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차안나 샘터사 2011 월간 샘터 Vol.494 No.-

Ni-Pd-CNT Nanoalloys에서 성장한 α-Ga2O3의 특성분석

차안나,이기업,김형구,성채원,배효정,노호균,Vishal Vilas Burungale,하준석 한국마이크로전자및패키징학회 2021 마이크로전자 및 패키징학회지 Vol.28 No.4

This paper demonstrates the utility of the Ni-Pd and carbon-nanotube (Ni-Pd-CNT)-based nanoalloy to improve the α-Ga2O3 crystal quality using the halide-vapor-phase epitaxy (HVPE) method. As result, the overall thickness of the α-Ga2O3 epitaxial layer increased from a Ni electroless plating time of 40 s to 11 μm after growth. In addition, the surface morphologies of the α-Ga2O3 epilayers remained flat and crack-free. The full-width half-maximum results of the X-ray diffraction analysis revealed that the (1014) diffraction patterns decreased with increasing nominal thickness. 본 연구에서는 HVPE 방법을 사용하여 Ni-Pd and Carbon-Nanotube nanoalloys (Ni-Pd-CNT) 위에 α-Ga2O3 을 성장시켜 Ni-Pd-CNT에 따른 효과를 확인하였다. 그 결과, 무전해 Ni 도금 시간 40초에서 성장한 α-Ga2O3 에피층의두께는 11 μm로 확인되었다. 또한, α-Ga2O3 에피층의 표면 형태는 균열 발생 없이 기판에 대한 우수한 접착력을 보여주었다. 결과적으로, 성장과정에서 발생한 수평 성장에 의해 α-Ga2O3 대의 비대칭면인 (1014) FWMH 값을 크게 감소할 수있었다.

Growth of α-Ga2O3 Epitaxial Films on Al2O3 by Halide Vapor Pressure Epitaxy

이대장,차안나,박준성,노호균,문영부,하준석 한국마이크로전자및패키징학회 2019 마이크로전자 및 패키징학회지 Vol.26 No.4

In this study, we investigated the growth of single-crystallinity α-Ga2O3 thin films on c-plane sapphire substrates using halide vapor pressure epitaxy. We also found the optimal growth conditions to suppress the phase transition of α-Ga2O3. Our results confirmed that the growth temperature and partial pressure of the reactive gas greatly influenced the crystallinity. The optimal growth temperature range was about 460~510oC, and the α-Ga2O3 thin films with the highest crystallinity were obtained at a III/VI ratio of 4. The thickness and surface morphology of the thin films was observed by scanning electron microscopy. The film thickness was 6.938 μm, and the full width at half maximum of the ω-2θ scan rocking curve was as small as 178 arcsec. The optical band gap energy obtained was 5.21 eV, and the films were almost completely transparent in the near-ultraviolet and visible regions. The etch pit density was found to be as low as about 6.0 × 104 cm−2.

초등학교 교실공간의 체적분석에 의한 공간감의 인식에 관한 연구

김수인,차안나,김종필,장동국 대한건축학회지회연합회 2007 대한건축학회연합논문집 Vol.9 No.3

Since the 7th reform of education policy has been implemented into many schools, new planning and design methods have been also introduced into elementary schools. One of most importantly as well as urgently introduced design factors in them is probably classroom's size to meet the requirements of fast changing trends not only in our social policy but also in the number of students and their body shape, such as height, weight, etc. It is however very difficult to find suitable design criteria which can be employed into the design of elementary school's classroom, for example, the volume and size of classroom for the new ages. This study investigates three elementary schools in Gwang-ju City to identify the differences in the volume and size of their classrooms with the introduction of space density model of classroom showing the ratio of classroom's volume and that of teaching aids. Five key factors are introduced to find students' attitudes in their recognition of classroom, such as a sense on the width, depth, height, inside wall, and the colour. Students in the three elementary schools were questioned by the five key factors and their questionnaires were analysed by student's sex. Research results show that the above mentioned ratio in the three elementary schools shows little difference, but their recognition on the classrooms reveals a little bit interesting results. In general, they regard their classroom as sort of wide and having a suitable depth with high ceiling height. Regarding their recognition on the wall and colour, they answer that the classroom's walls are some tidy and their colour is a little bit warm.

