• Transactions on Electrical and Electronic Materials
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• 제15권6호
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• pp.315-319
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• 2014

In this paper, we investigate visible light stress instability in radio frequency (RF) sputtered a-IGZO thin film transistors (TFTs). The oxygen flow rate differs during deposition to control the concentration of oxygen vacancies, which is confirmed via RT PL. A negative shift is observed in the threshold voltage ($V_{TH}$) under illumination with/without the gate bias, and the amount of shift in $V_{TH}$ is proportional to the concentration of oxygen vacancies. This can be explained to be consistent with the ionization oxygen vacancy model where the instability in $V_{TH}$ under illumination is caused by the increase in the channel conductivity by electrons that are photo-generated from oxygen vacancies, and it is maintained after the illumination is removed due to the negative-U center properties.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.387-390
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• 2002

This paper presents deposition and characterizations of microcrystalline silicon(${\mu}$c-Si:H) films prepared by hot wire chemical vapor deposition at substrate temperature below 300$^{\circ}C$. The SiH$_4$ concentration[F(SiH$_4$)/F(SiH$_4$).+(H$_2$)] is critical parameter for the formation of Si films with microcrystalline phase. At 6% of silane concentration, deposited intrinsic ${\mu}$c-Si:H films shows sufficiently low dark conductivity and high photo sensitivity for solar cell applications. P-type ${\mu}$c-S:H films deposited by Hot-Wire CVD also shows good electrical properties by varying the rate of B$_2$H$\_$6/ to SiH$_4$ gas. The solar cells with structure of Al/nip ${\mu}$c-Si:H/TCO/g1ass was fabricated with single chamber Hot-Wire CVD. About 3% solar efficiency was obtained and applicability of HWCVD for thin film solar cells was proven in this research.

• 한국세라믹학회지
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• 제48권2호
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• pp.200-204
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• 2011

Increase of surface area and decrease of band gap in $TiO_2$ semiconductors are significant to improve the efficiency of water splitting by photoelectrolysis. In this study $TiO_2$ nanotube arrays with ~7 um length and ~100 nm diameter were fabricated by an anodizing technique of titanium foils using DMSO (dimethyl sulfoxide)-based electrolytes. Then to control the band gap of the $TiO_2$ arrays, they were annealed at $550^{\circ}C$ for up to 180 min in $NH_3$ gas ambient. The samples annealed in $NH_3$ gas for 30 min and 60 min showed superior photo-conversion efficiency for water splitting under white and visible light. A $TiO_2$ nanotube annealed in $NH_3$ gas ambient for a period longer than 120 min showed 1 order higher leakage current. It is believed that the decrease of band gap and increase of conductivity in $TiO_2$ nanotube arrays due to $NH_3$ gas treatments result in the superior water-splitting performance.

• 한국인쇄학회지
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• 제29권1호
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• pp.23-33
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• 2011

This experimental focus to characterize luminescence properties related to CNT (Carbon Nano Tube) element dispersedly implanted in ZnS-based phosphor thin film panel fabricated by a screen printing method. More specifically FE-SEM measurements, L-V(Luminescence vs. Voltage) and photo luminescence were carried out to determine an optimum value of CNT concentration and film thickness for the thin film structure of CNT-ZnS:(Cu, Al) by the screen printing method. We confirmed that an optimum value of CNT concentration in the ZnS:(Cu, Al) film panel is about 0.75 wt% resulting that the electric conductivity is 1.6 times higher than that of pure CNT sample and showing that the luminescence intensity is increasing until the optimum concentration. Clearly, CNT is presenting in the luminescence process providing a pathway for the creation of hot electron and a channel for the electron-hole recombination but overly inserted CNT may hinder to produce the hot electron for making an avalanching process. In case of the overly doped CNT 1.0 wt% in the ZnS-based phosphor, the luminescence intensity is decreasing although the electric conductivity is exponentially increasing. Based on these results, we realized that hot electron occurred by the external electric field or exciton arose by the external photon source are reduced dramatically over the critical value of CNT concentration because CNT element provide various isolated residues in the composites of ZnS based phosphor rather than pathway or channel for the D-A(Donnor to Acceptor) pair transition or the radiative recombination of electron-hole.

