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ZnO thin films have been grown by radio frequency sputtering on Al, Au, Ni, Cu and glass substrates. Crystallinity of ZnO thin films has been estimated by X-ray diffraction (XRD) and reflected high-energy electron diffraction (RHEED). ZnO/substrates interfaces have been observed by cross-section transmission electron microscopy (TEM). ZnO thin films are classified into two groups depending on the...
Recently, there has been much interest in wide band-gap wurtzite semiconductors such as group-III nitrides (GaN, AlGaN, and InGaN) and ZnO. Ion-beam-defect processes are considerably more complex in these wurtzite semiconductors than in the case of both elemental and group-III-V cubic semiconductors. This brief review focuses on our recent studies of the following aspects of ion-beam-defect processes:...
We report on the growth of monocrystalline thin films of ZnSe and ZnO by atomic layer epitaxy by simple reaction between elemental precursors. Structural and optical properties of these films are discussed with reference to the investigations performed with atomic force microscopy, scanning electron microscopy, cathodoluminescence and photoluminescence.
Current-voltage properties along the c-axis of high-resistive Ni-doped zinc oxide (ZnO) thin film were examined. Zinc oxide thin film capacitor with Al/Ti top and bottom electrodes was fabricated on SiO 2 /Si substrate. Current saturation due to acoustoelectric effect in piezoelectric ZnO thin film was observed. The current saturation indicates that the drift velocity of electron reaches the...
High-quality ZnO epitaxial films without rotation domain structure were successfully prepared on sapphire (0001) substrates using metal organic chemical vapor deposition method. The ZnO films deposited by rf sputtering at the substrate temperature of 300 o C with (0001) preferred orientation were used as a very thin intermediate buffer layer with the thickness of 5-40nm. In the X-ray diffraction...
Thin ZnO-SnO 2 films were deposited on glass substrates by opposed planar magnetron sputtering, in which ZnO and SnO 2 :Sb (Sb 2 O 5 3wt% doped) targets face each other. Glass substrate temperatures (T s ) were held at 150 o C and 250 o C. As an experimental parameter, current ratio δ, ZnO target current divided by the sum of ZnO and SnO ...
Crystallinity of ZnO thin film for film bulk acoustic wave (BAW) resonator has been successfully improved by using Pt/Al bottom electrode. The lattice mismatch of ZnO c-plane and Pt (111) plane is as small as 1.4% so that we could obtain good crystallinity ZnO film on Pt surface. The effective electromechanical coupling coefficient (kt eff2 ) of the BAW resonator that we fabricated...
The effects of Al 2 O 3 dopings in pseudobinary (In 2 O 3 ) 1-δ (2ZnO) δ films were investigated, and carrier generation mechanism was discussed. Here the δ value is the ratio of Zn/(Zn+In). For Al 2 O 3 doping below 2wt%, low-resitivity amorphous films in 2-4x10 -4 Ωcm were deposited over a narrow range of δ=Zn/(Zn+In)...
We have improved electrical characteristics of a film bulk acoustic wave (BAW) resonator that features the injection of H 2 O gas into a process chamber. The preferred crystallinity of piezoelectric ZnO film was obtained by RF sputtering at a high H 2 O partial pressure 1.5×10 −4 Pa. The effective electromechanical coupling coefficient (kteff2) of the BAW resonator remarkably...
Polycrystalline ZnO thin films were synthesized on Si(111) substrates by pulsed laser deposition (PLD) under oxygen sufficient condition at temperatures ranging from 550 to 700∘C. The results of in situ reflection high-energy electron diffraction (RHEED) and X-ray diffraction (XRD) show that the (002) orientation of ZnO thin films is deteriorated, but the full-width at half-maximum (FWHM) of (002)...
Analysis of positron lifetime data for ZnO single crystals suggests that four well-separated lifetime levels exist between those for the bulk and the Zn vacancy. Due to the hydrothermal growth conditions of most ZnO single crystals studied so far, it is postulated that a hydrogen–defect interaction could be responsible for this finding.
The cathodic electrodeposition of nanocrystalline zinc oxide (ZnO) thin films from an aqueous zinc acetate containing electrochemical bath is reported. Scanning electron microscopic examination of the resultant films reveals the formation of nanoporous ZnO. X-ray diffraction (XRD) analysis indicates that the ZnO thin films deposited with crystallite sizes as small as 10nm are possible with this method...
This paper reports the preparation and gas-sensing characteristic of ZnO:TiO 2 -based hydrogen sulfide (H 2 S) gas sensor with different mol% of CdO by polymerized complex method. The structural and gas-sensing properties of ZnO:TiO 2 materials have been characterized using X-ray diffraction and gas-sensing measurement. The electrical resistance response of the sensor based...
ZnO films were synthesized on Si(111) substrates by pulsed laser deposition (PLD) under four different growth conditions. The structural and optical properties of the samples were characterized by reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), and photoluminescence (PL) measurement. It is found that when ZnO film is directly prepared on Si, oxygen atmosphere can significantly...
The effects of buffer layer deposition conditions on subsequent ZnO epitaxy on sapphire (0001) were examined. An initial ZnO buffer layer improves surface roughness for a wide range of buffer layer growth temperatures and pressures. Changes in buffer layer growth pressure and temperature have a moderate effect on the roughness of subsequent film growth. However, the conditions for buffer layer deposition...
Highly c-axis oriented ZnO thin films were grown on Si (100) substrates with Zn buffer layers. Effects of the Zn buffer layer thickness on the structural and optical qualities of ZnO thin films were investigated for the ZnO films with the buffer layers 90, 110, and 130nm thick using X-ray diffraction (XRD), photoluminescence (PL) and atomic force microscopy (AFM) analysis techniques. It was confirmed...
Large-scale and dense ZnO thin films with novel petal-like architectures were directly electrodeposited on the Au/ITO glass substrates from aqueous solution of Zn(NO 3 ) 2 and HMTA at a low temperature of 70°C for the first time. Scanning electron microscopic (SEM) investigation revealed that the Au/ITO glass substrates are fully covered with densely distributed ZnO petal-like architectures...
ZnO tetrapod-liked nanostructure with fine crystalline structure and high purity was synthesized via CVD method. Each branch of the nanotetrapod was 50–200nm in diameter and the nanotetrapod structure exhibited a high aspect ratio. Cathode emission materials with this nanostructure were employed to fabricate field emission display with 72×72 pixel array. The as-obtained device showed an ideal field...
Influence of incorporation of Ga in amorphous In–Zn–O transparent conductive oxide films was investigated as a function of Zn/(Zn+In). For In–Zn–O films with no Ga 2 O 3 , the range of Zn/(Zn+In) ratio where the amorphous phase appears became narrow at a substrate temperature of 250°C. With increasing Ga 2 O 3 quantity, amorphous films were obtained even at a high substrate...
The effects of a metal oxide under-layer on the resistivity of a Ag layer were investigated. Ag-based multilayers, which have a layer construction of glass/ZnO under-layer/Ag/ZAO (Al-doped ZnO) blocker/ZnO top layer, were deposited by DC magnetron sputtering with changing the sputter gas pressure during the under-layer deposition and it was confirmed that the Ag layer showed low resistivity when the...
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