ZnO Films (zno + film)

Distribution by Scientific Domains


Selected Abstracts


Synthesis of Aligned Arrays of Ultrathin ZnO Nanotubes on a Si Wafer Coated with a Thin ZnO Film,

ADVANCED MATERIALS, Issue 20 2005
Y. Sun
Aligned arrays of ultrathin, high-quality ZnO nanotubes (see Figure) have been synthesized via hydrothermal growth methods on Si that has been pre-coated with a thin film of ZnO. The nanorods are single-crystalline, with typical wall thicknesses and outer diameters of 5,15 and 20,40,nm, respectively. Annealing the arrays in vacuum causes enhancement of UV photoluminescence. [source]


Repeated Growing and Annealing Towards ZnO Film by Metal-Organic CVD,

CHEMICAL VAPOR DEPOSITION, Issue 7-9 2009
Chia-Cheng Wu
Abstract ZnO deposited on sapphire substrate is investigated as a function of growth temperature in the range 350,650,C. The surface morphology of ZnO structures changes significantly with increasing growth temperature. Though ZnO crystal quality and optical property can be improved under high growth temperature, ZnO is inclined to form nanostructures. Therefore, we propose the repeated growing and annealing (RGA) growth mode as a reliable and reproducible way for the growth of ZnO film. The RGA growth mode is performed at a growth temperature of 450,C for 8,min, an anneal temperature of 650,C for 20,min, and repeatedly switched between growing and annealing. Meanwhile, we compare the effects of annealing under Ar, N2, and O2, and found that a low resistivity of 3.4,,10,3,, cm and a high mobility of 85.2,cm2 V,1 s,1 can be obtained annealing under N2. [source]


Atomic Layer Deposition of UV-Absorbing ZnO Films on SiO2 and TiO2 Nanoparticles Using a Fluidized Bed Reactor,

ADVANCED FUNCTIONAL MATERIALS, Issue 4 2008
David M. King
Atomic layer deposition (ALD) was used to apply conformal, nanothick ZnO coatings on particle substrates using a fluidized bed reactor. Diethylzinc (DEZ) and water were used as precursors at 177,C. Observed growth rates were ca. 2.0 /cycle on primary particles as verified by HRTEM. ICP-AES and XPS were used to quantify Zn:substrate ratios. Layers of 6, 18, and 30 nm were deposited on 550 nm SiO2 spheres for UV blocking cosmetics particles. TiO2 nanoparticles were coated in the second part of this work by ZnO shells of 2, 5, and 10 nm thickness as novel inorganic sunscreen particles. The specific surface area of powders changed appropriately after nanothick film deposition using optimized conditions, signifying that high SA particles can be functionalized without agglomeration. The ZnO layers were polycrystalline as deposited and narrowing of the FWHM occurred upon annealing. Annealing the ZnO-TiO2 nanocomposite powder to 600,C caused the formation of zinc titanate (Zn2TiO4) in both oxygen-rich and oxygen-deficient environments. The non-ideal surface behavior of the DEZ precursor became problematic for the much longer times required for high surface area nanoparticle processing and results in Zn-rich films at this growth temperature. In situ mass spectrometry provides process control capability to functionalize bulk quantities of nano- and ultrafine particles without significant precursor waste or process overruns. ZnO overlayers can be efficiently deposited on the surfaces of primary particles using ALD processing in a scalable fluidized bed reactor. [source]


The effect of oxygen remote plasma treatment on ZnO TFTs fabricated by atomic layer deposition

