• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.51-51
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• 2011

We have grown nanocrystalline graphite on sapphire substrate by using solid carbon source molecular beam epitaxy. Changes of structure from amorphous carbon to nanocrystalline graphite controlled by the growth temperature have been investigated by Raman spectroscopy. Raman spectra show D, G, and 2D peaks, whose intensities vary on the growth temperature. Atomic force microscopy reveals that the surface is very flat. Sapphire substrates of different cutting direction produce similar results. Simulations suggest that the interaction between carbon and oxygen causes disorders. Electrical transport measurements exhibit a Dirac-like peak, including a carrier type change by an external gate voltage bias.

• Journal of the Korean Ceramic Society
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• v.32 no.10
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• pp.1103-1110
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• 1995

Silicon carbide (SiC) films have been deposited on the isotropic graphite by chemical vapor deposition. Change of deposition parameters affected significantly the microstructure and preferred orientation of SiC films. Preferred orientation of SiC films was (111) or (220), and microstructure showed the startified structure consisting of small crystallite or faceted columnar structure depending on the deposition parameters. For microhardness, (111) oriented film and stratified structure were superior to (220) oriented film and faceted columnar structure, respectively. Surface of (111) oriented films was less rough than that of (220) oriented films. Adhesion force between graphite substrate and SiC films was above 100N for crystalline films and 49N for amorphous film.

• Journal of Surface Science and Engineering
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• v.29 no.6
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• pp.648-653
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• 1996

Hydrogenated amorphous carbon(a-C:H) films are prepared by rf plasma CVD in a $CH_4$ source gas system diluted with Ar of $H_2$. The spectra of emissive and reactive species in the plasma are detected using in stiu optical emission spectroscopy. Inaddition, the relationship between the film properties which can be varied by the deposition parameters and the Raman spectra is studied. In the $CH_4/H_2$ gas system, the emission intensities of CH and $H \tau$ decrease and those of $H \alpha$, $H \beta$, $C_2$ and Ar increase with increasing $H_2$ concentration, The formation of $C_2$ and CH in the $CH_4/Ar/H_2$ gas system is greatly suppressed by hydrogen addition and the excess of hydrogen addition is found to form graphite structure. The $C_2$ formation in the gas phase enhances a-C:H film formation.

• Journal of Astronomy and Space Sciences
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• v.9 no.2
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• pp.183-192
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• 1992

We have investigated the properties of dust grains in the envelopes of infrared carbon stars by testing various radiative transfer model spectra with different stellar and enveloped parameters. We have deduced a new opacity pattern for the dust grains reflecting both the experimental data and the model fitting with recent infrared observations. The best pattern we find is very similar to amorphous carbon with a slight modification that could be attributed to some unknown dust grain materials. Unlike oxygen-rich dust grains, the optical properties of carbon grains do not show any reasonable tendency of temperature dependence. We find that the Planck mean values of radiation pressure efficiency factors for the modified amorphous carbon are much larger than those for graphite.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.406-408
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• 1999

Amorphous carbon nitride thin films were prepared on pretreated silicon(100) substrate in sputtering graphite target by activated gas phase using RF reactively sputtering. We measured the FT-IR spectrum to identify C=N(nitrile)stretching mode(2200cm$\^$-1/), C-H stretching mode(2800cm$\^$-1/), C-H bending mode, C=C stretching mode C=N(imino) mode(1680cm$\^$-1/ ), and the XPS to investigate chemical structure of surface. By the results of FT-H and XPS spectrum, We confirmed that amorphous carbon nitride films with typel (C(1s): 285.9[eV], N(1s): 398.5[ev]) and type 2(C1s): 287.5[eV, N(1s): 400.2[eV]) successfully were synthesized by RF reactively sputtering

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.155-158
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• 2015

The traditional view of dust in the interstellar medium is that it is made of graphite and silicates. In this paper, we discuss the evidence for complex organics being a major component of interstellar dust. Comparison between astronomical infrared spectra and laboratory spectra of amorphous carbonaceous materials suggests that organics of mixed aromatic-aliphatic structures are widely present in circumstellar, interstellar, and galactic environments. Scenarios for the synthesis of these compounds in the late stages of stellar evolution are presented.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.7
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• pp.475-480
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• 2018

We investigated the tribological properties of amorphous carbon (a-C) films deposited with CrC interlayers of various thicknesses as the adhesive layer. A-C and CrC thin films were deposited using the unbalanced magnetron (UBM) sputtering method with graphite and chromium as the targets. CrC films as the interlayer were fabricated under a-C films, and various structural, surface, and tribological properties of a-C films deposited with various CrC interlayer thicknesses were investigated. With various CrC interlayer thicknesses under a-C films, the tribological properties of CrC/a-C films were improved; the increased film thickness exhibited a maximum high hardness of over 27.5 GPa, high elastic modulus of over 242 GPa, critical load of 31 N, residual stress of 1.85 GPa, and a smooth surface below 0.09 nm at the condition of 30-nm CrC thickness.

