• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.8
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• pp.516-521
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• 2014

An excellent hydrophobic surface has a high contact angle over 147 degree and the contact angle hysteresis below $5^0$ was produced by using roughness combined with hydrophobic PTFE coatings, which were also confirmed to exhibit an extreme adhesion to glass substrate. To form the rough surface, the glass was etched by Ar-plasma. A very thin PTFE film was coated on the plasma etched glass surface. Roughness factors before or after PTFE coating on the plasma etched glass surface, based on Wensel's model were calculated, which agrees well with the dependence of the contact angle on the roughness factor is predicted by Wensel's model. The PTFE films deposited on glass by using a conventional rf-magnetron sputtering. The glass substrates were etched Ar-plasma prior to the deposition of PTFE. Their hydrophobicities are investigated for application as a anti-fouling coating layer on the screen of displays. It is found that the hydrophobicity of PTFE films mainly depends on the sputtering conditions, such as rf-power, Ar gas content introduced during deposition. These conditions are closely related to the deposition rate or thickness of PTFE film. Thus, it is also found that the deposition rate or the film thickness affects sensitively the geometrical morphology formed on surface of the rf-sputtered PTFE films. In particular, 1,950-nm-thick PTFE films deposited for 30 minute by rf-power 50 watt under Ar gas content of 20 sccm shows a very excellent optical transmittance and a good anti-fouling property and a good durability.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.6
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• pp.392-397
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• 2018

In this paper, the ZnS nanoparticles were synthesized according to the process conditions of hydrothermal synthesis. When the molar ratio of Zn to S was 1:1.2, it was confirmed that it had a cubic single phase and a high crystal phase. After the molar ratio is fixed, hydrothermal synthesis was conducted at $180^{\circ}C$ for 24, 36, 72 and 96 h in order to confirm the structural change with the change of hydrothermal synthesis times. As the hydrothermal synthesis times increased, the particle size increased. The hydrothermal synthesized particle size for 72 h was considered to be suitable for sintering. The ZnS ceramic had a density of 99.7% and an excellent transmittance of ~70% in the long-wavelength region.

• Journal of Sensor Science and Technology
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• v.24 no.6
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• pp.364-367
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• 2015

Tin oxide thin films were fabricated on glass substrates by the successive ionic layer adsorption and reaction (SILAR) method at room temperature and ambient pressure. Before measuring their properties, all samples were annealed at $500^{\circ}C$ for 2 h in air. Film thickness increased with the number of cycles; X-ray diffraction patterns for the annealed $SnO_2$ thin films indicated a $SnO_2$ single phase. Thickness of the $SnO_2$ films increased from 12 to 50 nm as the number of cycles increased from 20 to 60. Although the optical transmittance decreased with thickness, 50 nm $SnO_2$ thin films exhibited a high value of more than 85%. Regarding electronic properties, sheet resistance of the films decreased as thickness increased; however, the measured resistivity of the thin film was nearly constant with thickness ($3{\times}10^{-4}ohm/cm$). From Hall measurements, the 50 nm thickness $SnO_2$ thin film had the highest mobility of the samples ($8.6cm^2/(V{\cdot}s)$). In conclusion, optical and electronic properties of $SnO_2$ thin films could be controlled by adjusting the number of SILAR cycles.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.6
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• pp.789-793
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• 2018

All transparent metal oxide photoelectric device based on $V_2O_5$ was fabricated with structure of $V_2O_5/ZnO/ITO$ by magnetron sputtering system. $V_2O_5$ was deposited by reactive sputtering system with 4 inch vanadium target (purity 99.99%). In order to achieve p-n junction, p-type $V_2O_5$ was deposited onto the n-type ZnO layer. The ITO (indium tin oxide) was applied as the electron transporting layer for effective collection of the photo-induced electrons. Electrical and optical properties were analyzed. The Mott-Schottky analysis was applied to investigate the energy band diagram through the metal oxide layers. The $V_2O_5/ZnO/ITO$ photoelectric device has a rectifying ratio of 99.25 and photoresponse ratios of 1.6, 4.88 and 2.68 under different wavelength light illumination of 455 nm, 560 nm and 740 nm. Superior optical properties were realized with the high transmittance of average 70 % for visible light range. Transparent $V_2O_5$ layer absorbs the short wavelength light efficiently while passing the visible light. This research may provide a route for all-transparent photoelectric devices based on the adoption of the emerging p-type $V_2O_5$ metal oxide layer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.442-443
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• 2006

Electrical, optical, surface, and structural properties of amorphous indium zinc oxide (IZO) films grown on $SiO_2$/PES/$SiO_2$ substrate by a RF sputtering in pure Ar ambient at room temperature were investigated. A sheet resistance of $13.5\;{\Omega}{\square}$, average transmittance above 85 % in 550 nm, and root mean square roughness of $10.5\;{\AA}$ were obtained even in the IZO layers grown at room temperature in pure Ar ambient. Without addition of oxygen gas during IZO sputtering process, we can obtain high quality IZO anode films from the specially synthesized oxygen rich IZO target. XRD result shows that the IZO films grown at room temperature is completely amorphous structure due to low substrate temperature. In addition, the electrical and optical properties of the flexible OLED fabricated on IZO/$SiO_2$/PES/$SiO_2$ is critically influenced by the electrical properties of a IZO anode. This findings indicate that the IZO/$SiO_2$/PES/$SiO_2$ is a promising anode/substrate scheme for realizing organic based flexible displays.

