• 한국정보통신학회논문지
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• 제16권11호
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• pp.2511-2516
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• 2012

본 연구에서는 이중게이트 MOSFET의 전도중심에 따른 문턱전압의 변화를 분석할 것이다. DGMOSFET에 대한 단채널효과 중 문턱전압의 이동은 정확한 소자동작에 저해가 되고 있다. 문턱전압분석을 위하여 포아송방정식의 분석학적 전위분포를 이용하였으며 이때 전하분포함수에 대하여 가우시안 함수를 사용함으로써 보다 실험값에 가깝게 해석하였다. 소자 파라미터인 채널길이, 채널두께, 게이트산화막두께 그리고 도핑농도 등에 대하여 전도중심의 변화에 대한 문턱전압의 변화를 관찰하였다. 본 연구의 모델에 대한 타당성은 이미 기존에 발표된 논문에서 입증하였으며 본 연구에서는 이 모델을 이용하여 문턱전압특성을 분석할 것이다. 분석결과 문턱전압은 소자파라미터에 에 대한 전도중심의 변화에 크게 영향을 받는 것을 관찰할 수 있었다.

• Journal of Mechanical Science and Technology
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• 제17권7호
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• pp.1063-1072
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• 2003

Direct immersion cooling has been considered as one of the promising methods to cool high power density chips. A fluorocarbon liquid such as FC-72, which is chemically and electrically compatible with microelectronic components, is known to be a proper coolant for direct immersion cooling. However, boiling in this dielectric fluid is characterized by its small value of the critical heat flux. In this experimental study, we tried to enhance the critical heat flux by increasing the nucleate boiling area in the heat spreader (Conductive Immersion Cooling Module). Heat nux of 2 MW/㎡ was successfully removed at the heat source temperature below 78$^{\circ}C$ in FC-72. Some modified boiling curves at high heat flux were obtained from these modules. Also, the concept of conduction path length is very important in enhancing the critical heat flux by increasing the heat spreader surface area where nucleate boiling occurs.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2012년도 춘계학술대회
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• pp.709-712
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• 2012

본 연구에서는 분석학적 모델을 이용하여 DGMOSFET의 전류-전압을 고찰하고자 한다. 분석학적 모델을 유도하기 위하여 포아송 방정식을 이용하였다. 드레인 전류가 $10^{-7}A$일 때 상단게이트전압을 문턱전압으로 정의하였다. 채널의 길이를 20nm에서 100nm까지 변화시켜 채널길이에 따른 전류-전압특성을 분석하였다. 또한 본 연구에서 제시한 모델을 사용하여 DGMOSFET 설계시 중요한 도핑농도와 채널두께 등의 요소변화에 대한 전류-전압의 변화를 관찰하였다. 구조적 파라미터의 변화에 따라 전도중심의 변화와 전도중심이 전류-전압에 미치는 영향을 분석하였다.

• 대한기계학회논문집B
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• 제40권2호
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• pp.111-117
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• 2016

본 연구의 목적은 실리콘 열전달 조절을 위한 포논의 평균자유행로(Mean free path, MFP) 스펙트럼 열전달 기여도 예측이다. 열전달의 크기 효과는 포논의 MFP 와 재료의 특성길이가 비슷할 때 나타나는데, 나노시스템 응용을 위한 재료의 열전달 증감을 위해 포논 MFP 스펙트럼에 대한 열전달 기여도 예측이 중요하다. 이를 위해 포논의 주파수 의존성이 고려된 볼츠만 수송방정식(Boltzmann transport equation) 근간의 full phonon dispersion 모델을 통해 실리콘 박막(Silicon-on-Insulator) 트랜지스터의 실리콘 박막 두께 변화(41-177 nm)에 따른 포논 MFP 스펙트럼 열전달 특성 및 비등방성을 해석함으로써, 본 연구 결과는 향후 박막 트랜지스터에 대한 고효율 열소산(heat dissipation) 설계전략에 활용될 수 있다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.1092-1095
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• 2001

