• Journal of the Korean Vacuum Society
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• v.15 no.5
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• pp.534-540
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• 2006

Thin films of $V_2O_3$, $VO_2$, and $V_2O_5$ were obtained from a single precursor solution through post-annealing processes under different annealing conditions. As annealed in air, the deposited films became $V_2O_5$ with orthorhombic crystal structure, while they were $V_2O_3$ and $VO_2$ with rhombohedral and monoclinic crystal structure as annealed in vacuums with base pressure of $1{\times}10^{-6}$ Torr and with 10 mTorr $O_2$ pressure, respectively. Electrical and optical measurements indicated that the $V_2O_5$ and $VO_2$ films are semiconducting, while the $V_2O_3$ films are metallic at room temperature. Chromium doping in $VO_2$ resulted in a decrease of the resistivity and changed the conduction type from n-type to p-type. 10% Cr-doped $VO_2$ films were found to have orthorhombic crystal structure, which is different from that of the undoped $VO_2$. Spectral features in the optical absorption spectra of all the films were interpreted as the transitions involving O 2p and V 3d bands. The crystal-field splittings between $t_{2g}$ and $e_g$ states of the V 3d bands are estimated to be about 1.5 and 1.0 eV for $V_2O_5$ and $VO_2$, respectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.5
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• pp.1213-1218
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• 2013

In this study, Ga-doped ZnO (GZO) thin films were fabricated on transparent sapphire substrate by RF magnetron sputtering method and then investigated the effect of various substrate temperature on the electrical, optical properties and characteristic of crystallization of the GZO thin films. The electrical property indicated that the lowest resistivity ($4.18{\times}10^{-4}{\Omega}cm$), the highest carrier concentration ($6.77{\times}10^{20}cm^{-3}$) and Hall mobility ($22cm^2/Vs$) were obtained in the GZO thin film fabricated at $300^{\circ}C$. And for this condition, the highest c-axis orientation and (002) diffraction peak which exhibits a FWHM of $0.34^{\circ}$ were obtained. From the results of AFM measurements, it is known that the highest crystallinity is observed at $300^{\circ}C$. The transmittance spectrum in the visible range was approximately 80 % regardless of substrate temperature. The optical band-gap showed the blue-shift as increasing the substrate temperature to $300^{\circ}C$, and they are all larger than the band gap of bulk ZnO (3.3 eV). It can be explained by the Burstein-Moss effect.

• Korean Journal of Optics and Photonics
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• v.13 no.5
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• pp.455-459
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• 2002

The transport and optical properties of $In_2O_3$:Zn(IZO) thin films grown by DC magnetron sputtering deposition have been studied. The deposition temperatures ($T_s$) were varied from room temperature to $400^{\circ}C$ in $50^{\circ}C$ steps. The IZO films are an amorphous phase for $T_s$<$300^{\circ}C$ and polycrystalline phase for $350^{\circ}C$＜$T_s$. In contrast to ordinary films, amorphous IZO films have lower resistivity and higher optical transmittance than polycrystalline IZO films. The resistivity of amorphous IZO was in the range of 0.29~0.4 m$\Omega$cm and that of polycrystalline IZO was in the range of 1~4 m$\Omega$cm. The carrier type for IZO film was found to be n-type, and the carrier density, was $3~5{\times}10^{20}/cm^3$. The Hall mobility, $({\mu}_H)$, was 20~$50\textrm{cm}^2$/V.sec. The predominant scattering mechanisms in both amorphous and polycrystalline IZO films were believed to be ionized impurity scattering and lattice scattering. The visible transmittance of the IZO films, which decreases with an increase of TS, was above 80%.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.87-87
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• 2018

