• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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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.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.839-841
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• 2015

본 연구에서는 비대칭 이중게이트 MOSFET의 채널길이와 채널두께의 비에 따른 드레인 유도 장벽 감소 현상의 변화에 대하여 분석하고자한다. 드레인 전압이 소스 측 전위장벽에 영향을 미칠 정도로 단채널을 갖는 MOSFET에서 발생하는 중요한 이차효과인 드레인 유도 장벽 감소는 문턱전압의 이동 등 트랜지스터 특성에 심각한 영향을 미친다. 드레인 유도 장벽 감소현상을 분석하기 위하여 포아송방정식으로부터 급수형태의 전위분포를 유도하였으며 차단전류가 $10^{-7}A/m$일 경우 비대칭 이중게이트 MOSFET의 상단게이트 전압을 문턱전압으로 정의하였다. 비대칭 이중게이트 MOSFET는 단채널효과를 감소시키면서 채널길이 및 채널두께를 초소형화할 수 있는 장점이 있으므로 본 연구에서는 채널길이와 두께 비에 따라 드레인 유도 장벽 감소를 관찰하였다. 결과적으로 드레인 유도 장벽 감소 현상은 단채널에서 크게 나타났으며 하단게이트 전압, 상하단 게이트 산화막 두께 그리고 채널도핑 농도 등에 따라 큰 영향을 받고 있다는 것을 알 수 있었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.26-31
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• 2002

To realize a high integrated Flash memory utilizing SONOS memory devices, the NOR type 1TC(one Transistor Cell) SONOS Flash arrays are fabricated and characterized. This SONOS Flash arrays with common source lines are designed and fabricated by conventional 0.35$\mu\textrm{m}$ CMOS process. The thickness of ONO for memory cell is tunnel oxide of 34${\AA}$, nitride of 73${\AA}$ and blocking oxide of 34${\AA}$. To investigate operating characteristics, CHEI(Channel Hot Electron Injection) method and Bit line erase method are selected as the write operation and the erase method, respectively. The disturbance characteristics according to the write/erase/read cycling are also examined. The degradation characteristics are investigated and then the reliability of SONOS flash memory is guaranteed.

• JSTS:Journal of Semiconductor Technology and Science
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• v.5 no.2
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• pp.136-147
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• 2005

A theoretical design evaluation based on a hydrodynamic transport simulation of strained Si-SiGe on insulator (SSOI) type nMOSFETs is reported. Although, the net performance improvement is quite limited by the short channel effects, simulation results clearly show that the strained Si-SiGe type nMOSFETs are well-suited for gate lengths down to 20 nm. Simulation results show that the improvement in the transconductance with decreasing gate length is limited by the long-range Coulomb scattering. An influence of lateral and vertical diffusion of shallow dopants in the source/drain extension regions on the device performance (i.e., threshold voltage shift, subthreshold slope, current drivability and transconductance) is quantitatively assessed. An optimum layer thickness ($t_{si}$ of 5 and $t_{sg}$ of 10 nm) with shallow Junction depth (5-10 nm) and controlled lateral diffusion with steep doping gradient is needed to realize the sub-50 nm gate strained Si-SiGe type nMOSFETs.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.2
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• pp.181-189
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• 1985

The effect of the Coriolis force on the 2-D turbulent boundary layer which is developed in the side wall of the rotating rectangular flow channel was investigated. In this study, we measured mean velocities, turbulent velocity components(axial as well as lateral ones) and Reynolds stresses of the turbulent boundary layer. For high Reynolds number flows, the turbulent boundary layer without pressure gradient is hardly affected by the rotation. For low Reynolds number flows, however, the shearing stress at suction side decreases. Consequently, the velocity near the wall become slower so that the thickness of the viscous sublayer expands. On the other hand, the velocity near the wall at pressure side turns out increased.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.557-560
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• 2002

In this study, simulation of weak shock waves are peformed by a two-dimensional thermal fluid or compressible fluid model of the lattice Boltzmann method. The shock wave represents an abrupt change in fluids properties, in which finite variations in pressure, internal energies, and density occur over the shock thickness. The characteristics of the proposed model with a simple distribution function is verified by calculation of the sound speeds, and the shock tube problem. The reflection of a weak shock wave by wedge propagating in a channel is performed. The results agree well with those by finite difference method or by experiment. In the simulation of unsteady shock wave diffraction around a sharp corner, we show a flow field of vortical structure near the comer.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1815-1820
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• 2008

Self-catalytic behavior of combustion-synthesized carbon nanotubes (CNTs) is evaluated using a double-faced wall stagnation flow burner with a CNT-deposited stainless steel plate wall. CNT formation is observed using field-emission scanning and transmission electron microscopies and Raman spectroscopy. A self-catalytic behavior of multi-walled CNTs (MWCNTs) shows the enhanced ratio of channel diameter to tube wall thickness and the enhanced intensity ratio of G-band to D-band in Raman spectroscopy, implying that the quality of metal-catalytic, flame-synthesized MWCNTs can be much improved via a CNT self-catalytic flame-synthesis process. Thus, using a DWSF burner through the self-catalytic process has potential in mass production of CNTs having much improved quality.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1129-1131
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• 2008

We injection molded a plate with micro surface features including micro prizms & micro channels patterns on its surface and investigated the replication of the micro features depending on the mold temperature which is one of typical process parameters. The size of the patterns were 8um, 10um, 15um of prizm features & 15um, 30um, 45um of channel features. The size of the plate is about $400mm{\times}400mm$ and the thickness is 1mm of plate. the repliction of the mucro features turned out to depend on the mold temperature and also the location on the plate. The pressure and the feature of the melt in the cavity were also measured in real-time for the investigation on the micro feature replication.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.387.1-387.1
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• 2014

A new class of temperature-sensing materials is demonstrated along with their integration into transparent and flexible field-effect transistor (FET) temperature sensors with high thermal responsivity, stability, and reproducibility. The novelty of this particular type of temperature sensor is the incorporation of an R-GO/P(VDF-TrFE) nanocomposite channel as a sensing layer that is highly responsive to temperature, and is optically transparent and mechanically flexible. Furthermore, the nanocomposite sensing layer is easily coated onto flexible substrates for the fabrication of transparent and flexible FETs using a simple spin-coating method. The transparent and flexible nanocomposite FETs are capable of detecting an extremely small temperature change as small as $0.1^{\circ}C$ and are highly responsive to human body temperature. Temperature responsivity and optical transmittance of transparent nanocomposite FETs were adjustable and tuneable by changing the thickness and R-GO concentration of the nanocomposite.

• Journal of the Korean institute of surface engineering
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• v.41 no.6
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• pp.274-278
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• 2008

3-dimensional numerical analysis for a rectangular magnetron cathode model is done to predict cooling characteristics of high power sputtering system for ZnO deposition. It includes cooling channel design, heat transfer analysis of a target, bonding layer and backing plate. In order to model erosion profiles of a target, ion current density distribution from 3D Monte Carlo simulation is used to distribute total sputtering power to 5 discrete regions. At 3 kW of sputtering power and cooling water flow of 1 liter/min at $10^{\circ}C$, the maximum surface temperature was $45.8^{\circ}C$ for a flat new target and $156^{\circ}C$ for a target eroded by 1/3 of its thickness, respectively.