• 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 Korean institute of surface engineering
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• v.25 no.5
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• pp.271-281
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• 1992

Amorphous hydrogenated silicon carbide(a-Si1-xCx : H) films have been prepared by the rf sputtering using a silicon target in a gas mixture of Argon and methane with varying methane gas flow rate(fCH) in the range of 1.5 to 3.5 sccm at constant Argon flow rate of 30sccm and rf power in the range of 3 to 6 W/$\textrm{cm}^2$. The effects of methane flow rate and rf power on the structure and optical properties of a-Si1-xCx : H films have been analysed by measuring both the IR absorption spectrum and the UV transmittance for the films. With increasing the methane flow rate, the optical band gap(Eg) of a-Si1-xCx : H films increases gradually from 1.6eV to the maximum value of 2.42eV at rf power of 4 W/$\textrm{cm}^2$, which is due to an increases in C/Si ratio in the films by an significant increase in the number of C-Hn bonds. As the rf power increases, the number of Si-C and Si-Hn bonds increases rapidly with simultaneous reduction in the number of C-Hn bonds, which is associated with an increase in both degree of methane decomposition and sputtering of silicon. The effects of rf power on the Eg of films are considerably influenced by the methane flow rate. At low methane flow rate, the Eg of films decreased from 2.3eV to 1.8eV with the rf power. On the other hand, at high methane flow rate, that of films increased slowly to 2.4eV.

• Journal of the Semiconductor & Display Technology
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• v.9 no.3
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• pp.53-58
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• 2010

In this study, we have investigated the effect of the ambient gases on the characteristics of IZO thin films for the OLED (organic light emitting diodes) devices. For this purpose, IZO thin films were deposited by RF magnetron sputtering under various ambient gases (Ar, $Ar+O_2$ and $Ar+H_2$) at $150^{\circ}C$. In order to investigate the influences of the oxygen and hydrogen, the flow rate of oxygen and hydrogen in argon mixing gas has been changed from 0.1sccm to 0.5sccm, respectively. All the samples show amorphous structure regardless of ambient gases. The electrical resistivity of IZO film increased with increasing flow rate of $O_2$ under $Ar+O_2$ while under $Ar+H_2$ atmosphere the electrical resistivity showed minimum value near 0.5sccm of $H_2$. All the films showed the average transmittance over 85% in the visible range. The OLED device was fabricated with different IZO substrates made by configuration of IZO/${\alpha}$-NPD/DPVB/$Alq_3$/LiF/Al to elucidate the performance of IZO substrate. OLED devices with the amorphous-IZO (a-IZO) anode film show better current densityvoltage-luminance characteristics than that of OLED devices with the commercial crystalline-ITO (c-ITO) anode film. It can be explained that very flat surface roughness and high work function of a-IZO anode film lead to more efficient hole injection by reduction of interface barrier height between anode and organic layers. This suggests that a-IZO film is a promising anode materials substituting conventional c-ITO anode in OLED devices.

• Journal of the Korean institute of surface engineering
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• v.54 no.6
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• pp.302-306
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• 2021

SnO₂ 30/Ag 15/SnO₂ 30 nm(SAS) tri-layer films were deposited on the glass substrates with RF and DC magnetron sputtering and then electron beam is irradiated on the surface to investigate the effect of electron bombardment on the opto-electrical performance of the films. electron beam irradiated tri-layer films at 1000 eV show a higher figure of merit of 2.72×10^-3 Ω^-1 than the as deposited films due to a high visible light transmittance of 72.1% and a low sheet resistance of 14.0 Ω/☐, respectively. From the observed results, it is concluded that the post-deposition electron irradiated SnO₂ 30/Ag 15/SnO₂ 30 nm tri-layer films can be used as a substitute for conventional transparent conducting oxide films in various opto-electrical applications.

• The Korean Journal of Vision Science
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• v.20 no.4
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• pp.513-521
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• 2018

Purpose : : In this study, we made dopamine-functionalized hydrogels containing a cross-linked hyaluronic acid (HA) network and investigated their antioxidant activities. Methods : In the first step, we made poly hydroxyethyl methacrylate(p(HEMA))-based hydrogels post-modified with an interpenetrating polymer network(IPN) structure composed of HA polymers and a p(HEMA) network. The subsequent functionalization with dopamine via an amide coupling reaction resulted in the antioxidant hydrogels. Their antioxidant activities were evaluated using 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) and 2,2-diphenyl-1-picrylhydrazyl radical scavenging assays. Results : The dopamine-modified hydrogels exhibited significant antioxidant activities, when compared to unmodified control. The presence of the HA-IPN structure improved the surface wettability of the hydrogel while dopamine-conjugated IPN hydrogel did not demonstrate the significant difference compared to hydrogel control. Dopamine-modified hydrogels exhibited high transmittance (>88%). Conclusion : The results demonstrate that the development of antioxidant hydrogels based on dopamine-conjugated HA-IPN structures may help develop ophthalmic and biomedical materials.