• Journal of Surface Science and Engineering
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• v.29 no.5
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• pp.549-555
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• 1996

Diamond Like Carbon film is amorphous film which is considered to consist of three coordinate graphite structure and tetrahedron coordinate diamond structure. Its hardness, thermal conductivity and chemical stability are nearly to one of diamond. It is well known to become semi-conductor by doping of inpurity. In this study Diamond Like Carbon film was synthesized by Microwave Plasma CVD in the gas mixture of hydrogen-methan-nitrogen and doped of nitrogen on the single-crystal silicon or silica glass. The temperature of substrate and nitrogen concentration in the gas mixture had an effect on the bonding state, structural properties and conduction mechanism. The surface morphology was observed by Scanning Electron Microscope. The strucure was analyzed by laser Raman spectrometry. The bonding state was evaluated by electron spectroscopy. Diamond Like Carbon film synthesized was amorphous carbon containing the $sp^2$ and $sp^3$ carbon cluster. The number of $sp^2$ bonding increased as nitrogen concentration increased from 0 to 40 vol% in the feed gas at 1233K substrate temperature and at $7.4\times10^3$ Pa. Increase of nitrogen concentration made Diamond Like Carbon to be amorphous and the doze of nitragen could be controlled by nitrogen concentration of feed gas.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.122-122
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• 1999

Graphite with its advantages of high thermal conductivity, low thermal expansion coefficient, and low elasticity, has been widely used as a structural material for high temperature. However, graphite can easily react with oxygen at even low temperature as 40$0^{\circ}C$, resulting in CO2 formation. In order to apply the graphite to high temperature structural material, therefore, it is necessary to improve its oxidation resistive property. Silicon Carbide (SiC) is a semiconductor material for high-temperature, radiation-resistant, and high power/high frequency electronic devices due to its excellent properties. Conventional chemical vapor deposited SiC films has also been widely used as a coating materials for structural applications because of its outstanding properties such as high thermal conductivity, high microhardness, good chemical resistant for oxidation. Therefore, SiC with similar thermal expansion coefficient as graphite is recently considered to be a g행 candidate material for protective coating operating at high temperature, corrosive, and high-wear environments. Due to large lattice mismatch (~50%), however, it was very difficult to grow thick SiC layer on graphite surface. In theis study, we have deposited thick SiC thin films on graphite substrates at temperature range of 700-85$0^{\circ}C$ using single molecular precursors by both thermal MOCVD and PEMOCVD methods for oxidation protection wear and tribological coating . Two organosilicon compounds such as diethylmethylsilane (EDMS), (Et)2SiH(CH3), and hexamethyldisilane (HMDS),(CH3)Si-Si(CH3)3, were utilized as single source precursors, and hydrogen and Ar were used as a bubbler and carrier gas. Polycrystalline cubic SiC protective layers in [110] direction were successfully grown on graphite substrates at temperature as low as 80$0^{\circ}C$ from HMDS by PEMOCVD. In the case of thermal MOCVD, on the other hand, only amorphous SiC layers were obtained with either HMDS or DMS at 85$0^{\circ}C$. We compared the difference of crystal quality and physical properties of the PEMOCVD was highly effective process in improving the characteristics of the a SiC protective layers grown by thermal MOCVD and PEMOCVD method and confirmed that PEMOCVD was highly effective process in improving the characteristics of the SiC layer properties compared to those grown by thermal MOCVD. The as-grown samples were characterized in situ with OES and RGA and ex situ with XRD, XPS, and SEM. The mechanical and oxidation-resistant properties have been checked. The optimum SiC film was obtained at 85$0^{\circ}C$ and RF power of 200W. The maximum deposition rate and microhardness are 2$mu extrm{m}$/h and 4,336kg/mm2 Hv, respectively. The hardness was strongly influenced with the stoichiometry of SiC protective layers.

• Transactions on Electrical and Electronic Materials
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• v.12 no.3
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• pp.89-92
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• 2011

Hydrogenated amorphous carbon (a-C:H) films were deposited by plasma enhanced chemical vapor deposition on silicon substrates. a-C:H thin film was irradiated to a typical He-Cd laser to study its emitting properties. The photoluminescence (PL) intensity during the irradiation achieved a maximum value when 2,000 seconds elapsed. Fourier transform infrared measurement revealed a-C:H thin film suffered transformation from a polymer-like to graphite-like phase during laser irradiation. Thermal annealing was done at various temperatures, ranging from room temperature to $400^{\circ}C$ in the atmosphere, to investigate structural changes in a-C:H film by heat generation during the emission. PL intensity of a-C:H thin film increased 1.5 times without apparent structural change, as annealing temperature increased up to $200^{\circ}C$. However, a-C:H film above $200^{\circ}C$ exhibited significant decrease of PL accompanying dehydrogenation. This led to a red shift of the PL peak.