다이아몬드 상 탄소(diamond-like carbon, DLC)는 상당량의 $sp^3$ 결합을 가지는 비정질 탄소(a-C) 또는 수소화 비정질 탄소(a-C:H)로 이루어진 준안정 형태의 탄소이다. DLC는 전기 저항과 굴절률이 높고 화학적으로 다른 물질과 반응하지 않으며, 마찰계수가 낮고 경도가 높아 자기 디스크, 광학 소자 등의 다양한 분야에서 적용되고 있다[1,2]. 또한 다이아몬드에 비해 상온에서 성장이 가능할 정도로 합성온도가 낮아 적용 기판의 제한이 거의 없고, 증착 방법과 조건에 따라 탄소 결합의 다양성과 비정질성이 변화하기 때문에 넓은 범위의 특성을 얻을 수 있는 장점이 있다. 지금까지 DLC 박막의 광학적 특성, 특히 굴절률, 광학적인 에너지 밴드 갭, 자외선과 적외선 투과성에 대해서는 많은 연구가 진행되었으나 가시광선의 투과성에 대한 연구는 제한적이며[4], 가시광선 투과도 개선에 대한 연구는 전무하다. 본 연구에서는 ITO 기판 위에 DLC를 합성하고 기계적 특성과 가시광선 영역 투과도를 조사하였다. RF-PECVD(radio frequency plasma enhanced chemical vapor deposition) 방법에 의해서 $C_2H_2+Ar$ 혼합 가스 비율과 $C_2H_2+N_2$ 혼합 가스 비율을 변화시켜 ITO 기판 위에 DLC 박막을 합성하였다. 공정 압력과 rf-power, 증착시간, 기판온도는 0.2 torr, 40 W, 5 분, $50^{\circ}C$로 고정하고, 공정 가스는 $C_2H_2+Ar$과 $C_2H_2+N_2$가 200 sccm이 되도록 비율을 변화하였다. $C_2H_2:Ar$과 $C_2H_2:N_2$의 비율은 180 : 20, 160 : 40, 140 : 60, 120 : 80, 100 : 100이 되도록 가스의 유량을 조절하였다. 투과도는 가시광선(380 ~ 780 nm) 범위에서 측정하였고 두께와 표면조도는 AFM으로 측정하였다. 투과도는 $C_2H_2+Ar$의 Ar 가스 비율이 증가할수록 증가해 140 : 60일 때 최댓값을 나타낸 후 다시 감소하였다. $C_2H_2+N_2$ 투과도는 $N_2$ 가스 비율이 증가할수록 감소하는 경향을 나타내었다. 표면 거칠기는 $C_2H_2+Ar$ 혼합 가스를 사용한 경우의 Ar의 가스 비율이 증가할수록 증가하였다. 그러나 $C_2H_2+N_2$ 혼합 가스를 사용한 경우에는 $N_2$ 가스의 혼합 비율이 증가할수록 감소하였다.

• Applied Chemistry for Engineering
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• v.17 no.1
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• pp.28-32
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• 2006

This study investigated the variation of flow rates in microchannels that consisted of polydimethyl siloxane (PDMS) and glass using various external voltages. Three different microchannel widths and two different depths. PDMS and negative photoresist (SU-8) were used to make the microchannels by the soft lithographic method. For each depth of microchannel ($50{\mu}m$ and $100{\mu}m$), three different widths ($100{\mu}m$, $200{\mu}m$ and $300{\mu}m$) were made. In each case, several different external voltages were applied (0.3 kV, 0.35 kV, 0.4 kV and 0.45 kV) to examine the flow rates. Our results indicated that flow rate increased with an increase of the external voltage at the same microchannel width. This was because the electrical field was increased as the external voltage increased. For the same external voltage, the flow rate increased as the microchannel's width increased. These results showed that the resistance in the microchannel decreased as the microchannel's width increased. Also, to investigate the effect of microchannel's depth and width, the cross-sectional area of the microchannel was increased to the double in area. As a result, the effect of the microchannel's depth was higher at a low external voltage, and the effect of the microchannel's width was higher at a high external voltage.