• 마이크로전자및패키징학회지
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• 제29권2호
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• pp.99-105
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• 2022

칩사이즈가 작아짐에 따라 선폭 또한 미세화되면서 인터커넥션의 밀집정도가 증가하고 있다. 그로 인해 캐패시터 층과 전기전도층의 저항 차이로 인해 RC delay가 문제되고 있다. 이를 해결하기 위해서는 높은 전기전도도의 전극과 낮은 유전율의 유전체 개발이 요구된다. 본 연구에서는 PCB (Print Circuit Board)의 회로를 외부요인으로부터 보호하는 상용 PSR (photo solder resist)과 우수한 내열 및 저유전 특성을 보유한 PI (polyimide)를 혼합하여 저유전체 잉크 개발을 진행하였다. 그 결과 PSR과 PI를 10:3으로 혼합한 잉크가 가장 우수한 결과를 보였으며 20 GHz와 28 GHz에서 각각 유전 상수 약 2.6, 2.37을 보였고, 유전손실은 약 0.022, 0.016으로 측정되었다. 차후 어플리케이션 적용 가능성 검증을 위해 테프론에 제작된 다양한 선폭의 전송선로에 평가하였으며 그 결과, PSR만 사용했을 때보다 PI와 혼합한 저유전체 잉크를 사용한 전송선로의 손실이 S21에서 평균 0.12 dB 덜 감소한 결과를 보였다.

• 멤브레인
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• 제33권2호
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• pp.77-86
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• 2023

본 연구에서는 낮은 막 저항과 높은 수산화 이온 전도성을 가지는 세공 충진 이온교환막 제조법으로 연구하였다. 알칼리 내구성을 향상하기 위해 폴리 테트라 플로오 에틸렌 소재인 다공성 지지체를 사용하였고 세공에는 단량체 2-(dimethylamino)ethyl methacrylate (DMAEMA), vinylbenzyl chloride (VBC)를 이용하여 copolymer를 제조했다. 가교제는 divinylbenzene (DVB)를 사용하였고 가교제 함량별로 이온교환막을 제조하여 DMAEMA-DVB와 VBC-DMAEMA-DVB copolymer에서 가교제 함량이 미치는 영향에 관해 연구하였다. 그 결과, PTFE 소재 지지체를 이용하여 화학적 안정성이 향상했고 저압 UV 램프를 사용하여 낮은 온도에서 빠른 광중합이 가능하여 생산성을 높일 수 있는 장점이 있다. 음이온교환 막 연료전지에 요구되는 이온교환막의 물리적 및 화학적 안정성을 확인하기 위해서 인장강도와 내알칼리성 테스트를 진행하였다. 그 결과, 가교도가 증가할수록 인장강도 대략 40 MPa가 증가하였고, 최종적으로 이온전도도와 내알칼리성 테스트를 통해 가교제 함량이 증가할수록 알칼리 안정성이 증가하는 것을 확인하였다.

• 공업화학
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• 제21권1호
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• pp.58-62
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• 2010

$TiOSO_4$와 다층벽탄소나노튜브(MWCNT)를 사용하여 가수분해법으로 CNT-$TiO_{2}$ 나노복합체를 제조하였다. 제조된 $TiO_{2}$-CNT 복합체의 CNT는 아나타제 $TiO_{2}$에 균일하게 분산되어 있으며 MWCNT의 첨가량이 증가함에 따라 결정성 탄소의 비율과 O/Ti 비율이 증가함을 확인할 수 있다. CNT-$TiO_{2}$복합체의 광활성 및 오염물 흡착능력을 UV 조사 시간에 따른 메틸렌블루의 분해정도로 확인하였다. MWCNT의 비율이 높아질수록 높은 흡착능과 광분해능을 나타내었다. 이는 MWCNT의 높은 비표면적, 산소포함 관능기, 낮은 밴드갭 에너지, 높은 전기전도성, 높은 부피 대 표면적 비율, 균일한 구조 및 특성으로 인하여 CNT-$TiO_{2}$ 복합체의 광활성에 도움을 주는 것으로 보인다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.90.1-90.1
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• 2010

