• 한국표면공학회지
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• 제54권6호
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• pp.348-356
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• 2021

In this study, optical diagnosis of plasma was performed for nitrogen doping in graphene using a horizontal inductively coupled plasma (ICP) system. Graphene was prepared by mechanical exfoliation and the ICP system using nitrogen gas was ignited for plasma-induced and defect-suppressed nitrogen doping. In order to derive the optimum condition for the doping, plasma power, working pressure, and treatment time were changed. Optical emission spectroscopy (OES) was used as plasma diagnosis method. The Boltzmann plot method was adopted to estimate the electron excitation temperature using obtained OES spectra. Ar ion peaks were interpreted as a reference peak. As a result, the change in the concentration of nitrogen active species and electron excitation temperature depending on process parameters were confirmed. Doping characteristics of graphene were quantitatively evaluated by comparison of intensity ratio of graphite (G)-band to 2-D band, peak position, and shape of G-band in Raman profiles. X-ray photoelectron spectroscopy also revealed the nitrogen doping in graphene.

• Nuclear Engineering and Technology
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• 제56권4호
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• pp.1145-1152
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• 2024

To realize an initial objective of the negative ion-based neutral beam injection (N-NBI) at the Comprehensive Research Facility for Fusion Technology (CRAFT) test facility, which targets an H⁰ beam power of 2 MW at an energy of 200-400 keV and a pulse duration of 100 s, it is crucial to study the cesium dynamics of the negative ion source. Here a numerical simulation program CSFC3D is developed and applied to simulate the distribution and time dynamics of cesium during short pulses. The calculations show that most of the cesium on the plasma grid (PG) area originates from the release of cesium that is accumulated within the ion source in the plasma phase. Increasing the wall temperature reduces the loss of cesium on the wall of the ion source. Furthermore, the thickness of the cesium monolayer is directly influenced by the PG temperature. Both simulated and experimental results demonstrate that maintaining the PG temperature between 180 ℃ and 200 ℃ is essential for enhancing the performance of the ion source and optimizing the cesium behavior.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.525-525
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• 2013

Low temperature plasma diagnosis is one of the big issues in laboratory scale or processing industry. One of the most powerful techniques of plasma diagnostics is the use of the scattering of electromagnetic radiation from the plasma. Electron temperature and density are important parameters for understanding the information of plasmas in the plasma processing industry. Laser scattering experiments on plasma can provide a substantial amount of information about plasma parameters such as the electron density ne, the electron temperature Te, and the neutral density nn and temperature Tn. Thomson scattering spectroscopy is used several method, in accordance with detector type. Commonly, Thomson scattering is used several notch filter to separate expanded wavelength. Since using a spectrometer with surface relief grating or notch filter, the system of the measurement will be complicated and bigger. In this study, using VPHG (Volume Phase Holographic Grating) in order to install the simple and cheap system. VPHG has the advantage of the system installation, because it can be Transmission Type. The diffraction efficiency and dispersion angle of VPHG is higher than the surface relief grating relatively. For a wavelength and bandwidth selection, Using a slit or mask to select a rejection wavelength instead of notch filter.

• 한국염색가공학회지
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• 제6권4호
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• pp.27-33
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• 1994

Wool fabrics were treated with low temperature oxygen plasma and/or protease, and examined for their mechanical and dyeing properties. By plasma-treatment the strength of wool fabric increased and higher rate of weight loss for protease treatment was obtained. When dyed by levelling type acid dye equilibrium dye uptake appeared same, but rate of dyeing increased by the plasma treatment, while, with milling type acid dye, both of them increased greatly in the order of untreatedplasma/protease-treated. It was assumed from the above results that plasma affects the surface of fiber, and enzyme attacks mainly the inner part of fiber. This was confirmed again by scanning electron microscope.

• 한국세라믹학회지
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• 제34권11호
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• pp.1121-1128
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• 1997

In this study, the Ar plasma treatment was used to improve the surface roughness of Poly-Si1-xGex thin film deposited by RTCVD. The surface roughness and the resistivity of Si1-xGex thin film were investigated with variation of Ar plasma treatment parameters (electrode distance, working pressure, time, substrate temperature and R.F power). When the Ar plasma treatment was used, the cluster size decreased by the surface etching effect due to the increasing surface collision energy of particles (ion, neutral atom) in plasma under the conditions of decreasing electrode distance and increasing pressure, time, temperature, and R. F power. Although the surface roughness value decreased by the reduction of the cluster size due to surface etching effect, however, the resistivity increased. This may be due to the surface damage caused by the increasing surface collision energy. It was concluded that the surface roughness could be improved by the Ar plasma treatment, while the resistivity was increased by the surface damage on the substrate.

• 전자공학회논문지A
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• 제31A권4호
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• pp.84-91
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• 1994

A compact electron cyclotron resonance(ECR) plasma system composed of a microwave generator and a magnet coil was fabricated. A Langmuir single probe was used to investigate the plasma characteristics of the system through I-V measurements. The performance of the compact ECR plasma system was tested for the case of silicon etching reaction with $CF_{4}/O_{2}$(30%) mixed gas. Electron density and etch rate increased to maximum values and then decreased with increasing argon gas pressure, but electron temperature changed in the opposite way. The electron density and the electron temperature of argon gas plasma were 0.85${\times}~5.5{\times}10^{10}cm^{-3}$ and 4.5~6.0 eV, respectively, in the pressure range from $3{\times}10^{4}$ to 0.05Torr. The etch rate reached a maximum value at the position of 2.5cm from the bottom of plasma cavity. Etch rate uniformity was $\pm$6% across 6cm wafer. Anisotropic index was 0.75 at 1.5${\times}10^{-4}$Torr.

