technique are investigated with various temperatures from 100 to 250 °C and different Zn : Al cycle ratios from 20 : 0 to 20 : 3. Surface morphology, structure, optical and electrical properties of obtained AZO films are studied in detail. The Al composition of the AZO films is varied by controlling the ratio of Zn : Al. We achieve an excellent AZO thin film with a resistivity of 2.14 × 10‑3 Ω·cm and high optical transmittance deposited at 150 °C with 20 : 2 Zn : Al cycle ratio. This kind of AZO thin films exhibit great potential for optoelectronics device application. Project supported by the State Key Development Program for Basic Research of China (Nos. 2011CBA00706, 2011CBA00707) and the Tianjin Applied Basic Research Project and Cutting-Edge Technology Research Plan (No. 13JCZDJC26900).

  18. Characterization of homoepitaxial and heteroepitaxial ZnO films grown by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Z.Q. [Japan Atomic Energy Research Institute, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan)]. E-mail: chenzq@taka.jaeri.go.jp; Yamamoto, S. [Japan Atomic Energy Research Institute, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Kawasuso, A. [Japan Atomic Energy Research Institute, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Xu, Y. [Japan Atomic Energy Research Institute, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Sekiguchi, T. [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)

    2005-05-15

    Homo- and heteroepitaxial ZnO films were grown on ZnO (0001) and Al{sub 2}O{sub 3} (1-bar 1-bar 2-bar -bar 0) substrates by using pulsed laser deposition. The X-ray diffraction and Raman measurements for these films show good correspondence with the bulk ZnO substrate, which confirms successful growth of c-axis oriented ZnO layer. Strong UV emission was also observed in these films, indicating good optical quality. However, the surface roughness differs very much for the homo- and heteroepitaxial film, that is, much less for the homoepitaxial layer. Positron annihilation measurements reveal a higher vacancy concentration in the homoepitaxial layer.

  19. Hydrothermal Growth of Vertically Aligned ZnO Nanorods Using a Biocomposite Seed Layer of ZnO Nanoparticles.

    Science.gov (United States)

    Ibupoto, Zafar Hussain; Khun, Kimleang; Eriksson, Martin; AlSalhi, Mohammad; Atif, Muhammad; Ansari, Anees; Willander, Magnus

    2013-08-19

    Well aligned ZnO nanorods have been prepared by a low temperature aqueous chemical growth method, using a biocomposite seed layer of ZnO nanoparticles prepared in starch and cellulose bio polymers. The effect of different concentrations of biocomposite seed layer on the alignment of ZnO nanorods has been investigated. ZnO nanorods grown on a gold-coated glass substrate have been characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques. These techniques have shown that the ZnO nanorods are well aligned and perpendicular to the substrate, and grown with a high density and uniformity on the substrate. Moreover, ZnO nanorods can be grown with an orientation along the c -axis of the substrate and exhibit a wurtzite crystal structure with a dominant (002) peak in an XRD spectrum and possessed a high crystal quality. A photoluminescence (PL) spectroscopy study of the ZnO nanorods has revealed a conventional near band edge ultraviolet emission, along with emission in the visible part of the electromagnetic spectrum due to defect emission. This study provides an alternative method for the fabrication of well aligned ZnO nanorods. This method can be helpful in improving the performance of devices where alignment plays a significant role.

  20. Hydrothermal Growth of Vertically Aligned ZnO Nanorods Using a Biocomposite Seed Layer of ZnO Nanoparticles

    Directory of Open Access Journals (Sweden)

    Zafar Hussain Ibupoto

    2013-08-01

    Full Text Available Well aligned ZnO nanorods have been prepared by a low temperature aqueous chemical growth method, using a biocomposite seed layer of ZnO nanoparticles prepared in starch and cellulose bio polymers. The effect of different concentrations of biocomposite seed layer on the alignment of ZnO nanorods has been investigated. ZnO nanorods grown on a gold-coated glass substrate have been characterized by X-ray diffraction (XRD and field emission scanning electron microscopy (FESEM techniques. These techniques have shown that the ZnO nanorods are well aligned and perpendicular to the substrate, and grown with a high density and uniformity on the substrate. Moreover, ZnO nanorods can be grown with an orientation along the c-axis of the substrate and exhibit a wurtzite crystal structure with a dominant (002 peak in an XRD spectrum and possessed a high crystal quality. A photoluminescence (PL spectroscopy study of the ZnO nanorods has revealed a conventional near band edge ultraviolet emission, along with emission in the visible part of the electromagnetic spectrum due to defect emission. This study provides an alternative method for the fabrication of well aligned ZnO nanorods. This method can be helpful in improving the performance of devices where alignment plays a significant role.

  1. High quality ZnO layers with adjustable refractive indices for integrated optics applications

    NARCIS (Netherlands)

    Heideman, Rene; Lambeck, Paul; Gardeniers, Johannes G.E.

    1995-01-01

    Thin (approx. 1 μm) crystalline ZnO films with a good optical quality and a good (0002) texture are grown under two considerably different process parameter sets using a r.f. planar magnetron sputtering unit. The optical parameters of the two corresponding ZnO layers are distinctly different: high

  2. Band-gap and sub-band-gap photoelectrochemical processes at nanocrystalline CdS grown on ZnO by successive ionic layer adsorption and reaction method

    International Nuclear Information System (INIS)

    Malashchonak, M.V.; Streltsov, E.A.; Mazanik, A.V.; Kulak, A.I.; Poznyak, S.K.; Stroyuk, O.L.; Kuchmiy, S.Ya.; Gaiduk, P.I.

    2015-01-01

    Cadmium sulfide nanoparticle (NP) deposition by the successive ionic layer adsorption and reaction (SILAR) method on the surface of mesoporous ZnO micro-platelets with a large specific surface area (110 ± 10 m 2 g −1 ) results in the formation of ZnO/CdS heterostructures exhibiting a high incident photon-to-current conversion efficiency (Y) not only within the region of CdS fundamental absorption (Y max = 90%; 0.1 M Na 2 S + 0.1 M Na 2 SO 3 ), but also in the sub-band-gap (SBG) range (Y max = 25%). The onset potentials of SBG photoelectrochemical processes are more positive than the band-gap (BG) onset potential by up to 100 mV. A maximum incident photon-to-current conversion efficiency value for SBG processes is observed at larger amount of deposited CdS in comparison with the case of BG ones. The Urbach energy (E U ) of CdS NPs determined from the photocurrent spectra reaches a maximal value on an early deposition stage (E U = 93 mV at SILAR cycle number N = 5), then lowers somewhat (E U = 73 mV at N = 10) and remains steady in the range of N from 20 to 300 (E U = 67 ± 1 mV). High efficiency of the photoelectrochemical SBG processes are interpreted in terms of light scattering in the ZnO/CdS heterostructures. - Highlights: • ZnO/CdS films demonstrate high quantum efficiency (25%) for sub-band-gap transitions. • Onset photocurrent potentials for sub-band-gap processes differ than those for band-gap ones. • Sub-band-gap transitions are caused by band-tail states in CdS nanoparticles

  3. Band-gap and sub-band-gap photoelectrochemical processes at nanocrystalline CdS grown on ZnO by successive ionic layer adsorption and reaction method

    Energy Technology Data Exchange (ETDEWEB)

    Malashchonak, M.V., E-mail: che.malasche@gmail.com [Belarusian State University, Nezalezhnastsi Av. 4, Minsk 220030 (Belarus); Streltsov, E.A., E-mail: streltea@bsu.by [Belarusian State University, Nezalezhnastsi Av. 4, Minsk 220030 (Belarus); Mazanik, A.V. [Belarusian State University, Nezalezhnastsi Av. 4, Minsk 220030 (Belarus); Kulak, A.I., E-mail: kulak@igic.bas-net.by [Institute of General and Inorganic Chemistry, National Academy of Sciences of Belarus, Surganova str., 9/1, Minsk 220072 (Belarus); Poznyak, S.K. [Belarusian State University, Nezalezhnastsi Av. 4, Minsk 220030 (Belarus); Stroyuk, O.L., E-mail: stroyuk@inphyschem-nas.kiev.ua [L.V. Pysarzhevsky Institute of Physical Chemistry of National Academy of Sciences of Ukraine, 31 prosp. Nauky, 03028 Kyiv (Ukraine); Kuchmiy, S.Ya. [L.V. Pysarzhevsky Institute of Physical Chemistry of National Academy of Sciences of Ukraine, 31 prosp. Nauky, 03028 Kyiv (Ukraine); Gaiduk, P.I. [Belarusian State University, Nezalezhnastsi Av. 4, Minsk 220030 (Belarus)

    2015-08-31

    Cadmium sulfide nanoparticle (NP) deposition by the successive ionic layer adsorption and reaction (SILAR) method on the surface of mesoporous ZnO micro-platelets with a large specific surface area (110 ± 10 m{sup 2}g{sup −1}) results in the formation of ZnO/CdS heterostructures exhibiting a high incident photon-to-current conversion efficiency (Y) not only within the region of CdS fundamental absorption (Y{sub max} = 90%; 0.1 M Na{sub 2}S + 0.1 M Na{sub 2}SO{sub 3}), but also in the sub-band-gap (SBG) range (Y{sub max} = 25%). The onset potentials of SBG photoelectrochemical processes are more positive than the band-gap (BG) onset potential by up to 100 mV. A maximum incident photon-to-current conversion efficiency value for SBG processes is observed at larger amount of deposited CdS in comparison with the case of BG ones. The Urbach energy (E{sub U}) of CdS NPs determined from the photocurrent spectra reaches a maximal value on an early deposition stage (E{sub U} = 93 mV at SILAR cycle number N = 5), then lowers somewhat (E{sub U} = 73 mV at N = 10) and remains steady in the range of N from 20 to 300 (E{sub U} = 67 ± 1 mV). High efficiency of the photoelectrochemical SBG processes are interpreted in terms of light scattering in the ZnO/CdS heterostructures. - Highlights: • ZnO/CdS films demonstrate high quantum efficiency (25%) for sub-band-gap transitions. • Onset photocurrent potentials for sub-band-gap processes differ than those for band-gap ones. • Sub-band-gap transitions are caused by band-tail states in CdS nanoparticles.

  4. Electrical properties of ZnO nanorods and layers

    Energy Technology Data Exchange (ETDEWEB)

    Schlenker, Eva; Bakin, Andrey; Peters, Ole; Mofor, Augustine C.; Postels, Bianca; El-Shaer, Hamid; Wehmann, Hergo-Heinrich; Waag, Andreas [Institut fuer Halbleitertechnik, TU Braunschweig (Germany); Weimann, Thomas; Hinze, Peter [Physikalisch-Technische Bundesanstalt (PTB), Braunschweig (Germany)

    2007-07-01

    ZnO has attracted a lot of interest in the scientific community due to its outstanding properties. With a band gap of 3.37 eV and an exciton binding energy of 60 meV it is a promising candidate for micro- and optoelectronic applications. The growth of ZnO nanostructures and epitaxial layers is well under control and their optical and structural properties are already thoroughly characterized. However, due to contacting difficulties, less reports exist on the electrical properties of single ZnO nanostructures. In this contribution we present various contacting methods in order to explore the electrical properties of individual nanorods either grown by aqueous chemical growth or vapor phase transport. Current-Voltage characteristics were obtained by using an atomic force microscope with a conductive tip or by patterning contacts with e-beam lithography. The results are compared to the ones obtained from measurements on epitaxially grown ZnO layers and first applications are presented.

  5. Origin of the 2.45 eV luminescence band observed in ZnO epitaxial layers grown on c-plane sapphire by chemical vapour deposition

    International Nuclear Information System (INIS)

    Saroj, R K; Dhar, S

    2014-01-01

    Zinc oxide epitaxial layers have been grown on c-plane sapphire substrates by the chemical vapour deposition (CVD) technique. A structural study shows (0001)-oriented films with good crystalline quality. The temperature and excitation power dependence of the photoluminescence (PL) characteristics of these layers is studied as a function of various growth parameters, such as the growth temperature, oxygen flow rate and Zn flux, which suggest that the origin of the broad visible luminescence (VL), which peaks at 2.45 eV, is the transition between the conduction band and the Zn vacancy acceptor states. A bound excitonic transition observed at 3.32 eV in low temperature PL has been identified as an exciton bound to the neutral Zn vacancy. Our study also reveals the involvement of two activation processes in the dynamics of VL, which has been explained in terms of the fluctuation of the capture barrier height for the holes trapped in Zn vacancy acceptors. The fluctuation, which might be a result of the inhomogeneous distribution of Zn vacancies, is found to be associated with an average height of 7 and 90 meV, respectively, for the local and global maxima. (paper)

  6. Effects of Rapid Thermal Annealing on the Structural, Electrical, and Optical Properties of Zr-Doped ZnO Thin Films Grown by Atomic Layer Deposition

    Directory of Open Access Journals (Sweden)

    Jingjin Wu

    2016-08-01

    Full Text Available The 4 at. % zirconium-doped zinc oxide (ZnO:Zr films grown by atomic layer deposition (ALD were annealed at various temperatures ranging from 350 to 950 °C. The structural, electrical, and optical properties of rapid thermal annealing (RTA treated ZnO:Zr films have been evaluated to find out the stability limit. It was found that the grain size increased at 350 °C and decreased between 350 and 850 °C, while creeping up again at 850 °C. UV–vis characterization shows that the optical band gap shifts towards larger wavelengths. The Hall measurement shows that the resistivity almost keeps constant at low annealing temperatures, and increases rapidly after treatment at 750 °C due to the effect of both the carrier concentration and the Hall mobility. The best annealing temperature is found in the range of 350–550 °C. The ZnO:Zr film-coated glass substrates show good optical and electrical performance up to 550 °C during superstrate thin film solar cell deposition.

  7. 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.

  8. On quantum efficiency of photoluminescence in ZnO layers and nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Reshchikov, M.A., E-mail: mreshchi@vcu.ed [Physics Department, Virginia Commonwealth University, 701 W. Grace St., Richmond, VA 23284 (United States); El-Shaer, A.; Behrends, A.; Bakin, A.; Waag, A. [Institute of Semiconductor Technology, Technical University of Braunschweig, Braunschweig D-38106 (Germany)

    2009-12-15

    In this work we studied PL in ZnO layers and nanostructures, including ZnO homoepitaxial layers on ZnO substrate and ZnO-Zn{sub 1-x}Mg{sub x}O single quantum well (SQW) structures grown on sapphire substrates by MBE, and ZnO nanowires grown on sapphire by MOCVD. The external quantum efficiency (QE) of PL in O-face ZnO layers exceeded that in Zn-face ZnO layers by two orders of magnitude at low temperatures. In a sample with SQW the combined external QE from the 4.6-nm-wide SQW and 50-nm-thick Zn{sub 1-x}Mg{sub x}O barriers achieved 28% at 15 K. The highest external QE was observed in one of the samples with ZnO nanowires-52% at 15 K and 2% at 300 K. Contribution of defect-related PL bands in ZnO nanowires samples was extremely low.

  9. Photosensitivity of nanocrystalline ZnO films grown by PLD

    International Nuclear Information System (INIS)

    Ayouchi, R.; Bentes, L.; Casteleiro, C.; Conde, O.; Marques, C.P.; Alves, E.; Moutinho, A.M.C.; Marques, H.P.; Teodoro, O.; Schwarz, R.

    2009-01-01

    We have studied the properties of ZnO thin films grown by laser ablation of ZnO targets on (0 0 0 1) sapphire (Al 2 O 3 ), under substrate temperatures around 400 deg. C. The films were characterized by different methods including X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and atomic force microscopy (AFM). XPS analysis revealed that the films are oxygen deficient, and XRD analysis with θ-2θ scans and rocking curves indicate that the ZnO thin films are highly c-axis oriented. All the films are ultraviolet (UV) sensitive. Sensitivity is maximum for the films deposited at lower temperature. The films deposited at higher temperatures show crystallite sizes of typically 500 nm, a high dark current and minimum photoresponse. In all films we observe persistent photoconductivity decay. More densely packed crystallites and a faster decay in photocurrent is observed for films deposited at lower temperature

  10. Structural and optical properties of pentacene films grown on differently oriented ZnO surfaces

    International Nuclear Information System (INIS)

    El Helou, M; Lietke, E; Helzel, J; Heimbrodt, W; Witte, G

    2012-01-01

    Pentacene films have been grown on two polar zinc oxide surfaces, i.e., ZnO(0001) and ZnO(0 0 0 1-bar ), as well as on the mixed-terminated ZnO(1 0 1-bar 0) and are characterized by means of atomic force microscopy (AFM), x-ray diffraction (XRD), and thermal desorption spectroscopy (TDS). In all cases, pentacene aggregates in an upright orientation without any evidence for the formation of an interface stabilized wetting layer. Additional films deposited on a highly-defective, oxygen-depleted ZnO(0 0 0 1-bar ) reveal no altered growth mode. Nearly identical optical absorption spectra have been measured for all films, thus corroborating a weak molecule-substrate interaction. Upon cooling, however, a slightly different relaxation behavior could be resolved for pentacene films on polar ZnO surfaces compared to pentacene on the mixed-terminated ZnO(1 0 1-bar 0) surface.

  11. Study of annealing effect on the growth of ZnO nanorods on ZnO seed layers

    Science.gov (United States)

    Sannakashappanavar, Basavaraj S.; Pattanashetti, Nandini A.; Byrareddy, C. R.; Yadav, Aniruddh Bahadur

    2018-04-01

    A zinc oxide (ZnO) seed layer was deposited on the SiO2/Si substrate by RF sputtering. To study the effect of annealing, the seed layers were classified into annealed and unannealed thin films. Annealing of the seed layers was carried at 450°C. Surface morphology of the seed layers were studied by Atomic force microscopy. ZnO nanorods were then grown on both the types of seed layer by hydrothermal method. The morphology and the structural properties of the nanorods were characterized by X-ray diffraction and Scanning electron microscopy. The effect of seed layer annealing on the growth and orientation of the ZnO nanorods were clearly examined on comparing with the nanorods grown on unannealed seed layer. The nanorods grown on annealed seed layers were found to be well aligned and oriented. Further, the I-V characteristic study was carried out on these aligned nanorods. The results supports positively for the future work to further enhance the properties of developed nanorods for their wide applications in electronic and optoelectronic devices.

  12. Performance of inverted polymer solar cells with randomly oriented ZnO nanorods coupled with atomic layer deposited ZnO

    International Nuclear Information System (INIS)

    Zafar, Muhammad; Yun, Ju-Young; Kim, Do-Heyoung

    2017-01-01

    Highlights: • Hydrothermally grown, randomly oriented, and low areal density ZnO nanorods have been successfully adopted as the electron transport layer in inverted organic solar cells. • The addition of atomic layer deposited ZnO on the ZnO nanorods effectively enhance the photovoltaic performances of inverted organic solar cells. • The inverted organic solar cells with 5 nm thick-ALD ZnO showed the highest power conversion efficiency of 3.08%, which is an enhancement of approximately 80% compared to the cells without the ALD ZnO layer (PCE = 1.67%). - Abstract: Nanostructuring of the electron transport layer (ETL) in organic photovoltaic cells (OPV) is of great interest because it increases the surface area of the cell and electron transport. In this work, hydrothermally grown, randomly oriented, and low areal density ZnO nanorods (NRs) have been adopted as the ETL, and the effect of adding atomic layer deposited (ALD) ZnO on the ZnO NRs on the inverted organic solar cell performance has been investigated. The fabricated inverted organic solar cell with 5-nm-thick ALD-ZnO grown on the ZnO NRs showed the highest power conversion efficiency (PCE) of 3.08%, which is an enhancement of 85% from that of the cell without ALD-ZnO (PCE = 1.67%). The ultrathin ALD-ZnO was found to act as a curing layer of the surface defects on the hydrothermally grown ZnO NRs, resulting in an improvement in photovoltaic performance.

  13. Performance of inverted polymer solar cells with randomly oriented ZnO nanorods coupled with atomic layer deposited ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Zafar, Muhammad [School of Chemical Engineering, Chonnam National University, 300 Youngbong-dong, Gwangju 500-757 (Korea, Republic of); Yun, Ju-Young [Center for Vacuum, Korea Research Institute of Standards and Science, 267 Gajeong-ro, Daejeon 305-600 (Korea, Republic of); Kim, Do-Heyoung, E-mail: kdhh@chonnam.ac.kr [School of Chemical Engineering, Chonnam National University, 300 Youngbong-dong, Gwangju 500-757 (Korea, Republic of)

    2017-03-15

    Highlights: • Hydrothermally grown, randomly oriented, and low areal density ZnO nanorods have been successfully adopted as the electron transport layer in inverted organic solar cells. • The addition of atomic layer deposited ZnO on the ZnO nanorods effectively enhance the photovoltaic performances of inverted organic solar cells. • The inverted organic solar cells with 5 nm thick-ALD ZnO showed the highest power conversion efficiency of 3.08%, which is an enhancement of approximately 80% compared to the cells without the ALD ZnO layer (PCE = 1.67%). - Abstract: Nanostructuring of the electron transport layer (ETL) in organic photovoltaic cells (OPV) is of great interest because it increases the surface area of the cell and electron transport. In this work, hydrothermally grown, randomly oriented, and low areal density ZnO nanorods (NRs) have been adopted as the ETL, and the effect of adding atomic layer deposited (ALD) ZnO on the ZnO NRs on the inverted organic solar cell performance has been investigated. The fabricated inverted organic solar cell with 5-nm-thick ALD-ZnO grown on the ZnO NRs showed the highest power conversion efficiency (PCE) of 3.08%, which is an enhancement of 85% from that of the cell without ALD-ZnO (PCE = 1.67%). The ultrathin ALD-ZnO was found to act as a curing layer of the surface defects on the hydrothermally grown ZnO NRs, resulting in an improvement in photovoltaic performance.

  14. 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.

  15. 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.

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

    KAUST Repository

    Kim, Hyunho

    2017-02-27

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

  17. Exploring the potential of laser assisted flow deposition grown ZnO for photovoltaic applications

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, J., E-mail: joana.catarina@ua.pt [Departamento de Física & I3N, Universidade de Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro (Portugal); Cerqueira, A.F.R.; Sousa, M.G.; Santos, N.F. [Departamento de Física & I3N, Universidade de Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro (Portugal); Pimentel, A.; Fortunato, E. [CENIMAT/I3N, Departamento de Ciência dos Materiais, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Cunha, A.F. da; Monteiro, T.; Costa, F.M. [Departamento de Física & I3N, Universidade de Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro (Portugal)

    2016-07-01

    Zinc oxide (ZnO) is a widely studied wide band gap semiconductor with applications in several fields, namely to enhance solar cells efficiency. Its ability to be grown in a wide variety of nanostructured morphologies, allowing the designing of the surface area architecture constitutes an important advantage over other semiconductors. Laser assisted flow deposition (LAFD) is a recently developed growth method, based on a vapour-solid mechanism, which proved to be a powerful approach in the production of ZnO micro/nanostructures with different morphologies as well as high crystallinity and optical quality. In the present work we report the use of the LAFD technique to grow functional ZnO nanostructures (nanoparticles and tetrapods) working as nano templates to improve the dye-sensitized solar cells (DSSCs) efficiency. The structural and morphological characterization of the as-grown ZnO crystals were performed by X-ray diffraction and electron microscopy, respectively, and the optical quality was assessed by photoluminescence spectroscopy. DSSCs were produced using a combination of these nanostructures, which were subsequently sensitized with N719 dye. An efficiency of ∼3% was achieved under simulated AM 1.5 illumination conditions for a dye loading time of 1 h. - Highlights: • Laser assisted flow deposition proved to be an efficient technique to produce high quality ZnO. • Active layer formed by an interconnected network of tetrapods and a small amount of nanoparticles. • Efficiency of ∼3% obtained under simulated AM 1.5 illumination conditions.

  18. Crystallographic tilt and in-plane anisotropies of an a-plane InGaN/GaN layered structure grown by MOCVD on r-plane sapphire using a ZnO buffer

    International Nuclear Information System (INIS)

    Liu, H F; Chi, D Z; Liu, W; Guo, S

    2016-01-01

    High-resolution x-ray diffraction (HRXRD) was used to investigate the crystallographic tilts and structural anisotropies in epitaxial nonpolar a-plane InGaN/GaN grown by metal–organic chemical vapor deposition on r-plane sapphire using a ZnO buffer. The substrate had an unintentional miscut of 0.14° towards its [–4 2 2 3] axis. However, HRXRD revealed a tilt of 0.26° (0.20°) between the ZnO (GaN) (11-20) and the Al 2 O 3 (1-102) atomic planes, with the (11-20) axis of ZnO (GaN) tilted towards its c-axis, which has a difference of 163° in azimuth from that of the substrate’s miscut. Excess broadenings in the GaN/ZnO (11-20) rocking curves (RCs) were observed along its c-axis. Specific analyses revealed that partial dislocations and anisotropic in-plane strains, rather than surface-related effects, wafer curvature or stacking faults, are the dominant factors for the structural anisotropy. The orientation of the partial dislocations is most likely affected by the miscut of the substrate, e.g. via tilting of the misfit dislocation gliding planes created during island coalescences. Their Burgers vector components in the growth direction, in turn, gave rise to crystallographic tilts in the same direction as that of the excess RC-broadenings. (paper)

  19. Crystallographic tilt and in-plane anisotropies of an a-plane InGaN/GaN layered structure grown by MOCVD on r-plane sapphire using a ZnO buffer

    Science.gov (United States)

    Liu, H. F.; Liu, W.; Guo, S.; Chi, D. Z.

    2016-03-01

    High-resolution x-ray diffraction (HRXRD) was used to investigate the crystallographic tilts and structural anisotropies in epitaxial nonpolar a-plane InGaN/GaN grown by metal-organic chemical vapor deposition on r-plane sapphire using a ZnO buffer. The substrate had an unintentional miscut of 0.14° towards its [-4 2 2 3] axis. However, HRXRD revealed a tilt of 0.26° (0.20°) between the ZnO (GaN) (11-20) and the Al2O3 (1-102) atomic planes, with the (11-20) axis of ZnO (GaN) tilted towards its c-axis, which has a difference of 163° in azimuth from that of the substrate’s miscut. Excess broadenings in the GaN/ZnO (11-20) rocking curves (RCs) were observed along its c-axis. Specific analyses revealed that partial dislocations and anisotropic in-plane strains, rather than surface-related effects, wafer curvature or stacking faults, are the dominant factors for the structural anisotropy. The orientation of the partial dislocations is most likely affected by the miscut of the substrate, e.g. via tilting of the misfit dislocation gliding planes created during island coalescences. Their Burgers vector components in the growth direction, in turn, gave rise to crystallographic tilts in the same direction as that of the excess RC-broadenings.

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

    International Nuclear Information System (INIS)

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

    2013-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-01-15

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

  2. Point defects in ZnO crystals grown by various techniques

    International Nuclear Information System (INIS)

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

    2017-01-01

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

  3. Structural and interfacial defects in c-axis oriented LiNbO{sub 3} thin films grown by pulsed laser deposition on Si using Al : ZnO conducting layer

    Energy Technology Data Exchange (ETDEWEB)

    Shandilya, Swati; Sreenivas, K; Gupta, Vinay [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India); Tomar, Monika [Miranda House, University of Delhi, Delhi 110007 (India)

    2009-05-07

    Highly c-axis oriented LiNbO{sub 3} films are deposited using pulsed laser deposition on a silicon substrate using a transparent conducting Al doped ZnO layer. X-ray diffraction and Raman spectroscopic analysis show the fabrication of single phase and oriented LiNbO{sub 3} films under the optimized deposition condition. An extra peak at 905 cm{sup -1} was observed in the Raman spectra of LiNbO{sub 3} film deposited at higher substrate temperature and higher oxygen pressure, and attributed to the presence of niobium antisite defects in the lattice. Dielectric constant and ac conductivity of oriented LiNbO{sub 3} films deposited under the static and rotating substrate modes have been studied. Films deposited under the rotating substrate mode exhibit dielectric properties close to the LiNbO{sub 3} single crystal. The cause of deviation in the dielectric properties of the film deposited under the static substrate mode, in comparison with the bulk, are discussed in the light of the possible formation of an interdiffusion layer at the interface of the LiNbO{sub 3} film and the Al : ZnO layer.

  4. Structural and interfacial defects in c-axis oriented LiNbO3 thin films grown by pulsed laser deposition on Si using Al : ZnO conducting layer

    International Nuclear Information System (INIS)

    Shandilya, Swati; Sreenivas, K; Gupta, Vinay; Tomar, Monika

    2009-01-01

    Highly c-axis oriented LiNbO 3 films are deposited using pulsed laser deposition on a silicon substrate using a transparent conducting Al doped ZnO layer. X-ray diffraction and Raman spectroscopic analysis show the fabrication of single phase and oriented LiNbO 3 films under the optimized deposition condition. An extra peak at 905 cm -1 was observed in the Raman spectra of LiNbO 3 film deposited at higher substrate temperature and higher oxygen pressure, and attributed to the presence of niobium antisite defects in the lattice. Dielectric constant and ac conductivity of oriented LiNbO 3 films deposited under the static and rotating substrate modes have been studied. Films deposited under the rotating substrate mode exhibit dielectric properties close to the LiNbO 3 single crystal. The cause of deviation in the dielectric properties of the film deposited under the static substrate mode, in comparison with the bulk, are discussed in the light of the possible formation of an interdiffusion layer at the interface of the LiNbO 3 film and the Al : ZnO layer.

  5. Structural and interfacial defects in c-axis oriented LiNbO3 thin films grown by pulsed laser deposition on Si using Al : ZnO conducting layer

    Science.gov (United States)

    Shandilya, Swati; Tomar, Monika; Sreenivas, K.; Gupta, Vinay

    2009-05-01

    Highly c-axis oriented LiNbO3 films are deposited using pulsed laser deposition on a silicon substrate using a transparent conducting Al doped ZnO layer. X-ray diffraction and Raman spectroscopic analysis show the fabrication of single phase and oriented LiNbO3 films under the optimized deposition condition. An extra peak at 905 cm-1 was observed in the Raman spectra of LiNbO3 film deposited at higher substrate temperature and higher oxygen pressure, and attributed to the presence of niobium antisite defects in the lattice. Dielectric constant and ac conductivity of oriented LiNbO3 films deposited under the static and rotating substrate modes have been studied. Films deposited under the rotating substrate mode exhibit dielectric properties close to the LiNbO3 single crystal. The cause of deviation in the dielectric properties of the film deposited under the static substrate mode, in comparison with the bulk, are discussed in the light of the possible formation of an interdiffusion layer at the interface of the LiNbO3 film and the Al : ZnO layer.

  6. ZnO homoepitaxy on the O polar face of hydrothermal and melt-grown substrates by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, D.J. [Nanovation SARL, Orsay (France); Technical Univ. of Troyes (France); CNRS, Troyes (France); Hosseini Teherani, F. [Nanovation SARL, Orsay (France); Largeteau, A.; Demazeau, G. [ICMCB-CNRS, Bordeaux 1 University (Science and Technology), Pessac (France); Moisson, C.; Turover, D. [Novasic, Savoie Technolac, Arche Bat. 4, BP 267, Le Bourget du Lac (France); Nause, J. [Cermet Inc., Atlanta, GA (United States); Garry, G. [Thales Research, Domaine de Corbeville, Orsay (France); Kling, R.; Gruber, T. [Ulm University, Department of Semiconductor Physics, Ulm (Germany); Waag, A. [Braunschweig Technical University, Institute of Semiconductor Technology, Braunschweig (Germany); Jomard, F.; Galtier, P.; Lusson, A. [LPSC-CNRS, Meudon (France); Monteiro, T.; Soares, M.J.; Neves, A.; Carmo, M.C.; Peres, M. [University of Aveiro, Physics Department, Aveiro (Portugal); Lerondel, G.; Hubert, C. [Technical University of Troyes-CNRS (FRE2671), 12 rue Marie Curie, BP 2060, Troyes (France)

    2007-07-15

    2 cm diameter hydrothermal ZnO crystals were grown and then made into substrates using both mechanical and chemical-mechanical polishing (CMP). CMP polishing showed superior results with an (0002) {omega} scan full width half maximum (FWHM) of 67 arcsec and an root mean square (RMS) roughness of 2 Aa. In comparison, commercial melt-grown substrates exhibited broader X-ray diffraction (XRD) linewidths with evidence of sub-surface crystal damage due to polishing, including a downward shift of c-lattice parameter. Secondary ion mass spectroscopy revealed strong Li, Fe, Co, Al and Si contamination in the hydrothermal crystals as opposed to the melt-grown substrates, for which glow discharge mass spectroscopy studies had reported high levels of Pb, Fe, Cd and Si. Low temperature photoluminescence (PL) studies indicated that the hydrothermal crystal had high defect and/or impurity concentrations compared with the melt-grown substrate. The dominant bound exciton for the melt-grown substrate was indexed to Al. ZnO films were grown using pulsed laser deposition. The melt-grown substrates gave superior results with XRD (0002) {omega} and 2{theta}/{omega} WHM of 124 and 34 arcsec, respectively. Atomic force microscope measurements indicated a low RMS roughness (1.9 nm) as confirmed by fringes in the XRD 2{theta}/{omega} scan. It was suggested that the improvement in XRD response relative to the substrate might be due to ''healing'' of sub-surface polishing damage due to the elevated T{sub s} used for the growth. Indeed the c-lattice parameter for the homoepitaxial layer on the melt-grown substrate had become that which would be expected for strain-free ZnO. Furthermore, the stability of the PL peak positions relative to bulk ZnO, confirmed that the films appear practically strain free. (orig.)

  7. CBE growth of high-quality ZnO epitaxial layers

    Energy Technology Data Exchange (ETDEWEB)

    El-Shaer, A.; Bakin, A.; Mofor, A.C.; Kreye, M.; Waag, A. [Institute of Semiconductor Technology, Technical University Braunschweig, Hans-Sommer-Strasse 66, 38106 Braunschweig (Germany); Blaesing, J.; Krost, A. [Institute of Experimental Physics, Otto-von-Guericke-University Magdeburg (Germany); Stoimenos, J. [Physics Department, Aristotele University, Univ. Campus, 54006 Thessaloniki (Greece); Pecz, B. [Research Institute for Technical Physics and Materials Science, Hungarian Academy of Sciences, P.O. Box 49, 1525 Budapest (Hungary); Heuken, M. [Aixtron AG, Kackertstr. 15-17, 52072 Aachen (Germany)

    2006-03-15

    Further improvements on the recently reported novel approach to zinc oxide Chemical Beam Epitaxy (CBE) are presented. Hydrogen peroxide is employed as a very efficient novel oxidant. ZnO layers with a thickness from 100 nm to 600 nm were grown on c-sapphire using a MgO buffer. PL-mapping as well as conductivity mapping shows a good uniformity across the 2 inch ZnO-on-sapphire epiwafers. The measured surface roughness for the best layers is as low as 0.26 nm. HRXRD measurements of the obtained ZnO layers show excellent quality of the single crystalline ZnO. The FWHM of the HRXRD (0002) rocking curves measured for the 2 inch ZnO-on-sapphire wafers is as low as 27 arcsec with a very high lateral homogeneity across the whole wafer. Plane view HRTEM observations reveal the very good quality of the ZnO films. The results indicate that CBE is a suitable technique to fabricate ZnO of very high structural quality, which can eventually be used as an alternative to bulk ZnO substrates. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Hydrophobic ZnO nanostructured thin films on glass substrate by simple successive ionic layer absorption and reaction (SILAR) method

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, P. Suresh; Raj, A. Dhayal [Thin Film and Nanomaterials Laboratory, Department of Physics, Bharathiar University, Coimbatore-641046 (India); Mangalaraj, D., E-mail: dmraj800@yahoo.co [Department of Nanoscience and Technology, Bharathiar University, Coimbatore-641046 (India); Nataraj, D. [Thin Film and Nanomaterials Laboratory, Department of Physics, Bharathiar University, Coimbatore-641046 (India)

    2010-10-01

    In the present work, ZnO nanostructured thin films were grown on glass substrates by a simple successive ionic layer absorption and reaction method (SILAR) process at relatively low temperature for its self cleaning application. X-ray diffraction, scanning electron microscopy and Photoluminescence (PL) spectra were used to characterize the prepared ZnO nanostructured film. XRD pattern clearly reviles that the grown ZnO nanostructure film reflect (002) orientation with c-direction. SEM image clearly shows the surface morphology with cluster of spindle and flower-like nanostructured with diameter various around 350 nm. Photoluminescence (PL) spectra of ZnO nanostructures film exhibit a UV emission around 385nm and visible emission in the range around 420-500 nm. Good water repellent behavior were observed for ZnO nanostructured film without any surface modification.

  9. Hydrophobic ZnO nanostructured thin films on glass substrate by simple successive ionic layer absorption and reaction (SILAR) method

    International Nuclear Information System (INIS)

    Kumar, P. Suresh; Raj, A. Dhayal; Mangalaraj, D.; Nataraj, D.

    2010-01-01

    In the present work, ZnO nanostructured thin films were grown on glass substrates by a simple successive ionic layer absorption and reaction method (SILAR) process at relatively low temperature for its self cleaning application. X-ray diffraction, scanning electron microscopy and Photoluminescence (PL) spectra were used to characterize the prepared ZnO nanostructured film. XRD pattern clearly reviles that the grown ZnO nanostructure film reflect (002) orientation with c-direction. SEM image clearly shows the surface morphology with cluster of spindle and flower-like nanostructured with diameter various around 350 nm. Photoluminescence (PL) spectra of ZnO nanostructures film exhibit a UV emission around 385nm and visible emission in the range around 420-500 nm. Good water repellent behavior were observed for ZnO nanostructured film without any surface modification.

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

    Indian Academy of Sciences (India)

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

  11. A comparative study of physico-chemical properties of CBD and SILAR grown ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Jambure, S.B.; Patil, S.J.; Deshpande, A.R.; Lokhande, C.D., E-mail: l_chandrakant@yahoo.com

    2014-01-01

    Graphical abstract: Schematic model indicating ZnO nanorods by CBD (Z{sub 1}) and nanograins by SILAR (Z{sub 2}). - Highlights: • Simple methods for the synthesis of ZnO thin films. • Comparative study of physico-chemical properties of ZnO thin films prepared by CBD and SILAR methods. • CBD outperforms SILAR method. - Abstract: In the present work, nanocrystalline zinc oxide (ZnO) thin films have been successfully deposited onto glass substrates by simple and economical chemical bath deposition (CBD) and successive ionic layer adsorption reaction (SILAR) methods. These films were further characterized for their structural, optical, surface morphological and wettability properties. The X-ray diffraction (XRD) patterns for both CBD and SILAR deposited ZnO thin films reveal the highly crystalline hexagonal wurtzite structure. From optical studies, band gaps obtained are 2.9 and 3.0 eV for CBD and SILAR deposited thin films, respectively. The scanning electron microscope (SEM) patterns show growth of well defined randomly oriented nanorods and nanograins on the CBD and SILAR deposited samples, respectively. The resistivity of CBD deposited films (10{sup 2} Ω cm) is lower than that of SILAR deposited films (10{sup 5} Ω cm). Surface wettability studies show hydrophobic nature for both films. From the above results it can be concluded that CBD grown ZnO thin films show better properties as compared to SILAR method.

  12. A comparative study of physico-chemical properties of CBD and SILAR grown ZnO thin films

    International Nuclear Information System (INIS)

    Jambure, S.B.; Patil, S.J.; Deshpande, A.R.; Lokhande, C.D.

    2014-01-01

    Graphical abstract: Schematic model indicating ZnO nanorods by CBD (Z 1 ) and nanograins by SILAR (Z 2 ). - Highlights: • Simple methods for the synthesis of ZnO thin films. • Comparative study of physico-chemical properties of ZnO thin films prepared by CBD and SILAR methods. • CBD outperforms SILAR method. - Abstract: In the present work, nanocrystalline zinc oxide (ZnO) thin films have been successfully deposited onto glass substrates by simple and economical chemical bath deposition (CBD) and successive ionic layer adsorption reaction (SILAR) methods. These films were further characterized for their structural, optical, surface morphological and wettability properties. The X-ray diffraction (XRD) patterns for both CBD and SILAR deposited ZnO thin films reveal the highly crystalline hexagonal wurtzite structure. From optical studies, band gaps obtained are 2.9 and 3.0 eV for CBD and SILAR deposited thin films, respectively. The scanning electron microscope (SEM) patterns show growth of well defined randomly oriented nanorods and nanograins on the CBD and SILAR deposited samples, respectively. The resistivity of CBD deposited films (10 2 Ω cm) is lower than that of SILAR deposited films (10 5 Ω cm). Surface wettability studies show hydrophobic nature for both films. From the above results it can be concluded that CBD grown ZnO thin films show better properties as compared to SILAR method

  13. Influence of substrate temperature and Zn-precursors on atomic layer deposition of polycrystalline ZnO films on glass

    International Nuclear Information System (INIS)

    Makino, Hisao; Miyake, Aki; Yamada, Takahiro; Yamamoto, Naoki; Yamamoto, Tetsuya

    2009-01-01

    Influence of substrate temperature and Zn-precursors on growth rate, crystal structure, and electrical property of undoped ZnO thin films grown by atomic layer deposition (ALD) have been studied. Differences between dimethylzinc (DMeZn) and diethylzinc (DEtZn) used as Zn-precursors were examined. The ZnO films grown using DMeZn showed higher electrical resistivity compared to that grown using DEtZn. However, the higher resistivity in the case of DMeZn was owing to much amount of residual impurities incorporated during the ALD growth

  14. Characterization of ZnO thin films grown on different p-Si substrate elaborated by solgel spin-coating method

    Energy Technology Data Exchange (ETDEWEB)

    Chebil, W., E-mail: Chbil.widad@live.fr [Laboratoire Physico-chimie des Matériaux, Unité de Service Commun de Recherche “High resolution X-ray diffractometer”, Département de Physique, Université de Monastir, Faculté des Sciences de Monastir, Avenue de l’Environnement, 5019 Monastir (Tunisia); Fouzri, A. [Laboratoire Physico-chimie des Matériaux, Unité de Service Commun de Recherche “High resolution X-ray diffractometer”, Département de Physique, Université de Monastir, Faculté des Sciences de Monastir, Avenue de l’Environnement, 5019 Monastir (Tunisia); Institut Supérieur des Sciences Appliquées et de Technologie de Sousse, Université de Sousse (Tunisia); Fargi, A. [Laboratoire de Microélectronique et Instrumentation, Faculté des Sciences de Monastir, Université de Monastir, Avenue de l’environnement, 5019 Monastir (Tunisia); Azeza, B.; Zaaboub, Z. [Laboratoire Micro-Optoélectroniques et Nanostructures, Faculté des Sciences de Monastir, Université de Monastir, Avenue de l' environnement, 5019 Monastir (Tunisia); and others

    2015-10-15

    Highlights: • High quality ZnO thin films grown on different p-Si substrates were successful obtained by sol–gel process. • PL measurement revealed that ZnO thin film grown on porous Si has the better optical quality. • I–V characteristics for all heterojunctions exhibit successful diode formation. • The diode ZnO/PSi shows a better photovoltaic effect under illumination with a maximum {sub Voc} of 0.2 V. - Abstract: In this study, ZnO thin films are deposited by sol–gel technique on p-type crystalline silicon (Si) with [100] orientation, etched silicon and porous silicon. The structural analyses showed that the obtained thin films were polycrystalline with a hexagonal wurtzite structure and preferentially oriented along the c-axis direction. Morphological study revealed the presence of rounded and facetted grains irregularly distributed on the surface of all samples. PL spectra at room temperature revealed that ZnO thin film grown on porous Si has a strong UV emission with low defects in the visible region comparing with ZnO grown on plat Si and etched Si surface. The heterojunction parameters were evaluated from the (I–V) under dark and illumination at room temperature. The ideality factor, barrier height and series resistance of heterojunction grown on different p-Si substrates are determined by using different methods. Best electrical properties are obtained for ZnO layer deposited on porous silicon.

  15. Epitaxial growth of ZnO layers on (111) GaAs substrates by laser molecular beam epitaxy

    International Nuclear Information System (INIS)

    Ding Jian; Zhang Di; Konomi, Takaharu; Saito, Katsuhiko; Guo Qixin

    2012-01-01

    ZnO layers were grown on (111) GaAs substrates by laser molecular epitaxy at substrate temperatures between 200 and 550 °C. X-ray diffraction analysis revealed that c-axis of ZnO epilayer with a wurtzite structure is perpendicular to the substrate surface. X-ray rocking curves and Raman spectroscopy showed that the crystal quality of ZnO epilayers depends on the substrate temperature during the growth. Strong near-band-edge emission in the UV region without any deep-level emissions was observed from the ZnO epilayers at room temperature. The results indicate that laser molecular beam epitaxy is a promising growth method for obtaining high-quality ZnO layers on (111) GaAs substrates.

  16. Implementation of ZnO/ZnMgO strained-layer superlattice for ZnO heteroepitaxial growth on sapphire

    Science.gov (United States)

    Petukhov, Vladimir; Bakin, Andrey; Tsiaoussis, Ioannis; Rothman, Johan; Ivanov, Sergey; Stoemenos, John; Waag, Andreas

    2011-05-01

    The main challenge in fabrication of ZnO-based devices is the absence of reliable p-type material. This is mostly caused by insufficient crystalline quality of the material and not well-enough-developed native point defect control of ZnO. At present high-quality ZnO wafers are still expensive and ZnO heteroepitaxial layers on sapphire are the most reasonable alternative to homoepitaxial layers. But it is still necessary to improve the crystalline quality of the heteroepitaxial layers. One of the approaches to reduce defect density in heteroepitaxial layers is to introduce a strained-layer superlattice (SL) that could stop dislocation propagation from the substrate-layer interface. In the present paper we have employed fifteen periods of a highly strained SL structure. The structure was grown on a conventional double buffer layer comprising of high-temperature MgO/low-temperature ZnO on sapphire. The influence of the SLs on the properties of the heteroepitaxial ZnO layers is investigated. Electrical measurements of the structure with SL revealed very high values of the carrier mobility up to 210 cm2/Vs at room temperature. Structural characterization of the obtained samples showed that the dislocation density in the following ZnO layer was not reduced. The high mobility signal appears to come from the SL structure or the SL/ZnO interface.

  17. Structural characterization of ZnO films grown by molecular beam epitaxy on sapphire with MgO buffer

    International Nuclear Information System (INIS)

    Pecz, B.; El-Shaer, A.; Bakin, A.; Mofor, A.-C.; Waag, A.; Stoemenos, J.

    2006-01-01

    The structural characteristics of the ZnO film grown on sapphire substrate using a thin MgO buffer layer were studied using transmission electron microscopy and high-resolution x-ray diffraction. The growth was carried out in a modified plasma-molecular beam epitaxy system. The observed misfit dislocations were well confined at the sapphire overgrown interface exhibiting domain matching epitaxy, where the integral multiples of lattice constants match across the interface. The main extended defects in the ZnO film were the threading dislocations having a mean density of 4x10 9 cm -2 . The formation of the MgO buffer layer as well as the ZnO growth were monitored in situ by reflection high-energy electron diffraction. The very thin ∼1 nm, MgO buffer layer can partially interdiffuse with the ZnO as well as react with the Al 2 O 3 substrate forming an intermediate epitaxial layer having the spinel (MgO/Al 2 O 3 ) structure

  18. 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.

  19. A Systematic Study of the Relationship among the Morphological, Structural and Photoelectrochemical Properties of ZnO Nanorods Grown Using the Microwave Chemical Bath Deposition Method

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Sungjin; Ryu, Hyukhyun [Inje University, Gimhae (Korea, Republic of); Lee, Won-Jae [Dong-Eui University, Busan (Korea, Republic of)

    2017-08-15

    In this study, zinc oxide (ZnO) nanostructures were grown on a ZnO seed layer/fluorine-doped tin oxide (FTO) substrate for different growth durations ranging from 5 to 40 min using the microwave chemical bath deposition method. We studied the effect of growth duration on the morphological, structural, optical and photoelectrochemical properties of the ZnO nanostructures. From this study, we found that the photoelectrochemical properties of the ZnO nanostructures were largely affected by their morphological and structural properties. As a result, we obtained the highest photocurrent density of 0.46 mA/cm{sup 2} (at 1.5 V vs. SCE) from the sample grown for 30 min.

  20. Counting molecular-beam grown graphene layers

    Energy Technology Data Exchange (ETDEWEB)

    Plaut, Annette S. [School of Physics, University of Exeter, Exeter EX4 4QL (United Kingdom); Wurstbauer, Ulrich [Department of Physics, Columbia University, New York, New York 10027 (United States); Pinczuk, Aron [Department of Physics, Columbia University, New York, New York 10027 (United States); Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States); Garcia, Jorge M. [MBE Lab, IMM-Instituto de Microelectronica de Madrid (CNM-CSIC), Madrid, E-28760 (Spain); Pfeiffer, Loren N. [Electrical Engineering Department, Princeton University, New Jersey 08544 (United States)

    2013-06-17

    We have used the ratio of the integrated intensity of graphene's Raman G peak to that of the silicon substrate's first-order optical phonon peak, accurately to determine the number of graphene layers across our molecular-beam (MB) grown graphene films. We find that these results agree well both, with those from our own exfoliated single and few-layer graphene flakes, and with the results of Koh et al.[ACS Nano 5, 269 (2011)]. We hence distinguish regions of single-, bi-, tri-, four-layer, etc., graphene, consecutively, as we scan coarsely across our MB-grown graphene. This is the first, but crucial, step to being able to grow, by such molecular-beam-techniques, a specified number of large-area graphene layers, to order.

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

    International Nuclear Information System (INIS)

    Fay, Sylvie; Steinhauser, Jerome; Nicolay, Sylvain; Ballif, Christophe

    2010-01-01

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

  2. Control of chemical bonding of the ZnO surface grown by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Ogata, K.; Komuro, T.; Hama, K.; Koike, K.; Sasa, S.; Inoue, M.; Yano, M.

    2004-01-01

    Toward the fabrication of enzyme modified field effect transistors (EnFETs) as one of organic/inorganic hybridized structures, surface bonding of the ZnO grown by molecular beam epitaxy was controlled by ex situ treatments. Angle resolved X-ray photoelectron spectroscopy (XPS) measurement revealed that O-H bonds exist at the surface of ZnO. It was found that the number of O-H bond could be changed with reversibility using plasma and thermal treatments

  3. Characteristics of threading dislocations in ZnO grown on facet-controlled epitaxial overgrown GaN templates

    International Nuclear Information System (INIS)

    Zhou, H L; Chua, S J; Chow, S Y; Pan, H; Zhu, Y W; Feng, Y P; Wang, L S; Zang, K Y; Liu, W; Tripathy, S

    2007-01-01

    Using transmission electron microscopy (TEM), the authors have investigated the behavior of threading dislocations in ZnO selectively grown on a facet-controlled epitaxial overgrown GaN template. In this case, the ZnO is grown by a vapor transport method. The TEM study in the overgrown regions shows that all the pure-edge type dislocations in ZnO are parallel toward the mask area and vertical propagation of dislocation to the ZnO surface is minimized. Using such a selective growth technique on a faceted semi-polar GaN surface, a reduction of threading dislocation density in ZnO could be achieved

  4. VLS-grown diffusion doped ZnO nanowires and their luminescence properties

    International Nuclear Information System (INIS)

    Roy, Pushan Guha; Dutta, Amartya; Das, Arpita; Bhattacharyya, Anirban; Sen, Sayantani; Pramanik, Pallabi

    2015-01-01

    Zinc Oxide (ZnO) nanowires were deposited by vapor–liquid–solid (VLS) method on to aluminum doped ZnO (AZO) thin films grown by sol-gel technique. For various device applications, current injection into such nanowires is critical. This is expected to be more efficient for ZnO nanowires deposited on to AZO compared to those deposited on to a foreign substrate such as silicon. In this work we compare the morphological and optical properties of nanowires grown on AZO with those grown under similar conditions on silicon (Si) wafers. For nanowires grown on silicon, diameters around 44 nm with heights around 2.2 μm were obtained. For the growth on to AZO, the diameters were around 90 nm while the heights were around 520 nm. Room temperature photoluminescence (RT-PL) measurements show improved near band-edge emission for nanowires grown on to AZO, indicating higher material quality. This is further established by low temperature photoluminescence (LT-PL) measurements where excitonic transitions with width as small as 14 meV have been obtained at 4 K for such structures. Electron energy loss spectroscopy (EELS) studies indicate the presence of Al in the nanowires, indicating a new technique for introduction of dopants into these structures. These results indicate that ZnO nanowires on sol-gel grown AZO thin films show promise in the development of various optoelectronic devices. (paper)

  5. Observation of Zn vacancies in ZnO grown by chemical vapor transport

    Energy Technology Data Exchange (ETDEWEB)

    Tuomisto, F.; Saarinen, K. [Laboratory of Physics, Helsinki University of Technology, P.O. Box 1100, 02015 TKK (Finland); Grasza, K.; Mycielski, A. [Institute of Physics, Polish Academy of Sciences, Lotnikow 32/46, 02-668 Warsaw (Poland)

    2006-03-15

    We have used positron annihilation spectroscopy to study the vacancy defects in ZnO crystals grown by both the conventional and contactless chemical vapor transport (CVT and CCVT). Our results show that Zn vacancies or Zn vacancy related defects are present in as-grown ZnO, irrespective of the growth method. Zn vacancies are observed in CVT-grown undoped ZnO and (Zn,Mn)O. The Zn vacancies present in undoped CCVT-ZnO are the dominant negatively charged point defect in the material. Doping the material with As introduces also Zn vacancy-related defect complexes with larger open volume. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Photoelectrocatalytic activity of a hydrothermally grown branched Zno nanorod-array electrode for paracetamol degradation.

    Science.gov (United States)

    Lin, Chin Jung; Liao, Shu-Jun; Kao, Li-Cheng; Liou, Sofia Ya Hsuan

    2015-06-30

    Hierarchical branched ZnO nanorod (B-ZnR) arrays as an electrode for efficient photoelectrocatalytic degradation of paracetamol were grown on fluorine-doped tin oxide substrates using a solution route. The morphologic and structural studies show the ZnO trunks are single-crystalline hexagonal wurtzite ZnO with a [0001] growth direction and are densely covered by c-axis-oriented ZnO branches. The obvious enhancement in photocurrent response of the B-ZnR electrode was obtained than that in the ZnO nanoparticle (ZnO NP) electrode. For the photoelectrocatalytic degradation of paracetamol in 20 h, the conversion fraction of the drug increased from 32% over ZnO NP electrode to 62% over B-ZnR arrays with about 3-fold increase in initial reaction rate. The light intensity-dependent photoelectrocatalytic experiment indicated that the superior performance over the B-ZnR electrode was mainly ascribed to the increased specific surface area without significantly sacrificing the charge transport and pollutant diffusion efficiencies. Two aromatic intermediate compounds were observed and eventually converted into harmless carboxylic acids and ammonia. Hierarchical tree-like ZnO arrays can be considered effective alternatives to improve photoelectro degradation rates without the need for expensive additives. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. Enhanced electrical properties of dual-layer channel ZnO thin film transistors prepared by atomic layer deposition

    Science.gov (United States)

    Li, Huijin; Han, Dedong; Dong, Junchen; Yu, Wen; Liang, Yi; Luo, Zhen; Zhang, Shengdong; Zhang, Xing; Wang, Yi

    2018-05-01

    The thin film transistors (TFTs) with a dual-layer channel structure combing ZnO thin layer grown at 200 °C and ZnO film grown at 120 °C by atomic layer deposition are fabricated. The dual-layer channel TFT exhibits a low leakage current of 2.8 × 10-13 A, Ion/Ioff ratio of 3.4 × 109, saturation mobility μsat of 12 cm2 V-1 s-1, subthreshold swing (SS) of 0.25 V/decade. The SS value decreases to 0.18 V/decade after the annealing treatment in O2 due to the reduction of the trap states at the channel/dielectric interface and in the bulk channel layer. The enhanced performance obtained from the dual-layer channel TFTs is due to the ability of maintaining high mobility and suppressing the increase in the off-current at the same time.

  8. Atomic Layer Deposition of ZnO on Multi-walled Carbon Nanotubes and Its Use for Synthesis of CNT–ZnO Heterostructures

    Directory of Open Access Journals (Sweden)

    Li C

    2010-01-01

    Full Text Available Abstract In this article, direct coating of ZnO on PECVD-grown multi-walled carbon nanotubes (MWCNTs is achieved using atomic layer deposition (ALD. Transmission electron microscopy investigation shows that the deposited ZnO shell is continuous and uniform, in contrast to the previously reported particle morphology. The ZnO layer has a good crystalline quality as indicated by Raman and photoluminescence (PL measurements. We also show that such ZnO layer can be used as seed layer for subsequent hydrothermal growth of ZnO nanorods, resulting in branched CNT–inorganic hybrid nanostructures. Potentially, this method can also apply to the fabrication of ZnO-based hybrid nanostructures on other carbon nanomaterials.

  9. Monocrystalline zinc oxide films grown by atomic layer deposition

    International Nuclear Information System (INIS)

    Wachnicki, L.; Krajewski, T.; Luka, G.; Witkowski, B.; Kowalski, B.; Kopalko, K.; Domagala, J.Z.; Guziewicz, M.; Godlewski, M.; Guziewicz, E.

    2010-01-01

    In the present work we report on the monocrystalline growth of (00.1) ZnO films on GaN template by the Atomic Layer Deposition technique. The ZnO films were obtained at temperature of 300 o C using dietylzinc (DEZn) as a zinc precursor and deionized water as an oxygen precursor. High resolution X-ray diffraction analysis proves that ZnO layers are monocrystalline with rocking curve FWHM of the 00.2 peak equals to 0.07 o . Low temperature photoluminescence shows a sharp and bright excitonic line with FWHM of 13 meV.

  10. ALD grown nanostructured ZnO thin films: Effect of substrate temperature on thickness and energy band gap

    Directory of Open Access Journals (Sweden)

    Javed Iqbal

    2016-10-01

    Full Text Available Nanostructured ZnO thin films with high transparency have been grown on glass substrate by atomic layer deposition at various temperatures ranging from 100 °C to 300 °C. Efforts have been made to observe the effect of substrate temperature on the thickness of the deposited thin films and its consequences on the energy band gap. A remarkably high growth rate of 0.56 nm per cycle at a substrate temperature of 200 °C for ZnO thin films have been achieved. This is the maximum growth rate for ALD deposited ZnO thin films ever reported so far to the best of our knowledge. The studies of field emission scanning electron microscopy and X-ray diffractometry patterns confirm the deposition of uniform and high quality nanosturtured ZnO thin films which have a polycrystalline nature with preferential orientation along (100 plane. The thickness of the films deposited at different substrate temperatures was measured by ellipsometry and surface profiling system while the UV–visible and photoluminescence spectroscopy studies have been used to evaluate the optical properties of the respective thin films. It has been observed that the thickness of the thin film depends on the substrate temperatures which ultimately affect the optical and structural parameters of the thin films.

  11. Luminescence properties of hydrothermally grown ZnO nanorods

    Czech Academy of Sciences Publication Activity Database

    Yatskiv, Roman; Grym, Jan

    2016-01-01

    Roč. 99, 1November (2016), s. 214-220 ISSN 0749-6036 R&D Projects: GA MŠk(CZ) LD14111; GA ČR GA15-17044S Institutional support: RVO:67985882 Keywords : Photoluminescence * Annealing * ZnO nanorods Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 2.123, year: 2016

  12. Characterization of Non-Polar ZnO Layers with Positron Annihilation Spectroscopy

    Science.gov (United States)

    Zubiaga, A.; Tuomisto, F.; Zúñiga-Pérez, J.; Muñoz-San José, V.

    2008-11-01

    We applied positron annihilation spectroscopy to study the effect of growth polarity on the vacancy defects in ZnO grown by metal-organic vapor phase deposition on sapphire. Both c-plane and a-plane ZnO layers were measured, and Zn vacancies were identified as the dominant defects detected by positrons. The results are qualitatively similar to those of earlier experiments in GaN. The Zn vacancy concentration decreases in c-plane ZnO by almost one order of magnitude (from high 1017 cm-3 to low 1017 cm-3) when the layer thickness is increased from 0.5 to 2 μm. Interestingly, in a-plane ZnO the Zn vacancy concentration is constant at a level of about 2×1017 cm-3 in all the samples with thicknesses varying from 0.6 to 2.4 μm. The anisotropy of the Doppler broadening of the annihilation radiation parallel and perpendicular to the hexagonal c-axis was also measured.

  13. Simulation, fabrication and characterization of ZnO based thin film transistors grown by radio frequency magnetron sputtering.

    Science.gov (United States)

    Singh, Shaivalini; Chakrabarti, P

    2012-03-01

    We report the performance of the thin film transistors (TFTs) using ZnO as an active channel layer grown by radio frequency (RF) magnetron sputtering technique. The bottom gate type TFT, consists of a conventional thermally grown SiO2 as gate insulator onto p-type Si substrates. The X-ray diffraction patterns reveal that the ZnO films are preferentially orientated in the (002) plane, with the c-axis perpendicular to the substrate. A typical ZnO TFT fabricated by this method exhibits saturation field effect mobility of about 0.6134 cm2/V s, an on to off ratio of 102, an off current of 2.0 x 10(-7) A, and a threshold voltage of 3.1 V at room temperature. Simulation of this TFT is also carried out by using the commercial software modeling tool ATLAS from Silvaco-International. The simulated global characteristics of the device were compared and contrasted with those measured experimentally. The experimental results are in fairly good agreement with those obtained from simulation.

  14. Structural and optical properties of ZnO films grown on silicon and ...

    Indian Academy of Sciences (India)

    TECS

    Abstract. Photoluminescence (PL) properties of undoped ZnO thin films grown by rf magnetron sputtering on silicon .... voluted O1 s and (c) typical Zr 3d spectra of ZrO2/ZnO/Si film. .... strate doping concentration (NB) of ≈ 2⋅5 × 1015 cm–3 is.

  15. Annealing Heat Treatment of ZnO Nanoparticles Grown on Porous Si Substrate Using Spin-Coating Method

    Directory of Open Access Journals (Sweden)

    K. A. Eswar

    2014-01-01

    Full Text Available ZnO nanoparticles were successfully deposited on porous silicon (PSi substrate using spin-coating method. In order to prepare PSi, electrochemical etching was employed to modify the Si surface. Zinc acetate dihydrate was used as a starting material in ZnO sol-gel solution preparation. The postannealing treatments were investigated on morphologies and photoluminescence (PL properties of the ZnO thin films. Field emission scanning electron microscopy (FESEM results indicate that the thin films composed by ZnO nanoparticles were distributed uniformly on PSi. The average sizes of ZnO nanoparticle increase with increasing annealing temperature. Atomic force microscopic (AFM analysis reveals that ZnO thin films annealed at 500°C had the smoothest surface. PL spectra show two peaks that completely correspond to nanostructured ZnO and PSi. These findings indicate that the ZnO nanostructures grown on PSi are promising for application as light emitting devices.

  16. Comparative PL study of individual ZnO nanorods, grown by APMOCVD and CBD techniques

    Energy Technology Data Exchange (ETDEWEB)

    Khranovskyy, Volodymyr, E-mail: volkh@ifm.liu.se [Department of Physics, Chemistry and Biology (IFM), Linkoeping University, 58183 Linkoeping (Sweden); Yakimova, Rositza; Karlsson, Fredrik; Syed, Abdul S.; Holtz, Per-Olof [Department of Physics, Chemistry and Biology (IFM), Linkoeping University, 58183 Linkoeping (Sweden); Nigussa Urgessa, Zelalem [Department of Physics, P.O Box 77000, Nelson Mandela Metropolitan University, Port Elizabeth 6031 (South Africa); Samuel Oluwafemi, Oluwatobi [Department of Chemistry and Chemical Technology, Walter Sisulu University, Mthatha Campus, Private Bag XI 5117 (South Africa); Reinhardt Botha, Johannes [Department of Physics, P.O Box 77000, Nelson Mandela Metropolitan University, Port Elizabeth 6031 (South Africa)

    2012-05-15

    The photoluminescence properties of individual ZnO nanorods, grown by atmospheric pressure metalorganic chemical vapor deposition (APMOCV) and chemical bath deposition (CBD) are investigated by means of temperature dependent micro-PL. It was found that the low temperature PL spectra are driven by neutral donor bound exciton emission D{sup 0}X, peaked at 3.359 and 3.363 eV for APMOCVD and CBD ZnO nanorods, respectively. The temperature increase causes a red energy shift of the peaks and enhancement of the free excitonic emission (FX). The FX was found to dominate after 150 K for both samples. It was observed that while APMOCVD ZnO nanorods possess a constant low signal of visible deep level emission with temperature, the ZnO nanorods grown by CBD revealed the thermal activation of deep level emission (DLE) after 130 K. The resulting room temperature DLE was a wide band located at 420-550 nm. The PL properties of individual ZnO nanorods can be of importance for their forthcoming application in future optoelectronics and photonics.