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2010
Seungjun Lee
Abstract We deposited ZnO thin films by atomic layer deposition (ALD) and then investigated the chemical and electrical characteristics after plasma treatment. The chemical bonding states were examined by X-ray photoelectron spectroscopy (XPS). The XPS spectra of O 1s showed that the intensity of oxygen deficient regions of the ZnO film decreased from 27.6 to 19.4%, while the intensity of the oxygen bound on the surface of the ZnO film increased from 15.0 to 21.9% as plasma exposure times increased. The ZnO film exhibited a decrease in carrier concentration from 4.9,,1015 to 1.2,,1014,cm,3 and an increase in resistivity from 1.2,,102 to 9.8,,103,,,cm as the plasma exposure times increased. To verify the changes in the chemical and electrical properties of the ZnO films caused by the oxygen remote plasma treatment, ZnO thin film transistors were fabricated and their electrical properties were investigated. We found that the Ion/Ioff ratio increased from 7.3,,104 to 8.6,,106, the subthreshold swings improved from 1.67 to 0.45,V/decade, and the saturation mobility (sat) decreased from 1.63 to 0.72,cm2/V,s as plasma exposure times were increased. [source]


Structural evolution of ZnO films deposited by rf magnetron sputtering on glass substrate

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2010
Yan-Ping Liao
Abstract Influences of O2/Ar flux ratio (R) on surface morphology and structural evolution have been studied in the case of ZnO films deposited on glass substrates by radio-frequency (rf) magnetron sputtering. Results of atomic force microscopy (AFM), X-ray diffraction, and X-ray photoelectron spectroscopy (XPS) clearly indicate that the surface root-mean-square (rms) roughness, crystallinity, stress, and defects strongly depend on the R. At R,=,1/2, the crystallized ZnO film with highly c -axis orientation and highly smooth surface has been obtained. The implication of these results is that a moderate R is needed to realize high-quality ZnO film. [source]


Growth behavior and microstructure of ZnO epilayer on ,-LiAlO2(100) substrate by chemical vapor deposition

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 2 2009
Liuwen Chang
Abstract Low lattice-mismatched ,-LiAlO2(100) substrates were employed to grow ZnO epitaxial films by chemical vapor deposition. The influence of growth temperature on growth behavior of ZnO was investigated. Results indicated that the low lattice-matched (100) crystallites nucleate on substrate at all growth temperatures employed. However, a second type of crystallites having an (0001) orientation can also nucleate on substrate at low growth temperature of 575 C and 640 C. The growth rate of the later crystallite is, however, higher than that of the (100) one and finally results in a single crystalline ZnO film having an [0001] azimuthal orientation. ( 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Improved electrical, optical, and structural properties of undoped ZnO thin films grown by water-mist-assisted spray pyrolysis

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 10 2006
L. Martnez Prez
Abstract Undoped ZnO thin films were prepared using the ultrasonic spray pyrolysis deposition technique with zinc acetylacetonate dissolved in N,N-dimethylformamide as the source materials solution. The addition of water mist in a parallel flux to the spray solution stream was also used during deposition of the films. The addition of water mist improved the electrical characteristics of the ZnO films. Fresh ZnO samples were then thermally annealed in a H2 reducing atmosphere. X-ray diffraction patterns show mainly the wurzite crystalline ZnO phase in the films. An electrical resistivity (, ) of around 2.7 10,2 , cm was measured at room temperature for the best undoped ZnO film. , is approximately one order of magnitude lower than the resistivities found in undoped ZnO films obtained by means of similar non-vacuum deposition techniques. ( 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Photoconductivity of Ga doped polycrystalline ZnO films grown by reactive plasma deposition

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2007
Seiichi Kishimoto
Abstract Photoconductivity and photo-absorption of polycrystalline Ga-doped ZnO (GZO) thin films with film thickness of 200 nm have evaluated compared with undoped ZnO films. The GZO and undoped ZnO thin films were deposited on alkali-free glass substrate at 200 C by a reactive plasma deposition with DC arc discharge technique under an oxygen gas flow rate from 0 to 30 sccm. Undoped ZnO films with carrier concentration of 2.50 1018 and 7.96 1018 cm,3 have exciton absorption at about 3.28 eV. For these films, the photoconductivity peak is agreement with the photon-energy of exciton absorption in the optical-absorption. The optical band edge of undoped ZnO films estimated from the optical-absorption shows a shift to higher energy with increasing the carrier concentration. The increase of oxygen gas flow rate led to the resistivity change of GZO films from 2.15 10,4 to 4.54 10,3 , cm, corresponding to the carrier concentration change from 1.39 1021 to 1.05 1020 cm,3. The photoconductivity of GZO film is larger than that of undoped ZnO film. The peak energy of photoconductivity spectra of GZO films are seen to little shift to higher energy with increasing the carrier concentration. The GZO film exhibited the larger photoconductivity at the wavelength, ranging widely less than 380 nm. GZO film with carrier concentration more than 1 1021 cm,3 indicated much larger photoconductivity. ( 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Preparation of ZnO thin films by MO-CVD method using bis(acetylacetonato) zinc(II) anhydrate fiber

