• 한국재료학회지
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• 제25권12호
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• pp.708-712
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• 2015

This study reports the effects of $H_2S$ gas concentration on the properties of $Cu_2ZnSnS_4(CZTS)$ thin films. Specifically, sulfurization process with low $H_2S$ concentrations of 0.05% and 0.1%, along with 5% $H_2S$ gas, was studied. CZTS films were directly synthesized on Mo/Si substrates by chemical bath deposition method using copper sulfate, zinc sulfate heptahydrate, tin chloride dihydrate, and sodium thiosulfate pentahydrate. Smooth CZTS films were grown on substrates at optimized chemical bath deposition condition. The CZTS films sulfurized at low $H_2S$ concentrations of 0.05 % and 0.1% showed very rough and porous film morphology, whereas the film sulfurized at 5% $H_2S$ yielded a very smooth and dense film morphology. The CZTS films were fully crystallized in kesterite crystal form when they were sulfurized at $500^{\circ}C$ for 1 h. The kesterite CZTS film showed a reasonably good room-temperature photoluminescence spectrum that peaked in a range of 1.4 eV to 1.5 eV, consistent with the optimal bandgap for CZTS solar cell applications.

• 한국전기전자재료학회논문지
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• 제27권7호
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• pp.472-476
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• 2014

We report the characteristics of thin-film transistor (TFT) to make the bi-channel structure with stacked $Mg_{0.1}Zn_{0.9}O$ (Mg= 10 at.%) and ZnO. The ZnO and $Mg_{0.1}ZnO_{0.9}O$ thin films were deposited by radio frequency (RF) co-sputter system onto the thermally oxidized silicon substrate. A total thickness of active layer was 50 nm. Firstly, the ZnO thin films were deposited to control the thickness from 5 nm to 30 nm. Sequentially, the $Mg_{0.1}ZnO_{0.9}O$ thin films were deposited to change from 45 nm to 20 nm. The bi-layer TFT shows more improved properties than the single layer TFT. The field effect mobility and subthreshold slope for $Mg_{0.1}ZnO_{0.9}O$/ZnO-TFT are $7.40cm^2V^{-1}s^{-1}$ and 0.24 V/decade at the ZnO thickness of 10 nm, respectively.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.160-162
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• 2003

ZnO epilayer were synthesized by the pulesd laser deposition(PLD) process on $Al_2O_3$ substrate after irradiating the surface of the ZnO sintered pellet by the ArF(193nm) excimer laser. The substrate temperatures was $400^{\circ}C$. The crystalline structure of epilayer was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of ZnO epilayer measured with Hall effect by van der Pauw method are $8.27{\times}10^{16}\;cm^{-3}\;and\;299\;cm^2V{\cdot}s$ at 293 K, respectively. The temperature dependence of the energy band gap of the ZnO obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)\;=\;3.3973\;eV\;-\;(2.69{\times}10^{-4}\;eV/K)T^2/(T\;+\;463K)$. After the as-grown ZnO epilayer was annealed in Zn atmospheres, oxygen and vaccum the origin of point defects of ZnO atmospheres has been investigated by the photoluminescence(PL) at 10 K. The native defects of $V_{Zn}$, Vo, $Zn_{int}$, and $O_{int}$ obtained by PL measurements were classified as a donors or accepters type.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 C
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• pp.1523-1525
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• 2003

Due to the rapid development of wireless networking system, researches on the communication devices are mainly focus on microwave frequency devices such as filters, resonators, and phase shifters. Among them, Film bulk acoustic resonator (FBAR) has been paid extensive attentions for their high performance. In this research, ZnO thin films were deposited by RF-magnetron sputtering on Al/$SiO_2$/Si wafer and then crystalline properties and surface morphology were examined. To measure crystalline structure and surface morphology X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) were employed. It was showed that crystalline properties of ZnO thin films were strongly dependant on the deposition conditions. As increasing the deposition temperature and the deposition pressures, the peak intensities of ZnO(002) plane were increased until $300^{\circ}C$, then decreased rapidly. At the sputtering conditions of RF power of 213 W and working pressure of 15 m Torr, ZnO film had excellent c-axis orientation, surface morphology, and adhesion to the substrate. In conclusion we optimized smooth surface with very small grains as well as highly c-axis oriented ZnO film for FBAR applications.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.676-677
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• 2006

Synthesis of zinc oxide nanorods, sheets and flower like structure were done by the sol-gel method using zinc acetate dihydrate and sodium hydroxide at $80^{\circ}C$ with 12 hours refluxing time nanorods, in case of as synthesized powder, with diameter of 20-60nm. Annealing at higher temperature (300 and $500^{\circ}C$,) in air ambient changes the morphology to sheet and flower like structure. The standard peak of zinc oxide was observed in IR at $523cm^{-1}$. The UV-VIS spectroscopy of zinc oxide shows a characteristic peak at 375nm.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 춘계학술대회 논문집 디스플레이 광소자 분야
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• pp.127-130
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• 2005

The properties of phosphorus doped ZnO multilayer thin films deposited on (001) sapphire substrates by pulsed laser deposition (PLD) were investigated by using annealing treatment at various annealing temperature after deposition. The phosphorus doped ZnO multilayer was composed of phosphorus doped ZnO layer and two pure ZnO layers on sapphire substrate. The structural. electrical and optical properties of the ZnOthin films were measured by X-ray diffraction (XRD). Hall measurements and photoluminescence (PL). As the annealing temperature optimized. the electrical properties of the ZnO multilayer showed a electron concentration of $1.56{\times}10^{16}/cm^3$, a resistivity of 17.97 ${\Omega}cm$. It was observed the electrical property of the film was changed by dopant activation effect as thermal annealing process