  17. Comparative PL study of individual ZnO nanorods, grown by APMOCVD and CBD techniques

    International Nuclear Information System (INIS)

    Khranovskyy, Volodymyr; Yakimova, Rositza; Karlsson, Fredrik; Syed, Abdul S.; Holtz, Per-Olof; Nigussa Urgessa, Zelalem; Samuel Oluwafemi, Oluwatobi; Reinhardt Botha, Johannes

    2012-01-01

    The photoluminescence properties of individual ZnO nanorods, grown by atmospheric pressure metalorganic chemical vapor deposition (APMOCV) and chemical bath deposition (CBD) are investigated by means of temperature dependent micro-PL. It was found that the low temperature PL spectra are driven by neutral donor bound exciton emission D 0 X, peaked at 3.359 and 3.363 eV for APMOCVD and CBD ZnO nanorods, respectively. The temperature increase causes a red energy shift of the peaks and enhancement of the free excitonic emission (FX). The FX was found to dominate after 150 K for both samples. It was observed that while APMOCVD ZnO nanorods possess a constant low signal of visible deep level emission with temperature, the ZnO nanorods grown by CBD revealed the thermal activation of deep level emission (DLE) after 130 K. The resulting room temperature DLE was a wide band located at 420–550 nm. The PL properties of individual ZnO nanorods can be of importance for their forthcoming application in future optoelectronics and photonics.

  18. Sensing performances of ZnO nanostructures grown under different oxygen pressures to hydrogen

    International Nuclear Information System (INIS)

    Chu, Jin; Peng, Xiaoyan; Wang, Zhenbo; Feng, Peter

    2012-01-01

    Graphical abstract: Display Omitted Highlights: ► Surface morphology depends on the oxygen pressure. ► Structural degradation was observed for the ZnO samples when oxygen pressure was overhigh. ► The sensitivity of the ZnO-based sensors increase with grown oxygen pressure. -- Abstract: For extensive use in an industrialized process of individual ZnO nanostructures applied in gas sensors, a simple, inexpensive, and safe synthesis process is required. Here, nanostructured ZnO films were grown by a pulsed laser deposition technique under different oxygen pressures. Scanning electron microscopy images show nanopores, nanotips, and nanoparticles are obtained and energy dispersive X-ray spectroscopy data indicate oxygen concentration of the synthesized samples increases monotonously with oxygen pressure. The sensor based on ZnO with high oxygen concentration has high sensitivity, rapid response (9 s) and recovery (80 s) behavior to 500 ppm hydrogen below 150 °C. Experimental data indicate that high oxygen concentration effectively improves the sensing properties of nanostructured ZnO.

  19. Acceptor Type Vacancy Complexes In As-Grown ZnO

    International Nuclear Information System (INIS)

    Zubiaga, A.; Tuomisto, F.; Zuniga-Perez, J.

    2010-01-01

    One of the many technological areas that ZnO is interesting for is the construction of opto-electronic devices working in the blue-UV range as its large band gap (∼3.4 eV at 10 K) makes them suitable for that purpose. As-grown ZnO shows generally n-type conductivity partially due to the large concentration of unintentional shallow donors, like H, but impurities can also form complexes with acceptor type defects (Zn vacancy) leading to the creation of compensating defects. Recently, Li Zn and Na Zn acceptors have been measured and H could form similar type of defects. Doppler Broadening Positron Annihilation spectroscopy experimental results on the observation of Zn related vacancy complexes in ZnO thin films, as-grown, O implanted and Al doped will be presented. Results show that as-grown ZnO film show small Zn vacancy related complexed that could be related to presence of H as a unintentional doping element.

  20. Acceptor Type Vacancy Complexes In As-Grown ZnO

    Science.gov (United States)

    Zubiaga, A.; Tuomisto, F.; Zuñiga-Pérez, J.

    2010-11-01

    One of the many technological areas that ZnO is interesting for is the construction of opto-electronic devices working in the blue-UV range as its large band gap (˜3.4 eV at 10 K) makes them suitable for that purpose. As-grown ZnO shows generally n-type conductivity partially due to the large concentration of unintentional shallow donors, like H, but impurities can also form complexes with acceptor type defects (Zn vacancy) leading to the creation of compensating defects. Recently, LiZn and NaZn acceptors have been measured and H could form similar type of defects. Doppler Broadening Positron Annihilation spectroscopy experimental results on the observation of Zn related vacancy complexes in ZnO thin films, as-grown, O implanted and Al doped will be presented. Results show that as-grown ZnO film show small Zn vacancy related complexed that could be related to presence of H as a unintentional doping element.

  1. Atomic layer epitaxy of ZnO for applications in molecular beam epitaxy growth of GaN and InGaN

    International Nuclear Information System (INIS)

    Godlewski, M.; Szczerbakow, A.; Ivanov, V. Yu.; Barski, A.; Goldys, E.M.

    2000-01-01

    We report the successful atomic layer epitaxy growth of thin ZnO films and their use for GaN and InGaN epitaxy. The properties of ZnO epilayers, obtained by four different procedures, are analysed, as well as of GaN and InGaN films grown on ZnO-coated Si and GaAs by MBE. (author)

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

    International Nuclear Information System (INIS)

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

    2007-01-01

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

  3. ZnO nanocoral reef grown on porous silicon substrates without catalyst

    International Nuclear Information System (INIS)

    Abdulgafour, H.I.; Yam, F.K.; Hassan, Z.; AL-Heuseen, K.; Jawad, M.J.

    2011-01-01

    Research highlights: → Porous silicon (PS) technology is utilized to grow coral reef-like ZnO nanostructures on the surface of Si substrates. → Flower-like aligned ZnO nanorods are fabricated directly onto the silicon substrates through zinc powder evaporation using a simple thermal evaporation method without a catalyst for comparison. → The PL spectra show that for ZnO nanocoral reefs the UV emission shifts slightly towards lower frequency. → This non-catalyst growth technique on the rough surface of substrates may have potential applications in the fabrication of nanoelectronic and nanooptical devices. - Abstract: Porous silicon (PS) technology is utilized to grow coral reef-like ZnO nanostructures on the surface of Si substrates with rough morphology. Flower-like aligned ZnO nanorods are also fabricated directly onto the silicon substrates through zinc powder evaporation using a simple thermal evaporation method without a catalyst for comparison. The characteristics of these nanostructures are investigated using field-emission scanning electron microscopy, grazing-angle X-ray diffraction (XRD), and photoluminescence (PL) measurements of structures grown on both Si and porous Si substrates. The texture coefficient obtained from the XRD spectra indicates that the coral reef-like nanostructures are highly oriented on the porous silicon substrate with decreasing nanorods length and diameter from 800-900 nm to 3.5-5.5 μm and from 217-229 nm to 0.6-0.7 μm, respectively. The PL spectra show that for ZnO nanocoral reefs the UV emission shifts slightly towards lower frequency and the intensity increase with the improvement of ZnO crystallization. This non-catalyst growth technique on the rough surface of substrates may have potential applications in the fabrication of nanoelectronic and nanooptical devices.

  4. ZnO nanocoral reef grown on porous silicon substrates without catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Abdulgafour, H.I., E-mail: hind_alshaikh@yahoo.com [School of Physics, University Sains Malaysia 11800 Penang (Malaysia); Yam, F.K.; Hassan, Z.; AL-Heuseen, K.; Jawad, M.J. [School of Physics, University Sains Malaysia 11800 Penang (Malaysia)

    2011-05-05

    Research highlights: > Porous silicon (PS) technology is utilized to grow coral reef-like ZnO nanostructures on the surface of Si substrates. > Flower-like aligned ZnO nanorods are fabricated directly onto the silicon substrates through zinc powder evaporation using a simple thermal evaporation method without a catalyst for comparison. > The PL spectra show that for ZnO nanocoral reefs the UV emission shifts slightly towards lower frequency. > This non-catalyst growth technique on the rough surface of substrates may have potential applications in the fabrication of nanoelectronic and nanooptical devices. - Abstract: Porous silicon (PS) technology is utilized to grow coral reef-like ZnO nanostructures on the surface of Si substrates with rough morphology. Flower-like aligned ZnO nanorods are also fabricated directly onto the silicon substrates through zinc powder evaporation using a simple thermal evaporation method without a catalyst for comparison. The characteristics of these nanostructures are investigated using field-emission scanning electron microscopy, grazing-angle X-ray diffraction (XRD), and photoluminescence (PL) measurements of structures grown on both Si and porous Si substrates. The texture coefficient obtained from the XRD spectra indicates that the coral reef-like nanostructures are highly oriented on the porous silicon substrate with decreasing nanorods length and diameter from 800-900 nm to 3.5-5.5 {mu}m and from 217-229 nm to 0.6-0.7 {mu}m, respectively. The PL spectra show that for ZnO nanocoral reefs the UV emission shifts slightly towards lower frequency and the intensity increase with the improvement of ZnO crystallization. This non-catalyst growth technique on the rough surface of substrates may have potential applications in the fabrication of nanoelectronic and nanooptical devices.

  5. ZnO layers prepared by spray pyrolysis

    Science.gov (United States)

    Messaoudi, C.; Abd-Lefdil, S.; Sayah, D.; Cadene, M.

    1998-02-01

    Highly transparent undoped and indium doped ZnO thin films have been grown on glass substrates by using the spray pyrolysis process. Conditions of preparation have been optimized to get good quality and reproducible films with required properties. Polycrystalline films with an hexagonal Wurtzite-type structure were easily obtained under the optimum spraying conditions. Both of samples have shown high transmission coefficient in the visible and infrared wavelength range with sharp absorption edge around 380 nm which closely corresponds to the intrinsic band-gap of ZnO (3.2 eV). Orientation and crystallites size were remarkably modified by deposition temperature and indium doping. Des couches minces de ZnO, hautement transparentes, non dopées et dopées à l'indium ont été élaborées sur un substrat en verre par le procédé de pulvérisation chimique réactive spray. Les conditions de préparation ont été optimisées pour l'obtention de couches reproductibles, de bonne qualité et ayant les propriétés requises. Des films polycristallins, présentant une structure hexagonale de type Wurtzite, ont été aisément obtenus dans les conditions optimales de pulvérisation. Tous les échantillons ont présenté un coefficient de transmission élevé dans le domaine du visible et du proche infrarouge, avec une absorption brutale au voisinage de 380 nm, correspondant au gap optique du ZnO (3,2 eV). L'orientation et la taille des cristallites ont été remarquablement modifiées par la température du dépôt et par le dopage à l'indium.

  6. Performance Improvement of GaN-Based Flip-Chip White Light-Emitting Diodes with Diffused Nanorod Reflector and with ZnO Nanorod Antireflection Layer

    Directory of Open Access Journals (Sweden)

    Hsin-Ying Lee

    2014-01-01

    Full Text Available The GaN-based flip-chip white light-emitting diodes (FCWLEDs with diffused ZnO nanorod reflector and with ZnO nanorod antireflection layer were fabricated. The ZnO nanorod array grown using an aqueous solution method was combined with Al metal to form the diffused ZnO nanorod reflector. It could avoid the blue light emitted out from the Mg-doped GaN layer of the FCWLEDs, which caused more blue light emitted out from the sapphire substrate to pump the phosphor. Moreover, the ZnO nanorod array was utilized as the antireflection layer of the FCWLEDs to reduce the total reflection loss. The light output power and the phosphor conversion efficiency of the FCWLEDs with diffused nanorod reflector and 250 nm long ZnO nanorod antireflection layer were improved from 21.15 mW to 23.90 mW and from 77.6% to 80.1% in comparison with the FCWLEDs with diffused nanorod reflector and without ZnO nanorod antireflection layer, respectively.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-06-22

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

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

    International Nuclear Information System (INIS)

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

    2015-01-01

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

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

    Science.gov (United States)

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

    2015-06-01

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

  10. Influence of different carrier gases on the properties of ZnO films grown by MOCVD

    Directory of Open Access Journals (Sweden)

    Wang, Jinzhong

    2008-08-01

    Full Text Available ZnO films were grown on sapphire (001 substrate by atmospheric MOCVD using diethyl zinc and tertiary butanol precursors. The influence of different carrier gases (H2 and He on the properties was analyzed by their structural (XRD, microstructural (SEM and compositional (SIMS characterization. The intensity of the strongest diffraction peak from ZnO (002 plane was increased by about 2 orders of magnitude when He is used as carrier gas, indicating the significant enhancement in crystallinity. The surface of the samples grown using H2 and He carrier gases was composed of leaf-like and spherical grains respectively. Hydrogen [H] content in the film grown using H2 is higher than that using He, indicating that the [H] was influenced by the H2 carrier gas. Ultraviolet emission dominates the low temperature PL spectra. The emission from ZnO films grown using He show higher optical quality and more emission centers.

    Se depositaron películas de ZnO sobre sustratos de zafiro (001 utilizando dietil zinc y butanol terciario como precursores. La influencia de los diferentes gases portadores (H2 y He sobre las propiedades se estudió mediante la caracterización estructural (XRD, microestructural (SEM y composicional (SIMS. La intensidad del pico de difracción más importante del plano (002 del ZnO aumentó en dos órdenes de magnitud cuando se utiliza He como gas portador indicando un incremento significativo de la cristalinidad. La superficie de las muestras crecidas utilizando H2 y He está formada por granos en forma de hoja y de forma esférica respectivamente. El contenido en hidrógeno (H en la película es mayor cuando se utiliza H2 que cuando se utiliza He, indicando que la cantidad de hidrógeno está influenciada por el H2 del gas portador. La emisión ultravioleta domina el espectro PL de baja temperatura. La emisión de las películas de ZnO utilizando

  11. Influence of the processing conditions on the structural properties of ZnO layers obtained by PECVD

    Energy Technology Data Exchange (ETDEWEB)

    Kitova, S; Danev, G, E-mail: skitova@clf.bas.b [Institute of Optical Materials and Technology ' Acad. J. Malinowski' , Bulgarian Academy of Sciences, Acad. G. Bonchev str., bl.109, 1113 Sofia (Bulgaria)

    2010-11-01

    The plasma enhanced chemical vapor deposition (PECVD) is a powerful and flexible instrument for depositing thin layers, nanocomposites or nanostructures. In this work ZnO layers have been grown by metal-organic PECVD (RF - 13.56 MHz) on Si wafers. Zn acetylacetonate has been used as a precursor and oxygen as oxidant. The influence of the oxygen content in gas mixture, the total pressure, substrate temperature and ZnO seed layer on the structural properties of the layers deposited on Si wafers has been studied. ZnO layer properties were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD data have shown that all layers are crystalline with hexagonal wurtzite structure. The crystallites are preferentially oriented along c-axis direction perpendicular to the substrate surfaces. The results obtained indicate that by controlling the oxygen content in gas mixture, the total pressure and substrate temperature during the film growth one can control the formation of c-axis phase and the crystallite grain size. Nanorods with good alignment, vertically orientated to the substrate surface can be observed in the layers deposited at low content of O{sub 2} in plasma at substrate temperature of 400 {sup o}C. Due to their structural characteristics these layers are potential materials for preparing chemical- and biosensors where inherently large surface to volume ratio of structured materials are important prerequisite for enhanced sensitivity.

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

    International Nuclear Information System (INIS)

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

    2012-01-01

    ZnO thin films were grown by pulsed laser deposition on three different substrates: sapphire (0 0 0 1), MgO (1 0 0) and fused silica (FS). The structure and morphology of the films were characterized by x-ray diffraction and scanning electron microscopy and defect studies were carried out using slow positron implantation spectroscopy (SPIS). Films deposited on all substrates studied in this work exhibit the wurtzite ZnO structure and are characterized by an average crystallite size of 20-100 nm. However, strong differences in the microstructure of films deposited on various substrates were found. The ZnO films deposited on MgO and sapphire single-crystalline substrates exhibit local epitaxy, i.e. a well-defined relation between film crystallites and the substrate. Domains with different orientation relationships with the substrate were found in both films. On the other hand, the film deposited on the FS substrate exhibits fibre texture with random lateral orientation of crystallites. Extremely high compressive in-plane stress of σ ∼ 14 GPa was determined in the film deposited on the MgO substrate, while the film deposited on sapphire is virtually stress-free, and the film deposited on the FS substrate exhibits a tensile in-plane stress of σ ∼ 0.9 GPa. SPIS investigations revealed that the concentration of open-volume defects in the ZnO films is substantially higher than that in a bulk ZnO single crystal. Moreover, the ZnO films deposited on MgO and sapphire single-crystalline substrates exhibit a significantly higher density of defects than the film deposited on the amorphous FS substrate. (paper)

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

    KAUST Repository

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

    2017-01-01

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

  14. Dye-sensitized solar cells with a tri-layer ZnO photo-electrode

    Energy Technology Data Exchange (ETDEWEB)

    Li, Hui; Bai, Jiafan; Feng, Bo; Lu, Xiong; Weng, Jie; Jiang, Chongxi; Wang, Jianxin, E-mail: j.wang63@gmail.com

    2013-11-25

    Graphical abstract: Schematic diagram for the energy-level, the paths of charge transfer, the model of light scattering in the top layer and the assembly of the DSSC. Highlights: •We successfully fabricated ZnO photo-anodes with a tri-layer ZnO structure. •The ZnO seed layer decreased the transfer resistance at the ZnO/FTO interface. •The ZnO light scattering layer could increase the number of photoelectrons. •J{sub sc} and V{sub oc} were greatly enhanced via the use of the tri-layer ZnO structure. •The efficiency of the DSSCs for a tri-layer ZnO structure was the highest. -- Abstract: In this paper, a tri-layer ZnO structure was designed to fabricate the photo-anodes of dye-sensitized solar cells (DSSC). The results showed that an overall energy-conversion efficiency of 1.18% was achieved for DSSC with the tri-layer photo-anode, which was 14% higher than that obtained from a bilayer ZnO photo-anode (with an efficiency of 1.04%) and 76% higher than that fabricated with a single layer photo-anode (with an efficiency of 0.67%). The photo-current density and the open circuit voltage have greatly increased via the use of the tri-layer ZnO structure. Thus, the tri-layer ZnO structure might provide a new route for the improvement of the overall energy-conversion efficiency for the DSSC of ZnO.

  15. Dye-sensitized solar cells with a tri-layer ZnO photo-electrode

    International Nuclear Information System (INIS)

    Li, Hui; Bai, Jiafan; Feng, Bo; Lu, Xiong; Weng, Jie; Jiang, Chongxi; Wang, Jianxin

    2013-01-01

    Graphical abstract: Schematic diagram for the energy-level, the paths of charge transfer, the model of light scattering in the top layer and the assembly of the DSSC. Highlights: •We successfully fabricated ZnO photo-anodes with a tri-layer ZnO structure. •The ZnO seed layer decreased the transfer resistance at the ZnO/FTO interface. •The ZnO light scattering layer could increase the number of photoelectrons. •J sc and V oc were greatly enhanced via the use of the tri-layer ZnO structure. •The efficiency of the DSSCs for a tri-layer ZnO structure was the highest. -- Abstract: In this paper, a tri-layer ZnO structure was designed to fabricate the photo-anodes of dye-sensitized solar cells (DSSC). The results showed that an overall energy-conversion efficiency of 1.18% was achieved for DSSC with the tri-layer photo-anode, which was 14% higher than that obtained from a bilayer ZnO photo-anode (with an efficiency of 1.04%) and 76% higher than that fabricated with a single layer photo-anode (with an efficiency of 0.67%). The photo-current density and the open circuit voltage have greatly increased via the use of the tri-layer ZnO structure. Thus, the tri-layer ZnO structure might provide a new route for the improvement of the overall energy-conversion efficiency for the DSSC of ZnO

  16. Effect of the substrate surface topology and temperature on the structural properties of ZnO layers obtained by plasma enhanced chemical vapour deposition

    Energy Technology Data Exchange (ETDEWEB)

    Kitova, S; Danev, G, E-mail: skitova@clf.bas.b [Acad. J .Malinowski Central Laboratory of Photoprocesses, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl.109, 1113 Sofia (Bulgaria)

    2010-04-01

    In this work thin ZnO layers were grown by metal-organic PECVD (RF 13.56 MHz) on Si wafers. Zn acetylacetonate was used as a precursor and oxygen as oxidant. A system for dosed injection of the precursor and oxidant into the plasma reactor was developed. The influence of the substrate surface topology and temperature on the structural properties of the deposited layers was studied. ZnO and graphite powder dispersions were used to modify the silicon wafers before starting the deposition process of the layers. Some of the ZnO layers were deposited on the back, unpolished, side of Si wafers. Depositions at 400 {sup 0}C were performed to examine the effect of the substrate temperatures on the layer growth. The film structure was examined by XRD and SEM. The results show that all layers are crystalline with hexagonal wurtzite structure. The crystallites are preferentially oriented along the c-axis direction perpendicular to the substrate surfaces. ZnO layers deposited on thin ZnO seed films and clean Si surface exhibit well-developed grain structures and more c-axis preferred phase with better crystal quality than that of the layers deposited on graphite seed layer or rough, unpolished Si wafer.

  17. Surface characterization of ZnO nanorods grown by chemical bath deposition

    Energy Technology Data Exchange (ETDEWEB)

    Mbulanga, C.M., E-mail: crispin.mbulanga@nmmu.ac.za [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Urgessa, Z.N.; Tankio Djiokap, S.R.; Botha, J.R. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Duvenhage, M.M.; Swart, H.C. [Department of Physics, University of the Free State, P.O Box 77000, Bloemfontein ZA9300 (South Africa)

    2016-01-01

    The surface composition of as-grown and annealed ZnO nanorods (ZNs) grown by a two-step chemical bath deposition method is investigated by the following surface-sensitive techniques: Time-of-Flight Secondary Ion Mass Spectroscopy (TOF-SIMS), X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES). The presence of H on the surface and throughout the entire thickness of ZNs is confirmed by TOF-SIMS. Based on TOF-SIMS results, the O2 XPS peak mostly observable at ~531.5 is assigned to O bound to H. Furthermore, it is found that the near surface region of as-grown ZNs is Zn-rich, and annealing at high temperature (~850 °C) removes H-related defects from the surface of ZNs and affect the balance of zinc and oxygen concentrations.

  18. Field emission from carbon nanotube bundle arrays grown on self-aligned ZnO nanorods

    International Nuclear Information System (INIS)

    Li Chun; Fang Guojia; Yuan Longyan; Liu Nishuang; Ai Lei; Xiang Qi; Zhao Dongshan; Pan Chunxu; Zhao Xingzhong

    2007-01-01

    The field emission (FE) properties of carbon nanotube (CNT) bundle arrays grown on vertically self-aligned ZnO nanorods (ZNRs) are reported. The ZNRs were first synthesized on ZnO-seed-coated Si substrate by the vapour phase transport method, and then the radically grown CNTs were grown directly on the surface of the ZNRs from ethanol flames. The CNT/ZNR composite showed a turn-on field of 1.5 V μm -1 (at 0.1 μA cm -2 ), a threshold field of 4.5 V μm -1 (at 1 mA cm -2 ) and a stable emission current with fluctuations of 5%, demonstrating significantly enhanced FE of ZNRs due to the low work function and high aspect ratio of the CNTs, and large surface-to-volume ratio of the underlying ZNRs

  19. Characterization of CBD grown ZnO films with high c-axis orientation

    Energy Technology Data Exchange (ETDEWEB)

    Kahraman, S., E-mail: suleymanmku@gmail.com [Physics Department, Mustafa Kemal University, 31034 Hatay (Turkey); Bayansal, F.; Cetinkara, H.A.; Cakmak, H.M.; Gueder, H.S. [Physics Department, Mustafa Kemal University, 31034 Hatay (Turkey)

    2012-06-15

    Highly c-axis oriented ZnO films were deposited on seeded glass substrates. Successive ionic layer adsorption and reaction (SILAR) method and chemical bath deposition (CBD) method were used to obtain seed layers and ZnO films. To see the effects of seed layer and deposition time, structural (e.g. grain size, microstrain and dislocation density), morphological, and electrical (e.g. resistivity, activation energy) properties of the films were investigated by scanning electron microscopy, X-ray diffraction, and four point probe method. From the SEM images, resultant structures were found as well defined nanorods nearly perpendicular to the substrate surfaces and densely cover the substrates. The XRD patterns showed that ZnO films have hexagonal wurtzite structure with a preferred c-axis orientation along (002) plane. C-axis orientation was also supported by texture coefficient calculations. The lattice parameters of the structures were determined as a = 3.2268 A, b = 5.2745 A, {alpha} = {beta} = 90 Degree-Sign and {gamma} = 120 Degree-Sign . From the XRD patterns, it was revealed that, microstrain and dislocation density values of the structures decreased whereas grain size increased. This was attributed to enhancement occurred in lattice structure of the ZnO films. Activation energy values of the films were found in between 0.12 and 0.15 eV from the dark electrical resistivity-temperature characteristics in a temperature range of 300-500 K. - Highlights: Black-Right-Pointing-Pointer Hexagonal wurtzite structured ZnO nanorods (preferred orientation along (002) plane). Black-Right-Pointing-Pointer Electrical activation energies were calculated in between 0.12 and 0.15 eV. Black-Right-Pointing-Pointer Microstrain and dislocation density decreased with increasing deposition time. Black-Right-Pointing-Pointer Increasing deposition time was resulted in an increase in preferred orientation.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-06-15

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

  1. Device quality ZnO grown using a Filtered Cathodic Vacuum Arc

    International Nuclear Information System (INIS)

    Elzwawi, Salim; Kim, Hyung Suk; Heinhold, Robert; Lynam, Max; Turner, Gary; Partridge, Jim G.; McCulloch, Dougal G.

    2012-01-01

    In this paper we report on the structural, electrical and optical characteristics of unintentionally doped ZnO films grown on a-plane sapphire substrates using the Filtered Cathodic Vacuum Arc (FCVA) technique. The resulting films showed considerable promise for device applications with properties including high transparency, moderate intrinsic carrier concentrations (10 17 -10 19 cm -3 ), electron mobilities up to 30 cm 2 /Vs, low surface roughness (typically <2% of film thickness) and well-structured photoluminescence. Post-annealing in oxygen at temperatures up to 800 °C produced significant improvements in the properties of these films. Silver oxide Schottky diodes fabricated on FCVA ZnO showed ideality factors as low as 1.20 and good sensitivity to ultraviolet light.

  2. Structural and morphological characterizations of ZnO films grown on GaAs substrates by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Agouram, S.; Zuniga Perez, J.; Munoz-Sanjose, V. [Universitat de Valencia, Departamento de Fisica Aplicada y Electromagnetismo, Burjassot (Spain)

    2007-07-15

    ZnO films were grown on GaAs(100), GaAs(111)A and GaAs(111)B substrates by metal organic chemical vapour deposition (MOCVD). Diethylzinc (DEZn) and tertiarybutanol (t-butanol) were used as Zn and O precursors, respectively. The influence of the growth temperature and GaAs substrate orientation on the crystalline orientation and morphology of the ZnO grown films has been analysed. Crystallinity of grown films was studied by X-ray diffraction (XRD); thickness and morphology of ZnO films were investigated by scanning electron microscopy (SEM). SEM results reveal significant differences between morphologies depending on growth temperature but not significant differences were detected on the texture of grown films. (orig.)

  3. Temperature-dependent Hall effect studies of ZnO thin films grown by metalorganic chemical vapour deposition

    International Nuclear Information System (INIS)

    Roro, K T; Dangbegnon, J K; Sivaraya, S; Westraadt, J E; Neethling, J H; Leitch, A W R; Botha, J R; Kassier, G H

    2008-01-01

    The electrical properties of zinc oxide (ZnO) thin films of various thicknesses (0.3–4.4 µm) grown by metalorganic chemical vapour deposition on glass substrates have been studied by using temperature-dependent Hall-effect (TDH) measurements in the 18–300 K range. The high quality of the layers has been confirmed with x-ray diffraction, transmission electron microscopy, scanning electron microscopy and photoluminescence techniques. TDH measurements indicate the presence of a degenerate layer which significantly influences the low-temperature data. It is found that the measured mobility generally increases with increasing layer thickness, reaching a value of 120 cm 2 V −1 s −1 at room temperature for the 4.4 µm thick sample. The lateral grain size of the layers is also found to increase with thickness indicating a clear correlation between the size of the surface grains and the electrical properties of corresponding films. Theoretical fits to the Hall data suggest that the bulk conduction of the layers is dominated by a weakly compensated donor with activation energy in the 33–41 meV range and concentration of the order of 10 17 cm −3 , as well as a total acceptor concentration of mid-10 15 cm −3 . Grain boundary scattering is found to be an important limiting factor of the mobility throughout the temperature range considered

  4. Growth of c-plane ZnO on γ-LiAlO2 (1 0 0) substrate with a GaN buffer layer by plasma assisted molecular beam epitaxy

    International Nuclear Information System (INIS)

    Yan, T.; Lu, C.-Y.J.; Schuber, R.; Chang, L.; Schaadt, D.M.; Chou, M.M.C.; Ploog, K.H.; Chiang, C.-M.

    2015-01-01

    Highlights: • ZnO epilayers were grown on LiAlO 2 (1 0 0) substrate with a GaN buffer layer by MBE. • A high Zn/O flux ratio is beneficial for reducing the density of screw dislocations. • Reciprocal space maps demonstrate that the misfit strain in ZnO has been relaxed. • No interfacial layer is formed at ZnO/GaN interface using a Zn pre-exposure strategy. - Abstract: C-plane ZnO epilayers were grown on LiAlO 2 (1 0 0) substrate with a GaN buffer layer by plasma assisted molecular beam epitaxy. Both the X-ray rocking curves and the transmission electron microscopy analyses indicate that the ZnO epilayers exhibit a lower threading dislocation density (∼1 × 10 10 cm −2 ) as compared to those grown on LiAlO 2 substrate without the buffer layer. A high Zn/O flux ratio is beneficial for reducing the density of screw-type dislocations. Reciprocal space maps demonstrate that the misfit strain has been relaxed. No interfacial layer is formed at the ZnO/GaN interface by using a Zn pre-exposure strategy. The ZnO epilayers exhibit a strong near band edge emission at 3.28 eV at room temperature with a negligible green band emission

  5. Transparent conductive ZnO layers on polymer substrates: Thin film deposition and application in organic solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Dosmailov, M. [Institute of Applied Physics, Johannes Kepler University Linz, A-4040 Linz (Austria); Leonat, L.N. [Linz Institute for Organic Solar Cells (LIOS)/Institute of Physical Chemistry, Johannes Kepler University Linz, A-4040 Linz (Austria); Patek, J. [Institute of Applied Physics, Johannes Kepler University Linz, A-4040 Linz (Austria); Roth, D.; Bauer, P. [Institute of Experimental Physics, Johannes Kepler University Linz, A-4040 Linz (Austria); Scharber, M.C.; Sariciftci, N.S. [Linz Institute for Organic Solar Cells (LIOS)/Institute of Physical Chemistry, Johannes Kepler University Linz, A-4040 Linz (Austria); Pedarnig, J.D., E-mail: johannes.pedarnig@jku.at [Institute of Applied Physics, Johannes Kepler University Linz, A-4040 Linz (Austria)

    2015-09-30

    Aluminum doped ZnO (AZO) and pure ZnO thin films are grown on polymer substrates by pulsed-laser deposition and the optical, electrical, and structural film properties are investigated. Laser fluence, substrate temperature, and oxygen pressure are varied to obtain transparent, conductive, and stoichiometric AZO layers on polyethylene terephthalate (PET) that are free of cracks. At low fluence (1 J/cm{sup 2}) and low pressure (10{sup −3} mbar), AZO/PET samples of high optical transmission in the visible range, low electrical sheet resistance, and high figure of merit (FOM) are produced. AZO films on fluorinated ethylene propylene have low FOM. The AZO films on PET substrates are used as electron transport layer in inverted organic solar cell devices employing P3HT:PCBM as photovoltaic polymer-fullerene bulk heterojunction. - Highlights: • Aluminum doped and pure ZnO thin films are grown on polyethylene terephthalate. • Growth parameters laser fluence, temperature, and gas pressure are optimized. • AZO films on PET have high optical transmission and electrical conductance (FOM). • Organic solar cells on PET using AZO as electron transport layer are made. • Power conversion efficiency of these OSC devices is measured.

  6. Origin of green luminescence in ZnO thin film grown by molecular-beam epitaxy

    International Nuclear Information System (INIS)

    Heo, Y.W.; Norton, D.P.; Pearton, S.J.

    2005-01-01

    The properties of ZnO films grown by molecular-beam epitaxy are reported. The primary focus was on understanding the origin of deep-level luminescence. A shift in deep-level emission from green to yellow is observed with reduced Zn pressure during the growth. Photoluminescence and Hall measurements were employed to study correlations between deep-level/near-band-edge emission and carrier density. With these results, we suggest that the green emission is related to donor-deep acceptor (Zn vacancy V Zn - ) and the yellow to donor-deep acceptor (oxygen vacancy, O i - )

  7. ZnO nanowall network grown by chemical vapor deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, Amrita, E-mail: but.then.perhaps@gmail.com; Dhar, Subhabrata [Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai-400076 (India)

    2015-06-24

    Network of wedge shaped ZnO nanowalls are grown on c-sapphire by Chemical Vapor Deposition (CVD) technique. Structural studies using x-ray diffraction show much better crystallinity in the nanowall sample as compared to the continuous film. Moreover, the defect related broad green luminescence is found to be suppressed in the nanowall sample. The low temperature photoluminescence study also suggests the quantum confinement of carriers in nanowall sample. Electrical studies performed on the nanowalls show higher conductivity, which has been explained in terms of the reduction of scattering cross-section as a result of 1D quantum confinement of carriers on the tip of the nanowalls.

  8. Sparking deposited ZnO nanoparticles as double-layered photoelectrode in ZnO dye-sensitized solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Hongsith, Kritsada [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Thailand Center of Excellence in Physics (ThEP center), CHE, Bangkok 10400 (Thailand); Hongsith, Niyom [Thailand Center of Excellence in Physics (ThEP center), CHE, Bangkok 10400 (Thailand); School of Science, University of Phayao, Phayao 56000 (Thailand); Wongratanaphisan, Duangmanee; Gardchareon, Atcharawon; Phadungdhitidhada, Surachet [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Thailand Center of Excellence in Physics (ThEP center), CHE, Bangkok 10400 (Thailand); Singjai, Pisith [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Choopun, Supab, E-mail: supab99@gmail.com [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Thailand Center of Excellence in Physics (ThEP center), CHE, Bangkok 10400 (Thailand)

    2013-07-31

    The semiconducting layers of ZnO nanoparticles (ZN), ZnO powder (ZP) and ZnO nanopowder (ZNP) were designed and fabricated for double-layered semiconducting photoelectrode in dye-sensitized solar cells (DSSCs). The under-layer was ZN, which was prepared by simple and cost-effective sparking technique onto F-doped tin oxide (FTO) glass substrate and its thickness was controlled by number of sparking cycles for 0, 10, 25, 50 and 100 rounds under atmospheric pressure. Then, ZP or ZNP was screened on to ZN to form double-layered photoelectrode. Here, the DSSC structures were FTO/double-layered ZnO/Eosin Y/electrolyte/Pt counterelectrode. The best results of DSSCs were observed with J{sub sc} of 4.71 mA/cm{sup 2} and 5.56 mA/cm{sup 2} and photoconversion efficiency of 1.11% and 1.14% at 50 sparking cycles for ZP and ZNP over-layers, respectively. The efficiency enhancement can be explained by combination effects of electron and light scattering. Moreover, the modified equation of short circuit current density was developed and effectively used to explain the efficiency enhancement. - Highlights: • Effect of under-layer thickness is investigated. • Simple and cost-effective sparking technique is used for ZnO nanoparticles. • Efficiency enhancement can be explained by both electron and light scattering. • Modified equation of short circuit current density was developed for enhancement.

  9. Sparking deposited ZnO nanoparticles as double-layered photoelectrode in ZnO dye-sensitized solar cell

    International Nuclear Information System (INIS)

    Hongsith, Kritsada; Hongsith, Niyom; Wongratanaphisan, Duangmanee; Gardchareon, Atcharawon; Phadungdhitidhada, Surachet; Singjai, Pisith; Choopun, Supab

    2013-01-01

    The semiconducting layers of ZnO nanoparticles (ZN), ZnO powder (ZP) and ZnO nanopowder (ZNP) were designed and fabricated for double-layered semiconducting photoelectrode in dye-sensitized solar cells (DSSCs). The under-layer was ZN, which was prepared by simple and cost-effective sparking technique onto F-doped tin oxide (FTO) glass substrate and its thickness was controlled by number of sparking cycles for 0, 10, 25, 50 and 100 rounds under atmospheric pressure. Then, ZP or ZNP was screened on to ZN to form double-layered photoelectrode. Here, the DSSC structures were FTO/double-layered ZnO/Eosin Y/electrolyte/Pt counterelectrode. The best results of DSSCs were observed with J sc of 4.71 mA/cm 2 and 5.56 mA/cm 2 and photoconversion efficiency of 1.11% and 1.14% at 50 sparking cycles for ZP and ZNP over-layers, respectively. The efficiency enhancement can be explained by combination effects of electron and light scattering. Moreover, the modified equation of short circuit current density was developed and effectively used to explain the efficiency enhancement. - Highlights: • Effect of under-layer thickness is investigated. • Simple and cost-effective sparking technique is used for ZnO nanoparticles. • Efficiency enhancement can be explained by both electron and light scattering. • Modified equation of short circuit current density was developed for enhancement

  10. Strain modulated defect luminescence in ZnO nanostructures grown on Si substrates

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Hung-Ing; Hsiao, Jui-Ju; Huang, Yi-Jen; Wang, Jen-Cheng [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); Wu, Ya-Fen [Department of Electronic Engineering, Ming Chi University of Technology, Taishan, New Taipei 243, Taiwan, ROC (China); Lu, Bing-Yuh [Department of Electrical Engineering, Tun Gnan University, Shenkeng, New Taipei 222, 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)

    2015-12-15

    The strain modulated defect green luminescence from ZnO nanostructures grown on silicon substrates has been investigated in-depth. According to the Warren–Averbach Fourier analysis of the X-ray diffraction profiles, both the internal strain and the average crystallite size of the well-ordered nano-size ZnO nanostructures could be subtly modulated by careful adjustment of the aqueous solution of zinc nitrate (Zn(NO{sub 3}){sub 2}) and ammonium hydroxide (NH{sub 3}OH) used in the hydrothermal treatment. Visible defect-related and ultraviolet band-to-band emissions were characterized using temperature-dependent photoluminescence measurements over a broad temperature range from 20 to 300 K. It was found that the thermal-related tensile strain led to the blueshift of the green emission with increasing temperature, while the violet and ultraviolet emissions were thermally insensitive. These spectral observations were substantially corroborated by the deformation potential theory. - Highlights: • The strain modulated defect green luminescence from ZnO nanostructures. • Visible and ultraviolet emissions were characterized using photoluminescence. • The tensile strain led to the blueshift of the green emission. • The spectral observations were corroborated by the deformation potential theory.

  11. Zn-vacancy related defects in ZnO grown by pulsed laser deposition

    Science.gov (United States)

    Ling, F. C. C.; Luo, C. Q.; Wang, Z. L.; Anwand, W.; Wagner, A.

    2017-02-01

    Undoped and Ga-doped ZnO (002) films were grown c-sapphire using the pulsed laser deposition (PLD) method. Znvacancy related defects in the films were studied by different positron annihilation spectroscopy (PAS). These included Doppler broadening spectroscopy (DBS) employing a continuous monenergetic positron beam, and positron lifetime spectroscopy using a pulsed monoenergetic positron beam attached to an electron linear accelerator. Two kinds of Znvacancy related defects namely a monovacancy and a divacancy were identified in the films. In as-grown undoped samples grown with relatively low oxygen pressure P(O2)≤1.3 Pa, monovacancy is the dominant Zn-vacancy related defect. Annealing these samples at 900 oC induced Zn out-diffusion into the substrate and converted the monovacancy to divacancy. For the undoped samples grown with high P(O2)=5 Pa irrespective of the annealing temperature and the as-grown degenerate Ga-doped sample (n=1020 cm-3), divacancy is the dominant Zn-vacancy related defect. The clustering of vacancy will be discussed.

  12. Electron irradiation induced deep centers in hydrothermally grown ZnO

    International Nuclear Information System (INIS)

    Fang, Z.-Q.; Claflin, B.; Look, D. C.; Farlow, G. C.

    2007-01-01

    An n-type hydrothermally grown ZnO sample becomes semi-insulating (ρ∼10 8 Ω cm) after 1-MeV electron-irradiation. Deep traps produced by the irradiation were studied by thermally stimulated current spectroscopy. The dominant trap in the as-grown sample has an activation energy of 0.24 eV and is possibly related to Li Zn acceptors. However, the electron irradiation introduces a new trap with an activation energy of 0.15 eV, and other traps of energy 0.30 and 0.80 eV, respectively. From a comparison of these results with positron annihilation experiments and density functional theory, we conclude that the 0.15-eV trap may be related to V Zn

  13. Sublattice-specific ordering of ZnO layers during the heteroepitaxial growth at different temperatures

    International Nuclear Information System (INIS)

    Redondo-Cubero, A.; Vinnichenko, M.; Muecklich, A.; Kolitsch, A.; Krause, M.; Munoz, E.; Gago, R.

    2011-01-01

    The effect of the substrate temperature on the sublattice ordering in ZnO layers grown by reactive pulsed magnetron sputtering on sapphire has been investigated by different techniques. The improvement of the crystal quality and heteroepitaxial growth at relatively low temperatures (550 deg. C) is verified by x-ray diffraction, high-resolution transmission electron microscopy, Rutherford backscattering spectrometry in channeling mode (RBS/C), and Raman spectroscopy. Sublattice-resolved analysis by resonant RBS/C and Raman spectroscopy reveals that the progressive transition to the single crystal phase is accomplished in a faster way for Zn- than for O-sublattice. This behavior is attributed to the preferential annealing of defects in the Zn sublattice at low temperatures when compared to those of the O sublattice.

  14. Evolution of Structural and Optical Properties of ZnO Nanorods Grown on Vacuum Annealed Seed Crystallites

    Directory of Open Access Journals (Sweden)

    Waqar Khan

    2018-01-01

    Full Text Available In this study, the ambient condition for the as-coated seed layer (SL annealing at 350 °C is varied from air or nitrogen to vacuum to examine the evolution of structural and optical properties of ZnO nanorods (NRs. The NR crystals of high surface density (~240 rods/μm2 and aspect ratio (~20.3 show greatly enhanced (002 degree of orientation and crystalline quality, when grown on the SLs annealed in vacuum, compared to those annealed in air or nitrogen ambient. This is due to the vacuum-annealed SL crystals of a highly preferred orientation toward (002 and large grain sizes. X-ray photoelectron spectroscopy also reveals that the highest O/Zn atomic ratio of 0.89 is obtained in the case of vacuum-annealed SL crystals, which is due to the effective desorption of hydroxyl groups and other contaminants adsorbed on the surface formed during aqueous solution-based growth process. Near band edge emission (ultra violet range of 360–400 nm of the vacuum-annealed SLs is also enhanced by 44% and 33% as compared to those annealed in air and nitrogen ambient, respectively, in photoluminescence with significant suppression of visible light emission associated with deep level transition. Due to this improvement of SL optical crystalline quality, the NR crystals grown on the vacuum-annealed SLs produce ~3 times higher ultra violet emission intensity than the other samples. In summary, it is shown that the ZnO NRs preferentially grow along the wurtzite c-axis direction, thereby producing the high crystalline quality of nanostructures when they grow on the vacuum-annealed SLs of high crystalline quality with minimized impurities and excellent preferred orientation. The ZnO nanostructures of high crystalline quality achieved in this study can be utilized for a wide range of potential device applications such as laser diodes, light-emitting diodes, piezoelectric transducers and generators, gas sensors, and ultraviolet detectors.

  15. Growth of ZnO layers for transparent and flexible electronics

    International Nuclear Information System (INIS)

    Mofor, A.C.; Bakin, A.S.; Postels, B.; Suleiman, M.; Elshaer, A.; Waag, A.

    2008-01-01

    We have deposited and characterised ZnO on flexible and transparent plastic polymer. We employed a specially designed vapour phase growth system with elemental sources for zinc and oxygen and deposited thin ZnO films at temperatures below 400 deg. C. Basic photoluminescence characterisation confirms ZnO. Ohmic contacts were fabricated on these layers and the layers exhibit significantly high electron concentration with carrier mobility μ of up to 10.78 cm 2 V -1 s -1 . Furthermore, we show how these layers can be processed with conventional device processing techniques

  16. Growth of ZnO layers for transparent and flexible electronics

    Energy Technology Data Exchange (ETDEWEB)

    Mofor, A.C.; Bakin, A.S.; Postels, B.; Suleiman, M.; Elshaer, A.; Waag, A. [Institute of Semiconductor Technology, Technical University Braunschweig, Hans-Sommer-Str. 66, D-38106 Braunschweig (Germany)

    2008-02-15

    We have deposited and characterised ZnO on flexible and transparent plastic polymer. We employed a specially designed vapour phase growth system with elemental sources for zinc and oxygen and deposited thin ZnO films at temperatures below 400 deg. C. Basic photoluminescence characterisation confirms ZnO. Ohmic contacts were fabricated on these layers and the layers exhibit significantly high electron concentration with carrier mobility {mu} of up to 10.78 cm{sup 2} V{sup -1} s{sup -1}. Furthermore, we show how these layers can be processed with conventional device processing techniques.

  17. Fabrication and characterization of ZnO nanowires array electrodes with high photocurrent densities: Effects of the seed layer calcination time

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Yi-Jing; Liu, Ching-Fang; Hu, Chi-Chang, E-mail: cchu@che.nthu.edu.tw; Kuo, Jen-Hou; Boddula, Rajender

    2017-03-01

    In this work, we demonstrate that vertically grown ZnO nanowire (NW) arrays of the wurzite phase were successfully fabricated on fluorine doped tin oxide (FTO) substrates via a hydrothermal method. The coating of a seed layer onto the FTO substrates was found to favor the growth of a uniform ZnO NWs array which shows saturation in the photocurrent density with a relatively low potential bias. Furthermore, prolonging the calcination time of the seed layer makes the ZnO NWs behave the better charge separation and improve the photo-electrochemical performance. Under the irradiation at a 75 mW cm{sup −2} from a simulated sunlight source, the ZnO NWs array electrode prepared from the seed layer with calcination at 350 °C for 5 h shows a saturated photocurrent density of 514 μA cm{sup −2} and a maximum half-cell solar-to-hydrogen (HC-STH) efficiency of 0.26% was obtained at 0.6 V versus reversible hydrogen electrode (RHE) in neutral electrolyte. - Highlights: • The seed layer annealing time strongly influences the textural and photo-activity of ZnO NWs. • The average diameter and density of ZnO NWs were controlled to 47–70 nm and 46–70 NWs μm{sup −2}, respectively. • ZnO NWs show promising application potential in solar-electrocatalytic water splitting under potential bias. • The ZnO NWs with SL annealing time = 5 h achieve the highest HC-STH efficiency of 0.26% at 0.6 V.

  18. Large-area, laterally-grown epitaxial semiconductor layers

    Science.gov (United States)

    Han, Jung; Song, Jie; Chen, Danti

    2017-07-18

    Structures and methods for confined lateral-guided growth of a large-area semiconductor layer on an insulating layer are described. The semiconductor layer may be formed by heteroepitaxial growth from a selective growth area in a vertically-confined, lateral-growth guiding structure. Lateral-growth guiding structures may be formed in arrays over a region of a substrate, so as to cover a majority of the substrate region with laterally-grown epitaxial semiconductor tiles. Quality regions of low-defect, stress-free GaN may be grown on silicon.

  19. MOVPE gallium-nitride nanostructures fabricated on ZnO nanorod templates grown from aqueous chemical solution

    Energy Technology Data Exchange (ETDEWEB)

    Fuendling, Soenke; Li Shunfeng; Postels, Bianca; Al-Suleiman, Mohamed; Wehmann, Hergo-Heinrich; Bakin, Andrey; Waag, Andreas, E-mail: s.fuendling@tu-bs.de [Institut fuer Halbleitertechnik, Technische Universitaet Braunschweig, 38096 Braunschweig (Germany)

    2009-11-15

    Concerning optoelectronic devices fabricated by epitaxial methods, the combination of ZnO and GaN has promising aspects regarding their good optical properties and a relatively good lattice matching between both as compared to other foreign substrates like sapphire or silicon. Moreover ZnO nanopillar arrays may serve as a template for GaN nanopillar fabrication or for high quality GaN layers by lateral overgrowth of the ZnO nanopillars. In this work, we investigate the combination of two very different growth methods - aqueous chemical low temperature growth (ACG) for the ZnO nanopillar templates on silicon substrates and metalorganic vapor phase epitaxy (MOVPE) for the GaN overgrowth - in order to show to which extent the very cost efficient ZnO templates suit the high demands of GaN MOVPE. By a combination of annealing and photoluminescence experiments we show that the properties of the heterostructures change significantly with temperature.

  20. Fabrication of Well-Aligned ZnO Nanorods Using a Composite Seed Layer of ZnO Nanoparticles and Chitosan Polymer.

    Science.gov (United States)

    Khun, Kimleang; Ibupoto, Zafar Hussain; AlSalhi, Mohamad S; Atif, Muhammad; Ansari, Anees A; Willander, Magnus

    2013-09-30

    In this study, by taking the advantage of both inorganic ZnO nanoparticles and the organic material chitosan as a composite seed layer, we have fabricated well-aligned ZnO nanorods on a gold-coated glass substrate using the hydrothermal growth method. The ZnO nanoparticles were characterized by the Raman spectroscopic techniques, which showed the nanocrystalline phase of the ZnO nanoparticles. Different composites of ZnO nanoparticles and chitosan were prepared and used as a seed layer for the fabrication of well-aligned ZnO nanorods. Field emission scanning electron microscopy, energy dispersive X-ray, high-resolution transmission electron microscopy, X-ray diffraction, and infrared reflection absorption spectroscopic techniques were utilized for the structural characterization of the ZnO nanoparticles/chitosan seed layer-coated ZnO nanorods on a gold-coated glass substrate. This study has shown that the ZnO nanorods are well-aligned, uniform, and dense, exhibit the wurtzite hexagonal structure, and are perpendicularly oriented to the substrate. Moreover, the ZnO nanorods are only composed of Zn and O atoms. An optical study was also carried out for the ZnO nanoparticles/chitosan seed layer-coated ZnO nanorods, and the obtained results have shown that the fabricated ZnO nanorods exhibit good crystal quality. This study has provided a cheap fabrication method for the controlled morphology and good alignment of ZnO nanorods, which is of high demand for enhancing the working performance of optoelectronic devices.

  1. Fabrication of Well-Aligned ZnO Nanorods Using a Composite Seed Layer of ZnO Nanoparticles and Chitosan Polymer

    Directory of Open Access Journals (Sweden)

    Anees A. Ansari

    2013-09-01

    Full Text Available In this study, by taking the advantage of both inorganic ZnO nanoparticles and the organic material chitosan as a composite seed layer, we have fabricated well-aligned ZnO nanorods on a gold-coated glass substrate using the hydrothermal growth method. The ZnO nanoparticles were characterized by the Raman spectroscopic techniques, which showed the nanocrystalline phase of the ZnO nanoparticles. Different composites of ZnO nanoparticles and chitosan were prepared and used as a seed layer for the fabrication of well-aligned ZnO nanorods. Field emission scanning electron microscopy, energy dispersive X-ray, high-resolution transmission electron microscopy, X-ray diffraction, and infrared reflection absorption spectroscopic techniques were utilized for the structural characterization of the ZnO nanoparticles/chitosan seed layer-coated ZnO nanorods on a gold-coated glass substrate. This study has shown that the ZnO nanorods are well-aligned, uniform, and dense, exhibit the wurtzite hexagonal structure, and are perpendicularly oriented to the substrate. Moreover, the ZnO nanorods are only composed of Zn and O atoms. An optical study was also carried out for the ZnO nanoparticles/chitosan seed layer-coated ZnO nanorods, and the obtained results have shown that the fabricated ZnO nanorods exhibit good crystal quality. This study has provided a cheap fabrication method for the controlled morphology and good alignment of ZnO nanorods, which is of high demand for enhancing the working performance of optoelectronic devices.

  2. An efficient BTX sensor based on ZnO nanoflowers grown by CBD method

    Science.gov (United States)

    Acharyya, D.; Bhattacharyya, P.

    2015-04-01

    In this paper, sensing performance of ZnO nanoflower like structures derived by chemical bath deposition method (CBD), towards Benzene Toluene and Xylene (BTX) vapors is reported. Relatively higher bath temperature (110 °C) and high pH value (pH: 11) of solution escort to higher growth rate along [0 0 0 1] plane of ZnO, which eventually resulted in pointed edge nanorod based flower like structures after 3 h. After detailed structural characterizations (field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD)), existence of different defect states (viz. oxygen vacancy (Vo), Zinc vacancy (VZn) and Zinc interstitials (Zni)) were authenticated by Photoluminescence (PL) spectroscopy. BTX sensing performance, employing the nanoflowers as the sensing layer, was carried out in resistive mode with two Pd lateral electrodes. The sensor study was performed at different temperatures (150-350 °C) in the concentration range of 0.5-700 ppm of the respective vapors. The highest normalized resistance response (NRR%) was achieved at 200 °C. At this optimum temperature, normalized resistance responses (39.3/92.6%, 45.8/96.9%, and 47.8/99% respectively) were found to be promising towards 0.5/700 ppm of benzene, toluene and xylene. The response time of the sensor towards the target species were also found to be appreciably fast (15 s, 6 s, and 5 s) towards 700 ppm of benzene, toluene and xylene respectively. Detailed sensing mechanism for BTX with such flower like ZnO structures was explained with the help of interaction of band structures (of ZnO) with the corresponding highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the target species.

  3. Electrical and structural characterization of as-grown and annealed hydrothermal bulk ZnO

    International Nuclear Information System (INIS)

    Kassier, G. H.; Hayes, M.; Auret, F. D.; Mamor, M.; Bouziane, K.

    2007-01-01

    Hall effect measurements in the range 20-370 K on as-grown and annealed hydrothermal bulk ZnO have been performed. The bulk conductivity in the highly resistive as-grown sample was found to decrease and then increase after annealing at 550 deg. C and 930 deg. C, respectively. The conduction in the as-grown material is attributed to a deep donor which is replaced by a much shallower donor after annealing at 930 deg. C. Annealing at both temperatures also produced strong surface conduction effects. Nondegenerate low-mobility surface conduction dominated the electrical properties of the sample annealed at 550 deg. C, while a degenerate surface channel was formed after annealing at 930 deg. C. In addition, Rutherford backscattering and channeling spectrometry (RBS/C) was used to assess the effect of annealing on the crystalline quality of the samples. RBS/C measurements reveal that annealing at 930 deg. C leads to significant improvement of the crystalline quality of the material, while annealing at 550 deg. C results in the segregation of a nonchanneling impurity at the surface

  4. Effects of annealing on the recombination dynamics of low-temperature grown ZnO nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Hilker, B.; Bekeny, C.; Voss, T.; Gutowski, J. [IFP, Universitaet Bremen, 28334 Bremen (Germany); Hauschild, R.; Kalt, H. [Universitaet Karlsruhe, 76128 Karlsruhe (Germany); Postels, B.; Bakin, Andrey; Waag, A. [IHT, TU Braunschweig, 38023 Braunschweig (Germany)

    2007-07-01

    We present systematic temperature and excitation density dependent time-resolved photoluminescence (TRPL) measurements of as-grown and annealed ZnO nanorods fabricated by an aqueous chemical growth (ACG) technique at {proportional_to}90 C. The as-grown nanorods show strong nearband-edge and rather weak deep-level emission indicating their already good optical quality. At 4K, we find a broad emission line at 3.36 eV (line width 30 meV) which we attribute to recombination from a donor band formed through the high donor concentration. After annealing in oxygen and nitrogen atmospheres at 600-800 C well-resolved and sharper excitonic transitions are observed. To understand the recombination dynamics in the nanorods we carried out TRPL measurements using a frequency-doubled femtosecond laser and a streak camera. The as-grown sample shows a very fast monoexponential decay time of {proportional_to}10ps independent of temperature and excitation density. In contrast, the annealed samples exhibit a biexponential decay. Each a fast {tau}1 and a slow {tau}2 time constant have been determined for all annealed samples both of them significantly varying depending on the annealing atmosphere and temperature. This will be discussed on the basis of a phenomenological rate-equation model.

  5. Ultrathin ZnS and ZnO Interfacial Passivation Layers for Atomic-Layer-Deposited HfO2 Films on InP Substrates.

    Science.gov (United States)

    Kim, Seung Hyun; Joo, So Yeong; Jin, Hyun Soo; Kim, Woo-Byoung; Park, Tae Joo

    2016-08-17

    Ultrathin ZnS and ZnO films grown by atomic layer deposition (ALD) were employed as interfacial passivation layers (IPLs) for HfO2 films on InP substrates. The interfacial layer growth during the ALD of the HfO2 film was effectively suppressed by the IPLs, resulting in the decrease of electrical thickness, hysteresis, and interface state density. Compared with the ZnO IPL, the ZnS IPL was more effective in reducing the interface state density near the valence band edge. The leakage current density through the film was considerably lowered by the IPLs because the film crystallization was suppressed. Especially for the film with the ZnS IPL, the leakage current density in the low-voltage region was significantly lower than that observed for the film with the ZnO IPL, because the direct tunneling current was suppressed by the higher conduction band offset of ZnS with the InP substrate.

  6. Void Structures in Regularly Patterned ZnO Nanorods Grown with the Hydrothermal Method

    Directory of Open Access Journals (Sweden)

    Yu-Feng Yao

    2014-01-01

    Full Text Available The void structures and related optical properties after thermal annealing with ambient oxygen in regularly patterned ZnO nanrorod (NR arrays grown with the hydrothermal method are studied. In increasing the thermal annealing temperature, void distribution starts from the bottom and extends to the top of an NR in the vertical (c-axis growth region. When the annealing temperature is higher than 400°C, void distribution spreads into the lateral (m-axis growth region. Photoluminescence measurement shows that the ZnO band-edge emission, in contrast to defect emission in the yellow-red range, is the strongest under the n-ZnO NR process conditions of 0.003 M in Ga-doping concentration and 300°C in thermal annealing temperature with ambient oxygen. Energy dispersive X-ray spectroscopy data indicate that the concentration of hydroxyl groups in the vertical growth region is significantly higher than that in the lateral growth region. During thermal annealing, hydroxyl groups are desorbed from the NR leaving anion vacancies for reacting with cation vacancies to form voids.

  7. Photoluminescence transient study of surface defects in ZnO nanorods grown by chemical bath deposition

    Science.gov (United States)

    Barbagiovanni, E. G.; Strano, V.; Franzò, G.; Crupi, I.; Mirabella, S.

    2015-03-01

    Two deep level defects (2.25 and 2.03 eV) associated with oxygen vacancies (Vo) were identified in ZnO nanorods (NRs) grown by low cost chemical bath deposition. A transient behaviour in the photoluminescence (PL) intensity of the two Vo states was found to be sensitive to the ambient environment and to NR post-growth treatment. The largest transient was found in samples dried on a hot plate with a PL intensity decay time, in air only, of 23 and 80 s for the 2.25 and 2.03 eV peaks, respectively. Resistance measurements under UV exposure exhibited a transient behaviour in full agreement with the PL transient, indicating a clear role of atmospheric O2 on the surface defect states. A model for surface defect transient behaviour due to band bending with respect to the Fermi level is proposed. The results have implications for a variety of sensing and photovoltaic applications of ZnO NRs.

  8. Photoluminescence study of aligned ZnO nanorods grown using chemical bath deposition

    International Nuclear Information System (INIS)

    Urgessa, Z.N.; Oluwafemi, O.S.; Dangbegnon, J.K.; Botha, J.R.

    2012-01-01

    The photoluminescence study of self-assembled ZnO nanorods grown on a pre-treated Si substrate by a simple chemical bath deposition method at a temperature of 80 °C is hereby reported. By annealing in O 2 environment the UV emission is enhanced with diminishing deep level emission suggesting that most of the deep level emission is due to oxygen vacancies. The photoluminescence was investigated from 10 K to room temperature. The low temperature photoluminescence spectrum is dominated by donor-bound exciton. The activation energy and binding energy of shallow donors giving rise to bound exciton emission were calculated to be around 13.2 meV, 46 meV, respectively. Depending on these energy values and nature of growth environment, hydrogen is suggested to be the possible contaminating element acting as a donor.

  9. Photoluminescence study of aligned ZnO nanorods grown using chemical bath deposition

    Energy Technology Data Exchange (ETDEWEB)

    Urgessa, Z.N. [Department of Physics, P.O. Box 77000, Nelson Mandela Metropolitan University, Port Elizabeth 6031 (South Africa); Oluwafemi, O.S. [Department of Chemistry and Chemical Technology, Walter Sisulu University, Mthatha Campus, Private Bag XI, 5117 (South Africa); Dangbegnon, J.K. [Department of Physics, P.O. Box 77000, Nelson Mandela Metropolitan University, Port Elizabeth 6031 (South Africa); Botha, J.R., E-mail: Reinhardt.Botha@nmmu.ac.za [Department of Physics, P.O. Box 77000, Nelson Mandela Metropolitan University, Port Elizabeth 6031 (South Africa)

    2012-05-15

    The photoluminescence study of self-assembled ZnO nanorods grown on a pre-treated Si substrate by a simple chemical bath deposition method at a temperature of 80 Degree-Sign C is hereby reported. By annealing in O{sub 2} environment the UV emission is enhanced with diminishing deep level emission suggesting that most of the deep level emission is due to oxygen vacancies. The photoluminescence was investigated from 10 K to room temperature. The low temperature photoluminescence spectrum is dominated by donor-bound exciton. The activation energy and binding energy of shallow donors giving rise to bound exciton emission were calculated to be around 13.2 meV, 46 meV, respectively. Depending on these energy values and nature of growth environment, hydrogen is suggested to be the possible contaminating element acting as a donor.

  10. Microwave Synthesized ZnO Nanorod Arrays for UV Sensors: A Seed Layer Annealing Temperature Study.

    Science.gov (United States)

    Pimentel, Ana; Ferreira, Sofia Henriques; Nunes, Daniela; Calmeiro, Tomas; Martins, Rodrigo; Fortunato, Elvira

    2016-04-20

    The present work reports the influence of zinc oxide (ZnO) seed layer annealing temperature on structural, optical and electrical properties of ZnO nanorod arrays, synthesized by hydrothermal method assisted by microwave radiation, to be used as UV sensors. The ZnO seed layer was produced using the spin-coating method and several annealing temperatures, ranging from 100 to 500 °C, have been tested. X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and spectrophotometry measurements have been used to investigate the structure, morphology, and optical properties variations of the produced ZnO nanorod arrays regarding the seed layer annealing temperatures employed. After the growth of ZnO nanorod arrays, the whole structure was tested as UV sensors, showing an increase in the sensitivity with the increase of seed layer annealing temperature. The UV sensor response of ZnO nanorod arrays produced with the seed layer annealed temperature of 500 °C was 50 times superior to the ones produced with a seed layer annealed at 100 °C.