• Korean Journal of Environmental Agriculture
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• v.17 no.1
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• pp.48-53
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• 1998

The purpose of this study was to compare heavy metal concentrations in uncontaminated soil with those in soil influenced by industrial activities, and to investigate the relationship between change of heavy metal content and the kind of industry at the Iksan 1st Industrial Complex that has started since 1975. Soils sampled in 0-3㎝ and 3-6㎝ soil depth, respectively were analized for content of Cd, Cu, Ni, Pb and Zn. Change of heavy metal content in soil of the industrial complex were more accumulated 16 to 25% of Cd and Cu, 93% of Pb and Zn, respectively in samples compared with natural soil uncontaminated. But there was no different in Ni content between two soil. Distribution of Cd in soil layer of 0 to 3cm was the highest concentration of 5 ppm more at the textile industries, and then higher at the chemicals and the food processing industries. In 3 to 6㎝ soil layer Cd content was the highest concentration of 5 ppm more at the metal processing industries, and then higher at the textile industries. Cd accumulation in soil was different according to a kind of industry and soil depth. Cu content was the highest value of 400 ppm more in soil layer of 0 to 3cm at the manufacturing electric wires industry area and showed the accumulation phenomenon in soil layer 3 to 6cm at the ohmmeter, machines and electric wires industry area. Ni content was 35 ppm more in soil of the metal plating and processing industries regardless of soil sampling layer. Then it was 25 ppm more in soil of the building stones and semiconductor industries. Pb content was from 400 to 1000 ppm in soil of the chemicals and textiles industries regardless of soil sampling layer. Zn content was 1200 ppm more in soil of the chemicals and silk fabrics industries regardless of soil depth, and then lower in order to soil of leather processing${\le}$metal plating industries. In conclusion, changes of heavy metal kinds and content in soil of this industrial complex area were caused by the type or kinds of industrial activities. Changes of Pb and Zn content in soil were dominated at this area.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.131-131
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• 2016

기원전 5000년 이집트에서부터 시작된 도금은 시간이 지남에 따라 점점 발전하여, 1900년대에 들어 전기를 이용한 도금공정이 개발되었고, 현재 뿌리산업으로써 각종 제조업에 널리 이용되고 있다. 도금 공정은 금속을 부식으로부터 보호하고, 제품의 심미성과 기능성, 생산성 등을 높이기 위해 주로 이용된다. 전주도금 공정은 완벽하게 동일한 형태의 생산품을 다량으로 제작 할 수 있기 때문에, 그 높은 생산성으로 주목 받고 있다. 특히, 나노/마이크로 크기의 정밀 소자 등을 가공하는 차세대 기술인 LIGA공정과 접목이 가능하다는 장점이 있다. 몰드를 이용하여 복제하는 방식인 전주 도금은 도금공정이 끝난 후 몰드와 완성된 제품을 분리해내는 추가공정이 필연적으로 발생하게 되는데, 둘 사이의 접착력을 낮추기 위하여 몰드의 표면에 이형박리제를 도포하게 된다. 이형박리제로는 전기가 잘 흐르면서 접착력이 낮은 이산화 셀렌이나 중크롬산이 주로 이용되지만, 원활한 박리를 위해서는 그 두께가 30 um 이상 확보되어야 하기 때문에 정밀한 미세구조 전주도금이 어렵다는 문제점이 있다. 또한 이와 같은 화학 약품들은 매우 유독하기 때문에 추가적인 폐수 처리 공정이 필요하며, 작업자의 안전을 위협하고 심각한 환경 오염을 초래한다는 추가적인 문제가 발생한다. 따라서, 매우 얇고 친 환경적이며 안전한 전주도금 이형박리제에 대한 연구가 요구되고 있다. 본 연구에서는 전주도금 몰드로 사용한 구리의 표면에 TCVD를 이용하여 단일 층 그래핀을 성장시킨 후, 그래핀이 코팅된 몰드에 구리를 전주도금하여 박리하였다. 박리 후 그래핀은 몰드에 손상 없이 남아있는 것을 Raman microscopy를 통해서 확인하였고, 몰드와 그래핀 사이의 접착력 (약 $0.71J/m^2$)에 비해 그래핀과 전주도금 샘플간에 낮은 접착력 (약 $0.52J/m^2$)을 갖는 것을 확인하였다. 이와 같이 낮은 접착력을 통해 박리 시 표면구조의 손상 없이 정밀한 구조의 미세 패턴구조를 형성할 수 있었다. 전주도금을 이용한 전극 형성과 고분자와의 융합을 통해 유연기판을 제작하여 bending 실험을 진행하였다. $90^{\circ}$의 bending 각도로 10000회 이하에서는 저항의 변화가 없었고, LED chip을 mounting한 후 곡률반경 4.5 mm까지 bending을 진행하여도 이상 없이 LED가 발광하는 것을 확인하였다. 위와 같은 전주도금 공정을 이용하여 고집적 전자기기, 광학기기, 센서기기 등의 다양한 어플리케이션의 부품제조에 활용될 수 있을 것으로 기대한다.

