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초소형기계시스템의 공진특성 분석을 통한 박막의 기계적 특성 평가
정증현(Jeung-hyun Jeong),이세호(Se-Ho Lee),정성훈(Sung-hoon Jung),권동일(Dongil Kwon) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.3
Electrostatically resonating testing devices were used to evaluate elastic modulus, fracture toughness, fatigue properties of microscale materials applicable to thin film system, MEMS, electronic package. Here, Rayleigh's energy method was used to obtain the relationship between resonance frequency and system stiffness, where resonance frequence can be converted into elastic modulus and notch length. For laterally actuated devices, resonance frequencies were measured as a function of temperature during temperature cycle, which was used to estimate elastic modulus with varying temperature. Other devices with micro-notch in their beams were used to understand the effect of notch shape on fracture toughness and life time. Experimental results show that it was successful to evaluate the temperature dependency of elastic modulus, notch-shape dependecy of fraucture toughness, and fatigue properties.
전착법을 이용한 CuInSe<sub>2</sub> 박막태양전지 광활성층의 조성 조절
박영일,김동환,서경원,정증현,김홍곤,Park, Young-Il,Kim, Donghwan,Seo, Kyungwon,Jeong, Jeung-Hyun,Kim, Honggon 한국전기전자재료학회 2013 전기전자재료학회논문지 Vol.26 No.3
Thin light-active layers of the $CuInSe_2$ solar cell were prepared on Mo-coated sodalime glass substrates by one-step electrodeposition and post-annealing. The structure, morphology, and composition of $CuInSe_2$ film could be controlled by deposition parameters, such as the composition of metallic precursors, the concentration of complexing agents, and the temperature of post-annealing with elemental selenium. A dense and uniform Cu-poor $CuInSe_2$ film was successfully obtained in a range of parametric variation of electrodeposition with a constant voltage of -0.5 V vs. a Ag/AgCl reference electrode. The post-annealing of the film at high temperature above $500^{\circ}C$ induced crystallization of $CuInSe_2$ with well-developed grains. The KCN-treatment of the annealed $CuInSe_2$ films further induced Cu-poor $CuInSe_2$ films without secondary phases, such as $Cu_2Se$. The structure, morphology, and composition of $CuInSe_2$ films were compared with respect to the conditions of electrodeposition and post-annealing using SEM, XRD, Raman, AES and EDS analysis. And the conditions for preparing device-quality $CuInSe_2$ films by electrodeposition were proposed.
레이저 간섭계 ( ESPI ) 를 이용한 폴립칩 패키지의 열변형 평가
장우순(Woo Soon Jang),이백우(Baik Woo Lee),김동원(Dong Won Kim),정증현(Jeung Hyun Jeong),백경욱(Kyung Wook Paik),권동일(Dong Il Kwon),나전웅(Jae Woong Nah) 대한금속재료학회 ( 구 대한금속학회 ) 2002 대한금속·재료학회지 Vol.40 No.9
In this study, electronic speckle pattern interferometry (ESPI) was applied to a non-destructive and real-time evaluation of the thermal deformation in a flip-chip package. The displacement resolution of ESPI was improved with magnifying lenses, and ESPI was modified to measure the deformation of micro systems. The flip-chip package thermally deforms with increasing temperature, and the difference in the thermal expansion between the chip and the PCB induces the micro-failure at the solder joint. To evaluate the level of thermal deformation precisely, the horizontal and vertical deformations were measured in the temperature range of 25℃ to 125℃ in situ using the resolution-enhanced ESPI to a sub-micrometer scale. From the experimental results, it was found that the CTE (coefficient of thermal expansion) difference between the chip and the PCB leads to shear strain at the solder joint. In addition, the shear strain could be evaluated at each solder joint. To verify these experimental results, the finite element analysis(FEA) results were compared with the ESPI results. The FEA results were similar to the ESPI results, which confirmed the adequacy of our application.
KF 후열처리 공정시 CIGS 박막의 Na 원소 존재가태양전지 셀성능에 미치는 영향
손유승(Yu-Seung Son),김원목(Won Mok Kim),박종극(Jong-Keuk Park),정증현(Jeung-hyun Jeong) 한국태양광발전학회 2015 Current Photovoltaic Research Vol.3 No.4
The high efficiency cell research processes through the KF post deposition treatment (PDT) of the Cu(In,Ga)Se₂(CIGS) thin film has been very actively progress. In this study, it CIGS thin film deposition process when KF PDT 300 to the processing temperature, 350, 400°C changed to soda-lime glass (SLG) efficiency of the CIGS thin film characteristics, and solar cell according to Na presence of diffusion from the substrate the effects were analyzed. As a result, the lower the temperature of KF PDT and serves to interrupt the flow of current K-CIGS layer is not removed from the reaction surface, FF and photocurrent is decreased significantly. Blocking of the Na diffusion from the glass substrate is significantly increased while the optical voltage, photocurrent and FF is a low temperature (300, 350°C) in the greatly reduced, and in 400°C tend to reduce fine. It is the presence of Na in CIGS thin film by electron-induced degradation of the microstructure of CIGS thin film is expected to have a significant impact on increasing the hole recombination rate a reaction layer is formed of the K elements in the CIGS thin film surface.
입방정 질화붕소 박막의 잔류응력 형성에 미치는 산소 첨가 효과
장희연(Hee-yeon Jang),박종극(Jong-Keuk Park),이욱성(Wook-Seong Lee),백영준(Young-Joon Baik),임대순(Dae-Soon Lim),정증현(Jeung-hyun Jeong) 한국표면공학회 2007 한국표면공학회지 Vol.40 No.2
In this study, we investigated the oxygen effect on the nucleation and its residual stress during unbalanced magnetron sputtering. Up to 0.5% in oxygen flow rate, cubic phase (c-BN) was dominated with extremely small fraction of hexagonal phase (h-BN) of increasing trend with oxygen concentration, whereas hexagonal phase is dominated beyond 0.75% flow rate. Interestingly, the residual stress in cubic-phase-dominated films was substantially reduced with small amount of oxygen (~0.5%) down to a low value comparable to the h-BN case. This may be because oxygen atoms break B-N sp³ bonds and make B-O bonds more favorably, increasing sp² bonds preference, as revealed by FTIR and NEXAFS. It was confirmed by experimental facts that the threshold bias voltage for nucleation and growth of cubic phase were increased from ?55 V to ?70 V and from ?50 V to ?60 V, respectively. The reduction of residual stress in O-added c-BN films is seemingly resulting from the microstructure of the films. The oxygen tends to increase slightly the amount of h-BN phase in the grain boundary of c-BN and the soft h-BN phase of 3D network including surrounding nano grains of cubic phase may relax the residual stress of cubic phase.