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2010
Shigeyuki Seki
Abstract The MO-CVD method as a deposition process corresponding to the mass production of the high-quality ZnO film that can be used as an active layer in the thin film transistor is paid to attention. Bis(acetylacetonato) zinc(II) (Zn(acac)2) which has chemical stability and low toxicity is promising as the inexpensive raw material for CVD. The problem includes (1) pollution with water in process by character to easily take water of crystallization, and (2) the supply of the gas-phase raw material by sublimation should be not able to be controlled easily because it is a fine particle. In this study, Zn(acac)2 anhydrate fiber was prepared from Zn(acac)2 monohydrate powder by the sublimation process. Melting point of this fiber was almost same (,134 C) as the monohydrate powder in N2 atmosphere. ZnO film was deposited on r-face sapphire substrate by MO-CVD process using Zn(acac)2 anhydrate fiber, successfully. RMS of the film flatness was 0.48 nm. This film had resistivity of 4.6 10,1 ,cm, carrier electron density of 9.1 1017 cm,3 and Hall mobility of 15 cm2V,1s,1. ( 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Interface properties and junction behavior of Pd contact on ZnO thin film grown by vacuum deposition technique

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2010
Ghusoon M. Ali
Abstract In this paper we explain the results of our experimental investigation on interface properties and junction behavior of Pd contact on ZnO thin film based Schottky diode. We used a conventional vacuum evaporation deposition unit for sequential deposition of ZnO film and metallic layer. For the first time a high quality Pd/ZnO Schottky diode is fabricated successfully in our laboratory by vacuum evaporation method. The I-V and C-V characteristics of the devices were studied by using microprobe arrangement. The parameter such as ideality factor, leakage current, resistance-area-product, carrier concentration and barrier height were extracted from the measured data. The surface morphological and the structural properties of thin film were studied by atomic force microscope. The optical band gap of thin film was determined using UV-visible spectrophotometer. The device fabricated by a simple technique exhibited excellent stability for use as an electronic or optoelectronic component. ( 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Fabrication of a n -type ZnO/p -type Cu,Al,O heterojunction diode by sputtering deposition methods

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2009
Satoru Takahata
Abstract CuAlO2 polycrystalline films were deposited by the helicon-wave-excited plasma sputtering (HWPS) method at 700 C. The best full-width at half-maximum value of the (006) CuAlO2 X-ray diffraction peak was 0.19 degrees, which was similar to those reported previously using other deposition methods. While, noncrystalline Cu,Al,O films were deposited by a conventional RF sputtering method. Using this p -type transparent conducting oxide (TCO) film and an n -type ZnO film deposited by HWPS, a n -type ZnO/p -type Cu,Al,O heterojunction diode was fabricated. Optical transmittance of the device was approximately 80% in the near infrared region. The rectifying current,voltage characteristics with a threshold forward voltage approximately 1.4 V were obtained. These results are the first step toward realizing an electrical/optical device using p -type CuAlO2 or Cu-Al-O films. ( 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Electro-optic property of ZnO:Mn epitaxial films

