• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.2
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• pp.249-254
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• 2015

Solution-derived amorphous indium-gallium-zinc oxide (a-IGZO) thin-film-transistor (TFTs) were developed using a microwave irradiation treatment at low process temperature below $300^{\circ}C$. Compared to conventional furnace-annealing, the a-IGZO TFTs annealed by microwave irradiation exhibited better electrical characteristics in terms of field effect mobility, SS, and on/off current ratio, although the annealing temperature of microwave irradiation is much lower than that of furnace annealing. The microwave irradiated TFTs showed a smaller $V_{th}$ shift under the positive gate bias stress (PGBS) and negative gate bias stress (NGBS) tests owing to a lower ratio of oxygen vacancies, surface absorbed oxygen molecules, and reduced interface trapping in a-IGZO. Therefore, microwave irradiation is very promising to low-temperature process.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1431-1433
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• 1996

Effective ionization coefficients for (100), (110) and (111) oriented gallium arsenide are extracted from the ionization coefficients far electrons and holes. Analytical formulas for the breakdown voltage of the GaAs Schottky rectifiers are derived by employing the ionization coefficients. The breakdown voltages obtained from our analytical model agree fairly well with the numerical results as well as the experimental ones reported in the range of $10^{14}\;cm^{-3}$ - $5{\times}10^{17}\;cm^{-3}$ doping concentrations.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1235-1236
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• 2015

This paper reports hyperelastically stretchable strain gauges based on liquid metal (eutectic gallium-indium;EGaIn) and a platinum-catalyzed silicone elastomer ($Ecoflex^{TM}$). A custom liquidmetal patterning setup was operated to fabricate liquidmetal straingauge on flexible substrate. The printed strain gauges were tested under cyclic uniaxial stretching, twisting, even bending of human finger. By engineering the orientation of solid wires placed over two terminals of t he printed liquid metal resistor, we stably achieved the stretchability of ~800 % which is the highest value reported so far, to the best of our knowledge.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.154.1-154.1
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• 2014

Indium gallium zinc oxide (IGZO)는 차세대 디스플레이 평판 패널에 사용되는 반도체 화합물의 일종으로 최근 주목받고 있는 물질의 하나이다. 기존의 IGZO를 사용하여 박막을 증착한 뒤 표면 처리를 통해 박막의 특성 변화에 대한 연구들이 진행되어 왔으며, 기존의 연구들은 plasma 환경에 노출을 시켜 간접적인 plasma treatment를 통해 박막의 특성을 향상시켜 왔다. 본 연구에서는 기존의 plasma treatment에서 발견된 방식인 ion beam treatment를 통해 플라즈마를 직접적으로 표면에 조사하여 박막의 특성 변화를 알아보았다. 한국표준과학연구원에서 자체 제작한 chamber를 이용하여 RF sputter로 Si wafer 위에 IGZO 박막을 증착하고 수소 ion beam treatment를 한 뒤, SEM과 XPS를 사용하여 박막 표면의 물성 변화를 분석하였다. 실험에 사용된 chamber에는 sputter gun과 ion beam이 함께 장착되어 있으며, scroll pump와 TMP를 사용하여 pressure를 유지하였다. 실험 시 base pressure는 $1.4{\times}10^{-6}Torr$였다. RF power 150 W. ion beam power 2,000 V에서 실험을 진행하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.3
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• pp.257-262
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• 2001

Single crystalline films of La doped YIG(yttrium iron garnet) were grown by the liquid phase epitaxy. The lattice constants of films obtained by DCD(double crystalline diffractometer) measurement increased with increasing La contents in films. In particular, lattice constants of films grown wiht Y/La=20 solution were nearly same as those of GGG (gadolinium gallium garnet) substrate. The saturation magnetization measured with VSM (vibrating sample magnetometer) was about 1750Gauss which is the same as that of pure YIG irrespective of La contents in films. FMR(ferromagnetic resonance) linewidth of La doped YIG was smaller than that of pure YIG. Since appropriate La doping decreases the lattice mismatch between film and substrate, the FMR linewidth was Y/La=20 in this experiment.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.4
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• pp.226-231
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• 1999