• Journal of the Korean Vacuum Society
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• v.10 no.3
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• pp.335-340
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• 2001

$Ga_2O_3$(1 wt%)-doped ZnO(GZO) thin films were grown on ${\alpha}-Al_2O_3$ (0001) by rf magnetron sputtering at $510^{\circ}C$, whose crystal structure was polycrystalline. As-grown GZO thin film shows poor electrical properties and photoluminescence (PL) spectra. To improve these properties, GZO thin films were annealed at 800-$900^{\circ}C$ in $N_2$atmosphere for 3 min. After the rapid thermal annealing(RTA), deep defect-level emission disappears and near-band emission is greatly enhanced. Annealed GZO thin films show very low resisitivity of $2.6\times10^{-4}\Omega$/cm with $3.9\times10^{20}/\textrm{cm}^3$ carrier concentration and exceptionally high mobility of 60 $\textrm{cm}^2$/V.s. These improved physical properties are explained in terms of translation of doped-Ga atoms from interstitial to substitutional site.

• Journal of the Korean Ceramic Society
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• v.39 no.10
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• pp.928-934
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• 2002

Gallium doped Zinc Oxide(GZO) films were deposited by dc magnetron sputtering using a GZO ceramic target at various conditions such as substrate temperature (RT, 400), residual water pressure ($P_{H_2O}$; 1.61${\times}10^{-4}∼2.2{\times}10^{-3}$ Pa), introduction of $H_2$ gas (8.5%) and different magnetic field strengths(250, 1000G). GZO films deposited without substrate heating showed clear degradation in film crystallinity and electrical properties with increasing $P_{H_2O}$. The resistivity increased from 3.0${\times}10^{-3}$ to 3.1${\times}10^{-2}{\Omega}㎝$ and the grain size of the films decreased from 24 to 3 nm when PH2O was increased from 1.61${\times}10^{-4}$ to 2.2${\times}10^{-3}$ Pa. However, degradation in electrical properties with increasing $P_{H_2O}$ was not observed for the films deposited with introduction of 8.5% $H_2$. When magnetic field strength of the cathode increased from 250G to 1000G, crystallinity and electrical properties of GZO films improved remarkably about all the $P_{H_2O}$. This result could be attributed to the decrease in film damage caused by the decrease in plasma impedance.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.7
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• pp.32-36
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• 2008

In this study, $In_2O_3-ZnO$ thin films are prepared on quartz substrates by the pulsed laser deposition and their optical and electrical properties are investigated as the function of substrate temperatures ($200{\sim}600^{\circ}C$) at the fixed oxygen pressure of 200 mTorr. The XRD measurement shows that polycrystalline $In_2O_3-ZnO$ thin films are formed. In the XRD measurement, the intensity of the (400) $In_2O_3$ peak at $35.5^{\circ}$ decreases and that of the (222) $In_2O_3$ peak at $30.6^{\circ}$ increases with the increase substrate temperature up to $500^{\circ}C$. From the result of AFM measurement, the morphology of $In_2O_3-ZnO$ thin films are observed as round-type grains. The lowest surface roughness (6.15 nm) is obtained for the $In_2O_3-ZnO$ thin film fabricated at $500^{\circ}C$. The optical transmittance of $In_2O_3-ZnO$ thin films are higher than 82% in the visible region. The maximum carrier concentration of $2.46{\times}10^{20}cm^{-3}$ and the minimum resistivity of $1.36{\times}10^{-3}{\Omega}cm$ are obtained also for the $In_2O_3-ZnO$ thin film fabricated at $500^{\circ}C$.