• Journal of Mechanical Science and Technology
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• 제19권6호
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• pp.1378-1389
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• 2005

This work provides the fundamental knowledge of energy transport characteristics during very short-pulse laser heating of semiconductors from a microscopic viewpoint. Based on the self-consistent hydrodynamic equations, in-situ interactions between carriers, optical phonons, and acoustic phonons are simulated to figure out energy transport mechanism during ultrafast pulse laser heating of a silicon substrate through the detailed information on the time and spatial evolutions of each temperature for carriers, longitudinal optical (LO) phonons, acoustic phonons. It is found that nonequilibrium between LO phonons and acoustic phonons should be considered for ultrafast pulse laser heating problem, two-peak structures become apparently present for the subpicosecond pulses because of the Auger heating. A substantial increase in carrier temperature is observed for lasers with a few picosecond pulse duration, whereas the temperature rise of acoustic and phonon temperatures is relatively small with decreasing laser pulse widths. A slight lagging behavior is observed due to the differences in relaxation times and heat capacities between two different phonons. Moreover, the laser fluence has a significant effect on the decaying rate of the Auger recombination.

• 한국표면공학회지
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• 제22권3호
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• pp.109-117
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• 1989

The effect of heft treatment on the characteristic properties of insulation layer is studied for two kinds of non-oriented silicon steels, which were insulation-coates with various kinds of inorganic and inorganic-organic complex coating solutions. In addition, how the carbon contained in the insulation layer would affect the carbon content and the magnetic properties of the steel substrates is examined. Lower temperature heat treftment ($480^{\circ}C$ for 0.5hr) is found to render morw favorable surface qualities, wheras higher temperature heat treatment ($790^{\circ}C$ for 2hr) better core loss due to grin growt occurred during the heat treatment. Decarburization of the steel substrate is also found unaffectrd by the presence of carbon in the insulation layer.

• 한국세라믹학회지
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• 제32권4호
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• pp.419-428
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• 1995

Polycrystalline silicon carbide (SiC) thick films were depostied by low pressure chemical vapor deposition (LPCVD) using CH3SiCl3 (MTS) and H2 gaseous mixture onto isotropic graphite substrate. Effects of deposition variables on the SiC film were investigated. Deposition rate had been found to be surface-reaction controlled below reactor temperature of 120$0^{\circ}C$ and mass-transport controlled over 125$0^{\circ}C$. Apparent activation energy value decreased below 120$0^{\circ}C$ and deposition rate decreased above 125$0^{\circ}C$ by depletion effect of the reactant gas in the direction of flow in a horizontal hot wall reactor. Microstructure of the as-deposited SiC films was strongly influenced by deposition temperature and position. Microstructural change occurred greater in the mass transport controlled region than surface reaction controlled region. The as-deposited SiC layers in this experiment showed stoichiometric composition and there were no polytype except for $\beta$-SiC. The preferred orientation plane of the polycrystalline SiC layers was (220) plane at a high reactant gas concentration in the mass transfer controlled region. As depletion effect of reactant concentration was increased, SiC films preferentially grow as (111) plane.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.420-420
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• 2013

We investigated oxygen plasma effect on defect states near the interface of AlGaN/GaN High Electron Mobility Transistor (HEMT) structure grown on a silicon substrate. After the plasma treatment, electrical properties were evaluated using a frequency dependant Capacitance-Voltage (C-V) and a temperature dependant C-V measurements, and a deep level transient spectroscopy (DLTS) method to study the change of defect densities. In the depth profile resulted from the temperature dependant C-V, a sudden decrease in the carrier concentration for two-dimensional electron gas (2DEG) nearby 250 K was observed. In C-V measurement, the interface states were improved in case of the oxygen-plasma treated samples, whereas the interface was degraded in case of the nitrogen-plasma treated sample. In the DLTS measurement, it was observed the two kinds of defects well known in AlGaN/GaN structure grown on sapphire substrate, which have the activation energies of 0.15 eV, 0.25 eV below the conduction band. We speculate that this defect state in AlGaN/GaN on the silicon substrate is caused from the decrease in 2DEG's carrier concentrations. We compared the various DLTS signals with filling pulse times to identify the characteristics of the newly found defect. In the filling pulse time range under the 80 us, the activation energies changed as the potential barrier model. On the other hand, in the filling pulse time range above the 80 us, the activation energies changed as the extended potential model. Therefore, we suggest that the found defect in the AlGaN/GaN/Si structure could be the extended defect related with AlGa/N/GaN interface states.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.205-207
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• 2008