Steady state thermal analysis has been done by a finite element method in a diode of 12kV blocking voltage. The diode was fabricated by soldering ten pieces of 1200V diodes in series, capping a dummy wafer at the far end of diode series, and finally wire bonded for building anode and cathode terminal. In order to achieve high voltage and reliability, the edge of each diode was beveled and passivated by resin with a thickness of 25${\mu}$m. It was assumed that the generated heat which is mainly by the on-state voltage drop, 9V for 12kV diode, is dissipated by way of the conduction through diodes layers to bonding wire and of the convection at the surface of passivating resin. It was predicted by the thermal analysis that the temperature rise of a pn junction of the 12kV diode can reach at the range of 16∼34$^{\circ}C$ under the given boundary conditions. The thickness and thermal conductivity(0.3∼3W/m-K) of the passivating resin did little effect to lower thermal resistance of the diode. As the length of the bonding wire increased, which means the distance of heat conduction path became longer, the thermal resistance increased considerably. The thermal analysis results imply that the generated heat of the diode is dissipated mainly by the conduction through the route of diode-dummy wafer-bonding wire, which suggests to minimize the length of the wire for the lowest thermal resistance.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2015년도 춘계학술대회
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• pp.829-831
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• 2015

본 연구에서는 비대칭 이중게이트 MOSFET의 채널길이와 채널두께의 비에 따른 문턱전압 및 전도중심의 변화를 분석하고자한다. 비대칭 이중게이트 MOSFET는 상하단 게이트 전압에 의하여 전류흐름을 제어할 수 있어 단채널효과를 감소시킬 수 있다는 장점이 있다. 그러나 채널길이가 감소하면 필연적으로 발생하는 문턱전압의 급격한 변화는 소자 특성에 커다란 영향을 미치고 있다. 특히 상하단의 게이트 전압, 상하단의 게이트 산화막 두께 그리고 도핑분포변화에 따라 발생하는 전도중심의 변화는 문턱전압을 결정하는 중요 요소가 된다. 해석학적으로 문턱전압 및 전도중심을 분석하기 위하여 해석학적 전위분포를 포아송방정식을 통하여 유도하였다. 다양한 채널길이 및 채널두께에 대하여 전도중심과 문턱전압을 계산한 결과, 채널길이와 채널두께의 비 등 구조적 파라미터뿐만이 아니라 도핑분포 및 게이트 전압 등에 따라 전도중심과 문턱전압은 크게 변화한다는 것을 알 수 있었다.

• 대한기계학회논문집B
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• 제41권5호
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• pp.341-346
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• 2017

본 연구는 해석적 접근이 용이한 실리콘 내 포논 평균자유행로(mean free path, MFP) 스펙트럼(spectrum) 열전도 특성 예측 모델을 제시했다. 해석이 용이한 포논 기체 운동론(kinetic theory)을 적용하기 위해, 나노구조물의 현상학적 접근으로 열전도에 관여하는 포논 모드(mode)들만 추출하고, 300 K의 실리콘에 대한 포논의 분산관계(dispersion relations) 및 분극(polarization) 효과가 고려된 포논의 주파수 변화에 따른 비열(specific heat)과 군속도(group velocity) 및 MFP 정보를 사용했다. 300 K의 실리콘 내 포논의 MFP 스펙트럼 열전도율 기여를 계산하고, 기존 실험결과 및 제1원리 기법 결과와 비교하여, 본 방법의 타당함을 보였다. 본 연구를 통해, 나노구조물 열전달 해석모델 개발 및 나노재료 열전달 특성 조정(tailoring) 전략 설계에 필요한 포논 MFP 스펙트럼 열전도 특성 정보를 해석이 용이한 방법으로 구할 수 있는 방법을 제공했다.

• 대한기계학회논문집B
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• 제33권10호
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• pp.820-826
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• 2009

The anisotropic phonon conductions with varying Joule heating rate of the silicon film in Silicon-on-Insulator devices are examined using the electron-phonon interaction model. It is found that the phonon heat transfer rate at each boundary of Si-layer has a strong dependence on the heating power rate. And the phonon flow decreases when the temperature gradient has a sharp change within extremely short length scales such as phonon mean free path. Thus the heat generated in the hot spot region is removed primarily by heat conduction through Si-layer at the higher Joule heating level and the phonon nonlocality is mainly attributed to lower group velocity phonons as remarkably dissimilar to the case of electrons in laser heated plasmas. To validate these observations the modified phonon nonlocal model considering complete phonon dispersion relations is introduced as a correct form of the conventional theory. We also reveal that the relation between the phonon heat deposition time from the hot spot region and the relaxation time in Si-layer can be used to estimate the intrinsic thermal resistance in the parallel heat flow direction as Joule heating level varies.

