• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1412-1413
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• 2011

Effects of thermal annealing on electrical characteristics of thin film transistors (TFTs) using hydrogenated zinc oxide (ZnO:H) films as active channel were extensively investigated. The ZnO:H films were deposited at room temperature by RF sputtering. The device parameters of the ZnO:H-based TFTs, such as threshold voltage ($V_{th}$), subthreshold swing (S.S.), and on-off current ratio ($I_{on}/I_{off}$), were characterized in terms of the annealing temperature as well as the gas flow ratio of $H_2$/Ar.

• Transactions on Electrical and Electronic Materials
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• 제13권1호
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• pp.6-9
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• 2012

In this study, we carried out an investigation of the etching characteristics (etch rate, selectivity to $SiO_2$) of ZnO thin films in $N_2/Cl_2$/Ar inductivity coupled plasma. A maximum etch rate and selectivity of 108.8 nm/min and, 3.21, respectively, was obtained for ZnO thin film at a $N_2/Cl_2$/Ar gas mixing ratio of 15:16:4 sccm. The plasmas were characterized by optical emission spectroscopy. The x-ray photoelectron spectroscopy analysis showed the efficient destruction of oxide bonds by ion bombardment. An accumulation of low volatile reaction products on the etched surface was also shown. Based on this data, an ion-assisted chemical reaction is proposed as the main etch mechanism for plasmas containing $Cl_2$.

• 한국표면공학회지
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• 제37권5호
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• pp.263-272
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• 2004

High strength steels such as transformation induced plastic steel, dual phase and solid solution Hardening have been developed and continuously improved due to the intensified needs in the automotive industry. But silicon and manganese in transformation induced plastic steels were known to exhibit harmful effects on galvannealing reaction by oxide film formed during heat treatment. Therefore, in this work, the applicability of Zn-Ni electrodeposition instead of hot dip galvannealed coating to transformation induced plastic steels was evaluated and optimum electroplating condition was investigated. Based on these investigations optimized electroplating conditions were proposed and Zn-Ni electrogalvanized steel sheet was produced by EGL (electrogalvanized line). Its perfomance properties for automotive steel was evaluated.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 추계학술대회
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• pp.451-454
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• 2006

WGS reaction over Mo2C and ceria based catalysts was investigated to develop an alternative commercial Cu-Zn/Al2O3 catalyst for fuel processor and hydrogen station. The Mo2C catalysts were prepared by a temperature programmed method and the various metal supported cerium oxide catalysts were prepared by an Impregnation method. The catalysts were characterized by the N2 physisorption, Co chemisorption, XRD, TEM and TPR. It was found that Mo2C and 0.2wt% Pt-40wt%, Ni/CeO2 catalysts had higher activity and stability than the Cu-Zn/Al203 above $260^{\circ}C$. Moreover, CO conversion of more than 85% was observed at $280{\sim}300^{\circ}C$. But all catalysts were deactivated during the thermal cycling runs. The results suggest that these catalysts are an attractive candidate for the alternative Cu-Zn/Al2O3 catalyst for fuel processor and hydrogen station applications.

• 한국전기전자재료학회논문지
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• 제35권1호
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• pp.80-85
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• 2022

ZnO-based transparent conductive films have been widely studied to achieve high performance optoelectronic devices such as next generation flexible and transparent display systems. In order to achieve a transparent flexible ZnO-based device, a low temperature growth technique using a flexible polymer substrate is required. In this work, high quality flexible ZnO films were grown on colorless polyimide substrate using atomic layer deposition (ALD). Transparent ZnO films grown from 80 to 200℃ were fabricated with a metal-semiconductor-metal structure photodetectors (PDs). As the growth temperature of ZnO film increases, the photocurrent of UV PDs increases, while the sensitivity of that decreases. In addition, it is found that the response times of the PDs become shorter as the growth temperature increases. Based on these results, we suggest that high-quality ZnO film can be grown below 200℃ in an atomic layer deposition system, and can be applied to transparent and flexible UV PDs with very fast response time and high photocurrent.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 추계학술발표대회
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• pp.3.2-3.2
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• 2011

Nanofibers, one of various one-dimensional nanomaterials such as nanorods, nanowires and nanotubes have been successfully synthesized by many groups in recent years and their applications to chemical sensors, catalytic filters and biomedicine, etc. are extensively tested. In particular, there is a possibility that chemical sensors based on oxide nanofibers can overcome the shortcomings of chemical sensors based on single nanowires. In order to prepare oxide nanofibers, the electrospinning method is most widely used. In this work, we synthesized various oxide nanofibers including ZnO, SnO2 and CuO by employing an electrospinning method and various shapes of nanofibers including core-shell nanofibers and hollow nanofibers as well. The response properties of the various nanofibers to oxidizing and reducing gaseous species have been investigated systematically. The normal oxide nanofibers showed high sensitivity and quite fast response time to many gaseous species. Furthermore, derivatives of normal nanofibers including hollow nanofibers, core-shell nanofibers and heterostructured nanofibers display much superior sensing properties. These results hold promise for the practical application of oxide nanofibers to chemical sensors. In addition, the sensing mechanisms operated in the nanofibers will be discussed in detail.

