• Korean Journal of Materials Research
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• v.29 no.9
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• pp.547-552
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• 2019

In the present study, the thermal conductivity of a silicon nitride($Si_3N_4$) thin-film is evaluated using the dual-wavelength pump-probe technique. A 100-nm thick $Si_3N_4$ film is deposited on a silicon (100) wafer using the radio frequency plasma enhanced chemical vapor deposition technique and film structural characteristics are observed using the X-ray reflectivity technique. The film's thermal conductivity is measured using a pump-probe setup powered by a femtosecond laser system of which pump-beam wavelength is frequency-doubled using a beta barium borate crystal. A multilayer transient heat conduction equation is numerically solved to quantify the film property. A finite difference method based on the Crank-Nicolson scheme is employed for the computation so that the experimental data can be curve-fitted. Results show that the thermal conductivity value of the film is lower than that of its bulk status by an order of magnitude. This investigation offers an effective way to evaluate thermophysical properties of nanoscale ceramic and dielectric materials with high temporal and spatial resolutions.

• JSTS:Journal of Semiconductor Technology and Science
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• v.8 no.2
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• pp.111-114
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• 2008

We studied the influence of nanocrystalline silicon (nc-Si) thin film thickness on top gate nc-Si thin film transistor (TFT) fabricated at $180^{\circ}C$. The nc-Si thickness affects the characteristics of nc-Si TFT due to the nc-Si growth similar to a columnar. As the thickness of nc-Si increases from 40 nm to 200 nm, the grain size was increased from 20 nm to 40 nm. Having a large grain size, the thick nc-Si TFT surpasses the thin nc-Si TFT in terms of electrical characteristics such as field effect mobility. The channel resistance was decreased due to growth of the grain. We obtained the experimental results that the field effect mobility of the fabricated devices of which nc-Si thickness is 60, 90 and 130 nm are 26, 77 and $119\;cm^2/Vsec$, respectively. The leakage current, however, is increased from $7.2{\times}10^{-10}$ to $1.9{\times}10^{-8}\;A$ at $V_{GS}=-4.4\;V$ when the nc-Si thickness increases. It is originated from the decrease of the channel resistance.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.349-349
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• 2009

High quality ZnO:Al films were prepared on glass substrates by in-line RF magnetron sputtering and their surface morphologies were modified by wet-etching process in dilute acid solution to improve optical properties for application to silicon thin film solar cells as front electrode. The as-deposited films show a strong preferred orientation in [001] direction under our experimental conditions. A low resistivity below $5{\times}10^{-4}{\Omega}{\cdot}cm$ and high optical transmittance above 80% in a visible range are achieved in the films deposited at optimized conditions. After wet-etching, the surface morphologies of the films are changed dramatically depending on the deposition conditions, especially working pressure. The optical properties such as total/diffuse transmittance, haze and angular resolved distribution of light are varied significantly with the surface morphology feature, whereas the electrical properties are seldom changed. The cell performances of silicon thin film solar cells fabricated on the textured films are also evaluated in detail with comparison of commercial $SnO_2$:F films.

• Journal of the Korean Physical Society
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• v.73 no.9
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• pp.1329-1333
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• 2018

We investigated the mechanism of mobility enhancement after the dehydrogenation process in polycrystalline silicon (poly-Si) thin films. The dehydrogenation process was performed by using an in-situ CVD chamber in a $N_2$ ambient or an ex-situ furnace in air ambient. We observed that the dehydrogenated poly-Si in a $N_2$ ambient had a lower oxygen concentration than the dehydrogenated poly-Si annealed in an air ambient. The in-situ dehydrogenation increased the (111) preferred orientation of poly-Si and reduced the oxygen concentration in poly-Si thin films, leading to a reduction of the trap density near the valence band. This phenomenon gave rise to an increase of the field-effect mobility of the poly-Si thin film transistor.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.4
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• pp.292-297
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• 2003

We fabricated a single crystal silicon thin film transistor for active matrix organic light emitting displays(AMOLEDs) using silicon on insulator wafer (SOI wafer). Poly crystal silicon thin film transistor(poly-Si TFT) Is actively researched and developed nowsdays for a pixel switching devices of AMOLEDs. However, poly-Si TFT has some disadvantages such as high off-state leakage currents and low field-effect mobility due to a trap of grain boundary in active channel. While single crystal silicon TFT has many advantages such as high field effect mobility, low off-state leakage currents, low power consumption because of the low threshold voltage and simultaneous integration of driving ICs on a substrate. In our experiment, we compared the property of poly-Si TFT with that of SOI TFT. Poly-Si TFT exhibited a field effect mobility of 34 $\textrm{cm}^2$/Vs, an off-state leakage current of about l${\times}$10$\^$-9/ A at the gate voltage of 10 V, a subthreshold slope of 0.5 V/dec and on/off ratio of 10$\^$-4/, a threshold voltage of 7.8 V. Otherwise, single crystal silicon TFT on SOI wafer exhibited a field effect mobility of 750 $\textrm{cm}^2$/Vs, an off-state leakage current of about 1${\times}$10$\^$-10/ A at the gate voltage of 10 V, a subthreshold slope of 0.59 V/dec and on/off ratio of 10$\^$7/, a threshold voltage of 6.75 V. So, we observed that the properties of single crystal silicon TFT using SOI wafer are better than those of Poly Si TFT. For the pixel driver in AMOLEDs, the best suitable pixel driver is single crystal silicon TFT using SOI wafer.

• Journal of the Korean Ceramic Society
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• v.46 no.1
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• pp.10-15
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• 2009

We have fabricated silicon-rich silica thin films via RF magnetron sputtering using a SiO target. Thickness evolution and microstructure change of such $SiO_x$ (1$SiO_x$ thin films turned out to be mainly responsible for the increase of refractive index.

• Journal of the Korean institute of surface engineering
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• v.25 no.6
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• pp.287-292
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• 1992

Silicon nitride thin film (SiNx) was deposited onto the 3inch silicon wafer using an electron cyclotron resonance (ECR) plasma apparatus. The thin films which were deposited by changing the SiH4N2 gas flow rate ratio at 1.5mTorr without substrate heating were analyzed through the x-ray photo spectroscopy (XPS) and ellipsometer measurements, etc. Silicon nitride thin films prepared by the electron cyclotron resonance plasma chemical vapor deposition method at low substrate temperature (<10$0^{\circ}C$) exhibited excellent physical and electrical properties. The very uniform and good quality silicon nitride thin films were obtained. The characteristics of electron cyclotron resonance plasma were inferred from the analyzed results of the deposited films.

• Journal of the Korean Ceramic Society
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• v.37 no.6
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• pp.596-603
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• 2000

The hardness and elastic modulus of three bulk materials are computed from the load and displacement data which are measured during basic nanoindentation test and compared with values determined by independent means to assess the accuracy of the method. The results show that with this technique, modulus and hardness and elastic modulus profile through depth of silicon nitride and silicon oxynitride films. The results show that for silicon nitride film deposited on silicon, hardness and elastic modulus increase as the volume ratio of NH3 : SiH4, which had been used for deposition, increases up to 20.0; and for silicon oxynitride film on silicon, the hardness and elastic modulus profile changes distinctly as the relative amount of oxygen in deposition gas mixture changes.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.267-268
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• 2010

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.233-233
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• 2007