  11. The roles of buffer layer thickness on the properties of the ZnO epitaxial films

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Kun, E-mail: ktang@nju.edu.cn [Nanjing National Laboratory of Microstructures and School of Electronic Science and Engineering, Nanjing University, Nanjing 210023 (China); Huang, Shimin [Nanjing National Laboratory of Microstructures and School of Electronic Science and Engineering, Nanjing University, Nanjing 210023 (China); Gu, Shulin, E-mail: slgu@nju.edu.cn [Nanjing National Laboratory of Microstructures and School of Electronic Science and Engineering, Nanjing University, Nanjing 210023 (China); Zhu, Shunming [Nanjing National Laboratory of Microstructures and School of Electronic Science and Engineering, Nanjing University, Nanjing 210023 (China); Ye, Jiandong [Nanjing National Laboratory of Microstructures and School of Electronic Science and Engineering, Nanjing University, Nanjing 210023 (China); Nanjing University Institute of Optoelectronics at Yangzhou, Yangzhou 225009 (China); Xu, Zhonghua; Zheng, Youdou [Nanjing National Laboratory of Microstructures and School of Electronic Science and Engineering, Nanjing University, Nanjing 210023 (China)

    2016-12-01

    Highlights: • The growth mechanism has been revealed for the ZnO buffers with different thickness. • The surface morphology has been determined as the key factor to affect the epitaxial growth. • The relation between the hexagonal pits from buffers and epi-films has been established. • The hexagonal pits formed in the epi-films have been attributed to the V-shaped defects inheriting from the dislocations in the buffers. • The structural and electrical properties of the V-defects have been presented and analyzed. - Abstract: In this article, the authors have investigated the optimization of the buffer thickness for obtaining high-quality ZnO epi-films on sapphire substrates. The growth mechanism of the buffers with different thickness has been clearly revealed, including the initial nucleation and vertical growth, the subsequent lateral growth with small grain coalescence, and the final vertical growth along the existing larger grains. Overall, the quality of the buffer improves with increasing thickness except the deformed surface morphology. However, by a full-scale evaluation of the properties for the epi-layers, the quality of the epi-film is briefly determined by the surface morphology of the buffer, rather than the structural, optical, or electrical properties of it. The best quality epi-layer has been grown on the buffer with a smooth surface and well-coalescent grains. Meanwhile, due to the huge lattice mismatch between sapphire and ZnO, dislocations are inevitably formed during the growth of buffers. More importantly, as the film grows thicker, the dislocations may attracting other smaller dislocations and defects to reduce the total line energy and thus result in the formation of V-shape defects, which are connected with the bottom of the threading dislocations in the buffers. The V-defects appear as deep and large hexagonal pits from top view and they may act as electron traps which would affect the free carrier concentration of the epi-layers.

  12. The roles of buffer layer thickness on the properties of the ZnO epitaxial films

    International Nuclear Information System (INIS)

    Tang, Kun; Huang, Shimin; Gu, Shulin; Zhu, Shunming; Ye, Jiandong; Xu, Zhonghua; Zheng, Youdou

    2016-01-01

    Highlights: • The growth mechanism has been revealed for the ZnO buffers with different thickness. • The surface morphology has been determined as the key factor to affect the epitaxial growth. • The relation between the hexagonal pits from buffers and epi-films has been established. • The hexagonal pits formed in the epi-films have been attributed to the V-shaped defects inheriting from the dislocations in the buffers. • The structural and electrical properties of the V-defects have been presented and analyzed. - Abstract: In this article, the authors have investigated the optimization of the buffer thickness for obtaining high-quality ZnO epi-films on sapphire substrates. The growth mechanism of the buffers with different thickness has been clearly revealed, including the initial nucleation and vertical growth, the subsequent lateral growth with small grain coalescence, and the final vertical growth along the existing larger grains. Overall, the quality of the buffer improves with increasing thickness except the deformed surface morphology. However, by a full-scale evaluation of the properties for the epi-layers, the quality of the epi-film is briefly determined by the surface morphology of the buffer, rather than the structural, optical, or electrical properties of it. The best quality epi-layer has been grown on the buffer with a smooth surface and well-coalescent grains. Meanwhile, due to the huge lattice mismatch between sapphire and ZnO, dislocations are inevitably formed during the growth of buffers. More importantly, as the film grows thicker, the dislocations may attracting other smaller dislocations and defects to reduce the total line energy and thus result in the formation of V-shape defects, which are connected with the bottom of the threading dislocations in the buffers. The V-defects appear as deep and large hexagonal pits from top view and they may act as electron traps which would affect the free carrier concentration of the epi-layers.

  13. Single and multi-layered core-shell structures based on ZnO nanorods obtained by aerosol assisted chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Sáenz-Trevizo, A.; Amézaga-Madrid, P.; Pizá-Ruiz, P.; Antúnez-Flores, W.; Ornelas-Gutiérrez, C.; Miki-Yoshida, M., E-mail: mario.miki@cimav.edu.mx

    2015-07-15

    Core–shell nanorod structures were prepared by a sequential synthesis using an aerosol assisted chemical vapor deposition technique. Several samples consisting of ZnO nanorods were initially grown over TiO{sub 2} film-coated borosilicate glass substrates, following the synthesis conditions reported elsewhere. Later on, a uniform layer consisting of individual Al, Ni, Ti or Fe oxides was grown onto ZnO nanorod samples forming the so-called single MO{sub x}/ZnO nanorod core–shell structures, where MO{sub x} was the metal oxide shell. Additionally, a three-layer core–shell sample was developed by growing Fe, Ti and Fe oxides alternately, onto the ZnO nanorods. The microstructure of the core–shell materials was characterized by grazing incidence X-ray diffraction, scanning and transmission electron microscopy. Energy dispersive X-ray spectroscopy was employed to corroborate the formation of different metal oxides. X-ray diffraction outcomes for single core–shell structures showed solely the presence of ZnO as wurtzite and TiO{sub 2} as anatase. For the multi-layered shell sample, the existence of Fe{sub 2}O{sub 3} as hematite was also detected. Morphological observations suggested the existence of an outer material grown onto the nanorods and further microstructural analysis by HR-STEM confirmed the development of core–shell structures in all cases. These studies also showed that the individual Al, Fe, Ni and Ti oxide layers are amorphous; an observation that matched with X-ray diffraction analysis where no apparent extra oxides were detected. For the multi-layered sample, the development of a shell consisting of three different oxide layers onto the nanorods was found. Overall results showed that no alteration in the primary ZnO core was produced during the growth of the shells, indicating that the deposition technique used herein was and it is suitable for the synthesis of homogeneous and complex nanomaterials high in quality and purity. In addition

  14. Iron (III Ion Sensor Based on the Seedless Grown ZnO Nanorods in 3 Dimensions Using Nickel Foam Substrate

    Directory of Open Access Journals (Sweden)

    Mazhar Ali Abbasi

    2013-01-01

    Full Text Available In the present work, the seedless, highly aligned and vertical ZnO nanorods in 3 dimensions (3D were grown on the nickel foam substrate. The seedless grown ZnO nanorods were characterised by field emission scanning electron microscopy (FESEM, high resolution transmission electron microscopy (HRTEM, and X-ray diffraction (XRD techniques. The characterised seedless ZnO nanorods in 3D on nickel foam were highly dense, perpendicular to substrate, grown along the (002 crystal plane, and also composed of single crystal. In addition to this, these seedless ZnO nanorods were functionalized with trans-dinitro-dibenzo-18-6 crown ether, a selective iron (III ion ionophore, along with other components of membrane composition such as polyvinyl chloride (PVC, 2-nitopentylphenyl ether as plasticizer (NPPE, and tetrabutyl ammonium tetraphenylborate (TBATPB as conductivity increaser. The sensor electrode has shown high linearity with a wide range of detection of iron (III ion concentrations from 0.005 mM to 100 mM. The low limit of detection of the proposed ion selective electrode was found to be 0.001 mM. The proposed sensor also described high storage stability, selectivity, reproducibility, and repeatability and a quick response time of less than 10 s.

  15. Effects of seed layers on controlling of the morphology of ZnO nanostructures and superhydrophobicity of ZnO nanostructure/stearic acid composite films

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jing; Liu, Zhihua, E-mail: sdwfliu@163.com; Liu, Junqi; E, Lei; Liu, Zhifeng, E-mail: tjulzf@163.com

    2016-11-01

    Hydrophobic ZnO self-cleaning thin films with the nanobundles and nanocarpets structures fabricated on indium tin oxides (ITO) glass substrate are reported. The water contact angle of ZnO nanobundles and nanocarpets structures (79° and 67° respectively) is higher than that of unmodified ZnO nanorods. A subsequent chemical treatment with stearic acid (SA) contributed to a superhydrophobic surface with a water contact angle of 159°. Its superhydrophobic property is originated from the nanobundles or nanocarpets structures and surface energy of SA/ZnO nanobundles and SA/ZnO nanocarpets composite nanostructures. Moreover, this promising ZnO nanostructured materials show an important application in self-cleaning smart coatings. - Highlights: • PEG and CTAB are firstly introduced to modify the morphology of ZnO seed layers. • ZnO nanobundles and nanocarpets obtained from different seed layers. • Superhydrophobic surfaces obtained by chemcial treatment using SA.

  16. Photoluminescence of Hexagonal ZnO Nanorods Hydrothermally Grown on Zn Foils in KOH Solutions with Different Values of Basicity

    Directory of Open Access Journals (Sweden)

    Nuengruethai Ekthammathat

    2013-01-01

    Full Text Available Aligned hexagonal ZnO nanorods on pure Zn foils were hydrothermally synthesized in 30 mL solutions containing 0.05–0.50 g KOH. The products were characterized by X-ray diffraction (XRD, scanning electron microscopy (SEM, transmission electron microscopy (TEM, and photoluminescence (PL spectroscopy. In this research, wurtzite hexagonal ZnO nanorods grown along the [002] direction with green light emission at 541 nm caused by singly ionized oxygen vacancies inside were detected.

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

    Energy Technology Data Exchange (ETDEWEB)

    Grechnikov, A A; Borodkov, A S [Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, 19 Kosygin Str., 119991 Moscow (Russian Federation); Georgieva, V B [Georgi Nadjakov Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee, 1784 Sofia (Bulgaria); Alimpiev, S S; Nikiforov, S M; Simanovsky, Ya O [General Physics Institute, Russian Academy of Sciences, 38 Vavilov Str., 119991 Moscow (Russian Federation); Dimova-Malinovska, D; Angelov, O I, E-mail: lazarova@issp.bas.b [Laboratory for Solar Energy and New Energy Sources, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee, 1784 Sofia (Bulgaria)

    2010-04-01

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

  18. Influence of seed layer treatment on ZnO growth morphology and their device performance in dye-sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, R. Saravana [PG and Research, Department of Physics, Kongunadu Arts and Science College, Coimbatore 641029 (India); Sudhagar, P. [Energy Materials Laboratary, WCU Program Department of Energy Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Matheswaran, P. [PG and Research, Department of Physics, Kongunadu Arts and Science College, Coimbatore 641029 (India); Sathyamoorthy, R., E-mail: rsathya59@gmail.com [PG and Research, Department of Physics, Kongunadu Arts and Science College, Coimbatore 641029 (India); Kang, Yong Soo, E-mail: kangys@hanyang.ac.kr [Energy Materials Laboratary, WCU Program Department of Energy Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)

    2010-09-15

    The surface modification of the ZnO seed layer by ultrasonic mediated rinsing (UMR) was realized as an efficient tool for growing highly branched hierarchical ZnO nanorods through multistage approach. The hierarchical ZnO nanostructure achieved through UMR approach was performed as the photoanodes in dye-sensitized solar cells (DSSCs). The DSSC based on the novel branched network resulted in energy conversion efficiency ({eta}) of 1.1% (J{sub sc} = 4.7 mA cm{sup -2}). The improved device performance was ascribed to the (a) high internal surface area for efficient dye adsorption, (b) rapid electron pathway for charge transport from ZnO to transparent conducting oxide (TCO) substrate and (c) producing random multiple scattering of the light within the hierarchical network leading to photon localization, thereby increasing the probability of the interaction between the photons and the dye molecules of the branched network. The beneficial effect of the UMR approach was distinguished by fabricating DSSCs based on randomly oriented ZnO nanorods prepared by conventional rinsing (CR), which offered lower conversion efficiency {eta} = 0.7% (J{sub sc} = 3.8 mA cm{sup -2}). The exploration of novel hierarchical ZnO nanorods grown in the present work by the low temperature solution growth techniques may pave way to bring out photoanode material on flexible substrates for the fast growing DSSCs devices.

  19. Double-layered ZnO nanostructures for efficient perovskite solar cells

    KAUST Repository

    Mahmood, Khalid; S. Swain, Bhabani; Amassian, Aram

    2014-01-01

    To date, a single layer of TiO2 or ZnO has been the most successful implementations of any electron transport layer (ETL) in solution-processed perovskite solar cells. In a quest to improve the ETL, we explore a new nanostructured double-layer ZnO film for mesoscopic perovskite-based thin film photovoltaics. This approach yields a maximum power conversion efficiency of 10.35%, which we attribute to the morphology of oxide layer and to faster electron transport. The successful implementation of the low-temperature hydrothermally processed double-layer ZnO film as ETL in perovskite solar cells highlights the opportunities to further improve the efficiencies by focusing on the ETL in this rapidly developing field. This journal is

  20. 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.)

  1. Low temperature fabrication of ZnO compact layer for high performance plastic dye-sensitized ZnO solar cells

    International Nuclear Information System (INIS)

    Hu Fangyi; Xia Yujing; Guan Zisheng; Yin Xiong; He Tao

    2012-01-01

    Highlights: ► ZnO compact layer is prepared via simple electrochemical method at low temperature. ► Compact layer can effectively block electron transfer from TCO to electrolyte. ► DSC PCE is improved by 17% when ZnO compact layer is introduced. ► Plastic DSCs with ZnO compact layer show a PCE of 3.29% under AM1.5 100 mW cm −2 . ► The above efficiency is comparable to that with high temperature sintering step. - Abstract: ZnO compact layer has been fabricated on transparent conducting oxide glass and plastic polymer substrates at low temperature via electrodeposition. The results of dark current and cyclic voltammetric measurements demonstrate that the compact layer can effectively reduce the short circuit from transparent conducting oxide to electrolyte in dye-sensitized ZnO solar cells, leading to an increase of open-circuit photovoltage and fill factor of the devices and, thereby, the power conversion efficiency. The resultant plastic dye-sensitized ZnO solar cell presents an efficiency of 3.29% under illumination of 100 mW cm −2 , AM 1.5G. This indicates that electrodeposition is a viable method to fabricate ZnO compact layer for high performance flexible devices.

  2. Doping properties of ZnO thin films for photovoltaic devices grown by URT-IP (ion plating) method

    International Nuclear Information System (INIS)

    Iwata, K.; Sakemi, T.; Yamada, A.; Fons, P.; Awai, K.; Yamamoto, T.; Matsubara, M.; Tampo, H.; Sakurai, K.; Ishizuka, S.; Niki, S.

    2004-01-01

    The Uramoto-gun with Tanaka magnetic field (URT)-ion plating (IP) method is a novel ion plating technique for thin film deposition. This method offers the advantage of low-ion damage, low deposition temperatures, large area deposition and high growth rates. Ga-doped ZnO thin films were grown using the URT-IP method, and the doping properties were evaluated. The opposing goals of low Ga composition and low resistivity are required for industrial applications of transparent conductive oxide (TCO). We have carried out a comparison between the carrier concentration and Ga atomic concentration in Ga-doped ZnO thin films and found the trade-off point for optimal TCO performance. The optimum growth conditions were obtained using a 3% Ga 2 O 3 content ZnO target

  3. 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.

  4. 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

  5. Hydrothermal Growth and Application of ZnO Nanowire Films with ZnO and TiO2Buffer Layers in Dye-Sensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Jiang Chunhua

    2009-01-01

    Full Text Available Abstract This paper reports the effects of the seed layers prepared by spin-coating and dip-coating methods on the morphology and density of ZnO nanowire arrays, thus on the performance of ZnO nanowire-based dye-sensitized solar cells (DSSCs. The nanowire films with the thick ZnO buffer layer (~0.8–1 μm thick can improve the open circuit voltage of the DSSCs through suppressing carrier recombination, however, and cause the decrease of dye loading absorbed on ZnO nanowires. In order to further investigate the effect of TiO2buffer layer on the performance of ZnO nanowire-based DSSCs, compared with the ZnO nanowire-based DSSCs without a compact TiO2buffer layer, the photovoltaic conversion efficiency and open circuit voltage of the ZnO DSSCs with the compact TiO2layer (~50 nm thick were improved by 3.9–12.5 and 2.4–41.7%, respectively. This can be attributed to the introduction of the compact TiO2layer prepared by sputtering method, which effectively suppressed carrier recombination occurring across both the film–electrolyte interface and the substrate–electrolyte interface.

  6. 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

  7. InN-based layers grown by modified HVPE

    International Nuclear Information System (INIS)

    Syrkin, A.; Usikov, A.; Soukhoveev, V.; Kovalenkov, O.; Ivantsov, V.; Dmitriev, V.; Collins, C.; Readinger, E.; Shmidt, N.; Davydov, V.; Nikishin, S.; Kuryatkov, V.; Song, D.; Rosenbladt, D.; Holtz, Mark

    2006-01-01

    This paper contains results on InN and InGaN growth by Hydride Vapor Phase Epitaxy (HVPE) on various substrates including sapphire and GaN/sapphire, AlGaN/sapphire, and AlN/sapphire templates. The growth processes are carried out at atmospheric pressure in a hot wall reactor in the temperature range from 500 to 750 and ordm;C. Continuous InN layers are grown on GaN/sapphire template substrates. Textured InN layers are deposited on AlN/sapphire and AlGaN/sapphire templates. Arrays of nano-crystalline InN rods with various shapes are grown directly on sapphire substrates. X-ray diffraction rocking curves for the (002)InN reflection have the full width at half maximum (FWHM) as narrow as 270 arcsec for the nano-rods and 460 arcsec for the continuous layers. In x Ga 1-x N layers with InN content up to 10 mol.% are grown on GaN/sapphire templates. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Phase-coherent electron transport in (Zn, Al)Ox thin films grown by atomic layer deposition

    Science.gov (United States)

    Saha, D.; Misra, P.; Ajimsha, R. S.; Joshi, M. P.; Kukreja, L. M.

    2014-11-01

    A clear signature of disorder induced quantum-interference phenomena leading to phase-coherent electron transport was observed in (Zn, Al)Ox thin films grown by atomic layer deposition. The degree of static-disorder was tuned by varying the Al concentration through periodic incorporation of Al2O3 sub-monolayer in ZnO. All the films showed small negative magnetoresistance due to magnetic field suppressed weak-localization effect. The temperature dependence of phase-coherence length ( l φ ∝ T - 3 / 4 ), as extracted from the magnetoresistance measurements, indicated electron-electron scattering as the dominant dephasing mechanism. The persistence of quantum-interference at relatively higher temperatures up to 200 K is promising for the realization of ZnO based phase-coherent electron transport devices.

  9. Phase-coherent electron transport in (Zn, Al)O{sub x} thin films grown by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Saha, D., E-mail: sahaphys@gmail.com, E-mail: pmisra@rrcat.gov.in; Misra, P., E-mail: sahaphys@gmail.com, E-mail: pmisra@rrcat.gov.in; Ajimsha, R. S.; Joshi, M. P.; Kukreja, L. M. [Laser Materials Processing Division, Raja Ramanna Centre for Advanced Technology, Indore 452 013 (India)

    2014-11-24

    A clear signature of disorder induced quantum-interference phenomena leading to phase-coherent electron transport was observed in (Zn, Al)O{sub x} thin films grown by atomic layer deposition. The degree of static-disorder was tuned by varying the Al concentration through periodic incorporation of Al{sub 2}O{sub 3} sub-monolayer in ZnO. All the films showed small negative magnetoresistance due to magnetic field suppressed weak-localization effect. The temperature dependence of phase-coherence length (l{sub φ}∝T{sup −3/4}), as extracted from the magnetoresistance measurements, indicated electron-electron scattering as the dominant dephasing mechanism. The persistence of quantum-interference at relatively higher temperatures up to 200 K is promising for the realization of ZnO based phase-coherent electron transport devices.

  10. Structural Properties of Zinc Oxide Nanorods Grown on Al-Doped Zinc Oxide Seed Layer and Their Applications in Dye-Sensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Kyung Ho Kim

    2014-03-01

    Full Text Available We fabricated zinc oxide (ZnO nanorods (NRs with Al-doped ZnO (AZO seed layers and dye-sensitized solar cells (DSSCs employed the ZnO NRs between a TiO2 photoelectrode and a fluorine-doped SnO2 (FTO electrode. The growth rate of the NRs was strongly dependent on the seed layer conditions, i.e., thickness, Al dopant and annealing temperature. Attaining a large particle size with a high crystallinity of the seed layer was vital to the well-aligned growth of the NRs. However, the growth was less related to the substrate material (glass and FTO coated glass. With optimized ZnO NRs, the DSSCs exhibited remarkably enhanced photovoltaic performance, because of the increase of dye absorption and fast carrier transfer, which, in turn, led to improved efficiency. The cell with the ZnO NRs grown on an AZO seed layer annealed at 350 °C showed a short-circuit current density (JSC of 12.56 mA/cm2, an open-circuit voltage (VOC of 0.70 V, a fill factor (FF of 0.59 and a power conversion efficiency (PCE, η of 5.20% under air mass 1.5 global (AM 1.5G illumination of 100 mW/cm2.

  11. Antibacterial and barrier properties of oriented polymer films with ZnO thin films applied with atomic layer deposition at low temperatures

    International Nuclear Information System (INIS)

    Vähä-Nissi, Mika; Pitkänen, Marja; Salo, Erkki; Kenttä, Eija; Tanskanen, Anne; Sajavaara, Timo; Putkonen, Matti; Sievänen, Jenni; Sneck, Asko; Rättö, Marjaana; Karppinen, Maarit; Harlin, Ali

    2014-01-01

    Concerns on food safety, and need for high quality and extended shelf-life of packaged foods have promoted the development of antibacterial barrier packaging materials. Few articles have been available dealing with the barrier or antimicrobial properties of zinc oxide thin films deposited at low temperature with atomic layer deposition (ALD) onto commercial polymer films typically used for packaging purposes. The purpose of this paper was to study the properties of ZnO thin films compared to those of aluminum oxide. It was also possible to deposit ZnO thin films onto oriented polylactic acid and polypropylene films at relatively low temperatures using ozone instead of water as an oxidizing precursor for diethylzinc. Replacing water with ozone changed both the structure and the chemical composition of films deposited on silicon wafers. ZnO films deposited with ozone contained large grains covered and separated probably by a more amorphous and uniform layer. These thin films were also assumed to contain zinc salts of carboxylic acids. The barrier properties of a 25 nm ZnO thin film deposited with ozone at 100 °C were quite close to those obtained earlier with ALD Al 2 O 3 of similar apparent thickness on similar polymer films. ZnO thin films deposited at low temperature indicated migration of antibacterial agent, while direct contact between ZnO and Al 2 O 3 thin films and bacteria promoted antibacterial activity. - Highlights: • Thin films were grown from diethylzinc also with ozone instead of water at 70 and 100 °C. • ZnO films deposited with diethylzinc and ozone had different structures and chemistries. • Best barrier properties obtained with zinc oxide films close to those obtained with Al 2 O 3 • Ozone as oxygen source provided better barrier properties at 100 °C than water. • Both aluminum and zinc oxide thin films showed antimicrobial activity against E. coli

  12. InN layers grown by the HVPE

    International Nuclear Information System (INIS)

    Syrkin, A.L.; Ivantsov, V.; Usikov, A.; Dmitriev, V.A.; Chambard, G.; Ruterana, P.; Davydov, A.V.; Sundaresan, S.G.; Lutsenko, E.; Mudryi, A.V.; Readinger, E.D.; Chern-Metcalfe, G.D.; Wraback, M.

    2008-01-01

    We report on the properties of high quality HVPE InN and on successful subsequent MBE growth of InN layers with improved characteristics on HVPE InN template substrates. InN layers were grown by HVPE on GaN/sapphire HVPE templates. The (00.2) XRD rocking curve of the best InN layer (RC) had the FWHM of about 375 arc sec, being the narrowest XRD RCs ever reported for HVPE InN. Transmission Electron Microscopy (TEM) revealed that at the GaN/InN interface, the threading dislocations that come from GaN were transmitted into the InN layer. We estimated the dislocation density in HVPE grown InN to be in the low 10 9 cm -2 range. Reflection high energy electron diffraction (RHEED) confirmed monocrystalline structure of the InN layers surface. Layers photoluminescence (PL) showed edge emission around 0.8 eV. Hall measured free electron concentration was in the range of 10 19 -10 20 cm -3 and electron mobility was ∝200 cm 2 /V s. MBE growth of InN was performed on the HVPE grown InN template substrate demonstrating the improvement of material quality in the case of homo-epitaxial growth of InN. Demonstration of the high quality HVPE InN materials opens a new way for InN substrate development. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Optical transparency of graphene layers grown on metal surfaces

    International Nuclear Information System (INIS)

    Rut’kov, E. V.; Lavrovskaya, N. P.; Sheshenya, E. S.; Gall, N. R.

    2017-01-01

    It is shown that, in contradiction with the fundamental results obtained for free graphene, graphene films grown on the Rh(111) surface to thicknesses from one to ~(12–15) single layers do not absorb visible electromagnetic radiation emitted from the surface and influence neither the brightness nor true temperature of the sample. At larger thicknesses, such absorption occurs. This effect is observed for the surfaces of other metals, specifically, Pt(111), Re(1010), and Ni(111) and, thus, can be considered as being universal. It is thought that the effect is due to changes in the electronic properties of thin graphene layers because of electron transfer between graphene and the metal substrate.

  14. Optical transparency of graphene layers grown on metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Rut’kov, E. V. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation); Lavrovskaya, N. P. [State University of Aerospace Instrumentation (Russian Federation); Sheshenya, E. S., E-mail: sheshenayket@gmail.ru; Gall, N. R. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation)

    2017-04-15

    It is shown that, in contradiction with the fundamental results obtained for free graphene, graphene films grown on the Rh(111) surface to thicknesses from one to ~(12–15) single layers do not absorb visible electromagnetic radiation emitted from the surface and influence neither the brightness nor true temperature of the sample. At larger thicknesses, such absorption occurs. This effect is observed for the surfaces of other metals, specifically, Pt(111), Re(1010), and Ni(111) and, thus, can be considered as being universal. It is thought that the effect is due to changes in the electronic properties of thin graphene layers because of electron transfer between graphene and the metal substrate.

  15. Improved ITO thin films for photovoltaic applications with a thin ZnO layer by sputtering

    International Nuclear Information System (INIS)

    Herrero, J.; Guillen, C.

    2004-01-01

    The improvement of the optical and electrical characteristics of indium tin oxide (ITO) layers is pursued to achieve a higher efficiency in its application as frontal electrical contacts in thin film photovoltaic devices. In order to take advantage of the polycrystalline structure of ZnO films as growth support, the properties of ITO layers prepared at room temperature by sputtering onto bare and ZnO-coated substrates have been analyzed using X-ray diffraction, optical and electrical measurements. It has been found that by inserting a thin ZnO layer, the ITO film resistivity can be reduced as compared to that of a single ITO film with similar optical transmittance. The electrical quality improvement is related to ITO grain growth enhancement onto the polycrystalline ZnO underlayer

  16. In-situ ellipsometric characterization of the growth of porous anisotropic nanocrystalline ZnO layers

    Energy Technology Data Exchange (ETDEWEB)

    Laha, P., E-mail: plaha@vub.ac.be; Terryn, H.; Ustarroz, J., E-mail: justarro@vub.ac.be [Research Group Electrochemical and Surface Engineering (SURF), Vrije Universiteit Brussel, Pleinlaan 2, 1050 Elsene, Brussels (Belgium); Nazarkin, M. Y., E-mail: mikleo@mail.ru; Gavrilov, S. A. [Department of Materials of Functional Electronics (MFE), National Research University of Electronic Technology, Bld. 5, Pas. 4806, Zelenograd, Moscow 124498 (Russian Federation); Volkova, A. V.; Simunin, M. M. [Department of Quantum Physics and Nanoelectronics (QPN), National Research University of Electronic Technology, Bld. 5, Pas. 4806, Zelenograd, Moscow 124498 (Russian Federation)

    2015-03-09

    ZnO films have increasingly been in the spotlight due to their largely varied electro-physical and optical properties. For several applications, porous anisotropic nanocrystalline layers are especially interesting. To study the growth kinetics of such films during different fabrication processes, a powerful non-destructive in-situ technique is required. In this work, both ex-situ and in-situ spectroscopic ellipsometry are used along with advanced modelling techniques that are able to take both the anisotropy and the porosity of the films into account. Scanning electron microscopy, along with nitrogen absorption methods for measuring porosity, validated the ellipsometric data and proposed model. The film, grown by chemical bath deposition, was monitored from around 700 to 1800 nm in thickness. This same principle can now be used to monitor any other porous and/or anisotropic structure in an effective in-situ manner, e.g., growth of porous anodic aluminium oxides, nano-porous silica films, etc.

  17. Effects of the aspect ratio on the dye adsorption of ZnO nanorods grown by using a sonochemical method for dye-sensitized solar cells

    International Nuclear Information System (INIS)

    Choi, Seok Cheol; Yun, Won Suk; Sohn, Sang Ho; Oh, Sang Jin

    2012-01-01

    Well-aligned ZnO nanorods for the photoelectrode of dye-sensitized solar cells (DSSCs) were grown via a sonochemical method, and the effects of their aspect ratios on the dye adsorption in DSSCs were studied. The control of the aspect ratio of well-aligned ZnO nanorods was performed by tuning the mole concentration of zinc acetate dehydrate in the range of 0.04 ∼ 0.06M. The dye amounts adsorbed in the ZnO nanorods were estimated from the UV-Visible absorbance by using the Beer-Lambert law. The efficiency of DSSCs with ZnO nanorods was measured to investigate the effects of the aspect ratio of the ZnO nanorods on the dye adsorption properties. A change in the aspect ratio of the ZnO nanorods was founded to yield a change in their dye adsorption ability, resulting in a change in the efficiency of the DSSCs.

  18. ZnO: Hydroquinone superlattice structures fabricated by atomic/molecular layer deposition

    International Nuclear Information System (INIS)

    Tynell, Tommi; Karppinen, Maarit

    2014-01-01

    Here we employ atomic layer deposition in combination with molecular layer deposition to deposit crystalline thin films of ZnO interspersed with single layers of hydroquinone in an effort to create hybrid inorganic–organic superlattice structures. The ratio of the ZnO and hydroquinone deposition cycles is varied between 199:1 and 1:1, and the structure of the resultant thin films is verified with X-ray diffraction and reflectivity techniques. Clear evidence of the formation of a superlattice-type structure is observed in the X-ray reflectivity patterns and the presence of organic bonds in the films corresponding to the structure of hydroquinone is confirmed with Fourier transform infrared spectroscopy measurements. We anticipate that hybrid superlattice structures such as the ones described in this work have the potential to be of great importance for future applications where the precise control of different inorganic and organic layers in hybrid superlattice materials is required. - Highlights: • Inorganic–organic superlattices can be made by atomic/molecular layer deposition. • This is demonstrated here for ZnO and hydroquinone (HQ). • The ratio of the ZnO and HQ layers is varied between 199:1 and 14:1. • The resultant thin films are crystalline

  19. ZnO: Hydroquinone superlattice structures fabricated by atomic/molecular layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Tynell, Tommi; Karppinen, Maarit, E-mail: maarit.karppinen@aalto.fi

    2014-01-31

    Here we employ atomic layer deposition in combination with molecular layer deposition to deposit crystalline thin films of ZnO interspersed with single layers of hydroquinone in an effort to create hybrid inorganic–organic superlattice structures. The ratio of the ZnO and hydroquinone deposition cycles is varied between 199:1 and 1:1, and the structure of the resultant thin films is verified with X-ray diffraction and reflectivity techniques. Clear evidence of the formation of a superlattice-type structure is observed in the X-ray reflectivity patterns and the presence of organic bonds in the films corresponding to the structure of hydroquinone is confirmed with Fourier transform infrared spectroscopy measurements. We anticipate that hybrid superlattice structures such as the ones described in this work have the potential to be of great importance for future applications where the precise control of different inorganic and organic layers in hybrid superlattice materials is required. - Highlights: • Inorganic–organic superlattices can be made by atomic/molecular layer deposition. • This is demonstrated here for ZnO and hydroquinone (HQ). • The ratio of the ZnO and HQ layers is varied between 199:1 and 14:1. • The resultant thin films are crystalline.

  20. Photoluminescence properties of ZnO thin films grown by using the hydrothermal technique

    International Nuclear Information System (INIS)

    Sahoo, Trilochan; Jang, Leewoon; Jeon, Juwon; Kim, Myoung; Kim, Jinsoo; Lee, Inhwan; Kwak, Joonseop; Lee, Jaejin

    2010-01-01

    The photoluminescence properties of zinc-oxide thin films grown by using the hydrothermal technique have been investigated. Zinc-oxide thin films with a wurtzite symmetry and c-axis orientation were grown in aqueous solution at 90 .deg. C on sapphire substrates with a p-GaN buffer layer by using the hydrothermal technique. The low-temperature photoluminescence analysis revealed a sharp bound-exciton-related luminescence peak at 3.366 eV with a very narrow peak width. The temperature-dependent variations of the emission energy and of the integrated intensity were studied. The activation energy of the bound exciton complex was calculated to be 7.35 ± 0.5 meV from the temperature dependent quenching of the integral intensities.

  1. Structural and optical properties of ZnO rods hydrothermally formed on polyethersulfone substrates

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Chang Mi; Jang, Jin Tak; Kim, Chang Yong; Ryu, Hyuk Hyun [Inje University, Gimhae (Korea, Republic of); Lee, Won Jae [Dong-Eui University, Busan (Korea, Republic of); Chang, Ji Ho [Korea Maritime University, Busan (Korea, Republic of); Son, Chang Sik [Silla University, Busan (Korea, Republic of); Choi, Hee Lack [Pukyong National University, Busan (Korea, Republic of)

    2012-06-15

    Various unique ZnO morphologies, such as cigar-like and belt-like structures and microrod and nanorod structures, were formed on flexible polyethersulfone (PES) substrates by using a low temperature hydrothermal route. The structural properties of ZnO depended highly on the precursor concentration. The effect of a thin ZnO seed layer deposited the on PES substrate by using atomic layer deposition on the structural and the optical properties of ZnO hydrothermally grown on the ZnO seed layer/PES substrates was studied. Field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and photoluminescence (PL) measurements were employed to analyze the characteristics of hydrothermally-grown ZnO. The diameter of the ZnO nanorods grown on the ZnO seed layer/PES substrates increased with increasing precursor concentration from 0.025 to 0.125 M due to the Ostwald ripening process. ZnO hydrothermally-grown on the ZnO seed layer/PES substrates at a low precursor concentration showed better structural properties than ZnO formed without a seed layer. Well-formed ZnO nanorods deposited on the ZnO seed layer/PES substrates showed two PL peaks, one in the ultraviolet and the other in the visible region, whereas horizontally positioned ZnO formed on the PES substrate in the absence of a seed layer emitted only one broad PL peak in the violet region. The ZnO grown on PES substrates in this work can be used as high-quality transparent electrodes for solar cells fabricated on flexible substrates.

  2. Structural and optical properties of ZnO rods hydrothermally formed on polyethersulfone substrates

    International Nuclear Information System (INIS)

    Shin, Chang Mi; Jang, Jin Tak; Kim, Chang Yong; Ryu, Hyuk Hyun; Lee, Won Jae; Chang, Ji Ho; Son, Chang Sik; Choi, Hee Lack

    2012-01-01

    Various unique ZnO morphologies, such as cigar-like and belt-like structures and microrod and nanorod structures, were formed on flexible polyethersulfone (PES) substrates by using a low temperature hydrothermal route. The structural properties of ZnO depended highly on the precursor concentration. The effect of a thin ZnO seed layer deposited the on PES substrate by using atomic layer deposition on the structural and the optical properties of ZnO hydrothermally grown on the ZnO seed layer/PES substrates was studied. Field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and photoluminescence (PL) measurements were employed to analyze the characteristics of hydrothermally-grown ZnO. The diameter of the ZnO nanorods grown on the ZnO seed layer/PES substrates increased with increasing precursor concentration from 0.025 to 0.125 M due to the Ostwald ripening process. ZnO hydrothermally-grown on the ZnO seed layer/PES substrates at a low precursor concentration showed better structural properties than ZnO formed without a seed layer. Well-formed ZnO nanorods deposited on the ZnO seed layer/PES substrates showed two PL peaks, one in the ultraviolet and the other in the visible region, whereas horizontally positioned ZnO formed on the PES substrate in the absence of a seed layer emitted only one broad PL peak in the violet region. The ZnO grown on PES substrates in this work can be used as high-quality transparent electrodes for solar cells fabricated on flexible substrates.

  3. Characterization of spatial manipulation on ZnO nanocomposites consisting of Au nanoparticles, a graphene layer, and ZnO nanorods

    Science.gov (United States)

    Huang, Shen-Che; Lu, Chien-Cheng; Su, Wei-Ming; Weng, Chen-Yuan; Chen, Yi-Cian; Wang, Shing-Chung; Lu, Tien-Chang; Chen, Ching-Pang; Chen, Hsiang

    2018-01-01

    Three types of ZnO-based nanocomposites were fabricated consisting of 80-nm Au nanoparticles (NPs), a graphene layer, and ZnO nanorods (NRs). To investigate interactions between the ZnO NRs and Au nanoparticle, multiple material analysis techniques including field-emission scanning electron microscopy (FESEM), surface contact angle measurements, secondary ion mass spectrometry (SIMS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopic characterizations were performed. Results indicate that incorporating a graphene layer could block the interaction between the ZnO NRs and the Au NPs. Furthermore, the Raman signal of the Au NPs could be enhanced by inserting a graphene layer on top of the ZnO NRs. Investigation of these graphene-incorporated nanocomposites would be helpful to future studies of the physical properties and Raman analysis of the ZnO-based nanostructure design.

  4. Dimensional crossover of electron weak localization in ZnO/TiO{sub x} stacked layers grown by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Saha, D., E-mail: sahaphys@gmail.com, E-mail: pmisra@rrcat.gov.in; Misra, P., E-mail: sahaphys@gmail.com, E-mail: pmisra@rrcat.gov.in; Joshi, M. P.; Kukreja, L. M. [Laser Materials Processing Division, Raja Ramanna Centre for Advanced Technology, Indore 452 013 (India); Bhartiya, S. [Laser Materials Development & Devices Division, Raja Ramanna Centre for Advanced Technology, Indore 452 013 (India); Gupta, M. [UGC-DAE Consortium for Scientific Research, Indore 452 017 (India)

    2016-01-25

    We report on the dimensional crossover of electron weak localization in ZnO/TiO{sub x} stacked layers having well-defined and spatially-localized Ti dopant profiles along film thickness. These films were grown by in situ incorporation of sub-monolayer TiO{sub x} on the growing ZnO film surface and subsequent overgrowth of thin conducting ZnO spacer layer using atomic layer deposition. Film thickness was varied in the range of ∼6–65 nm by vertically stacking different numbers (n = 1–7) of ZnO/TiO{sub x} layers of nearly identical dopant-profiles. The evolution of zero-field sheet resistance (R{sub ◻}) versus temperature with decreasing film thickness showed a metal to insulator transition. On the metallic side of the metal-insulator transition, R{sub ◻}(T) and magnetoresistance data were found to be well corroborated with the theoretical framework of electron weak localization in the diffusive transport regime. The temperature dependence of both R{sub ◻} and inelastic scattering length provided strong evidence for a smooth crossover from 2D to 3D weak localization behaviour. Results of this study provide deeper insight into the electron transport in low-dimensional n-type ZnO/TiO{sub x} stacked layers which have potential applications in the field of transparent oxide electronics.

  5. Effects of Post Heat Treatments on ZnO Thin-Films Grown on Zn-coated Teflon Substrates

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ikhyun; Nam, Giwoong; Lee, Cheoleon; Kim, Dongwhan; Choi, Hyonkwang; Kim, Yangsoo; Leem, Jae-Young [Inje University, Gimhae (Korea, Republic of); Kim, Jin Soo [Chonbuk National University, Jeonju (Korea, Republic of); Kim, Jong Su [Yeungnam University, Gyeongsan (Korea, Republic of); Son, Jeong-Sik [Kyungwoon University, Gumi (Korea, Republic of)

    2015-06-15

    ZnO thin films were first grown on Zn-coated Teflon substrates using a spin-coating method, with various post-heating temperatures. The structural and optical properties of the ZnO thin films were then investigated using field-effect scanning-electron microscopy, X-ray diffractometry, and photoluminescence (PL) spectroscopy. The surface morphology of these ZnO thin films exhibited dendritic structures. With increasing post-heating temperature, all samples preferentially exhibited preferential c-axis orientation and increased residual tensile stress. All of the films exhibited preferential c-axis orientation, and the residual tensile stress of those increased with increasing post-heating temperature. The near-band-edge emission (NBE) peaks were red-shifted after post-heating treatment at 400 ℃. The intensity of the deep-level emission (DLE) peaks gradually decreased with increasing post- heating temperature. Moreover, the narrowest ‘full width at half maximum’ (FWHM) and the highest intensity ratio of the NBE to the DLE for thin films, were observed after post-heating at 400 ℃. The ZnO thin films fabricated with the 400 ℃ post-heating process provided the highest crystallinity and optical properties.

  6. Photoluminescence quenching, structures, and photovoltaic properties of ZnO nanostructures decorated plasma grown single walled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Aïssa, Brahim, E-mail: brahim.aissa@mpbc.ca [University of Quebec, Centre Énergie, Matériaux et Télécommunications, INRS-EMT (Canada); Nedil, Mourad [Telebec Wireless Underground Communication Laboratory, UQAT (Canada); Belaidi, Abdelhak; Isaifan, Rima J. [Hamad Bin Khalifa University, Qatar Foundation, Qatar Environment and Energy Research Institute (Qatar); Bentouaf, Ali [University Hassiba Ben Bouali, Physics Department, Faculty of Science (Algeria); Fauteux, Christian; Therriault, Daniel [École Polytechnique de Montréal, Laboratory for Multiscale Mechanics (LM2), Mechanical Engineering Department (Canada)

    2017-05-15

    Zinc oxide (ZnO) nanostructures were successfully grown directly on single walled carbon nanotubes (SWCNT) template through the CO{sub 2} laser-induced chemical liquid deposition (LCLD) process. Photoluminescence (PL) of the deposited ZnO/SWCNT hybrid composites exhibits, at room temperature, a narrow near UV band located at 390 nm with no emission bands in the visible region, indicating a high degree of crystalline quality of the ZnO nanostructures. Moreover, when the relative SWCNT loads are varied within the composites, the PL intensity and the diffused optical reflectance diminish in comparison with those of ZnO alone, owing to the transfer of photo-excited electrons from ZnO to the SWCNT, and the enhancement of the optical absorbance, respectively. Finally, these ZnO/SWCNT hybrid composites are integrated into a heterojunction photovoltaic-based device, using PEDOT:PSS on ITO/glass substrate. The devices show an evident p–n junction behavior in the dark, and a clear I–V curve shift downward when illuminated with an open-circuit voltage of 1.1 V, a short circuit current density of 14.05 μA cm{sup −2}, and a fill factor of ∼35%. These results indicate that these composites fabricated via LCLD process could be promising for optoelectronic and energy-harvesting devices.

  7. Epitaxially Grown Layered MFI–Bulk MFI Hybrid Zeolitic Materials

    KAUST Repository

    Kim, Wun-gwi

    2012-11-27

    The synthesis of hybrid zeolitic materials with complex micropore-mesopore structures and morphologies is an expanding area of recent interest for a number of applications. Here we report a new type of hybrid zeolite material, composed of a layered zeolite material grown epitaxially on the surface of a bulk zeolite material. Specifically, layered (2-D) MFI sheets were grown on the surface of bulk MFI crystals of different sizes (300 nm and 10 μm), thereby resulting in a hybrid material containing a unique morphology of interconnected micropores (∼0.55 nm) and mesopores (∼3 nm). The structure and morphology of this material, referred to as a "bulk MFI-layered MFI" (BMLM) material, was elucidated by a combination of XRD, TEM, HRTEM, SEM, TGA, and N2 physisorption techniques. It is conclusively shown that epitaxial growth of the 2-D layered MFI sheets occurs in at least two principal crystallographic directions of the bulk MFI crystal and possibly in the third direction as well. The BMLM material combines the properties of bulk MFI (micropore network and mechanical support) and 2-D layered MFI (large surface roughness, external surface area, and mesoporosity). As an example of the uses of the BMLM material, it was incorporated into a polyimide and fabricated into a composite membrane with enhanced permeability for CO2 and good CO2/CH4 selectivity for gas separations. SEM-EDX imaging and composition analysis showed that the polyimide and the BMLM interpenetrate into each other, thereby forming a well-adhered polymer/particle microstructure, in contrast with the defective interfacial microstructure obtained using bare MFI particles. Analysis of the gas permeation data with the modified Maxwell model also allows the estimation of the effective volume of the BMLM particles, as well as the CO2 and CH4 gas permeabilities of the interpenetrated layer at the BMLM/polyimide interface. © 2012 American Chemical Society.

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

    Indian Academy of Sciences (India)

    Zinc oxide (ZnO) is a II–VI compound semiconductor with a wide direct energy .... observed by scanning electron microscope (SEM/JEOL–. JSM 5140) ... SEM images of ZnO NWs growth on ITO–glass at argon to oxygen flow rate = 200/20 ...

  9. Influence of annealing temperature on ZnO thin films grown by dual ...

    Indian Academy of Sciences (India)

    Administrator

    In electrical characterization as well, when annealing temperature was increased .... of ZnO (002) peaks and (c) crystallite size and stress generation on ZnO thin films ... sufficient kinetic energy and surface mobility to occupy stable positions ...

  10. Graphene-Tapered ZnO Nanorods Array as a Flexible Antireflection Layer

    Directory of Open Access Journals (Sweden)

    Taeseup Song

    2015-01-01

    Full Text Available Flexible solar cells have drawn a great deal of attention due to their various advantages including deformable and wearable characteristics. In the solar cells, the antireflection layer plays an important role in the improvement in the conversion efficiency by increasing the light transmission and suppressing the Fresnel refraction. For the successful implantation of the antireflection layer into the flexible solar cells, the flexible mechanical property of the antireflection layer is also necessary. However, the study on flexible antireflection layer for the flexible solar cells or optoelectronics is still lacking. In this study, we report the graphene-tapered ZnO nanorods array as a flexible antireflection layer for the application in flexible solar cells. Flexible two-dimensional graphene sheet and the tapered morphology of ZnO nanorods enable conformal coverage on the flexible substrate with curved surface and significant improvements in antireflection properties, respectively.

  11. Chemical-bath ZnO buffer layer for CuInS{sub 2} thin-film solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Ennaoui, A.; Weber, M.; Scheer, R.; Lewerenz, H.J. [Hahn-Meitner-Institut, Abt. Grenzflaechen, Bereich Physikalische Chemie, Glienicker Strasse 100, D-14109 Berlin (Germany)

    1998-07-13

    ZnO buffer layers were grown by a chemical-bath deposition (CBD) in order to improve the interface quality in p-CuInS{sub 2} based solar cells, to improve the light transmission in the blue wavelength region, but also as an alternative to eliminate the toxic cadmium. The process consists of immersion of different substrates (glass, CIS) in a dilute solution of tetraamminezinc II, [Zn(NH{sub 2}){sub 4}]{sup 2+}, complex at 60-95C. During the growth process, a homogeneous growth mechanism which proceeds by the sedimentation of a mixture of ZnO and Zn(OH){sub 2} clusters formed in solution, competes with the heterogeneous growth mechanism. The mechanism consists of specific adsorption of a complex Zn(II) followed by a chemical reaction. The last process of growth results in thin, hard, adherent and specularly reflecting films. The characterization of the deposited CBD-ZnO layers was performed by X-ray diffraction (XRD), optical transmittance, scanning electron microscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The as-deposited films on glass show hexagonal zincite structure with two preferred orientations (1 0 0) and (1 0 1). High optical transmittance up to 80% in the near-infrared and part of the visible region was observed. The low growth rate of the films on CIS suggests an atomic layer-by-layer growth process.The device parameters and performance are compared to heterojunction with a standard CdS buffer layer

  12. Optical and structural properties of Mn-doped ZnO nanorods grown by aqueous chemical growth for spintronic applications

    Energy Technology Data Exchange (ETDEWEB)

    Strelchuk, V.V. [V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine, 45 Nauky pr., 03028 Kyiv (Ukraine); Nikolenko, A.S., E-mail: nikolenko_mail@ukr.net [V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine, 45 Nauky pr., 03028 Kyiv (Ukraine); Kolomys, O.F.; Rarata, S.V.; Avramenko, K.A.; Lytvyn, P.M. [V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine, 45 Nauky pr., 03028 Kyiv (Ukraine); Tronc, P. [Centre National de la Recherche Scientifique, Ecole Superieure de Physique et de Chimie Industrielles de la Ville de Paris, 10 rue Vauquelin, 75005 Paris (France); Chey, Chan Oeurn; Nur, Omer; Willander, Magnus [Department of Science and Technology, Linköping University, 601 74 Norrköping (Sweden)

    2016-02-29

    The effect of Mn-doping on the structural, morphological, optical and magnetic properties of the ZnO:Mn nanorods (NRs) synthesized by aqueous chemical process is reported. Grown ZnO:Mn NRs are shown to have hexagonal end facets and the diameters increasing with nominal Mn content. Optical absorption measurements show a decrease in optical band gap with increase of Mn concentration. Raman spectroscopy revealed significant modification of the lattice vibrational properties of the ZnO matrix upon Mn doping. The additional Mn-related vibrational mode, intensity of which increases with amount of Mn can be regarded as an evidence of Mn incorporation into the host lattice of the ZnO. At high Mn concentrations, coexistence of hexagonal Zn{sub 1−x}Mn{sub x}O phase along with the secondary phases of ZnMn{sub 2}O{sub 4} cubic spinel is revealed. Magnetic properties of ZnO:Mn NRs are studied by combinatorial atomic force microscopy and magnetic force microscopy imaging, and obtained clear magnetic contrast at room temperature provides a strong evidence of ferromagnetic behavior. - Highlights: • Synthesis of Mn-doped ZnO nanorods by hydrothermal method is demonstrated. • Doping with Mn significantly changes the morphology of ZnO nanorods. • Additional Mn-induced Raman modes evidence incorporation of Mn into ZnO matrix. • Formation of secondary ZnMn{sub 2}O{sub 4} spinel phase is found at high Mn concentrations. • Contrast MFM images of ZnO:Mn nanorods indicate ferromagnetism at room temperature.

  13. Suppression of Mg propagation into subsequent layers grown by MOCVD

    Science.gov (United States)

    Agarwal, Anchal; Tahhan, Maher; Mates, Tom; Keller, Stacia; Mishra, Umesh

    2017-01-01

    Low temperature (LT) flow modulation epitaxy (FME) or "pulsed" growth was successfully used to prevent magnesium from Metalorganic Chemical Vapor Deposition (MOCVD) grown p-GaN:Mg layers riding into subsequently deposited n-type layers. Mg concentration in the subsequent layers was lowered from ˜1 × 1018 cm-3 for a medium temperature growth at 950 °C to ˜1 × 1016 cm-3 for a low temperature growth at 700 °C via FME. The slope of the Mg concentration drop in the 700 °C FME sample was 20 nm/dec—the lowest ever demonstrated by MOCVD. For growth on Mg implanted GaN layers, the drop for a medium temperature regrowth at 950 °C was ˜10 nm/dec compared to >120 nm/dec for a high temperature regrowth at 1150 °C. This drop-rate obtained at 950 °C or lower was maintained even when the growth temperature in the following layers was raised to 1150 °C. A controlled silicon doping series using LT FME was also demonstrated with the lowest and highest achieved doping levels being 5 × 1016 cm-3 and 6 × 1019 cm-3, respectively.

  14. Effects of thermal annealing temperature and duration on hydrothermally grown ZnO nanorod arrays

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, X.Q.; Kim, C.R.; Lee, J.Y.; Shin, C.M.; Heo, J.H.; Leem, J.Y. [Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Obang-dong, Gimhae, Gyeongnam 621-749 (Korea, Republic of); Ryu, H. [Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Obang-dong, Gimhae, Gyeongnam 621-749 (Korea, Republic of)], E-mail: hhryu@inje.ac.kr; Chang, J.H. [Major of Nano Semiconductor, Korea Maritime University, 1 Dongsam-dong, Yeongdo-Ku, Busan 606-791 (Korea, Republic of); Lee, H.C. [Department of Mechatronics Engineering, Korea Maritime University, 1 Dongsam-dong, Yeongdo-Ku, Busan 606-791 (Korea, Republic of); Son, C.S. [Department of Electronic Materials Engineering, Silla University, Gwaebeop-dong, Sasang-gu, Busan 617-736 (Korea, Republic of); Shin, B.C.; Lee, W.J. [Department of Nano Engineering, Dong-Eui University, 995 Eomgwangno, Busanjin-gu, Busan 614-714 (Korea, Republic of); Jung, W.G. [School of Advanced Materials Engineering, Kookmin University, 861-1, Jeongneung-dong, Seongbuk-gu, Seoul 136-702 (Korea, Republic of); Tan, S.T. [Institute of Microelectronics, 11 Science Park Road, Science Park II, Singapore 117685 (Singapore); Zhao, J.L. [School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore); Sun, X.W. [Institute of Microelectronics, 11 Science Park Road, Science Park II, Singapore 117685 (Singapore); School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore)

    2009-03-15

    In this study, the effects of thermal annealing temperature and duration on ZnO nanorod arrays fabricated by hydrothermal method were investigated. The annealed ZnO/Si(1 1 1) substrate was used for ZnO nanorod array growth. The effects of annealing treatment on the structural and optical properties were investigated by scanning electron microscopy, X-ray diffraction, and room-temperature photoluminescence measurements. With the annealing temperature of 750 {sup o}C and the annealing duration of 10 min, both the structural and optical properties of the ZnO nanorod arrays improved significantly, as indicated in the X-ray diffraction and photoluminescence measurement.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-08-25

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

  16. The optical properties of ZnO films grown on porous Si templates

    International Nuclear Information System (INIS)

    Liu, Y L; Liu, Y C; Yang, H; Wang, W B; Ma, J G; Zhang, J Y; Lu, Y M; Shen, D Z; Fan, X W

    2003-01-01

    ZnO films were electrodeposited on porous silicon templates with different porosities. The photoluminescence (PL) spectra of the samples before and after deposition of ZnO were measured to study the effect of template porosity on the luminescence properties of ZnO/porous Si composites. As-prepared porous Si (PS) templates emit strong red light. The red PL peak of porous Si after deposition of ZnO shows an obvious blueshift, and the trend of blueshift increases with an increase in template porosity. A green emission at about 550 nm was also observed when the porosity of template increases, which is ascribed to the deep-level emission band of ZnO. A model-based band diagram of the ZnO/porous Si composite is suggested to interpret the properties of the composite

  17. Ambient Layer-by-Layer ZnO Assembly for Highly Efficient Polymer Bulk Heterojunction Solar Cells

    KAUST Repository

    Eita, Mohamed Samir

    2015-02-04

    The use of metal oxide interlayers in polymer solar cells has great potential because metal oxides are abundant, thermally stable, and can be used in fl exible devices. Here, a layer-by-layer (LbL) protocol is reported as a facile, room-temperature, solution-processed method to prepare electron transport layers from commercial ZnO nanoparticles and polyacrylic acid (PAA) with a controlled and tunable porous structure, which provides large interfacial contacts with the active layer. Applying the LbL approach to bulk heterojunction polymer solar cells with an optimized ZnO layer thickness of H25 nm yields solar cell power-conversion effi ciencies (PCEs) of ≈6%, exceeding the effi ciency of amorphous ZnO interlayers formed by conventional sputtering methods. Interestingly, annealing the ZnO/PAA interlayers in nitrogen and air environments in the range of 60-300 ° C reduces the device PCEs by almost 20% to 50%, indicating the importance of conformational changes inherent to the PAA polymer in the LbL-deposited fi lms to solar cell performance. This protocol suggests a new fabrication method for solution-processed polymer solar cell devices that does not require postprocessing thermal annealing treatments and that is applicable to fl exible devices printed on plastic substrates.

  18. Atomic Layer Deposition of Nickel on ZnO Nanowire Arrays for High-Performance Supercapacitors.

    Science.gov (United States)

    Ren, Qing-Hua; Zhang, Yan; Lu, Hong-Liang; Wang, Yong-Ping; Liu, Wen-Jun; Ji, Xin-Ming; Devi, Anjana; Jiang, An-Quan; Zhang, David Wei

    2018-01-10

    A novel hybrid core-shell structure of ZnO nanowires (NWs)/Ni as a pseudocapacitor electrode was successfully fabricated by atomic layer deposition of a nickel shell, and its capacitive performance was systemically investigated. Transmission electron microscopy and X-ray photoelectron spectroscopy results indicated that the NiO was formed at the interface between ZnO and Ni where the Ni was oxidized by ZnO during the ALD of the Ni layer. Electrochemical measurement results revealed that the Ti/ZnO NWs/Ni (1500 cycles) electrode with a 30 nm thick Ni-NiO shell layer had the best supercapacitor properties including ultrahigh specific capacitance (∼2440 F g -1 ), good rate capability (80.5%) under high current charge-discharge conditions, and a relatively better cycling stability (86.7% of the initial value remained after 750 cycles at 10 A g -1 ). These attractive capacitive behaviors are mainly attributed to the unique core-shell structure and the combined effect of ZnO NW arrays as short charge transfer pathways for ion diffusion and electron transfer as well as conductive Ni serving as channel for the fast electron transport to Ti substrate. This high-performance Ti/ZnO NWs/Ni hybrid structure is expected to be one of a promising electrodes for high-performance supercapacitor applications.

  19. Variation of microstructural and optical properties in SILAR grown ZnO thin films by thermal treatment.

    Science.gov (United States)

    Valanarasu, S; Dhanasekaran, V; Chandramohan, R; Kulandaisamy, I; Sakthivelu, A; Mahalingam, T

    2013-08-01

    The influence of thermal treatment on the structural and morphological properties of the ZnO films deposited by double dip Successive ionic layer by adsorption reaction is presented. The effect of annealing temperature and time in air ambient is presented in detail. The deposited films were annealed from 200 to 400 degrees C in air and the structural properties were determined as a function of annealing temperature by XRD. The studies revealed that films were exhibiting preferential orientation along (002) plane. The other structural parameters like the crystallite size (D), micro strain (epsilon), dislocation density (delta) and stacking fault (alpha) of as-deposited and annealed ZnO films were evaluated and reported. The optical properties were also studied and the band gap of the ZnO thins films varied from 3.27 to 3.04 eV with the annealing temperature. SEM studies revealed that the hexagonal shaped grains with uniformly distributed morphology in annealed ZnO thin films. It has been envisaged using EDX analysis that the near stoichiometric composition of the film can be attained by thermal treatment during which microstructural changes do occur.

  20. Sims Characterisation of ZnO Layer Prepared By Pulsed Laser Deposition

    Directory of Open Access Journals (Sweden)

    Andrej Vincze

    2005-01-01

    Full Text Available New material development requires new technologies to create and prepare basic material for semiconductor industry and device applications. Materials have given properties, which exhibit particulary small tolerances. One of the most important and promising material is recently ZnO. ZnO has specific properties for near UV emission and absorption optical devices. The pulsed laser deposition (PLD is one of the methods to prepare this type of material. The aim of this paper is to compare properties of ZnO layers deposited from pure Zn target in oxygen atmosphere and the analysis of their surface properties by secondary ion mass spectroscopy (SIMS, atomic force microscopy (AFM and scanning electron microscopy (SEM.

  1. Selective tuning of enhancement in near band edge emission in hydrothermally grown ZnO nanorods coated with gold

    Energy Technology Data Exchange (ETDEWEB)

    Dixit, Tejendra, E-mail: phd12110211@iiti.ac.in [Molecular and Nanoelectronics Research Group (MNRG), Department of Electrical Engineering, IIT Indore, Indore, Madhya Pradesh (India); Palani, I.A., E-mail: palaniia@iiti.ac.in [Mechatronics and Instrumentation Lab, Department of Mechanical Engineering, IIT Indore, Indore, Madhya Pradesh (India); Centre of Material Science and Engineering, IIT Indore, Indore, Madhya Pradesh (India); Singh, Vipul, E-mail: vipul@iiti.ac.in [Molecular and Nanoelectronics Research Group (MNRG), Department of Electrical Engineering, IIT Indore, Indore, Madhya Pradesh (India); Centre of Material Science and Engineering, IIT Indore, Indore, Madhya Pradesh (India)

    2016-02-15

    The room-temperature photoluminescence (PL) spectra of hydrothermally grown ZnO nanorods (NRs) coated with Au using dc sputtering and thermal evaporation were systematically investigated. Au coated (via dc sputtering) ZnO NRs were found to exhibit very large near band edge emission enhancement, on the contrary Au coated (via thermal evaporation) ZnO NRs showed suppression in the near band edge emission peak. These observed results were further confirmed by excitation intensity (EI) dependent PL spectra of different samples. Further using Raman spectra it has been observed that the longitudinal optical (LO) phonons exhibit an enhancement and a weakening by the Au coatings, using dc sputtering and thermal evaporation respectively. Finally by controlling the concentration of KMnO{sub 4} as an additive during the hydrothermal growth, selective tuning in the defect density was carried out, which was later utilized to probe the effect of defect density of the Au–ZnO plasmonic coupling. Moreover, our results strongly suggest that the EI dependent PL has a strong dependence on the metal coating technique. The findings presented in this article clearly indicate the dependence of Au–ZnO plasmonic coupling on the overall defect density and the process of Au deposition.

  2. Current-transport studies and trap extraction of hydrothermally grown ZnO nanotubes using gold Schottky diode

    Energy Technology Data Exchange (ETDEWEB)

    Amin, G.; Hussain, I.; Zaman, S.; Bano, N.; Nur, O.; Willander, M. [Department of Science and Technology, Campus Norrkoeping, Linkoeping University, 60174 Norrkoeping (Sweden)

    2010-03-15

    High-quality zinc oxide (ZnO) nanotubes (NTs) were grown by the hydrothermal technique on n-Si substrate. The room temperature (RT) current-transport mechanisms of Au Schottky diodes fabricated from ZnO NTs and nanorods (NRs) reference samples have been studied and compared. The tunneling mechanisms via deep-level states was found to be the main conduction process at low applied voltage but at the trap-filled limit voltage (V{sub TFL}) all traps were filled and the space-charge-limited current conduction was the dominating current-transport mechanism. The deep-level trap energy and the trap concentration for the NTs were obtained as {proportional_to}0.27 eV and 2.1 x 10{sup 16} cm{sup -3}, respectively. The same parameters were also extracted for the ZnO NRs. The deep-level states observed crossponds to zinc interstitials (Zn{sub i}), which are responsible for the violet emission. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  3. ZnO buffer layer for metal films on silicon substrates

    Science.gov (United States)

    Ihlefeld, Jon

    2014-09-16

    Dramatic improvements in metallization integrity and electroceramic thin film performance can be achieved by the use of the ZnO buffer layer to minimize interfacial energy between metallization and adhesion layers. In particular, the invention provides a substrate metallization method utilizing a ZnO adhesion layer that has a high work of adhesion, which in turn enables processing under thermal budgets typically reserved for more exotic ceramic, single-crystal, or metal foil substrates. Embodiments of the present invention can be used in a broad range of applications beyond ferroelectric capacitors, including microelectromechanical systems, micro-printed heaters and sensors, and electrochemical energy storage, where integrity of metallized silicon to high temperatures is necessary.

  4. Epitaxial properties of ZnO thin films on SrTiO3 substrates grown by laser molecular beam epitaxy

    International Nuclear Information System (INIS)

    Wei, X. H.; Li, Y. R.; Zhu, J.; Huang, W.; Zhang, Y.; Luo, W. B.; Ji, H.

