• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.1
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• pp.65-69
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• 2003

ZnO-Si-ZnO multi-layer thin films have been deposited by pulsed laser deposition (PLD). And then, the films have been annealed at 300$^{\circ}C$ in oxygen ambient pressure. Peak positions of ultraviolet (UV) and visible region were changed by addition of Si layer. Mobility of the films was improved slightly than ZnO thin film without Si layer. The structural property changed by inserting intermediate Si layer in ZnO thin film. The optical properties and structural properties of ZnO-Si-ZnO multi-layer thin films were characterized by PL(Photoluminescence) and XRB(X-ray diffraction) method, respectively. Electrical properties were measured by van der Pauw Hall measurements

• Journal of the Korean Ceramic Society
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• v.33 no.2
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• pp.149-154
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• 1996

ZnO and Al-doped ZnO thin films were prepared by sol-gel dip-coating method and electrical and optical properties of films were investigated. Using the zinc acetate dihydrate and acetylaceton(AcAc) as a chelating agent stable ZnO sol was synthesized with HCl catalyst. Adding aluminium chloride to the ZnO sol Al-doped ZnO sol could be also synthesized. As Al contents increase the crystallinity of ZnO thin film was retarded by increased compressive stress in the film resulted from the difference of ionic radius between Zn2+ and Al3+ The thickness of ZnO and Al-doped ZnO thin film was in the range of 2100~2350$\AA$. The resistivity of ZnO thin films was measured by Van der Pauw method. ZnO and Al-doped ZnO thin films with annealing temperature and Al content had the resistivity of 0.78~1.65$\Omega$cm and ZnO and Al-doped ZnO thin film post-annealed at 40$0^{\circ}C$ in vacuum(5$\times$10-5 torr) showed the resistivity of 2.28$\times$10-2$\Omega$cm. And the trans-mittance of ZnO and Al-doped ZnO thin film is in the range of 91-97% in visible range.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.10
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• pp.811-816
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• 2012

The effect of co-sputtering condition on the structural properties of $Mg_xZn_{1-x}O$ thin films grown by RF magnetron co-sputtering system was investigated for manufacturing ZnO/MgZnO structure LED. $Mg_xZn_{1-x}O$ thin films were grown with ZnO and MgO target varying RF power. Structural properties were investigated by X-ray diffraction (XRD) and Energy dispersive spectroscopy (EDS). The ZnO thin films have sufficient crystallinity on the high RF power. As RF power of ZnO target increased, the contents of MgO in the $Mg_xZn_{1-x}O$ film decreased. LED was manufactured using ZnO/MgZnO multi-layer on p-GaN/$Al_2O_3$ substrate. Threshold voltage of multi-layer LED was appeared at 8 V, and it was luminesced at wave length of 550 nm.

• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.27-29
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• 2005

ZnO and phosphorus doped ZnO thin films (ZnO:P) are deposited by pulsed laser deposition grown on (001) $Al_{2}O_{3}$. ZnO/ZnO:P/ZnO/$Al_{2}O_{3}$ (multi-layer) structure was used for phosphorus doped ZnO fabrication. This multi-layer structure thin film was annealed at $400^{\circ}C$ for 40 min. The electron concentration of that was changed from $10^{19}$ to $10^{16}/cm^{-3}$ after annealing. ZnO thin films with encapsulated structure showed the enhanced structural and optical properties than phosphorus doped ZnO without encapsulated layer. In this study, encapsulated ZnO structure was suggested to enhance electrical, structural and optical properties of phosphorus doped ZnO thin film and it was identified that encapsulated structure could be used to fabricate high quality phosphorus doped ZnO thin film.

• Journal of the Korean Vacuum Society
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• v.12 no.4
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• pp.214-217
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• 2003

In this study, we prepared ZnO thin film on $SiO_2$/Si substrate by FTS (Facing Targets Sputtering) apparatus which can reduce damage on the thin film because the bombardment of high-energy Particles such as ${\gamma}$-electron can be restrained. And, properties of thin filnl grown with ZnO buffer-layer which can be suppress initial growth layer was investigated. The crystalline and the c-axis preferred orientation of ZnO thin film was also investigated by XRD. As a result, we noticed that the ZnO thin film has a good crystallographic characteristic at thickness of ZnO buffer layer 10, 20 nm and working pressure 1 mTorr.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.54-54
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• 2010

Zinc oxide is metal oxide semiconductor with the 3.37 eV bandgap energy. Zinc oxide is very attractive materials for many application fields. Zinc Oxide has many advantages such as high conductivity and good transmittance in visible region. Also it is cheaper than other semiconductor materials such as indium tin oxide (ITO). Therefore, ZnO is alternative material for ITO. ZnO is attracting attention for its application to transparent conductive oxide (TCO) films, surface acoustic wave (SAW), films bulk acoustic resonator (FBAR), piezoelectric materials, gas-sensing, solar cells and photocatalyst. In this study, we synthesized ZnO nanoparticles and defined their physical and chemical properties. Also we studied about the application of ZnO nanoparticles as a photocatalyst and try to find a enhancement photocatalytic activity of ZnO nanorticles.. We synthesized ZnO nanoparticles using spray-pyrolysis method and defined the physical and optical properties of ZnO nanoparticles in experiment I. When the ZnO are exposed to UV light, reduction and oxidation(REDOX) reaction will occur on the ZnO surface and generate ${O_2}^-$ and OH radicals. These powerful oxidizing agents are proven to be effective in decomposition of the harmful organic materials and convert them into $CO_2$ and $H_2O$. Therefore, we investigated that the photocatalytic activity was increased through the surface modification of synthesized ZnO nanoparticles. In experiment II, we studied on the stability of ZnO nanoparticles in water. It is well known that ZnO is unstable in water in comparison with $TiO_2$. $Zn(OH)_2$ was formed at the ZnO surface and ZnO become inactive as a photocatalyst when ZnO is present in the solution. Therefore, we prepared synthesized ZnO nanoparticles that were immersed in the water and dried in the oven. After that, we measured photocatalytic activities of prepared samples and find the cause of their photocatalytic activity changes.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.3
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• pp.15-20
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• 2007