Due to the rapidly diminishing energy sources and higher energy production cost, the interest in dye-sensitized solar cells (DSSCs) has been increasing dramatically in recent years. A typical DSSC is constructed of wide band gap semiconductor electrode such as $TiO_2$ or ZnO that are anchored by light-harvesting sensitizer dyes and surrounded by a liquid electrolyte with a iodide ion/triiodide ion redox couple. DSSCs based on one-dimensional nano-structures, such as ZnO nanorods, have been recently attracting increasing attention due to their excellent electrical conductivity, high optical transmittance, diverse and abundant configurations, direct band gap, absence of toxicity, large exiton binding energy, etc. However, solar-to-electrical conversion performances of DSSCs composed of ZnO n-type photo electrode compared with that of $TiO_2$ are not satisfactory. An important reason for the low photovoltaic performance is the dissolution of $Zn^{2+}$ by the adsorption of acidic dye followed by the formation of agglomerates with dye molecules which could block the I-diffusion pathway into the dye molecule on the ZnO surface. In this paper, we prepared the DSSC with the ZnO electrode using the chemical bath deposition (CBD) method under low temperature condition (< $100^{\circ}C$). It was demonstrated that the ZnO seed layers played an important role on the formation of the ZnO nanostructures using CBD. To achieve truly low-temperature growth of the ZnO nanostructures on the substrates, a two-step method was developed and optimized in the present work. Firstly, ZnO seed layer was prepared on the FTO substrate through the spin-coating method. Secondly, the deposited ZnO seed substrate was immersed into an aqueous solution of 0.25M zinc nitrate hexahydrate and 0.25M hexamethylenetetramine at $90^{\circ}C$ for hydrothermal reaction several times.

• 전기학회논문지
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• 제63권2호
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• pp.250-256
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• 2014

In this study, we deposited and investigated ${\mu}c$-Si:H thin films prepared by Plasma Enhanced Chemical Vapor Deposition(PECVD) system. To deposition silicon thin films, we controlled $SiH_4$ gas concentration, RF input power, and heater temperature. According to the experiments, the more $SiH_4$ gas concentration increased, deposition rate also increased but crystalline property decreased at the same conditions. In the RF input power case, deposition rate and crystalline property increased together when the input power increased from 100[W] to 300[W]. If RF input power was 300[W], deposition rate has reached saturation point. In the heater temperature, deposition rate increased when heater temperature increased. Crystalline property maintained a certain level until heater temperature was $250[^{\circ}C]$. And then it was a suddenly increased. Multistep method has been proposed to improve the quality of ${\mu}c$-Si:H thin film. $SiH_4$ gas was injected with a time interval. According to the experiments, crystallite ratio improve about 20~60[%] and photo conductivity increased up to six times.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 C
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• pp.1555-1558
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• 2002

This paper presents deposition and characterizations of microcrystalline silicon(${\mu}c$-Si:H) films prepared by hot wire chemical vapor deposition at substrate temperature below $300^{\circ}C$. The $SiH_4$ Concentration$[F(SiH_4)/F(SiH_4)+F(H_2)]$ is critical parameter for the formation of Si films with microcrystalline phase. At 6% of silane concentration, deposited intrinsic ${\mu}c$-Si:H films shows sufficiently low dark conductivity and high photo sensitivity for solar cell applications. P-type ${\mu}c$-S:H films deposited by Hot-Wire CVD also shows good electrical properties by varying the rate of $B_2H_6$ to $SiH_4$ gas. The solar cells with structure of Al/nip ${\mu}c$-Si:H/TCO/glass was fabricated with sing1e chamber Hot-Wire CVD. About 3% solar efficiency was obtained and applicability of HWCVD for thin film solar cells was proven in this research.