• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2004년도 춘계총회 및 연구발표회 초록집
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• pp.33.2-33.2
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• 2004

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.106.1-106.1
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• 2011

The Cu(In,Ga)Se2 (CIGS) thin film solar cells have been achieved until almost 20% efficiency by NREL. These solar cells include chemically deposited CdS as buffer layer between CIGS absorber layer and ZnO window layer. Although CIGS solar cells with CdS buffer layer show excellent performance, the short wavelength response of CIGS solar cell is limited by narrow CdS band gap of about 2.42 eV. Taking into consideration the environmental aspect, the toxic Cd element should be replaced by a different material. Among Cd-free candidate materials, the CIGS thin film solar cells with ZnS buffer layer seem to be promising with 17.2%(module by showa shell K.K.), 18.6%(small area by NREL). However, ZnS/CIGS solar cells still show lower performance than CdS/CIGS solar cells. There are several reported reasons to reduce the efficiency of ZnS/CIGS solar cells. Nakada reported ZnS thin film had many defects such as stacking faults, pin-holes, so that crytallinity of ZnS thin film is poor, compared to CdS thin film. Additionally, it was known that the hetero-interface between ZnS and CIGS layer made unfavorable band alignment. The unfavorable band alignment hinders electron transport at the heteo-interface. In this study, we focused on growing defect-free ZnS thin film and for favorable band alignment of ZnS/CIGS, bandgap of ZnS and CIGS, valece band structure of ZnS/CIGS were modified. Finally, we verified the photovoltaic properties of ZnS/CIGS solar cells.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2008년도 춘계학술대회 논문집
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• pp.29-32
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• 2008

The electron charging and degradation of anode phosphor layers are showed major problems in high electric field with anode electrode of field emission devices. An AI metal layer on the phosphor layer may get rid of these problems. This Hetero-metal-oxide phosphor layer are formed with the roughness of phosphor surface layer without interlayer and cannot be given rise to enhance the luminance efficiency. In order to enhance the brightness, an anode layer need to be flated between phosphor layer and AI metal layer in anode electrode. After optimizing the anode phosphor layer, an anode layer with AI metal and inter layer increased the brightness and luminescence efficiency 1.2 times more than only phosphor laver in anode.

• 센서학회지
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• 제15권3호
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• pp.216-221
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• 2006

ZnO thin films prepared by PLD method exhibit an excellent optical property, but may have some problems such as incomplete surface roughness and crystallinity. In this study, undoped ZnO buffer layers were deposited on (0001) sapphire substrates by ultra high vacuum pulse laser deposition (UHV-PLD) and molecular beam epitaxy (MBE) methods, respectively. After post annealing of ZnO buffer layer, undoped ZnO thin films were deposited under different oxygen pressure ($35{\sim}350$ mtorr) conditions. The Arsenic-doped (1, 3 wt%) ZnO thin layers were deposited on the buffer layer of undoped ZnO by UHV-PLD method. The optical property of the ZnO thin films was analyzed by photoluminescence (PL) measurement. The ${\theta}-2{\theta}$ XRD analysis exhibited a strong (002)-peak, which indicates c-axis preferred orientation. Field emission-scanning electron microscope (FE-SEM) revealed that microstructures of the ZnO thin films were varied by oxygen partial pressure, Arsenic doping concentration, and deposition method of the undoped ZnO buffer layer. The denser and smoother films were obtained when employing MBE-buffer layer under lower oxygen partial pressure. It was also found that higher Arsenic concentration gave the enhanced growing of columnar structure of the ZnO thin films.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.207-210
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• 2005

In order to investigate the influence of the homo buffer layer on the microstructure of the ZnO thin film, undoped ZnO buffer layer were deposited on sapphire (0001) substrates by ultra high vaccum pulsed laser deposition (UHV-PLD) and molecular beam eiptaxy (MBE). After high temperature annealing at $600^{\circ}C$ for 30min, undoped ZnO buffer layer was deposited with various oxygen pressure (35~350mtorr). On the grown layer of undoped ZnO, Arsenic-doped(l, 3wt%) ZnO layers were deposited by UHV-PLD. The optical property of the ZnO was analyzed by the photoluminescence (PL) measurement. From $\Theta-2\Theta$ XRD analysis, all the films showed strong (0002) diffraction peak, and this indicates that the grains grew uniformly with the c-axis perpendicular to the substrate surface. Field emission scanning electron microscope (FE-SEM) revealed that microstructures of the ZnO were varied with oxygen pressure, arsenic doping level, and the deposition method of undoped ZnO buffer layers. The films became denser and smoother in the cases of introducing MBE-buffer layer and lower oxygen pressure during As-doped ZnO deposition. Higher As-doping concentration enhanced the columnar-character of the films.

