• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.60-61
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• 2007

IAZO (indium aluminium zinc oxide) anode films were co-sputtered on glass substrate using a dual target DC magnetron sputtering system. For preparation of IATO films, at constant DC power of IZO (indium zinc oxide) target of 100 W, the DC power of AZO (Aluminum zinc oxide) target was varied from 0 to 100 W. To analyze electrical and optical properties of IAZO anode, Hall measurement examination and UV/V is spectrometer were performed, respectively. In addition, structure of IAZO anode film was examined by X-ray diffraction (XRD) method. Surface smoothness was investigated by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). From co-sputtered IAZO anode, good conductivity($2.32{\times}10^{-4}{\Omega}.cm$) and high transparency(approximately 80%) in the visible range were obtained even at low temperature deposition. Finally, J-V-L characteristics of phosphorescent OLED with IAZO anode were studied by Keithley 2400 and compared with phosphorescent OLED with conventional ITO anode.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.3
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• pp.194-197
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• 2013

We investigated the effect of etching time on the surface roughness, and electrical and optical properties of ZnO and 2 wt% Al-doped ZnO (AZO) films. The ZnO and AZO films were deposited on glass substrates by RF magnetron sputtering technique. The etching experiment was carried out using a solution of 5% HCl at room temperature. The surface roughness was characterized by Atomic Force Microscopy. The electrical property was measured by Hall measurement system and 4-point probe. The optical property was characterized by UV-vis spectroscopy. After the wet chemical etching, the surface textures were obtained on the surface of the ZnO and AZO films. With the increase of etching time, the surface roughness (RMS) of the films increased and the transmittance of the films was observed to decrease. For the AZO film, a low resistivity of $1.0{\times}10^{-3}\;{\Omega}{\cdot}cm$ was achieved even after the etching.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1347-1348
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• 2007

In this paper, ITO gate electrode surface was modified using $O_2$ plasma and organic gate insulating layers were deposited on the ITO surface using plasma polymerization technique. In order to investigate the influence of the plasma coupling method and plasma conditions on the plasma polymerized methyl methacrylate (ppMMA) thin film properties, inductively coupled (ICP) and capacitively coupled plasma (CCP) were used to generate the plasma and the plasma parameters were varied. The ppMMAs were investigated using atomic force microscopy (AFM) and a Fourier Transform Infrared (FT-IR) spectroscopy. Dielectric constants of the ppMMA thin films were investigated using a impedance analyzer (HP4192A, LF Impedance Analyzer). Current-Voltage (I-V) characteristics of the organic thin film transistors (OTFTs) were investigated using a source measurement unit (SMU: Keithley 2612). Proposed method can be applied to dry-process to fabricate OTFTs during overall fabricating steps.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.461-462
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• 2005

In order to improve the efficiency of dye-sensitized solar cell (DSC), $TiO_2$ electrode screen-printed on transparent conducting oxide (TCO) substrate was sintered in variation with different temperature(350 to $550^{\circ}C$). $TiO_2$ electrode on fluorine doped tin oxide (FTO) glass was assembled with Pt counter electrode on FTO glass. I-V properties of DSC were measured under solar simulator. Also, effect of sintering temperature on surface morphology of $TiO_2$ films was investigated to understand correlation between its surface morphology and sintering temperature. Such surface morphology was observed by atomic force microscopy (AFM). From the measurement results, at sintering temperature of $500^{\circ}C$, both efficiency and fill factor of DSC were mutually complementary, enhancing highest fill factor and efficiency. Consequently, it was considered that optimum sintering temperature of $\alpha$-terpinol included $TiO_2$ paste is at $500^{\circ}C$.

• Tribology and Lubricants
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• v.32 no.6
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• pp.207-211
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• 2016

To interpret the perception that originates from tactile sensibility during people touch and recognize the object surfaces, this study focuses on the development of a friction model that can describe the interaction of a stylus pen sliding over the counter surfaces. In addition, the study includes several other experimental factors such as the pressure, temperature, and topology of surface, which can have an effect on the emotional user experience concerning various surfaces; this research aims to suggest a method to quantitatively evaluate the relation between these experimental parameters and emotional user experience. Accordingly, the objective of research comprises the friction characteristic technology for measurement of fine tribological behavior and a standard to quantify the emotional feedback. Existing panels or input devices that provide interaction feedback about user actions simply operate with a single frequency vibration or sound response. On the contrary, this research investigates various interaction characteristics including friction force, frequency, and surface topology synthetically. Using the developed model, which can explain the relation between the friction parameters and emotional user experience, developers can design their product in order to provide the user with expected emotional sensibility. Consequently, it can contribute to reduce the development cost about sensitivity model.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.471-474
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• 2005

This study investigates the nano/microstructure, the aging response, and the mechanical/tribological properties of the eutectic regions in rheoformed A356 alloy-T5 parts using nano/micro-indentation and mechanical scratching, combined with optical microscopy and atomic force microscope (AFM). Most eutectic Si crystals in the A356 alloy showed a modified morphology as fine-fibers. The loading curve for the eutectic region was more irregular than that of the primary Al region due to the presence of various particles of varying strength. The aging responses of the eutectic regions in the rheoformed A356 alloys aged at $150^{\circ}C$ for different times (0, 2, 4, 8, 10, 16, 24, 36, and 72 h) were investigated. Both Victors hardness $(H_v)$ and indentation $(H_{IT})$ test results showed a similar trend of aging curves, and the peak was obtained at the same aging time of 10 h. A remarkable size-dependence of the tests was found.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.318.2-318.2
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• 2013