    2007-01-01

    Epitaxial ZnO thin films with different orientations have been grown by laser molecular beam epitaxy on (001)- (011)-, and (111)-orientated SrTiO 3 single-crystal substrates. The growth behavior was in situ monitored by reflection high-energy electron diffraction, and the epitaxial orientation relations were reconfirmed by ex situ x-ray diffraction measurements. In the case of ZnO on SrTiO 3 (001), four orthogonal domains coexisted in the ZnO epilayer, i.e., ZnO(110) parallel SrTiO 3 (001) and ZnO[-111] parallel SrTiO 3 . For (011)- and (111)-orientated substrates, single-domain epitaxy with c axial orientation was observed, in which the in-plane relationship was ZnO[110] parallel SrTiO 3 [110] irrespective of the substrate orientations. Additionally, the crystalline quality of ZnO on SrTiO 3 (111) was better than that of ZnO on SrTiO 3 (011) because of the same symmetry between the (111) substrates and (001) films. The obtained results can be attributed to the difference of the in-plane crystallographic symmetry. Furthermore, those alignments can be explained by the interface stress between the substrates and the films

  5. Stability and dewetting kinetics of thin gold films on Ti, TiOx and ZnO adhesion layers

    International Nuclear Information System (INIS)

    Schaefer, Brian T.; Cheung, Jeffrey; Ihlefeld, Jon F.; Jones, Jacob L.; Nagarajan, Valanoor

    2013-01-01

    We present an in situ high-temperature confocal laser microscopy study on the thermal stability of 40 nm thick gold thin films grown on 40 nm Ti, TiO x and ZnO adhesion layers on (0 0 1) Si. In situ observation of the dewetting process was performed over a wide range of set temperatures (400–800 °C) and ramp rates (10–50 °C min −1 ) for each gold/adhesion layer combination. We found that significant dewetting and subsequent formation of gold islands occurs only at and above 700 °C for all adhesion layers. The dewetting is driven to equilibrium for gold/ZnO compared to gold/Ti and gold/TiO x as confirmed by ex situ X-ray diffraction and scanning electron microscopy characterization. Quantification of the in situ data through stretched exponential kinetic models reveals an underlying apparent activation energy of the dewetting process. This energy barrier for dewetting is higher for gold/Ti and gold/TiO x compared to gold/ZnO, thus confirming the ex situ observations. We rationalize that these apparent activation energies correspond to the underlying thermal stability of each gold/adhesion layer system

  6. Template-controlled piezoactivity of ZnO thin films grown via a bioinspired approach

    Directory of Open Access Journals (Sweden)

    Nina J. Blumenstein

    2017-01-01

    Full Text Available Biomaterials are used as model systems for the deposition of functional inorganic materials under mild reaction conditions where organic templates direct the deposition process. In this study, this principle was adapted for the formation of piezoelectric ZnO thin films. The influence of two different organic templates (namely, a carboxylate-terminated self-assembled monolayer and a sulfonate-terminated polyelectrolyte multilayer on the deposition and therefore on the piezoelectric performance was investigated. While the low negative charge of the COOH-SAM is not able to support oriented attachment of the particles, the strongly negatively charged sulfonated polyelectrolyte leads to texturing of the ZnO film. This texture enables a piezoelectric performance of the material which was measured by piezoresponse force microscopy. This study shows that it is possible to tune the piezoelectric properties of ZnO by applying templates with different functionalities.

  7. ZnO nanorod arrays grown under different pressures and their photoluminescence properties

    Energy Technology Data Exchange (ETDEWEB)

    Meng Xiuqing [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 16 East Nan-Hu Road, Open Economic ZoneChangchun 130033 (China); Graduate School of the Chinese Academy of Sciences (China); Zhao Dongxu [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 16 East Nan-Hu Road, Open Economic ZoneChangchun 130033 (China)]. E-mail: dxzhao2000@yahoo.com.cn; Shen Dezhen [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 16 East Nan-Hu Road, Open Economic ZoneChangchun 130033 (China); Zhang Jiying [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 16 East Nan-Hu Road, Open Economic ZoneChangchun 130033 (China); Li Binghui [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 16 East Nan-Hu Road, Open Economic ZoneChangchun 130033 (China); Wang Xiaohua [National Key Laboratory of High Power Semiconductor Laser, Changchun University of Science and technology, 7089 Weixing Road Changchun (China); Fan Xiwu [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 16 East Nan-Hu Road, Open Economic ZoneChangchun 130033 (China)

    2007-01-15

    The ZnO nanorod arrays were synthesized via a simple vapor deposition method on Si (1 1 1) substrates at a low growth temperature of 520 deg. C. By selecting different source materials under different growth pressures, well-aligned hexagonal-shaped ZnO nanorod arrays were obtained under both conditions. X-ray diffraction (XRD) analysis confirmed the nanorods are c-axis orientated. Selected area electron diffraction (SAED) and transmission electron microscopy (TEM) analysis demonstrated the individual nanorod is single crystal. Photoluminescence (PL) analyses show the superior optical properties of the nanorod arrays.

  8. ZnO nanorod arrays grown under different pressures and their photoluminescence properties

    International Nuclear Information System (INIS)

    Meng Xiuqing; Zhao Dongxu; Shen Dezhen; Zhang Jiying; Li Binghui; Wang Xiaohua; Fan Xiwu

    2007-01-01

    The ZnO nanorod arrays were synthesized via a simple vapor deposition method on Si (1 1 1) substrates at a low growth temperature of 520 deg. C. By selecting different source materials under different growth pressures, well-aligned hexagonal-shaped ZnO nanorod arrays were obtained under both conditions. X-ray diffraction (XRD) analysis confirmed the nanorods are c-axis orientated. Selected area electron diffraction (SAED) and transmission electron microscopy (TEM) analysis demonstrated the individual nanorod is single crystal. Photoluminescence (PL) analyses show the superior optical properties of the nanorod arrays

  9. Characterization of GaN/AlGaN epitaxial layers grown

    Indian Academy of Sciences (India)

    GaN and AlGaN epitaxial layers are grown by a metalorganic chemical vapour deposition (MOCVD) system. The crystalline quality of these epitaxially grown layers is studied by different characterization techniques. PL measurements indicate band edge emission peak at 363.8 nm and 312 nm for GaN and AlGaN layers ...

  10. Physical and chemical contributions of a plasma treatment in the growth of ZnO nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Jang, J.T. [Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Obang-dong, Gimhae, Gyeongnam 621-749 (Korea, Republic of); Ryu, H., E-mail: hhryu@inje.ac.kr [Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Obang-dong, Gimhae, Gyeongnam 621-749 (Korea, Republic of); Lee, W.J. [Department of Materials and Components Engineering, Dong-Eui University, 995 Eomgwangno, Busanjin-gu, Busan 614-714 (Korea, Republic of); Yun, J. [Department of Nano Science and Engineering, Kyungnam University, Changwon, Gyeongnam 631-701 (Korea, Republic of)

    2013-11-15

    Highlights: •ZnO nanorods were grown by hydrothermal synthesis. •Oxygen plasma was done on the surface of seed ZnO nanorods. •The ZnO nanorods with and without plasma treatment were characterized. •The results showed that the optical and structural properties of ZnO nanorods with plasma treatment were enhanced. -- Abstract: We analyzed the enhancement of optical and structural properties of ZnO nanorods by using a plasma treatment. In this study, seed ZnO nanorods were grown by hydrothermal synthesis for 1 h on a ZnO buffered Si substrate. The seed ZnO nanorods were then treated with an oxygen plasma. Next, ZnO was grown for an additional 4 h by hydrothermal synthesis. The resultant ZnO nanorods were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), electron energy loss spectroscopy (EELS), X-ray diffraction (XRD) and photoluminescence (PL). The measurements showed that the plasma treatment of the seed ZnO nanorods increased the roughness of the buffer layer and the concentration of oxygen ions on the surfaces of the seed ZnO nanorods and the buffer layer, leading to improved optical and structural properties. In this study, we found that the plasma treatment on the seed ZnO nanorods enhanced the optical and structural properties of the ZnO nanorods.

  11. Oxygen reduction at electrodeposited ZnO layers in alkaline solution

    International Nuclear Information System (INIS)

    Prestat, M.; Vucko, F.; Lescop, B.; Rioual, S.; Peltier, F.; Thierry, D.

    2016-01-01

    Zinc oxide (ZnO) layers were electrodeposited from an aqueous nitrate bath at 62 °C on copper substrates. At −0.9 V (vs. saturated calomel reference electrode), the growth rate is 600 nm min −1 . In the early stages of the deposition, the layers are porous. At longer deposition times, the surface becomes dense and rough. The wurtzite crystalline structure is confirmed by XRD measurements and the chemical composition of the ZnO surface was assessed by EDX and XPS. The oxygen reduction reaction (ORR) was investigated at room temperature in a 10 −3 M KOH solution with KCl as supporting electrolyte. The ORR onset potential is found to be much larger than that of platinum taken as reference electrocatalyst. Rotating ring-disk electrode experiments evidence a negligible production of hydrogen peroxide as intermediate product of the reaction. The latter follows thus a direct four-electron pathway at pH ∼11.

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

    Directory of Open Access Journals (Sweden)

    Tzu-Yi Yu

    2017-06-01

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

  13. Photoluminescence studies of ZnO thin films on R-plane sapphire substrates grown by sol-gel method

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min Su [Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Gimhae, Gyungnam 621-749 (Korea, Republic of); Nam, Giwoong; Kim, Soaram [Department of Nano Engineering, Inje University, Gimhae, Gyungnam 621-749 (Korea, Republic of); Kim, Do Yeob [Holcombe Department of Electrical and Computer Engineering, Center for Optical Materials Science and Engineering Technologies, Clemson University, Clemson, SC 29634 (United States); Lee, Dong-Yul [LED R and D team, Samsung Electronics Co. Ltd., Yongin 446-711 (Korea, Republic of); Kim, Jin Soo [Research Center of Advanced Materials Development (RCAMD), Division of Advanced Materials Engineering, Chonbuk National University, Jeonju, Chonbuk 561-756 (Korea, Republic of); Kim, Sung-O [Holcombe Department of Electrical and Computer Engineering, Center for Optical Materials Science and Engineering Technologies, Clemson University, Clemson, SC 29634 (United States); Kim, Jong Su [Department of Physics, Yeungnam University, Gyeongsan, Gyeongsangbuk-do 712-749 (Korea, Republic of); Son, Jeong-Sik [Department of Visual Optics, Kyungwoon University, Gumi, Gyeongsangbuk-do 730-850 (Korea, Republic of); Leem, Jae-Young, E-mail: jyleem@inje.ac.kr [Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Gimhae, Gyungnam 621-749 (Korea, Republic of)

    2012-10-15

    Zinc oxide (ZnO) thin films on R-plane sapphire substrates were grown by the sol-gel spin-coating method. The optical properties of the ZnO thin films were investigated using photoluminescence. In the UV range, the asymmetric near-band-edge emission was observed at 300 K, which consisted of two emissions at 3.338 and 3.279 eV. Eight peaks at 3.418, 3.402, 3.360, 3.288, 3.216, 3.145, 3.074, and 3.004 eV, which respectively correspond to the free exciton (FX), bound exciton, transverse optical (TO) phonon replica of FX recombination, and first-order longitudinal optical phonon replica of FX and the TO (1LO+TO), 2LO+TO, 3LO+TO, 4LO+TO, and 5LO+TO, were obtained at 12 K. From the temperature-dependent PL, it was found that the emission peaks at 3.338 and 3.279 eV corresponded to the FX and TO, respectively. The activation energy of the FX and TO emission peaks was found to be about 39.3 and 28.9 meV, respectively. The values of the fitting parameters of Varshni's empirical equation were {alpha}=4 Multiplication-Sign 10{sup -3} eV/K and {beta}=4.9 Multiplication-Sign 10{sup 3} K, and the S factor of the ZnO thin films was 0.658. With increasing temperature, the exciton radiative lifetime of the FX and TO emissions increased. The temperature-dependent variation of the exciton radiative lifetime for the TO emission was slightly higher than that for the FX emission. - Highlights: Black-Right-Pointing-Pointer ZnO thin films on R-plane sapphire substrates were grown by sol-gel method. Black-Right-Pointing-Pointer Two emission peaks at 3.338 and 3.279 eV were observed at 300 K Black-Right-Pointing-Pointer Activation energies of the two peaks were 39.3 and 28.9 meV,respectively. Black-Right-Pointing-Pointer Exciton radiative lifetime of the two peaks increased with increasing temperature.

  14. Structural, optical, and hydrogenation properties of ZnO nanowall networks grown on a Si (1 1 1) substrate by plasma-assisted molecular beam epitaxy

    International Nuclear Information System (INIS)

    Su, S.C.; Lu, Y.M.; Zhang, Z.Z.; Li, B.H.; Shen, D.Z.; Yao, B.; Zhang, J.Y.; Zhao, D.X.; Fan, X.W.

    2008-01-01

    ZnO nanowall networks were grown on a Si (1 1 1) substrate by plasma-assisted molecular beam epitaxy (P-MBE) without using catalysts. Scanning electronic microscopy (FE-SEM) confirmed the formation of nanowalls with a thickness of about 10-20 nm. X-ray diffraction (XRD) showed that the ZnO nanowall networks were crystallized in a wurtzite structure with their height parallel to the direction. Photoluminescence (PL) of the ZnO nanowall networks exhibited free excitons (FEs), donor-bound exciton (D 0 X), donor-acceptor pair (DAP), and free exciton to acceptor (FA) emissions. The growth mechanism of the ZnO nanowall networks was discussed, and their hydrogenation was also studied

  15. Effect of different sol concentrations on the properties of nanocrystalline ZnO thin films grown on FTO substrates by sol-gel spin-coating

    International Nuclear Information System (INIS)

    Kim, Ikhyun; Kim, Younggyu; Nam, Giwoong; Kim, Dongwan; Park, Minju; Kim, Haeun; Lee, Wookbin; Leem, Jaeyoung; Kim, Jongsu; Kim, Jin Soo

    2014-01-01

    Nanocrystalline ZnO thin films grown on fluorine-doped tinoxide (FTO) substrates were fabricated using the spin-coating method. The structural and the optical properties of the ZnO thin films prepared using different sol concentrations were investigated by using field-emission scanning electron microscopy (FE-SEM), X-ray diffractometry (XRD), photoluminescence (PL) measurements, and ultraviolet-visible (UV-vis) spectrometry. The surface morphology of the ZnO thin films, as observed in the SEM images, exhibited a mountain-chain structure. XRD results indicated that the thin films were preferentially orientated along the direction of the c-axis and that the grain size of the ZnO thin films increased with increasing sol concentration. The PL spectra showed a strong ultraviolet emission peak at 3.22 eV and a broad orange emission peak at 2.0 eV. The intensities of deep-level emission (DLE) gradually increased with increasing sol concentration from 0.4 to 1.0 M. The transmittance spectra of the ZnO thin films showed that the ZnO thin films were transparent (∼85%) in the visible region and exhibited sharp absorption edges at 375 nm. Thus, The Urbach energy of ZnO thin films decreased with increasing sol concentration.

  16. 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.

  17. Antibacterial and barrier properties of oriented polymer films with ZnO thin films applied with atomic layer deposition at low temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Vähä-Nissi, Mika, E-mail: mika.vaha-nissi@vtt.fi [VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044, VTT (Finland); Pitkänen, Marja; Salo, Erkki; Kenttä, Eija [VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044, VTT (Finland); Tanskanen, Anne, E-mail: Anne.Tanskanen@aalto.fi [Aalto University, School of Chemical Technology, Department of Chemistry, Laboratory of Inorganic Chemistry, P.O. Box 16100, FI-00076 Aalto (Finland); Sajavaara, Timo, E-mail: timo.sajavaara@jyu.fi [University of Jyväskylä, Department of Physics, P.O. Box 35, FI-40014 Jyväskylä (Finland); Putkonen, Matti; Sievänen, Jenni; Sneck, Asko; Rättö, Marjaana [VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044, VTT (Finland); Karppinen, Maarit, E-mail: Maarit.Karppinen@aalto.fi [Aalto University, School of Chemical Technology, Department of Chemistry, Laboratory of Inorganic Chemistry, P.O. Box 16100, FI-00076 Aalto (Finland); Harlin, Ali [VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044, VTT (Finland)

    2014-07-01

    Concerns on food safety, and need for high quality and extended shelf-life of packaged foods have promoted the development of antibacterial barrier packaging materials. Few articles have been available dealing with the barrier or antimicrobial properties of zinc oxide thin films deposited at low temperature with atomic layer deposition (ALD) onto commercial polymer films typically used for packaging purposes. The purpose of this paper was to study the properties of ZnO thin films compared to those of aluminum oxide. It was also possible to deposit ZnO thin films onto oriented polylactic acid and polypropylene films at relatively low temperatures using ozone instead of water as an oxidizing precursor for diethylzinc. Replacing water with ozone changed both the structure and the chemical composition of films deposited on silicon wafers. ZnO films deposited with ozone contained large grains covered and separated probably by a more amorphous and uniform layer. These thin films were also assumed to contain zinc salts of carboxylic acids. The barrier properties of a 25 nm ZnO thin film deposited with ozone at 100 °C were quite close to those obtained earlier with ALD Al{sub 2}O{sub 3} of similar apparent thickness on similar polymer films. ZnO thin films deposited at low temperature indicated migration of antibacterial agent, while direct contact between ZnO and Al{sub 2}O{sub 3} thin films and bacteria promoted antibacterial activity. - Highlights: • Thin films were grown from diethylzinc also with ozone instead of water at 70 and 100 °C. • ZnO films deposited with diethylzinc and ozone had different structures and chemistries. • Best barrier properties obtained with zinc oxide films close to those obtained with Al{sub 2}O{sub 3} • Ozone as oxygen source provided better barrier properties at 100 °C than water. • Both aluminum and zinc oxide thin films showed antimicrobial activity against E. coli.

  18. Sb-related defects in Sb-doped ZnO thin film grown by pulsed laser deposition

    Science.gov (United States)

    Luo, Caiqin; Ho, Lok-Ping; Azad, Fahad; Anwand, Wolfgang; Butterling, Maik; Wagner, Andreas; Kuznetsov, Andrej; Zhu, Hai; Su, Shichen; Ling, Francis Chi-Chung

    2018-04-01

    Sb-doped ZnO films were fabricated on c-plane sapphire using the pulsed laser deposition method and characterized by Hall effect measurement, X-ray photoelectron spectroscopy, X-ray diffraction, photoluminescence, and positron annihilation spectroscopy. Systematic studies on the growth conditions with different Sb composition, oxygen pressure, and post-growth annealing were conducted. If the Sb doping concentration is lower than the threshold ˜8 × 1020 cm-3, the as-grown films grown with an appropriate oxygen pressure could be n˜4 × 1020 cm-3. The shallow donor was attributed to the SbZn related defect. Annealing these samples led to the formation of the SbZn-2VZn shallow acceptor which subsequently compensated for the free carrier. For samples with Sb concentration exceeding the threshold, the yielded as-grown samples were highly resistive. X-ray diffraction results showed that the Sb dopant occupied the O site rather than the Zn site as the Sb doping exceeded the threshold, whereas the SbO related deep acceptor was responsible for the high resistivity of the samples.

  19. Single crystalline ZnO nanorods grown by a simple hydrothermal process

    Energy Technology Data Exchange (ETDEWEB)

    Pei, L.Z., E-mail: lzpei1977@163.com [School of Materials Science and Engineering, Institute of Molecular Engineering and Applied Chemistry, Key Lab of Materials Science and Processing of Anhui Province, Anhui University of Technology, Ma' anshan, Anhui 243002 (China); Zhao, H.S. [School of Materials Science and Engineering, Institute of Molecular Engineering and Applied Chemistry, Key Lab of Materials Science and Processing of Anhui Province, Anhui University of Technology, Ma' anshan, Anhui 243002 (China); Tan, W. [Henkel Huawei Electronics Co. Ltd., Lian' yungang, Jiangsu 222006 (China); Yu, H.Y. [School of Materials Science and Engineering, Institute of Molecular Engineering and Applied Chemistry, Key Lab of Materials Science and Processing of Anhui Province, Anhui University of Technology, Ma' anshan, Anhui 243002 (China); Chen, Y.W. [Department of Materials Science, Fudan University, Shanghai 200433 (China); Zhang Qianfeng [School of Materials Science and Engineering, Institute of Molecular Engineering and Applied Chemistry, Key Lab of Materials Science and Processing of Anhui Province, Anhui University of Technology, Ma' anshan, Anhui 243002 (China)

    2009-09-15

    Single crystalline ZnO nanorods with wurtzite structure have been prepared by a simple hydrothermal process. The microstructure and composition of the products were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM, energy dispersive X-ray spectrum (EDS) and Raman spectrum. The nanorods have diameters ranging from 100 nm to 800 nm and length of longer than 10 {mu}m. Raman peak at 437.8 cm{sup -1} displays the characteristic peak of wurtzite ZnO. Photoluminescence (PL) spectrum shows a blue light emission at 441 nm, which is related to radiative recombination of photo-generated holes with singularly ionized oxygen vacancies.

  20. Single crystalline ZnO nanorods grown by a simple hydrothermal process

    International Nuclear Information System (INIS)

    Pei, L.Z.; Zhao, H.S.; Tan, W.; Yu, H.Y.; Chen, Y.W.; Zhang Qianfeng

    2009-01-01

    Single crystalline ZnO nanorods with wurtzite structure have been prepared by a simple hydrothermal process. The microstructure and composition of the products were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM, energy dispersive X-ray spectrum (EDS) and Raman spectrum. The nanorods have diameters ranging from 100 nm to 800 nm and length of longer than 10 μm. Raman peak at 437.8 cm -1 displays the characteristic peak of wurtzite ZnO. Photoluminescence (PL) spectrum shows a blue light emission at 441 nm, which is related to radiative recombination of photo-generated holes with singularly ionized oxygen vacancies.

  1. Layer-by-layer-assembled quantum dot multilayer sensitizers: how the number of layers affects the photovoltaic properties of one-dimensional ZnO nanowire electrodes.

    Science.gov (United States)

    Jin, Ho; Choi, Sukyung; Lim, Sang-Hoon; Rhee, Shi-Woo; Lee, Hyo Joong; Kim, Sungjee

    2014-01-13

    Layer cake: Multilayered CdSe quantum dot (QD) sensitizers are layer-by-layer assembled onto ZnO nanowires by making use of electrostatic interactions to study the effect of the layer number on the photovoltaic properties. The photovoltaic performance of QD-sensitized solar cells critically depends on this number as a result of the balance between light-harvesting efficiency and carrier-recombination probability. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Influence of aspect ratio and surface defect density on hydrothermally grown ZnO nanorods towards amperometric glucose biosensing applications

    Science.gov (United States)

    Shukla, Mayoorika; Pramila; Dixit, Tejendra; Prakash, Rajiv; Palani, I. A.; Singh, Vipul

    2017-11-01

    In this work, hydrothermally grown ZnO Nanorods Array (ZNA) has been synthesized over Platinum (Pt) coated glass substrate, for biosensing applications. In-situ addition of strong oxidizing agent viz KMnO4 during hydrothermal growth was found to have profound effect on the physical properties of ZNA. Glucose oxidase (GOx) was later immobilized over ZNA by means of physical adsorption process. Further influence of varying aspect ratio, enzyme loading and surface defects on amperometric glucose biosensor has been analyzed. Significant variation in biosensor performance was observed by varying the amount of KMnO4 addition during the growth. Moreover, investigations revealed that the suppression of surface defects and aspect ratio variation of the ZNA played key role towards the observed improvement in the biosensor performance, thereby significantly affecting the sensitivity and response time of the fabricated biosensor. Among different biosensors fabricated having varied aspect ratio and surface defect density of ZNA, the best electrode resulted into sensitivity and response time to be 18.7 mA cm-2 M-1 and <5 s respectively. The observed results revealed that apart from high aspect ratio nanostructures and the extent of enzyme loading, surface defect density also hold a key towards ZnO nanostructures based bio-sensing applications.

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

    International Nuclear Information System (INIS)

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

    2012-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-05-15

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

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

    CERN Document Server

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

    2003-01-01

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

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

    International Nuclear Information System (INIS)

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

    2003-01-01

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

  7. RETRACTED: Growth behavior and microstructure evolution of ZnO nanorods grown on Si in aqueous solution

    Science.gov (United States)

    Liou, Sz-Chian; Hsiao, Chi-Sheng; Chen, San-Yuan

    2005-02-01

    This article has been retracted: please see Elsevier Policy on Article Withdrawal. This article has been retracted at the request of the Editor-in-Chief. Two papers published in the Journal of Crystal Growth are being retracted due to a case of misrepresentation and reuse of data. A reader of the Journal has brought to our attention the reuse of data within two published papers: Growth behavior and microstructure evolution of ZnO nanorods grown on Si in aqueous solution, Sz-Chian Liou, Chi-Sheng Hsiao, San-Yuan Chen, Journal of Crystal Growth 274 (2005) 438-446. Nucleation and growth behavior of well-aligned ZnO nanorods on organic substrates in aqueous solutions, Chin-Ching Lin, San-Yuan Chen, and Syh-Yuh Cheng, Journal of Crystal Growth 283 (2005) 141-146. In these papers the same transmission electron micrograph was used to describe two different experimental situations and results bringing into question the content of these papers. The reuse of data without proper attribution is not acceptable within the scientific publishing community. In the present case, this is compounded by the attribution of the micrograph to a different experimental situation and drawing, as a result, new conclusions from data obtained from different samples. Such behavior undermines the integrity of the scientific publishing endeavor and is not acceptable. The authors are responsible for the content of their papers.

  8. Growth and Properties of Cl- Incorporated ZnO Nanofilms Grown by Ultrasonic Spray-Assisted Chemical Vapor Deposition.

    Science.gov (United States)

    Chen, Tingfang; Wang, Aiji; Kong, Lingrui; Li, Yongliang; Wang, Yinshu

    2016-04-01

    Pure and Cl- incorporated ZnO nanofilms were grown by the ultrasonic spray-assisted chemical vapor deposition (CVD) method. The properties of the nanofilms were investigated. The effects of growth temperature and Cl- concentration on the crystal structure, morphology, and optical properties of the nanofilms were studied. Temperature plays an important role in the growth mode and morphology of the pure nanofilms. Preferential growth along the c-axis occurs only at modulating temperature. Lower temperature suppresses the preferential growth, and higher temperature suppresses the growth of the nanofilms. The morphologies of the nanofilms change from lamellar and spherical structures into hexagonal platelets, then into separated nanoparticles with an increase in the temperature. Incorporating Cl- results in the lattice contracting gradually along with c-axis. Grains composing the nanofilms refine, and the optical gap broadens with increasing of Cl- concentration in growth precursor. Incorporating Cl- could reduce oxygen vacancies and passivate the non-irradiated centers, thus enhancing the UV emission and suppressing the visible emission of ZnO nanofilms.

  9. XAFS study on ZnO films grown by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Wu Zhihao; Zhou Yinxue; Zhang Xinyi; Fudan Univ., Shanghai; Yu Gencai; Wei Shiqiang; Chen Dongliang

    2004-01-01

    Effects of growth conditions including lattice mismatch and growth temperature on the local structures of ZnO films prepared by MBE have been investigated using fluorescence EXAFS at Zn K edge. The ZnO films were deposited on the Si substrate at 200 degree C and on sapphire substrate at 200 degree C or 300 degree C respectively. The coordination number N in the first shell (number of O atoms immediately surrounding a central Zn atom) remains constant 4 or so for all samples. However, the degree of disorder σ 2 (mean squared displacement) of the local structure is varied with the growth conditions. At the same growth temperature 200 degree C, the degree of disorder is reduced from 0.0080 (Angstrom) 2 to 0.0054 (Angstrom) 2 as the substrate is changed from Si to sapphire; on the same sapphire substrate, the degree of disorder decreases from 0.0054 (Angstrom) 2 to 0.0039 (Angstrom) 2 when the growth temperature is increased from 200 degree C to 300 degree C. Therefore, the higher growth temperature and smaller lattice mismatch can improve the disorder of local structures; the crystal quality of ZnO film will be improved as well . (authors)

  10. Effect of deposition conditions on the growth rate and electrical properties of ZnO thin films grown by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Roro, K.T.; Botha, J.R.; Leitch, A.W.R. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa)

    2008-07-01

    ZnO thin films have been grown on glass substrates by MOCVD. The effect of deposition conditions such as VI/II molar ratio, DEZn flow rate and total reactor pressure on the growth rate and electrical properties of the films was studied. It is found that the growth rate decreases with an increase in the VI/II molar ratio. This behaviour is ascribed to the competitive adsorption of reactant species on the growth surface. The growth rate increases with an increase in DEZn flow rate, as expected. It is shown that the carrier concentration is independent of the DEZn flow rate. An increase in the total reactor pressure yields a decrease in growth rate. This phenomenon is attributed to the depletion of the gas phase due to parasitic prereactions between zinc and oxygen species at high pressure. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. The defect passivation effect of hydrogen on the optical properties of solution-grown ZnO nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Urgessa, Z.N., E-mail: zelalem.urgessa@nmmu.ac.za [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Mbulanga, C.M.; Tankio Djiokap, S.R.; Botha, J.R. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Duvenhage, M.M.; Swart, H.C. [Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein ZA9300 (South Africa)

    2016-01-01

    In this study the effect of annealing environment on both low temperature and room temperature photoluminescence (PL) characteristics of ZnO nanorods, grown in solution, is presented. Particular attention is given to the effect of hydrogen defect passivation and its PL related line. It is shown that, irrespective of annealing ambient, an optimum annealing temperature of 300 °C suppresses the defect related emission and significantly improves the UV emission. By considering the stability of hydrogen impurities, the observed results in the PL spectra are analyzed. There is an observed asymmetric broadening on the low energy side of the bound exciton luminescence in the low temperature annealed samples which is explained by a high concentration of ionized impurities related to hydrogen. This has been attributed primarily to the conversion of hydrogen molecule to substitutional hydrogen on the oxygen site (H{sub O}) as a result of annealing.

  12. The defect passivation effect of hydrogen on the optical properties of solution-grown ZnO nanorods

    International Nuclear Information System (INIS)

    Urgessa, Z.N.; Mbulanga, C.M.; Tankio Djiokap, S.R.; Botha, J.R.; Duvenhage, M.M.; Swart, H.C.

    2016-01-01

    In this study the effect of annealing environment on both low temperature and room temperature photoluminescence (PL) characteristics of ZnO nanorods, grown in solution, is presented. Particular attention is given to the effect of hydrogen defect passivation and its PL related line. It is shown that, irrespective of annealing ambient, an optimum annealing temperature of 300 °C suppresses the defect related emission and significantly improves the UV emission. By considering the stability of hydrogen impurities, the observed results in the PL spectra are analyzed. There is an observed asymmetric broadening on the low energy side of the bound exciton luminescence in the low temperature annealed samples which is explained by a high concentration of ionized impurities related to hydrogen. This has been attributed primarily to the conversion of hydrogen molecule to substitutional hydrogen on the oxygen site (H_O) as a result of annealing.

  13. Solution-Grown ZnO Films toward Transparent and Smart Dual-Color Light-Emitting Diode.

    Science.gov (United States)

    Huang, Xiaohu; Zhang, Li; Wang, Shijie; Chi, Dongzhi; Chua, Soo Jin

    2016-06-22

    An individual light-emitting diode (LED) capable of emitting different colors of light under different bias conditions not only allows for compact device integration but also extends the functionality of the LED beyond traditional illumination and display. Herein, we report a color-switchable LED based on solution-grown n-type ZnO on p-GaN/n-GaN heterojunction. The LED emits red light with a peak centered at ∼692 nm and a full width at half-maximum of ∼90 nm under forward bias, while it emits green light under reverse bias. These two lighting colors can be switched repeatedly by reversing the bias polarity. The bias-polarity-switched dual-color LED enables independent control over the lighting color and brightness of each emission with two-terminal operation. The results offer a promising strategy toward transparent, miniaturized, and smart LEDs, which hold great potential in optoelectronics and optical communication.

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

    International Nuclear Information System (INIS)

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

    2009-01-01

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

  15. Comparison of linear and nonlinear optical spectra of various ZnO epitaxial layers and of bulk material obtained by different experimental techniques

    Energy Technology Data Exchange (ETDEWEB)

    Priller, H.; Brueckner, J.; Klingshirn, C.; Kalt, H. [Institut fuer Angewandte Physik, Universitaet Karlsruhe, Wolfgang-Gaede-Str. 1, 76131 Karlsruhe (Germany); Gruber, Th.; Waag, A. [Abteilung Halbleiterphysik, Universitaet Ulm, Albert Einstein Allee 45, 89081 Ulm (Germany); Ko, H.J.; Yao, T. [Institute for Material Research, Tohoku University, Katahira 2-1-1, Aoba-Ku, Sendai 980-8577 (Japan)

    2004-03-01

    We investigate ZnO epitaxial layers grown by MBE (Molecular Beam Epitaxy) and MOVPE (Metal Organic Vapor Phase Epitaxy) techniques. The samples show similar optical behavior in temperature dependent photoluminescence measurements, reflection and photoluminescence excitation spectroscopy in the low density regime. High excitation measurements show different behavior. While the MBE sample leads to stimulated emission from the exciton-exciton-scattering, an electron hole plasma is formed in the MOVPE sample which leads to stimulated emission at higher excitation intensities. The gain value measured by the variable stripe length method is much higher for the MBE grown sample. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Electrical, photoelectrical and morphological properties of ZnO nanofiber networks grown on SiO{sub 2} and on Si nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Vega, Nadia Celeste; Comedi, David [Universidad Nacional de Tucuman (FACET/UNT), (Argentina). Facultad de Ciencias Exactas y Tecnologia. Dept. de Fisica. Lab. de Fisica del Solido; Audebert, Fernando [Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET) (Argentina); Tirado, Monica, E-mail: mtirado@herrera.unt.edu.ar [Universidad Nacional de Tucuman (FACET/UNT), (Argentina). Facultad de Ciencias Exactas y Tecnologia. Dept. de Fisica. Lab. de Nanomateriales y de Propiedades Dielectricas; Rodriguez, Andres; Rodriguez, Tomas [Universidad Politecnica de Madrid (ETSIT/UPM), Madrid (Spain). Escuela Tecnica Superior de Ingenieros de Telecomucacion. Tecnologia Electronica; Hughes, Gareth M.; Grovenor, Chris R.M. [University of Oxford, Parks Road, OX (United Kingdom). Dept. of Materials

    2013-11-01

    ZnO nanofibre networks (NFNs) were grown by vapour transport method on Si-based substrates. One type of substrate was SiO{sub 2} thermally grown on Si and another consisted of a Si wafer onto which Si nanowires (NWs) had been grown having Au nanoparticles catalysts. The ZnO-NFN morphology was observed by scanning electron microscopy on samples grown at 600 Degree-Sign C and 720 Degree-Sign C substrate temperature, while an focused ion beam was used to study the ZnO NFN/Si NWs/Si and ZnO NFN/SiO{sub 2} interfaces. Photoluminescence, electrical conductance and photo conductance of ZnO-NFN was studied for the sample grown on SiO{sub 2}. The photoluminescence spectra show strong peaks due to exciton recombination and lattice defects. The ZnO-NFN presents quasi-persistent photoconductivity effects and ohmic I-V characteristics which become nonlinear and hysteretic as the applied voltage is increased. The electrical conductance as a function of temperature can be described by a modified three dimensional variable hopping model with nanometer-ranged typical hopping distances. (author)

  17. Three-dimensional mesoscale heterostructures of ZnO nanowire arrays epitaxially grown on CuGaO2 nanoplates as individual diodes.

    Science.gov (United States)

    Forticaux, Audrey; Hacialioglu, Salih; DeGrave, John P; Dziedzic, Rafal; Jin, Song

    2013-09-24

    We report a three-dimensional (3D) mesoscale heterostructure composed of one-dimensional (1D) nanowire (NW) arrays epitaxially grown on two-dimensional (2D) nanoplates. Specifically, three facile syntheses are developed to assemble vertical ZnO NWs on CuGaO2 (CGO) nanoplates in mild aqueous solution conditions. The key to the successful 3D mesoscale integration is the preferential nucleation and heteroepitaxial growth of ZnO NWs on the CGO nanoplates. Using transmission electron microscopy, heteroepitaxy was found between the basal planes of CGO nanoplates and ZnO NWs, which are their respective (001) crystallographic planes, by the observation of a hexagonal Moiré fringes pattern resulting from the slight mismatch between the c planes of ZnO and CGO. Careful analysis shows that this pattern can be described by a hexagonal supercell with a lattice parameter of almost exactly 11 and 12 times the a lattice constants for ZnO and CGO, respectively. The electrical properties of the individual CGO-ZnO mesoscale heterostructures were measured using a current-sensing atomic force microscopy setup to confirm the rectifying p-n diode behavior expected from the band alignment of p-type CGO and n-type ZnO wide band gap semiconductors. These 3D mesoscale heterostructures represent a new motif in nanoassembly for the integration of nanomaterials into functional devices with potential applications in electronics, photonics, and energy.

  18. Enhanced magnetic properties of chemical solution deposited BiFeO3 thin film with ZnO buffer layer

    International Nuclear Information System (INIS)

    Rajalakshmi, R.; Kambhala, Nagaiah; Angappane, S.

    2012-01-01

    Highlights: ► Enhanced magnetization of BiFeO 3 is important for strong magnetoelectric coupling. ► BiFeO 3 film with ZnO buffer layer was successfully synthesized by chemical method. ► Magnetization of BiFeO 3 has increased by more than 10 times with ZnO buffer layer. ► A mechanism for enhancement in ferromagnetism of BiFeO 3 film is proposed. - Abstract: Magnetic properties of BiFeO 3 films deposited on Si substrates with and without ZnO buffer layer have been studied in this work. We adopted the chemical solution deposition method for the deposition of BiFeO 3 as well as ZnO films. The x-ray diffraction measurements on the deposited films confirm the formation of crystalline phase of BiFeO 3 and ZnO films, while our electron microscopy measurements help to understand the morphology of few micrometers thick films. It is found that the deposited ZnO film exhibit a hexagonal particulate surface morphology, whereas BiFeO 3 film fully covers the ZnO surface. Our magnetic measurements reveal that the magnetization of BiFeO 3 has increased by more than ten times in BiFeO 3 /ZnO/Si film compared to BiFeO 3 /Si film, indicating the major role played by ZnO buffer layer in enhancing the magnetic properties of BiFeO 3 , a technologically important multiferroic material.

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

    Czech Academy of Sciences Publication Activity Database

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

    2012-01-01

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

  20. ZnO nanostructures as electron extraction layers for hybrid perovskite thin films

    Science.gov (United States)

    Nikolaidou, Katerina; Sarang, Som; Tung, Vincent; Lu, Jennifer; Ghosh, Sayantani

    Optimum interaction between light harvesting media and electron transport layers is critical for the efficient operation of photovoltaic devices. In this work, ZnO layers of different morphologies are implemented as electron extraction and transport layers for hybrid perovskite CH3NH3PbI3 thin films. These include nanowires, nanoparticles, and single crystalline film. Charge transfer at the ZnO/perovskite interface is investigated and compared through ultra-fast characterization techniques, including temperature and power dependent spectroscopy, and time-resolved photoluminescence. The nanowires cause an enhancement in perovskite emission, which may be attributed to increased scattering and grain boundary formation. However, the ZnO layers with decreasing surface roughness exhibit better electron extraction, as inferred from photoluminescence quenching, reduction in the number of bound excitons, and reduced exciton lifetime in CH3NH3PbI3 samples. This systematic study is expected to provide an understanding of the fundamental processes occurring at the ZnO-CH3NH3PbI3 interface and ultimately, provide guidelines for the ideal configuration of ZnO-based hybrid Perovskite devices. This research was supported by National Aeronautics and Space administration (NASA) Grant No: NNX15AQ01A.

  1. Effects of Doping with Al, Ga, and In on Structural and Optical Properties of ZnO Nanorods Grown by Hydrothermal Method

    International Nuclear Information System (INIS)

    Kim, Soaram; Nam, Giwoong; Park, Hyunggil; Yoon, Hyunsik; Leem, Jaeyoung; Lee, Sangheon; Kim, Jong Su; Kim, Jin Soo; Kim, Do Yeob; Kim, Sungo

    2013-01-01

    The structural and optical properties of the ZnO, Al-doped ZnO, Ga-doped ZnO, and In-doped ZnO nanorods were investigated using field-emission scanning electron microscopy, X-ray diffraction, photoluminescence (PL) and ultraviolet-visible spectroscopy. All the nanorods grew with good alignment on the ZnO seed layers and the ZnO nanorod dimensions could be controlled by the addition of the various dopants. For instance, the diameter of the nanorods decreased with increasing atomic number of the dopants. The ratio between the near-band-edge emission (NBE) and the deep-level emission (DLE) intensities (I NBE /I DLE ) obtained by PL gradually decreased because the DLE intensity from the nanorods gradually increased with increase in the atomic number of the dopants. We found that the dopants affected the structural and optical properties of the ZnO nanorods including their dimensions, lattice constants, residual stresses, bond lengths, PL properties, transmittance values, optical band gaps, and Urbach energies

  2. Effects of Doping with Al, Ga, and In on Structural and Optical Properties of ZnO Nanorods Grown by Hydrothermal Method

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Soaram; Nam, Giwoong; Park, Hyunggil; Yoon, Hyunsik; Leem, Jaeyoung [Inje Univ., Gimhae (Korea, Republic of); Lee, Sangheon; Kim, Jong Su [Yeungnam Univ., Gyeongsan (Korea, Republic of); Kim, Jin Soo [Chonbuk National Univ., Jeonju (Korea, Republic of); Kim, Do Yeob; Kim, Sungo [Clemson Univ., Clemson (United States)

    2013-04-15

    The structural and optical properties of the ZnO, Al-doped ZnO, Ga-doped ZnO, and In-doped ZnO nanorods were investigated using field-emission scanning electron microscopy, X-ray diffraction, photoluminescence (PL) and ultraviolet-visible spectroscopy. All the nanorods grew with good alignment on the ZnO seed layers and the ZnO nanorod dimensions could be controlled by the addition of the various dopants. For instance, the diameter of the nanorods decreased with increasing atomic number of the dopants. The ratio between the near-band-edge emission (NBE) and the deep-level emission (DLE) intensities (I{sub NBE}/I{sub DLE}) obtained by PL gradually decreased because the DLE intensity from the nanorods gradually increased with increase in the atomic number of the dopants. We found that the dopants affected the structural and optical properties of the ZnO nanorods including their dimensions, lattice constants, residual stresses, bond lengths, PL properties, transmittance values, optical band gaps, and Urbach energies.

  3. Effects of Substrate and Post-Growth Treatments on the Microstructure and Properties of ZnO Thin Films Prepared by Atomic Layer Deposition

    Science.gov (United States)

    Haseman, Micah; Saadatkia, P.; Winarski, D. J.; Selim, F. A.; Leedy, K. D.; Tetlak, S.; Look, D. C.; Anwand, W.; Wagner, A.

    2016-12-01

    Aluminum-doped zinc oxide (ZnO:Al) thin films were synthesized by atomic layer deposition on silicon, quartz and sapphire substrates and characterized by x-ray diffraction (XRD), high-resolution scanning electron microscopy, optical spectroscopy, conductivity mapping, Hall effect measurements and positron annihilation spectroscopy. XRD showed that the as-grown films are of single-phase ZnO wurtzite structure and do not contain any secondary or impurity phases. The type of substrate was found to affect the orientation and degree of crystallinity of the films but had no effect on the defect structure or the transport properties of the films. High conductivity of 10-3 Ω cm, electron mobility of 20 cm2/Vs and carrier density of 1020 cm-3 were measured in most films. Thermal treatments in various atmospheres induced a large effect on the thickness, structure and electrical properties of the films. Annealing in a Zn and nitrogen environment at 400°C for 1 h led to a 16% increase in the thickness of the film; this indicates that Zn extracts oxygen atoms from the matrix and forms new layers of ZnO. On the other hand, annealing in a hydrogen atmosphere led to the emergence of an Al2O3 peak in the XRD pattern, which implies that hydrogen and Al atoms compete to occupy Zn sites in the ZnO lattice. Only ambient air annealing had an effect on film defect density and electrical properties, generating reductions in conductivity and electron mobility. Depth-resolved measurements of positron annihilation spectroscopy revealed short positron diffusion lengths and high concentrations of defects in all as-grown films. However, these defects did not diminish the electrical conductivity in the films.

  4. Enhanced resolution imaging of ultrathin ZnO layers on Ag(111) by multiple hydrogen molecules in a scanning tunneling microscope junction

    Science.gov (United States)

    Liu, Shuyi; Shiotari, Akitoshi; Baugh, Delroy; Wolf, Martin; Kumagai, Takashi

    2018-05-01

    Molecular hydrogen in a scanning tunneling microscope (STM) junction has been found to enhance the lateral spatial resolution of the STM imaging, referred to as scanning tunneling hydrogen microscopy (STHM). Here we report atomic resolution imaging of 2- and 3-monolayer (ML) thick ZnO layers epitaxially grown on Ag(111) using STHM. The enhanced resolution can be obtained at a relatively large tip to surface distance and resolves a more defective structure exhibiting dislocation defects for 3-ML-thick ZnO than for 2 ML. In order to elucidate the enhanced imaging mechanism, the electric and mechanical properties of the hydrogen molecular junction (HMJ) are investigated by a combination of STM and atomic force microscopy. It is found that the HMJ shows multiple kinklike features in the tip to surface distance dependence of the conductance and frequency shift curves, which are absent in a hydrogen-free junction. Based on a simple modeling, we propose that the junction contains several hydrogen molecules and sequential squeezing of the molecules out of the junction results in the kinklike features in the conductance and frequency shift curves. The model also qualitatively reproduces the enhanced resolution image of the ZnO films.

  5. Enhanced memory effect with embedded graphene nanoplatelets in ZnO charge trapping layer

    International Nuclear Information System (INIS)

    El-Atab, Nazek; Nayfeh, Ammar; Cimen, Furkan; Alkis, Sabri; Okyay, Ali K.

    2014-01-01

    A charge trapping memory with graphene nanoplatelets embedded in atomic layer deposited ZnO (GNIZ) is demonstrated. The memory shows a large threshold voltage V t shift (4 V) at low operating voltage (6/−6 V), good retention (>10 yr), and good endurance characteristic (>10 4 cycles). This memory performance is compared to control devices with graphene nanoplatelets (or ZnO) and a thicker tunnel oxide. These structures showed a reduced V t shift and retention characteristic. The GNIZ structure allows for scaling down the tunnel oxide thickness along with improving the memory window and retention of data. The larger V t shift indicates that the ZnO adds available trap states and enhances the emission and retention of charges. The charge emission mechanism in the memory structures with graphene nanoplatelets at an electric field E ≥ 5.57 MV/cm is found to be based on Fowler-Nordheim tunneling. The fabrication of this memory device is compatible with current semiconductor processing, therefore, has great potential in low-cost nano-memory applications.

  6. Enhanced Performance of Nanowire-Based All-TiO2 Solar Cells using Subnanometer-Thick Atomic Layer Deposited ZnO Embedded Layer

    International Nuclear Information System (INIS)

    Ghobadi, Amir; Yavuz, Halil I.; Ulusoy, T. Gamze; Icli, K. Cagatay; Ozenbas, Macit; Okyay, Ali K.

    2015-01-01

    In this paper, the effect of angstrom-thick atomic layer deposited (ALD) ZnO embedded layer on photovoltaic (PV) performance of Nanowire-Based All-TiO 2 solar cells has been systematically investigated. Our results indicate that by varying the thickness of ZnO layer the efficiency of the solar cell can be significantly changed. It is shown that the efficiency has its maximum for optimal thickness of 1 ALD cycle in which this ultrathin ZnO layer improves device performance through passivation of surface traps without hampering injection efficiency of photogenerated electrons. The mechanisms contributing to this unprecedented change in PV performance of the cell have been scrutinized and discussed

  7. ZnO nanorods for simultaneous light trapping and transparent electrode application in solar cells

    KAUST Repository

    Khan, Yasser

    2011-10-01

    Efficacy of using vertically grown ZnO nanorod array in enhancing electromagnetic field intensity and serving as the top contact layer (transparent electrodes) for solar cells was investigated. © 2011 IEEE.

  8. Influence of a ZnO Buffer Layer on the Structural, Optical, and Electrical Properties of ITO/ZnO Bi-Layered Films

    International Nuclear Information System (INIS)

    Heo, Sung-Bo; Moon, Hyun-Joo; Kim, Daeil; Kim, Jun-Ho

    2016-01-01

    Sn-doped indium oxide (ITO) films and ITO/ZnO bi-layered films were prepared on polycarbonate substrates by RF magnetron sputtering without intentional substrate heating. In order to consider the influence of the ZnO thickness on the structural, optical, and electrical properties of ITO/ZnO films, the thickness of the ZnO buffer layer was varied from 5 to 20 nm. As-deposited ITO films show an average optical transmittance of 79.2% in the visible range and an electrical resistivity of 3.0×10"-"4 Ωcm, while films with a 5-nm thick ZnO buffer layer film show an electrical resistivity of 2.6×10"-"4 Ωcm and films with a 20-nm thick ZnO buffer layer show an optical transmittance of 82.0%. Based on the figure of merit, it is concluded that the ZnO buffer layer enhances the optical and electrical performance of ITO films used as transparent conducting oxides in flexible display applications.

  9. Catalyst-free growth of ZnO nanowires on ITO seed/glass by thermal evaporation method: Effects of ITO seed layer thickness

    Energy Technology Data Exchange (ETDEWEB)

    Alsultany, Forat H., E-mail: foratusm@gmail.com; Ahmed, Naser M. [School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Hassan, Z. [Institute of Nano-Optoelectronics Research and Technology Laboratory (INOR), Universiti Sains Malaysia, 11800 USM, Penang (Malaysia)

    2016-07-19

    A seed/catalyst-free growth of ZnO nanowires (ZnO-NWs) on a glass substrate were successfully fabricated using thermal evaporation technique. These nanowires were grown on ITO seed layers of different thicknesses of 25 and 75 nm, which were deposited on glass substrates by radio frequency (RF) magnetron sputtering. Prior to synthesized ITO nanowires, the sputtered ITO seeds were annealed using the continuous wave (CW) CO2 laser at 450 °C in air for 15 min. The effect of seed layer thickness on the morphological, structural, and optical properties of ZnO-NWs were systematically investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and UV-Vis spectrophotometer.

  10. Photoluminescence study of ZnO structures grown by aqueous chemical growth

    International Nuclear Information System (INIS)

    Kenanakis, G.; Androulidaki, M.; Vernardou, D.; Katsarakis, N.; Koudoumas, E.

    2011-01-01

    ZnO micro-structures were deposited by aqueous chemical growth on Si (100) substrates, their morphology and size depending on the growth period. Characterization of the structures was performed using X-ray diffraction, scanning electron microscopy and Raman spectroscopy. Photoluminescence spectra recorded at 18 and 295 K for 325 nm CW excitation indicated that these are strongly affected by the morphology of the structures. Rods and tubes emit stronger UV radiation, in contrast to stronger yellow-green emission observed for flower-like structures. A red shift of the UV emission was found for increasing input power, while, thermal annealing of the samples induced stimulated emission for quite high excitation intensities.

  11. Effects of Chromium Dopant on Ultraviolet Photoresponsivity of ZnO Nanorods

    Science.gov (United States)

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

    2017-07-01

    Structural and optical properties of bare ZnO nanorods, ZnO-encapsulated ZnO nanorods, and Cr-doped ZnO-encapsulated ZnO nanorods have been investigated. Encapsulated ZnO nanorods were grown using a simple two-stage method in which ZnO nanorods were first grown on a glass substrate directly from a hydrothermal bath, then encapsulated with a thin layer of Cr-doped ZnO by dip coating. Comparative study of x-ray diffraction patterns showed that Cr was successfully incorporated into the shell layer of ZnO nanorods. Moreover, energy-dispersive x-ray spectroscopy confirmed presence of Cr in this sample. It was observed that the thickness of the shell layer around the core of the ZnO nanorods was at least about 20 nm. Transmission electron microscopy of bare ZnO nanorods revealed single-crystalline structure. Based on optical results, both the encapsulation process and addition of Cr dopant decreased the optical bandgap of the samples. Indeed, the optical bandgap values of Cr-doped ZnO-encapsulated ZnO nanorods, ZnO-encapsulated ZnO nanorods, and bare ZnO nanorods were 2.89 eV, 3.15 eV, and 3.34 eV, respectively. The ultraviolet (UV) parameters demonstrated that incorporation of Cr dopant into the shell layer of ZnO nanorods considerably facilitated formation and transportation of photogenerated carriers, optimizing their performance as a practical UV detector. As a result, the photocurrent of the Cr-doped ZnO-encapsulated ZnO nanorods was the highest (0.6 mA), compared with ZnO-encapsulated ZnO nanorods and bare ZnO nanorods (0.21 mA and 0.06 mA, respectively).

  12. UV light induced insulator-metal transition in ultra-thin ZnO/TiO{sub x} stacked layer grown by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Saha, D., E-mail: sahaphys@gmail.com, E-mail: pmisra@rrcat.gov.in; Misra, P., E-mail: sahaphys@gmail.com, E-mail: pmisra@rrcat.gov.in; Joshi, M. P.; Kukreja, L. M. [Laser Materials Processing Division, Raja Ramanna Centre for Advanced Technology, Indore 452 013 (India)

    2016-08-28

    In the present study, atomic layer deposition has been used to grow a series of Ti incorporated ZnO thin films by vertically stacking different numbers (n = 1–7) of ZnO/TiO{sub x} layers on (0001) sapphire substrates. The effects of defect states mediated chemisorption of O{sub 2} and/OH groups on the electrical properties of these films have been investigated by illuminating the samples under UV light inside a high vacuum optical cryostat. The ultra-thin film having one stacked layer (n = 1) did not show any change in its electrical resistance upon UV light exposure. On the contrary, marginal drop in the electrical resistivity was measured for the samples with n ≥ 3. Most surprisingly, the sample with n = 2 (thickness ∼ 12 nm) showed an insulator to metal transition upon UV light exposure. The temperature dependent electrical resistivity measurement on the as grown film (n = 2) showed insulating behaviour, i.e., diverging resistivity on extrapolation to T→ 0 K. However, upon UV light exposure, it transformed to a metallic state, i.e., finite resistivity at T → 0 K. Such an insulator-metal transition plausibly arises due to the de-trapping of conduction electrons from the surface defect sites which resulted in an upward shift of the Fermi level above the mobility edge. The low-temperature electron transport properties on the insulating film (n = 2) were investigated by a combined study of zero field electrical resistivity ρ(T) and magnetoresistance (MR) measurements. The observed negative MR was found to be in good agreement with the magnetic field induced suppression of quantum interference between forward-going paths of tunnelling electrons. Both ρ(T) and MR measurements provided strong evidence for the Efros-Shklovskii type variable range hopping conduction in the low-temperature (≤40 K) regime. Such studies on electron transport in ultra-thin n-type doped ZnO films are crucial to achieve optimum functionality

  13. Role of low O 2 pressure and growth temperature on electrical transport of PLD grown ZnO thin films on Si substrates

    Science.gov (United States)

    Pandis, Ch.; Brilis, N.; Tsamakis, D.; Ali, H. A.; Krishnamoorthy, S.; Iliadis, A. A.

    2006-06-01

    Undoped ZnO thin films have been grown on (100) Si substrates by pulsed laser deposition. The effect of growth parameters such as temperature, O 2 partial pressure and laser fluence on the structural and electrical properties of the films has been investigated. It is shown that the well-known native n-type conductivity, attributed to the activation of hydrogenic donor states, exhibits a conversion from n-type to p-type when the O 2 partial pressure is reduced from 10 -4 to 10 -7 Torr at growth temperatures lower than 400 °C. The p-type conductivity could be attributed to the dominant role of the acceptor Zn vacancies for ZnO films grown at very low O 2 pressures.

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

    International Nuclear Information System (INIS)

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

    2015-01-01

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

  15. Atmospheric spatial atomic layer deposition of in-doped ZnO

    NARCIS (Netherlands)

    Illiberi, A.; Scherpenborg, R.; Roozeboom, F.; Poodt, P.

    2014-01-01

    Indium-doped zinc oxide (ZnO:In) has been grown by spatial atomic layer deposition at atmospheric pressure (spatial-ALD). Trimethyl indium (TMIn), diethyl zinc (DEZ) and deionized water have been used as In, Zn and O precursor, respectively. The metal content of the films is controlled in the range

  16. Single layer porous gold films grown at different temperatures

    International Nuclear Information System (INIS)

    Zhang Renyun; Hummelgard, Magnus; Olin, Hakan

    2010-01-01

    Large area porous gold films can be used in several areas including electrochemical electrodes, as an essential component in sensors, or as a conducting material in electronics. Here, we report on evaporation induced crystal growth of large area porous gold films at 20, 40 and 60 deg. C. The gold films were grown on liquid surface at 20 deg. C, while the films were grown on the wall of beakers when temperature increased to 40 and 60 deg. C. The porous gold films consisted of a dense network of gold nanowires as characterized by TEM and SEM. TEM diffraction results indicated that higher temperature formed larger crystallites of gold wires. An in situ TEM imaging of the coalescence of gold nanoparticles mimicked the process of the growth of these porous films, and a plotting of the coalescence time and the neck radius showed a diffusion process. The densities of these gold films were also characterized by transmittance, and the results showed film grown at 20 deg. C had the highest density, while the film grown at 60 deg. C had the lowest consistent with SEM and TEM characterization. Electrical measurements of these gold films showed that the most conductive films were the ones grown at 40 deg. C. The conductivities of the gold films were related to the amount of contamination, density and the diameter of the gold nanowires in the films. In addition, a gold film/gold nanoparticle hybrid was made, which showed a 10% decrease in transmittance during hybridization, pointing to applications as chemical and biological sensors.

  17. Growing vertical ZnO nanorod arrays within graphite: efficient isolation of large size and high quality single-layer graphene.

    Science.gov (United States)

    Ding, Ling; E, Yifeng; Fan, Louzhen; Yang, Shihe

    2013-07-18

    We report a unique strategy for efficiently exfoliating large size and high quality single-layer graphene directly from graphite into DMF dispersions by growing ZnO nanorod arrays between the graphene layers in graphite.

  18. CdTe deposition by successive ionic layer adsorption and reaction (SILAR) technique onto ZnO nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Salazar, Raul; Delamoreanu, Alexandru; Saidi, Bilel; Ivanova, Valentina [CEA, LETI, MINATEC Campus, 17 Rue des Martyrs, 38054, Grenoble (France); Levy-Clement, Claude [CNRS, Institut de Chimie et des Materiaux de Paris-Est, 94320, Thiais (France)

    2014-09-15

    In this study is reported CdTe deposition by Successive Ionic Layer Adsorption and reaction (SILAR) at room temperature onto ZnO nanowires (NWs). The as-deposited CdTe layer exhibits poor crystalline quality and not well defined optical transition which is probably result of its amorphous nature. The implementation of an annealing step and chemical treatment by CdCl{sub 2} to the classical SILAR technique improved significantly the CdTe film quality. The XRD analysis showed that the as treated layers are crystallized in the cubic zinc blende structure. The full coverage of ZnO nanowires and thickness of the CdTe shell, composed of small crystallites, was confirmed by STEM and TEM analysis. The layer thickness could be controlled by the number of SILAR cycles. The sharper optical transitions for the annealed and CdCl{sub 2} treated heterostructures additionally proves the enhancement of the layer crystalline quality. For comparison CdTe was also deposited by close space sublimation (CSS) method onto ZnO nanowires. It is shown that the SILAR deposited CdTe exhibits equal crystalline and optical properties to that prepared by CSS. These results demonstrate that SILAR technique is more suitable for conformal thin film deposition on nanostructures. CdTe extremely thin film deposited by SILAR method onto ZnO nanowire. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. CdTe deposition by successive ionic layer adsorption and reaction (SILAR) technique onto ZnO nanowires

    International Nuclear Information System (INIS)

    Salazar, Raul; Delamoreanu, Alexandru; Saidi, Bilel; Ivanova, Valentina; Levy-Clement, Claude

    2014-01-01

    In this study is reported CdTe deposition by Successive Ionic Layer Adsorption and reaction (SILAR) at room temperature onto ZnO nanowires (NWs). The as-deposited CdTe layer exhibits poor crystalline quality and not well defined optical transition which is probably result of its amorphous nature. The implementation of an annealing step and chemical treatment by CdCl 2 to the classical SILAR technique improved significantly the CdTe film quality. The XRD analysis showed that the as treated layers are crystallized in the cubic zinc blende structure. The full coverage of ZnO nanowires and thickness of the CdTe shell, composed of small crystallites, was confirmed by STEM and TEM analysis. The layer thickness could be controlled by the number of SILAR cycles. The sharper optical transitions for the annealed and CdCl 2 treated heterostructures additionally proves the enhancement of the layer crystalline quality. For comparison CdTe was also deposited by close space sublimation (CSS) method onto ZnO nanowires. It is shown that the SILAR deposited CdTe exhibits equal crystalline and optical properties to that prepared by CSS. These results demonstrate that SILAR technique is more suitable for conformal thin film deposition on nanostructures. CdTe extremely thin film deposited by SILAR method onto ZnO nanowire. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

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

    Directory of Open Access Journals (Sweden)

    Daria Majchrowicz

    2016-03-01

    Full Text Available In this paper we investigated the response of a fiber-optic Fabry-Pérot sensing interferometer with thin ZnO layers deposited on the end faces of the optical fibers forming the cavity. Standard telecommunication single-mode optical fiber (SMF-28 segments were used with the thin ZnO layers deposited by Atomic Layer Deposition (ALD. Measurements were performed with the interferometer illuminated by two broadband sources operating at 1300 nm and 1550 nm. Reflected interference signal was acquired by an optical spectrum analyzer while the length of the air cavity was varied. Thickness of the ZnO layers used in the experiments was 50 nm, 100 nm, and 200 nm. Uncoated SMF-28 fiber was also used as a reference. Based on the results of measurements, the thickness of the ZnO layers and the length of the cavity were selected in order to achieve good visibility. Following, the interferometer was used to determine the refractive index of selected liquids.

  1. Stable Inverted Low-Bandgap Polymer Solar Cells with Aqueous Solution Processed Low-Temperature ZnO Buffer Layers

    Directory of Open Access Journals (Sweden)

    Chunfu Zhang

    2016-01-01

    Full Text Available Efficient inverted low-bandgap polymer solar cells with an aqueous solution processed low-temperature ZnO buffer layer have been investigated. The low-bandgap material PTB-7 is employed so that more solar light can be efficiently harvested, and the aqueous solution processed ZnO electron transport buffer layer is prepared at 150°C so that it can be compatible with the roll-to-roll process. Power conversion efficiency (PCE of the inverted device reaches 7.12%, which is near the control conventional device. More importantly, the inverted device shows a better stability, keeping more than 90% of its original PCE after being stored for 625 hours, while PCE of the conventional device is only 75% of what it was. In addition, it is found that the ZnO thin film annealed in N2 can obviously increase PCE of the inverted device further to 7.26%.

  2. Enhanced efficiency of organic solar cells by using ZnO as an electron-transport layer

    Science.gov (United States)

    Ullah, Irfan; Shah, Said Karim; Wali, Sartaj; Hayat, Khizar; Khattak, Shaukat Ali; Khan, Aurangzeb

    2017-12-01

    This paper reports the use of ZnO, processed by sol-gel, as an efficient electron-transport layer for inverted organic photovoltaic cells. The device with incorporated ZnO interlayer, annealed at 100 °C, between transparent electrode and blend film plays an effective role in enhancing photovoltaic properties: the short-circuit current density (J sc) doubles while open-circuit voltage (V oc) and fill factor increase by 0.12 V and 10 %, respectively. Power conversion efficiency (PCE) of solar cell increases, approximately, three times. The improvement in the PCE is attributed to the presence of ZnO which, being an electron-facilitating layer, provides an energy step for charge collection at electrodes.

  3. Structural, Optical Constants and Photoluminescence of ZnO Thin Films Grown by Sol-Gel Spin Coating

    Directory of Open Access Journals (Sweden)

    Abdel-Sattar Gadallah

    2013-01-01

    Full Text Available We report manufacturing and characterization of low cost ZnO thin films grown on glass substrates by sol-gel spin coating method. For structural properties, X-ray diffraction measurements have been utilized for evaluating the dominant orientation of the thin films. For optical properties, reflectance and transmittance spectrophotometric measurements have been done in the spectral range from 350 nm to 2000 nm. The transmittance of the prepared thin films is 92.4% and 88.4%. Determination of the optical constants such as refractive index, absorption coefficient, and dielectric constant in this wavelength range has been evaluated. Further, normal dispersion of the refractive index has been analyzed in terms of single oscillator model of free carrier absorption to estimate the dispersion and oscillation energy. The lattice dielectric constant and the ratio of free carrier concentration to free carrier effective mass have been determined. Moreover, photoluminescence measurements of the thin films in the spectral range from 350 nm to 900 nm have been presented. Electrical measurements for resistivity evaluation of the films have been done. An analysis in terms of order-disorder of the material has been presented to provide more consistency in the results.

  4. New method for the determination of the defect profile in thin layers grown over a substrate

    International Nuclear Information System (INIS)

    Zubiaga, A.; Garcia, J.A.; Plazaola, F.; Tuomisto, F.; Zuniga, J.; Munoz-Sanjose, V.