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2008
T. Oshio
Abstract Mn doping effect on the dielectric and electro-optic (E-O) property of ZnO epitaxial films was studied. The leakage current of the ZnO film is drastically decreased by doping Mn with the concentration of 3-5 at%. Although, ZnO: 4 at% Mn with the lowest leakage current has the largest frequency dispersion of birefringence shift (, n) at 1 kHz, and its E-O coefficient (rc) was larger than that of ZnO single crystal. It is presumably caused by another polarization effect but spontaneous polarization, such as space charge. To investigate the origin of the dispersion of , n, discharging property was evaluated. When the signal at 1 kHz was applied, ZnO: 3 and 5 at% Mn showed the discharging with relaxation time of 5 msec. Furthermore, the discharging property with same relaxation time was observed at 20 kHz at where the dispersion of , n was not observed. However, ZnO: 4 at% Mn does not show such a discharging behavior. Therefore, it is considered that the space charge is not the origin of the dispersion of , n. On the other hand, the dispersion of , n was minimum and no dielectric dispersion was observed at 20 kHz for all samples. The rc of ZnO: 3, 4 and 5 at% Mn measured at 20 kHz, which should be the rc originated from the spontaneous dipolar polarization, were derived to be 0.81, 0.81 and 0.62 pm/V, respectively. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Effects of low temperature buffer layer treatments on the growth of high quality ZnO films

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2004
H. Tampo
Abstract ZnO films were grown on sapphire substrates by radical source molecular beam epitaxy (RS-MBE). ZnO low temperature buffer layers were subjected to various treatments. High quality ZnO films were obtained by vacuum annealing plus nitrogen doping of the buffer layer. The carrier concentration of the ZnO film fabricated using this buffer layer was 7.5 1016 cm,3 with a mobility of 132 cm2/V sec at RT. Temperature dependent Hall measurements showed implied the existence of degenerate (untreated) buffer layers. Using a nitrogen-doped buffer layer to reduce the influence of the degenerate layer, a donor energy of 110 meV was estimated from temperature dependent Hall measurements. ( 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Repeated Growing and Annealing Towards ZnO Film by Metal-Organic CVD,

CHEMICAL VAPOR DEPOSITION, Issue 7-9 2009
Chia-Cheng Wu
Abstract ZnO deposited on sapphire substrate is investigated as a function of growth temperature in the range 350,650,C. The surface morphology of ZnO structures changes significantly with increasing growth temperature. Though ZnO crystal quality and optical property can be improved under high growth temperature, ZnO is inclined to form nanostructures. Therefore, we propose the repeated growing and annealing (RGA) growth mode as a reliable and reproducible way for the growth of ZnO film. The RGA growth mode is performed at a growth temperature of 450,C for 8,min, an anneal temperature of 650,C for 20,min, and repeatedly switched between growing and annealing. Meanwhile, we compare the effects of annealing under Ar, N2, and O2, and found that a low resistivity of 3.4,,10,3,, cm and a high mobility of 85.2,cm2 V,1 s,1 can be obtained annealing under N2. [source]


Nanocrystalline transparent SnO2 -ZnO films fabricated at lower substrate temperature using a low-cost and simplified spray technique

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 3 2010
K. Ravichandran
Abstract Nanocrystalline and transparent conducting SnO2 - ZnO films were fabricated by employing an inexpensive, simplified spray technique using a perfume atomizer at relatively low substrate temperature (3605 C) compared with conventional spray method. The structural studies reveal that the SnO2 -ZnO films are polycrystalline in nature with preferential orientation along the (101) plane. The dislocation density is very low (1.481015lines/m2), indicating the good crystallinity of the films. The crystallite size of the films was found to be in the range of 26,34 nm. The optical transmittance in the visible range and the optical band gap are 85% and 3.6 eV respectively. The sheet resistance increases from 8.74 k,/, to 32.4 k,/, as the zinc concentration increases from 0 to 40 at.%. The films were found to have desirable figure of merit (1.6310,2 (,/,),1), low temperature coefficient of resistance (,1.191/K) and good thermal stability. This simplified spray technique may be considered as a promising alternative to conventional spray for the massive production of economic SnO2 - ZnO films for solar cells, sensors and opto-electronic applications. ( 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Properties of InAs co-doped ZnO thin films prepared by pulsed laser deposition

