• Journal of the Semiconductor & Display Technology
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• v.13 no.3
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• pp.27-33
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• 2014

To develop high efficiency crystalline solar cells, the $SiN_x$ film for surface passivation and anti-reflection coating is very important and it is generally deposited by PECVD. In this paper, the $SiN_x$ film deposited by Hot-Wire chemical vapor deposition(HWCVD) that has no plasma damage was studied. First, to optimize the $SiN_x$ film deposition process, $SiH_4$ gas rate and substrate temperature were varied and then refractive index and thickness were measured. When $SiH_4$ gas rate was 22sccm and substrate temperature was $100^{\circ}C$, refractive index was 1.94 and higher than that of other process conditions. Second, the lifetime was measured by varying the annealing temperature and time. The annealing process was made from 5 to 30 minutes at $300{\sim}500^{\circ}C$. When the annealing temperature was $100^{\circ}C$ and time was 10minute, the lifetime was the highest. The lifetime of annealed samples was also measured after the firing process at $975^{\circ}C$. Although the lifetime of all samples was decreased by firing process, the lifetime of annealed samples before the firing process was higher than that of fired samples only. Finally, the characteristics of solar cells with HWCVD $SiN_x$ film were measured.

• Journal of the Korean Chemical Society
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• v.38 no.7
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• pp.473-479
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• 1994

Tungsten thin film was deposited on p-(100) silicon substrate by using the LPCVD(low pressure chemical vapor deposition) technique. $WF_6$ was used as a source gas for tungsten and $SiH_4$ was used as a reducing gas for $WF_6$. Tungsten thin film was deposited by either SiH4 or Si substrate reduction of $WF_6$ under cold-wall condition and it was deposited by $SiH_4$ reduction of $WF_6$ under hot-wall condition. The crystal structure of deposited thin film under both conditions were identified to be bcc (body centered cubic). The physical and electrical properties of deposited thin films were investigated. The deposited film under hot-wall condition changed to $WSi_2$ film by the annealing under $800^{\circ}C.$ From the experimental results and theoretical considerations, the change of the crystal structure of the thin film by annealing was discussed. $WSi_2$ thin film, which was known to have good compatibility with Si substrate, could be produced under hot-wall condition although the film properties were superior under cold-wall condition.

• Korean Journal of Materials Research
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• v.1 no.2
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• pp.77-85
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• 1991

In this study we have investigated surface morphologies of as-deposited silicon films on the various deposition conditions using LPCVD(Low Pressure Chemical Vapor Deposition) System. The processing conditions such as deposition temperature, pressure and flow rate of $SiH_4$ gas were found to determine the surface morphology. The optimum temperature of maximum effective surface area increased with increasing the deposition pressure and the flow rate of $SiH_4$ gas, These experimental results were also in quite good agreement with the equation derived under the assumption that the maximum effective surface area is obtained on the condition of maximum nucleation rate.

• Korean Journal of Metals and Materials
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• v.50 no.8
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• pp.613-618
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• 2012

We report on electrical and mechanical properties of silicon nitride ($SiN_x$) films deposited by a plasma enhanced chemical vapor deposition (PECVD) method at $200^{\circ}C$ from $SiH_4$ highly diluted in $N_2$. The films were also prepared from $SiH_4$ diluted in He for comparison. The $N_2$ dilution was also effective in improving adhesion of the $SiN_x$ films, fascilitating construction of thin film transistors (TFTs). Metal-insulator-semiconductor (MIS) and Metal-insulator-Metal (MIM) structures were used for capacitance-voltage (C-V) and current-voltage (I-V) measurements, respectively. The resistivity and breakdown field strength of the $SiN_x$ films from $N_2$-diluted $SiH_4$ were estimated to be $1{\times}10^{13}{\Omega}{\cdot}cm$, 7.4 MV/cm, respectively. The MIS device showed a hysteresis window and a flat band voltage shift of 3 V and 0.5 V, respectively. The TFTs fabricated by using these films showed a field-effect mobility of $0.16cm^2/Vs$, a threshold voltage of 3 V, a subthreshold slope of 1.2 V/dec, and an on/off ratio of > $10^6$.

• Composites Research
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• v.36 no.5
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• pp.377-382
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• 2023

To enhance the performance of graphene-based devices, it is of great importance to better understand the interfacial interaction of graphene with its underlying substrates. In this study, the adhesion energy of monolayer graphene placed on dielectric substrates was characterized using mode I fracture tests. Large-area monolayer graphene was synthesized on copper foil using chemical vapor deposition (CVD) with methane and hydrogen. The synthesized graphene was placed on target dielectric substrates using polymer-assisted wet transfer technique. The monolayer graphene placed on a substrate was mechanically delaminated from the dielectric substrate by mode I fracture tests using double cantilever beam configuration. The obtained force-displacement curves were analyzed to estimate the adhesion energies, showing 1.13 ± 0.12 J/m² for silicon dioxide and 2.90 ± 0.08 J/m² for silicon nitride. This work provides the quantitative measurement of the interfacial interactions of CVD-grown graphene with dielectric substrates.