    2007-01-01

    We present a new method to obtain information about the defect profile of films grown over high quality substrates. The method is valid, at least, for films where the positron mean-diffusion length is small. We have used the method for the case of ZnO films grown over sapphire, but the method can be generalized very easily to other film/substrate systems. Applying the method to the ratio of W and S parameters obtained from Doppler broadening measurements, W/S plots, one can determine the thickness of the film and the defect profile trend in the film, when mainly one positron trap is contributing to positron trapping within the film. Indeed, the quality of such a characterization is very important for the potential technological applications of the film. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. New method for the determination of the defect profile in thin layers grown over a substrate

    Energy Technology Data Exchange (ETDEWEB)

    Zubiaga, A.; Garcia, J.A.; Plazaola, F. [Fisika Aplikatua II Saila, Euskal Herriko Unibertsitatea, Bilbao (Spain); Tuomisto, F. [Laboratory of Physics, Helsinki University of Technology, Espoo (Finland); Zuniga, J.; Munoz-Sanjose, V. [Departamento de Fisica Aplicada i Electromagnetisme, Burjassot (Valencia) (Spain)

    2007-07-01

    We present a new method to obtain information about the defect profile of films grown over high quality substrates. The method is valid, at least, for films where the positron mean-diffusion length is small. We have used the method for the case of ZnO films grown over sapphire, but the method can be generalized very easily to other film/substrate systems. Applying the method to the ratio of W and S parameters obtained from Doppler broadening measurements, W/S plots, one can determine the thickness of the film and the defect profile trend in the film, when mainly one positron trap is contributing to positron trapping within the film. Indeed, the quality of such a characterization is very important for the potential technological applications of the film. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Growth of compact arrays of optical quality single crystalline ZnO

    Indian Academy of Sciences (India)

    We report the synthesis and optical properties of compact and aligned ZnO nanorod arrays (dia, ∼ 50–200 nm) grown on a glass substrate with varying seed particle density. The suspension of ZnO nanoparticles (size, ∼ 15 nm) of various concentrations are used as seed layer for the growth of nanorod arrays via ...

  7. Fabrication of nanostructured ZnO film as a hole-conducting layer of organic photovoltaic cell

    Science.gov (United States)

    Kim, Hyomin; Kwon, Yiseul; Choe, Youngson

    2013-05-01

    We have investigated the effect of fibrous nanostructured ZnO film as a hole-conducting layer on the performance of polymer photovoltaic cells. By increasing the concentration of zinc acetate dihydrate, the changes of performance characteristics were evaluated. Fibrous nanostructured ZnO film was prepared by sol-gel process and annealed on a hot plate. As the concentration of zinc acetate dihydrate increased, ZnO fibrous nanostructure grew from 300 to 600 nm. The obtained ZnO nanostructured fibrous films have taken the shape of a maze-like structure and were characterized by UV-visible absorption, scanning electron microscopy, and X-ray diffraction techniques. The intensity of absorption bands in the ultraviolet region was increased with increasing precursor concentration. The X-ray diffraction studies show that the ZnO fibrous nanostructures became strongly (002)-oriented with increasing concentration of precursor. The bulk heterojunction photovoltaic cells were fabricated using poly(3-hexylthiophene-2,5-diyl) and indene-C60 bisadduct as active layer, and their electrical properties were investigated. The external quantum efficiency of the fabricated device increased with increasing precursor concentration.

  8. Epitaxially Grown Layered MFI–Bulk MFI Hybrid Zeolitic Materials

    KAUST Repository

    Kim, Wun-gwi; Zhang, Xueyi; Lee, Jong Suk; Tsapatsis, Michael; Nair, Sankar

    2012-01-01

    The synthesis of hybrid zeolitic materials with complex micropore-mesopore structures and morphologies is an expanding area of recent interest for a number of applications. Here we report a new type of hybrid zeolite material, composed of a layered

  9. Antibacterial Composite Layers on Ti: Role of ZnO Nanoparticles

    Directory of Open Access Journals (Sweden)

    Roguska A.

    2016-03-01

    Full Text Available Problem of Post-operative infections of implant materials caused by bacterial adhesion to their surfaces is very serious. Enhancement of antibacterial properties is potentially beneficial for biomaterials value. Therefore, the metallic and metallic oxide nanoparticles attract particular attention as antimicrobial factors. The aim of this work was to create nanotubular (NT oxide layers on Ti with the addition of ZnO nanoparticles, designed for antibacterial biomedical coatings. Antimicrobial activities of titanium, TiO2 NT and ZnO/TiO2 NT surfaces were evaluated against bacterial strain typical for orthopaedic infections: S. epidermidis. TiO2 NT alone killed the free bacterial cells significantly but promoted their adhesion to the surfaces. The presence of moderate amount of ZnO nanoparticles significantly reduced the S. epidermidis cells adhesion and viability of bacterial cells in contact with modified surfaces. However, higher amount of loaded nanoZnO showed the reduced antimicrobial properties than the medium amount, suggesting the overdose effect.

  10. Atomic Layer Deposition of Electron Selective SnOx and ZnO Films on Mixed Halide Perovskite: Compatibility and Performance.

    Science.gov (United States)

    Hultqvist, Adam; Aitola, Kerttu; Sveinbjörnsson, Kári; Saki, Zahra; Larsson, Fredrik; Törndahl, Tobias; Johansson, Erik; Boschloo, Gerrit; Edoff, Marika

    2017-09-06

    The compatibility of atomic layer deposition directly onto the mixed halide perovskite formamidinium lead iodide:methylammonium lead bromide (CH(NH 2 ) 2 , CH 3 NH 3 )Pb(I,Br) 3 (FAPbI 3 :MAPbBr 3 ) perovskite films is investigated by exposing the perovskite films to the full or partial atomic layer deposition processes for the electron selective layer candidates ZnO and SnO x . Exposing the samples to the heat, the vacuum, and even the counter reactant of H 2 O of the atomic layer deposition processes does not appear to alter the perovskite films in terms of crystallinity, but the choice of metal precursor is found to be critical. The Zn precursor Zn(C 2 H 5 ) 2 either by itself or in combination with H 2 O during the ZnO atomic layer deposition (ALD) process is found to enhance the decomposition of the bulk of the perovskite film into PbI 2 without even forming ZnO. In contrast, the Sn precursor Sn(N(CH 3 ) 2 ) 4 does not seem to degrade the bulk of the perovskite film, and conformal SnO x films can successfully be grown on top of it using atomic layer deposition. Using this SnO x film as the electron selective layer in inverted perovskite solar cells results in a lower power conversion efficiency of 3.4% than the 8.4% for the reference devices using phenyl-C 70 -butyric acid methyl ester. However, the devices with SnO x show strong hysteresis and can be pushed to an efficiency of 7.8% after biasing treatments. Still, these cells lacks both open circuit voltage and fill factor compared to the references, especially when thicker SnO x films are used. Upon further investigation, a possible cause of these losses could be that the perovskite/SnO x interface is not ideal and more specifically found to be rich in Sn, O, and halides, which is probably a result of the nucleation during the SnO x growth and which might introduce barriers or alter the band alignment for the transport of charge carriers.

  11. Photoluminescence of phosphorus atomic layer doped Ge grown on Si

    Science.gov (United States)

    Yamamoto, Yuji; Nien, Li-Wei; Capellini, Giovanni; Virgilio, Michele; Costina, Ioan; Schubert, Markus Andreas; Seifert, Winfried; Srinivasan, Ashwyn; Loo, Roger; Scappucci, Giordano; Sabbagh, Diego; Hesse, Anne; Murota, Junichi; Schroeder, Thomas; Tillack, Bernd

    2017-10-01

    Improvement of the photoluminescence (PL) of Phosphorus (P) doped Ge by P atomic layer doping (ALD) is investigated. Fifty P delta layers of 8 × 1013 cm-2 separated by 4 nm Ge spacer are selectively deposited at 300 °C on a 700 nm thick P-doped Ge buffer layer of 1.4 × 1019 cm-3 on SiO2 structured Si (100) substrate. A high P concentration region of 1.6 × 1020 cm-3 with abrupt P delta profiles is formed by the P-ALD process. Compared to the P-doped Ge buffer layer, a reduced PL intensity is observed, which might be caused by a higher density of point defects in the P delta doped Ge layer. The peak position is shifted by ˜0.1 eV towards lower energy, indicating an increased active carrier concentration in the P-delta doped Ge layer. By introducing annealing at 400 °C to 500 °C after each Ge spacer deposition, P desorption and diffusion is observed resulting in relatively uniform P profiles of ˜2 × 1019 cm-3. Increased PL intensity and red shift of the PL peak are observed due to improved crystallinity and higher active P concentration.

  12. Characterization of GaN/AlGaN epitaxial layers grown by ...

    Indian Academy of Sciences (India)

    GaN and AlGaN epitaxial layers are grown by a metalorganic chemical ... reported by introducing annealing of the GaN layer in nitrogen [5], Fe doping [6], .... [2] Y F Wu, S M Wood, R P Smith, S Sheppard, S T Allen, P Parikh and J Milligan,.

  13. Layered zinc hydroxide salts: Delamination, preferred orientation of hydroxide lamellae, and formation of ZnO nanodiscs

    Czech Academy of Sciences Publication Activity Database

    Demel, Jan; Pleštil, Josef; Bezdička, Petr; Janda, Pavel; Klementová, Mariana; Lang, Kamil

    2011-01-01

    Roč. 360, č. 2 (2011), s. 532-539 ISSN 0021-9797 R&D Projects: GA MŠk ME09058; GA ČR GAP207/10/1447 Institutional research plan: CEZ:AV0Z40320502; CEZ:AV0Z40500505; CEZ:AV0Z40400503 Keywords : layered zinc hydroxide * delamination * exfoliation * hydroxide layer * ZnO Subject RIV: CA - Inorganic Chemistry Impact factor: 3.070, year: 2011

  14. Quality improvement of ZnO thin layers overgrown on Si(100 substrates at room temperature by nitridation pretreatment

    Directory of Open Access Journals (Sweden)

    Peng Wang

    2012-06-01

    Full Text Available To improve the quality of ZnO thin film overgrown on Si(100 substrate at RT (room temperature, the Si(100 surface was pretreated with different methods. The influence of interface on the overgrown ZnO layers was investigated by atomic force microscopy, photoluminescence and X-ray diffraction. We found that the nitridation pretreatment could significantly improve the quality of RT ZnO thin film through two-fold effects: one was to buffer the big lattice mismatch and ease the stress resulted from heterojunction growth; the other was to balance the interface charge, block the symmetric inheritance from the cubic Si (100 substrate and thus restrain the formation of zincblende phase.

  15. Characterization of few-layered graphene grown by carbon implantation

    International Nuclear Information System (INIS)

    Lee, Kin Kiong; McCallum, Jeffrey C.; Jamieson, David N.

    2014-01-01

    Graphene is considered to be a very promising material for applications in nanotechnology. The properties of graphene are strongly dependent on defects that occur during growth and processing. These defects can be either detrimental or beneficial to device performance depending on defect type, location and device application. Here we present experimental results on formation of few-layered graphene by carbon ion implantation into nickel films and characteristics of graphene devices formed by graphene transfer and lithographic patterning. Micro-Raman spectroscopy was used to determine the number of graphene layers formed and identify defects arising from the device processing. The graphene films were cleaned by annealing in vacuum. Transport properties of cleaned graphene films were investigated by fabrication of back-gated field-effect transistors, which exhibited high hole and electron mobility of 1935 and 1905 cm2/Vs, respectively

  16. Characterization of few-layered graphene grown by carbon implantation

    Science.gov (United States)

    Lee, Kin Kiong; McCallum, Jeffrey C.; Jamieson, David N.

    2014-02-01

    Graphene is considered to be a very promising material for applications in nanotechnology. The properties of graphene are strongly dependent on defects that occur during growth and processing. These defects can be either detrimental or beneficial to device performance depending on defect type, location and device application. Here we present experimental results on formation of few-layered graphene by carbon ion implantation into nickel films and characteristics of graphene devices formed by graphene transfer and lithographic patterning. Micro-Raman spectroscopy was used to determine the number of graphene layers formed and identify defects arising from the device processing. The graphene films were cleaned by annealing in vacuum. Transport properties of cleaned graphene films were investigated by fabrication of back-gated field-effect transistors, which exhibited high hole and electron mobility of 1935 and 1905 cm2/Vs, respectively.

  17. Evaluation of Alternative Atomistic Models for the Incipient Growth of ZnO by Atomic Layer Deposition

    Energy Technology Data Exchange (ETDEWEB)

    Chu, Manh-Hung; Tian, Liang; Chaker, Ahmad; Skopin, Evgenii; Cantelli, Valentina; Ouled, Toufik; Boichot, Raphaël; Crisci, Alexandre; Lay, Sabine; Richard, Marie-Ingrid; Thomas, Olivier; Deschanvres, Jean-Luc; Renevier, Hubert; Fong, Dillon; Ciatto, Gianluca

    2017-03-20

    ZnO thin films are interesting for applications in several technological fields, including optoelectronics and renewable energies. Nanodevice applications require controlled synthesis of ZnO structures at nanometer scale, which can be achieved via atomic layer deposition (ALD). However, the mechanisms governing the initial stages of ALD had not been addressed until very recently. Investigations into the initial nucleation and growth as well as the atomic structure of the heterointerface are crucial to optimize the ALD process and understand the structure-property relationships for ZnO. We have used a complementary suite of in situ synchrotron x-ray techniques to investigate both the structural and chemical evolution during ZnO growth by ALD on two different substrates, i.e., SiO2 and Al2O3, which led us to formulate an atomistic model of the incipient growth of ZnO. The model relies on the formation of nanoscale islands of different size and aspect ratio and consequent disorder induced in the Zn neighbors' distribution. However, endorsement of our model requires testing and discussion of possible alternative models which could account for the experimental results. In this work, we review, test, and rule out several alternative models; the results confirm our view of the atomistic mechanisms at play, which influence the overall microstructure and resulting properties of the final thin film.

  18. Electrosynthesis and characterization of ZnO nanoparticles as inorganic component in organic thin-film transistor active layers

    International Nuclear Information System (INIS)

    Picca, Rosaria Anna; Sportelli, Maria Chiara; Hötger, Diana; Manoli, Kyriaki; Kranz, Christine; Mizaikoff, Boris; Torsi, Luisa; Cioffi, Nicola

    2015-01-01

    Highlights: • PSS-capped ZnO NPs were synthesized via a green electrochemical-thermal method • The influence of electrochemical conditions and temperature was studied • Spectroscopic data show that PSS functionalities are retained in the annealed NPs • Nanostructured ZnO improved the performance of P3HT-based thin film transistors - Abstract: ZnO nanoparticles have been prepared via a green electrochemical synthesis method in the presence of a polymeric anionic stabilizer (poly-sodium-4-styrenesulfonate, PSS), and then applied as inorganic component in poly-3-hexyl-thiophene thin-film transistor active layers. Different parameters (i.e. current density, electrolytic media, PSS concentration, and temperature) influencing nanoparticle synthesis have been studied. The resulting nanomaterials have been investigated by transmission electron microscopy (TEM) and spectroscopic techniques (UV-Vis, infrared, and x-ray photoelectron spectroscopies), assessing the most suitable conditions for the synthesis and thermal annealing of nanostructured ZnO. The proposed ZnO nanoparticles have been successfully coupled with a poly-3-hexyl-thiophene thin-film resulting in thin-film transistors with improved performance.

  19. Epitaxially grown polycrystalline silicon thin-film solar cells on solid-phase crystallised seed layers

    Energy Technology Data Exchange (ETDEWEB)

    Li, Wei, E-mail: weili.unsw@gmail.com; Varlamov, Sergey; Xue, Chaowei

    2014-09-30

    Highlights: • Crystallisation kinetic is used to analyse seed layer surface cleanliness. • Simplified RCA cleaning for the seed layer can shorten the epitaxy annealing duration. • RTA for the seed layer can improve the quality for both seed layer and epi-layer. • Epitaxial poly-Si solar cell performance is improved by RTA treated seed layer. - Abstract: This paper presents the fabrication of poly-Si thin film solar cells on glass substrates using seed layer approach. The solid-phase crystallised P-doped seed layer is not only used as the crystalline template for the epitaxial growth but also as the emitter for the solar cell structure. This paper investigates two important factors, surface cleaning and intragrain defects elimination for the seed layer, which can greatly influence the epitaxial grown solar cell performance. Shorter incubation and crystallisation time is observed using a simplified RCA cleaning than the other two wet chemical cleaning methods, indicating a cleaner seed layer surface is achieved. Cross sectional transmission microscope images confirm a crystallographic transferal of information from the simplified RCA cleaned seed layer into the epi-layer. RTA for the SPC seed layer can effectively eliminate the intragrain defects in the seed layer and improve structural quality of both of the seed layer and the epi-layer. Consequently, epitaxial grown poly-Si solar cell on the RTA treated seed layer shows better solar cell efficiency, V{sub oc} and J{sub sc} than the one on the seed layer without RTA treatment.

  20. Heterojunction oxide thin-film transistors with unprecedented electron mobility grown from solution

    KAUST Repository

    Faber, Hendrik; Das, Satyajit; Lin, Yen-Hung; Pliatsikas, Nikos; Zhao, Kui; Kehagias, Thomas; Dimitrakopulos, George; Amassian, Aram; Patsalas, Panos A.; Anthopoulos, Thomas D.

    2017-01-01

    with the extrinsic electron transport properties of the often defect-prone oxides. We overcome this limitation by replacing the single-layer semiconductor channel with a low-dimensional, solution-grown In2O3/ZnO heterojunction. We find that In2O3/ZnO transistors

  1. Optical and electro-catalytic properties of bundled ZnO nanowires grown on a ITO substrate

    International Nuclear Information System (INIS)

    Xia Cao; Wang Ning; Wang Long

    2010-01-01

    Bundled wurtzite zinc oxide (ZnO) nanowires were fabricated in a facile manner on an ITO-conducting substrate via a microemulsion route without using any hard template or external electric/magnetic field. Structure and properties of the as-prepared ZnO electrode were investigated using scanning electron microscopy, X-ray diffraction, photoluminescence, Raman spectroscopy, as well as electrochemical tests. The ZnO electrode shows excellent optical and electrocatalytic ability, which may find further applications such as optoelectronics or as sensors as well as other modern industrial areas.

  2. Biofunctionalization of carbon nanotubes/chitosan hybrids on Ti implants by atom layer deposited ZnO nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Yizhou; Liu, Xiangmei [Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Ministry-of-Education Key Laboratory for the Green Preparation and Application of Functional Materials, Hubei Key Laboratory of Polymer Materials, School of Materials Science & Engineering, Hubei University, Wuhan 430062 (China); Yeung, Kelvin W.K. [Division of Spine Surgery, Department of Orthopaedics & Traumatology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong (China); Chu, Paul K. [Department of Physics & Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China); Wu, Shuilin, E-mail: shuilin.wu@gmail.com [Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Ministry-of-Education Key Laboratory for the Green Preparation and Application of Functional Materials, Hubei Key Laboratory of Polymer Materials, School of Materials Science & Engineering, Hubei University, Wuhan 430062 (China)

    2017-04-01

    Highlights: • Carbon naonotubes/chitosan/ZnO coating was first constructed on Ti implants. • This system endowed Ti implants with excellent self-antibacterial activity. • The amount of Zn could be precisely controlled by atom layer deposition. • This system could regulate cell behaviors on metallic implants. - Abstract: One-dimensional (1D) nanostructures of ZnO using atomic layer deposition (ALD) on chitosan (CS) modified carbon nanotubes (CNTs) were first introduced onto the surfaces of biomedical implants. When the content of ZnO is not sufficient, CNTs can strengthen the antibacterial activity against E. coli and S. aureus by 8% and 39%, respectively. CS can improve the cytocompatibility of CNTs and ZnO. The amount of Zn content can be controlled by changing the cycling numbers of ALD processes. This hybrid coating can not only endow medical implants with high self-antibacterial efficacy against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) of over 73% and 98%, respectively, but also regulate the proliferation and osteogenic differentiation of osteoblasts by controlling the amount of ZnO.

  3. Biofunctionalization of carbon nanotubes/chitosan hybrids on Ti implants by atom layer deposited ZnO nanostructures

    International Nuclear Information System (INIS)

    Zhu, Yizhou; Liu, Xiangmei; Yeung, Kelvin W.K.; Chu, Paul K.; Wu, Shuilin

    2017-01-01

    Highlights: • Carbon naonotubes/chitosan/ZnO coating was first constructed on Ti implants. • This system endowed Ti implants with excellent self-antibacterial activity. • The amount of Zn could be precisely controlled by atom layer deposition. • This system could regulate cell behaviors on metallic implants. - Abstract: One-dimensional (1D) nanostructures of ZnO using atomic layer deposition (ALD) on chitosan (CS) modified carbon nanotubes (CNTs) were first introduced onto the surfaces of biomedical implants. When the content of ZnO is not sufficient, CNTs can strengthen the antibacterial activity against E. coli and S. aureus by 8% and 39%, respectively. CS can improve the cytocompatibility of CNTs and ZnO. The amount of Zn content can be controlled by changing the cycling numbers of ALD processes. This hybrid coating can not only endow medical implants with high self-antibacterial efficacy against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) of over 73% and 98%, respectively, but also regulate the proliferation and osteogenic differentiation of osteoblasts by controlling the amount of ZnO.

  4. Passivation of ZnO Nanowire Guests and 3D Inverse Opal Host Photoanodes for Dye-Sensitized Solar Cells

    KAUST Repository

    Labouchere, Philippe; Chandiran, Aravind Kumar; Moehl, Thomas; Harms, Hauke; Chavhan, Sudam; Tena-Zaera, Ramon; Nazeeruddin, Mohammad Khaja; Graetzel, Michael; Tetreault, Nicolas

    2014-01-01

    A hierarchical host-guest nanostructured photoanode is reported for dye-sensitized solar cells. It is composed of ZnO nanowires grown in situ into the macropores of a 3D ZnO inverse opal structure, which acts both as a seed layer and as a conductive

  5. Effects of ZnS layer on the performance improvement of the photosensitive ZnO nanowire arrays solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Javed, Hafiz Muhammad Asif [Electronic Materials Research Laboratory, International Center for Dielectric Research, Key Laboratory of the Ministry of Education, Xi' an Jiaotong University, Xi' an, 710049 (China); Que, Wenxiu, E-mail: wxque@mail.xjtu.edu.cn [Electronic Materials Research Laboratory, International Center for Dielectric Research, Key Laboratory of the Ministry of Education, Xi' an Jiaotong University, Xi' an, 710049 (China); Gao, Yanping; Xing, Yonglei [Electronic Materials Research Laboratory, International Center for Dielectric Research, Key Laboratory of the Ministry of Education, Xi' an Jiaotong University, Xi' an, 710049 (China); Kong, Ling Bing, E-mail: ELBKong@ntu.edu.sg [School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, 639798 (Singapore)

    2016-08-01

    The impact of ZnS layer as an interface modification on the photosensitive ZnO nanowire arrays solar cells was studied. CdS, CdSe and ZnS were deposited on ZnO nanowire arrays by SILAR method. When a ZnS layer was deposited, the quantum dot barrier was indirectly become in contact with the electrolyte, which thus restrained the flow of electrons. The CdS sensitized solar cells has an efficiency of 0.55% with the deposition of the ZnS(3) layer, that is, with a deposition of three times, whereas the CdS/CdSe co-sensitized solar cells has an efficiency of 2.03% with the deposition of the ZnS(1) layer. It was also noted that as the thickness of the of ZnS layer was increased, V{sub oc}, I{sub sc} and efficiencies of both the solar cells were first increased and then decreased. In addition, the CdS/N719 solar cells has an efficiency of 0.75% with the deposition of the ZnS(2) layer. - Highlights: • The impact of ZnS layer on the photosensitive ZnO nanowire solar cells was studied. • ZnS layer restrained the flow of electrons to the electrolyte. • CdS/CdSe co-sensitized solar cells have higher efficiency than CdS solar cells. • When ZnS layer was increased, V{sub oc} and I{sub sc} firstly increased and then decreased.

  6. Simple Preparation of ZnO Nano-layer by Sol-Gel Method as Active Electrode in P3HT/ZnO Heterojunction Solar Cell

    Science.gov (United States)

    Aprilia, Annisa; Herman, Hidayat, Rahmat

    2010-10-01

    Highly transparent undoped ZnO thin films have been prepared on glass and indium tin oxide substrates with simple process by sol-gel route and dip-coating deposition. Gel precursor of ZnO was prepared from zinc acetat dehydrate solution in methanol with the addition of trietylamine as stabilizing agent. Thin layer of gel precursor was prepared by dip coating and then followed by calcination at 400° C for 5 minute in air atmosphere. The thickness of the resulted ZnO thin film produced by ten times coating is about 150 nm. The films shows high transmittance larger than 98% in the visible region (400-800 nm). Absorption is observed in the UV region with absorption onset at about 390 nm indicating varying band gap between 3.18 eV until 3.23 eV depending on the number of coating layer. The AFM image shows that the films seems to be constructed from random stacking of nano-sized ZnO particle in the order of 50 nm. Among the prepared samples, the lowest resistivity is about 1.8×107 Ωm observed in the five-layer coating film. In order to fabricate solar cell structure, P3HT was deposited onto the ZnO thin film layer by spin casting technique and then followed by metal (Au) layer deposition by thermal evaporation. The formed solar cell has the inverted type solar cell with ITO/ZnO/P3HT/Au configuration. By the insertion ZnO layer, the photocurrent was improved by more than ten orders of magnitude in comparison to that of without ZnO layer. The measured photocurrent decreases at large number of coating layer which is supposed to be related with the current limitation by the effective carrier path length in ZnO layer.

  7. Characterization of n and p-type ZnO thin films grown by pulsed filtered cathodic vacuum arc system

    International Nuclear Information System (INIS)

    Kavak, H.; Erdogan, E.N.; Ozsahin, I.; Esen, R.

    2010-01-01

    Full text : Semiconductor ZnO thin films with wide band gap attract much interest due to their properties such as chemical stability in hydrogen plasma, high optical transparency in the visible and nearinfrared region. Due to these properties ZnO oxide is a promising materials for electronic or optoelectronic applications such as solar cell (as an antireflecting coating and a transparent conducting material), gas sensors, surface acoustic wave devices. The purpose of this research is to improve the properties of n and p-type ZnO thin films for device applications. Polycrystalline ZnO is naturally n-type and very difficult to dope to make p-type. Therefore nowadays hardly produced p-type ZnO attracts a lot of attention. Nitrogen considered as the best dopant for p-type ZnO thin films.The transparent, conductive and very precise thickness controlled n and p-type semiconducting nanocrystalline ZnO thin films were prepared by pulsed filtered cathodic vacuum arc deposition (PFCVAD) method. Structural, optical and electrical properties of these films were investigated. And also photoluminescence properties of these films were investigated. Transparent p-type ZnO thin films were produced by oxidation of PFCVAD deposited zinc nitride. Zinc nitride thin films were deposited with various thicknesses and under different oxygen pressures on glass substrates. Zinc nitride thin films, which were deposited at room temperatures, were amorphous and the optical transmission was below 70%. For oxidation zinc nitride, the sample was annealed in air starting from 350 degrees Celsium up to 550 degrees Celsium for one hour duration. These XRD patterns imply that zinc nitride thin films converted to zinc oxide thin films with the same hexagonal crystalline structures of ZnO. The optical measurements were made for each annealing temperature and the optical transmissions of ZnO thin films were found better than 90 percent in visible range after annealing over 350 degrees Celsium. By

  8. Tunable, flexible antireflection layer of ZnO nanowires embedded in PDMS.

    Science.gov (United States)

    Kim, Min Kyu; Yi, Dong Kee; Paik, Ungyu

    2010-05-18

    In this article, we report the fabrication of ordered hybrid structures composed of ZnO nanowires and a polymeric matrix with a polymer precursor infiltrating the nanowire arrays. The antireflective properties of the resulting ZnO nanowire-embedded polydimethylsiloxane composite (ZPC) were investigated at various ZnO nanowire lengths and ZPC bending angles. Interestingly, we found that whereas the antireflective properties showed a strong dependence on the length of the embedded ZnO nanowires in PDMS, the bending of ZPC has little effect on the antireflective properties.

  9. Enhancement of hole-injection and power efficiency of organic light emitting devices using an ultra-thin ZnO buffer layer

    International Nuclear Information System (INIS)

    Huang, H.-H.; Chu, S.-Y.; Kao, P.-C.; Chen, Y.-C.; Yang, M.-R.; Tseng, Z.-L.

    2009-01-01

    The advantages of using an anode buffer layer of ZnO on the electro-optical properties of organic light emitting devices (OLEDs) are reported. ZnO powders were thermal-evaporated and then treated with ultra-violet (UV) ozone exposure to make the ZnO layers. The turn-on voltage of OLEDs decreased from 4 V (4.2 cd/m 2 ) to 3 V (3.4 cd/m 2 ) and the power efficiency increased from 2.7 lm/W to 4.7 lm/W when a 1-nm-thick ZnO layer was inserted between indium tin oxide (ITO) anodes and α-naphthylphenylbiphenyl diamine (NPB) hole-transporting layers. X-ray and ultra-violet photoelectron spectroscopy (XPS and UPS) results revealed the formation of the ZnO layer and showed that the work function increased by 0.59 eV when the ZnO/ITO layer was treated by UV-ozone for 20 min. The surface of the ZnO/ITO film became smoother than that of bare ITO film after the UV-ozone treatment. Thus, the hole-injection energy barrier was lowered by inserting an ZnO buffer layer, resulting in a decrease of the turn-on voltage and an increase of the power efficiency of OLEDs.

  10. Improving the Performance of PbS Quantum Dot Solar Cells by Optimizing ZnO Window Layer

    Science.gov (United States)

    Yang, Xiaokun; Hu, Long; Deng, Hui; Qiao, Keke; Hu, Chao; Liu, Zhiyong; Yuan, Shengjie; Khan, Jahangeer; Li, Dengbing; Tang, Jiang; Song, Haisheng; Cheng, Chun

    2017-04-01

    Comparing with hot researches in absorber layer, window layer has attracted less attention in PbS quantum dot solar cells (QD SCs). Actually, the window layer plays a key role in exciton separation, charge drifting, and so on. Herein, ZnO window layer was systematically investigated for its roles in QD SCs performance. The physical mechanism of improved performance was also explored. It was found that the optimized ZnO films with appropriate thickness and doping concentration can balance the optical and electrical properties, and its energy band align well with the absorber layer for efficient charge extraction. Further characterizations demonstrated that the window layer optimization can help to reduce the surface defects, improve the heterojunction quality, as well as extend the depletion width. Compared with the control devices, the optimized devices have obtained an efficiency of 6.7% with an enhanced V oc of 18%, J sc of 21%, FF of 10%, and power conversion efficiency of 58%. The present work suggests a useful strategy to improve the device performance by optimizing the window layer besides the absorber layer.

  11. Ultra-high sensitive hydrazine chemical sensor based on low-temperature grown ZnO nanoparticles

    International Nuclear Information System (INIS)

    Mehta, S.K.; Singh, Kulvinder; Umar, Ahmad; Chaudhary, G.R.; Singh, Sukhjinder

    2012-01-01

    Graphical abstract: Systematic representation of the fabricated amperometric hydrazine chemical sensor based on ZnO NPs/Au modified electrode. Highlights: ► Synthesis of well-crystalline ZnO NPs has been achieved in aqueous solution. ► ZnO NPs act as efficient electron mediators for hydrazine sensor. ► Extremely high sensitivity and low-detection limit have been obtained. - Abstract: Using well-crystalline ZnO nanoparticles (NPs), an ultra high sensitive hydrazine amperometric sensor has been fabricated and reported in this paper. The ZnO NPs have been synthesized by very simple aqueous solution process at 90 °C and characterized in detail in terms of their morphological, compositional, structural and optical properties. The detailed investigations reveal that the synthesized products are well-crystalline NPs, possessing wurtzite hexagonal phase and exhibit good optical properties. The fabricated amperometric hydrazine sensor exhibits ultra-high sensitivity of ∼97.133 μA cm −2 μM −1 and very low-detection limit of 147.54 nM. To the best of our knowledge, this is the first report in which an ultra-high sensitivity and low-detection limit have been obtained for the hydrazine chemical sensor based on ZnO nanostructures.

  12. Optical characteristics of silicon nanowires grown from tin catalyst layers on silicon coated glass

    KAUST Repository

    Ball, Jeremy

    2012-08-20

    The optical characteristics of silicon nanowires grown on Si layers on glass have been modeled using the FDTD (Finite Difference Time Domain) technique and compared with experimental results. The wires were grown by the VLS (vapour-liquid-solid) method using Sn catalyst layers and exhibit a conical shape. The resulting measured and modeled absorption, reflectance and transmittance spectra have been investigated as a function of the thickness of the underlying Si layer and the initial catalyst layer, the latter having a strong influence on wire density. High levels of absorption (>90% in the visible wavelength range) and good agreement between the modeling and experiment have been observed when the nanowires have a relatively high density of ∼4 wires/μ m2. The experimental and modeled results diverge for samples with a lower density of wire growth. The results are discussed along with some implications for solar cell fabrication. © 2012 Optical Society of America.

  13. Optical characteristics of silicon nanowires grown from tin catalyst layers on silicon coated glass

    KAUST Repository

    Ball, Jeremy; Centeno, Anthony; Mendis, Budhika G.; Reehal, H. S.; Alford, Neil

    2012-01-01

    The optical characteristics of silicon nanowires grown on Si layers on glass have been modeled using the FDTD (Finite Difference Time Domain) technique and compared with experimental results. The wires were grown by the VLS (vapour-liquid-solid) method using Sn catalyst layers and exhibit a conical shape. The resulting measured and modeled absorption, reflectance and transmittance spectra have been investigated as a function of the thickness of the underlying Si layer and the initial catalyst layer, the latter having a strong influence on wire density. High levels of absorption (>90% in the visible wavelength range) and good agreement between the modeling and experiment have been observed when the nanowires have a relatively high density of ∼4 wires/μ m2. The experimental and modeled results diverge for samples with a lower density of wire growth. The results are discussed along with some implications for solar cell fabrication. © 2012 Optical Society of America.

  14. Effect of ALD surface treatment on structural and optical properties of ZnO nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Jin-Tak [Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Obang-dong, Gimhae, Gyeongnam 621-749 (Korea, Republic of); Ryu, Hyukhyun, E-mail: hhryu@inje.ac.kr [Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Obang-dong, Gimhae, Gyeongnam 621-749 (Korea, Republic of); Lee, Won-Jae [Department of Materials and Components Engineering, Dong-Eui University, 995 Eomgwangno, Busanjin-gu, Busan 614-714 (Korea, Republic of)

    2013-07-01

    In this study, we report on the improvement of the optical and structural properties of ZnO nanorods using atomic layer deposition (ALD) on seed ZnO nanorods. After the initial growth of ZnO seed nanorods by hydrothermal synthesis for 1 h, a ZnO layer with a thickness of 10 nm was deposited on the initial ZnO seed nanorods using ALD. Then ZnO was further grown by hydrothermal synthesis for 4 h. The samples were characterized using room temperature photoluminescence (PL), field emission-scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). From this experiment, it was found that the ZnO nanorods with the ALD surface treatment show improved optical and structural properties when compared with the ZnO nanorods grown only by hydrothermal synthesis. The ZnO nanorods with the ALD surface treatment show about 2.7 times higher XRD (0 0 2) peak intensity, about 2.64 times higher PL NBE peak intensity, and about 3.1 times better NBE/DLE ratio than the ZnO nanorods without an ALD surface treatment.

  15. Conformity and structure of titanium oxide films grown by atomic layer deposition on silicon substrates

    Energy Technology Data Exchange (ETDEWEB)

    Jogi, Indrek [University of Tartu, Institute of Experimental Physics and Technology, Taehe 4, 51010, Tartu (Estonia)], E-mail: indrek.jogi@ut.ee; Paers, Martti; Aarik, Jaan; Aidla, Aleks [University of Tartu, Institute of Physics, Riia 142, 51014, Tartu (Estonia); Laan, Matti [University of Tartu, Institute of Experimental Physics and Technology, Taehe 4, 51010, Tartu (Estonia); Sundqvist, Jonas; Oberbeck, Lars; Heitmann, Johannes [Qimonda Dresden GmbH and Co. OHG, Koenigsbruecker Strasse 180, 01099, Dresden (Germany); Kukli, Kaupo [University of Tartu, Institute of Experimental Physics and Technology, Taehe 4, 51010, Tartu (Estonia)

    2008-06-02

    Conformity and phase structure of atomic layer deposited TiO{sub 2} thin films grown on silicon substrates were studied. The films were grown using TiCl{sub 4} and Ti(OC{sub 2}H{sub 5}){sub 4} as titanium precursors in the temperature range from 125 to 500 {sup o}C. In all cases perfect conformal growth was achieved on patterned substrates with elliptical holes of 7.5 {mu}m depth and aspect ratio of about 1:40. Conformal growth was achieved with process parameters similar to those optimized for the growth on planar wafers. The dominant crystalline phase in the as-grown films was anatase, with some contribution from rutile at relatively higher temperatures. Annealing in the oxygen ambient resulted in (re)crystallization whereas the effect of annealing depended markedly on the precursors used in the deposition process. Compared to films grown from TiCl{sub 4}, the films grown from Ti(OC{sub 2}H{sub 5}){sub 4} were transformed into rutile in somewhat greater extent, whereas in terms of step coverage the films grown from Ti(OC{sub 2}H{sub 5}){sub 4} remained somewhat inferior compared to the films grown from TiCl{sub 4}.

  16. A layer-by-layer ZnO nanoparticle-PbS quantum dot self-assembly platform for ultrafast interfacial electron injection

    KAUST Repository

    Eita, Mohamed Samir

    2014-08-28

    Absorbent layers of semiconductor quantum dots (QDs) are now used as material platforms for low-cost, high-performance solar cells. The semiconductor metal oxide nanoparticles as an acceptor layer have become an integral part of the next generation solar cell. To achieve sufficient electron transfer and subsequently high conversion efficiency in these solar cells, however, energy-level alignment and interfacial contact between the donor and the acceptor units are needed. Here, the layer-by-layer (LbL) technique is used to assemble ZnO nanoparticles (NPs), providing adequate PbS QD uptake to achieve greater interfacial contact compared with traditional sputtering methods. Electron injection at the PbS QD and ZnO NP interface is investigated using broadband transient absorption spectroscopy with 120 femtosecond temporal resolution. The results indicate that electron injection from photoexcited PbS QDs to ZnO NPs occurs on a time scale of a few hundred femtoseconds. This observation is supported by the interfacial electronic-energy alignment between the donor and acceptor moieties. Finally, due to the combination of large interfacial contact and ultrafast electron injection, this proposed platform of assembled thin films holds promise for a variety of solar cell architectures and other settings that principally rely on interfacial contact, such as photocatalysis. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Low temperature synthesis and field emission characteristics of single to few layered graphene grown using PECVD

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Avshish; Khan, Sunny; Zulfequar, M.; Harsh; Husain, Mushahid, E-mail: mush_reslab@rediffmail.com

    2017-04-30

    Highlights: • Graphene was synthesized by PECVD system at a low temperature of 600 °C. • From different characterization techniques, the presence of single and few layered graphene was confirmed. • X-ray diffraction pattern of the graphene showed single crystalline nature of the film. • The as-grown graphene films were observed extremely good field emitters with long term emission current stability. - Abstract: In this work, high-quality graphene has successfully been synthesized on copper (Cu) coated Silicon (Si) substrate at very large-area by plasma enhanced chemical vapor deposition system. This method is low cost and highly effective for synthesizing graphene relatively at low temperature of 600 °C. Electron microscopy images have shown that surface morphology of the grown samples is quite uniform consisting of single layered graphene (SLG) to few layered graphene (FLG). Raman spectra reveal that graphene has been grown with high-quality having negligible defects and the observation of G and G' peaks is also an indicative of stokes phonon energy shift caused due to laser excitation. Scanning probe microscopy image also depicts the synthesis of single to few layered graphene. The field emission characteristics of as-grown graphene samples were studied in a planar diode configuration at room temperature. The graphene samples were observed to be a good field emitter having low turn-on field, higher field amplification factor and long term emission current stability.

  18. 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.

  19. Hexagonal ZnO porous plates prepared from microwave synthesized layered zinc hydroxide sulphate via thermal decomposition

    Energy Technology Data Exchange (ETDEWEB)

    Machovsky, Michal, E-mail: machovsky@ft.utb.cz [Centre of Polymer Systems, University Institute, Tomas Bata University in Zlin, Nad Ovcirnou 3685, 760 01 Zlin (Czech Republic); Polymer Centre, Faculty of Technology, Tomas Bata University in Zlin, Nam. T.G. Masaryka 275, 762 72 Zlin (Czech Republic); Kuritka, Ivo, E-mail: ivo@kuritka.net [Centre of Polymer Systems, University Institute, Tomas Bata University in Zlin, Nad Ovcirnou 3685, 760 01 Zlin (Czech Republic); Polymer Centre, Faculty of Technology, Tomas Bata University in Zlin, Nam. T.G. Masaryka 275, 762 72 Zlin (Czech Republic); Sedlak, Jakub, E-mail: j1sedlak@ft.utb.cz [Centre of Polymer Systems, University Institute, Tomas Bata University in Zlin, Nad Ovcirnou 3685, 760 01 Zlin (Czech Republic); Polymer Centre, Faculty of Technology, Tomas Bata University in Zlin, Nam. T.G. Masaryka 275, 762 72 Zlin (Czech Republic); Pastorek, Miroslav, E-mail: pastorek@ft.utb.cz [Centre of Polymer Systems, University Institute, Tomas Bata University in Zlin, Nad Ovcirnou 3685, 760 01 Zlin (Czech Republic); Department of Polymer Engineering, Faculty of Technology, Tomas Bata University in Zlin, Nam. T.G. Masaryka 275, 762 72 Zlin (Czech Republic)

    2013-10-15

    Graphical abstract: - Highlights: • Zinc hydroxy sulphate was synthesized in 3 min via microwave hydrothermal route. • Zinc hydroxy sulphate was converted into mesh like porous ZnO by calcining at 900°. • The process of transformation is topotactic. - Abstract: Layered zinc hydroxide sulphate (ZHS) was prepared by microwave-assisted hydrothermal precipitation of zinc sulphate monohydrate with hexamethylenetetramine. Under ambient conditions, the structure of ZHS determined by X-ray diffraction (XRD) was found to be a mixture of zinc hydroxide sulphate pentahydrate Zn{sub 4}SO{sub 4}(OH){sub 6}·5H{sub 2}O and tetrahydrate Zn{sub 4}SO{sub 4}(OH){sub 6}·4H{sub 2}O. Fourier transform infrared (FTIR) spectroscopy was used for characterization of the prepared materials. Based on the interpretation of ZHS's thermal decomposition profile obtained by thermogravimetric analysis, ZnO of high purity was prepared by calcination at 900 °C for 2 h. The structure of the resulting ZnO was confirmed by the XRD. The morphology examination by scanning electron microscopy revealed a porous mesh-like ZnO structure developed from the ZHS precursor at the expense of mass removal due to the release of water and sulphate during the calcination.

  20. Improvement of inverted organic solar cells using acetic acid as an additive for ZnO layer processing

    Directory of Open Access Journals (Sweden)

    Yang Li

    2018-02-01

    Full Text Available In this work, we used acetic acid as an additive for the preparation of ZnO layers and improved the performance of poly{4,8-bis[(2-ethylhexyl-oxy]benzo[1,2-b:4,5-b’] dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethylhexylcarbonyl]thieno[3,4-b]thiophene- 4,6-diyl} (PTB7-based inverted organic solar cells. The addition of acetic acid to the ZnO precursor solution improved the transparency and conductivity of the sol-gel-synthesized ZnO film, by increasing the grain size of the film. Accordingly, the power conversion efficiency (PCE of the organic solar cells was improved from 6.42% to 7.55%, which was mainly caused by the enhanced current density and fill factor. The best sample demonstrated a high PCE of 7.85% with negligible hysteresis and good stability. Our results indicate that using acetic acid as an additive for the preparation of ZnO is a simple and effective way of fabricating high-performance inverted organic solar cells.

  1. Improvement of inverted organic solar cells using acetic acid as an additive for ZnO layer processing

    Science.gov (United States)

    Li, Yang; Liu, Yawen; Liu, Zhihai; Xie, Xiaoyin; Lee, Eun-Cheol

    2018-02-01

    In this work, we used acetic acid as an additive for the preparation of ZnO layers and improved the performance of poly{4,8-bis[(2-ethylhexyl)-oxy]benzo[1,2-b:4,5-b'] dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophene- 4,6-diyl} (PTB7)-based inverted organic solar cells. The addition of acetic acid to the ZnO precursor solution improved the transparency and conductivity of the sol-gel-synthesized ZnO film, by increasing the grain size of the film. Accordingly, the power conversion efficiency (PCE) of the organic solar cells was improved from 6.42% to 7.55%, which was mainly caused by the enhanced current density and fill factor. The best sample demonstrated a high PCE of 7.85% with negligible hysteresis and good stability. Our results indicate that using acetic acid as an additive for the preparation of ZnO is a simple and effective way of fabricating high-performance inverted organic solar cells.

  2. Effect of atomic layer deposition temperature on the performance of top-down ZnO nanowire transistors

    Science.gov (United States)

    2014-01-01

    This paper studies the effect of atomic layer deposition (ALD) temperature on the performance of top-down ZnO nanowire transistors. Electrical characteristics are presented for 10-μm ZnO nanowire field-effect transistors (FETs) and for deposition temperatures in the range 120°C to 210°C. Well-behaved transistor output characteristics are obtained for all deposition temperatures. It is shown that the maximum field-effect mobility occurs for an ALD temperature of 190°C. This maximum field-effect mobility corresponds with a maximum Hall effect bulk mobility and with a ZnO film that is stoichiometric. The optimized transistors have a field-effect mobility of 10 cm2/V.s, which is approximately ten times higher than can typically be achieved in thin-film amorphous silicon transistors. Furthermore, simulations indicate that the drain current and field-effect mobility extraction are limited by the contact resistance. When the effects of contact resistance are de-embedded, a field-effect mobility of 129 cm2/V.s is obtained. This excellent result demonstrates the promise of top-down ZnO nanowire technology for a wide variety of applications such as high-performance thin-film electronics, flexible electronics, and biosensing. PMID:25276107

  3. Properties of In–N codoped p-type ZnO nanorods grown through a two-step chemical route

    Energy Technology Data Exchange (ETDEWEB)

    Duta, M.; Mihaiu, S.; Munteanu, C. [Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Anastasescu, M., E-mail: manastasescu@icf.ro [Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Osiceanu, P.; Marin, A.; Preda, S. [Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Nicolescu, M., E-mail: mnicolescu2006@yahoo.com [Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Modreanu, M. [Tyndall National Institute, University College, Cork (Ireland); Zaharescu, M.; Gartner, M. [Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania)

    2015-07-30

    Highlights: • p-Type ZnO film codoped with In, N on glass substrate was obtained. • The films were prepared by sol–gel followed by hydrothermal method. • Influence of annealing regimes on opto-electrical properties was studied. • Thin films morphology consists of interconnected, randomly oriented nanorods. • 3.31 × 10{sup 17} cm{sup −3}carrier concentration and 85% transmission were obtained at 500 °C. - Abstract: By codoping with a donor–acceptor pair through a two-step chemical method we have succeed to obtain p-type ZnO thin films on glass. Firstly, a thin undoped ZnO seed layer was deposited by sol–gel method followed by the deposition of In–N codoped ZnO film obtained through the hydrothermal technique. The influence of post-deposition annealing temperature (100 °C, 300 °C and 500 °C) on the samples was investigated from a structural, chemical, morphological and optoelectrical point of view. X-ray diffractometry (XRD), infrared ellipsometry and X-ray photoelectron spectroscopy (XPS) analyses have confirmed the codoped nature of the ZnO thin films. The XRD pattern analysis has established the films have wurtzite nanocrystalline structure, the crystallite sizes varying between 10 nm and 13 nm with the annealing temperature. Continuous and homogenous films with nanorods surface morphology has been obtained, as visualized by scanning electron microscopy measurements. Hall Effect measurements have established that all samples, regardless of annealing temperature, showed p-type conduction due to the successful incorporation of nitrogen in the film, with the highest carrier concentration registered at 500 °C. This is in good correlation with the nitrogen content in the films as revealed from XPS. In all samples, the XPS depth profiling has shown a nitrogen gradient with higher elemental concentration at the surface.

  4. Improvement of stoichiometry in (ZnO)1-x(GaN)x thin films grown by laser ablation

    International Nuclear Information System (INIS)

    Gopalakrishnan, N.; Shin, B.C.; Bhuvana, K.P.; Elanchezhiyan, J.; Balasubramanian, T.

    2008-01-01

    The fabrication of pure and GaN (1 mol%) doped ZnO thin films by KrF excimer laser have been addressed. The fabricated films on Si(1 1 1) substrates have been investigated by X-ray diffraction (XRD), photoluminescence (PL) and atomic force microscopy (AFM) in order to investigate the structural, optical and morphological properties, respectively. The XRD analysis shows that the full width at half maximum (FWHM) of ZnO film is found to be decreased as doped with GaN due to the improvement of the stoichiometery between Zn and O. The PL spectra reveal that the deep level emissions due to native donor defects in pure ZnO are suppressed upon doping with GaN. The images of AFM show that the RMS surface roughness of pure ZnO, 27 nm is reduced to18 nm while doped with 1 mol% GaN. The incorporation of nitrogen in the film is confirmed by glow discharge mass spectroscopy (GDMS). The improved structural, optical and morphological properties of ZnO by GaN dopant due to enhancement of stoichiometry have been discussed in detail

  5. Structural and Morphological Properties of Nanostructured ZnO Particles Grown by Ultrasonic Spray Pyrolysis Method with Horizontal Furnace

    Directory of Open Access Journals (Sweden)

    G. Flores-Carrasco

    2014-01-01

    Full Text Available ZnO nanoparticles were synthesized in a horizontal furnace at 500°C using different zinc nitrate hexahydrate concentrations (0.01 and 0.1 M as reactive solution by ultrasonic spray pyrolysis method. The physical-chemical properties of synthesized ZnO nanoparticles have been characterized by thermogravimetric analysis (TGA, X-ray diffraction (XRD, scanning electron microscopy (SEM, energy dispersive spectroscopy (EDS, and high resolution transmission electron microscopy (HRTEM. With the TGA is has optimized the temperature at which the initial reactive (Zn(NO32·6H2O, is decomposed completely to give way to its corresponding oxide, ZnO. SEM revealed secondary particles with a quasispherical shape that do not change significantly with the increasing of precursor solution concentration as well as some content of the broken spheres. Increasing the precursor solution concentration leads to the increase in the average size of ZnO secondary particles from 248±73 to 470±160 nm; XRD reveals the similar tendency for the crystallite size which changes from 23±4 to 45±4 nm. HRTEM implies that the secondary particles are with hierarchical structure composed of primary nanosized subunits. These results showed that the precursor concentration plays an important role in the evolution on the size, stoichiometry, and morphology of ZnO nanoparticles.

  6. Annealing Temperature Dependence of ZnO Nanostructures Grown by Facile Chemical Bath Deposition for EGFET pH Sensors

    Science.gov (United States)

    Bazilah Rosli, Aimi; Awang, Zaiki; Sobihana Shariffudin, Shafinaz; Herman, Sukreen Hana

    2018-03-01

    Zinc Oxide (ZnO) nanostructures were deposited using chemical bath deposition (CBD) technique in water bath at 95 °C for 4 h. Post-deposition heat treatment in air ambient at various temperature ranging from 200-600 °C for 30 min was applied in order to enhance the electrical properties of ZnO nanostructures as the sensing membrane of extended-gate field effect transistor (EGFET) pH sensor. The as-deposited sample was prepared for comparison. The samples were characterized in terms of physical and sensing properties. FESEM images showed that scattered ZnO nanorods were formed for the as-deposited sample, and the morphology of the ZnO nanorods changed to ZnO nanoflowers when the heat treatment was applied from 200-600 °C. For sensing properties, the samples heated at 300 °C showed the higher sensitivity which was 39.9 mV/pH with the linearity of 0.9792. The sensing properties was increased with the increasing annealing treatment temperature up to 300 °C before decreased drastically.

  7. Crystallinity Improvement of Zn O Thin Film on Different Buffer Layers Grown by MBE

    International Nuclear Information System (INIS)

    Shao-Ying, T.; Che-Hao, L.; Wen-Ming, Ch.; Yang, C.C.; Po-Ju, Ch.; Hsiang-Chen, W.; Ya-Ping, H.

    2012-01-01

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

  8. Investigations of p-type signal for ZnO thin films grown on (100)GaAs substrates by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, D.J. [Nanovation SARL, Orsay (France); Univ. de Technologie de Troyes, Troyes (France); Hosseini Teherani, F. [Nanovation SARL, Orsay (France); Monteiro, T.; Soares, M.; Neves, A.; Carmo, M.; Correia, M.R. [Physics Dept., Univ. of Aveiro (Portugal); Pereira, S. [Physics Dept., Univ. of Aveiro (Portugal); Inst. Tecnologico e Nuclear, Sacavem (Portugal); Lusson, A. [Inst. d' Electronique Fondamentale, Orsay Univ. (France); LPSC - CNRS, Meudon (France); Alves, E.; Barradas, N.P. [Inst. Tecnologico e Nuclear, Sacavem (Portugal); Morrod, J.K.; Prior, K.A. [Physics Dept., Heriot Watt Univ., Edinburgh Scotland (United Kingdom); Kung, P.; Yasan, A.; Razeghi, M. [Center for Quantum Devices, Dept. of Electrical and Computer Engineering, Northwestern Univ., Evanston, IL (United States)

    2006-03-15

    In this work we investigated ZnO films grown on semi-insulating (100)GaAs substrates by pulsed laser deposition. Samples were studied using techniques including X-ray diffraction (XRD), scanning electron microscopy, atomic force microscopy, Raman spectroscopy, temperature dependent photoluminescence, C-V profiling and temperature dependent Hall measurements. The Hall measurements showed a clear p-type response with a relatively high mobility ({proportional_to}260 cm{sup 2}/Vs) and a carrier concentration of {proportional_to}1.8 x 10{sup 19} cm{sup -3}. C-V profiling confirmed a p-type response. XRD and Raman spectroscopy indicated the presence of (0002) oriented wurtzite ZnO plus secondary phase(s) including (101) oriented Zn{sub 2}As{sub 2}O{sub 7}. The results suggest that significant atomic mixing was occurring at the film/substrate interface for films grown at substrate temperatures of 450 C (without post-annealing). (orig.)

  9. Carrier transport in flexible organic bistable devices of ZnO nanoparticles embedded in an insulating poly(methyl methacrylate) polymer layer

    International Nuclear Information System (INIS)

    Son, Dong-Ick; Park, Dong-Hee; Choi, Won Kook; Cho, Sung-Hwan; Kim, Won-Tae; Kim, Tae Whan

    2009-01-01

    The bistable effects of ZnO nanoparticles embedded in an insulating poly(methyl methacrylate) (PMMA) polymer single layer by using flexible polyethylene terephthalate (PET) substrates were investigated. Transmission electron microscopy (TEM) images revealed that ZnO nanoparticles were formed inside the PMMA polymer layer. Current-voltage (I-V) measurement on the Al/ZnO nanoparticles embedded in an insulating PMMA polymer layer/ITO/PET structures at 300 K showed a nonvolatile electrical bistability behavior with a flat-band voltage shift due to the existence of the ZnO nanoparticles, indicative of trapping, storing, and emission of charges in the electronic states of the ZnO nanoparticles. The carrier transport mechanism of the bistable behavior for the fabricated organic bistable device (OBD) structures is described on the basis of the I-V results by analyzing the effect of space charge.

  10. Standing and sitting adlayers in atomic layer deposition of ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Zhengning; Banerjee, Parag, E-mail: parag.banerjee@wustl.edu [Department of Mechanical Engineering & Material Science, Washington University in St. Louis, Missouri 63130 and Institute of Materials Science & Engineering, Washington University in St. Louis, Missouri 63130 (United States); Wu, Fei; Myung, Yoon [Department of Mechanical Engineering & Material Science, Washington University in St. Louis, Missouri 63130 (United States); Fei, Ruixiang [Department of Physics, Washington University in St. Louis, Missouri 63130 (United States); Kanjolia, Ravindra [SAFC Hitech, 1429 Hilldale Ave., Haverhill, Massachusetts 01832 (United States); Yang, Li [Institute of Materials Science & Engineering, Washington University in St. Louis, Missouri 63130 and Department of Physics, Washington University in St. Louis, Missouri 63130 (United States)

    2016-01-15

    The extent of reactivity of diethyl zinc (DEZ) with a hydroxylated surface during atomic layer deposition (ALD) of ZnO using DEZ and water is measured. Two adlayer configurations of DEZ are possible. The “standing” adlayer releases one ethyl group from DEZ. The “sitting” adlayer releases both ethyl groups, thus forming a Zn bridge between two O anions. Density functional theory calculations suggest the sitting configuration is more stable than the standing configuration by 790 meV. In situ quadrupole mass spectroscopy of by-product ethane generated in ALD half cycles indicate that ∼1.56 OH sites react with a DEZ molecule resulting in 71.6% of sitting sites. A simple simulation of a “ball-and-stick” DEZ molecule randomly collapsing on a neighboring site remarkably captures this adlayer behavior. It is concluded that DEZ fraction sitting is a competitive process of a standing DEZ molecule collapsing onto an available neighboring hydroxyl site, as sites vie for occupancy via adsorption and surface diffusion.

  11. Time-resolved photon echoes from donor-bound excitons in ZnO epitaxial layers

    Science.gov (United States)

    Poltavtsev, S. V.; Kosarev, A. N.; Akimov, I. A.; Yakovlev, D. R.; Sadofev, S.; Puls, J.; Hoffmann, S. P.; Albert, M.; Meier, C.; Meier, T.; Bayer, M.

    2017-07-01

    The coherent optical response from 140 nm and 65 nm thick ZnO epitaxial layers is studied using four-wave-mixing spectroscopy with picosecond temporal resolution. Resonant excitation of neutral donor-bound excitons results in two-pulse and three-pulse photon echoes. For the donor-bound A exciton (D0XA ) at temperature of 1.8 K we evaluate optical coherence times T2=33 -50 ps corresponding to homogeneous line widths of 13 -19 μ eV , about two orders of magnitude smaller as compared with the inhomogeneous broadening of the optical transitions. The coherent dynamics is determined mainly by the population decay with time T1=30 -40 ps, while pure dephasing is negligible. Temperature increase leads to a significant shortening of T2 due to interaction with acoustic phonons. In contrast, the loss of coherence of the donor-bound B exciton (D0XB ) is significantly faster (T2=3.6 ps ) and governed by pure dephasing processes.

  12. Photoluminescence characteristics of Pb-doped, molecular-beam-epitaxy grown ZnSe crystal layers

    International Nuclear Information System (INIS)

    Mita, Yoh; Kuronuma, Ryoichi; Inoue, Masanori; Sasaki, Shoichiro; Miyamoto, Yoshinobu

    2004-01-01

    The characteristic green photoluminescence emission and related phenomena in Pb-doped, molecular-beam-epitaxy (MBE)-grown ZnSe crystal layers were investigated to explore the nature of the center responsible for the green emission. The intensity of the green emission showed a distinct nonlinear dependence on excitation intensity. Pb-diffused polycrystalline ZnSe was similarly examined for comparison. The characteristic green emission has been observed only in MBE-grown ZnSe crystal layers with moderate Pb doping. The results of the investigations on the growth conditions, luminescence, and related properties of the ZnSe crystal layers suggest that the green emission is due to isolated Pb replacing Zn and surrounded with regular ZnSe lattice with a high perfection

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

    International Nuclear Information System (INIS)

    Kunj, Saurabh; Sreenivas, K.

    2016-01-01

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

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

    Science.gov (United States)

    Kunj, Saurabh; Sreenivas, K.

    2016-05-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-05-23

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

  16. Electrodeposition of ZnO window layer for an all-atmospheric fabrication process of chalcogenide solar cell

    Science.gov (United States)

    Tsin, Fabien; Venerosy, Amélie; Vidal, Julien; Collin, Stéphane; Clatot, Johnny; Lombez, Laurent; Paire, Myriam; Borensztajn, Stephan; Broussillou, Cédric; Grand, Pierre Philippe; Jaime, Salvador; Lincot, Daniel; Rousset, Jean

    2015-01-01

    This paper presents the low cost electrodeposition of a transparent and conductive chlorine doped ZnO layer with performances comparable to that produced by standard vacuum processes. First, an in-depth study of the defect physics by ab-initio calculation shows that chlorine is one of the best candidates to dope the ZnO. This result is experimentally confirmed by a complete optical analysis of the ZnO layer deposited in a chloride rich solution. We demonstrate that high doping levels (>1020 cm−3) and mobilities (up to 20 cm2 V−1 s−1) can be reached by insertion of chlorine in the lattice. The process developed in this study has been applied on a CdS/Cu(In,Ga)(Se,S)2 p-n junction produced in a pilot line by a non vacuum process, to be tested as solar cell front contact deposition method. As a result efficiency of 14.3% has been reached opening the way of atmospheric production of Cu(In,Ga)(Se,S)2 solar cell. PMID:25753657

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

    International Nuclear Information System (INIS)

    Sun, Hongdan; Xia, Bingbo; Liu, Weiwei; Fang, Guoqing; Wu, Jingjing; Wang, Haibo; Zhang, Ruixue; Kaneko, Shingo; Zheng, Junwei; Wang, Hongyu; Li, Decheng

    2015-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-03-15

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

  19. Sol-gel derived ZnO as an electron transport layer (ETL) for inverted organic solar cells

    Science.gov (United States)

    Tiwari, D. C.; Dwivedi, Shailendra Kumar; Dipak, Phukhrambam; Chandel, Tarun; Sharma, Rishi

    2017-05-01

    In this work, we present the study of the fabrication process of the sol-gel derived zinc oxide (ZnO) as an electron transport layer (ETL.). The solution processed inverted bulk heterojunction organic solar cells based on a thin film blend of poly (3-hexylthiophene 2, 5-diyl) and [6,6]-phenyl-C61-butyric acid methyl ester is prepared. ZnO thin films are annealed at different temperature to optimize the solar cell performance and their characterization for their structural and optical properties are carried out. We have observed Voc=70mV, Jsc=1.33 µA/cm2 and FF=26% from the inverted heterojunction solar cell.

  20. Growth of thin film containing high density ZnO nanorods with low temperature calcinated seed layer

    Science.gov (United States)

    Panda, Rudrashish; Samal, Rudranarayan; Khatua, Lizina; Das, Susanta Kumar

    2018-05-01

    In this work we demonstrate the growth of thin film containing high density ZnO nanorods by using drop casting of the seed layer calcinated at a low temperature of 132 °C. Chemical bath deposition (CBD) method is used to grow the nanorods. X-ray diffraction (XRD) analysis and Field Emission Scanning Electron Microscopy (FESEM) are performed for the structural and morphological characterizations of the nanorods. The average diameter and length of nanorods are found to be 33 nm and 270 nm respectively. The bandgap of the material is estimated to be 3.2 eV from the UV-Visible absorption spectroscopy. The reported method is much more cost-effective and can be used for growth of ZnO nanorods for various applications.

  1. 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.

  2. Interfacial passivation of CdS layer to CdSe quantum dots-sensitized electrodeposited ZnO nanowire thin films

    International Nuclear Information System (INIS)

    Zhang, Jingbo; Sun, Chuanzhen; Bai, Shouli; Luo, Ruixian; Chen, Aifan; Sun, Lina; Lin, Yuan

    2013-01-01

    ZnO porous thin films with nanowire structure were deposited by the one-step electrochemical deposition method. And a CdS layer was coated on the as-deposited ZnO nanowire thin films by successive ionic layer adsorption and reaction (SILAR) method to passivate surface states. Then the films were further sensitized by CdSe quantum dots (QDs) to serve as a photoanode for fabricating quantum dots-sensitized solar cells (QDSSCs). The effect of the CdS interfacial passivation layer on the performance of the QDSSCs was systematically investigated by varying the SILAR cycle number and heating the passivation layer. The amorphous CdS layer with an optimized thickness can effectively suppress the recombination of the injected electrons with holes on QDs and the redox electrolyte. The newly formed CdS layer on the surface of the ZnO nanowire thin film obviously prolongs the electron lifetime in the passivated ZnO nanoporous thin film because of the lower surface trap density in the ZnO nanowires after CdS deposition, which is favorable to the higher short-circuit photocurrent density (J sc ). For the CdSe QDs-sensitized ZnO nanoporous thin film with the interfacial passivation layer, the J sc and conversion efficiency can reach a maximum of 8.36 mA cm −2 and 2.36%, respectively. The conversion efficiency was improved by 83.47% compared with that of the cell based on the CdSe QDs-sensitized ZnO nanoporous thin film without CdS interfacial passivation (0.39%)

  3. Spatial Atomic Layer Deposition of transparent conductive oxides

    NARCIS (Netherlands)

    Illiberi, A.; Scherpenborg, R.; Poodt, P.; Roozeboom, F.