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 12 2009
J. Elanchezhiyan
Abstract InAs co-doped ZnO films were grown on sapphire substrates by pulsed laser deposition. The grown films have been characterized using X-ray diffraction (XRD), Hall effect measurements, Atomic force microscope (AFM) and Field emission scanning electron microscope (FESEM) in order to investigate the structural, electrical, morphological and elemental properties of the films respectively. XRD analysis showed that all the films were highly orientated along the c-axis. It was observed from Hall effect measurements that InAs co-doped ZnO films were of n-type conductivity. In addition, the presence of In and As has been confirmed by Energy dispersive X-ray analysis. AFM images revealed that the surface roughness of the films was decreased upon the co-doping. ( 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Optical studies on ZnO films prepared by sol-gel method

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 8 2009
T. Ghosh
Abstract A standard sol-gel method was used to deposit ZnO thin films of suitable thickness on glass substrate. The optical characteristics of the visible to infrared range on thermal stress were critically observed. Morphological signature of the films was detected by X-ray diffraction (XRD) and the crystallite size determined by Scherrer method from XRD data were consistent with grain size estimated from spectroscopic data through Meulenkamp equation. The optical band gap value from the transmission spectrum was found to corroborate with the existing works. ( 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Vertical-type organic device using thin-film ZnO transparent electrode

ELECTRICAL ENGINEERING IN JAPAN, Issue 2 2007
Hiroyuki Iechi
Abstract We propose a double heterojunction organic light-emitting diode (OLED) using a zinc oxide (ZnO) film, which works as a transparent and electron injection layer. The crystal structure of the ZnO films as a function of Ar/O2 flow ratio and the basic characteristics of the OLED depending on the ZnO sputtering conditions are investigated. Excellent characteristics of the novel OLED were obtained, as high as 470 cd/m2 at 22 V and 7.6 mA/cm2. The results obtained here demonstrate that the vertical organic light-emitting transistor (OLET) using a ZnO layer as an electron injection layer is promising as a key element for flexible sheet displays. 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(2): 49,55, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20151 [source]


ZnO Nanostructures for Dye-Sensitized Solar Cells

ADVANCED MATERIALS, Issue 41 2009
Qifeng Zhang
Abstract This Review focuses on recent developments in the use of ZnO nanostructures for dye-sensitized solar cell (DSC) applications. It is shown that carefully designed and fabricated nanostructured ZnO films are advantageous for use as a DSC photoelectrode as they offer larger surface areas than bulk film material, direct electron pathways, or effective light-scattering centers, and, when combined with TiO2, produce a core,shell structure that reduces the combination rate. The limitations of ZnO-based DSCs are also discussed and several possible methods are proposed so as to expand the knowledge of ZnO to TiO2, motivating further improvement in the power-conversion efficiency of DSCs. [source]


Threading dislocations in domain-matching epitaxial films of ZnO

JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5 2007
W.-R. Liu
The structures of high-quality ZnO epitaxial films grown by pulsed-laser deposition on sapphire (0001) without an oxygen gas flow were investigated by X-ray diffraction and transmission electron microscopy. The great disparity of X-ray diffraction line widths between the normal and in-plane reflections reveals the specific threading dislocation geometry of ZnO. Most threading dislocations are pure edge dislocations. From a combination of scattering and microscopic results, it is found that threading dislocations are not uniformly distributed in the ZnO films, but the films consist of columnar epitaxial cores surrounded by annular regions of edge threading dislocations in large density. The local surface morphology and capacitance signal obtained from atomic force and scanning capacitance microscopes indicate that the aggregation of threading dislocations leads to high interface traps at the annular regions. [source]


Microstructure, Morphology, and Ultraviolet Emission of Zinc Oxide Nanopolycrystalline Films by the Modified Successive Ionic Layer Adsorption and Reaction Method

