• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.320-320
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• 2016

Nanocrystalline Carbon thin films have numerous applications in different areas such as mechanical, biotechnology and optoelectronic devices due to attractive properties like high excellent hardness, low friction coefficient, good chemical inertness, low surface roughness, non-toxic and biocompatibility. In this work, we studied the comparison of pure DC power and pulsed DC power in plasma sputtering process of carbon thin films synthesis. Using a close field unbalanced magnetron sputtering system, films were deposited on glass and Si wafer substrates by varying the power density and pulsed DC frequency variations. The plasma characteristics has been studied using the I-V discharge characteristics and optical emission spectroscopy. The films properties were studied using Raman spectroscopy, Hall effect measurement, contact angle measurement. Through the Raman results, ID/IG ratio was found to be increased by increasing either of DC power density and pulsed DC frequency. Film deposition rate, measured by Alpha step measurement, increased with increasing DC power density and decreased with pulsed DC frequency. The electrical resistivity results show that the resistivity increased with increasing DC power density and pulsed DC frequency. The film surface energy was estimated using the calculated values of contact angle of DI water and di-iodo-methane. Our results exhibit a tailoring of surface energies from 52.69 to $55.42mJ/m^2$ by controlling the plasma parameters.

• Journal of the Korean Society for Heat Treatment
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• v.13 no.3
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• pp.143-150
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• 2000

Ferritic plasma nitrocarburising was performed on pure iron using a modified DC plasma unit. This investigation was carried out with various gas compositions which consisted of nitrogen, hydrogen and carbon monoxide gases, and various gas pressures for 3 hours at $570^{\circ}C$. After treatment, the different cooling rates(slow cooling and fast cooling) were used to investigate its effect on the structure of the compound layer. The ${\varepsilon}$ phase occupied the outer part of the compound layer and ${\gamma}^{\prime}$ phase existed between the ${\varepsilon}$ phase and the diffusion zone. The gas composition of the atmosphere influenced the constitution of the compound layer produced, i.e. high nitrogen contents were essential for the production of ${\varepsilon}$ phase compound layer. It was found that with increasing carbon content in the gas mixture the compound layer thickness increased up to 10%. In the gas pressure around 3 mbar, the compound layer characteristics were slightly effected by gas pressure. However, in the low gas pressure and high gas pressure, the compound layer characteristics were significantly changed. The constitution of the compound layer was altered by varying the cooling rate. A large amount of ${\gamma}^{\prime}$ phase was transformed from the ${\varepsilon}$ phase during slow cooling.

• Applied Chemistry for Engineering
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• v.19 no.6
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• pp.640-644
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• 2008

Lubricating oil on aluminium surfaces was cleaned by a low temperature plasma process. Oxygen plasma mixed with argon was used, and process parameters were the mixing ratio of argon in oxygen, discharge power, and negative DC potential. The aluminium surfaces were analyzed with FTIR and EDX after the cleaning. It was found that almost all of the oil was eliminated in 20 min. if the oil was pure. Elimination efficiency was highly dependent on operational conditions of the process. The highest efficiency was obtained when treated at 300 W with oxygen plasma mixed with 30% argon applying negative potential more than -500 V on the aluminium surfaces. However, efficiency higher that 60% cannot be obtained at any condition if the oil contained inorganic materials.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.950-952
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• 1998

DC Arc Plasma was applied in order to convert of hydrocabon fuels (Methane) to hydrogen, which has higher available energy. Plasma can generate very high temperatures with a high degree of control, using electricity. Plasma can be used to produce the pure hydrogen fuel, and has rapid response time. In addition, the use of plasma could provide for a greater variety of operating modes including the posibility of virtual elimination of $CO_2$ production by pyrolytic operation and could obtain byproduct (Carbonblack).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.7
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• pp.641-646
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• 2003

The dielectric carbon nitride thin films were deposited onto Si(100) substrate using a pulsed laser ablation of pure graphite target combined with a high voltage discharge plasma in the presence of a N$_2$ reactive gas. We calculated dielectric constant, $\varepsilon$$\_$s/, with a capacitance Schering bridge method. We investigated the influence of the laser ablation of graphite target and DC high voltage source for the plasma. The properties of the deposited carbon nitride thin films were influenced by the high voltage source during the film growth. Deposition rate of carbon nitride films were increased drastically with the increase of high voltage source. Infrared absorption clearly shows the existence of C=N bonds and C=N bonds. The carbon nitride thin films were observed crystalline phase confirmed by x-ray diffraction data.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.208-211
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• 2003

The dielectric carbon nitride thin films were deposited onto Si(100) using a pulsed laser ablation of pure graphite target combined with a high voltage discharge plasma in nitrogen gas atmosphere. We can be calculated dielectric constant, ${\varepsilon}_s$, with a capacitance Sobering bridge method. We reported to investigate the influence of the laser ablation of graphite target and DC high voltage source for the plasma. The properties of the deposited carbon nitride thin films were influenced by the high voltage source during the film growth. Deposition rate of carbon nitride films were found to increase drastically with the increase of high voltage source. Infrared absorption clearly shows the existence of C=N bonds and $C{\equiv}N$ bonds. The carbon nitride thin films were observed crystalline phase, as confirmed by x-ray diffraction data.