    2013-01-01

    Undoped and indium doped ZnO films have been grown by Spatial Atomic Layer Deposition at atmospheric pressure. The electrical properties of ZnO films are controlled by varying the indium content in the range from 0 to 15 %. A minimum resistivity value of 3 mΩ•cm is measured in 180 nm thick films for

  4. The Effects of Zr Doping on the Optical, Electrical and Microstructural Properties of Thin ZnO Films Deposited by Atomic Layer Deposition

    Directory of Open Access Journals (Sweden)

    Stephania Herodotou

    2015-10-01

    Full Text Available Transparent conducting oxides (TCOs, with high optical transparency (≥85% and low electrical resistivity (10−4 Ω·cm are used in a wide variety of commercial devices. There is growing interest in replacing conventional TCOs such as indium tin oxide with lower cost, earth abundant materials. In the current study, we dope Zr into thin ZnO films grown by atomic layer deposition (ALD to target properties of an efficient TCO. The effects of doping (0–10 at.% Zr were investigated for ~100 nm thick films and the effect of thickness on the properties was investigated for 50–250 nm thick films. The addition of Zr4+ ions acting as electron donors showed reduced resistivity (1.44 × 10−3 Ω·cm, increased carrier density (3.81 × 1020 cm−3, and increased optical gap (3.5 eV with 4.8 at.% doping. The increase of film thickness to 250 nm reduced the electron carrier/photon scattering leading to a further reduction of resistivity to 7.5 × 10−4 Ω·cm and an average optical transparency in the visible/near infrared (IR range up to 91%. The improved n-type properties of ZnO: Zr films are promising for TCO applications after reaching the targets for high carrier density (>1020 cm−3, low resistivity in the order of 10−4 Ω·cm and high optical transparency (≥85%.

  5. SIMS depth profiling of rubber-tyre cord bonding layers prepared using 64Zn depleted ZnO

    International Nuclear Information System (INIS)

    Fulton, W.S.; Sykes, D.E.; Smith, G.C.

    2006-01-01

    Zinc oxide and copper/zinc sulphide layers are formed during vulcanisation and moulding of rubber to brass-coated steel tyre reinforcing cords. Previous studies have described how zinc diffuses through the rubber-brass interface to form zinc sulphide, and combines with oxygen to create zinc oxide during dezincification. The zinc is usually assumed to originate in the brass of the tyre cord, however, zinc oxide is also present in the rubber formulation. We reveal how zinc from these sources is distributed within the interfacial bonding layers, before and after heat and humidity ageing. Zinc oxide produced using 64 Zn-isotope depleted zinc was mixed in the rubber formulation in place of the natural ZnO and the zinc isotope ratios within the interfacial layers were followed by secondary ion mass spectroscopy (SIMS) depth profiling. Variations in the relative ratios of the zinc isotopes during depth profiling were measured for unaged, heat-aged and humidity-aged wire samples and in each case a relatively large proportion of the zinc incorporated into the interfacial layer as zinc sulphide was shown to have originated from ZnO in the rubber compound

  6. Effect of atomic layer deposited Al2O3:ZnO alloys on thin-film silicon photovoltaic devices

    Science.gov (United States)

    Abdul Hadi, Sabina; Dushaq, Ghada; Nayfeh, Ammar

    2017-12-01

    In this work, we present the effects of the Al2O3:ZnO ratio on the optical and electrical properties of aluminum doped ZnO (AZO) layers deposited by atomic layer deposition, along with AZO application as the anti-reflective coating (ARC) layer and in heterojunction configurations. Here, we report complex refractive indices for AZO layers with different numbers of aluminum atomic cycles (ZnO:Al2O3 = 1:0, 39:1, 19:1, and 9:1) and we confirm their validity by fitting models to experimental data. Furthermore, the most conductive layer (ZnO:Al2O3 = 19:1, conductivity ˜4.6 mΩ cm) is used to fabricate AZO/n+/p-Si thin film solar cells and AZO/p-Si heterojunction devices. The impact of the AZO layer on the photovoltaic properties of these devices is studied by different characterization techniques, resulting in the extraction of recombination and energy band parameters related to the AZO layer. Our results confirm that AZO 19:1 can be used as a low cost and effective conductive ARC layer for solar cells. However, AZO/p-Si heterojunctions suffer from an insufficient depletion region width (˜100 nm) and recombination at the interface states, with an estimated potential barrier of ˜0.6-0.62 eV. The work function of AZO (ZnO:Al2O3 = 19:1) is estimated to be in the range between 4.36 and 4.57 eV. These material properties limit the use of AZO as an emitter in Si solar cells. However, the results imply that AZO based heterojunctions could have applications as low-cost photodetectors or photodiodes, operating under relatively low reverse bias.

  7. Improve the open-circuit voltage of ZnO solar cells with inserting ZnS layers by two ways

    International Nuclear Information System (INIS)

    Sun, Yunfei; Yang, Jinghai; Yang, Lili; Cao, Jian; Gao, Ming; Zhang, Zhiqiang; Wang, Zhe; Song, Hang

    2013-01-01

    ZnS NPs layers were deposited on ZnO NRs by two different ways. One is spin coating; the other is successive ionic layer adsorption and reaction (SILAR) method. The ZnO NRs/ZnS NPs composites were verified by X-ray diffraction, X-ray photoelectron spectroscopy, and UV–visible spectrophotometer; their morphologies and thicknesses were examined by scanning electron microscopic and transmission electron microscopic images. The CdS quantum dot sensitized solar cells (QDSSCs) were constructed using ZnO NRs/ZnS NPs composites as photoanode and their photovoltaic characteristic was studied by J–V curves. The results indicated that the way of SILAR is more beneficial for retarding the back transfer of electrons to CdS and electrolyte than spin coating method. The open-circuit voltage increased to 0.59 V by introducing a ZnS layer through SILAR method. When ZnS NPs layer was deposited for 10 times on ZnO NRs, the conversion efficiency of QDSSC shows ∼3.3 folds increments of as-synthesized ZnO solar cell. - Graphical abstract: When ZnO nanorods were deposited by ZnS for 10 times, the conversion efficiency of QDSSC shows ∼3.3 folds increments of as-synthesized ZnO solar cell. Highlights: ► ZnS layers were deposited with two different ways. ► The way of SILAR is more beneficial for retarding the back transfer of electrons. ► The open-circuit voltage increased to 0.59 V by introducing a ZnS layer through SILAR method

  8. Improve the open-circuit voltage of ZnO solar cells with inserting ZnS layers by two ways

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yunfei [State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Graduate School of the Chinese Academy of Sciences, Beijing 100049 (China); Yang, Jinghai, E-mail: jhyang1@jlnu.edu.cn [Institute of Condensed State Physics, Jilin Normal University, Siping 136000 (China); Yang, Lili; Cao, Jian [Institute of Condensed State Physics, Jilin Normal University, Siping 136000 (China); Gao, Ming [State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Graduate School of the Chinese Academy of Sciences, Beijing 100049 (China); Institute of Condensed State Physics, Jilin Normal University, Siping 136000 (China); Zhang, Zhiqiang; Wang, Zhe [Institute of Condensed State Physics, Jilin Normal University, Siping 136000 (China); Song, Hang [State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China)

    2013-04-15

    ZnS NPs layers were deposited on ZnO NRs by two different ways. One is spin coating; the other is successive ionic layer adsorption and reaction (SILAR) method. The ZnO NRs/ZnS NPs composites were verified by X-ray diffraction, X-ray photoelectron spectroscopy, and UV–visible spectrophotometer; their morphologies and thicknesses were examined by scanning electron microscopic and transmission electron microscopic images. The CdS quantum dot sensitized solar cells (QDSSCs) were constructed using ZnO NRs/ZnS NPs composites as photoanode and their photovoltaic characteristic was studied by J–V curves. The results indicated that the way of SILAR is more beneficial for retarding the back transfer of electrons to CdS and electrolyte than spin coating method. The open-circuit voltage increased to 0.59 V by introducing a ZnS layer through SILAR method. When ZnS NPs layer was deposited for 10 times on ZnO NRs, the conversion efficiency of QDSSC shows ∼3.3 folds increments of as-synthesized ZnO solar cell. - Graphical abstract: When ZnO nanorods were deposited by ZnS for 10 times, the conversion efficiency of QDSSC shows ∼3.3 folds increments of as-synthesized ZnO solar cell. Highlights: ► ZnS layers were deposited with two different ways. ► The way of SILAR is more beneficial for retarding the back transfer of electrons. ► The open-circuit voltage increased to 0.59 V by introducing a ZnS layer through SILAR method.

  9. Selective exfoliation of single-layer graphene from non-uniform graphene grown on Cu

    International Nuclear Information System (INIS)

    Lim, Jae-Young; Lee, Jae-Hyun; Jang, Hyeon-Sik; Whang, Dongmok; Joo, Won-Jae; Hwang, SungWoo

    2015-01-01

    Graphene growth on a copper surface via metal-catalyzed chemical vapor deposition has several advantages in terms of providing high-quality graphene with the potential for scale-up, but the product is usually inhomogeneous due to the inability to control the graphene layer growth. The non-uniform regions strongly affect the reliability of the graphene in practical electronic applications. Herein, we report a novel graphene transfer method that allows for the selective exfoliation of single-layer graphene from non-uniform graphene grown on a Cu foil. Differences in the interlayer bonding energy are exploited to mechanically separate only the top single-layer graphene and transfer this to an arbitrary substrate. The dry-transferred single-layer graphene showed electrical characteristics that were more uniform than those of graphene transferred using conventional wet-etching transfer steps. (paper)

  10. Investigation of the Influence of the As-Grown ZnO Nanorods and Applied Potentials on an Electrochemical Sensor for In-Vitro Glucose Monitoring

    Directory of Open Access Journals (Sweden)

    Mohammed Marie

    2017-01-01

    Full Text Available The influence of the as-grown zinc oxide nanorods (ZnO NRs on the fabricated electrochemical sensor for in vitro glucose monitoring were investigated. A direct growth of ZnO NRs was performed on the Si/SiO2/Au electrode, using hydrothermal and sol-gel techniques at low temperatures. The structure, consisting of a Si/SiO2/Au/GOx/Nafion membrane, was considered as a baseline, and it was tested under several applied potential 0.1–0.8 V. The immobilized working electrode, with GOx and a nafion membrane, was characterized amperometrically using a source meter Keithely 2410, and an electrochemical impedance Gamry potentiostat. The sensor exhibited the following: a high sensitivity of ~0.468 mA/cm2 mM, a low detection limit in the order of 166.6 µM, and a fast and sharp response time of around 2 s. The highest sensitivity and the lowest limit of detection were obtained at 0.4 volt, after the growth of ZnO NRs. The highest net sensitivity was obtained after subtracting the sensitivity of the baseline, and it was in the order of 0.315 mA/cm2·mM. The device was tested with a range of glucose concentrations from 1–10 mM, showing a linear line from 3–8 mM, and the device was saturated after exceeding high concentrations of glucose. Such devices can be used for in vitro glucose monitoring, since glucose changes can be accurately detected.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-09-15

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

  12. Synthesis of Vertically Aligned ZnO Nano rods on Various Substrates

    International Nuclear Information System (INIS)

    Hassan, J.J.; Hassan, Z.; Abu Hassan, H.; Mahdi, M.A.

    2011-01-01

    We successfully synthesized vertically aligned ZnO nano rods on Si, GaN, Sic, Al 2 O 3 , ITO, and quartz substrates using microwave assisted chemical bath deposition (MA-CBD) method. All these types of substrates were seeded with PVA-ZnO nano composites layer prior to the nano rods growth. The effect of substrate type on the morphology of the ZnO nano rods was studied. The diameter of grown ZnO nano rods ranged from 50 nm to 200 nm. Structural quality and morphology of ZnO nano rods were determined by x-ray diffraction and scanning electron microscopy, which revealed hexagonal wurtzite structures perpendicular to the substrate along the z-axis in the direction of (002). Photoluminescence measurements of grown ZnO nano rods on all substrates exhibited high UV peak intensity. Raman scattering studies were conducted to estimate the lattice vibration modes. (author)

  13. Epitaxial GaN around ZnO nanopillars

    Energy Technology Data Exchange (ETDEWEB)

    Fikry, Mohamed; Scholz, Ferdinand [Institut fuer Optoelektronik, Universitaet Ulm, Albert-Einstein-Allee 45, 89081 Ulm (Germany); Madel, Manfred; Tischer, Ingo; Thonke, Klaus [Institut fuer Quantenmaterie, Universitaet Ulm, Albert-Einstein-Allee 45, 89081 Ulm (Germany)

    2011-07-01

    We report on an investigation of the epitaxial quality of GaN layers overgrown coaxially around ZnO nanopillars. In a first step, regularly arranged ZnO nanopillars were grown using pre-patterning by e-beam lithography or self-organized hexagonal polystyrene sphere masks. Alternatively, ZnO pillars were also successfully grown on top of GaN pyramids. In a second step, GaN layers were grown around the ZnO pillars by Metal Organic Vapor Phase Epitaxy. At growth temperatures above 800 C, the ZnO pillars are dissolved by the hydrogen carrier gas leaving hollow GaN nanotubes. Characterization involved photoluminescence (PL), scanning electron microscopy and cathodoluminescence. The fair quality of the deposited GaN layers is confirmed by a sharp low temperature PL peak at 3.48 eV attributed to the donor bound exciton emission. Further peaks at 3.42 eV and 3.29 eV show the possible existence of basal plane and prismatic stacking faults.

  14. Enhancing Performance of SnO2-Based Dye-Sensitized Solar Cells Using ZnO Passivation Layer

    Directory of Open Access Journals (Sweden)

    W. M. N. M. B. Wanninayake

    2016-01-01

    Full Text Available Although liquid electrolyte based dye-sensitized solar cells (DSCs have shown higher photovoltaic performance in their class, they still suffer from some practical limitations such as solvent evaporation, leakage, and sealing imperfections. These problems can be circumvented to a certain extent by replacing the liquid electrolytes with quasi-solid-state electrolytes. Even though SnO2 shows high election mobility when compared to the semiconductor material commonly used in DSCs, the cell performance of SnO2-based DSCs is considerably low due to high electron recombination. This recombination effect can be reduced through the use of ultrathin coating layer of ZnO on SnO2 nanoparticles surface. ZnO-based DSCs also showed lower performance due to its amphoteric nature which help dissolve in slightly acidic dye solution. In this study, the effect of the composite SnO2/ZnO system was investigated. SnO2/ZnO composite DSCs showed 100% and 38% increase of efficiency compared to the pure SnO2-based and ZnO-based devices, respectively, with the gel electrolyte consisting of LiI salt.

  15. Study of structural, morphological, optical and electroluminescent properties of undoped ZnO nanorods grown by a simple chemical precipitation

    Directory of Open Access Journals (Sweden)

    Singh A.

    2015-12-01

    Full Text Available In this work, zinc oxide (ZnO nanorods were obtained by a simple chemical precipitation method in the presence of capping agent: polyvinyl pyrrolidone (PVP at room temperature. X-ray diffraction (XRD result indicates that the synthesized undoped ZnO nanorods have hexagonal wurtzite structure without any impurities. It has been observed that the growth direction of the prepared ZnO nanorods is [1 0 1]. XRD analysis revealed that the nanorods have the crystallite size of 49 nm. Crystallite size is calculated by Debye-Scherrer formula and lattice strain is calculated by Williomson-Hall equation. Cell volume, Lorentz factor, Lorentz polarization factor, bond length, texture coefficient, lattice constants and dislocation density have also been studied. We also compared the interplanar spacings and relative peak intensities with their standard values at different angles. The scanning electron microscope (SEM images confirmed the size and shape of these nanorods. It has been found that the diameter of the nanorods ranges from 1.52 μm to 1.61 μm and the length is about 4.89 μm. It has also been observed that at room temperature ultraviolet visible (UV-Vis absorption band is around 355 nm (blue shifted as compared to the bulk. The average particle size has also been calculated by mathematical model of effective mass approximation equation, using UV-Vis absorption peak. Finally, the bandgap has been calculated using UV-absorption peak. Electroluminescence (EL studies show that emission of light is possible at very small threshold voltage and it increases rapidly with increasing applied voltage. It is seen that smaller ZnO nanoparticles give higher electroluminescence brightness starting at lower threshold voltage. The brightness is also affected by increasing the frequency of AC signal.

  16. Effect of growth temperature on the epitaxial growth of ZnO on GaN by ALD

    Science.gov (United States)

    Särkijärvi, Suvi; Sintonen, Sakari; Tuomisto, Filip; Bosund, Markus; Suihkonen, Sami; Lipsanen, Harri

    2014-07-01

    We report on the epitaxial growth of ZnO on GaN template by atomic layer deposition (ALD). Diethylzinc (DEZn) and water vapour (H2O) were used as precursors. The structure and the quality of the grown ZnO layers were studied with scanning electron microscope (SEM), X-ray diffraction (XRD), photoluminescence (PL) measurements and positron annihilation spectroscopy. The ZnO films were confirmed epitaxial, and the film quality was found to improve with increasing deposition temperature in the vicinity of the threshold temperature of two dimensional growth. We conclude that high quality ZnO thin films can be grown by ALD. Interestingly only separate Zn-vacancies were observed in the films, although ZnO thin films typically contain fairly high density of surface pits and vacancy clusters.

  17. Intensity dependence and transient dynamics of donor-acceptor pair recombination in ZnO thin films grown on (001) silicon

    Science.gov (United States)

    Guo, Bing; Qiu, Z. R.; Wong, K. S.

    2003-04-01

    We report room-temperature time-integrated and time-resolved photoluminescence (PL) measurements on a nominally undoped wurtzite ZnO thin film grown on (001) silicon. A linear and sublinear excitation intensity Iex dependence of the PL intensity were observed for the 379.48-nm exciton line and the weak broad green band (˜510 nm), respectively. The green luminescence was found to decay as hyperbolic t-1, and its peak energy was observed to increase nearly logarithmically with increased Iex. These results are in an excellent agreement with the tunnel-assisted donor-deep-acceptor pair (DAP) model so that its large blueshifts of about 25 meV per decade increase in Iex can be accounted for by the screening of the fluctuating impurity potential. Also, the 30-ps fast decay of the exciton emission was attributed to the rapid trapping of carriers at luminescent impurities, while the short lifetime of τ1/e=200 ps for the green luminescence may be due to an alternative trapping by deeper centers in the ZnO. Finally, singly ionized oxygen and zinc vacancies have been tentatively invoked to act as donor-deep-acceptor candidates for the DAP luminescence, respectively.

  18. Tuning of Ag doped core−shell ZnO NWs/Cu2O grown by electrochemical deposition

    International Nuclear Information System (INIS)

    Makhlouf, Houssin; Messaoudi, Olfa; Souissi, Ahmed; Ben Assaker, Ibtissem; Oueslati, Mihrez; Bechelany, Mikhael; Chtourou, Radhouane

    2015-01-01

    ZnO nanowires (NWs)/Cu 2 O–Ag core–shell nanostructures (NSs) have been synthesized by electrochemical deposition method on ITO-coated glass substrates in order to improve the efficiency of the type-II transition of core–shell ZnO NWs/Cu 2 O–Ag NSs. The morphologies of the obtained NSs were studied by scanning electron microscopy confirming the presence of core–shell NSs. The crystalline proprieties were analyzed by x-ray diffraction and micro-Raman measurement: wurtzite ZnO and cuprit Cu 2 O phase were founded. The presence of Ag content in core–shell NS was detected by EDX. Optical measurement reveals an additional contribution δE at about 1.72 eV attributed to the type-II interfacial transition between the valance band of cuprit−Cu 2 O and the conduction band of W−ZnO. The effect of the Ag doping into the type-II transition was investigated. A red shift of the type-II transition was detected according to the Ag concentration. These materials could have potential applications in photocatalytic and photovoltaic fields. (paper)

  19. H{sub 2}O{sub 2}-molecular beam epitaxy of high quality ZnO

    Energy Technology Data Exchange (ETDEWEB)

    El Shaer, A.; Bakin, A.; Che Mofor, A.; Kreye, M.; Waag, A. [Technical University Braunschweig, Institute of Semiconductor Technology, Braunschweig (Germany); Blaesing, J.; Krost, A. [Otto-von-Guericke-University, Institute of Experimental Physics, Magdeburg (Germany); Stoimenos, J. [Aristotele University, Physics Department, Thessaloniki (Greece); Pecz, B. [Hungarian Academy of Sciences, Research Institute for Technical Physics and Materials Science, P.O. Box 49, Budapest (Hungary)

    2007-07-15

    We have studied the growth and characterization of ZnO epilayers on (0001)-sapphire by H{sub 2}O{sub 2}-molecular beam epitaxy (MBE). A high temperature (HT) MgO buffer followed by a low-temperature ZnO buffer was introduced in order to accommodate the lattice mismatch between ZnO and sapphire. The surface morphology of the samples was studied using atomic force microscopy (AFM), and scanning electron microscopy (SEM). The crystalline quality of the layers was investigated by employing high resolution X-ray diffractometry (HRXRD) and high resolution transmission electron microscopy (HRTEM). The electrical properties of the grown ZnO layers were studied by Hall-effect measurements in a standard van der Pauw configuration. The measured surface roughness for the best layers is as low as 0.26 nm rms. HRXRD measurements of the obtained ZnO layers show excellent quality of the single crystalline ZnO heteroepitaxially grown on (0001)-sapphire with a HT MgO buffer layers. The influence of the growth conditions on the crystalline quality is discussed. The FWHM of the HRXRD (0002) rocking curves measured for the 2-inch ZnO-on-sapphire is as low as 27 arcsec with a very high lateral homogeneity across the whole 2-inch ZnO epilayers. The results indicate that H{sub 2}O{sub 2}-MBE is a suitable technique to fabricate ZnO epilayers of very high quality. (orig.)

  20. Growth of novel ZnO nanostructures by soft chemical routes

    International Nuclear Information System (INIS)

    Saravana Kumar, R.; Sathyamoorthy, R.; Matheswaran, P.; Sudhagar, P.; Kang, Yong Soo

    2010-01-01

    Research highlights: Fabrication of diverse ZnO nanostructures through soft chemical routes is both fundamentally interesting and technologically important. Accordingly, in the present work novel ZnO nanostructures namely nanorods/nanospines were grown on glass substrate by integrating SILAR and CBD techniques. This simple approach not only would lead to the development of an effective and commercial growth process for diverse ZnO nanostructures, but also lead to the large-scale preparation of other nanomaterials for many important applications in nanotechnology. - Abstract: We explore a facile route to prepare one-dimensional (1D) ZnO nanostructures including nanorods/nanospines on glass substrates by integrating inexpensive successive ionic layer adsorption and reaction (SILAR) and chemical bath deposition (CBD) methods. The effect of seed layer on the growth and morphology of the ZnO nanostructures was investigated. Accordingly, the surface modification of the seed layer prepared by SILAR was carried out by employing two different drying processes namely (a) allowing the hot substrate to cool for certain period of time before immersing in the ion-exchange bath, and (b) immediate immersion of the hot substrate into the ion-exchange bath. X-ray diffraction (XRD) analysis of the ZnO films revealed hexagonal wurtzite structure with preferential orientation along c-axis, while the scanning electron microscopy (SEM) revealed the dart-like and spherical shaped ZnO seed particles. ZnO nanostructures grown by CBD over the dart-like and spherical shaped ZnO seed particles resulted in the hierarchical and aligned ZnO nanospines/nanorods respectively. Room temperature photoluminescence (PL) study exhibited highly intense UV emission with weak visible emissions in the visible region. The growth mechanism and the role of seed layer morphology on the formation of ZnO nanostructures were discussed.

  1. Growth of novel ZnO nanostructures by soft chemical routes

    Energy Technology Data Exchange (ETDEWEB)

    Saravana Kumar, R. [PG and Research, Department of Physics, Kongunadu Arts and Science College (Autonomous), Coimbatore 641 029, Tamil Nadu (India); Sathyamoorthy, R., E-mail: rsathya59@gmail.co [PG and Research, Department of Physics, Kongunadu Arts and Science College (Autonomous), Coimbatore 641 029, Tamil Nadu (India); Matheswaran, P. [PG and Research, Department of Physics, Kongunadu Arts and Science College (Autonomous), Coimbatore 641 029, Tamil Nadu (India); Sudhagar, P.; Kang, Yong Soo [Energy Materials Laboratory, WCU Program Department of Energy Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)

    2010-09-10

    Research highlights: Fabrication of diverse ZnO nanostructures through soft chemical routes is both fundamentally interesting and technologically important. Accordingly, in the present work novel ZnO nanostructures namely nanorods/nanospines were grown on glass substrate by integrating SILAR and CBD techniques. This simple approach not only would lead to the development of an effective and commercial growth process for diverse ZnO nanostructures, but also lead to the large-scale preparation of other nanomaterials for many important applications in nanotechnology. - Abstract: We explore a facile route to prepare one-dimensional (1D) ZnO nanostructures including nanorods/nanospines on glass substrates by integrating inexpensive successive ionic layer adsorption and reaction (SILAR) and chemical bath deposition (CBD) methods. The effect of seed layer on the growth and morphology of the ZnO nanostructures was investigated. Accordingly, the surface modification of the seed layer prepared by SILAR was carried out by employing two different drying processes namely (a) allowing the hot substrate to cool for certain period of time before immersing in the ion-exchange bath, and (b) immediate immersion of the hot substrate into the ion-exchange bath. X-ray diffraction (XRD) analysis of the ZnO films revealed hexagonal wurtzite structure with preferential orientation along c-axis, while the scanning electron microscopy (SEM) revealed the dart-like and spherical shaped ZnO seed particles. ZnO nanostructures grown by CBD over the dart-like and spherical shaped ZnO seed particles resulted in the hierarchical and aligned ZnO nanospines/nanorods respectively. Room temperature photoluminescence (PL) study exhibited highly intense UV emission with weak visible emissions in the visible region. The growth mechanism and the role of seed layer morphology on the formation of ZnO nanostructures were discussed.

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

    KAUST Repository

    Jagadamma, Lethy Krishnan; Al-Senani, Mohammed; Amassian, Aram

    2015-01-01

    The present work details a facile and low-temperature (125C) solution-processed Al-doped ZnO (AZO) buffer layer functioning very effectively as electron accepting/hole blocking layer for a wide range of polymer:fullerene bulk heterojunction systems

  3. Intersubband spectroscopy of ZnO/ZnMgO quantum wells grown on m-plane ZnO substrates for quantum cascade device applications (Conference Presentation)

    Science.gov (United States)

    Quach, Patrick; Jollivet, Arnaud; Isac, Nathalie; Bousseksou, Adel; Ariel, Frédéric; Tchernycheva, Maria; Julien, François H.; Montes Bajo, Miguel; Tamayo-Arriola, Julen; Hierro, Adrián.; Le Biavan, Nolwenn; Hugues, Maxime; Chauveau, Jean-Michel

    2017-03-01

    Quantum cascade (QC) lasers opens new prospects for powerful sources operating at THz frequencies. Up to now the best THz QC lasers are based on intersubband emission in GaAs/AlGaAs quantum well (QW) heterostructures. The maximum operating temperature is 200 K, which is too low for wide-spread applications. This is due to the rather low LO-phonon energy (36 meV) of GaAs-based materials. Indeed, thermal activation allows non-radiative path through electron-phonon interaction which destroys the population inversion. Wide band gap materials such as ZnO have been predicted to provide much higher operating temperatures because of the high value of their LO-phonon energy. However, despite some observations of intersubband absorption in c-plane ZnO/ZnMgO quantum wells, little is known on the fundamental parameters such as the conduction band offset in such heterostructures. In addition the internal field inherent to c-plane grown heterostuctures is an handicap for the design of QC lasers and detectors. In this talk, we will review a systematic investigation of ZnO/ZnMgO QW heterostructures with various Mg content and QW thicknesses grown by plasma molecular beam epitaxy on low-defect m-plane ZnO substrates. We will show that most samples exhibit TM-polarized intersubband absorption at room temperature linked either to bound-to-quasi bound inter-miniband absorption or to bound-to bound intersubband absorption depending on the Mg content of the barrier material. This systematic study allows for the first time to estimate the conduction band offset of ZnO/ZnMgO heterostructures, opening prospects for the design of QC devices operating at THz frequencies. This was supported by the European Union's Horizon 2020 research and innovation programme under grant agreement #665107.

  4. Positron annihilation studies of defects in molecular beam epitaxy grown III-V layers

    International Nuclear Information System (INIS)

    Umlor, M.T.; Keeble, D.J.; Cooke, P.W.

    1994-01-01

    A summary of recent positron annihilation experiments on molecular beam epitaxy (MBE) grown III-V layers is Presented. Variable energy positron beam measurements on Al 0.32 Ga 0.68 As undoped and Si doped have been completed. Positron trapping at a open volume defect in Al 0.32 Ga 0.68 :Si for temperatures from 300 to 25 K in the dark was observed. The positron trap was lost after 1.3 eV illumination at 25K. These results indicate an open volume defect is associated with the local structure of the deep donor state of the DX center. Stability of MBE GaAs to thermal annealing war, investigated over the temperature range of 230 to 700 degrees C, Proximity wafer furnace anneals in flowing argon were used, Samples grown above 450 degrees C were shown to be stable but for sample below this temperature an anneal induced vacancy related defect was produced for anneals between 400 and 500 degrees C. The nature of the defect was shown to be different for material grown at 350 and 230 degrees C. Activation energies of 2.5 eV to 2.3 eV were obtained from isochronal anneal experiments for samples grown at 350 and 230 degrees C, respectively

  5. Formation of transparent ZnO layers by MePIIID

    International Nuclear Information System (INIS)

    Maendl, S.; Rauschenbach, B.

    2006-01-01

    ZnO thin films were deposited using metal plasma immersion ion implantation and deposition (MePIIID) with high voltage pulses from 0 to 10 kV at a duty cycle of 9%. All films exhibit a (0 0 2) fibre texture of the hexagonal ZnO phase. With increasing bias voltage, an increased sub-band gap absorption was observed with spectroscopic ellipsometry, together with preferential sputtering of oxygen from the film. Only a partial reversal of this effect was obtained with an increased oxygen/zinc ratio on the supply side showing that additional radiation induced defects are present in the film at high pulse voltages

  6. Decreased Charge Transport Barrier and Recombination of Organic Solar Cells by Constructing Interfacial Nanojunction with Annealing-Free ZnO and Al Layers.

    Science.gov (United States)

    Liu, Chunyu; Zhang, Dezhong; Li, Zhiqi; Zhang, Xinyuan; Guo, Wenbin; Zhang, Liu; Ruan, Shengping; Long, Yongbing

    2017-07-05

    To overcome drawbacks of the electron transport layer, such as complex surface defects and unmatched energy levels, we successfully employed a smart semiconductor-metal interfacial nanojunciton in organic solar cells by evaporating an ultrathin Al interlayer onto annealing-free ZnO electron transport layer, resulting in a high fill factor of 73.68% and power conversion efficiency of 9.81%. The construction of ZnO-Al nanojunction could effectively fill the surface defects of ZnO and reduce its work function because of the electron transfer from Al to ZnO by Fermi level equilibrium. The filling of surface defects decreased the interfacial carrier recombination in midgap trap states. The reduced surface work function of ZnO-Al remodulated the interfacial characteristics between ZnO and [6,6]-phenyl C71-butyric acid methyl ester (PC 71 BM), decreasing or even eliminating the interfacial barrier against the electron transport, which is beneficial to improve the electron extraction capacity. The filled surface defects and reduced interfacial barrier were realistically observed by photoluminescence measurements of ZnO film and the performance of electron injection devices, respectively. This work provides a simple and effective method to simultaneously solve the problems of surface defects and unmatched energy level for the annealing-free ZnO or other metal oxide semiconductors, paving a way for the future popularization in photovoltaic devices.

  7. Optimization of an Electron Transport Layer to Enhance the Power Conversion Efficiency of Flexible Inverted Organic Solar Cells

    Directory of Open Access Journals (Sweden)

    Lee Kang Hyuck

    2010-01-01

    Full Text Available Abstract The photovoltaic (PV performance of flexible inverted organic solar cells (IOSCs with an active layer consisting of a blend of poly(3-hexylthiophene and [6, 6]-phenyl C61-butlyric acid methyl ester was investigated by varying the thicknesses of ZnO seed layers and introducing ZnO nanorods (NRs. A ZnO seed layer or ZnO NRs grown on the seed layer were used as an electron transport layer and pathway to optimize PV performance. ZnO seed layers were deposited using spin coating at 3,000 rpm for 30 s onto indium tin oxide (ITO-coated polyethersulphone (PES substrates. The ZnO NRs were grown using an aqueous solution method at a low temperature (90°C. The optimized device with ZnO NRs exhibited a threefold increase in PV performance compared with that of a device consisting of a ZnO seed layer without ZnO NRs. Flexible IOSCs fabricated using ZnO NRs with improved PV performance may pave the way for the development of PV devices with larger interface areas for effective exciton dissociation and continuous carrier transport paths.

  8. Influence of ZnO seed layer precursor molar ratio on the density of interface defects in low temperature aqueous chemically synthesized ZnO nanorods/GaN light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Alnoor, Hatim, E-mail: hatim.alnoor@liu.se; Iandolo, Donata; Willander, Magnus; Nur, Omer [Department of Science and Technology (ITN), Linköping University, SE-601 74 Norrköping (Sweden); Pozina, Galia; Khranovskyy, Volodymyr; Liu, Xianjie [Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-583 81 Linköping (Sweden)

    2016-04-28

    Low temperature aqueous chemical synthesis (LT-ACS) of zinc oxide (ZnO) nanorods (NRs) has been attracting considerable research interest due to its great potential in the development of light-emitting diodes (LEDs). The influence of the molar ratio of the zinc acetate (ZnAc): KOH as a ZnO seed layer precursor on the density of interface defects and hence the presence of non-radiative recombination centers in LT-ACS of ZnO NRs/GaN LEDs has been systematically investigated. The material quality of the as-prepared seed layer as quantitatively deduced by the X-ray photoelectron spectroscopy is found to be influenced by the molar ratio. It is revealed by spatially resolved cathodoluminescence that the seed layer molar ratio plays a significant role in the formation and the density of defects at the n-ZnO NRs/p-GaN heterostructure interface. Consequently, LED devices processed using ZnO NRs synthesized with molar ratio of 1:5 M exhibit stronger yellow emission (∼575 nm) compared to those based on 1:1 and 1:3 M ratios as measured by the electroluminescence. Furthermore, seed layer molar ratio shows a quantitative dependence of the non-radiative defect densities as deduced from light-output current characteristics analysis. These results have implications on the development of high-efficiency ZnO-based LEDs and may also be helpful in understanding the effects of the ZnO seed layer on defect-related non-radiative recombination.

  9. Deposition of stress free c-axis oriented LiNbO3 thin film grown on (002) ZnO coated Si substrate

    International Nuclear Information System (INIS)

    Shandilya, Swati; Gupta, Vinay; Tomar, Monika

    2012-01-01

    C-axis oriented lithium niobate thin films have been deposited on Si substrate using RF sputtering technique. A thin buffer layer of c-axis (002) oriented ZnO on Si substrate has been used as a nucleating layer to promote the growth of (006) oriented LiNbO 3 film. The processing gas composition and pressure are found to be very critical in obtaining stress free LiNbO 3 film having desired (006) orientation. The LiNbO 3 films deposited under unique combination of sputtering pressure (10 mTorr) and argon percentage (80%) in reactive gas (Ar + O 2 ) composition become almost stress free having lattice parameter (1.3867 A) close to the bulk value. The observed variation in the structural properties and optical phonon modes observed by Raman spectroscopic studies of the oriented LiNbO 3 thin film with stress has been correlated with growth kinetics.

  10. Carbon-coated ZnO mat passivation by atomic-layer-deposited HfO2 as an anode material for lithium-ion batteries.

    Science.gov (United States)

    Jung, Mi-Hee

    2017-11-01

    ZnO has had little consideration as an anode material in lithium-ion batteries compared with other transition-metal oxides due to its inherent poor electrical conductivity and large volume expansion upon cycling and pulverization of ZnO-based electrodes. A logical design and facile synthesis of ZnO with well-controlled particle sizes and a specific morphology is essential to improving the performance of ZnO in lithium-ion batteries. In this paper, a simple approach is reported that uses a cation surfactant and a chelating agent to synthesize three-dimensional hierarchical nanostructured carbon-coated ZnO mats, in which the ZnO mats are composed of stacked individual ZnO nanowires and form well-defined nanoporous structures with high surface areas. In order to improve the performance of lithium-ion batteries, HfO 2 is deposited on the carbon-coated ZnO mat electrode via atomic layer deposition. Lithium-ion battery devices based on the carbon-coated ZnO mat passivation by atomic layer deposited HfO 2 exhibit an excellent initial discharge and charge capacities of 2684.01 and 963.21mAhg -1 , respectively, at a current density of 100mAg -1 in the voltage range of 0.01-3V. They also exhibit cycle stability after 125 cycles with a capacity of 740mAhg -1 and a remarkable rate capability. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. Efficient Color-Stable Inverted White Organic Light-Emitting Diodes with Outcoupling-Enhanced ZnO Layer.

    Science.gov (United States)

    Zhao, Xin-Dong; Li, Yan-Qing; Xiang, Heng-Yang; Zhang, Yi-Bo; Chen, Jing-De; Xu, Lu-Hai; Tang, Jian-Xin

    2017-01-25

    Inverted organic light-emitting diode (OLED) has attracted extensive attention due to the demand in active-matrix OLED display panels as its geometry enables the direct connection with n-channel transistor backplane on the substrate. One key challenge of high-performance inverted OLED is an efficient electron-injection layer with superior electrical and optical properties to match the indium tin oxide cathode on substrate. We here propose a synergistic electron-injection architecture using surface modification of ZnO layer to simultaneously promote electron injection into organic emitter and enhance out-coupling of waveguided light. An efficient inverted white OLED is realized by introducing the nanoimprinted aperiodic nanostructure of ZnO for broadband and angle-independent light out-coupling and inserting an n-type doped interlayer for energy level tuning and injection barrier lowering. As a result, the optimized inverted white OLEDs have an external quantum efficiency of 42.4% and a power efficiency of 85.4 lm W 1- , which are accompanied by the superiority of angular color stability over the visible wavelength range. Our results may inspire a promising approach to fabricate high-efficiency inverted OLEDs for large-scale display panels.

  12. 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.

  13. Effect of Different HTM Layers and Electrical Parameters on ZnO Nanorod-Based Lead-Free Perovskite Solar Cell for High-Efficiency Performance

    Directory of Open Access Journals (Sweden)

    Farhana Anwar

    2017-01-01

    Full Text Available Simulation has been done using SCAPS-1D to examine the efficiency of CH3NH3SnI3-based solar cells including various HTM layers such as spiro-OMeTAD, Cu2O, and CuSCN. ZnO nanorod array has been considered as an ETM layer. Device parameters such as thickness of the CH3NH3SnI3 layer, defect density of interfaces, density of states, and metal work function were studied. For optimum parameters of all three structures, efficiency of 20.21%, 20.23%, and 18.34% has been achieved for spiro-OMeTAD, Cu2O, and CuSCN, respectively. From the simulations, an alternative lead-free perovskite solar cell is introduced with the CH3NH3SnI3 absorber layer, ZnO nanorod ETM layer, and Cu2O HTM layer.

  14. Some studies on successive ionic layer adsorption and reaction (SILAR) grown indium sulphide thin films

    International Nuclear Information System (INIS)

    Pathan, H.M.; Lokhande, C.D.; Kulkarni, S.S.; Amalnerkar, D.P.; Seth, T.; Han, Sung-Hwan

    2005-01-01

    Indium sulphide (In 2 S 3 ) thin films were grown on amorphous glass substrate by the successive ionic layer adsorption and reaction (SILAR) method. X-ray diffraction, optical absorption, scanning electron microscopy (SEM) and Rutherford back scattering (RBS) were applied to study the structural, optical, surface morphological and compositional properties of the indium sulphide thin films. Utilization of triethanolamine and hydrazine hydrate complexed indium sulphate and sodium sulphide as precursors resulted in nanocrystalline In 2 S 3 thin film. The optical band gap was found to be 2.7 eV. The film appeared to be smooth and homogeneous from SEM study

  15. Triboelectric charge generation by semiconducting SnO2 film grown by atomic layer deposition

    Science.gov (United States)

    Lee, No Ho; Yoon, Seong Yu; Kim, Dong Ha; Kim, Seong Keun; Choi, Byung Joon

    2017-07-01

    Improving the energy harvesting efficiency of triboelectric generators (TEGs) requires exploring new types of materials that can be used, and understanding their properties. In this study, we have investigated semiconducting SnO2 thin films as friction layers in TEGs, which has not been explored thus far. Thin films of SnO2 with various thicknesses were grown by atomic layer deposition on Si substrates. Either polymer or glass was used as counter friction layers. Vertical contact/separation mode was utilized to evaluate the TEG efficiency. The results indicate that an increase in the SnO2 film thickness from 5 to 25 nm enhances the triboelectric output voltage of the TEG. Insertion of a 400-nm-thick Pt sub-layer between the SnO2 film and Si substrate further increased the output voltage up to 120 V in a 2 cm × 2 cm contact area, while the enhancement was cancelled out by inserting a 10-nm-thick insulating Al2O3 film between SnO2 and Pt films. These results indicate that n-type semiconducting SnO2 films can provide triboelectric charge to counter-friction layers in TEGs.[Figure not available: see fulltext.

  16. Mosaic Structure Characterization of the AlInN Layer Grown on Sapphire Substrate

    Directory of Open Access Journals (Sweden)

    Engin Arslan

    2014-01-01

    Full Text Available The 150 nm thick, (0001 orientated wurtzite-phase Al1−xInxN epitaxial layers were grown by metal organic chemical vapor deposition on GaN (2.3 µm template/(0001 sapphire substrate. The indium (x concentration of the Al1−xInxN epitaxial layers was changed as 0.04, 0.18, 0.20, 0.47, and 0.48. The Indium content (x, lattice parameters, and strain values in the AlInN layers were calculated from the reciprocal lattice mapping around symmetric (0002 and asymmetric (10–15 reflection of the AlInN and GaN layers. The mosaic structure characteristics of the AlInN layers, such as lateral and vertical coherence lengths, tilt and twist angle, heterogeneous strain, and dislocation densities (edge and screw type dislocations of the AlInN epilayers, were investigated by using high-resolution X-ray diffraction measurements and with a combination of Williamson-Hall plot and the fitting of twist angles.

  17. STM studies of GeSi thin layers epitaxially grown on Si(111)

    Science.gov (United States)

    Motta, N.; Sgarlata, A.; De Crescenzi, M.; Derrien, J.

    1996-08-01

    Ge/Si alloys were prepared in UHV by solid phase epitaxy on Si(111) substrates. The alloy formation, as a function of the evaporation rate and the Ge layer thickness has been followed in situ by RHEED and scanning tunneling microscopy. The 5 × 5 surface reconstruction appeared after annealing at 450°C Ge layers (up to 10 Å thick), obtained from a low rate Knudsen cell evaporator. In this case a nearly flat and uniform layer of reconstructed alloy was observed. When using an e-gun high rate evaporator we needed to anneal the Ge layer up to 780°C to obtain a 5 × 5 reconstruction. The grown layer was not flat, with many steps and Ge clusters; at high coverages (10 Å and more) large Ge islands appeared. Moreover, we then succeeded in visualizing at atomic resolution the top of some of these Ge islands which displayed a 2 × 1 reconstruction, probably induced from the high compressive strain due to the lattice mismatch with the substrate. We suggest that this unusual behavior could be connected to the high evaporation rate, which helped the direct formation of Ge microcrystals on the Si substrate during the deposition process.

  18. Effects of Complex Structured Anodic Oxide Dielectric Layer Grown in Pore Matrix for Aluminum Capacitor.

    Science.gov (United States)

    Shin, Jin-Ha; Yun, Sook Young; Lee, Chang Hyoung; Park, Hwa-Sun; Suh, Su-Jeong

    2015-11-01

    Anodization of aluminum is generally divided up into two types of anodic aluminum oxide structures depending on electrolyte type. In this study, an anodization process was carried out in two steps to obtain high dielectric strength and break down voltage. In the first step, evaporated high purity Al on Si wafer was anodized in oxalic acidic aqueous solution at various times at a constant temperature of 5 degrees C. In the second step, citric acidic aqueous solution was used to obtain a thickly grown sub-barrier layer. During the second anodization process, the anodizing potential of various ranges was applied at room temperature. An increased thickness of the sub-barrier layer in the porous matrix was obtained according to the increment of the applied anodizing potential. The microstructures and the growth of the sub-barrier layer were then observed with an increasing anodizing potential of 40 to 300 V by using a scanning electron microscope (SEM). An impedance analyzer was used to observe the change of electrical properties, including the capacitance, dissipation factor, impedance, and equivalent series resistance (ESR) depending on the thickness increase of the sub-barrier layer. In addition, the breakdown voltage was measured. The results revealed that dielectric strength was improved with the increase of sub-barrier layer thickness.

  19. α-Ga2O3 grown by low temperature atomic layer deposition on sapphire

    Science.gov (United States)

    Roberts, J. W.; Jarman, J. C.; Johnstone, D. N.; Midgley, P. A.; Chalker, P. R.; Oliver, R. A.; Massabuau, F. C.-P.

    2018-04-01

    α-Ga2O3 is a metastable phase of Ga2O3 of interest for wide bandgap engineering since it is isostructural with α-In2O3 and α-Al2O3. α-Ga2O3 is generally synthesised under high pressure (several GPa) or relatively high temperature (∼500 °C). In this study, we report the growth of α-Ga2O3 by low temperature atomic layer deposition (ALD) on sapphire substrate. The film was grown at a rate of 0.48 Å/cycle, and predominantly consists of α-Ga2O3 in the form of (0001) -oriented columns originating from the interface with the substrate. Some inclusions were also present, typically at the tips of the α phase columns and most likely comprising ε-Ga2O3. The remainder of the Ga2O3 film - i.e. nearer the surface and between the α-Ga2O3 columns, was amorphous. The film was found to be highly resistive, as is expected for undoped material. This study demonstrates that α-Ga2O3 films can be grown by low temperature ALD and suggests the possibility of a new range of ultraviolet optoelectronic and power devices grown by ALD. The study also shows that scanning electron diffraction is a powerful technique to identify the different polymorphs of Ga2O3 present in multiphase samples.

  20. Stress engineering in GaN structures grown on Si(111) substrates by SiN masking layer application

    Energy Technology Data Exchange (ETDEWEB)

    Szymański, Tomasz, E-mail: tomasz.szymanski@pwr.edu.pl; Wośko, Mateusz; Paszkiewicz, Bogdan; Paszkiewicz, Regina [The Faculty of Microsystem Electronics and Photonics, Wrocaw University of Technology, Janiszewskiego 11/17, 50-372 Wroclaw (Poland); Drzik, Milan [International Laser Center, Ilkovicova 3, 841-04 Bratislava 4 (Slovakia)

    2015-07-15

    GaN layers without and with an in-situ SiN mask were grown by using metal organic vapor phase epitaxy for three different approaches used in GaN on silicon(111) growth, and the physical and optical properties of the GaN layers were studied. For each approach applied, GaN layers of 1.4 μm total thickness were grown, using silan SiH{sub 4} as Si source in order to grow Si{sub x}N{sub x} masking layer. The optical micrographs, scanning electron microscope images, and atomic force microscope images of the grown samples revealed cracks for samples without SiN mask, and micropits, which were characteristic for the samples grown with SiN mask. In situ reflectance signal traces were studied showing a decrease of layer coalescence time and higher degree of 3D growth mode for samples with SiN masking layer. Stress measurements were conducted by two methods—by recording micro-Raman spectra and ex-situ curvature radius measurement—additionally PLs spectra were obtained revealing blueshift of PL peak positions with increasing stress. The authors have shown that a SiN mask significantly improves physical and optical properties of GaN multilayer systems reducing stress in comparison to samples grown applying the same approaches but without SiN masking layer.

  1. Unusual strain in homoepitaxial CdTe(001) layers grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Heinke, H.; Waag, A.; Moeller, M.O.; Regnet, M.M.; Landwehr, G. [Physikalisches Institut, Univ. Wuerzburg (Germany)

    1994-01-01

    For homoepitaxial CdTe(001) films grown by molecular beam epitaxy onto CdTe(001) substrates, a difference between the lattice constants of the substrate and the layer was systematically observed using high resolution X-ray diffraction. Reciprocal space maps point out an unusual strain state of such layers which is indicated by the position of their reciprocal lattice points. They lie in a section of reciprocal space which is usually forbidden by elasticity theory. The strain is laterally anisotropic leading to a monoclinic symmetry of the thin films. The lateral strain is depth dependent. Possible reasons for the formation of the unusual strain are discussed, and a correlation of the unusual strain with the growth conditions is attempted

  2. Molecular beam epitaxy grown Ge/Si pin layer sequence for photonic devices

    International Nuclear Information System (INIS)

    Schulze, J.; Oehme, M.; Werner, J.

    2012-01-01

    A key challenge to obtain a convergence of classical Si-based microelectronics and optoelectronics is the manufacturing of photonic integrated circuits integrable into classical Si-based integrated circuits. This integration would be greatly enhanced if similar facilities and technologies could be used. Therefore one approach is the development of optoelectronic components and devices made from group-IV-based materials such as SiGe, Ge or Ge:Sn. In this paper the optoelectronic performances of a pin diode made from a Ge/Si heterostructure pin layer sequence grown by molecular beam epitaxy are discussed. After a detailed description of the layer sequence growth and the device manufacturing process it will be shown that – depending on the chosen operating point and device design – the diode serves as a broadband high speed photo detector, Franz–Keldysh effect modulator or light emitting diode.

  3. Molecular beam epitaxy grown Ge/Si pin layer sequence for photonic devices

    Energy Technology Data Exchange (ETDEWEB)

    Schulze, J., E-mail: schulze@iht.uni-stuttgart.de; Oehme, M.; Werner, J.

    2012-02-01

    A key challenge to obtain a convergence of classical Si-based microelectronics and optoelectronics is the manufacturing of photonic integrated circuits integrable into classical Si-based integrated circuits. This integration would be greatly enhanced if similar facilities and technologies could be used. Therefore one approach is the development of optoelectronic components and devices made from group-IV-based materials such as SiGe, Ge or Ge:Sn. In this paper the optoelectronic performances of a pin diode made from a Ge/Si heterostructure pin layer sequence grown by molecular beam epitaxy are discussed. After a detailed description of the layer sequence growth and the device manufacturing process it will be shown that - depending on the chosen operating point and device design - the diode serves as a broadband high speed photo detector, Franz-Keldysh effect modulator or light emitting diode.

  4. RBS/channeling study of buried Ge quantum dots grown in a Si layer

    International Nuclear Information System (INIS)

    Fonseca, A.; Alves, E.; Barradas, N.P.; Leitao, J.P.; Sobolev, N.A.; Carmo, M.C.; Nikiforov, A.I.; Presting, H.

    2006-01-01

    In last decades we have been assisting to a crescent importance of low dimensional systems for the fabrication of nano- and opto-electronic devices. Ge quantum dots (QDs) are well suited for fulfilling these requirements. In this work we present and discuss Ge/Si multilayer and single layer samples grown by molecular beam epitaxy. RBS/channeling results reveal the evidence for the presence of Ge QD for the thickest (with 1 ML of SiO 2 and 0.9 nm of Ge) single layer sample. On the other hand Ge atoms are fully substitutional incorporated in the Si matrix for the thinner sample, excluding the formation of Ge QDs. Multilayer sample shows an angular deviation of the Ge curve (-0.48 o ) with respect to the Si ones, indicating the compressive strain of the films. A tetragonal distortion of (1.78 ± 0.19%) was calculated

  5. Fabrication of a Combustion-Reacted High-Performance ZnO Electron Transport Layer with Silver Nanowire Electrodes for Organic Solar Cells.

    Science.gov (United States)

    Park, Minkyu; Lee, Sang-Hoon; Kim, Donghyuk; Kang, Juhoon; Lee, Jung-Yong; Han, Seung Min

    2018-02-28

    Herein, a new methodology for solution-processed ZnO fabrication on Ag nanowire network electrode via combustion reaction is reported, where the amount of heat emitted during combustion was minimized by controlling the reaction temperature to avoid damaging the underlying Ag nanowires. The degree of participation of acetylacetones, which are volatile fuels in the combustion reaction, was found to vary with the reaction temperature, as revealed by thermogravimetric and compositional analyses. An optimized processing temperature of 180 °C was chosen to successfully fabricate a combustion-reacted ZnO and Ag nanowire hybrid electrode with a sheet resistance of 30 Ω/sq and transmittance of 87%. A combustion-reacted ZnO on Ag nanowire hybrid structure was demonstrated as an efficient transparent electrode and electron transport layer for the PTB7-Th-based polymer solar cells. The superior electrical conductivity of combustion-reacted ZnO, compared to that of conventional sol-gel ZnO, increased the external quantum efficiency over the entire absorption range, whereas a unique light scattering effect due to the presence of nanopores in the combustion-derived ZnO further enhanced the external quantum efficiency in the 450-550 nm wavelength range. A power conversion efficiency of 8.48% was demonstrated for the PTB7-Th-based polymer solar cell with the use of a combustion-reacted ZnO/Ag NW hybrid transparent electrode.

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

    Science.gov (United States)

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

    2011-10-07

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

  7. Photo-electrochemical and impedance investigation of passive layers grown anodically on titanium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, N.T.C. [Departamento de Quimica, Universidade Federal de Sao Carlos, CP 676, 13560-970 Sao Carlos, SP (Brazil); Biaggio, S.R. [Departamento de Quimica, Universidade Federal de Sao Carlos, CP 676, 13560-970 Sao Carlos, SP (Brazil); Piazza, S. [Dipartimento di Ingegneria Chimica dei Processi e dei Materiali, Universita di Palermo, Viale delle Scienze, 90128 Palermo (Italy)]. E-mail: piazza@dicpm.unipa.it; Sunseri, C. [Dipartimento di Ingegneria Chimica dei Processi e dei Materiali, Universita di Palermo, Viale delle Scienze, 90128 Palermo (Italy); Di Quarto, F. [Dipartimento di Ingegneria Chimica dei Processi e dei Materiali, Universita di Palermo, Viale delle Scienze, 90128 Palermo (Italy)

    2004-10-15

    The anodic behaviour of two titanium cast alloys, obtained by fusion in a voltaic arc under argon atmosphere, was analyzed in aerated aqueous solutions having different pH values. In all solutions the alloys, having nominal compositions Ti-50Zr at.% and Ti-13Zr-13Nb wt.%, displayed a valve-metal behaviour, owing to the formation of barrier-type oxide films. Passive films, grown potentiodynamically up to about 9 V, were investigated by photocurrent spectroscopy (PCS) and electrochemical impedance spectroscopy (EIS). These passive layers show photoactivity under anodic polarizations, with optical gaps close to 3.55 and 3.25 eV for the binary and the ternary alloy, respectively, independent of the anodizing electrolyte. Films grown on the binary alloy present insulating behaviour and anodic impedance spectra with one time constant; this was interpreted in terms of a single-layer mixed Ti-Zr oxide enriched in Ti with respect to the alloy composition. Also for the ternary alloy the results are consistent with the formation, upon anodization, of Ti-Nb-Zr mixed oxide films, but they display n-type semiconducting behaviour, owing to their poor content of ZrO{sub 2} groups.

  8. Conduction and stability of holmium titanium oxide thin films grown by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Castán, H., E-mail: helena@ele.uva.es [Department of Electronic, University of Valladolid, 47011 Valladolid (Spain); García, H.; Dueñas, S.; Bailón, L. [Department of Electronic, University of Valladolid, 47011 Valladolid (Spain); Miranda, E. [Departament d' Enginyería Electrònica, Universitat Autónoma de Barcelona, 08193 Bellaterra (Spain); Kukli, K. [Department of Chemistry, University of Helsinki, FI-00014 Helsinki (Finland); Institute of Physics, University of Tartu, EE-50411,Tartu (Estonia); Kemell, M.; Ritala, M.; Leskelä, M. [Department of Chemistry, University of Helsinki, FI-00014 Helsinki (Finland)

    2015-09-30

    Holmium titanium oxide (HoTiO{sub x}) thin films of variable chemical composition grown by atomic layer deposition are studied in order to assess their suitability as dielectric materials in metal–insulator–metal electronic devices. The correlation between thermal and electrical stabilities as well as the potential usefulness of HoTiO{sub x} as a resistive switching oxide are also explored. It is shown that the layer thickness and the relative holmium content play important roles in the switching behavior of the devices. Cycled current–voltage measurements showed that the resistive switching is bipolar with a resistance window of up to five orders of magnitude. In addition, it is demonstrated that the post-breakdown current–voltage characteristics in HoTiO{sub x} are well described by a power-law model in a wide voltage and current range which extends from the soft to the hard breakdown regimes. - Highlights: • Gate and memory suitabilities of atomic layer deposited holmium titanium oxide. • Holmium titanium oxide exhibits resistive switching. • Layer thickness and holmium content influence the resistive switching. • Low and high resistance regimes follow a power-law model. • The power-law model can be extended to the hard breakdown regime.

  9. Infrared Reflectance Analysis of Epitaxial n-Type Doped GaN Layers Grown on Sapphire.

    Science.gov (United States)

    Tsykaniuk, Bogdan I; Nikolenko, Andrii S; Strelchuk, Viktor V; Naseka, Viktor M; Mazur, Yuriy I; Ware, Morgan E; DeCuir, Eric A; Sadovyi, Bogdan; Weyher, Jan L; Jakiela, Rafal; Salamo, Gregory J; Belyaev, Alexander E

    2017-12-01

    Infrared (IR) reflectance spectroscopy is applied to study Si-doped multilayer n + /n 0 /n + -GaN structure grown on GaN buffer with GaN-template/sapphire substrate. Analysis of the investigated structure by photo-etching, SEM, and SIMS methods showed the existence of the additional layer with the drastic difference in Si and O doping levels and located between the epitaxial GaN buffer and template. Simulation of the experimental reflectivity spectra was performed in a wide frequency range. It is shown that the modeling of IR reflectance spectrum using 2 × 2 transfer matrix method and including into analysis the additional layer make it possible to obtain the best fitting of the experimental spectrum, which follows in the evaluation of GaN layer thicknesses which are in good agreement with the SEM and SIMS data. Spectral dependence of plasmon-LO-phonon coupled modes for each GaN layer is obtained from the spectral dependence of dielectric of Si doping impurity, which is attributed to compensation effects by the acceptor states.

  10. Electrical characteristics and density of states of thin-film transistors based on sol-gel derived ZnO channel layers with different annealing temperatures

    Science.gov (United States)

    Wang, S.; Mirkhani, V.; Yapabandara, K.; Cheng, R.; Hernandez, G.; Khanal, M. P.; Sultan, M. S.; Uprety, S.; Shen, L.; Zou, S.; Xu, P.; Ellis, C. D.; Sellers, J. A.; Hamilton, M. C.; Niu, G.; Sk, M. H.; Park, M.

    2018-04-01

    We report on the fabrication and electrical characterization of bottom gate thin-film transistors (TFTs) based on a sol-gel derived ZnO channel layer. The effect of annealing of ZnO active channel layers on the electrical characteristics of the ZnO TFTs was systematically investigated. Photoluminescence (PL) spectra indicate that the crystal quality of the ZnO improves with increasing annealing temperature. Both the device turn-on voltage (Von) and threshold voltage (VT) shift to a positive voltage with increasing annealing temperature. As the annealing temperature is increased, both the subthreshold slope and the interfacial defect density (Dit) decrease. The field effect mobility (μFET) increases with annealing temperature, peaking at 800 °C and decreases upon further temperature increase. An improvement in transfer and output characteristics was observed with increasing annealing temperature. However, when the annealing temperature reaches 900 °C, the TFTs demonstrate a large degradation in both transfer and output characteristics, which is possibly produced by non-continuous coverage of the film. By using the temperature-dependent field effect measurements, the localized sub-gap density of states (DOSs) for ZnO TFTs with different annealing temperatures were determined. The DOSs for the subthreshold regime decrease with increasing annealing temperature from 600 °C to 800 °C and no substantial change was observed with further temperature increase to 900 °C.

  11. Ultra-smooth epitaxial Ge grown on Si(001) utilizing a thin C-doped Ge buffer layer

    KAUST Repository

    Mantey, J.; Hsu, W.; James, J.; Onyegam, E. U.; Guchhait, S.; Banerjee, S. K.

    2013-01-01

    Here, we present work on epitaxial Ge films grown on a thin buffer layer of C doped Ge (Ge:C). The growth rate of Ge:C is found to slow over time and is thus unsuitable for thick (>20 nm) layers. We demonstrate Ge films from 10 nm to >150 nm

  12. Efficient inverted bulk-heterojunction solar cells from low-temperature processing of amorphous ZnO buffer layers

    KAUST Repository

    Jagadamma, Lethy Krishnan; Abdelsamie, Maged; El Labban, Abdulrahman; Aresu, Emanuele; Ngongang Ndjawa, Guy Olivier; Anjum, Dalaver H.; Cha, Dong Kyu; Beaujuge, Pierre; Amassian, Aram

    2014-01-01

    In this report, we demonstrate that solution-processed amorphous zinc oxide (a-ZnO) interlayers prepared at low temperatures (∼100 °C) can yield inverted bulk-heterojunction (BHJ) solar cells that are as efficient as nanoparticle-based ZnO requiring comparably more complex synthesis or polycrystalline ZnO films prepared at substantially higher temperatures (150-400 °C). Low-temperature, facile solution-processing approaches are required in the fabrication of BHJ solar cells on flexible plastic substrates, such as PET. Here, we achieve efficient inverted solar cells with a-ZnO buffer layers by carefully examining the correlations between the thin film morphology and the figures of merit of optimized BHJ devices with various polymer donors and PCBM as the fullerene acceptor. We find that the most effective a-ZnO morphology consists of a compact, thin layer with continuous substrate coverage. In parallel, we emphasize the detrimental effect of forming rippled surface morphologies of a-ZnO, an observation which contrasts with results obtained in polycrystalline ZnO thin films, where rippled morphologies have been reported to improve efficiency. After optimizing the a-ZnO morphology at low processing temperature for inverted P3HT:PCBM devices, achieving a power conversion efficiency (PCE) of ca. 4.1%, we demonstrate inverted solar cells with low bandgap polymer donors on glass/flexible PET substrates: PTB7:PC71BM (PCE: 6.5% (glass)/5.6% (PET)) and PBDTTPD:PC71BM (PCE: 6.7% (glass)/5.9% (PET)). Finally, we show that a-ZnO based inverted P3HT:PCBM BHJ solar cells maintain ca. 90-95% of their initial PCE even after a full year without encapsulation in a nitrogen dry box, thus demonstrating excellent shelf stability. The insight we have gained into the importance of surface morphology in amorphous zinc oxide buffer layers should help in the development of other low-temperature solution-processed metal oxide interlayers for efficient flexible solar cells. This journal is

  13. Enhanced Doping Efficiency of Al-Doped ZnO by Atomic Layer Deposition Using Dimethylaluminum Isopropoxide as an Alternative Aluminum Precursor

    NARCIS (Netherlands)

    Wu, Y.; Potts, S.E.; Hermkens, P.M.; Knoops, H.C.M.; Roozeboom, F.; Kessels, W.M.M.

    2013-01-01

    Atomic layer deposition offers the unique opportunity to control, at the atomic level, the 3D distribution of dopants in highly uniform and conformal thin films. Here, it is demonstrated that the maximum doping efficiency of Al in ZnO can be improved from ∼10% to almost 60% using dimethylaluminum

  14. Annealing effects of ZnO nanorods on dye-sensitized solar cell efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Jooyoung; Lee, Juneyoung [Department of Chemical and Biomolecular Engineering, Yonsei University, 134 Shinchon-dong, Seodaemoon-gu, Seoul 120-749 (Korea, Republic of); Lim, Sangwoo, E-mail: swlim@yonsei.ac.k [Department of Chemical and Biomolecular Engineering, Yonsei University, 134 Shinchon-dong, Seodaemoon-gu, Seoul 120-749 (Korea, Republic of)

    2010-06-01

    Dye-sensitized solar cells (DSSCs) were fabricated using ZnO nanorod arrays vertically grown on fluorine-doped tin oxide (FTO) glass using a low-temperature hydrothermal method. When the ZnO seed layer was annealed, greater DSSC efficiency was obtained. This may be attributed to the improvement of adhesion between the FTO and the seed layer and the corresponding effective growth of the ZnO nanorods. The DSSCs fabricated using ZnO nanorods which underwent annealing were more efficient than those that did not undergo annealing. The ZnO nanorods which were annealed in N{sub 2}/H{sub 2} or O{sub 2} had increased dye loadings due to higher OH concentrations on the hydrophilic surface, which contributed to the improved DSSC efficiency. The fill factor increased after the annealing of the ZnO nanorods, potentially due to the improved crystallinity of the ZnO nanorods. In this study, annealing of both the seed layer and the ZnO nanorods resulted in the greatest DSSC efficiency.