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2010
Daoli Zhang
Zinc oxide (ZnO) nanopolycrystalline films were successfully prepared by the modified successive ionic layer adsorption and reaction technique, which was based on the alternate immersion of substrate in the alkaline zinc precursor and deionized water. ZnO films were formed through an accumulation of ZnO crystal clusters. The size of the clusters ranged from 200 to 500 nm based on scanning electron micrographic images. Prepared ZnO films exhibited a wurtzite structure, with good microstructure, surface morphology, and optical properties. Ethanolamine was used as a complex reagent, which improved the adsorption of zinc complex with the substrate. Effects of processing parameters on the properties of ZnO nanopolycrystalline films were studied in detail. Intensive and sharp ultraviolet emission peaks at about 400 nm could be observed in the photoluminescence spectra. [source]


Effects of Individual Layer Thickness on the Microstructure and Optoelectronic Properties of Sol,Gel-Derived Zinc Oxide Thin Films

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2008
Noureddine Bel Hadj Tahar
Zinc oxide (ZnO) thin films were prepared under different conditions on glass substrates using a sol,gel process. The microstructure of ZnO films was investigated by means of diffraction analysis, and plan-view and cross-sectional scanning electron microscopy. It was found that the preparation conditions strongly affected the structure and the optoelectronic properties of the films. A structural evolution in morphology from spherical to columnar growth was observed. The crystallinity of the films was improved and columnar film growth became more dominant as the zinc concentration and the substrate withdrawal speed decreased. The individual layer thickness for layer-by-layer homoepitaxy growth that resulted in columnar grains was <20 nm. The grain columns are grown through the entire film with a nearly unchanged lateral dimension through the full film thickness. The columnar ZnO grains are c -axis oriented perpendicular to the interface and possess a polycrystalline structure. Optical transmittance up to 90% in the visible range and electrical resistivity as low as 6.8 10,3,cm were obtained under optimal deposition conditions. [source]


The effect of oxygen remote plasma treatment on ZnO TFTs fabricated by atomic layer deposition

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2010
Seungjun Lee
Abstract We deposited ZnO thin films by atomic layer deposition (ALD) and then investigated the chemical and electrical characteristics after plasma treatment. The chemical bonding states were examined by X-ray photoelectron spectroscopy (XPS). The XPS spectra of O 1s showed that the intensity of oxygen deficient regions of the ZnO film decreased from 27.6 to 19.4%, while the intensity of the oxygen bound on the surface of the ZnO film increased from 15.0 to 21.9% as plasma exposure times increased. The ZnO film exhibited a decrease in carrier concentration from 4.9,,1015 to 1.2,,1014,cm,3 and an increase in resistivity from 1.2,,102 to 9.8,,103,,,cm as the plasma exposure times increased. To verify the changes in the chemical and electrical properties of the ZnO films caused by the oxygen remote plasma treatment, ZnO thin film transistors were fabricated and their electrical properties were investigated. We found that the Ion/Ioff ratio increased from 7.3,,104 to 8.6,,106, the subthreshold swings improved from 1.67 to 0.45,V/decade, and the saturation mobility (sat) decreased from 1.63 to 0.72,cm2/V,s as plasma exposure times were increased. [source]


Structural evolution of ZnO films deposited by rf magnetron sputtering on glass substrate

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2010
Yan-Ping Liao
Abstract Influences of O2/Ar flux ratio (R) on surface morphology and structural evolution have been studied in the case of ZnO films deposited on glass substrates by radio-frequency (rf) magnetron sputtering. Results of atomic force microscopy (AFM), X-ray diffraction, and X-ray photoelectron spectroscopy (XPS) clearly indicate that the surface root-mean-square (rms) roughness, crystallinity, stress, and defects strongly depend on the R. At R,=,1/2, the crystallized ZnO film with highly c -axis orientation and highly smooth surface has been obtained. The implication of these results is that a moderate R is needed to realize high-quality ZnO film. [source]