기존의 염료감응형 태양전지(Dye Sensitized Solar Cells; DSSCs)는 최대 효율 11~12%의 광전변환효율을 가지고 있다. 이러한 한계를 극복하기 위해서 광흡수 층 최적화, 상대전극의 촉매성 증대, 전해질의 산화 환원 반응 최적화 등의 많은 연구가 이루어지고 있다. 본 연구에서는 DSSCs의 광전변환효율을 증가시키고자 기존의 투명전극 및 기판으로 사용되는 FTO(Fluor-doped Tin Oxide)를 GZO(Gallium-doped Zinc Oxide)를 사용하여 투명전극기판에 따른 계면 저항, 전류손실 등 DSSCs에 미치는 영향을 분석하였다. 본 연구에 사용된 FTO는 ${\sim}7{\Omega}/{\square}$의 면저항과 80%이상의 투과도를 갖고 있으나 Ion-Sputtering 법으로 증착된 GZO는 열처리 과정을 통하여 $3{\sim}4{\Omega}/{\square}$의 면 저항을 나타내고 80%이상의 우수한 투과도를 가지고 있다. 이러한 두 기판의 특성 비교를 위해, UV-Visble Spectrophotometer를 사용하여 광학적 특성을 분석하고, SEM(Scanning Electron Microscope), AFM(Atomic Force Microscope)를 사용하여 표면 특성을 평가하였다. 또한 전기적 특성을 분석하기 위하여 4-Point-probe를 이용하여 면 저항을 측정하였고, DSSCs의 효율 및 Fill Factor를 분석하기 위하여 Solar Simulator의 I-V measurement를 이용하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.223.2-223.2
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• 2013

비정질 실리콘은 태양전지, 트랜지스터, 이미지 센서 등 다양한 분야에서 응용되고 있으며 새로운 박막 소자 개발을 위한 소재로서 많은 연구가 진행되고 있다. 하지만 소자개발에 있어 공정상에서 발생하는 비정질 실리콘 박막의 높은 응력(stress)은 소자의 특성을 떨어뜨리는 문제점을 갖는다. 따라서 우수한 특성의 소자 개발을 위해서는 보다 낮은 응력을 갖는 비정질 실리콘 박막 증착 및 공정 조건에 따른 응력 조절이 필요하다. 저응력의 비정질 실리콘 박막 증착은 보다 낮은 반응온도에서 증착속도를 최소로 하여 성장되어야 하는데 이는 플라즈마기상증착(Plasma enhanced chemical vapor deposition, PECVD) 시스템에 의해 가능하다. 따라서 본 연구에서는 PECVD 시스템을 사용하여 비정질 실리콘 박막을 증착하였고 그 특성을 분석하였다. 이 때 증착 온도, rf 파워, 공정 압력은 실험결과로부터 얻어진 낮은 박막 증착속도 하에서 안정적으로 증착이 가능한 조건으로 일정하게 유지하여 실험하였다. 공정 가스는 SiH4/He/N2의 혼합가스를 사용하였고 응력 조절을 위해 SiH4/He 가스비를 일정한 비율로 변화하여 비정질 실리콘 박막을 증착하였다. 증착된 박막의 두께 및 표면 특성은 field emission scanning electron microscopy 및 atomic force microscopy를 이용하여 분석하였고, energy dispersive X-ray 분석을 통하여 정량 및 정성적 분석을 수행하였다. 그리고 stress measurement system을 이용하여 박막의 응력을 측정하였고 X-ray diffraction 측정 및 ellipsometry 측정으로부터 증착된 박막의 결정성, 굴절률 및 oiptical bandgap을 분석하였다.

• Transactions of Materials Processing
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• v.29 no.6
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• pp.323-330
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• 2020

The surface region of a sheet metal may have different characteristics from the inner region because the surface region is less restricted than the interior. In addition, the grains on the free surface are less hardened because of surface adsorption of the dislocations, rather than piling up. In the case of bulk or thick sheet metals, this effect is negligible because the fraction of the surface region is much smaller than that of the inner region. However, this surface effect is important in the case of ultra-thin sheet metals. In order to evaluate the surface effect, tensile and bending tests were performed for the SS304 stainless steel with a thickness of 0.39 mm. The bending force predicted using the tensile behavior is higher than the measurement because of the surface effect. To account for the surface effect, the surface layer model was developed by dividing the sheet section into surface and inner layers. The mechanical behaviors of the two regions were calibrated using the tensile and bending properties. The surface layer model reproduced the bending behavior of the ultra-thin sheet metal.

• Journal of Institute of Convergence Technology
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• v.7 no.2
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• pp.25-30
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• 2017

This paper presents the effects of a virtual mass with a low-pass filter on the stability boundary of a virtual spring in the haptic system. In general, a haptic system consists of a haptic device, a sampler, a virtual impedance model and zero-order-hold. The virtual impedance is modeled as a virtual spring and a virtual mass. However the high-frequency noise due to the sampling time and the quantization error of sampled data may be generated when an acceleration is measured to compute the inertia force of the virtual mass. So a low-pass filter is needed to prevent the unstable behavior due to the high-frequency noise. A finite impulse response (FIR) filter is added to the measurement process of the acceleration and the effects on the haptic stability are simulated. According to the virtual mass with the FIR filter and the sampling time, the stability boundary of the virtual spring is analyzed through the simulation. The maximum available stiffness to guarantee the stable behavior is reduced, but simulation results still show that the stability boundary of the haptic system with the virtual mass is larger than that of the haptic system without the virtual mass.