  15. Characteristics of one-port surface acoustic wave resonator fabricated on ZnO/6H-SiC layered structure

    Science.gov (United States)

    Li, Qi; Qian, Lirong; Fu, Sulei; Song, Cheng; Zeng, Fei; Pan, Feng

    2018-04-01

    Characteristics of one-port surface acoustic wave (SAW) resonators fabricated on ZnO/6H-SiC layered structure were investigated experimentally and theoretically. Phase velocities (V p), electromechanical coupling coefficients (K 2), quality factors (Q), and temperature coefficients of frequency (TCF) of Rayleigh wave (0th mode) and first- and second-order Sezawa wave (1st and 2nd modes, respectively) for different piezoelectric film thickness-to-wavelength (h ZnO /λ) ratios were systematically studied. Results demonstrated that one-port SAW resonators fabricated on the ZnO/6H-SiC layered structure were promising for high-frequency SAW applications with moderate K 2 and TCF values. A high K 2 of 2.44% associated with a V p of 5182 m s‑1 and a TCF of  ‑41.8 ppm/°C was achieved at h ZnO /λ  =  0.41 in the 1st mode, while a large V p of 7210 m s‑1 with a K 2 of 0.19% and a TCF of  ‑36.4 ppm/°C was obtained for h ZnO /λ  =  0.31 in the 2nd mode. Besides, most of the parameters were reported for the first time and will be helpful for the future design and optimization of SAW devices fabricated on ZnO/6H-SiC layered structures.

  16. Control of ZnO Nanorod Defects to Enhance Carrier Transportation in p-Cu₂O/i-ZnO Nanorods/n-IGZO Heterojunction.

    Science.gov (United States)

    Ke, Nguyen Huu; Trinh, Le Thi Tuyet; Mung, Nguyen Thi; Loan, Phan Thi Kieu; Tuan, Dao Anh; Truong, Nguyen Huu; Tran, Cao Vinh; Hung, Le Vu Tuan

    2017-01-01

    The p-Cu₂O/i-ZnO nanorods/n-IGZO heterojunctions were fabricated by electrochemical and sputtering method. ZnO nanorods were grown on conductive indium gallium zinc oxide (IGZO) thin film and then p-Cu₂O layer was deposited on ZnO nanorods to form the heterojunction. ZnO nanorods play an important role in carrier transport mechanisms and performance of the junction. The changing of defects in ZnO nanorods by annealing samples in air and vacuum have studied. The XRD, photoluminescence (PL) spectroscopy, and FTIR were used to study about structure, and defects in ZnO nanorods. The SEM, i–V characteristics methods were also used to define structure, electrical properties of the heterojunctions layers. The results show that the defects in ZnO nanorods affected remarkably on performance of heterojunctions of solar cells.

  17. Mg-doped ZnO thin films deposited by the atomic layer chemical vapor deposition for the buffer layer of CIGS solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Li, Zhao-Hui [Department of Electronics Engineering, Gachon University, Soojung-gu, Seongnam city 461-701, Gyunggi-do (Korea, Republic of); Center for Photovoltaic and Solar Energy, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen city 518055 (China); Cho, Eou-Sik [Department of Electronics Engineering, Gachon University, Soojung-gu, Seongnam city 461-701, Gyunggi-do (Korea, Republic of); Kwon, Sang Jik, E-mail: sjkwon@gachon.ac.kr [Department of Electronics Engineering, Gachon University, Soojung-gu, Seongnam city 461-701, Gyunggi-do (Korea, Republic of)

    2014-09-30

    Highlights: • Mg-doped ZnO film as CIGS buffer was prepared by ALD process. • The grain size of ZnO-like hexagonal phase decreased with Mg content. • The transmittance and crystallinity increased but the band gap decreased with temperature. - Abstract: Mg-doped ZnO [(Zn, Mg)O] thin films were prepared by atomic layer chemical vapor deposition (ALCVD) process with different Mg content, using diethyl zinc, biscyclopentadienyl magnesium, and water as the metal and oxygen sources, respectively. The ratio of Mg to Zn was varied by changing the pulse ratio of MgCp{sub 2} to DEZn precursor to study its effect on the properties of (Zn, Mg)O thin films. From the experimental results, it was shown that the grain size of the ZnO-like hexagonal phase (Zn, Mg)O decreased as the Mg content increased. But the transmittance and optical band gap of (Zn, Mg)O films increased with the increase of the Mg content. In addition, the effect of the substrate temperature on the properties of (Zn, Mg)O films was also investigated. The deposition rate, transmittance, and crystallinity of (Zn, Mg)O films increased as the substrate temperature increased. But its band gap decreased slightly with the increase of substrate temperature.

  18. Research Update: Atmospheric pressure spatial atomic layer deposition of ZnO thin films: Reactors, doping, and devices

    Directory of Open Access Journals (Sweden)

    Robert L. Z. Hoye

    2015-04-01

    Full Text Available Atmospheric pressure spatial atomic layer deposition (AP-SALD has recently emerged as an appealing technique for rapidly producing high quality oxides. Here, we focus on the use of AP-SALD to deposit functional ZnO thin films, particularly on the reactors used, the film properties, and the dopants that have been studied. We highlight how these films are advantageous for the performance of solar cells, organometal halide perovskite light emitting diodes, and thin-film transistors. Future AP-SALD technology will enable the commercial processing of thin films over large areas on a sheet-to-sheet and roll-to-roll basis, with new reactor designs emerging for flexible plastic and paper electronics.

  19. Research Update: Atmospheric pressure spatial atomic layer deposition of ZnO thin films: Reactors, doping, and devices

    Energy Technology Data Exchange (ETDEWEB)

    Hoye, Robert L. Z., E-mail: rlzh2@cam.ac.uk, E-mail: jld35@cam.ac.uk; MacManus-Driscoll, Judith L., E-mail: rlzh2@cam.ac.uk, E-mail: jld35@cam.ac.uk [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Muñoz-Rojas, David [LMGP, University Grenoble-Alpes, CNRS, F-3800 Grenoble (France); Nelson, Shelby F. [Kodak Research Laboratories, Eastman Kodak Company, Rochester, New York 14650 (United States); Illiberi, Andrea; Poodt, Paul [Holst Centre/TNO Thin Film Technology, Eindhoven, 5656 AE (Netherlands); Roozeboom, Fred [Holst Centre/TNO Thin Film Technology, Eindhoven, 5656 AE (Netherlands); Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, Eindhoven, 5600 MB (Netherlands)

    2015-04-01

    Atmospheric pressure spatial atomic layer deposition (AP-SALD) has recently emerged as an appealing technique for rapidly producing high quality oxides. Here, we focus on the use of AP-SALD to deposit functional ZnO thin films, particularly on the reactors used, the film properties, and the dopants that have been studied. We highlight how these films are advantageous for the performance of solar cells, organometal halide perovskite light emitting diodes, and thin-film transistors. Future AP-SALD technology will enable the commercial processing of thin films over large areas on a sheet-to-sheet and roll-to-roll basis, with new reactor designs emerging for flexible plastic and paper electronics.

  20. Influence of the local absorber layer thickness on the performance of ZnO nanorod solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Belaidi, Abdelhak; Dittrich, Thomas; Kieven, David; Tornow, Julian; Schwarzburg, Klaus; Lux-Steiner, Martha [Helmholtz-Zentrum Berlin fuer Materialien und Energie, Berlin (Germany)

    2008-08-15

    The local absorber layer thickness (d{sub local}) of solar cells with extremely thin absorber was changed between 10 nm and 70 nm. As a model system, ZnO nanorod arrays (electron conductor) with fixed internal surface area coated with In{sub 2}S{sub 3} (absorber) and impregnated with CuSCN (transparent hole conductor) were applied. The performance of the small area solar cells depended critically on d{sub local}. The highest short circuit current density was reached for the lowest d{sub local}. In contrast, the highest open circuit voltage was obtained for the highest d{sub local}. A maximum energy conversion efficiency of 3.4% at AM1.5 was achieved. Limiting factors are discussed.(copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Impact of surface morphology of Si substrate on performance of Si/ZnO heterojunction devices grown by atomic layer deposition technique

    International Nuclear Information System (INIS)

    Hazra, Purnima; Singh, Satyendra Kumar; Jit, Satyabrata

    2015-01-01

    In this paper, the authors have investigated the structural, optical, and electrical characteristics of silicon nanowire (SiNW)/zinc oxide (ZnO) core–shell nanostructure heterojunctions and compared their characteristics with Si/ZnO planar heterojunctions to investigate the effect of surface morphology of Si substrate in the characteristics of Si/ZnO heterojunction devices. In this work, ZnO thin film was conformally deposited on both p-type 〈100〉 planar Si substrate and substrate with vertically aligned SiNW arrays by atomic layer deposition (ALD) method. The x-ray diffraction spectra show that the crystalline structures of Si/ZnO heterojunctions are having (101) preferred orientation, whereas vertically oriented SiNW/ZnO core–shell heterojunctions are having (002)-oriented wurtzite crystalline structures. The photoluminescence (PL) spectra of Si/ZnO heterojunctions show a very sharp single peak at 377 nm, corresponding to the bandgap of ZnO material with no other defect peaks in visible region; hence, these devices can have applications only in UV region. On the other hand, SiNW/ZnO heterojunctions are having band-edge peak at 378 nm along with a broad emission band, spreading almost throughout the entire visible region with a peak around 550 nm. Therefore, ALD-grown SiNW/ZnO heterojunctions can emit green and red light simultaneously. Reflectivity measurement of the heterojunctions further confirms the enhancement of visible region peak in the PL spectra of SiNW/ZnO heterojunctions, as the surface of the SiNW/ZnO heterojunctions exhibits extremely low reflectance ( 20%). The current–voltage characteristics of both Si/ZnO and SiNW/ZnO heterojunctions are measured with large area ohmic contacts on top and bottom of the structure to compare the electrical characteristics of the devices. Due to large surface to-volume ratio of SiNW/ZnO core–shell heterojunction devices, the output current rating is about 130 times larger compared to their planar

  2. Impact of surface morphology of Si substrate on performance of Si/ZnO heterojunction devices grown by atomic layer deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Hazra, Purnima; Singh, Satyendra Kumar [Department of Electronics and Communication Engineering, Motilal Neheru National Institute of Technology, Allahabad 211004 (India); Jit, Satyabrata, E-mail: sjit.ece@itbhu.ac.in [Department of Electronics Engineering, Indian Institute of Technology (BHU), Varanasi 221005 (India)

    2015-01-01

    In this paper, the authors have investigated the structural, optical, and electrical characteristics of silicon nanowire (SiNW)/zinc oxide (ZnO) core–shell nanostructure heterojunctions and compared their characteristics with Si/ZnO planar heterojunctions to investigate the effect of surface morphology of Si substrate in the characteristics of Si/ZnO heterojunction devices. In this work, ZnO thin film was conformally deposited on both p-type 〈100〉 planar Si substrate and substrate with vertically aligned SiNW arrays by atomic layer deposition (ALD) method. The x-ray diffraction spectra show that the crystalline structures of Si/ZnO heterojunctions are having (101) preferred orientation, whereas vertically oriented SiNW/ZnO core–shell heterojunctions are having (002)-oriented wurtzite crystalline structures. The photoluminescence (PL) spectra of Si/ZnO heterojunctions show a very sharp single peak at 377 nm, corresponding to the bandgap of ZnO material with no other defect peaks in visible region; hence, these devices can have applications only in UV region. On the other hand, SiNW/ZnO heterojunctions are having band-edge peak at 378 nm along with a broad emission band, spreading almost throughout the entire visible region with a peak around 550 nm. Therefore, ALD-grown SiNW/ZnO heterojunctions can emit green and red light simultaneously. Reflectivity measurement of the heterojunctions further confirms the enhancement of visible region peak in the PL spectra of SiNW/ZnO heterojunctions, as the surface of the SiNW/ZnO heterojunctions exhibits extremely low reflectance (<3%) in the visible wavelength region compared to Si/ZnO heterojunctions (>20%). The current–voltage characteristics of both Si/ZnO and SiNW/ZnO heterojunctions are measured with large area ohmic contacts on top and bottom of the structure to compare the electrical characteristics of the devices. Due to large surface to-volume ratio of SiNW/ZnO core–shell heterojunction devices, the

  3. Luminescence and deep-level transient spectroscopy of grown dislocation-rich Si layers

    Directory of Open Access Journals (Sweden)

    I. I. Kurkina

    2012-09-01

    Full Text Available The charge deep-level transient spectroscopy (Q-DLTS is applied to the study of the dislocation-rich Si layers grown on a surface composed of dense arrays of Ge islands prepared on the oxidized Si surface. This provides revealing three deep-level bands located at EV + 0.31 eV, EC – 0.35 eV and EC – 0.43 eV using the stripe-shaped p-i-n diodes fabricated on the basis of these layers. The most interesting observation is the local state recharging process which proceeds with low activation energy (∼50 meV or without activation. The recharging may occur by carrier tunneling within deep-level bands owing to the high dislocation density ∼ 1011 - 1012 cm-2. This result is in favor of the suggestion on the presence of carrier transport between the deep states, which was previously derived from the excitation dependence of photoluminescence (PL intensity. Electroluminescence (EL spectra measured from the stripe edge of the same diodes contain two peaks centered near 1.32 and 1.55 μm. Comparison with PL spectra indicates that the EL peaks are generated from arsenic-contaminated and pure areas of the layers, respectively.

  4. Silicon transport in sputter-deposited tantalum layers grown under ion bombardment

    International Nuclear Information System (INIS)

    Gallais, P.; Hantzpergue, J.J.; Remy, J.C.; Roptin, D.

    1988-01-01

    Tantalum was sputter deposited on (111) Si substrate under low-energy ion bombardment in order to study the effects of the ion energy on the silicon transport into the Ta layer. The Si substrate was heated up to 500 0 C during growth. For ion energies up to 180 eV silicon is not transported into tantalum and the growth temperature has no effect. An ion bombardment energy of 280 eV enhances the transport of silicon throughout the tantalum layer. Growth temperatures up to 300 0 C have no effect on the silicon transport which is mainly enhanced by the ion bombardment. For growth temperatures between 300 and 500 0 C, the silicon transport is also enhanced by the thermal diffusion. The experimental depth distribution of silicon is similar to the theoretical depth distribution calculated for the case of an interdiffusion. The ion-enhanced process of silicon transport is characterized by an activation energy of 0.4 eV. Silicon into the layers as-grown at 500 0 C is in both states, amorphous silicide and microcrystalline cubic silicon

  5. Effect of ZnO decoration on the photovoltaic performance of TiO{sub 2} based dye sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Long; Zhai, Bao-gai [School of Mathematics and Physics, Changzhou University, Jiangsu 213164 (China); Ma, Qing-lan [School of Electronics and Information, Nantong University, Jiangsu 226019 (China); Huang, Yuan Ming, E-mail: dongshanisland@126.com [School of Electronics and Information, Nantong University, Jiangsu 226019 (China)

    2014-08-25

    Highlights: • Various ZnO morphologies coated TiO{sub 2} photoanodes are formed and applied to DSSCs. • The effect of photoanode morphology on performance of DSSCs was studied. • ZnO NRs@TiO{sub 2} electrode provides more dye absorption and fast transfer pathway. • The η of DSSC with ZnO NRs@TiO{sub 2} is increased over fourfold than other DSSCs. - Abstract: ZnO nanoparticles and one-dimensional vertically aligned ZnO nanorods were grown on the TiO{sub 2} layers in the photoanodes via the hydrothermal method at 60 and 90 °C, respectively. The effect of ZnO decoration on the photovoltaic performance of TiO{sub 2} based dye sensitized solar cells (DSSCs) was investigated. The morphologies, crystalline structures and optical properties of the synthesized ZnO nanoparticles and ZnO nanorods were characterized by field-emission scanning electron microscope, X-ray diffractometer and photoluminescence spectroscopy, respectively. The photocurrent–voltage curves of the fabricated DSSCs showed that the ZnO nanorods decorated DSSCs exhibited better photovoltaic performance than the ZnO nanoparticles decorated DSSCs. The improved performance of the ZnO nanorods decorated DSSCs can be ascribed to the fact that the vertically aligned ZnO nanorods provide high specific surface area for dye adsorption and the efficient pathway for electron transportation.

  6. Uniform GaN thin films grown on (100) silicon by remote plasma atomic layer deposition

    International Nuclear Information System (INIS)

    Shih, Huan-Yu; Chen, Miin-Jang; Lin, Ming-Chih; Chen, Liang-Yih

    2015-01-01

    The growth of uniform gallium nitride (GaN) thin films was reported on (100) Si substrate by remote plasma atomic layer deposition (RP-ALD) using triethylgallium (TEG) and NH 3 as the precursors. The self-limiting growth of GaN was manifested by the saturation of the deposition rate with the doses of TEG and NH 3 . The increase in the growth temperature leads to the rise of nitrogen content and improved crystallinity of GaN thin films, from amorphous at a low deposition temperature of 200 °C to polycrystalline hexagonal structures at a high growth temperature of 500 °C. No melting-back etching was observed at the GaN/Si interface. The excellent uniformity and almost atomic flat surface of the GaN thin films also infer the surface control mode of the GaN thin films grown by the RP-ALD technique. The GaN thin films grown by RP-ALD will be further applied in the light-emitting diodes and high electron mobility transistors on (100) Si substrate. (paper)

  7. Post-growth annealing induced change of conductivity in As-doped ZnO grown by radio frequency magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    To, C. K.; Yang, B.; Su, S. C.; Ling, C. C.; Beling, C. D.; Fung, S. [Department of Physics, University of Hong Kong, Pokfulam Road (Hong Kong)

    2011-12-01

    Arsenic-doped ZnO films were fabricated by radio frequency magnetron sputtering method at a relatively low substrate temperature of 200 deg. C. Post-growth annealing in air was carried out up to a temperature of 1000 deg. C. The samples were characterized by Hall measurement, positron annihilation spectroscopy (PAS), secondary ion mass spectroscopy (SIMS), and cathodoluminescence (CL). The as-grown sample was of n-type and it converted to p-type material after the 400 deg. C annealing. The resulting hole concentration was found to increase with annealing temperature and reached a maximum of 6 x 10{sup 17} cm{sup -3} at the annealing temperature of 600 deg. C. The origin of the p-type conductivity was consistent with the As{sub Zn}(V{sub Zn}){sub 2} shallow acceptor model. Further increasing the annealing temperature would decrease the hole concentration of the samples finally converted the sample back to n-type. With evidence, it was suggested that the removal of the p-type conductivity was due to the dissociation of the As{sub Zn}(V{sub Zn}){sub 2} acceptor and the creation of the deep level defect giving rise to the green luminescence.

  8. Post-growth annealing induced change of conductivity in As-doped ZnO grown by radio frequency magnetron sputtering

    Science.gov (United States)

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

    2011-12-01

    Arsenic-doped ZnO films were fabricated by radio frequency magnetron sputtering method at a relatively low substrate temperature of 200 °C. Post-growth annealing in air was carried out up to a temperature of 1000 °C. The samples were characterized by Hall measurement, positron annihilation spectroscopy (PAS), secondary ion mass spectroscopy (SIMS), and cathodoluminescence (CL). The as-grown sample was of n-type and it converted to p-type material after the 400 °C annealing. The resulting hole concentration was found to increase with annealing temperature and reached a maximum of 6 × 1017 cm-3 at the annealing temperature of 600 °C. The origin of the p-type conductivity was consistent with the AsZn(VZn)2 shallow acceptor model. Further increasing the annealing temperature would decrease the hole concentration of the samples finally converted the sample back to n-type. With evidence, it was suggested that the removal of the p-type conductivity was due to the dissociation of the AsZn(VZn)2 acceptor and the creation of the deep level defect giving rise to the green luminescence.

  9. Post-growth annealing induced change of conductivity in As-doped ZnO grown by radio frequency magnetron sputtering

    International Nuclear Information System (INIS)

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

    2011-01-01

    Arsenic-doped ZnO films were fabricated by radio frequency magnetron sputtering method at a relatively low substrate temperature of 200 deg. C. Post-growth annealing in air was carried out up to a temperature of 1000 deg. C. The samples were characterized by Hall measurement, positron annihilation spectroscopy (PAS), secondary ion mass spectroscopy (SIMS), and cathodoluminescence (CL). The as-grown sample was of n-type and it converted to p-type material after the 400 deg. C annealing. The resulting hole concentration was found to increase with annealing temperature and reached a maximum of 6 x 10 17 cm -3 at the annealing temperature of 600 deg. C. The origin of the p-type conductivity was consistent with the As Zn (V Zn ) 2 shallow acceptor model. Further increasing the annealing temperature would decrease the hole concentration of the samples finally converted the sample back to n-type. With evidence, it was suggested that the removal of the p-type conductivity was due to the dissociation of the As Zn (V Zn ) 2 acceptor and the creation of the deep level defect giving rise to the green luminescence.

  10. Surface diffusion coefficient of Au atoms on single layer graphene grown on Cu

    Energy Technology Data Exchange (ETDEWEB)

    Ruffino, F., E-mail: francesco.ruffino@ct.infn.it; Cacciato, G.; Grimaldi, M. G. [Dipartimento di Fisica ed Astronomia-Universitá di Catania, via S. Sofia 64, 95123 Catania, Italy and MATIS IMM-CNR, via S. Sofia 64, 95123 Catania (Italy)

    2014-02-28

    A 5 nm thick Au film was deposited on single layer graphene sheets grown on Cu. By thermal processes, the dewetting phenomenon of the Au film on the graphene was induced so to form Au nanoparticles. The mean radius, surface-to-surface distance, and surface density evolution of the nanoparticles on the graphene sheets as a function of the annealing temperature were quantified by scanning electron microscopy analyses. These quantitative data were analyzed within the classical mean-field nucleation theory so to obtain the temperature-dependent Au atoms surface diffusion coefficient on graphene: D{sub S}(T)=[(8.2±0.6)×10{sup −8}]exp[−(0.31±0.02(eV)/(at) )/kT] cm{sup 2}/s.

  11. Thickness optimization of the ZnO based TCO layer in a CZTSSe solar cell. Evolution of its performance with thickness when external temperature changes.

    Science.gov (United States)

    Chadel, Meriem; Moustafa Bouzaki, Mohammed; Chadel, Asma; Aillerie, Michel; Benyoucef, Boumediene

    2017-07-01

    The influence of the thickness of a Zinc Oxide (ZnO) transparent conductive oxide (TCO) layer on the performance of the CZTSSe solar cell is shown in detail. In a photovoltaic cell, the thickness of each layer largely influence the performance of the solar cell and optimization of each layer constitutes a complete work. Here, using the Solar Cell Capacitance Simulation (SCAPS) software, we present simulation results obtained in the analyze of the influence of the TCO layer thickness on the performance of a CZTSSe solar cell, starting from performance of a CZTSSe solar cell commercialized in 2014 with an initial efficiency equal to 12.6%. In simulation, the temperature was considered as a functioning parameter and the evolution of tthe performance of the cell for various thickness of the TCO layer when the external temperature changes is simulated and discussed. The best efficiency of the solar cell based in CZTSSe is obtained with a ZnO thickness equal to 50 nm and low temperature. Based on the considered marketed cell, we show a technological possible increase of the global efficiency achieving 13% by optimization of ZnO based TCO layer.

  12. Epitaxially grown zinc-blende structured Mn doped ZnO nanoshell on ZnS nanoparticles

    International Nuclear Information System (INIS)

    Limaye, Mukta V.; Singh, Shashi B.; Date, Sadgopal K.; Gholap, R.S.; Kulkarni, Sulabha K.

    2009-01-01

    Zinc oxide in the bulk as well as in the nanocrystalline form is thermodynamically stable in the wurtzite structure. However, zinc oxide in the zinc-blende structure is more useful than that in the wurtzite structure due to its superior electronic properties as well as possibility of efficient doping. Therefore, zinc oxide shell is grown epitaxially on zinc sulphide core nanoparticles having zinc-blende structure. It is shown that doping of manganese could be achieved in zinc oxide nanoshell with zinc-blende structure

  13. Photoluminescence and lasing properties of ZnO nanorods

    International Nuclear Information System (INIS)

    Lee, Geon Joon; Lee, Young Pak; Min, Sun Ki; Han, Sung Hwan; Lim, Hwan Hong; Cha, Myoung Sik; Kim, Sung Soo; Cheong, Hyeon Sik

    2010-01-01

    In this study, we investigated the structures, photoluminescence (PL), and lasing characteristics of the ZnO nanorods prepared by using chemical bath deposition. The continuous-wave HeCd laser excited PL spectra of the ZnO nanorods exhibited two emission bands, one in the UV region and the other in the visible region. The UV emission band has its peak at 3.25 eV with a bandwidth of 160 meV. However, the PL spectra under 355-nm, 35-ps pulse excitation exhibited a spectrally-narrowed UV emission band with a peak at 3.20 eV and a spectral width of 35 meV. The lasing phenomena were ascribed to the amplified spontaneous emission (ASE) caused by coupling of the microcavity effect of ZnO nanorods and the high-intensity excitation. Above the lasing threshold, the ASE peak intensity exhibited a superlinear dependence on the excitation intensity. For an excitation pulse energy of 3 mJ, the ASE peak intensity was increased by enlarging the length of the ZnO nanorods from 1 μm to 4 μm. In addition, the PL spectrum under 800-nm femtosecond pulse excitation exhibited second harmonic generation, as well as the multiphoton absorption-induced UV emission band. In this research, ZnO nanorods were grown on seed layers by using chemical bath deposition in an aqueous solution of Zn(NO 3 ) 2 and hexamethyltetramine. The seed layers were prepared on conducting glass substrates by dip coating in an aqueous colloidal dispersion containing 50% 70-nm ZnO nanoparticles. Scanning electron microscopy clearly revealed that ZnO nanorods were successfully grown on the seed layers.

  14. ZnO film for application in surface acoustic wave device

    International Nuclear Information System (INIS)

    Du, X Y; Fu, Y Q; Tan, S C; Luo, J K; Flewitt, A J; Maeng, S; Kim, S H; Choi, Y J; Lee, D S; Park, N M; Park, J; Milne, W I

    2007-01-01

    High quality, c-axis oriented zinc oxide (ZnO) thin films were grown on silicon substrate using RF magnetron sputtering. Surface acoustic wave (SAW) devices were fabricated with different thickness of ZnO ranging from 1.2 to 5.5 μmUm and the frequency responses were characterized using a network analyzer. Thick ZnO films produce the strongest transmission and reflection signals from the SAW devices. The SAW propagation velocity is also strongly dependent on ZnO film thickness. The performance of the ZnO SAW devices could be improved with addition of a SiO 2 layer, in name of reflection signal amplitude and phase velocity of Rayleigh wave

  15. Enhancing the Performance of Quantum Dot Light-Emitting Diodes Using Room-Temperature-Processed Ga-Doped ZnO Nanoparticles as the Electron Transport Layer

    KAUST Repository

    Cao, Sheng

    2017-04-19

    Colloidal ZnO nanoparticle (NP) films are recognized as efficient electron transport layers (ETLs) for quantum dot light-emitting diodes (QD-LEDs) with good stability and high efficiency. However, because of the inherently high work function of such films, spontaneous charge transfer occurs at the QD/ZnO interface in such a QD-LED, thus leading to reduced performance. Here, to improve the QD-LED performance, we prepared Ga-doped ZnO NPs with low work functions and tailored band structures via a room-temperature (RT) solution process without the use of bulky organic ligands. We found that the charge transfer at the interface between the CdSe/ZnS QDs and the doped ZnO NPs was significantly weakened because of the incorporated Ga dopants. Remarkably, the as-assembled QD-LEDs, with Ga-doped ZnO NPs as the ETLs, exhibited superior luminances of up to 44 000 cd/m2 and efficiencies of up to 15 cd/A, placing them among the most efficient red-light QD-LEDs ever reported. This discovery provides a new strategy for fabricating high-performance QD-LEDs by using RT-processed Ga-doped ZnO NPs as the ETLs, which could be generalized to improve the efficiency of other optoelectronic devices.

  16. Characterization and growth mechanism of nonpolar and semipolar GaN layers grown on patterned sapphire substrates

    International Nuclear Information System (INIS)

    Okada, Narihito; Tadatomo, Kazuyuki

    2012-01-01

    Nonpolar and semipolar GaN layers with markedly improved crystalline quality can be obtained by selective-area growth from the sapphire sidewalls of patterned sapphire substrates (PSSs). In this paper, we review the crystalline qualities of GaN layers grown on PSSs and their growth mechanism. We grew semipolar {1 1 −2 2} and {1 0 −1 1} GaN layers on r- and n-PSSs. The crystalline qualities of the GaN layers grown on the PSSs were higher than those of GaN layers grown directly on heteroepitaxial substrates. To reveal the growth mechanism of GaN layers grown on PSSs, we also grew various nonpolar and semipolar GaN layers such as m-GaN on a-PSS, {1 1 −2 2} GaN on r-PSS, {1 0 − 1  1} GaN on n-PSS, m-GaN on c-PSS and a-GaN on m-PSS. It was found that the nucleation of GaN on the c-plane-like sapphire sidewall results in selective growth from the sapphire sidewall, and nonpolar or semipolar GaN can be obtained. Finally, we demonstrated a light-emitting diode fabricated on a {1 1 −2 2} GaN layer grown on an r-PSS. (paper)

  17. ZnMgO-ZnO quantum wells embedded in ZnO nanopillars: Towards realisation of nano-LEDs

    Energy Technology Data Exchange (ETDEWEB)

    Bakin, A.; El-Shaer, A.; Mofor, A.C.; Al-Suleiman, M.; Schlenker, E.; Waag, A. [Institute of Semiconductor Technology, Braunschweig Technical University, Hans-Sommer-Str. 66, 38106 Braunschweig (Germany)

    2007-07-01

    ZnO thin films, ZnMgO/ZnO heterostructures and ZnO nanostructures were fabricated using molecular beam epitaxy (MBE), vapour phase transport (VPT) and an aqueous chemical growth approach (ACG). The possibility to employ several fabrication techniques is of special importance for the realization of unique device structures. MBE was implemented for ZnO-based layer and heterostructure growth. Pronounced RHEED oscillations were used for growth control and optimisation, resulting in high quality ZnO and Zn{sub 1-x}Mg{sub x}O epilayers and heterostructures, as well as ZnMgO/ZnO quantum wells on sapphire and SiC substrates. A novel advanced VPT approach is developed and sapphire, SiC, ZnO epitaxial layers, and even plastic and glass were implemented as substrates for ZnO growth. The VPT fabrication of ZnO nanopillars, leading to well aligned, c-axis oriented nanopillars with excellent quality and purity is demonstrated. Successful steps were made towards device fabrication on ZnO basis. The nanopillar fabrication technique is combined with MBE technology: MBE-grown ZnMgO/ZnO quantum well structures were grown on ZnO nanopillars presenting significant progress towards nano-LEDs realization. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Deposition of stress free c-axis oriented LiNbO{sub 3} thin film grown on (002) ZnO coated Si substrate

    Energy Technology Data Exchange (ETDEWEB)

    Shandilya, Swati; Gupta, Vinay [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India); Tomar, Monika [Miranda House, University of Delhi, Delhi 110007 (India)

    2012-05-15

    C-axis oriented lithium niobate thin films have been deposited on Si substrate using RF sputtering technique. A thin buffer layer of c-axis (002) oriented ZnO on Si substrate has been used as a nucleating layer to promote the growth of (006) oriented LiNbO{sub 3} film. The processing gas composition and pressure are found to be very critical in obtaining stress free LiNbO{sub 3} film having desired (006) orientation. The LiNbO{sub 3} films deposited under unique combination of sputtering pressure (10 mTorr) and argon percentage (80%) in reactive gas (Ar + O{sub 2}) composition become almost stress free having lattice parameter (1.3867 A) close to the bulk value. The observed variation in the structural properties and optical phonon modes observed by Raman spectroscopic studies of the oriented LiNbO{sub 3} thin film with stress has been correlated with growth kinetics.

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

    Science.gov (United States)

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

    2016-11-02

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

  20. Active Layer Spin Coating Speed Dependence of Inverted Organic Solar Cell Based on Eosin-Y-Coated ZnO Nanorod Arrays

    Science.gov (United States)

    Ginting, R. T.; Yap, C. C.; Yahaya, M.; Fauzia, V.; Salleh, M. M.

    2013-04-01

    The active layer spin coating speed dependence of the performance of inverted organic solar cells (OSCs) based on Eosin-Y-coated ZnOnanorods has been investigated. An active layer consisted of poly(2-methoxy-5-(2'-ethyl)-hexyloxy-p-phenylenevinylene) (MEH-PPV) as donor and phenyl-c61-butyric acid methyl ester (PCBM) as acceptor was employed, whereas ZnO nanorods were utilized as electron transporting layer. The active layer was deposited on top of Eosin-Y-coated ZnO nanorods with various spin coating speeds (1000-4000 rpm). Inverted OSCs with a structure of FTO/Eosin-Y-coated ZnO nanorods/MEH-PPV:PCBM /Ag were characterized through the current density-voltage (J-V) measurement under illumination intensity of 100 mW/cm2. Based on the investigation, the short circuit current density (Jsc) and the power conversion efficiency (PCE) enhanced significantly, where as fill factor slightly increased with spin coating speed. The two-diode equivalent model was found to fit the experimental J-V curves very well. The optimum PCE of 1.18 ± 0.07% was achieved at the highest spin coating speed of 4000 rpm, as a result of the decrement of diffusion current density (Jdiff), recombination current density (Jrec), and ideality factor, thus further confirms the strong built-in electric field in thinner photoactive layer.

  1. Successful Fabrication of GaN Epitaxial Layer on Non-Catalytically grown Graphene

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Sung Won [Konkuk University, Chungju (Korea, Republic of); Choi, Suk-Ho [Kyung Hee University, Yongin (Korea, Republic of)

    2016-07-15

    Sapphire is widely used as a substrate for the growth of GaN epitaxial layer (EPI), but has several drawbacks such as high cost, large lattice mismatch, non-flexibility, and so on. Here, we first employ graphene directly grown on Si or sapphire substrate as a platform for the growth and lift-off of GaN-light-emitting diode (LED) EPI, useful for not only recycling the substrate but also transferring the GaN-LED EPI to other flexible substrates. Sequential standard processes of nucleation/recrystallization of GaN seeds and deposition of undoped (u-) GaN/AlN buffer layer were done on graphene/substrate before the growth of GaN-LED EPI, accompanied by taping and lift-off of u-GaN/AlN or GaN-LED EPI. This approach can overcome the limitations by the catalytic growth and transfer of graphene, and make the oxygen-plasma treatment of graphene for the growth of GaN EPI unnecessary.

  2. Chemical resistance of thin film materials based on metal oxides grown by atomic layer deposition

    International Nuclear Information System (INIS)

    Sammelselg, Väino; Netšipailo, Ivan; Aidla, Aleks; Tarre, Aivar; Aarik, Lauri; Asari, Jelena; Ritslaid, Peeter; Aarik, Jaan

    2013-01-01

    Etching rate of technologically important metal oxide thin films in hot sulphuric acid was investigated. The films of Al-, Ti-, Cr-, and Ta-oxides studied were grown by atomic layer deposition (ALD) method on silicon substrates from different precursors in large ranges of growth temperatures (80–900 °C) in order to reveal process parameters that allow deposition of coatings with higher chemical resistance. The results obtained demonstrate that application of processes that yield films with lower concentration of residual impurities as well as crystallization of films in thermal ALD processes leads to significant decrease of etching rate. Crystalline films of materials studied showed etching rates down to values of < 5 pm/s. - Highlights: • Etching of atomic layer deposited thin metal oxide films in hot H 2 SO 4 was studied. • Smallest etching rates of < 5 pm/s for TiO 2 , Al 2 O 3 , and Cr 2 O 3 were reached. • Highest etching rate of 2.8 nm/s for Al 2 O 3 was occurred. • Remarkable differences in etching of non- and crystalline films were observed

  3. Ambient Layer-by-Layer ZnO Assembly for Highly Efficient Polymer Bulk Heterojunction Solar Cells

    KAUST Repository

    Eita, Mohamed Samir; El Labban, Abdulrahman; Cruciani, Federico; Usman, Anwar; Beaujuge, Pierre; Mohammed, Omar F.

    2015-01-01

    The use of metal oxide interlayers in polymer solar cells has great potential because metal oxides are abundant, thermally stable, and can be used in fl exible devices. Here, a layer-by-layer (LbL) protocol is reported as a facile, room

  4. Facing-target sputtering deposition of ZnO films with Pt ultra-thin layers for gas-phase photocatalytic application

    International Nuclear Information System (INIS)

    Zhang Zhonghai; Hossain, Md. Faruk.; Arakawa, Takuya; Takahashi, Takakazu

    2010-01-01

    In this paper, various zinc oxide (ZnO) films are deposited by a versatile and effective dc-reactive facing-target sputtering method. The ratios of Ar to O 2 in the mixture gas are varied from 8:2 to 6:4 at a fixed sputtering pressure of 1.0 Pa. X-ray diffraction, spectrophotometer and scanning electron microscope are used to study the crystal structure, optical property and surface morphology of the as-deposited films. The Pt ultra-thin layer, ∼2 nm thick, is deposited on the surface of ZnO film by dc diode sputtering with a mesh mask controlling the coated area. The photocatalytic activity of ZnO films and Pt-ZnO films is evaluated by decomposition of methanol under UV-vis light irradiation. The variation of photocatalytic activity depends on the ratios of Ar to O 2 , which is mainly attributed to the different grain size and carrier mobility. Though the pure ZnO film normally shows a low gas-phase photocatalytic activity, its activity is significantly enhanced by depositing Pt ultra-thin layer.

  5. Improving photoelectrochemical performance on quantum dots co-sensitized TiO{sub 2} nanotube arrays using ZnO energy barrier by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Min [Key Laboratory of Ministry of Education for Advanced Materials in Tropical Island Resources, College of Materials and Chemical Engineering, Hainan University, Haikou 570228 (China); Zeng, Xi [College of Chemistry and Chemical Engineering, Yunnan Normal University, Kunming, 650500 (China); Peng, Xiange; Zhu, Zhuo; Liao, Jianjun; Liu, Kai; Wang, Guizhen [Key Laboratory of Ministry of Education for Advanced Materials in Tropical Island Resources, College of Materials and Chemical Engineering, Hainan University, Haikou 570228 (China); Lin, Shiwei, E-mail: linsw@hainu.edu.cn [Key Laboratory of Ministry of Education for Advanced Materials in Tropical Island Resources, College of Materials and Chemical Engineering, Hainan University, Haikou 570228 (China)

    2016-12-01

    Graphical abstract: - Highlights: • The length of TNTAs has a balance between the charge recombination and the QDs loading. • The introduction of ZnO interlayer by ALD could improve the QDs absorption. • The optimal thickness of ZnO interlayer is 1.5 nm prepared by 10 cycles ALD. - Abstract: PbS and CdS quantum dots (QDs) have been deposited onto TiO{sub 2} nanotube arrays (TNTAs) in turn via a sonication-assisted successive ionic layer adsorption and reaction method. This method could uniformly decorate TNTAs with QDs, avoiding QDs aggregation at the mouth of TiO{sub 2} nanotube. The loading amounts of QDs on TNTAs could be controlled by adjusting the TNTAs length. Under one sun illumination, the QDs co-sensitized TNTAs (TNTAs/QDs) with the length of about 2.4 μm displayed the highest photocurrent of 4.32 mA cm{sup −2}, which is 27 times higher than that of the bare TNTAs. Introduction of a thin ZnO energy barrier by atomic layer deposition (ALD) between the TNTAs and QDs can further improve the photocurrent of TNTAs/QDs. And the TNTAs/QDs with 10 ALD cycles of ZnO interlayer exhibits the highest photocurrent of 5.24 mA cm{sup −2} and best photoconversion efficiency of 4.9%, a more than 20% enhancement over the bare TNTAs/QDs. Such enhanced photoelectrochemical performance may be ascribed to the increased amounts of QDs on the TNTAs due to the introduction of ZnO interlayer. The benefits of ALD layers play a crucial role in development and optimization of high-performance photoelectrodes in the near future.

  6. Improving photoelectrochemical performance on quantum dots co-sensitized TiO_2 nanotube arrays using ZnO energy barrier by atomic layer deposition

    International Nuclear Information System (INIS)

    Zeng, Min; Zeng, Xi; Peng, Xiange; Zhu, Zhuo; Liao, Jianjun; Liu, Kai; Wang, Guizhen; Lin, Shiwei

    2016-01-01

    Graphical abstract: - Highlights: • The length of TNTAs has a balance between the charge recombination and the QDs loading. • The introduction of ZnO interlayer by ALD could improve the QDs absorption. • The optimal thickness of ZnO interlayer is 1.5 nm prepared by 10 cycles ALD. - Abstract: PbS and CdS quantum dots (QDs) have been deposited onto TiO_2 nanotube arrays (TNTAs) in turn via a sonication-assisted successive ionic layer adsorption and reaction method. This method could uniformly decorate TNTAs with QDs, avoiding QDs aggregation at the mouth of TiO_2 nanotube. The loading amounts of QDs on TNTAs could be controlled by adjusting the TNTAs length. Under one sun illumination, the QDs co-sensitized TNTAs (TNTAs/QDs) with the length of about 2.4 μm displayed the highest photocurrent of 4.32 mA cm"−"2, which is 27 times higher than that of the bare TNTAs. Introduction of a thin ZnO energy barrier by atomic layer deposition (ALD) between the TNTAs and QDs can further improve the photocurrent of TNTAs/QDs. And the TNTAs/QDs with 10 ALD cycles of ZnO interlayer exhibits the highest photocurrent of 5.24 mA cm"−"2 and best photoconversion efficiency of 4.9%, a more than 20% enhancement over the bare TNTAs/QDs. Such enhanced photoelectrochemical performance may be ascribed to the increased amounts of QDs on the TNTAs due to the introduction of ZnO interlayer. The benefits of ALD layers play a crucial role in development and optimization of high-performance photoelectrodes in the near future.

  7. Composition, structure and electrical properties of alumina barrier layers grown in fluoride-containing oxalic acid solutions

    Energy Technology Data Exchange (ETDEWEB)

    Jagminas, A. [Institute of Chemistry, A. Gostauto 9, LT-01108 Vilnius (Lithuania)], E-mail: jagmin@ktl.mii.lt; Vrublevsky, I. [Department of Microelectricals, Belarusian State University of Informatics and Radioelectricals, 6 Brovka Street, Minsk 220013 (Belarus); Kuzmarskyte, J.; Jasulaitiene, V. [Institute of Chemistry, A. Gostauto 9, LT-01108 Vilnius (Lithuania)

    2008-04-15

    The composition, structure and electrical properties of alumina barrier layers grown by anodic oxidation in F{sup -}-containing (FC) and F{sup -}-free (FF) oxalic acid solutions were studied using the re-anodizing/dissolution technique, Fourier-transformed infrared and X-ray photoelectron spectroscopy. These results confirmed formation in FC anodizing solutions of films structurally different from ones grown in FF oxalic acid baths. It was found that the barrier layer of FC alumina films is composed of two layers differing in the dissolution rate. These differences are related to the formation in the FC electrolyte of a barrier layer composed of a more microporous outer part and a thin, non-porous and non-scalloped inner part consisting of aluminum oxide and aluminum fluoride.

  8. High-Brightness Blue Light-Emitting Diodes Enabled by a Directly Grown Graphene Buffer Layer.

    Science.gov (United States)

    Chen, Zhaolong; Zhang, Xiang; Dou, Zhipeng; Wei, Tongbo; Liu, Zhiqiang; Qi, Yue; Ci, Haina; Wang, Yunyu; Li, Yang; Chang, Hongliang; Yan, Jianchang; Yang, Shenyuan; Zhang, Yanfeng; Wang, Junxi; Gao, Peng; Li, Jinmin; Liu, Zhongfan

    2018-06-08

    Single-crystalline GaN-based light-emitting diodes (LEDs) with high efficiency and long lifetime are the most promising solid-state lighting source compared with conventional incandescent and fluorescent lamps. However, the lattice and thermal mismatch between GaN and sapphire substrate always induces high stress and high density of dislocations and thus degrades the performance of LEDs. Here, the growth of high-quality GaN with low stress and a low density of dislocations on graphene (Gr) buffered sapphire substrate is reported for high-brightness blue LEDs. Gr films are directly grown on sapphire substrate to avoid the tedious transfer process and GaN is grown by metal-organic chemical vapor deposition (MOCVD). The introduced Gr buffer layer greatly releases biaxial stress and reduces the density of dislocations in GaN film and In x Ga 1- x N/GaN multiple quantum well structures. The as-fabricated LED devices therefore deliver much higher light output power compared to that on a bare sapphire substrate, which even outperforms the mature process derived counterpart. The GaN growth on Gr buffered sapphire only requires one-step growth, which largely shortens the MOCVD growth time. This facile strategy may pave a new way for applications of Gr films and bring several disruptive technologies for epitaxial growth of GaN film and its applications in high-brightness LEDs. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Adsorption properties of Mg-Al layered double hydroxides thin films grown by laser based techniques

    Energy Technology Data Exchange (ETDEWEB)

    Matei, A., E-mail: andreeapurice@nipne.ro [National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Str., 77125 Bucharest, Magurele (Romania); Birjega, R.; Vlad, A.; Filipescu, M.; Nedelcea, A.; Luculescu, C. [National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Str., 77125 Bucharest, Magurele (Romania); Zavoianu, R.; Pavel, O.D. [University of Bucharest, Faculty of Chemistry, Department of Chemical Technology and Catalysis, 4-12 Regina Elisabeta Bd., Bucharest (Romania); Dinescu, M. [National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Str., 77125 Bucharest, Magurele (Romania)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer Laser techniques MAPLE and PLD can successfully be used to produce LDHs thin films. Black-Right-Pointing-Pointer Hydration treatments of the PLD and MAPLE deposited films lead to the LDH reconstruction effect. Black-Right-Pointing-Pointer The Ni retention from aqueous solution occurs in the films via a dissolution-reconstruction mechanism. Black-Right-Pointing-Pointer The films are suitable for applications in remediation of contaminated drinking water or waste waters. - Abstract: Powdered layered double hydroxides (LDHs) have been widely studied due to their applications as catalysts, anionic exchangers or host materials for inorganic and/or organic molecules. Assembling nano-sized LDHs onto flat solid substrates forming thin films is an expanding area of research due to the prospects of novel applications as sensors, corrosion-resistant coatings, components in optical and magnetic devices. Continuous and adherent thin films were grown by laser techniques (pulsed laser deposition - PLD and matrix assisted pulsed laser evaporation - MAPLE) starting from targets of Mg-Al LDHs. The capacity of the grown thin films to retain a metal (Ni) from contaminated water has been also explored. The thin films were immersed in an Ni(NO{sub 3}){sub 2} aqueous solutions with Ni concentrations of 10{sup -3}% (w/w) (1 g/L) and 10{sup -4}% (w/w) (0.1 g/L), respectively. X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDX) were the techniques used to characterize the prepared materials.

  10. Carrier confinement in Ge/Si quantum dots grown with an intermediate ultrathin oxide layer

    Science.gov (United States)

    Kuryliuk, V.; Korotchenkov, O.; Cantarero, A.

    2012-02-01

    We present computational results for strain effects on charge carrier confinement in GexSi1-x quantum dots (QDs) grown on an oxidized Si surface. The strain and free carrier probability density distributions are obtained using the continuum elasticity theory and the effective-mass approximation implemented by a finite-element modeling scheme. Using realistic parameters and conditions for hemisphere and pyramid QDs, it is pointed out that an uncapped hemisphere dot deposited on the Si surface with an intermediate ultrathin oxide layer offers advantageous electron-hole separation distances with respect to a square-based pyramid grown directly on Si. The enhanced separation is associated with a larger electron localization depth in the Si substrate for uncapped hemisphere dots. Thus, for dot diameters smaller than 15-20 nm and surface density of the dots (nQD) ranging from about 1010 to 1012 cm-2, the localization depth may be enhanced from about 8 nm for a pyramid to 38 nm for a hemisphere dot. We find that the effect in a hemisphere dot is very sensitive to the dot density and size, whereas the localization depth is not significantly affected by the variation of the Ge fraction x in GexSi1-x and the aspect ratio of the dot. We also calculate the effect of the fixed oxide charge (Qox) with densities ranging from 10-9 to 10-7 C/cm2 for 10-Ωcm p-type Si wafers on the carrier confinement. Although the confinement potential can be strongly perturbed by the charge at nQD less than ≈4×1011 cm-2, it is not very sensitive to the value of Qox at higher nQD. Since, to our knowledge, there are no data on carrier confinement for Ge QDs deposited on oxidized Si surfaces, these results might be applicable to functional devices utilizing separated electrons and holes such as photovoltaic devices, spin transistors, and quantum computing components. The use of hemisphere QDs placed on oxidized Si rather than pyramid dots grown on bare Si may help to confine charge carriers deeper

  11. Flexible Al-doped ZnO films grown on PET substrates using linear facing target sputtering for flexible OLEDs

    International Nuclear Information System (INIS)

    Jeong, Jin-A; Shin, Hyun-Su; Choi, Kwang-Hyuk; Kim, Han-Ki

    2010-01-01

    We report the characteristics of flexible Al-doped zinc oxide (AZO) films prepared by a plasma damage-free linear facing target sputtering (LFTS) system on PET substrates for use as a flexible transparent conducting electrode in flexible organic light-emitting diodes (OLEDs). The electrical, optical and structural properties of LFTS-grown flexible AZO electrodes were investigated as a function of dc power. We obtained a flexible AZO film with a sheet resistance of 39 Ω/□ and an average transmittance of 84.86% in the visible range although it was sputtered at room temperature without activation of the Al dopant. Due to the effective confinement of the high-density plasma between the facing AZO targets, the AZO film was deposited on the PET substrate without plasma damage and substrate heating caused by bombardment of energy particles. Moreover, the flexible OLED fabricated on the AZO/PET substrate showed performance similar to the OLED fabricated on a ITO/PET substrate in spite of a lower work function. This indicates that LFTS is a promising plasma damage-free and low-temperature sputtering technique for deposition of flexible and indium-free AZO electrodes for use in cost-efficient flexible OLEDs.

  12. Thermally oxidized formation of new Ge dots over as-grown Ge dots in the Si capping layer

    International Nuclear Information System (INIS)

    Nie Tianxiao; Lin Jinhui; Shao Yuanmin; Wu Yueqin; Yang Xinju; Fan Yongliang; Jiang Zuimin; Chen Zhigang; Zou Jin

    2011-01-01

    A Si-capped Ge quantum dot sample was self-assembly grown via Stranski-Krastanov mode in a molecular beam epitaxy system with the Si capping layer deposited at 300 deg. C. After annealing the sample in an oxygen atmosphere at 1000 deg. C, a structure, namely two layers of quantum dots, was formed with the newly formed Ge-rich quantum dots embedded in the oxidized matrix with the position accurately located upon the as-grown quantum dots. It has been found that the formation of such nanostructures strongly depends upon the growth temperature and oxygen atmosphere. A growth mechanism was proposed to explain the formation of the nanostructure based on the Ge diffusion from the as-grown quantum dots, Ge segregation from the growing oxide, and subsequent migration/agglomeration.

  13. Layer-controlled large area MoS{sub 2} layers grown on mica substrate for surface-enhanced Raman scattering

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Y.Y.; Yang, C. [College of Physics and Electronics, Shandong Normal University, Jinan 250014 (China); Jiang, S.Z. [College of Physics and Electronics, Shandong Normal University, Jinan 250014 (China); State Key Lab of Crystal Materials Shandong University, Jinan 250100 (China); Man, B.Y., E-mail: byman@sdnu.edu.cn [College of Physics and Electronics, Shandong Normal University, Jinan 250014 (China); Liu, M.; Chen, C.S.; Zhang, C.; Sun, Z.C.; Qiu, H.W. [College of Physics and Electronics, Shandong Normal University, Jinan 250014 (China); Li, H.S. [Department of Radiation Oncology, Key Laboratory of Radiation Oncology of Shandong Province, Shandong Cancer Hospital and Institute, Jinan 250117 (China); Feng, D.J. [College of Information Science and Engineering, Shandong University, Jinan 250100 (China); Zhang, J.X. [College of Physics and Electronics, Shandong Normal University, Jinan 250014 (China)

    2015-12-01

    Highlights: • Layer-controlled large-area and continuous MoS{sub 2} atomic layers were obtained on mica substrate by thermally decomposing ammonium thiomolybdate at relatively low temperature. • The as-grown MoS{sub 2}/mica substrate was demonstrated to be suitable as a substrate for enhancing Raman signals without any modification and we even collected Raman signals of R6G as low as 10{sup −7} M. • Using the Raman peak of R6G at 1361 cm{sup −1} as a signature, Raman intensity showed an approximately linear increase with the increasing of the logarithm of R6G concentrations. - Abstract: Molybdenum disulfide has recently raised more and more interest due to its layer-related properties and potential applications in optoelectronics and electronics. Here, layer-controlled large-area and continuous MoS{sub 2} atomic layers were obtained on mica substrate by thermally decomposing ammonium thiomolybdate. The obtained MoS{sub 2} film is three layers uniformly. Because of the small lattice mismatch between MoS{sub 2} and mica, the epitaxial MoS{sub 2} film is well grown on the substrate. The as-grown MoS{sub 2}/mica substrate is demonstrated to be suitable as a substrate for enhancing Raman signals of adsorbed molecules without any modification, which even can compare with graphene and will expand the application of MoS{sub 2} to microanalysis.

  14. XRD Investigation of the relaxation of InAsP layers grown by CBE on (100) InP

    NARCIS (Netherlands)

    Marschner, T.H.; Leijs, M.R.; Vonk, H.; Wolter, J.H.

    1998-01-01

    We present X-ray diffraction (XRD) investigations of the influence of the substrate off-orientation on the relaxation of InAsP layers grown on InP by chemical beam epitaxy (CBE). Our measurements show that with beginning relaxation the As-concentration increases drastically and stays constant if the

  15. Low temperature step-graded InAlAs/GaAs metamorphic buffer layers grown by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Shang, X Z; Wu, S D; Liu, C; Wang, W X; Guo, L W; Huang, Q; Zhou, J M

    2006-01-01

    Low-temperature step-graded InAlAs metamorphic buffer layers on GaAs substrate grown by molecular beam epitaxy were investigated. The strain relaxation and the composition of the top InAlAs layer were determined by high-resolution triple-axis x-ray diffraction measurements, which show that the top InAlAs layer is nearly fully relaxed. Surface morphology was observed by reflection high-energy electron diffraction pattern and atomic force microscopy. Under a selected range of growth parameters, the root mean square surface roughness of the sample grown at 380 deg. C is 0.802 nm, which has the smallest value compared with those of other samples. Furthermore, The ω-2θ and ω scans of the triple-axis x-ray diffraction, and photoluminescence show the sample grown at 380 deg. C has better crystalline quality. With decreasing As overpressure at this growth temperature, crystalline quality became poor and could not maintain two dimensional growth with increasing overpressure. The carrier concentrations and Hall mobilities of the InAlAs/ InGaAs/GaAs MM-HEMT structure on low-temperature step-graded InAlAs metamorphic buffer layers grown in optimized conditions are high enough to make devices

  16. Zno Micro/Nanostructures Grown on Sapphire Substrates Using Low-Temperature Vapor-Trapped Thermal Chemical Vapor Deposition: Structural and Optical Properties

    Directory of Open Access Journals (Sweden)

    Po-Sheng Hu

    2017-12-01

    Full Text Available In this research, the Zn(C5H7O22·xH2O-based growth of ZnO micro/nanostructures in a low temperature, vapor-trapped chemical vapor deposition system was attempted to optimize structural and optical properties for potential biomedical applications. By trapping in-flow gas molecules and Zinc vapor inside a chamber tube by partially obstructing a chamber outlet, a high pressure condition can be achieved, and this experimental setup has the advantages of ease of synthesis, being a low temperature process, and cost effectiveness. Empirically, the growth process proceeded under a chamber condition of an atmospheric pressure of 730 torr, a controlled volume flow rate of input gas, N2/O2, of 500/500 Standard Cubic Centimeters per Minute (SCCM, and a designated oven temperature of 500 °C. Specifically, the dependence of structural and optical properties of the structures on growth duration and spatially dependent temperature were investigated utilizing scanning electron microscopy, X-ray diffraction (XRD, photoluminescence (PL, and ultraviolet-visible transmission spectroscopy. The experimental results indicate that the grown thin film observed with hexagonal structures and higher structural uniformity enables more prominent structural and optical signatures. XRD spectra present the dominant peaks along crystal planes of (002 and (101 as the main direction of crystallization. In addition, while the structures excited with laser wavelength of 325 nm emit a signature radiation around 380 nm, an ultraviolet lamp with a wavelength of 254 nm revealed distinctive photoluminescence peaks at 363.96 nm and 403.52 nm, elucidating different degrees of structural correlation as functions of growth duration and the spatial gradient of temperature. Transmittance spectra of the structures illustrate typical variation in the wavelength range of 200 nm to 400 nm, and its structural correlation is less significant when compared with PL.

  17. Structural and optical properties of nano-structured tungsten-doped ZnO thin films grown by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Ngom, B.D. [African Laser Centre, CSIR campus, P.O. Box 395, Pretoria (South Africa); Groupes de Laboratoires de physique des Solides et Sciences des Materiaux, Faculte des sciences et Techniques Universite Cheikh Anta Diop de Dakar (UCAD), B.P. 25114 Dakar-Fann Dakar (Senegal); NANO-Sciences Laboratories, Materials Research Group, iThemba LABS, National Research Foundation (South Africa)], E-mail: bdngom@tlabs.ac.za; Mpahane, T. [NANO-Sciences Laboratories, Materials Research Group, iThemba LABS, National Research Foundation (South Africa); Manyala, N. [Department of Physics and Electronics National University of Lesotho (Lesotho); Nemraoui, O. [NANO-Sciences Laboratories, Materials Research Group, iThemba LABS, National Research Foundation (South Africa); Buttner, U. [Engineering Department, University of Stellenbosch (South Africa); Kana, J.B. [Department of Physique University of Yaounde 1 (Cameroon); Fasasi, A.Y. [Centre for Energy Research and Development, Obafemi Awolowo University, Ile-Ife, Osun State (Nigeria); Maaza, M. [African Laser Centre, CSIR campus, P.O. Box 395, Pretoria (South Africa); NANO-Sciences Laboratories, Materials Research Group, iThemba LABS, National Research Foundation (South Africa); Beye, A.C. [African Laser Centre, CSIR campus, P.O. Box 395, Pretoria (South Africa); Groupes de Laboratoires de physique des Solides et Sciences des Materiaux, Faculte des sciences et Techniques Universite Cheikh Anta Diop de Dakar (UCAD), B.P. 25114 Dakar-Fann Dakar (Senegal)

    2009-01-15

    Novel highly c-oriented tungsten-doped zinc oxide (WZO) thin films with 1 wt% were grown by pulsed laser deposition (PLD) technique on corning 1737F glass substrate. The effects of laser energy on the structural, morphological as well as optical transmission properties of the films were studied. The films were highly transparent with average transmittance exceeding 87% in the wavelength region lying between 400 and 2500 nm. X-ray diffraction analysis (XRD) results indicated that the WZO films had c-axis preferred orientation with wurtzite structure. Film thickness and the full width at half maximum (FWHM) of the (0 0 2) peaks of the films were found to be dependent on laser fluence. The composition determined through Rutherford backscattering spectroscopy (RBS) appeared to be independent of the laser fluence. By assuming a direct band gap transition, the band gap values of 3.36, 3.34 and 3.31 eV were obtained for corresponding laser fluence of 1, 1.7 and 2.7 J cm{sup -2}, respectively. Compared with the reported undoped ZnO band gap value of 3.37 eV, it is conjectured that the observed low band gap values obtained in this study may be attributable to tungsten incorporation in the films as well as the increase in laser fluence. The high transparency makes the films useful as optical windows while the high band gap values support the idea that the films could be good candidates for optoelectronic applications.

  18. Numerical simulation of solar cells besed CZTS buffer layer (ZnO 1 ...

    African Journals Online (AJOL)

    Cds buffer layer has many advantages such as large bandgap, and the carrier density. Otherwise, the presence of cadmium is an inconvenient. Research work, are shifted on the possibility of replacing CdS by a buffer layer devoid of cadmium. This manuscript presents the numerical study, using SCAPS-1D program, the ...

  19. Influence of Drying Temperature on the Structural, Optical, and Electrical Properties of Layer-by-Layer ZnO Nanoparticles Seeded Catalyst

    Directory of Open Access Journals (Sweden)

    S. S. Shariffudin

    2012-01-01

    Full Text Available Layer-by-layer zinc oxide (ZnO nanoparticles have been prepared using sol-gel spin coating technique. The films were dried at different temperature from 100°C to 300°C to study its effect to the surface morphology, optical and electrical properties of the films. Film dried at 200°C shows the highest (0 0 2 peak of X-ray diffraction pattern which is due to complete decomposition of zinc acetate and complete vaporization of the stabilizer and solvent. It was found that the grain size increased with the increased of drying temperature from 100 to 200°C, but for films dried at above 200°C, the grain size decreased. Photoluminescence measurements show a sharp ultraviolet emission centred at 380 nm and a very low intensity visible emission. Blue visible emission was detected for sample dried at temperature below 200°C, while for films dried above 250°C, the visible emission is red shifted. The films were transparent in the visible range from 400 to 800 nm with average transmittance of above 85%. Linear I-V characteristics were shown confirming the ohmic behaviour of the gold contacts to the films. A minimum resistivity was given by 5.08 Ω · cm for the film dried at 300°C.

  20. Doping effect on SILAR synthesized crystalline nanostructured Cu-doped ZnO thin films grown on indium tin oxide (ITO) coated glass substrates and its characterization

    Science.gov (United States)

    Dhaygude, H. D.; Shinde, S. K.; Velhal, Ninad B.; Takale, M. V.; Fulari, V. J.

    2016-08-01

    In the present study, a novel chemical route is used to synthesize the undoped and Cu-doped ZnO thin films in aqueous solution by successive ionic layer adsorption and reaction (SILAR) method. The synthesized thin films are characterized by x-ray diffractometer (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive x-ray analysis (EDAX), contact angle goniometer and UV-Vis spectroscopic techniques. XRD study shows that the prepared films are polycrystalline in nature with hexagonal crystal structure. The change in morphology for different doping is observed in the studies of FE-SEM. EDAX spectrum shows that the thin films consist of zinc, copper and oxygen elements. Contact angle goniometer is used to measure the contact angle between a liquid and a solid interface and after detection, the nature of the films is initiated from hydrophobic to hydrophilic. The optical band gap energy for direct allowed transition ranging between 1.60-2.91 eV is observed.

  1. Effect of Al-doped on physical properties of ZnO Thin films grown by spray pyrolysis on SnO2: F/glass

    Directory of Open Access Journals (Sweden)

    Castagné M.

    2012-06-01

    Full Text Available Transparent conducting thin films of aluminum-doped zinc oxide (ZnO:Al have been deposited on SnO2:F/glass by the chemical spray technique, starting from zinc acetate (CH3CO22Zn.2H2O and aluminum chloride AlCl3. The effect of changing the aluminum-to-zinc ratio y from 0 to 3 at.%, has been thoroughly investigated. It was found that the optical and electrical properties of Al doped ZnO films improved with the addition of aluminum in the spray solution until y=2%. At this Al doping percentage, the thin layers have a resistivity equal to 4.1 × 10−4 Ω.cm and a transmittance of about 90 % in the region [600-1000] nm. XRD patterns confirm that the films have polycristalline nature and a wurtzite (hexagonal structure which characterized with (100, (002 and (101 principal orientations. The undoped films have (002 as the preferred orientation but Al doped ones have (101 as the preferred orientation. Beyond y= 1%, peak intensities decrease considerably.