전해 도금을 이용한 높은 접착 특성을 갖는 섬유 기반 웨어러블 디바이스 제작

김형구,노호균,차안나,이민정,박준범,정탁,하준석,Kim, Hyung Gu,Rho, Ho Kyun,Cha, Anna,Lee, Min Jung,Park, Jun-beom,Jeong, Tak,Ha, Jun-Seok 한국마이크로전자및패키징학회 2021 마이크로전자 및 패키징학회지 Vol.28 No.1

In order to produce wearable displays with high adhesion while maintaining flexible characteristics, the adhesive method using electro plating method was carried out. Laser lift-off (LLO) transcription was also used to remove sapphire substrates from LEDs bonded to fibers. Afterwards, the SEM and EDS data of the sample, which conducted the adhesion method using electro plating, confirmed that copper actually grows through the lattice of the fiber fabric to secure the light source and fiber. The adhesion characteristics of copper were checked using Universal testing machine (UTM). After plating adhesion, the characteristics of the LLO transcription process completed and the LED without the transcription process were compared using probe station. The electroluminescence (EL) according to the enhanced current was measured to check the characteristics of the light source after the process. As the current increases, the temperature rises and the bandgap decreases, so it was confirmed that the spectrum shifted. In addition, the change in the electrical characteristics of the samples according to the radius change is confirmed using probe station. The radius strain also had mechanical strength that copper could withstand bending stress, so the Vf variation was measured below 6%. Based on these results, it is expected that it will be applied to batteries, catalysts, and solar cells that require flexibility as well as wearable displays, contributing to the development of wearable devices. 유연한 특성을 유지하면서 높은 접착력을 가진 웨어러블 디스플레이를 제작하기 위하여 전해도금법을 이용한 접착법을 진행하였다. 또한 섬유에 접착된 LED의 사파이어 기판을 제거하기 위하여 LLO 전사법을 이용하였다. 그 후 전해도금을 이용한 접착법을 진행한 샘플의 SEM, EDS 데이터를 통하여 실제로 구리가 섬유직물의 격자사이를 관통하여 성장하며 광원과 섬유를 고정시켜주는 것을 확인하였다. 구리의 접착특성을 확인하기 위하여 Universal testing machine (UTM)을 이용하여 측정하였다. 도금 접착 후 laser lift-off (LLO) 전사공정을 완료한 샘플과 전사공정을 진행하지 않은 LED의 특성을 probe station을 이용하여 비교하였다. 공정 이후의 광원의 특성을 확인하기 위하여 인가 전류에 따른 electroluminescence (EL)을 측정하였다. 전류가 증가할수록 온도가 상승하여 Bandgap이 감소하기 때문에 spectrum이 천이하는 것을 확인하였다. 또한 radius 변화에 따른 샘플의 전기적 특성 변화를 probe station을 이용하여 확인하였다. Radius 변형에도 구리가 bending stress를 견딜 수 있는 기계적 강도를 가지고 있어 Vf 변화는 6% 이하로 측정되었다. 이러한 결과를 토대로 웨어러블 디스플레이 뿐만 아니라 유연성이 필요한 배터리, 촉매, 태양전지 등에 적용되어 웨어러블 디바이스의 발전에 기여할 수 있을 것으로 기대한다.

