Papers by Author: Ki Hyun Kim

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Authors: Ki Hyun Kim, Dae Gab Gweon, Hyun Soo Jung, Soo Hun Lee, Min Sung Hong, Moon G. Lee
Abstract: Design of design of X-Y-Theta fine stage using VCM (voice coil motor) is presented in this paper. This fine stage is combined with linear DC motor. Long range, high speed and high precision of the stage is obtained by using dual servo control for laser micro/nano machining. A novel structure of VCM for the fine stage is proposed. The fine stage can have 3 DOF(X-Y-Theta) motion by four VCM actuators which are located on the same plane. The X-Y-Theta fine stage is designed to have high acceleration for high throughput. Based on the design, the stage is fabricated. The designed stage has the acceleration of 5m/s2 with 45kg total mass. In addition, this actuator is feedback controlled using HP laser interferometer. The reaction force between the coarse and fine stage of the dual servo is compensated by force compensator.
Authors: Ki Hyun Kim, Se Jin Ahn, Byung Tae Ahn, Kyung Hoon Yoon
Abstract: To make a dense CIGS absorber layer, spray deposited CIGS films were annealed in the two-zone RTP furnace in Se atmosphere. More Se supply by increasing Se evaporation temperature or by increasing the flow rate of carrier gas resulted in the larger CIGS grains. However, a thick MoSe2 layer was formed between CIGS and Mo, as the Se supply increased, results in partial detachment of CIGS/MoSe2/Mo layers from the glass substrate. From the result, it was found that the short heat- treatment with high Se vapor pressure is better than the long heat-treatment with low Se vapor pressure. The large CIGS grains without peeling off, can be obtained from the following conditions; Se evaporation temperature of 450oC, substrate temperature of 550oC, annealing time of 5 min, and flow rate of carrier gas of 30 sccm.
Authors: Hyung Seop Shin, Ki Hyun Kim, Young Jin Jung, Dong Kyun Ko
Abstract: The impact fracture behavior of Zr-based bulk metallic glass was investigated by an instrumented impact tester using subsize Charpy specimens. Influences of loading rate and notch shape on the fracture behavior of amorphous Zr-Al-Ni-Cu alloy were examined. As a result, the maximum load and absorbed fracture energy under impact loading were lower than those under quasi-static loading. A large part of the absorbed fracture energy in the Zr-based BMG was consumed in the process for crack initiation and not for crack propagation. In addition, fractographic characteristics of BMGs were investigated. Fractured surfaces under impact loading are smoother than those under quasi-static loading. The absorbed fracture energy appeared differently depending on the appearance of the shear bands developed. It can be found that the fracture energy and fracture toughness of Zr-based BMG are closely related with the extent of shear bands developed during fracture.
Authors: Ki Hyun Kim, Young Gab Chun, Byung Ok Park, Kyung Hoon Yoon
Abstract: Chalcopyrite CuInSe 2 (CIS) and CuInGaSe 2
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