The new process for hybrid silicon thin film transistor (TFT) using DPSS laser has been developed for realizing both low-temperature poly-Si (LTPS) TFT and a-Si:H TFT on the same substrate as a backplane of active matrix liquid crystal display. LTPS TFTs are integrated on the peripheral area of the panel for gate driver integrated circuit and a-Si:H TFTs are used as a switching device for pixel in the active area. The technology has been developed based on the current a-Si:H TFT fabrication process without introducing ion-doping and activation process and the field effect mobility of $4{\sim}5\;cm^2/V{\cdot}s$ and $0.5\;cm^2/V{\cdot}s$ for each TFT was obtained. The low power consumption, high reliability, and low photosensitivity are realized compared with amorphous silicon gate driver circuit and are demonstrated on the 14.1 inch WXGA+ ($1440{\times}900$) LCD Panel.

• 전자공학회논문지 IE
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• 제43권2호
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• pp.11-15
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• 2006

FPD (flat panel display)의 능동구동 (active matrix) 방식의 플렉시블 디스플레이를 위해 PES의 플라스틱 기판위에 극저온 다결정 실리콘 박막 트랜지스터를 제작하였다. 상온에서도 박막의 증착이 가능한 RF 마크네트론 스퍼터링과 양질의 다결정 실리콘 박막을 얻을 수 있다고 알려진 XeCl 엑시머 레이져 열처리를 이용하였으며 모든 공정이 150$^{\circ}C$ 이하의 극저온에서 이루어졌다. 플라스틱 기판에 형성한 실리콘 박막 트랜지스터는 344 $mJ/cm^2$ 의 에너지 밀도에서 결정화 하였을 때 이동도 63.64$cm^2/V$ 로 기판에 회로를 집적할 수 있기에 충분한 특성을 얻을 수 있었다.

• 대한전자공학회논문지SD
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• 제41권10호
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• pp.51-56
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• 2004

광소자의 재료물질로서 특성이 우수하며 열광학계수가 큰 silicon을 기반으로 한 SOI (Silicon-on-insulator)를 사용하여 열광학 1×2 광스위치를 제안, 제작하였다. SOI wafer는 도파로가 형성될 상위 Si 층(n=3.5)과 클래딩 영역이 될 산화막 매립층(n=1.5) 그리고 기판인 Si인 3층으로 이루어진다. BPM(Beam propagation method) 전산모의를 통해 20dB 이상의 누화특성을 갖는 단일모드의 1×2 비대칭 y-분기 광도파로를 형성하고, 열확산 전산모의를 통해 금속열선을 설계 제작하였다. 제작된 광스위치는 약 3.5 watts의 구동 전력에서 20dB 이상의 채널간 누화가 측정되었다.

• ETRI Journal
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• 제26권3호
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• pp.257-261
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• 2004

We grew amorphous SiCN films by pulsed laser deposition using mixed targets. The targets were fabricated by compacting a mixture of SiC and $SiC-{Si_3}{N_4}$ powders. We controlled the film stoichiometry by varying the mixing ratio of the target and the target-to-substrate distance. The mixing ratio of the target had a dominant effect on the film composition. We consider the structures of the SiCN films deposited using 30~70 wt.% SiC in the target to be an intermediate phase of SiC and $SiN_x$. This provides the possibility of growing homogeneous SiCN films with a mixed target at a moderate target-to-substrate distance.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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• pp.1007-1010
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• 2004

We report crystallization of a-Si using XeCl excimer laser annealing [1] on the plastic substrate. We tried to obtain higher crystallinity as the effect of $CeO_2$ seed layer patterned. Also, we tried to control the direction of crystallization growth of silicon layer for lateral growth as the type of $CeO_2$ pattern. This crystallization method plays an important role in low temperature poly-Si (LTPS) [2] process and flexible display.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 D
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• pp.1337-1339
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• 1998

The trench termination scheme is introduced for high voltage devices. The curvature of the depletion region at field limiting ring is critical factor to determine the breakdown voltage. The smooth curvature of the depletion junction alleviate the electric field crowding effect around this region. In the trench field limiting ring, the radius of the depletion region is smaller than conventional field limiting ring, but the distance between every trench is spaced small enough to punchthrough before initiation of local breakdown. The trench field limiting ring on silicon can ne formed by RIE followed by oxidation on side wall surface of the trench, and polysilicon filling. The combined termination of this trench floating field ring and field plate have been designed and analyzed. The breakdown simulation by 2-dimensional TCAD shows that the cylindrical junction breakdown voltage for substrate doping might be 99 percent of the ideal breakdwon voltage for substrate doping concentration of $3\times10^{14}cm^{-3}$ with about $100{\mu}m$ of lateral termination width.