  2. Nanomechanical mapping of graphene layers and interfaces in suspended graphene nanostructures grown via carbon diffusion

    Energy Technology Data Exchange (ETDEWEB)

    Robinson, B.J. [Department of Physics, Lancaster University, Lancaster LA1 4YB (United Kingdom); Rabot, C. [CEA-LETI-Minatec Campus, 17 rue des Martyrs, 38054 Grenoble Cedex 09 (France); Mazzocco, R. [Department of Physics, Lancaster University, Lancaster LA1 4YB (United Kingdom); Delamoreanu, A. [Microelectronics Technology Laboratory (LTM), Joseph Fourier University, French National Research Center (CNRS), 17 Avenue des Martyrs, 38054 Grenoble Cedex 9 (France); Zenasni, A. [CEA-LETI-Minatec Campus, 17 rue des Martyrs, 38054 Grenoble Cedex 09 (France); Kolosov, O.V., E-mail: o.kolosov@lancaster.ac.uk [Department of Physics, Lancaster University, Lancaster LA1 4YB (United Kingdom)

    2014-01-01

    Graphene's remarkable mechanical, electronic and thermal properties are strongly determined by both the mechanism of its growth and its interaction with the underlying substrate. Evidently, in order to explore the fundamentals of these mechanisms, efficient nanoscale methods that enable observation of features hidden underneath the immediate surface are needed. In this paper we use nanomechanical mapping via ultrasonic force microscopy that employs MHz frequency range ultrasonic vibrations and allows the observation of surface composition and subsurface interfaces with nanoscale resolution, to elucidate the morphology of few layer graphene (FLG) films produced via a recently reported method of carbon diffusion growth (CDG) on platinum-metal based substrate. CDG is known to result in FLG suspended over large areas, which could be of high importance for graphene transfer and applications where a standalone graphene film is required. This study directly reveals the detailed mechanism of CDG three-dimensional growth and FLG film detachment, directly linking the level of graphene decoupling with variations of the substrate temperature during the annealing phase of growth. We also show that graphene initially and preferentially decouples at the substrate grain boundaries, likely due to its negative expansion coefficient at cooling, forming characteristic “nano-domes” at the intersections of the grain boundaries. Furthermore, quantitative nanomechanical mapping of flexural stiffness of suspended FLG “nano-domes” using kHz frequency range force modulation microscopy uncovers the progression of “nano-dome” stiffness from single to bi-modal distribution as CDG growth progresses, suggesting growth instability at advanced CDG stages. - Highlights: • Exploring growth and film-substrate decoupling in carbon diffusion grown graphene • Nanomechanical mapping of few layer graphene and graphene–substrate interfaces • Quantitative stiffness mapping of

  3. Raman scattering from epitaxial HfN layers grown on MgO(001)

    International Nuclear Information System (INIS)

    Stoehr, M.; Seo, H.-S.; Petrov, I.; Greene, J.E.

    2006-01-01

    Stoichiometric single-crystal HfN layers grown on MgO(001) are analyzed by Raman spectroscopy. Second-order Raman scattering predominates, but first-order modes in the acoustic and optical ranges are also visible. The latter indicates that the O h symmetry of NaCl-structure HfN is broken. The large mass difference between Hf and N leads to a correspondingly large separation, 250 cm -1 , between the first-order acoustic and optical bands. Within this gap, four Raman lines are clearly observed. The first three are the second-order transverse acoustic mode (240 cm -1 ), the sum of the first-order transverse and longitudinal acoustic modes (280 cm -1 ), and the second-order longitudinal acoustic mode (325 cm -1 ). The fourth line at 380 cm -1 is identified as the difference between the first-order optical and acoustic modes. The observed first-order Raman scattering, as well as the width of the gap between the first-order acoustic and optical modes, is in good agreement with previously calculated HfN phonon density of states

  4. X-ray and scanning electron microscopic investigation of porous silicon and silicon epitaxial layers grown on porous silicon

    International Nuclear Information System (INIS)

    Wierzchowski, W.; Pawlowska, M.; Nossarzewska-Orlowska, E.; Brzozowski, A.; Wieteska, K.; Graeff, W.

    1998-01-01

    The 1 to 5 μm thick layers of porous silicon and epitaxial layers grown on porous silicon were studied by means of X-ray diffraction methods, realised with a wide use of synchrotron source and scanning microscopy. The results of x-ray investigation pointed the difference of lateral periodicity between the porous layer and the substrate. It was also found that the deposition of epitaxial layer considerably reduced the coherence of porous fragments. A number of interface phenomena was also observed in section and plane wave topographs. The scanning electron microscopic investigation of cleavage faces enabled direct evaluation of porous layer thickness and revealed some details of their morphology. The scanning observation of etched surfaces of epitaxial layers deposited on porous silicon revealed dislocations and other defects not reasonable in the X-ray topographs. (author)

  5. Fabrication of undoped ZnO thin film via photosensitive sol–gel method and its applications for an electron transport layer of organic solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Luong, Chi Hieu [Department of Materials Science and Engineering and Graduate School of Energy Science and Technology, Chungnam National University, Yuseong-gu, Daejeon 305-764 (Korea, Republic of); Kim, Sarah [Central Research Division, LG Chem., Yuseong-gu, Daejeon 305-738 (Korea, Republic of); Surabhi, Srivathsava; Vo, Thanh Son; Lee, Kyung-Min; Yoon, Soon-Gil [Department of Materials Science and Engineering and Graduate School of Energy Science and Technology, Chungnam National University, Yuseong-gu, Daejeon 305-764 (Korea, Republic of); Jeong, Jun-Ho [Nanomechanical Systems Research Division, Korea Institute of Machinery and Materials, Yuseong-gu, Daejeon 305-343 (Korea, Republic of); Choi, Jun-Hyuk, E-mail: junhyuk@kimm.re.kr [Nanomechanical Systems Research Division, Korea Institute of Machinery and Materials, Yuseong-gu, Daejeon 305-343 (Korea, Republic of); Jeong, Jong-Ryul, E-mail: jrjeong@cnu.ac.kr [Department of Materials Science and Engineering and Graduate School of Energy Science and Technology, Chungnam National University, Yuseong-gu, Daejeon 305-764 (Korea, Republic of)

    2015-10-01

    Highlights: • Investigated the effect of the interfacial ZnO for ETL synthesized by photochemical reaction using photosensitive 2-nitrobenzaldehyde on the inverted P3HT:PCBM OSC. • The abrupt increase of grain size and surface roughness was observed as increasing the annealing temperature above 350 °C. • The sheet resistance abruptly decreased with increasing the annealing temperature above 350 °C. • Increase of surface roughness caused by the high annealing temperature could be detrimental to the OSCs characteristics due to a high contact resistance and a large leakage current. - Abstract: We have investigated ZnO thin films prepared via photochemical reaction as the electron transport layer (ETL) of inverted organic solar cells (OSCs). Morphological and electrical properties of the ZnO thin films prepared by the photosensitive ZnO sol were studied according to the annealing temperature and their effects on the performance of the inverted poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PCBM) OSCs was characterized. It was found that the optimal annealing temperature of the ZnO thin films was 330 °C, and that devices with the ZnO ETL annealed at this temperature exhibited the largest short-circuit current density (J{sub sc}) of 9.39 mA/cm{sup 2}, as well as the highest power conversion efficiency (PCE) of 2.31%, which can be attributed to enhanced electron transport and interfacial properties. Devices containing ZnO films formed at optimal annealing condition exhibited an open circuit voltage (V{sub oc}) of 0.60 V and a fill factor (FF) of 41.0%. However, further increase of the annealing temperature led to degradation of the device performance, despite further improvements in electrical properties. We have found that marked increase in the surface roughness of the ZnO films occurred at temperatures above 350 °C which could be detrimental to the OSCs characteristics due to a high contact resistance and a large leakage current.

  6. Effect of different coating layer on the topography and optical properties of ZnO nanostructured

    Science.gov (United States)

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

    2018-05-01

    Magnesium (Mg) and aluminum (Al) co-doped zinc oxide (MAZO) thin films were synthesized on glass substrate by sol-gel spin coating method. MAZO thin films were prepared at different coating layers range from 1 to 9. Atomic Force Microscopy (AFM) was used to investigate the topography of the thin films. According to the AFM results, Root Means Square (RMS) of MAZO thin films was increased from 0.747 to 6.545 nm, with increase of number coating layer from 1 to 9, respectively. The results shown the variation on structural and topography properties of MAZO seed film when it's deposited at different coating layers on glass substrate. The optical properties was analyzed using UV-Vis spectroscopy. The obtained results show that the transmittance spectra was increased as thin films coating layer increases.

  7. Hydrothermal synthesis of highly crystalline ZnO nanorod arrays: Dependence of morphology and alignment on growth conditions

    Energy Technology Data Exchange (ETDEWEB)

    Azzez, Shrook A., E-mail: shurouq44@yahoo.com [Institutes of Nano-Optoelectronic Research and Technology Laboratory (INOR), Ministry of Science and Technology, Baghdad (Iraq); Hassan, Z.; Alimanesh, M.; Rasheed, Hiba S.; Sabah, Fayroz A.; Abdulateef, Sinan A. [Institutes of Nano-Optoelectronic Research and Technology Laboratory (INOR), Ministry of Science and Technology, Baghdad (Iraq); Hassan, J. J. [Department of Physics, College of Science, University of Basrah, Basrah (Iraq)

    2016-07-06

    Highly oriented zinc oxide nanorod were successfully grown on seeded p-type silicon substrate by hydrothermal methode. The morphology and the crystallinty of ZnO c-axis (002) arrays were systematically studied using field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) methods. The effect of seed layer pre-annealing on nanorods properties was explained according to the nucleation site of ZnO nanoparticles on silicon substrate. In addition, the variation of the equal molarity of zinc nitrate hexahydrate and hexamine concentrations in the reaction vessel play a crucial role related to the ZnO nanorods.

  8. Passivation of ZnO Nanowire Guests and 3D Inverse Opal Host Photoanodes for Dye-Sensitized Solar Cells

    KAUST Repository

    Labouchere, Philippe

    2014-04-23

    A hierarchical host-guest nanostructured photoanode is reported for dye-sensitized solar cells. It is composed of ZnO nanowires grown in situ into the macropores of a 3D ZnO inverse opal structure, which acts both as a seed layer and as a conductive backbone host. Using a combination of self-assembly, hydrothermal or electrodeposition of single crystalline ZnO nanowires and TiO2 passivation, a novel photoanode with scattering capability for optimal light harvesting is fabricated. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Characterization of nanostructures of ZnO and ZnMnO films deposited by successive ionic layer adsorption and reaction method

    International Nuclear Information System (INIS)

    Jimenez-Garcia, F.N.; Espinosa-Arbelaez, D.G.; Vargas-Hernandez, C.; Real, A. del; Rodriguez-Garcia, M.E.

    2011-01-01

    ZnO and ZnMnO thin films were obtained by the successive ionic layer adsorption and reaction (SILAR) method. All thin films were deposited on glass microscope slide. A precursor solution of 0.1 M of ZnCl 2 complexed with ammonium hydroxide and water close to boiling point (92 deg. C) as a second solution was used for the ZnO films. An uncomplexed bath comprised of 0.1 M ZnCl 2 , 0.1 M MnCl 2, and a second solution of 0.1 ml of NH 4 OH with water close to boiling point was used for the ZnMnO films. The film samples were deposited by the SILAR method and annealed at 200 deg. C for 15 min. These samples were characterized using X-Ray Diffraction (XRD), Scanning Electron Microscopy with Energy Dispersive Spectroscopy (EDS), and Atomic Force Microscope. Atomic absorption was used to determine quantitatively the amount of Mn incorporated into the films. According to the XRD patterns these films were polycrystalline with wurtzite hexagonal structure. The morphology of the ZnO films constituted by rice-like and flower-like structures changed significantly to nanosheet structures with the Mn incorporation. The Mn inclusion in a ZnO structure was less than 4% according to the results from EDS, XRD, and atomic absorption.

  10. Characterization of nanostructures of ZnO and ZnMnO films deposited by successive ionic layer adsorption and reaction method

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez-Garcia, F.N. [Departamento de Fisica y Matematicas, Universidad Autonoma de Manizales, Antigua Estacion del Ferrocarril, Manizales, Caldas (Colombia); Departamento de Fisica y Quimica, Universidad Nacional de Colombia, Sede Manizales, Campus la Nubia, Manizales, Caldas (Colombia); Espinosa-Arbelaez, D.G. [Departamento de Nanotecnologia, Centro de Fisica Aplicada y Tecnologia Avanzada, Universidad Nacional Autonoma de Mexico, Blv. Juriquilla 3001, Juriquilla, Queretaro, C.P. 76230 (Mexico); Posgrado en Ciencia e Ingenieria Materiales, Instituto de Investigacion en Materiales, Universidad Nacional Autonoma de Mexico, Mexico DF (Mexico); Vargas-Hernandez, C. [Departamento de Fisica y Quimica, Universidad Nacional de Colombia, Sede Manizales, Campus la Nubia, Manizales, Caldas (Colombia); Real, A. del [Departamento de Nanotecnologia, Centro de Fisica Aplicada y Tecnologia Avanzada, Universidad Nacional Autonoma de Mexico, Blv. Juriquilla 3001, Juriquilla, Queretaro, C.P. 76230 (Mexico); Rodriguez-Garcia, M.E., E-mail: marioga@fata.unam.mx [Departamento de Nanotecnologia, Centro de Fisica Aplicada y Tecnologia Avanzada, Universidad Nacional Autonoma de Mexico, Blv. Juriquilla 3001, Juriquilla, Queretaro, C.P. 76230 (Mexico)

    2011-09-01

    ZnO and ZnMnO thin films were obtained by the successive ionic layer adsorption and reaction (SILAR) method. All thin films were deposited on glass microscope slide. A precursor solution of 0.1 M of ZnCl{sub 2} complexed with ammonium hydroxide and water close to boiling point (92 deg. C) as a second solution was used for the ZnO films. An uncomplexed bath comprised of 0.1 M ZnCl{sub 2}, 0.1 M MnCl{sub 2,} and a second solution of 0.1 ml of NH{sub 4}OH with water close to boiling point was used for the ZnMnO films. The film samples were deposited by the SILAR method and annealed at 200 deg. C for 15 min. These samples were characterized using X-Ray Diffraction (XRD), Scanning Electron Microscopy with Energy Dispersive Spectroscopy (EDS), and Atomic Force Microscope. Atomic absorption was used to determine quantitatively the amount of Mn incorporated into the films. According to the XRD patterns these films were polycrystalline with wurtzite hexagonal structure. The morphology of the ZnO films constituted by rice-like and flower-like structures changed significantly to nanosheet structures with the Mn incorporation. The Mn inclusion in a ZnO structure was less than 4% according to the results from EDS, XRD, and atomic absorption.

  11. The Effect of Post-Baking Temperature and Thickness of ZnO Electron Transport Layers for Efficient Planar Heterojunction Organometal-Trihalide Perovskite Solar Cells

    Directory of Open Access Journals (Sweden)

    Kun-Mu Lee

    2017-11-01

    Full Text Available Solution-processed zinc oxide (ZnO-based planar heterojunction perovskite photovoltaic device is reported in this study. The photovoltaic device benefits from the ZnO film as a high-conductivity and high-transparent electron transport layer. The optimal electron transport layer thickness and post-baking temperature for ZnO are systematically studied by scanning electron microscopy, photoluminescence and time-resolved photoluminescence spectroscopy, and X-ray diffraction. Optimized perovskite solar cells (PSCs show an open-circuit voltage, a short-circuit current density, and a fill factor of 1.04 V, 18.71 mA/cm2, and 70.2%, respectively. The highest power conversion efficiency of 13.66% was obtained when the device was prepared with a ZnO electron transport layer with a thickness of ~20 nm and when post-baking at 180 °C for 30 min. Finally, the stability of the highest performance ZnO-based PSCs without encapsulation was investigated in detail.

  12. Atomic force microscopy studies of homoepitaxial GaN layers grown on GaN template by laser MBE

    Energy Technology Data Exchange (ETDEWEB)

    Choudhary, B. S. [CSIR-National Physical Laboratory, Dr K.S. Krishnan Road, New Delhi 110012 (India); Rajasthan Technical University, Rawatbhata Road, Kota 324010 (India); Singh, A.; Tyagi, P. K. [Department of Applied Physics, Delhi Technological University, Delhi 110042 (India); Tanwar, S. [Rajasthan Technical University, Rawatbhata Road, Kota 324010 (India); Kumar, M. Senthil; Kushvaha, S. S., E-mail: kushvahas@nplindia.org [CSIR-National Physical Laboratory, Dr K.S. Krishnan Road, New Delhi 110012 (India)

    2016-04-13

    We have grown homoepitaxial GaN films on metal organic chemical vapor deposition (MOCVD) grown 3.5 µm thick GaN on sapphire (0001) substrate (GaN template) using an ultra-high vacuum (UHV) laser assisted molecular beam epitaxy (LMBE) system. The GaN films were grown by laser ablating a polycrystalline solid GaN target in the presence of active r.f. nitrogen plasma. The influence of laser repetition rates (10-30 Hz) on the surface morphology of homoepitaxial GaN layers have been studied using atomic force microscopy. It was found that GaN layer grown at 10 Hz shows a smooth surface with uniform grain size compared to the rough surface with irregular shape grains obtained at 30 Hz. The variation of surface roughness of the homoepitaxial GaN layer with and without wet chemical etching has been also studied and it was observed that the roughness of the film decreased after wet etching due to the curved structure/rough surface.

  13. Rubrene epitaxial layers for organic TFT's grown by hot wall epitaxy

    International Nuclear Information System (INIS)

    Abd AL-Baqi, S.

    2010-01-01

    discussed in a statistical analysis as well as using thermodynamic modelling. Rubrene films were grown on different substrates as well as applying electrical field during the growth to study the growth mechanism. Optical characterisation techniques like fluorescence microscopy (FM), laser scanning confocal microscopy (LSCM), time resolved photoluminescence spectra and thermally stimulated luminescence were implemented to analyse various growth conditions to obtain more details about the material and the crystallization properties. Ellipsometry was also used to find the optical parameters for rubrene thin films. By using a special evaluation program for ellipsometry, it was possible to find the thickness of rubrene films. Finally, field effect transistors with rubrene thin films as an active layer were fabricated and characterized. Better output characteristics are achieved by using a self-assembled monolayer at the interface between SiO 2 and rubrene. (author) [de

  14. Sensitivity of the crystal quality of SiGe layers grown at low temperatures by trisilane and germane

    Energy Technology Data Exchange (ETDEWEB)

    Abedin, A., E-mail: aabedin@kth.se; Moeen, M.; Cappetta, C.; Östling, M.; Radamson, H.H., E-mail: rad@kth.se

    2016-08-31

    This work investigates the crystal quality of SiGe layers grown at low temperatures using trisilane, and germane precursors. The crystal quality sensitivity was monitored for hydrogen chloride and/or minor oxygen amount during SiGe epitaxy or at the interface of SiGe/Si layers. The quality of the epi-layers was examined by quantifying noise parameter, K{sub 1/f} obtained from the power spectral density vs. 1/f curves. The results indicate that while it is difficult to detect small defect densities in SiGe layers by physical material characterization, the noise measurement could reveal the effects of oxygen contamination as low as 0.16 mPa inside and in the interface of the layers. - Highlights: • SiGe layers were grown using trisilane and germane. • Effect of HCl flow on Ge content and growth rate was investigated. • O{sub 2} partial pressures up to 4.3 mPa did not affect x-ray diffraction pattern. • O{sub 2} partial pressures as low as 0.16 mPa increased the noise level. • HCl increased metal contaminations of the layers and the noise level consequently.

  15. Engineering of nearly strain-free ZnO films on Si(1 1 1) by tuning AlN buffer thickness

    International Nuclear Information System (INIS)

    Venkatachalapathy, Vishnukanthan; Galeckas, Augustinas; Lee, In-Hwan; Kuznetsov, Andrej Yu.

    2012-01-01

    ZnO properties were investigated as a function of AlN buffer layer thickness (0–100 nm) in ZnO/AlN/Si(1 1 1) structures grown by metal organic vapor phase epitaxy. A significant improvement of ZnO film crystallinity by tuning AlN buffer thickness was confirmed by x-ray diffraction, topography and photoluminescence measurements. An optimal AlN buffer layer thickness of 50 nm is defined, which allows for growth of nearly strain-free ZnO films. The presence of free excitons at 10 K suggests high crystal quality for all ZnO samples grown on AlN/Si(1 1 1) templates. The intensities of neutral and ionized donor bound exciton lines are found to correlate with the in-plane and out-of-plane strain in the films, respectively.

  16. Engineering of nearly strain-free ZnO films on Si(1 1 1) by tuning AlN buffer thickness

    Energy Technology Data Exchange (ETDEWEB)

    Venkatachalapathy, Vishnukanthan, E-mail: vishnukanthan.venkatachalapathy@smn.uio.no [Department of Physics/Centre for Materials Science and Nanotechnology, University of Oslo, P.O. Box 1048 Blindern, NO-0316 Oslo (Norway); Galeckas, Augustinas [Department of Physics/Centre for Materials Science and Nanotechnology, University of Oslo, P.O. Box 1048 Blindern, NO-0316 Oslo (Norway); Lee, In-Hwan [School of Advanced Materials Engineering, Research Centre for Advanced Materials Development (RCAMD), Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Kuznetsov, Andrej Yu. [Department of Physics/Centre for Materials Science and Nanotechnology, University of Oslo, P.O. Box 1048 Blindern, NO-0316 Oslo (Norway)

    2012-05-15

    ZnO properties were investigated as a function of AlN buffer layer thickness (0-100 nm) in ZnO/AlN/Si(1 1 1) structures grown by metal organic vapor phase epitaxy. A significant improvement of ZnO film crystallinity by tuning AlN buffer thickness was confirmed by x-ray diffraction, topography and photoluminescence measurements. An optimal AlN buffer layer thickness of 50 nm is defined, which allows for growth of nearly strain-free ZnO films. The presence of free excitons at 10 K suggests high crystal quality for all ZnO samples grown on AlN/Si(1 1 1) templates. The intensities of neutral and ionized donor bound exciton lines are found to correlate with the in-plane and out-of-plane strain in the films, respectively.

  17. A study on the sensing of NO(sub2) and O(sub2) utilizing ZnO films grown by aerosol spray pyrolysis

    CSIR Research Space (South Africa)

    Mhlongo, GH

    2015-07-01

    Full Text Available The present paper addresses the preparation and characterization of ZnO nanostructured thin films obtained using aerosol spray pyrolysis method at different deposition periods. Aiming at understanding the chemical composition, structural...

  18. ZnO Rods with Exposed {100} Facets Grown via a Self-Catalyzed Vapor-Solid Mechanism and Their Photocatalytic and Gas Sensing Properties

    Czech Academy of Sciences Publication Activity Database

    Vallejos, S.; Pizúrová, Naděžda; Gracia, I.; Sotelo-Vazquez, C.; Cechal, J.; Blackman, C.; Parkin, I.; Cane, C.

    2016-01-01

    Roč. 8, č. 48 (2016), s. 33335-33342 ISSN 1944-8244 Institutional support: RVO:68081723 Keywords : ZnO * rods * AACVD * gas sensing Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 7.504, year: 2016

  19. Effect of Ag doping on the structural, electrical and optical properties of ZnO grown by MOCVD at different substrate temperatures

    Science.gov (United States)

    Ievtushenko, A.; Karpyna, V.; Eriksson, J.; Tsiaoussis, I.; Shtepliuk, I.; Lashkarev, G.; Yakimova, R.; Khranovskyy, V.

    2018-05-01

    ZnO films and nanostructures were deposited on Si substrates by MOCVD using single source solid state zinc acetylacetonate (Zn(AA)) precursor. Doping by silver was realized in-situ via adding 1 and 10 wt. % of Ag acetylacetonate (Ag(AA)) to zinc precursor. Influence of Ag on the microstructure, electrical and optical properties of ZnO at temperature range 220-550 °C was studied by scanning, transmission electron and Kelvin probe force microscopy, photoluminescence and four-point probe electrical measurements. Ag doping affects the ZnO microstructure via changing the nucleation mode into heterogeneous and thus transforming the polycrystalline films into a matrix of highly c-axis textured hexagonally faceted nanorods. Increase of the work function value from 4.45 to 4.75 eV was observed with Ag content increase, which is attributed to Ag behaviour as a donor impurity. It was observed, that near-band edge emission of ZnO NS was enhanced with Ag doping as a result of quenching deep-level emission. Upon high doping of ZnO by Ag it tends to promote the formation of basal plane stacking faults defect, as it was observed by HR TEM and PL study in the case of 10 wt.% of Ag. Based on the results obtained, it is suggested that NS deposition at lower temperatures (220-300 °C) is more favorable for p-type doping of ZnO.

  20. Reducing the layer number of AB stacked multilayer graphene grown on nickel by annealing at low temperature.

    Science.gov (United States)

    Velasco, J Marquez; Giamini, S A; Kelaidis, N; Tsipas, P; Tsoutsou, D; Kordas, G; Raptis, Y S; Boukos, N; Dimoulas, A

    2015-10-09

    Controlling the number of layers of graphene grown by chemical vapor deposition is crucial for large scale graphene application. We propose here an etching process of graphene which can be applied immediately after growth to control the number of layers. We use nickel (Ni) foil at high temperature (T = 900 °C) to produce multilayer-AB-stacked-graphene (MLG). The etching process is based on annealing the samples in a hydrogen/argon atmosphere at a relatively low temperature (T = 450 °C) inside the growth chamber. The extent of etching is mainly controlled by the annealing process duration. Using Raman spectroscopy we demonstrate that the number of layers was reduced, changing from MLG to few-layer-AB-stacked-graphene and in some cases to randomly oriented few layer graphene near the substrate. Furthermore, our method offers the significant advantage that it does not introduce defects in the samples, maintaining their original high quality. This fact and the low temperature our method uses make it a good candidate for controlling the layer number of already grown graphene in processes with a low thermal budget.

  1. Effects of O2 plasma post-treatment on ZnO: Ga thin films grown by H2O-thermal ALD

    Science.gov (United States)

    Lee, Yueh-Lin; Chuang, Jia-Hao; Huang, Tzu-Hsuan; Ho, Chong-Long; Wu, Meng-Chyi

    2013-03-01

    Transparent conducting oxides have been widely employed in optoelectronic devices using the various deposition methods such as sputtering, thermal evaporator, and e-gun evaporator technologies.1-3 In this work, gallium doped zinc oxide (ZnO:Ga) thin films were grown on glass substrates via H2O-thermal atomic layer deposition (ALD) at different deposition temperatures. ALD-GZO thin films were constituted as a layer-by-layer structure by stacking zinc oxides and gallium oxides. Diethylzinc (DEZ), triethylgallium (TEG) and H2O were used as zinc, gallium precursors and oxygen source, respectively. Furthermore, we investigated the influences of O2 plasma post-treatment power on the surface morphology, electrical and optical property of ZnO:Ga films. As the result of O2 plasma post-treatment, the characteristics of ZnO:Ga films exhibit a smooth surface, low resistivity, high carrier concentration, and high optical transmittance in the visible spectrum. However, the transmittance decreases with O2 plasma power in the near- and mid-infrared regions.

  2. Low Temperature Hydrothermal Growth of ZnO Nanorod Films for Schottky Diode Application

    International Nuclear Information System (INIS)

    Singh, Shaivalini; Park, Si-Hyun

    2016-01-01

    The purpose of this research is to report on the fabrication and characterizations of Pd/ZnO nanorod-based Schottky diodes for optoelectronic applications. ZnO nanorods (NRs) were grown on silicon (Si) substrates by a two step hydrothermal method. In the first step, a seed layer of pure ZnO was deposited from a solution of zinc acetate and ethyl alcohol, and then in the second step, the main growth of the ZnO NRs was done over the seed layer. The structural morphology and optical properties of the ZnO NR films were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-vis spectroscopy. The electrical characterization of the Pd/ZnO NR contacts was studied using a current-voltage (I-V) tool. The ZnO NR films exhibited a wurtzite ZnO structure,and the average length of the ZnO NRs were in the range of 750 nm to 800 nm. The values of ideality factor, turn-on voltage and reverse saturation current were calculated from the I-V characteristics of Pd/ZnO NR-based Schottky diodes. The study demonstrates that Pd/ZnO NR Schottky contacts fabricated by a simple and inexpensive method can be used as a substitute for conventional Schottky diodes for optoelectronic applications.

  3. Photoelectrochemical properties of the TiO2-ZnO nanorod hierarchical structure prepared by hydrothermal process

    Directory of Open Access Journals (Sweden)

    Bao SUN

    2018-02-01

    Full Text Available In order to increase the transport channels of the photogenerated electrons and enhance the photosensitizer loading ability of the electrode, a new TiO2-ZnO nanorod hierarchical structure is prepared through two-step hydrothermal process. First, TiO2 nanorod array is grown on the FTO conductive glass substrate by hydrothermal proess. Then, ZnO sol is coated onto the TiO2 nanorods through dip-coating method and inverted to ZnO seed layer by sintering. Finally, the secondary ZnO nanorods are grown onto the TiO2 nanorods by the sencond hydrothermal method to form the designed TiO2-ZnO nanorod hierarchical structure. A spin-coating assisted successive ionic layer reaction method (SC-SILR is used to deposit the CdS nanocrystals into the TiO2 nanorod array and the TiO2-ZnO nanorod hierarchical structure is used to form the CdS/TiO2 and CdS/TiO2-ZnO nanocomposite films. Different methods, such as SEM, TEM, XRD, UV-Vis and transient photocurrent, are employed to characterize and measure the morphologies, structures, light absorption and photoelectric conversion performance of all the samples, respectively. The results indicate that, compared with the pure TiO2 nanorod array, the TiO2-ZnO nanorod hierarchical structure can load more CdS photosensitizer. The light absorption properties and transient photocurrent performance of the CdS/TiO2-ZnO nanorod hierarchical structure composite film are evidently superior to that of the CdS/TiO2 nanocomposite films. The excellent photoelctrochemical performance of theTiO2-ZnO hierarchical structure reveales its application prospect in photoanode material of the solar cells.

  4. Insitu grown superhydrophobic Zn-Al layered double hydroxides films on magnesium alloy to improve corrosion properties

    Science.gov (United States)

    Zhou, Meng; Pang, Xiaolu; Wei, Liang; Gao, Kewei

    2015-05-01

    A hierarchical superhydrophobic zinc-aluminum layered double hydroxides (Zn-Al LDHs) film has been fabricated on a magnesium alloy substrate via a facile hydrothermal crystallization method following chemical modification. The characteristics of the films were investigated by X-ray diffraction (XRD), scanning electronic microscope (SEM), and energy dispersive spectroscopy (EDS). XRD patterns and SEM images showed that the micro/nanoscale hierarchical LDHs film surfaces composed of ZnO nanorods and Zn-Al LDHs nanowalls structures. The static contact angle (CA) for the prepared surfaces was observed at around 165.6°. The corrosion resistance of the superhydrophobic films was estimated by electrochemical impedance spectroscopy (EIS) and potentiondynamic polarization measurement. EIS and polarization measurements revealed that the superhydrophobic Zn-Al LDHs coated magnesium alloy had better corrosion resistance in neutral 3.5 wt.% NaCl solution.

  5. Solution-Processed In2O3/ZnO Heterojunction Electron Transport Layers for Efficient Organic Bulk Heterojunction and Inorganic Colloidal Quantum-Dot Solar Cells

    KAUST Repository

    Eisner, Flurin

    2018-04-25

    We report the development of a solution‐processed In2O3/ZnO heterojunction electron transport layer (ETL) and its application in high efficiency organic bulk‐heterojunction (BHJ) and inorganic colloidal quantum dot (CQD) solar cells. Study of the electrical properties of this low‐dimensional oxide heterostructure via field‐effect measurements reveals that electron transport along the heterointerface is enhanced by more than a tenfold when compared to the individual single‐layer oxides. Use of the heterojunction as the ETL in organic BHJ photovoltaics is found to consistently improve the cell\\'s performance due to the smoothening of the ZnO surface, increased electron mobility and a noticeable reduction in the cathode\\'s work function, leading to a decrease in the cells’ series resistance and a higher fill factor (FF). Specifically, non‐fullerene based organic BHJ solar cells based on In2O3/ZnO ETLs exhibit very high power conversion efficiencies (PCE) of up to 12.8%, and high FFs of over 70%. The bilayer ETL concept is further extended to inorganic lead‐sulphide CQD solar cells. Resulting devices exhibit excellent performance with a maximum PCE of 8.2% and a FF of 56.8%. The present results highlight the potential of multilayer oxides as novel ETL systems and lay the foundation for future developments.

  6. MOF-Derived ZnO Nanoparticles Covered by N-Doped Carbon Layers and Hybridized on Carbon Nanotubes for Lithium-Ion Battery Anodes.

    Science.gov (United States)

    Zhang, Hui; Wang, Yunsong; Zhao, Wenqi; Zou, Mingchu; Chen, Yijun; Yang, Liusi; Xu, Lu; Wu, Huaisheng; Cao, Anyuan

    2017-11-01

    Metal-organic frameworks (MOFs) have many promising applications in energy and environmental areas such as gas separation, catalysis, supercapacitors, and batteries; the key toward those applications is controlled pyrolysis which can tailor the porous structure, improve electrical conductivity, and expose metal ions in MOFs. Here, we present a systematic study on the structural evolution of zeolitic imidazolate frameworks hybridized on carbon nanotubes (CNTs) during the carbonization process. We show that a number of typical products can be obtained, depending on the annealing time, including (1) CNTs wrapped by relatively thick carbon layers, (2) CNTs grafted by ZnO nanoparticles which are covered by thin nitrogen-doped carbon layers, and (3) CNTs grafted by aggregated ZnO nanoparticles. We also investigated the electrochemical properties of those hybrid structures as freestanding membrane electrodes for lithium ion batteries, and the second one (CNT-supported ZnO covered by N-doped carbon) shows the best performance with a high specific capacity (850 mA h/g at a current density of 100 mA/g) and excellent cycling stability. Our results indicate that tailoring and optimizing the MOF-CNT hybrid structure is essential for developing high-performance energy storage systems.

  7. Solution-Processed In2O3/ZnO Heterojunction Electron Transport Layers for Efficient Organic Bulk Heterojunction and Inorganic Colloidal Quantum-Dot Solar Cells

    KAUST Repository

    Eisner, Flurin; Seitkhan, Akmaral; Han, Yang; Khim, Dongyoon; Yengel, Emre; Kirmani, Ahmad R.; Xu, Jixian; Garcí a de Arquer, F. Pelayo; Sargent, Edward H.; Amassian, Aram; Fei, Zhuping; Heeney, Martin; Anthopoulos, Thomas D.

    2018-01-01

    We report the development of a solution‐processed In2O3/ZnO heterojunction electron transport layer (ETL) and its application in high efficiency organic bulk‐heterojunction (BHJ) and inorganic colloidal quantum dot (CQD) solar cells. Study of the electrical properties of this low‐dimensional oxide heterostructure via field‐effect measurements reveals that electron transport along the heterointerface is enhanced by more than a tenfold when compared to the individual single‐layer oxides. Use of the heterojunction as the ETL in organic BHJ photovoltaics is found to consistently improve the cell's performance due to the smoothening of the ZnO surface, increased electron mobility and a noticeable reduction in the cathode's work function, leading to a decrease in the cells’ series resistance and a higher fill factor (FF). Specifically, non‐fullerene based organic BHJ solar cells based on In2O3/ZnO ETLs exhibit very high power conversion efficiencies (PCE) of up to 12.8%, and high FFs of over 70%. The bilayer ETL concept is further extended to inorganic lead‐sulphide CQD solar cells. Resulting devices exhibit excellent performance with a maximum PCE of 8.2% and a FF of 56.8%. The present results highlight the potential of multilayer oxides as novel ETL systems and lay the foundation for future developments.

  8. Full coverage of perovskite layer onto ZnO nanorods via a modified sequential two-step deposition method for efficiency enhancement in perovskite solar cells

    Science.gov (United States)

    Ruankham, Pipat; Wongratanaphisan, Duangmanee; Gardchareon, Atcharawon; Phadungdhitidhada, Surachet; Choopun, Supab; Sagawa, Takashi

    2017-07-01

    Full coverage of perovskite layer onto ZnO nanorod substrates with less pinholes is crucial for achieving high-efficiency perovskite solar cells. In this work, a two-step sequential deposition method is modified to achieve an appropriate property of perovskite (MAPbI3) film. Surface treatment of perovskite layer and its precursor have been systematically performed and their morphologies have been investigated. By pre-wetting of lead iodide (PbI2) and letting it dry before reacting with methylammonium iodide (MAI) provide better coverage of perovskite film onto ZnO nanorod substrate than one without any treatment. An additional MAI deposition followed with toluene drop-casting technique on the perovskite film is also found to increase the coverage and enhance the transformation of PbI2 to MAPbI3. These lead to longer charge carrier lifetime, resulting in an enhanced power conversion efficiency (PCE) from 1.21% to 3.05%. The modified method could been applied to a complex ZnO nanorods/TiO2 nanoparticles substrate. The enhancement in PCE to 3.41% is observed. These imply that our introduced method provides a simple way to obtain the full coverage and better transformation to MAPbI3 phase for enhancement in performances of perovskite solar cells.

  9. Hydrogen-Induced Plastic Deformation in ZnO

    Science.gov (United States)

    Lukáč, F.; Čížek, J.; Vlček, M.; Procházka, I.; Anwand, W.; Brauer, G.; Traeger, F.; Rogalla, D.; Becker, H.-W.

    In the present work hydrothermally grown ZnO single crystals covered with Pd over-layer were electrochemically loaded with hydrogen and the influence of hydrogen on ZnO micro structure was investigated by positron annihilation spectroscopy (PAS). Nuclear reaction analysis (NRA) was employed for determination of depth profile of hydrogen concentration in the sample. NRA measurements confirmed that a substantial amount of hydrogen was introduced into ZnO by electrochemical charging. The bulk hydrogen concentration in ZnO determined by NRA agrees well with the concentration estimated from the transported charge using the Faraday's law. Moreover, a subsurface region with enhanced hydrogen concentration was found in the loaded crystals. Slow positron implantation spectroscopy (SPIS) investigations of hydrogen-loaded crystal revealed enhanced concentration of defects in the subsurface region. This testifies hydrogen-induced plastic deformation of the loaded crystal. Absorbed hydrogen causes a significant lattice expansion. At low hydrogen concentrations this expansion is accommodated by elastic straining, but at higher concentrations hydrogen-induced stress exceeds the yield stress in ZnO and plastic deformation of the loaded crystal takes place. Enhanced hydrogen concentration detected in the subsurface region by NRA is, therefore, due to excess hydrogen trapped at open volume defects introduced by plastic deformation. Moreover, it was found that hydrogen-induced plastic deformation in the subsurface layer leads to typical surface modification: formation of hexagonal shape pyramids on the surface due to hydrogen-induced slip in the [0001] direction.

  10. Atmospheric spatial atomic-layer-deposition of Zn(O, S) buffer layer for flexible Cu(In, Ga)Se2 solar cells: From lab-scale to large area roll to roll processing

    NARCIS (Netherlands)

    Frijters, C.H.; Bolt, P.J.; Poodt, P.W.G.; Knaapen, R.; Brink, J. van den; Ruth, M.; Bremaud, D.; Illiberi, A.

    2016-01-01

    In this manuscript we present the first successful application of a spatial atomic-layer-deposition process to thin film solar cells. Zn(O,S) has been grown by spatial atomic layer deposition (S-ALD) at atmospheric pressure and applied as buffer layer in rigid and flexible CIGS cells by a lab-scale

  11. Hydrogen-related defects in Al2O3 layers grown on n-type Si by the atomic layer deposition technique

    Science.gov (United States)

    Kolkovsky, Vl.; Stübner, R.

    2018-04-01

    The electrical properties of alumina films with thicknesses varying from 15 nm to 150 nm, grown by the atomic layer deposition technique on n-type Si, were investigated. We demonstrated that the annealing of the alumina layers in argon (Ar) or hydrogen (H) atmosphere at about 700 K resulted in the introduction of negatively charged defects irrespective of the type of the substrate. These defects were also observed in samples subjected to a dc H plasma treatment at temperatures below 400 K, whereas they were not detected in as-grown samples and in samples annealed in Ar atmosphere at temperatures below 400 K. The concentration of these defects increased with a higher H content in the alumina films. In good agreement with theory we assigned these defects to interstitial H-related defects.

  12. Nanomechanical properties of thick porous silicon layers grown on p- and p+-type bulk crystalline Si

    International Nuclear Information System (INIS)

    Charitidis, C.A.; Skarmoutsou, A.; Nassiopoulou, A.G.; Dragoneas, A.

    2011-01-01

    Highlights: → The nanomechanical properties of bulk crystalline Si. → The nanomechanical properties of porous Si. → The elastic-plastic deformation of porous Si compared to bulk crystalline quantified by nanoindentation data analysis. - Abstract: The nanomechanical properties and the nanoscale deformation of thick porous Si (PSi) layers of two different morphologies, grown electrochemically on p-type and p+-type Si wafers were investigated by the depth-sensing nanoindentation technique over a small range of loads using a Berkovich indenter and were compared with those of bulk crystalline Si. The microstructure of the thick PSi layers was characterized by field emission scanning electron microscopy. PSi layers on p+-type Si show an anisotropic mesoporous structure with straight vertical pores of diameter in the range of 30-50 nm, while those on p-type Si show a sponge like mesoporous structure. The effect of the microstructure on the mechanical properties of the layers is discussed. It is shown that the hardness and Young's modulus of the PSi layers exhibit a strong dependence on their microstructure. In particular, PSi layers with the anisotropic straight vertical pores show higher hardness and elastic modulus values than sponge-like layers. However, sponge-like PSi layers reveal less plastic deformation and higher wear resistance compared with layers with straight vertical pores.

  13. Growth and characterization of textured well-faceted ZnO on planar Si(100, planar Si(111, and textured Si(100 substrates for solar cell applications

    Directory of Open Access Journals (Sweden)

    Chin-Yi Tsai

    2017-09-01

    Full Text Available In this work, textured, well-faceted ZnO materials grown on planar Si(100, planar Si(111, and textured Si(100 substrates by low-pressure chemical vapor deposition (LPCVD were analyzed by X-ray diffraction (XRD, scanning electron microscopy (SEM, atomic force microscopy (AFM, and cathode luminescence (CL measurements. The results show that ZnO grown on planar Si(100, planar Si(111, and textured Si(100 substrates favor the growth of ZnO(110 ridge-like, ZnO(002 pyramid-like, and ZnO(101 pyramidal-tip structures, respectively. This could be attributed to the constraints of the lattice mismatch between the ZnO and Si unit cells. The average grain size of ZnO on the planar Si(100 substrate is slightly larger than that on the planar Si(111 substrate, while both of them are much larger than that on the textured Si(100 substrate. The average grain sizes (about 10–50 nm of the ZnO grown on the different silicon substrates decreases with the increase of their strains. These results are shown to strongly correlate with the results from the SEM, AFM, and CL as well. The reflectance spectra of these three samples show that the antireflection function provided by theses samples mostly results from the nanometer-scaled texture of the ZnO films, while the micrometer-scaled texture of the Si substrate has a limited contribution. The results of this work provide important information for optimized growth of textured and well-faceted ZnO grown on wafer-based silicon solar cells and can be utilized for efficiency enhancement and optimization of device materials and structures, such as heterojunction with intrinsic thin layer (HIT solar cells.

  14. Structural characterization of AgGaTe{sub 2} layers grown on a- and c-sapphire substrates by a closed space sublimation method

    Energy Technology Data Exchange (ETDEWEB)

    Uruno, Aya; Usui, Ayaka [Department of Electrical Engineering and Bioscience, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan); Kobayashi, Masakazu [Department of Electrical Engineering and Bioscience, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan); Kagami Memorial Research Institute for Materials Science and Technology, Waseda University, 2-8-26 Nishiwaseda, Shinjuku, Tokyo 169-0051 (Japan)

    2014-07-15

    AgGaTe{sub 2} layers were grown on a- and c-plane sapphire substrates by a closed space sublimation method with varying the source temperature. Grown films were evaluated by θ -2θ and pole figure measurements of X-ray diffraction. AgGaTe{sub 2} layers were grown to have strong preference for the (103) orientation. However, it was cleared the Ag{sub 5}Te{sub 3} was formed along with the AgGaTe{sub 2} when the layer was grown on c-plane sapphire. The orientation of the film was analyzed by using the pole figure, and resulted in AgGaTe{sub 2} without Ag{sub 5}Te{sub 3} layers could be grown on a-plane sapphire. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. Electrical and Photo-Induced Degradation of ZnO Layers in Organic Photovoltaics

    DEFF Research Database (Denmark)

    Manor, Assaf; Katz, Eugene A.; Tromholt, Thomas

    2011-01-01

    minutes) does not affect the short-circuit current of the device. However, a significant degradation of V-OC and FF has been recorded by measurements of the cell current-voltage curves with a variation of light intensity, for the devices before and after the treatment. The same degradation was found......We present the case of degradation of organic solar cells by sunlight concentrated to a moderate level (similar to 4 suns). This concentration level is not enough for sufficient acceleration of the photobleaching or trap-generation in the photoactive layer and therefore such short treatment (100...

  16. Investigation of InN layers grown by MOCVD using analytical and high resolution TEM: The structure, band gap, role of the buffer layers

    International Nuclear Information System (INIS)

    Ruterana, P.; Abouzaid, M.; Gloux, F.; Maciej, W.; Doualan, J.L.; Drago, M.; Schmidtling, T.; Pohl, U.W.; Richter, W.

    2006-01-01

    In this work we investigate the microstructure of InN layers grown by MOCVD on different buffer layers using TEM (InN, GaN). The large mismatch between the various lattices (InN, sapphire or GaN) leads to particular interface structures. Our local analysis allows to show that at atomic scale, the material has the InN lattice parameters and that no metallic In precipitates are present, meaning that the PL emission below 0.8 eV is a genuine property of the InN semiconductor. It is also shown that the N polar layers, which exhibit a 2D growth, have poorer PL emission than In polar layers. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Enhanced B doping in CVD-grown GeSn:B using B δ-doping layers

    Science.gov (United States)

    Kohen, David; Vohra, Anurag; Loo, Roger; Vandervorst, Wilfried; Bhargava, Nupur; Margetis, Joe; Tolle, John

    2018-02-01

    Highly doped GeSn material is interesting for both electronic and optical applications. GeSn:B is a candidate for source-drain material in future Ge pMOS device because Sn adds compressive strain with respect to pure Ge, and therefore can boost the Ge channel performances. A high B concentration is required to obtain low contact resistivity between the source-drain material and the metal contact. To achieve high performance, it is therefore highly desirable to maximize both the Sn content and the B concentration. However, it has been shown than CVD-grown GeSn:B shows a trade-off between the Sn incorporation and the B concentration (increasing B doping reduces Sn incorporation). Furthermore, the highest B concentration of CVD-grown GeSn:B process reported in the literature has been limited to below 1 × 1020 cm-3. Here, we demonstrate a CVD process where B δ-doping layers are inserted in the GeSn layer. We studied the influence of the thickness between each δ-doping layers and the δ-doping layers process conditions on the crystalline quality and the doping density of the GeSn:B layers. For the same Sn content, the δ-doping process results in a 4-times higher B doping than the co-flow process. In addition, a B doping concentration of 2 × 1021 cm-3 with an active concentration of 5 × 1020 cm-3 is achieved.

  18. Ultra-smooth epitaxial Ge grown on Si(001) utilizing a thin C-doped Ge buffer layer

    KAUST Repository

    Mantey, J.

    2013-01-01

    Here, we present work on epitaxial Ge films grown on a thin buffer layer of C doped Ge (Ge:C). The growth rate of Ge:C is found to slow over time and is thus unsuitable for thick (>20 nm) layers. We demonstrate Ge films from 10 nm to >150 nm are possible by growing pure Ge on a thin Ge:C buffer. It is shown that this stack yields exceedingly low roughness levels (comparable to bulk Si wafers) and contains fewer defects and higher Hall mobility compared to traditional heteroepitaxial Ge. The addition of C at the interface helps reduce strain by its smaller atomic radius and its ability to pin defects within the thin buffer layer that do not thread to the top Ge layer. © 2013 AIP Publishing LLC.

  19. Anomalous diffusion of Ga and As from semi-insulating GaAs substrate into MOCVD grown ZnO films as a function of annealing temperature and its effect on charge compensation

    Directory of Open Access Journals (Sweden)

    Pranab Biswas

    2014-05-01

    Full Text Available The diffusion behavior of arsenic (As and gallium (Ga atoms from semi-insulating GaAs (SI-GaAs into ZnO films upon post-growth annealing vis-à-vis the resulting charge compensation was investigated with the help of x-ray photoelectron spectroscopy (XPS and secondary ion mass spectroscopy. The films, annealed at 600 ºC and 700 ºC showed p-type conductivity with a hole concentration of 1.1 × 1018 cm−3 and 2.8 × 1019 cm−3 respectively, whereas those annealed at 800 ºC showed n-type conductivity with a carrier concentration of 6.5 × 1016 cm−3. It is observed that at lower temperatures, large fraction of As atoms diffused from the SI-GaAs substrates into ZnO and formed acceptor related complex, (AsZn–2VZn, by substituting Zn atoms (AsZn and thereby creating two zinc vacancies (VZn. Thus as-grown ZnO which was supposed to be n-type due to nonstoichiometric nature showed p-type behavior. On further increasing the annealing temperature to 800 ºC, Ga atoms diffused more than As atoms and substitute Zn atoms thereby forming shallow donor complex, GaZn. Electrons from donor levels then compensate the p-type carriers and the material reverts back to n-type. Thus the conversion of carrier type took place due to charge compensation between the donors and acceptors in ZnO and this compensation is the possible origin of anomalous conduction in wide band gap materials.

  20. Buffer layers grown by replicating the texture of an original template tape

    International Nuclear Information System (INIS)

    Lim, Sunme; Yoo, Jaeun; Park, Chan; Youm, Dojun

    2007-01-01

    We propose a fabrication method of the buffer layers, whose biaxial textures are replicated from an original template tape. The purpose of this method is economical texturing process for coated conductors. At first we prepared a biaxially textured metal tape (TM-tape). Then a sacrifice layer (SA), a buffer layer (BU) and a thick metallic layer (SM) were sequentially deposited on the TM-tape. SA-layer and BU-layer were deposited epitaxially to copy the texture of the TM-tape. SA-layer was dissoluble in water. SM-layer with the textured BU-layer was separated and could be used for a supporting tape for the further growth of a superconducting layer. In this way, it is possible to reuse the original textured TM-tape many times. In this paper, we report the results of our experiments, in which we used a biaxially Ni tape, BaO film, STO film, and a thick Ag film for TM-tape, SA-layer, BU-layer, and SM-layer, respectively. The Ag/STO layers were successfully separated form the Ni tape by dissolving the BaO layer in water. The texture quality of the STO layer was well secured after the separation

  1. Enhanced ZnO Thin-Film Transistor Performance Using Bilayer Gate Dielectrics

    KAUST Repository

    Alshammari, Fwzah Hamud; Nayak, Pradipta K.; Wang, Zhenwei; Alshareef, Husam N.

    2016-01-01

    We report ZnO TFTs using Al2O3/Ta2O5 bilayer gate dielectrics grown by atomic layer deposition. The saturation mobility of single layer Ta2O5 dielectric TFT was 0.1 cm2 V-1 s-1, but increased to 13.3 cm2 V-1 s-1 using Al2O3/Ta2O5 bilayer dielectric with significantly lower leakage current and hysteresis. We show that point defects present in ZnO film, particularly VZn, are the main reason for the poor TFT performance with single layer dielectric, although interfacial roughness scattering effects cannot be ruled out. Our approach combines the high dielectric constant of Ta2O5 and the excellent Al2O3/ZnO interface quality, resulting in improved device performance. © 2016 American Chemical Society.

  2. Enhanced ZnO Thin-Film Transistor Performance Using Bilayer Gate Dielectrics

    KAUST Repository

    Alshammari, Fwzah Hamud

    2016-08-24

    We report ZnO TFTs using Al2O3/Ta2O5 bilayer gate dielectrics grown by atomic layer deposition. The saturation mobility of single layer Ta2O5 dielectric TFT was 0.1 cm2 V-1 s-1, but increased to 13.3 cm2 V-1 s-1 using Al2O3/Ta2O5 bilayer dielectric with significantly lower leakage current and hysteresis. We show that point defects present in ZnO film, particularly VZn, are the main reason for the poor TFT performance with single layer dielectric, although interfacial roughness scattering effects cannot be ruled out. Our approach combines the high dielectric constant of Ta2O5 and the excellent Al2O3/ZnO interface quality, resulting in improved device performance. © 2016 American Chemical Society.

  3. Crystalline nanostructured Cu doped ZnO thin films grown at room temperature by pulsed laser deposition technique and their characterization

    Energy Technology Data Exchange (ETDEWEB)

    Drmosh, Qasem A. [Department of Mechanical Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Rao, Saleem G.; Yamani, Zain H. [Laser Research Group, Department of Physics, Center of Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Gondal, Mohammed A., E-mail: magondal@kfupm.edu.sa [Laser Research Group, Department of Physics, Center of Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia)

    2013-04-01

    We report structural and optical properties of Cu doped ZnO (ZnO:Cu) thin films deposited on glass substrate at room temperature by pulsed laser deposition (PLD) method without pre and post annealing contrary to all previous reports. For preparation of (ZnO:Cu) composites pure Zn and Cu targets in special geometrical arrangements were exposed to 248 nm radiations generated by KrF exciter laser. The laser energy was 200 mJ with 10 Hz frequency and 20 ns pulse width. The effect of Cu concentration on crystal structure, morphology, and optical properties were investigated by XRD, FESEM and photoluminescence spectrometer respectively. A systematic shift in ZnO (0 0 2) peak with Cu concentration observed in XRD spectra demonstrated that Cu ion has been incorporated in ZnO lattice. Uniform film with narrow size range grains were observed in FESEM images. The photoluminescence (PL) spectra measured at room temperature revealed a systematic red shift in ZnO emission peak and decrease in the band gap with the increase in Cu concentration. These results entail that PLD technique can be realized to deposit high quality crystalline ZnO and ZnO:Cu thin films without pre and post heat treatment which is normally practiced worldwide for such structures.

  4. The role of annealing temperature variation on ZnO nanorods array deposited on TiO2 seed layer

    Science.gov (United States)

    Asib, N. A. M.; Aadila, A.; Afaah, A. N.; Rusop, M.; Khusaimi, Z.

    2018-05-01

    Seed layer of Titanium dioxide (TiO2) by sol-gel spin coating technique were coated on glass substrate to grow Zinc oxide nanorods (ZNR) by solution-immersion method. The fabricated ZNR were annealed at various temperatures ranged from 400 to 600° C. FESEM images revealed that smaller ZNR were densely grown at optimum temperature of 450 and 500°C. Meanwhile, for all samples a dominant (0 0 2) diffraction peak of ZNR recorded by XRD patterns was at 34.4° which corresponding to hexagonal ZNR with a wurtzite structure. UV-Vis absorbance spectra showed the maximum absorption properties at UV region were detected at 450 and 500°C. The samples also showed high absorbance values at visible region.

  5. Fabrication of layered hydroxide zinc nitrate films and their conversion to ZnO nanosheet assemblies for use in dye-sensitized solar cells

    Directory of Open Access Journals (Sweden)

    Takuya Yuki

    2015-03-01

    Full Text Available Layered hydroxide zinc nitrate (LHZN; Zn5(NO32(OH8·xH2O films were fabricated on glass or plastic substrates by a chemical bath deposition method combined with a homogeneous precipitation in methanolic solutions. High- or low-temperature pyrolytic decomposition of the LHZN films having two-dimensional morphology was attempted to obtain porous ZnO nanosheet-assembly films. The LHZN films were converted into porous ZnO films by pyrolyzing at temperatures above 400 °C, while porous LHZN/ZnO hybrid films were obtained by pyrolyzing at a lower temperature of 120 °C without morphological changes. The pyrolyzed ZnO films were applied to dye-sensitized solar cells (DSSCs, resulting in the generation of relatively high open-circuit voltages. The low-temperature pyrolysis enabled us to fabricate the LHZN/ZnO film even on the plastic substrate. Actually a cell using the LHZN/ZnO film on an indium tin oxide-coated polyethylene naphthalate substrate showed an energy conversion efficiency of 2.08% with a high open-circuit voltage around 0.70 V.

  6. Luminescence and Morphological Properties of GaN Layers Grown on SiC/Si(111) Substrates

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Garcia, M.A.; Ristic, J.; Calleja, E. [ISOM and Dpto. Ing. Electronica, ETSI Telecomunicacion, Univ. Politecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain); Perez-Rodriguez, A.; Serre, C.; Romano-Rodriguez, A.; Morante, J.R. [EME - Electronic Materials and Engineering, Department of Electronics, Universidad de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); Koegler, R.; Skorupa, W. [Institute of Ion Beam Physics and Materials Research, Forschungszentrum Rossendorf e.V., 01314 Dresden (Germany); Trampert, A.; Ploog, K.H. [Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

    2002-08-16

    This article describes the fabrication of SiC thin films on top of Si(111) substrates by means of a multiple C-ion implantation and the subsequent growth by plasma-assisted molecular beam epitaxy of GaN layers. The stoichiometry of the top SiC layer is controlled by reactive ion etching. Photoluminescence spectra reveal that all GaN layers are under biaxial tensile strain of thermal origin. The photoluminescence efficiency clearly depends on the stoichiometry of the initial SiC layer and on whether AlN buffer layers are used or not. GaN layers grown directly on bare non-stoichiometric SiC layers exhibit the best photoluminescence efficiency but also a high degree of mosaicity, as measured by X-ray diffraction techniques. The nucleation process involved in the initial stages of the growth leads to the formation of large dislocation-free grains with a high PL efficiency and with a higher tensile strain character. Despite the lack of a perfect monocrystalline SiC substrate lattice, high quality GaN microcrystals are obtained. (Abstract Copyright[2002], Wiley Periodicals, Inc.)

  7. Comparative study of polar and semipolar (112¯2) InGaN layers grown by metalorganic vapour phase epitaxy

    International Nuclear Information System (INIS)

    Dinh, Duc V.; Zubialevich, V. Z.; Oehler, F.; Kappers, M. J.; Humphreys, C. J.; Alam, S. N.; Parbrook, P. J.; Caliebe, M.; Scholtz, F.

    2014-01-01

    InGaN layers were grown simultaneously on (112 ¯ 2) GaN and (0001) GaN templates by metalorganic vapour phase epitaxy. At higher growth temperature (≥750 °C), the indium content ( ¯ 2) and (0001) InGaN layers was similar. However, for temperatures less than 750 °C, the indium content of the (112 ¯ 2) InGaN layers (15%–26%) were generally lower than those with (0001) orientation (15%–32%). The compositional deviation was attributed to the different strain relaxations between the (112 ¯ 2) and (0001) InGaN layers. Room temperature photoluminescence measurements of the (112 ¯ 2) InGaN layers showed an emission wavelength that shifts gradually from 380 nm to 580 nm with decreasing growth temperature (or increasing indium composition). The peak emission wavelength of the (112 ¯ 2) InGaN layers with an indium content of more than 10% blue-shifted a constant value of ≈(50–60) nm when using higher excitation power densities. This blue-shift was attributed to band filling effects in the layers.

  8. Ultra-Fast Microwave Synthesis of ZnO Nanorods on Cellulose Substrates for UV Sensor Applications

    Directory of Open Access Journals (Sweden)

    Ana Pimentel

    2017-11-01

    Full Text Available In the present work, tracing and Whatman papers were used as substrates to grow zinc oxide (ZnO nanostructures. Cellulose-based substrates are cost-efficient, highly sensitive and environmentally friendly. ZnO nanostructures with hexagonal structure were synthesized by hydrothermal under microwave irradiation using an ultrafast approach, that is, a fixed synthesis time of 10 min. The effect of synthesis temperature on ZnO nanostructures was investigated from 70 to 130 °C. An Ultra Violet (UV/Ozone treatment directly to the ZnO seed layer prior to microwave assisted synthesis revealed expressive differences regarding formation of the ZnO nanostructures. Structural characterization of the microwave synthesized materials was carried out by scanning electron microscopy (SEM and X-ray diffraction (XRD. The optical characterization has also been performed. The time resolved photocurrent of the devices in response to the UV turn on/off was investigated and it has been observed that the ZnO nanorod arrays grown on Whatman paper substrate present a responsivity 3 times superior than the ones grown on tracing paper. By using ZnO nanorods, the surface area-to-volume ratio will increase and will improve the sensor sensibility, making these types of materials good candidates for low cost and disposable UV sensors. The sensors were exposed to bending tests, proving their high stability, flexibility and adaptability to different surfaces.

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

    Science.gov (United States)

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

    2017-12-27

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

  10. Near-field microwave microscopy of high-κ oxides grown on graphene with an organic seeding layer

    Energy Technology Data Exchange (ETDEWEB)

    Tselev, Alexander, E-mail: tseleva@ornl.gov; Kalinin, Sergei V. [Oak Ridge National Laboratory, Center for Nanophase Materials Sciences, Oak Ridge, Tennessee 37831 (United States); Sangwan, Vinod K.; Jariwala, Deep; Lauhon, Lincoln J. [Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208 (United States); Marks, Tobin J.; Hersam, Mark C. [Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208 (United States); Department of Chemistry, Northwestern University, Evanston, Illinois 60208 (United States)

    2013-12-09

    Near-field scanning microwave microscopy (SMM) is used for non-destructive nanoscale characterization of Al{sub 2}O{sub 3} and HfO{sub 2} films grown on epitaxial graphene on SiC by atomic layer deposition using a self-assembled perylene-3,4,9,10-tetracarboxylic dianhydride seeding layer. SMM allows imaging of buried inhomogeneities in the dielectric layer with a spatial resolution close to 100 nm. The results indicate that, while topographic features on the substrate surface cannot be eliminated as possible sites of defect nucleation, the use of a vertically heterogeneous Al{sub 2}O{sub 3}/HfO{sub 2} stack suppresses formation of large outgrowth defects in the oxide film, ultimately improving lateral uniformity of the dielectric film.

  11. Mesoporous multi-shelled ZnO microspheres for the scattering layer of dye sensitized solar cell with a high efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Weiwei; Mei, Chao; Zeng, Xianghua, E-mail: xhzeng@yzu.edu.cn; Wu, Guoqing; Shen, Xiaoshuang [College of Physics Science and Technology and Institute of Optoelectronic Technology, Yangzhou University, Yangzhou 225002 (China); Chang, Shuai [Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China)

    2016-03-14

    Both light scattering and dye adsorbing are important for the power conversion efficiency PCE performance of dye sensitized solar cell (DSSC). Nanostructured scattering layers with a large specific surface area are regarded as an efficient way to improve the PCE by increasing dye adsorbing, but excess adsorbed dye will hinder light scattering and light penetration. Thus, how to balance the dye adsorbing and light penetration is a key problem to improve the PCE performance. Here, multiple-shelled ZnO microspheres with a mesoporous surface are fabricated by a hydrothermal method and are used as scattering layers on the TiO{sub 2} photoanode of the DSSC in the presence of N719 dye and iodine–based electrolyte, and the results reveal that the DSSCs based on triple shelled ZnO microsphere with a mesoporous surface exhibit an enhanced PCE of 7.66%, which is 13.0% higher than those without the scattering layers (6.78%), indicating that multiple-shelled microspheres with a mesoporous surface can ensure enough light scattering between the shells, and a favorable concentration of the adsorbed dye can improve the light penetration. These results may provide a promising pathway to obtain the high efficient DSSCs.

  12. Transfer of preheat-treated SnO 2 via a sacrificial bridge-type ZnO layer for ethanol gas sensor

    KAUST Repository

    Lee, Da Hoon; Kang, Sun Kil; Pak, Yusin; Lim, Namsoo; Lee, Ryeri; Kumaresan, Yogeenth; Lee, Sungeun; Lee, Chaedeok; Ham, Moon-Ho; Jung, Gun Young

    2017-01-01

    The progress in developing the microelectromechanical system (MEMS) heater-based SnO2 gas sensors was hindered by the subsequent heat treatment of the tin oxide (SnO2), nevertheless it is required to obtain excellent sensor characteristics. During the sintering process, the MEMS heater and the contact electrodes can be degraded at such a high temperature, which could reduce the sensor response and reliability. In this research, we presented a process of preheating the printed SnO2 sensing layer on top of a sacrificial bridge-type ZnO layer at such a high temperature, followed by transferring it onto the contact electrodes of sensor device by selective etching of the sacrificial ZnO layer. Therefore, the sensor device was not exposed to the high sintering temperature. The SnO2 gas sensor fabricated by the transfer process exhibited a rectangular sensing curve behavior with a rapid response of 52 s at 20 ppm ethanol concentration. In addition, reliable and repeatable sensing characteristics were obtained even at an ethanol gas concentration of 5 ppm.

  13. Transfer of preheat-treated SnO 2 via a sacrificial bridge-type ZnO layer for ethanol gas sensor

    KAUST Repository

    Lee, Da Hoon

    2017-08-05

    The progress in developing the microelectromechanical system (MEMS) heater-based SnO2 gas sensors was hindere