Temperature dependence of effective ionization coefficients in GaAs is formulated as a single polynomial function of temperature, which allows analytical expressions for breakdown voltage of GaAs $p^+n$ junctions as a function of temperature. At 300 K, extracted effective ionization coefficient of GaAs $p^+n$ junction especially agrees well with the published result of <111> oriented GaAs. The analytic results agree with the simulation as well as the experimental ones reported within 10% in error for the doping concentrations in the range of $10_{14}cm_{-3}~10_{17}cm_{-3}$ at 100 K, 300 K and 500 K.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.367-367
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• 2011

CIGS solar cell with copper, indium, gallium and selenium is a second generation solar cells for the lowering of the manufacturing cost. The relative ratio of the four elements is one of the most important measurement issues because the photovoltaic property of CIGS solar cell depends on the crystalline structure of the CIGS layer. However, there is no useful analysis method for the composition of the CIGS layer. Recently, AES depth profiling analysis of CIGS films has been studied with a reference material certified by inductively coupled plasma optical emission spectroscopy. However, there are some problems in AES depth profiling analysis of CIGS films. In this study, the in-depth profiling analysis was investigated by secondary ion mass spectrometry (SIMS) depth profiling analysis. We will present the compositional depth profiling of CIGS films by SIMS and its applications for the development of CIGS solar cells with high efficiency.

• Journal of the Korean Ceramic Society
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• v.55 no.4
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• pp.325-336
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• 2018

Perovskite solar cells (PSCs) are a new class of photovoltaic devices, which have attracted significant attention due to their remarkable optoelectrical properties, including high absorption coefficients, high carrier mobilities, long carrier diffusion lengths, tunable bandgaps, low cost, and facile fabrication. PSCs have reached efficiencies of 22.70% and 18.36% on rigid fluorine-doped tin oxide and poly(ethylene terephthalate) substrates, respectively; these are comparable to those of single-crystal silicon and copper-indium-gallium-selenium solar cells. Over the past eight years, the photo conversion efficiency of PSCs has been significantly improved by device-architecture adjustments, and absorber and electron/hole transport layer optimization. Each layer is important for the performance of PSCs; hence, we discuss achievements in flexible perovskite solar cells (FPSCs), covering electron/hole-transport materials, electrode materials. We give a comprehensive overview of FPSCs and put forward suggestions for their further development.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.465-465
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• 2013

Inorganic 물질인 SiO2 dielectric 위에 organic dielectric PVP (4-vinyphenol)를 spin coating으로 올려, inorganic/organic dielectric 형태의 double layer구조로 High-performance amorphous indiumgallium zinc oxide thin-film transistors (IGZO TFT)를 제작하여 보았다. SiO2 dielectric을 buffer layer로 80 nm, PVP는 10Wt% 400 nm로 구성하였으며, 200 nm single SiO2 dielectric과 동일한 수준의 leakage current 특성을 MIM Capacitor 구조를 통해서 확인할 수 있었다. 이 소자의 장점은 용액공정의 도입으로 공정 시간의 단축 및 원가 절감을 이룰 수 있으며, dielectric과 channel 사이의 균일한 interface의 형성으로 interface trap 개선 및 Yield 향상의 장점을 갖는다. 우리는 실험을 통해서 SiO2 buffer layer가 수직 electric field에 의한 leakage current을 제어하고, PVP dielectric은 interface를 개선하는 것을 확인하였다. Vth의 negative shift 및 slope의 향상으로 구동전압이 줄어들고, 균일한 I-V Curve 형성을 통해서 Process Yield의 향상을 확인하였다.

• Journal of the Korean institute of surface engineering
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• v.37 no.4
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• pp.191-195
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• 2004

Gallium or sulphur additions in $CuInSe_2$ were prepared using RF magnetron sputtering and pulsed laser deposition respectively. All of the observed thin films shows a chalcopyrite structure with the S and Ga addition increases the favourable (112) peak. The optical absorption coefficients were slightly decreased. The energy band gap of films could be shifted from 1.04 to 1.68 eV by adjusting the mole ratio of S/(S+Se) and Ga/(In+Ga). It is possible to obtain the optimum energy band gap by adding S or Ga solute at a certain ratio in favour of Se and In respectively. It is also necessary to control the ratio of Ga and S additions and to retain a certain portion of In and Se to provide better properties of thin films.