• 한국전자통신학회논문지
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• 제15권4호
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• pp.665-670
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• 2020

CIGS 박막 태양 전지의 버퍼층은 흡수층과 윈도우층 사이의 밴드정렬(band alignment)을 통해 에너지 변환 효율을 향상시킨다. ZnS는 무독성의 II-VI 반도체 화합물로서 직접천이형 광대역 밴드갭과 n형 전도성을 가지며, 높은 광투과성, 높은 굴절률 등의 우수한 전기적, 광학적 특성을 가지고 있고, 우수한 격자정합을 가지는 물질이다. 이 연구에서, RF 마그네트론 스퍼터링 방법에 의해 증착 후 급속 열처리에 의해 제작된 ZnS 버퍼층 박막의 구조적, 광학적 특성의 상관관계에 대해 고찰하였다. (111), (220), (311) 면의 섬아연광 입방정 구조를 확인할 수 있고, 상대적으로 저온에서 급속열처리를 수행한 시료에서는 (002) 면의 우르쯔광 육방정 구조가 함께 나타나는 다결정이 되었다. 고온에서 급속열처리 수행한 시료에서는 섬아연광 입방정 구조의 단결정으로 상전이 된다. 화학적 성분 분석을 통해서 Zn/S의 비율이 화학양론에 근접한 시료에서 섬아연광 입방정 구조의 단결정이 나타났음을 확인하였다 급속열처리 온도가 증가할수록 흡수단이 다소간 단파장 쪽으로 이동되고, 가시광 파장 범위에서 평균 광투과율이 증가하는 경향성을 보이며 500℃ 조건에서는 80.40%로 향상되었다.

• KEPCO Journal on Electric Power and Energy
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• 제2권1호
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• pp.97-101
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• 2016

산화아연은 다양한 나노 구조와 특유의 특성으로 인하여 여러 분야에서 많은 관심을 받고있는 물질이다. 산화아연을 합성하는 다양한 방법 중에서, 수열합성법은 간단하고 친환경적인 장점을 가지고 있다. 나노 구조를 가지는 산화아연 박막은 수열합성법을 통하여 FTO 전극 위에 제작되었다. 성장된 산화아연은 X-ray diffraction (XRD)와 Field-emission scanning electron microscopy (FESEM)을 통하여 분석되었다. XRD 분석에서 산화아연 박막이 자연상태의 hexagonal wurtzite 상으로 구성되어 있음을 확인하였으며 SEM 사진에서는 나노 로드 형태를 구성하고 있는 것을 확인할 수 있었다. 본 연구에서는 UV 영역의 흡수 스펙트럼을 분석하여 산화아연이 보이는 365 nm 파장에서의 흡수를 확인하였다. 또한 photoluminescence 방출을 분석한 결과, 424 nm의 band edge emission과 500 nm에서 산화아연의 oxygen vacancies에 의한 방출을 확인하였다. 또한 라만 스펙트럼 분석을 통하여 본 연구진이 제작한 산화아연이 높은 결정성을 가지고 있는 것을 확인할 수 있었다. 이러한 연구를 통하여 다양한 특성을 가진 산화아연의 광촉매적 적용을 기대할 수 있다.

• 반도체디스플레이기술학회지
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• 제9권4호
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• pp.77-81
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• 2010

The AZO thin films were deposited on the corning 1737 glass plate by the RF magnetron sputtering and effects of working pressure and oxygen contents on the electrical properties were investigated. XRD spectra showed a preferred orientation along the c-axis and a minimum FWHM for the 70mTorr. From the surface analysis (AFM), the number of crystal grain of AZO thin film increased as working pressure increased. The film deposited with 70mTorr of working pressure showed n-type semiconductor characteristic having suitable resistivity $-1.59{\times}10^{-2}{\Omega}cm$, carrier concentration $-10.1{\times}10^{19}cm^{-3}$, and mobility $-4.35cm^2V^{-1}s^{-1}$ while other films by 7 mTorr, 20 mTorr of working pressure closed to metallic films. The films including the oxygen represent stoichiometric composition similar to the oxide. The transmittance of the film was over 85% in the visible light range regardless of the changes in working pressure and oxygen contents.

• 한국재료학회지
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• 제29권9호
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• pp.553-558
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• 2019

$Cu_2ZnSn(S,Se)_4(CZTSSe)$ thin film solar cells areone of the most promising candidates for photovoltaic devices due to their earth-abundant composition, high absorption coefficient and appropriate band gap. The sputtering process is the main challenge to achieving high efficiency of CZTSSe solar cells for industrialization. In this study, we fabricated CZTSSe absorbers on Mo coated soda lime glass using different pressures during the annealing process. As an environmental strategy, the annealing process is performed with S and Se powder, without any toxic $H_2Se$ and/or $H_2S$ gases. Because CZTSSe thin films have a very narrow stable phase region, it is important to control the condition of the annealing process to achieve high efficiency of the solar cell. To identify the effect of process pressure during the sulfo-selenization, we experiment with varying initial pressure from 600 Torr to 800 Torr. We fabricate a CZTSSe thin film solar cell with 8.24 % efficiency, with 435 mV for open circuit voltage($V_{OC}$) and $36.98mA/cm^2$ for short circuit current density($J_{SC}$), under a highest process pressure of 800 Torr.