Unique structure of ZnO films deposited by chemical bath deposition

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2009
Dewei Chu
Abstract The unique structure of ZnO films obtained from aqueous solution method was investigated. Scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) analyses indicate that unique morphology and structure of the region where precipitation on the substrate may occur in parallel with other regions. This is accompanied by a decrease of the electrical resistivity in the absorbed region. A possible mechanism for the resistivity transformation was discussed. [source]


Growth and electrical properties of ZnO films prepared by chemical bath deposition method

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2009
Dewei Chu
Abstract The influence of the choice of temperature, pH value, counter-ion, deposition time, and seed layer on the morphology as well as electrical properties of ZnO films grown from chemical bath deposition (CBD) are discussed. Consequently, oriented ZnO films with various microstructures can be synthesized by controlling the solution pH value and counter-ions. Besides, the point at which the seed layer is pre-heated at higher temperature is crucial and can lead to a significant difference in the width of crystals and electrical properties of ZnO films. ( 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Sensitivity of ZnO films doped with Er, Ta and Co to NH3 at room temperature

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2008
D. Dimova-Malinovska
Abstract The sensitivity of ZnO films, undoped and doped with Er, Ta and Co, to exposure to NH3 has been studied. The films were deposited by magnetron co-sputtering of a sintered ZnO target with chips of the different doping elements on its surface. The sensitivities of the ZnO films to exposure to NH3 were measured by the quartz crystal microbalance method using the resonance frequency shift. The adsorption process was investigated over an aqueous solution of ammonia with 100 ppm concentration. The speed and the mass of sorption were calculated on the basis of the time,frequency characteristic. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Properties of post-annealed ZnO films grown with O3

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2008
H. S. Kim
Abstract The properties of ZnO thin films grown with ozone are examined. Annealing studies were performed on ZnO films grown by pulsed-laser deposition using either O2 and an O2/O3 gas mixture as the oxidant. The carrier density of ZnO films grown with pure O2 generally decreases upon annealing in 1 atm O2. In contrast, the n-type carrier density for ZnO films grown with O2/O3 mixture gas increased with O2 annealing. The results indicate that acceptor states, created via growth in ozone, are annihilated with post-annealing. This suggests that the ozone-related acceptor states are metastable. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Enhanced ultraviolet photoluminescence from V-doped ZnO thin films prepared by a sol,gel process

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2007
Ling Wei
Abstract Undoped and vanadium-doped ZnO thin films were prepared on single-crystalline p-type Si(100) substrates by a sol,gel process and further annealed in an oxygen atmosphere. The influence of vanadium doping on the structural, surface morphological and optical properties of ZnO thin films was investigated by X-ray diffraction, atomic force microscopy and photoluminescence measurements. Both the undoped and V-doped ZnO thin films were of polycrystalline hexagonal wurtzite structure with (002)-preferred orientation. The crystallite size and the root-mean-square roughness of V-doped ZnO are smaller than those of undoped ZnO. Vanadium doping could reduce deep level defects of ZnO and thus strengthen ultraviolet (UV) emission. The peak intensity of UV emission increased with increasing annealing temperature above 400 C. After annealing at 800 C, the UV emission for the V-doped ZnO films was largely enhanced, while the visible emission was distinctly weakened. ( 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Transparent ohmic contacts to GaSb/In(Al)GaAsSb photovoltaic cells

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2007
K. Golaszewska
Abstract In this paper we present the results of study of thin oxide films: CdO, ZnO and RuSiO4 used as transparent ohmic contacts to GaSb/InGaAsSb/AlGaAsSb photodiodes. Thin oxide films with thickness of 50 nm were deposited by magnetron sputtering. CdO and RuSiO4 were formed in a reactive process in Ar,O2 atmosphere, from Cd and Ru1Si1 targets, respectively. ZnO films were deposited directly from ZnO target by rf sputtering. We have shown that application of CdO, ZnO and RuSiO4 transparent films instead of conventional metal-based contacts enables to improve of photodiode properties. As a result, GaSb/InGaAsSb/AlGaAsSb photodiodes with detectivity D * increased by factor of 2 and reduced by factor of 3 the series resistance were obtained. ( 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]