• Resources Recycling
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• v.22 no.2
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• pp.22-28
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• 2013

In the present study, the possibility of recovering and recycling the silicon carbide(SiC) from a silicon sludge by removing Fe and Si impurities was investigated. Si and SiC were separated from the silicon sludge using centrifugation. The separated SiC concentrate consisted of Fe, Si and SiC, in which Fe and Si were removed to recover the pure SiC. Leaching with acid/alkali solution was compared with the vapor-phase chlorination. The Fe concentration removed in the SiC was 49 ppm, and it was separated by leaching with 1 M HCl solution at $80^{\circ}C$ for 1 h. The Si concentration removed in the SiC was 860 ppm, and it was separated by leaching with 1M NaOH solution at $50^{\circ}C$ for 1 h. The SiC concentrate was chlorinated in a tubular reactor, 2.4 cm in diameter and 32 cm in length. The boat filled with SiC concentrate was located at the midpoint of the alumina tube, then, the chlorine and nitrogen gas mixture was introduced. The Fe and Si concentration removed in the SiC were 48 ppm and 405 ppm, respectively, at $500^{\circ}C$ reactor temperature, 4 h reaction time, 300 cc/min gas flow rate, and 10% $Cl_2$ gas mole fraction.

• Transactions on Electrical and Electronic Materials
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• v.13 no.4
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• pp.192-195
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• 2012

We reported diborane ($B_2H_6$) doped wide bandgap hydrogenated amorphous silicon oxide (p-type a-SiOx:H) films prepared by using silane ($SiH_4$) hydrogen ($H_2$) and nitrous oxide ($N_2O$) in a radio frequency (RF) plasma enhanced chemical vapor deposition (PECVD) system. We improved the $E_{opt}$ and conductivity of p-type a-SiOx:H films with various $N_2O$ and $B_2H_6$ ratios and applied those films in regards to the a-Si thin film solar cells. For the single layer p-type a-SiOx:H films, we achieved an optical band gap energy ($E_{opt}$) of 1.91 and 1.99 eV, electrical conductivity of approximately $10^{-7}$ S/cm and activation energy ($E_a$) of 0.57 to 0.52 eV with various $N_2O$ and $B_2H_6$ ratios. We applied those films for the a-Si thin film solar cell and the current-voltage characteristics are as given as: $V_{oc}$ = 853 and 842 mV, $J_{sc}$ = 13.87 and 15.13 $mA/cm^2$. FF = 0.645 and 0.656 and ${\eta}$ = 7.54 and 8.36% with $B_2H_6$ ratios of 0.5 and 1% respectively.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.2
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• pp.57-62
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• 2003

Nano-bending method is presented to measure the Poisson's ratio of thinfilms for MEMS (Micro-Electro-Mechanical Systems) applicaiton. The douvle-ring specimen is designed and fabricated based on the surface micromachining process to facilitate the measurement of the Poisson's ratio. The Poisson's ratio can be obtained through analyzing the linear load-displacement relationship of the double ring specimen subjected to nano-indenter loading. The Present nano-bending mehod is an in-situ measurement approach due to the compatibility to the surface micromachining process. The Poisson's ratio is locally obtained at the location of the double ring specimen with micro dimension. To validate the nano-bending method, the Poisson's ratio of LPCVD (Low Pressure Chemical Vapor Deposition) poly-silicon with thickness of 2.3㎛ is investigated. Experimental results reveal that the Poisson's ratio of the poly-silicon film is 0.2569. The standard deviation of the nano-bending measurement for the stiffness of double ring specimens is 2.66%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.280-284
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• 2004

Multicrystalline silicon wafers were textured in an alkaline bath, basically using sodium hydroxide and in acidic bath, using mainly hydrofluoric acid (HF), nitric acid $(HNO_3)$ and de-ionized water (DIW). Some wafers were also acid polished for the comparative study. Comparison of average reflectance of the samples treated with the new recipe of acidic solution showed average diffuse reflectance less than even 5 percent in the optimized condition. Solar cells were thus fabricated with the samples following the main steps such as phosphorus doping for emitter layer formation, silicon nitride deposition for anti-reflection coating by plasma enhanced chemical vapor deposition (PECVD) and front surface passivation, screen printing metallization, co-firing in rapid thermal processing (RTP) Furnace and laser edge isolation and confirmed >14 % conversion efficiency from the best textured samples. This isotropic texturing approach can be instrumental to achieve high efficiency in mass production using relatively low cost silicon wafers as starting material.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.10
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• pp.83-90
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• 1998

The effects of dopant activation anneal on GOI (Gate Oxide Integrity) of MOS capacitor with amorphous silicon gate electrode were investigated. It was found that the amorphous silicon gate electrode was crystallized and the dopant atoms were sufficiently activated by activation anneal. The mechanical stress of gate electrode that reveals large compressive stress in amorphous state, was released with increase of anneal temperature from $700^{\circ}C$ to 90$0^{\circ}C$. The resistivity of gate electrode polycrystalline silicon film is decreased by the increase of anneal temperature. The reliability of thin gate oxide and interface properties between oxide and silicon substrate greatly depends on the activation anneal temperature. The charge trapping characteristics as well as oxide reliability are improved by the anneal of 90$0^{\circ}C$ compare to that of $700^{\circ}C$ or 80$0^{\circ}C$. Especially, the lifetimes of the thin gate oxide estimated by TDDB method is 3$\times$10$^{10}$ for the case of $700^{\circ}C$ anneal, is significantly increased to 2$\times$10$^{12}$ for the case of 90$0^{\circ}C$ anneal. Finally, the interface trap density is reduced with relaxation of mechanical stress of gate electrode.