• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.2
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• pp.109-113
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• 2013

ZnO thin films were synthesized on Si substrates by MOCVD using diethyl zinc as a precursor. Effects of $O_2$/DEZ gas mixing ratio on the growth rate, surface morphology, preferred orientation, and electrical properties of the ZnO thin films were investigated with SEM, XRD, and Hall measurement. The surface reflectance variations of ZnO thin films were analyzed using laser-photometer apparatus. As the $O_2$/DEZ mixing ratio increased, growth rate and $I_{(002)}/I_{(101)}$ in XRD of ZnO thin films decreased, and the crystal structure was changed from columnar to planar structure. All ZnO films deposited at various CVD conditions exhibited c-axis (002) plane preferred orientation. The electrical properties of ZnO thin films mainly depended on the carrier mobility.

• Korean Journal of Materials Research
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• v.23 no.3
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• pp.161-167
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• 2013

The ZnO thin films were grown on GaN template substrates by RF magnetron sputtering at different RF powers and n-ZnO/p-GaN heterojunction LEDs were fabricated to investigate the effect of the RF power on the characteristics of the n-ZnO/p-GaN LEDs. For the growth of the ZnO thin films, the substrate temperature was kept constant at $200^{\circ}C$ and the RF power was varied within the range of 200 to 500W at different growth times to deposit films of 100 nm thick. The electrical, optical and structural properties of ZnO thin films were investigated by ellipsometry, X-ray diffraction (XRD), atomic force microscopy (AFM), photoluminescence (PL) and by assessing the Hall effect. The characteristics of the n-ZnO/p-GaN LEDs were evaluated by current-voltage (I-V) and electroluminescence (EL) measurements. ZnO thin films were grown with a preferred c-axis orientation along the (0002) plane. The XRD peaks shifted to low angles and the surface roughness became non-uniform with an increase in the RF power. Also, the PL emission peak was red-shifted. The carrier density and the mobility decreased with the RF power. For the n-ZnO/p-GaN LED, the forward current at 20 V decreased and the threshold voltage increased with the RF power. The EL emission peak was observed at approximately 435 nm and the luminescence intensity decreased. Consequently, the crystallinity of the ZnO thin films grown with RF sputtering powers were improved. However, excess Zn affected the structural, electrical and optical properties of the ZnO thin films when the optimal RF power was exceeded. This excess RF power will degrade the characteristics of light emitting devices.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.10
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• pp.1488-1493
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• 2017

Boron-doped ZnO:Al films were deposited by rf magnetron sputtering. The structural and optical property variations of the films with the boron amounts were studied. ZnO nanorods were grown on $SiO_2/Si$ wafers and glass by a hydrothermal method. ~50 nm-thick boron-doped ZnO:Al films were deposited on the substrates as seed layers. The mixed solution of zinc nitrate hexahydrate and hexamethylenetetramine in DI water was used as a precursor for ZnO nanorods. The concentration of zinc nitrate hexahydrate and that of hexamethylenetetramine were 0.05 mol, respectively. ZnO nanorods were grown at $90^{\circ}C$ for 2 hours. X-ray diffraction was conducted to observe the crystallinity of ZnO nanorods. A field emission scanning electron microscope was employed to study the morphology of nanorods. Optical transmittance was measured by a UV-Vis spectrophotometer, and photoluminescence was carried out with 266 nm light. The ZnO nanorods grown on the 0.5 wt% boron-doped ZnO seed layer showed the best crystallinity.

• Korean Journal of Crystallography
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• v.6 no.2
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• pp.134-140
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• 1995

SAW properties of SiNx/ZnO bilayer thin film structure were analyzed. ZnO thin films were deposited by rf magnetron sputter using O2 gas as an oxidizer. Structure of ZnO thin films was affected by Ar/O2 ratio. At the gas ratio of Ar/O2=67/33, the standard deviation of X-ray rocking curve of (002) preferred ZnO thin film was 2.17 degree. This value is sufficient to use ZnO thin films as an acoustic element. SAW velocity of glass/SiNx(7000Å)/Al/ZnO(5μm) structure was max. 2.2% faster than that of ZnO/glass.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.2
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• pp.116-119
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• 2005

Al doped ZnO thin films (ZnO:Al) were deposited on poly carbonate (PC) substrate by rf magnetron sputtering. In addition, the electrical, optical properties of the films prepared at various conditions were investigated. As the sputter power increased, the resistivity of ZnO:Al films decreased, regardless of substrate types. However, the resistivity of the films increased with the sputter pressure. The ZnO:Al films were increasingly dark gray colored as the sputter power increased, resulting in the loss of transmittance. High quality films with resistivity as low as 1.43${\times}$10$^{-4}$ Ω-cm and transmittance over 80 % have been obtained by suitably controlling the deposition parameters.

