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반응성 이온 식각법에 의해 제작된 탄소나노튜브 전극의 전기화학적 특성
황숙현,최현광,김상효,한영문,전민현,Hwang, Sook-Hyun,Choi, Hyon-Kwang,Kim, Sang-Hyo,Han, Young-Moon,Jeon, Min-Hyon 한국재료학회 2011 한국재료학회지 Vol.21 No.2
In this work, fabrication and electrochemical analysis of an individual multi-walled carbon nanotube (MWNT) electrode are carried out to confirm the applicability of electrochemical sensing. The reactive ion etching (RIE) process is performed to obtain sensitive MWNT electrodes. In order to characterize the electrochemical properties, an individual MWNT is cut by RIE under oxygen atmosphere into two segments with a small gap: one segment is applied to the working electrode and the other is used as a counter electrode. Electrical contacts are provided by nanolithography to the two MWNT electrodes. Dopamine is specially selected as an analytical molecule for electrochemical detection using the MWNT electrode. Using a quasi-Ag/AgCl reference electrode, which was fabricated by us, the nanoelectrodes are subjected to cyclic voltammetry inside a $2{\mu}L$ droplet of dopamine solution. In the experiment, RIE power is found to be a more effective parameter to cut an individual MWNT and to generate "broken" open state, which shows good electrochemical performance, at the end of the MWNT segments. It is found that the pico-molar level concentration of analytical molecules can be determined by an MWNT electrode. We believe that the MWNT electrode fabricated and treated by RIE has the potential for use in high-sensitivity electrochemical measurement and that the proposed scheme can contribute to device miniaturization.
투명전극 응용을 위한 ZnO박막과 Ga 도핑 된 ZnO박막의 성장 후 열처리에 따른 특성분석
장재호,배효준,이지수,정광현,최현광,전민현,Jang, Jae-Ho,Bae, Hyo-Jun,Lee, Ji-Su,Jung, Kwang-Hyun,Choi, Hyon-Kwang,Jeon, Min-Hyon 한국전기전자재료학회 2009 전기전자재료학회논문지 Vol.22 No.7
Polycrystalline ZnO and Ga doped ZnO (GZO) films are deposited on glass substrate by RF magnetron sputtering at room temperature. The characteristics of ZnO and GZO films are investigated with X-ray diffraction measurement, UV-VIS-NIR spectrophotometer $(250{\sim}1200nm)$ and hall measurement. The post-growth thermal treatment of these films is carried out in N2 ambient at $500^{\circ}C$ for 30 min and an hour. ZnO and GZO films have different changing behavior of structural and optical properties by annealing. To use transparent conductive films for solar cell, films should have not only high transmittance but also good electrical property. Although as deposited GZO films have electrical properties than ZnO films, GZO films have not good transmittance properties. Consequently, we succeed that the high transmittance of GZO films is improved by annealing process.
텐덤형 태양전지를 위한 InAs 다중 양자점과 InGaAs 다중 양자우물에 관한 연구
조중석,김상효,황보수정,장재호,최현광,전민현,Cho, Joong-Seok,Kim, Sang-Hyo,HwangBoe, Sue-Jeong,Janng, Jae-Ho,Choi, Hyon-Kwang,Jeon, Min-Hyon 한국진공학회 2009 Applied Science and Convergence Technology Vol.18 No.5
본 연구에서는 1.1 eV의 에너지대역을 흡수할 수 있는 InAs 양자점구조와 1.3 eV의 에너지 대역을 흡수 할 수 있는 InGaAs 양자우물구조를 이용한 텐덤형 태양전지의 구조를 1D poisson을 이용해 설계하고, 분자선 에피택시 장비를 이용하여 각각 5, 10, 15층씩 쌓은 양자점 및 양자우물구조를 삽입하여 p-n접합을 성장하였다. Photoluminescence (PL) 측정을 이용한 광학적특성 평가에서 양자점 5층 및 양자우물 10층을 삽입한 구조의 PL 피크가 가장 높은 상대발광강도를 나타냈으며, 각각 1.1 eV 및 1.3 eV에서 57.6 meV 및 12.37 meV의 Full Width at Half Maximum을 나타내었다. 양자점의 밀도 및 크기는 Reflection High-Energy Electron Diffraction system과 Atomic Force Microscope를 이용해 분석하였다. 그리고 GaAs/AlGaAs층을 이용한 터널접합에서는 I-V 측정을 통하여 GaAs층의 두께(20, 30, 50 nm)에 따른 터널링 효과를 평가하였다. GaAs 층의 두께가 30 nm 및 50 nm의 터널접합에서는 backward diode 특성을 나타낸 반면, 20 nm GaAs층의 GaAs/AlGaAs 터널접합에서는 다이오드 특성 곡선을 확인하였다. The InAs multi-quantum dots (MQDs) solar cell and InGaAs multi-quantum wells (MQWs) solar cell to cover 1.1 eV and 1.3 eV were designed by 1D poisson, respectively. The MQDs and MQWs of 5, 10, 15 layers were grown by molecular beam epitaxy. The photo luminescence results showed that the 5 period stacked MQDs have the highest intensity at around 1.1 eV with 57.6 meV full width at half maximum (FWHM). Also we can observe 10 period stacked MQWs peak position which has highest intensity at 1.31 eV with 12.37 meV FWHM. The density and size of QDs were observed by reflection high energy electron diffraction pattern and atomic force microscope. Futhermore, AlGaAs/GaAs sandwiched tunnel junctions were modified according to the width of GaAs layer on p-type GaAs substrates. The structures with GaAs width of 30 nm and 50 nm have backward diode characteristics. In contrast, tunnel diode characteristics were observed in the 20 nm of that of sample.