• Journal of Information Display
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• 제11권4호
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• pp.165-168
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• 2010

A solution-processed multicomponent oxide, yttrium hafnium zinc oxide (YHZO), was synthesized and deposited as a gate insulator. The YHZO film annealed at $600^{\circ}C$ contained an amorphous phase based on the results of thermogravimetry, differential thermal analysis, and X-ray diffraction. The electrical characteristics of the YHZO film were analyzed by measuring the leakage current. The high dielectric constant (16.4) and high breakdown voltage (71.6 V) of the YHZO films resulted from the characteristics of $HfO_2$ and $Y_2O_3$, respectively. To examine if YHZO can be applied to thin-film transistors (TFTs), indium gallium zinc oxide TFTs with a YHZO gate insulator were also fabricated. The desirable characteristics of the YHZO films when used as a gate insulator show that the limitations of the general binary-oxide-based materials and of the conventional vacuum processes can be overcome.

• KIEE International Transactions on Electrophysics and Applications
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• 제5C권3호
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• pp.131-137
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• 2005

This paper describes a new approach to the algorithm and fundamental characteristics of the device for monitoring the leakage currents flowing through zinc oxide (ZnO) surge arresters. In order to obtain a technique for a new on-line monitoring device that can be used in the deterioration diagnosis of ZnO surge arresters, the new algorithm and on-line leakage current detection device for extracting the resistive and capacitive currents using the phase shift addition method were proposed. The computer-based on-line monitoring device can sense accurately the power frequency leakage currents flowing through ZnO surge arresters. The on-line leakage current monitoring device of ZnO surge arresters proposed in this work has the high sensitivity compared to the third harmonic leakage current detection devices. As a consequence, it was found that the proposed leakage current monitoring device would be useful for forecasting the defects and degradation of ZnO surge arresters.

• Composites Research
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• 제29권4호
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• pp.132-137
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• 2016

Based on mussel-inspired polydopamine (PDA), a novel technique to fabricate carbon nanowire (CNW) arrays is presented for a possible use of porous carbon electrode in electrochemical energy storage applications. PDA can give more porosity and nitrogen-doping effect to carbon electrodes, since it has high graphitic carbon yield characteristic and rich amine functionalities. Using such outstanding properties, the applicability of PDA for electrochemical energy storage devices was investigated. To achieve this, the decoration of the CNW arrays on carbon fiber surface was performed to increase the surface area for storage of electrical charge and the chemical active sites. Here, zinc oxide (ZnO) nanowire (NW) arrays were hydrothermally grown on the carbon fiber surface and then, PDA was coated on ZnO NWs. Finally, high temperature annealing was performed to carbonize PDA coating layers. For higher energy density, manganese oxide ($MnO_x$) nanoparticles (NPs), were deposited on the carbonized PDA NW arrays. The enlarged surface area induced by carbon nanowire arrays led to a 4.7-fold enhancement in areal capacitance compared to that of bare carbon fibers. The capacitance of nanowire-decorated electrodes reached up to $105.7mF/cm^2$, which is 59 times higher than that of pristine carbon fibers.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.251-251
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• 2011

본 연구에서는 Zr이 도핑 된 ZnSnO (ZZTO) 기반의 물질을 액상공정을 이용하여 합성하고, 박막트랜지스터를 제작하였다. 출발 물질로써 지르코늄 클로라이드 (ZrCl4), 아연 아세테이트 디하이드레이트 ($Zn(CH_3COO)_2{\cdot}2H_3O$), 틴 클로라이드 ($SnCl_2$)를 아연과 주석 프리커서의 비율을 4:7로 고정하고, 지르코늄 프리커서의 몰비를 변형시켜 제작하였다. 제작된 솔루션은 0.25몰의 몰 농도로 고정하였다. 솔벤트로는 2-메톡시에탄올 (2-methoxyethanol)을 사용하였으며, 준비된 솔루션은 $0.2{\mu}m$ 필터를 이용하여 필터링을 실시하였다. Heavily doped p+ Si 기판에 열적 산화법을 이용하여 120 nm 두께의 $SiO_2$를 성장시킨 것을 게이트 및 게이트 절연막으로 이용하였으며, 스핀코팅을 이용하여 ZZTO 박막을 코팅하였다. 코팅 된 기판은 $300^{\circ}C$에서 $500^{\circ}C$ 사이로 2시간 열처리를 실시하였으며, 마지막으로 소오스/드레인을 스퍼터링법으로 Al을 증착하였다. Zr 함량비, 열처리 온도, 제작된 솔루션의 온도에 따른 박막단계를 파악하기 위해 X-ray photoelectron spectroscopy (XPS), thermogravimetry differential thermal analyzer (TG-DTA), X-ray diffractometer (XRD), high-resolution transmission electron microscopy (HR-TEM), Hall-effect measurement, UV-Vis spectroscopy 분석을 실시하였으며, 제작된 소자는 semiconductor analyzer (HP4156C)를 이용하여 측정하였다.