차세대 웨어러블 디바이스를 위한 높은 기계적/전기적 특성을 갖는 CNT-Ni-Fabric 유연기판

김형구,노호균,차안나,이민정,하준석 한국마이크로전자및패키징학회 2020 마이크로전자 및 패키징학회지 Vol.27 No.2

Recently, numerous researches are being conducted in flexible substrate to apply to wearable devices. Particularly, Conductive substrate researches that can implement the wearable devices on clothing are massive. In this study, we formed fiber substrate spraying CNT and Pd mixed solution on it and plated metal layer with electroless plating. Used SEM equipment and EDS analysis to analysis structure of the plated fiber substrate and discovered Ni layer was created. For check electrical properties, mapping was performed to check surface resistance and distribution of resistance of electroless plated fiber substrate with 4-point probe. It was confirmed that conductivity was improved as the duration of electroless plating was increased, and it was found that distribution of resistance by surface location was uniform. Changes in resistance due to mechanical stress were measured through tensile, bending, and twisting tests. As a result, it was confirmed that resistance change of flexible substrate gradually disappeared as plating time increased. Using UTM (Universal testing machine), it was analyzed mechanical properties of the electroless plated substrate with respect to changes in plating time were improved. In the case of conductive fiber substrate in which electroless plating was performed for 2 hours, tensile strength was increased by 16 MPa than fiber substrate. Based on these results, we found that Ni- CNT-Fabric flexible substrate is adequate for clothing-intergrated conductive substrate and we positively expect that this experiment shows flexible substrate can adapt to and develop not only a wearable device technology but also other fields needing flexibility such as battery, catalyst and solar cell. 최근 웨어러블 장치에 적용하기 위한 유연성 기판에 대한 연구가 활발히 진행되고 있다. 특히, 유연성 기판중의복에 웨어러블 장치를 적용하기 위한 전도성 섬유기판에 대한 연구가 진행되고 있다. 본연구에서는, 면섬유 기판 표면에 CNT와 Pd복합 용액을 스프레이 법을 이용하여 형성하였고, 무전해 도금법을 이용하여 금속층을 도금하였다. 도금된섬유기판의 형상을 분석하기 위하여 SEM 장비를 이용하였고, CNT를증착한 섬유기판의 표면에 Ni 레이어가 형성된것을 확인하였다. EDS 분석을 통하여 섬유기판의 표면에 형성된 물질이 Ni임을 알 수 있었다. 전기적 특성을 확인하기 위하여 4-point probe로 무전해 도금을 진행한 섬유기판의 표면저항 및 저항 분포를 확인하기 위한 맵핑을 진행하였다. 무전해도금의진행시간이길어질수록전도성이 향상되었음을 확인할수있었고, 표면위치별저항의분포가 균일함을알수있었다. 인장력, 굽힘, 뒤틀림 시험을 통하여 기계적 스트레스로 인한 저항변화를 측정하였다. 그결과 도금 시간이길어질수록 유연성 기판의 저항변화가 점점 사라지는 것을 확인하였다. UTM(Universal testing machine)을이용하여 도금시간 변화에 대한 무전해 도금 기판의 기계적 특성 향상 여부에 대하여 분석하였다. 인장강도는 무전해 도금을 2 시간동안진행한 전도성 섬유기판의 경우, 면섬유 기판보다약 16 MPa 증가하였다. 이러한 결과들을 토대로 Ni-CNT-Fabric 유연기판은 의류 일체형 전도성 기판으로 이용되기에 충분함을 확인하였고, 이러한 연구 결과는 유연기판, 웨어러블 디바이스뿐만 아니라 유연성이 필요한 배터리, 촉매, 태양전지 등에 적용되어 발전에 기여할 수 있을 것으로 기대한다.

지역노인복지시설의 입지분포와 인구추이에 관한 고찰

김민석(Kim.Min-Seok),차안나(Cha.Ahn-Na),전진숙(Jeon.Jin-Sook),김수인(Kim) 대한건축학회 2004 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.24 No.1

The purpose of this study is preparing provision as investigating the actual condition, demand and present condition of welfare facility on the focus in Gwang-ju. Also, the ultimate purpose is finding an index making 'a system of network' of a district about the elderly population and welfare facility for the elderly.<br/> <br/> <br/> <br/>

YAG:Ce<SUP>3+</SUP>@ beta-SiALON 형광체를 이용한 InGaN 광전극의 효과적인 물분해

배효정(Hyojung Bae),이대장(Daejang Lee),차안나(An-Na Cha),주진우(Jin-Woo Ju),문영부(Youngboo Moon),하준석(Jun-Seok Ha) 한국태양광발전학회 2020 Current Photovoltaic Research Vol.8 No.2

GaN based photoelectrode has shown good potential owing to its better chemical stability and tunable bandgap with materials such as InN and AlN. Tunable bandgap allows GaN to make the maximum utilization of solar spectrum, which could improve photoelectrode performance. However, the problems about low photoelectrode performance and photo-corrosion still remain. In this study, we attempt to investigate the photoelectrochemical (PEC) properties of phosphor application to InGaN photoelectrode. Experimental result shows YAG:Ce<SUP>3+</SUP> and beta-SiALON phosphor result in the highest photoelectrode performance of InGaN.

그래핀-니켈 코어쉘을 적용한 광전기화학적 수소생산량 개선에 대한 연구

하준석(Jun Seok Ha),노호균,성채원,류혜수,배효정,차안나 한국고분자학회 2022 한국고분자학회 학술대회 연구논문 초록집 Vol.47 No.2