• Progress in Superconductivity and Cryogenics
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• v.21 no.2
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• pp.36-39
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• 2019

Effects of the spherically shaped Ge and the rod-like carbon-coated Ge on the superconducting properties of $MgB_2$ were investigated. Pure Ge and carbon-coated Ge nano-powders were synthesized under the different amount of $CH_4$ (0 to 5 kPa) by using DC thermal plasma method. When the $CH_4$ was added ~100 nm sized Ge with a spherical shape changed to rod-like morphology with a diameter of ~30-70 nm and a length of ~400-500 nm. Also it was confirmed that thin carbon layers of a few nanometers were formed along the rod length and the agglomerated carbons were found on the edges of rods. Pure spherical Ge and Ge/C rods were mixed and milled with Mg & B precursor to form the doped $MgB_2$ bulk samples by the solid-state reaction method. Almost no change of $T_c$ was noticed for the pure Ge-added $MgB_2$, whereas $T_c$ was found to decrease with the Ge/C-added $MgB_2$ samples. It was found that the pure spherical Ge showed to have a negative effect on the flux pinning of $MgB_2$. However, Ge/C rods can enhance the flux pinning property of $J_c$ due to the coated carbon on Ge rods.

• KIEE International Transactions on Electrophysics and Applications
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• v.4C no.4
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• pp.185-189
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• 2004

The temporal variation of a secondary electron emission coefficient (${\gamma}$ coefficient) of hydrogenated amorphous silicon (a-Si:H) was investigated in a dc silane plasma. Estimated ${\gamma}$ coefficients have a value of 2.73 ${\times}$ 10$^{-2}$ on the pure aluminum electrode and 1.5 ${\times}$ 10$^{-3}$ after 2 hours deposition of -Si:H thin films on a cathode. It showed an abrupt decrease for about 30 minutes before saturation. The variation of the ${\gamma}$ coefficient was estimated as a function of the thin film thickness, and the film thickness was about 80 nm after 30 minutes deposition time. These results are compared with the results of a computer simulation for ion penetration into a cathode.

• Journal of the Korean Society for Heat Treatment
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• v.13 no.5
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• pp.318-323
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• 2000

The planarization of rough polycrystalline diamond films synthesized by DC arc discharge plasma jet CVD (chemical vapor deposition) was attempted using KrF excimer laser pulses. The effects of laser incidence angle and reaction gases (ozone and oxygen) on etching rate of diamond were studied. The temperature change of diamond and graphite with different laser fluences was calculated by computer simulation to explain the etching behavior of diamond films. The threshold energy density from the experiment for etching of pure crystalline diamond was about $1.7J/cm^2$ and fairly matched the simulation value. Preferential etching of a particular crystallographic plane was observed through scanning electron microscopy. The etching rate of diamond with ozone was lower than that with oxygen. When the angle of incidence was $80^{\circ}$ to the diamond surface normal, the peak-to-valley surface roughness was Significantly reduced from $20{\mu}m$ to $0.5{\mu}m$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.8
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• pp.622-628
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• 2001

We developed 1- and 2-dimensional fluid model for the analysis of a capacitively coupled Ar RF(Radio Frequency) glow discharge. This discharge is in pure Ar gas at the pressure 100[mTorr], frequency 13.56[MHz] and voltage amplitude 120[V}. This model is based on the equations of continuity and electron energy conservation coupled with Poison equation. 2-dimensional model is simulated on the condition of GEC(Gaseous Electronic Conference cell). The geometry of the discharge chamber and the electrodes used in the model is cylindrically simmetric; tow cylinders for the electrodes are surrounded by the grounded chamber. It is shown that 1-dimensional model is very useful on the understanding of RF glow discharge property and of the movement of charged particles. 2-dimensional model predicts off-axis maximum structure as in the experiments and has the results in qualitatively and quantitatively good agreement with the experiments. Effects of dc self-bias voltage, guard ring and reactor geometry is discussed.