• 센서학회지
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• 제11권3호
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• pp.155-162
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• 2002

CO 기체 감지 특성을 향상시키기 위해서 3 mol% ZnO를 첨가한 $SnO_2$와 3mol% $SnO_2$를 첨가한 ZnO의 적층 형태를 변화시켜 연구하였다. 적층 구조는 단일층, 복층, 그리고 이종층 구조로 후막 인쇄법을 사용하여 제작하였다. $SnO_2$-ZnO계에서 제 2상은 발견되지 않았다. 전도성은 $SnO_2$에 ZnO를 첨가하면 감소하고, ZnO에 $SnO_2$를 첨가하면 증가하였다. 측정 온도증가와 CO 기체 유입으로 전도성은 증가하였다. 단층 및 복층의 후막센서 구조의 감도 향상은 없었으나, $SnO_2$ 3ZnO-ZnO $3SnO_2$/substrate 구조의 이종층 센서의 감도는 향상되었다. 센서 구조에 관계없이 I-V 변화는 모두 직선성을 나타내서 Ohmic 접합 특성을 이루고 있었다.

• 전자공학회논문지
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• 제54권6호
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• pp.25-29
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• 2017

본 논문에서는 듀로이드와 FR4를 기판으로 하는 재배선층 위에 정전 구동 방식의 RF MEMS 스위치와 승압 DC-DC 컨버터를 결합하는 연구를 진행하였다. 상용 PCB(Printed Circuit Board) 공정으로 듀로이드와 GCPW 전송 선로 조합의 재배선층과 FR4와 CPW 전송 선로 조합의 재배선층을 제작하였다. 상용 PCB 공정 특성에 의하여 전송 선로의 특성 임피던스는 56옴, 59옴 이었으며 이에 대하여 비교 분석하였다. 듀로이드 기판은 유전상수가 작고 두께가 얇으며 GCPW를 적용하였기 때문에 상대적으로 유전상수가 크고 두께가 두꺼우며 CPW 전송 선로를 적용한 FR4 기판보다 6GHz 대역에서 삽입 손실은 약 2.08dB, 반사 손실은 약 3.91dB, 신호 분리도는 약 3.33dB 우수한 것을 확인하였다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1998년도 IUMRS-ICEM ABSTRACT BOOK
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• pp.119.4-119
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• 1998

• Applied Science and Convergence Technology
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• 제26권3호
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• pp.52-54
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• 2017

An InGaN/GaN multiple quantum well (MQW) structure is grown on a GaN/sapphire template using a plasma-assisted molecular beam epitaxy (PA-MBE). The fluctuation of the quantum well thickness formed from roughly-grown InGaN layer results in a disordered photoluminescence (PL) spectrum. The surface morphologies of the InGaN layers with various In compositions are investigated by reflection high energy electron diffraction (RHEED) and atomic force microscopy (AFM). A blurred InGaN/GaN hetero-interface and the non-uniform QW size is confirmed by high resolution transmission electron microscopy (HR-TEM). Inhomogeneity of the quantum confinement results in a degradation of the quantum efficiency even though the InGaN layer has a uniform In composition.

• 한국결정성장학회지
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• 제9권2호
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• pp.162-167
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• 1999

3가지 방향성을 가진 사파이어 기판 위에 GaN 박막을 OMVPE방식으로 증착시켜 증착된 GaN epilayer를 투과전자현미경으로 분석하여 각 미세구조의 차이를 비교분석하였다. 3 가지 방향 모두에서 GaN 증착층이 관찰되어졌으며 그중 가장 좋은 경계면의 상태와 단일결정성을 보여준 것은 사파이어{0001} 방향의 기판을 사용한 경우였다. 결함들도 {0001} 방향의 기판을 사용한 경우에서 가장 적게 나타났다. 모든 경우에서 buffer layer는 발견되어지지 않았고 그럼에도 불구하고 경계면에서의 격자 뒤틀림이 일어나는 지역이 수 나노미터(nanometer) 정도밖에 안되는 우수한 경계면들이 관찰되었다. 따라서 일반적으로 GaN 박막 증착시에 가장 많이 사용되는 사파이어 basal plane 외에도 결함이 많기는 하지만, {1120}와 {1102} plane 위에도 GaN 증착층이 buffer layer 없이 증착 될 수 있다는 사실을 TEM 관찰을 통하여 알 수 있었으며 사파이어 {0001}면를 기판으로 사용한 경우에 미세구조 측면에서 볼 때 hetero-epitaxial한 GaN 박막층을 얻을 수 있는 것을 확인하였다.