• Journal of the Korean Society for Heat Treatment
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• v.25 no.2
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• pp.85-89
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• 2012

Transparent conductive ZnO/Ag/ZnO (ZAZ) multilayer films were deposited by Radio frequency (RF) magnetron sputtering and direct current (DC) magnetron sputtering. The effects of post deposition vacuum annealing temperature on the structural, electrical and optical properties of the ZAZ multilayer films were investigated. The thickness of ZAZ films is kept constant at ZnO 50 nm/Ag 5nm/ZnO 45 nm, while the vacuum annealing temperatures were varied from 200 and $400^{\circ}C$, respectively. As-deposited ZAZ films exhibit a sheet resistance of $6.1{\Omega}/{\Box}$ and optical transmittance of 72.7%. By increasing annealing temperature to $200^{\circ}C$, the resistivity decreased to as low as $5.3{\Omega}/{\Box}$ and optical transmittance also increased to as high as 82.1%. Post-deposition annealing of ZAZ multilayer films lead to considerably lower electrical resistivity and higher optical transparency, simultaneously by increased crystallization of the films.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.1
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• pp.72-77
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• 2013

The effect of sputtering condition on the structural properties of ZnO thin films grown by RF magnetron sputtering system was investigated for TFT driver circuit. ZnO thin films were grown with ZnO target varying RF power and working pressure. Structural properties were investigated by X-ray diffraction (XRD) and atomic force microscope (AFM). The ZnO thin films have sufficient crystallinity on the 100W RF power. But, the surface roughness of ZnO films was increased as increased RF power. As increased working pressure from 5 mTorr to 15 mTorr, a full width at half maximum (FWHM) of ZnO (002) peak was increased.

• Journal of the Korean Vacuum Society
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• v.17 no.3
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• pp.204-210
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• 2008

ZnO thin films were grown on a glass by RF sputtering system with RF power 100W and oxygen partial pressure of $0%{/sim}30%$. Elliptic constants were measured by using a phase modulated spectroscopic ellipsometer and analyzed with the Tauc-Lorentz dispersion formula and best fit method in the range of 1.5 to 3.8eV. Also, scanning electron microscope(SEM) was used for the analysis of surface crystallization condition. From elliptic constants spectra, optical constants, thickness and roughness of ZnO films were evaluated. Total thickness of ZnO films obtained by ellipsometry showed good agreement with SEM data. It was found that the grain size of the films were getting smaller with increasing oxygen partial pressure. Band-gap of ZnO films increase with the oxygen partial pressure. These findings clearly indicate that optical properties of ZnO films are strongly dependent on the oxygen partial pressure. It could be explained that increasing the oxygen partial pressure induced high crystalline imperfection in the ZnO films.

• Journal of the Korean Vacuum Society
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• v.7 no.3
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• pp.201-207
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• 1998

We have investigated about interface characteristics between ZnO thin films and metal electrodes when ZnO and metal electrodes were fabricated as piezoelectric vibrators. At this, ZnO thin films were deposited by rf reactive magnetron sputtering method. After fabricating piezoelectric vibrator of Cr/ZnO/Cr structure with optimum condition, we analyse interface characteristics between ZnO thin films and metal electrodes by I-V measurement. AES depth profile, SEM and C-V measurement. From these measurements we found that ZnO piezoelectric vibrators showed good property when they fabricated as Cr/$SiO_2$/ZnO/Cr structure. And we could confirm these things by driving, and measuring vibration displacement of piezoelectric vibrator with $SiO_2$diffusion barrier.

• Journal of Sensor Science and Technology
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• v.15 no.3
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• pp.216-221
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• 2006

ZnO thin films prepared by PLD method exhibit an excellent optical property, but may have some problems such as incomplete surface roughness and crystallinity. In this study, undoped ZnO buffer layers were deposited on (0001) sapphire substrates by ultra high vacuum pulse laser deposition (UHV-PLD) and molecular beam epitaxy (MBE) methods, respectively. After post annealing of ZnO buffer layer, undoped ZnO thin films were deposited under different oxygen pressure ($35{\sim}350$ mtorr) conditions. The Arsenic-doped (1, 3 wt%) ZnO thin layers were deposited on the buffer layer of undoped ZnO by UHV-PLD method. The optical property of the ZnO thin films was analyzed by photoluminescence (PL) measurement. The ${\theta}-2{\theta}$ XRD analysis exhibited a strong (002)-peak, which indicates c-axis preferred orientation. Field emission-scanning electron microscope (FE-SEM) revealed that microstructures of the ZnO thin films were varied by oxygen partial pressure, Arsenic doping concentration, and deposition method of the undoped ZnO buffer layer. The denser and smoother films were obtained when employing MBE-buffer layer under lower oxygen partial pressure. It was also found that higher Arsenic concentration gave the enhanced growing of columnar structure of the ZnO thin films.