• 한국전기전자재료학회논문지
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• 제21권9호
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• pp.835-843
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• 2008

We have fabricated the source-drain electrodes for OTFTs by screen printing method and manufactured Ag pastes as conductive paste. To obtain excellent conductivity and screen-printability of Ag pastes, the dispersion characteristics of Ag pastes prepared from two types of acryl resins with different molecular structures and Ag powder treated with caprylic acid, triethanol amine and dodecane thiol as surfactant respectively were investigated. The Ag pastes containing Ag powder treated with dodecane thiol having thiol as anchor group or AA4123 with carboxyl group(COOH) of hydrophilic group as binder resin exhibited excellent dispersity. But, Ag pastes(CA-41, TA-41, DT-41) prepared from AA4123 fabricated the insulating layer since the strong interaction between surface of Ag powder and carboxyl group(COOH) of AA4123 interfered with the formation of conduction path among Ag powders. The viscosity behavior of Ag pastes exhibited shear-thinning flow in the high shear rate range and the pastes with bad dispersion characteristic demonstrated higher shear-thinning index than those with good dispersity due to the weak flocculated network structure. The output curve of OTFT device with a channel length of 107 ${\mu}m$ using screen-printed S-D electrodes from DT-30 showed good saturation behavior and no significant contact resistance. And this device exhibited a saturation mobility of $4.0{\times}10^{-3}$ $cm^2/Vs$, on/off current ratio of about $10^5$ and a threshold voltage of about 0.7 V.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.993-994
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• 2008

Electrochromic (EC) devices are capable of reversibly changing their optical properties upon charge injection and extraction induced by the external voltage. The characteristics of the EC device, such as low power consumption, high coloration efficiency, and memory effects under open circuit status, make them suitable for use in a variety of applications including smart windows and electronic papers. Coloration due to reduction or oxidation of redox chromophores can be used for EC devices (e-paper), but the switching time is slow (second level). Recently, with increasing demand for the low cost, lightweight flat panel display with paper-like readability (electronic paper), an EC display technology based on dye-modified $TiO_2$ nanoparticle electrode was developed. A well known organic dye molecule, viologen, was adsorbed on the surface of a mesoporous $TiO_2$ nanoparticle film to form the EC electrode. On the other hand, ZnO is a wide bandgap II-VI semiconductor which has been applied in many fields such as UV lasers, field effect transistors and transparent conductors. The bandgap of the bulk ZnO is about 3.37 eV, which is close to that of the $TiO_2$ (3.4 eV). As a traditional transparent conductor, ZnO has excellent electron transport properties, even in ZnO nanoparticle films. In the past few years, one-dimension (1D) nanostructures of ZnO have attracted extensive research interest. In particular, 1D ZnO nanowires renders much better electron transportation capability by providing a direct conduction path for electron transport and greatly reducing the number of grain boundaries. These unique advantages make ZnO nanowires a promising matrix electrode for EC dye molecule loading. ZnO nanowires grow vertically from the substrate and form a dense array (Fig. 1). The ZnO nanowires show regular hexagonal cross section and the average diameter of the ZnO nanowires is about 100 nm. The cross-section image of the ZnO nanowires array (Fig. 1) indicates that the length of the ZnO nanowires is about $6\;{\mu}m$. From one on/off cycle of the ZnO EC cell (Fig. 2). We can see that, the switching time of a ZnO nanowire electrode EC cell with an active area of $1\;{\times}\;1\;cm^2$ is 170 ms and 142 ms for coloration and bleaching, respectively. The coloration and bleaching time is faster compared to the $TiO_2$ mesoporous EC devices with both coloration and bleaching time of about 250 ms for a device with an active area of $2.5\;cm^2$. With further optimization, it is possible that the response time can reach ten(s) of millisecond, i.e. capable of displaying video. Fig. 3 shows a prototype with two different transmittance states. It can be seen that good contrast was obtained. The retention was at least a few hours for these prototypes. Being an oxide, ZnO is oxidation resistant, i.e. it is more durable for field emission cathode. ZnO nanotetropods were also applied to realize the first prototype triode field emission device, making use of scattered surface-conduction electrons for field emission (Fig. 4). The device has a high efficiency (field emitted electron to total electron ratio) of about 60%. With this high efficiency, we were able to fabricate some prototype displays (Fig. 5 showing some alphanumerical symbols). ZnO tetrapods have four legs, which guarantees that there is one leg always pointing upward, even using screen printing method to fabricate the cathode.