• 한국표면공학회지
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• 제32권6호
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• pp.658-664
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• 1999

Helicon sources are attractive for plasma processing because they provide high plasma density in low magnetic fields. Helicon waves were excited by a Nagoya type III antenna in a magnetized plasma column. Plasma parameters were measured with a double probe, and the structure and adsorption of the helicon wave fields were determined with the probes. Argon is fed through a MFC (mass flow controller) for operation pressure of 10~110 mtorr. A 13.56 MHz r.f. power of 50~450 W is induced through the antenna. The plasma density and electron temperature are measured as functions of external magnetic field, r.f. power and pressure. The plasma density as functions of r.f. power and magnetic field at a constant pressure increased linearly, and the electron temperature did not change largely with various operation parameters and the value was around 5~7 eV.

• 멤브레인
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• 제7권4호
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• pp.183-190
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• 1997

Composite membranes were prepared by the deposition of pentafluoropyridine(PFP) or pentafluorotoluene(PFT) plasma films onto porous Celgard and nonporous poly(dimethylsiloxane) [PDMS] films. Gas permeation measurements for the composite membranes were made in the temperature range of 35$^{\circ}$C to 75 $^{\circ}$C and the solubilities in plasma polymers were measured using a Cahn Microbalance. The permeability coefficients of plasma polymers obeyed the Arrhenius relationship fairly wall. Activation energies for permeation in the plasma films increased with the size of penetrant molecules. The activation energy of plasma polymers was much lower than that of commonly used perfluoropolymers. This difference was proved to be attributable to the much lower heat of solutions of the plasma polymers compared to perfluoropolymers. The diffusion activation energies were comparable with each other.

• 한국표면공학회지
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• 제57권3호
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• pp.155-164
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• 2024

Physical properties of carbon nanomaterials are dependent on their nanostructures and they are modified by diverse synthesis methods. Among them, thermal plasma method stands out for synthesizing carbon nanomaterials by controlling chemical and physical reactions through various design and operating conditions such as plasma torch type, plasma gas composition, power capacity, raw material injection rate, quenching rate, kinds of precursors, and so on. The method enables the production of carbon nanomaterials with various nanostructures and characteristics. The high-energy integration at high-temperature region thermal plasma to the precursor is possible to completely vaporize precursors, and the vaporized materials are rapidly condensed to the nanomaterials due to the rapid quenching rate by sharp temperature gradient. The synthesized nanomaterials are averagely in several nanometers to 100 nm scale. Especially, the thermal plasma was validated to synthesize low-dimensional carbon nanomaterials, carbon nanotubes and graphene, which hold immense promise for future applications.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.77-77
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• 2016

Thin films synthesized by plasma processes have been widely applied in a variety of industrial sectors. The structure control of thin film is one of prime factor in most of these applications. It is well known that the structure of this film is closely associated with plasma parameters and species of plasma which are electrons, ions, radical and neutrals in plasma processes. However the precise control of structure by plasma process is still limited due to inherent complexity, reproducibility and control problems in practical implementation of plasma processing. Therefore the study on the fundamental physical properties that govern the plasmas becomes more crucial for molecular scale control of film structure and corresponding properties for new generation nano scale film materials development and application. The thin films are formed through nucleation and growth stages during thin film depostion. Such stages involve adsorption, surface diffusion, chemical binding and other atomic processes at surfaces. This requires identification, determination and quantification of the surface activity of the species in the plasma. Specifically, the ions and neutrals have kinetic energies ranging from ~ thermal up to tens of eV, which are generated by electron impact of the polyatomic precursor, gas phase reaction, and interactions with the substrate and reactor walls. The present work highlights these aspects for the controlled and low-temperature plasma enhanced chemical vapour disposition (PECVD) of Si-based films like crystalline Si (c-Si), Si-quantum dot, and sputtered crystalline C by the design and control of radicals, plasmas and the deposition energy. Additionally, there is growing demand on the low-temperature deposition process with low hydrogen content by PECVD. The deposition temperature can be reduced significantly by utilizing alternative plasma concepts to lower the reaction activation energy. Evolution in this area continues and has recently produced solutions by increasing the plasma excitation frequency from radio frequency to ultra high frequency (UHF) and in the range of microwave. In this sense, the necessity of dedicated experimental studies, diagnostics and computer modelling of process plasmas to quantify the effect of the unique chemistry and structure of the growing film by radical and plasma control is realized. Different low-temperature PECVD processes using RF, UHF, and RF/UHF hybrid plasmas along with magnetron sputtering plasmas are investigated using numerous diagnostics and film analysis tools. The broad outlook of this work also outlines some of the 'Grand Scientific Challenges' to which significant contributions from plasma nanoscience-related research can be foreseen.