염료감응형 태양전지의 탄소나노튜브 상대전극의 광투과도와 전기화학적 특성이 에너지 변환 효율에 미치는 영향
한영문,황숙현,강명훈,김영주,김현국,김상효,배효준,최현광,전민현,Han, Young-Moon,Hwang, Sook-Hyun,Kang, Myung-Hoon,Kim, Young-Joo,Kim, Hyun-Kook,Kim, Sang-Hyo,Bae, Hyo-Jun,Choi, Hyon-Kwang,Jeon, Min-Hyon 한국전기전자재료학회 2011 전기전자재료학회논문지 Vol.24 No.4
In this work, electrochemical characteristics and optical transmittance of carbon nanotubes (CNTs) counter electrodes which had different amount of CNTs in CNTs slurries were analyzed. Two-step heat treatment processes were applied to achieve well-fabricated CNTs electrode. Three sets of CNTs electrodes and dye-sensitized solar cells (DSSCs) with CNTs counter electrodes were prepared. As the amount of CNTs increased, sheet resistance of CNTs electrode decreased. CNTs electrode with low sheet resistance had low electrochemical impedance and fast redox reaction. On the other hand, in case of CNTs counter electrode with low density of CNTs, performance of the dye-sensitized solar cell was improved due to its high optical transmittance. We found that the transmittance of CNTs counter electrode influence the performance of dye-sensitized solar cells.
아연을 코팅한 테프론 기판 위에 성장된 산화아연 박막의 후열처리 효과
김익현 ( Ik Hyun Kim ),남기웅 ( Gi Woong Nam ),이철언 ( Cheol Eon Lee ),김동완 ( Dong Whan Kim ),최현광 ( Hyon Kwang Choi ),김양수 ( Yang Soo Kim ),김진수 ( Jin Soo Kim ),김종수 ( Jong Su Kim ),손정식 ( Jeong-sik Son ),임재영 ( Ja 대한금속재료학회(구 대한금속학회) 2015 대한금속·재료학회지 Vol.53 No.6
ZnO thin films were first grown on Zn-coated Teflon substrates using a spin-coating method, with various post-heating temperatures. The structural and optical properties of the ZnO thin films were then investigated using field-effect scanning-electron microscopy, X-ray diffractometry, and photoluminescence (PL) spectroscopy. The surface morphology of these ZnO thin films exhibited dendritic structures. With increasing post-heating temperature, all samples preferentially exhibited preferential c-axis orientation and increased residual tensile stress. All of the films exhibited preferential c-axis orientation, and the residual tensile stress of those increased with increasing post-heating temperature. The near-band-edge emission (NBE) peaks were red-shifted after post-heating treatment at 400 ℃. The intensity of the deep-level emission (DLE) peaks gradually decreased with increasing post- heating temperature. Moreover, the narrowest ‘full width at half maximum’ (FWHM) and the highest intensity ratio of the NBE to the DLE for thin films, were observed after post-heating at 400 ℃. The ZnO thin films fabricated with the 400 ℃ post-heating process provided the highest crystallinity and optical properties.(Received March 04, 2014)