Low temperature processed ZnO-TFTs on glass below $270^{\circ}C$ for plastic substrate applications were fabricated and their electrical properties were investigated. Films in ZnO-TFTs with bottom gate configuration were made by RF magnetron sputtering system except for $SiO_2$ gate oxide deposited by ICP-CVD. ZnO channel films were grown on glass with various Ar and $O_2$ flow ratios. All of the fabricated ZnO-TFTs showed perfectly the enhancement mode operation, a high optical transmittance of above 80% in visible ranges of the spectrum. In the ZnO-TFTs with pure Ar process, the field effect mobility, threshold voltage, and on/off ratio were measured to be $1.2\;cm^2/Vs$, 8.5 V, and $5{\times}10^5$, respectively. These characteristic values are much higher than those of the ZnO-TFTs of which ZnO channel layers were processed with additional $O_2$ gas. In addition, ZnO-TFT with pure Af process showed smaller swing voltage of 1.86v/decade compared to those with $Ar+O_2$ process.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.2
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• pp.190-197
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• 2002

In this thesis, ZnO varistors with various formulation, such as A∼E, were fabricated according to ceramic fabrication method. The microstructure, electrical properties, and surge characteristics of ZnO varistors were investigated according to ZnO varistors with various formulation. In the microstructure, A∼E\`s ZnO varistor ceramics sintered at 1130$\^{C}$ was consisted of ZnO grain(ZnO), spinel phase (Zn$\_$2.33/Sb$\_$0.67/O$\_$4/), Bi-rich phase(Bi$_2$O$_3$) and intergranuler phase, wholly. Lightning impulse residual voltage of A, B, C and E\`s ZnO varistors suited standard characteristics, below 12kV at current of 5kA. On the contrary, D\`s ZnO varistor exhibited high residual voltage as high reference voltage. In the accelerated aging test, leakage current and watt loss of B, C and D\`s ZnO varistors increases abruptly with stress time under the first a.c. stress(115$\^{C}$/3.213kV/300h). Consequently, C varistor exhibited a thermal run away. On the contrary, leakage current and watt loss of A and C\`s ZnO varistors which show low initial leakage current exhibited constant characteristics. After high current impulse test, A\`s ZnO varistor has broken the side of varistor but impulse current flowed. On the contrary, E\`s ZnO Varistor exhibited good discharge characteristics which the appearance of varistor was not wrong such as puncture, flashover, creaking and other significant damage. After long duration impulse current test, E\`s ZnO varistor exhibited good discharge characteristics which the appearance of varistor was not wrong such as puncture, flashover, creaking and other significant damage. After high current impulse test and long duration impulse current test, E\`s ZnO varistor exhibited very good characteristics which variation rate of residual voltage is 1.4% before and after test.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.552-556
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• 2002

The microstructure and electrical characteristics of A~C's ZnO varistors fabricated according to variable sintering condition, which sintering temperature is $1130^{\circ}C$ and speeds of pusher are A: 2mm/min, B: 4mm/min, C: 6mm/min, respectively, were investigated. In the microstructure, A~C's ZnO varist-ors fabricated variable sintering condition was consisted of ZnO grain(ZnO), spinel phase$(Zn_{2.33}Sb_{0.67}O_4)$ Bi-rich $phase(Bi_{2}O_{3})$, wholly. Varistor voltage of A~C's ZnO varistors sintered at $1130^{\circ}C$ increased in order A < B < C's ZnO varistors. C's ZnO varistor exhibited good characteristics that nonlinear exponent is 31.70. Leakage current of A~C's ZnO varistors exhibited below 2mA at rated voltage. Lightning impulse residual voltage of A's ZnO varistor suited standard characteristics, which is 3.85kV at 2.5kA, 4.4kV at 5kA and 5.16kV at 10kA. After multi lightning impulse residual voltage test of A's ZnO varistor exhibited good discharge characteristics which ZnO varistor reveals no evidence of puncture, flashover, cracking in visual examination. After high current impulse test of A's ZnO varistor exhibited good discharge characteristics, which variation rate of residual voltage is 0.4% before and after test, and revealed no evidence.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.450-450
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• 2011

This study reports the hydrogen sulfide gas sensing properties of ZnO nanorods bundle and the investigation of gas sensing mechanism. Also the improvement of sensing properties was also studied through the application of ZnO heterstructured nanorods. The 1-Dimensional ZnO nano-structure was synthesized by hydrothermal method and ZnO nano-heterostructures were prepared by sonochemical reaction. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) spectra confirmed a well-crystalline ZnO of hexagonal structure. The gas response of ZnO nanorods bundle sensor increased with increasing temperature, which is thought to be due to chemical reaction of nanorods with gas molecules. Through analysis of X-ray photoelectron spectroscopy (XPS), the sensing mechanism of ZnO nanorods bundle sensor was explained by well-known surface reaction between ZnO surface atoms and hydrogen sulfide. However at high sensing temperature, chemical conversion of ZnO nanorods becomes a dominant sensing mechanism in current system. In order to improve the gas sensing properties, simple type of gas sensor was fabricated with ZnO nano-heterostructures, which were prepared by deposition of CuO, Au on the ZnO nanorods bundle. These heteronanostructures show higher gas response and higher current level than ZnO nanorods bundle. The gas sensing mechanism of the heteronanostructure can be explained by the chemical conversion of sensing material through the reaction with target gas.