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Surface-wave plasma which generates a specific wave mode between the plasma and a dielectric window by microwave is superior to RF plasmas in producing relatively higher electron density at low temperature. To challenge the uniformity issue of the microwave plasma whose wavelength is shorter than the size of the industrial system, rotating field systems by imparting a phase difference of microwaves from multiple inputs over time are attracting attention. The authors investigate the feasibility of a phase-locked-loop (PLL) injected magnetron (MGT) as a highly efficient microwave source to modulate the phase difference of high-power microwaves fast and precisely. The phase-transition time of the MGT with a plasma load is estimated to be below 45 ns by theoretical analysis and experimental measurement. The results show that the phase-modulation frequency of microwaves with the PLL-injected MGT is capable of reaching up to 10 MHz.

A 2.45 GHz microwave plasma with linear antenna has been prepared for hydrophobic and wear-resistible surface coating of carbon steel. Wear-resistible properties are required for the surface protection of cutting tools and achieved by depositing a hydrogenated amorphous carbon film on steel surface through linear microwave plasma source that has TE 10- TEM waveguide. Compared to the existing RF plasma source driven by 13.56MHz, linear microwave plasma source can easily generate high density plasma and provide faster deposition rate and wider process windows. In this study, Ar/CH₄ gas mixtures are used for hydrogenated amorphous carbon film deposition. When microwave power of 1000W is applied, 40 cm long uniform Ar/CH₄ plasma could be obtained in gas pressure of 200~400 mTorr. The Vickers hardness measurement of hydrogenated amorphous carbon film on steel surface was evaluated. It was found the optimized deposition condition at Ar : CH₄=25:25 sccm, 300 mTorr with microwave power of 1000W and RF bias power of 100W. By deposition of hydrogenated amorphous carbon film, contact angle on steel surfaces increases from 43.9° to 93.2°.

In low-temperature Ar/H2 discharge used for material processing, the main factor influencing the film quality is the active species responsible for surface reactions, such as hydrogen atoms or hydrogen ions. The changes in plasma chemistry with the operating conditions affect the production of active species in the bulk plasma region. In conventional Ar/H2 discharge using continuous-wave plasma, there is not enough information to explain the correlations between the active species generation and process parameters. In particular, it is difficult to investigate the relationship between the generation of H x (x = 1, 2) ions using the ratio of Ar to hydrogen as an operating variable, and an additional control parameter is required to research the occurrence of each active species. To improve the efficiency of material processing and enhance process controllability, an inductively coupled plasma Ar/H2 pulsed-power model (source pulsing) was introduced and investigated in this study. This work provides an overview of the generation of each active species in pulsed Ar/H2 discharge and discusses the effects of the Ar/H2 gas mixture ratio, duty cycle, and pulse frequency. In addition, it presents an analysis of the principle of the Ar/H2 pulsed-plasma process for the production of active species, demonstrating that the generation densities of specific ions and neutral particles can be controlled.

In a Fire Extinguishing System (FES), it is important to maintain the design concentration of the gaseous agent in the enclosure for a specific time. An inert agent, in particular, can maintain an O2 concentration below 15% by maintaining a gaseous concentration above the threshold value for a specified time, which is called the retention time. However, the current theoretical model for retention time in the inert agent reflects only species diffusion due to differences in gravity and molecular weight but not due to temperature. Therefore, this study analyzed species diffusion with temperature using IG-541, a representative inert agent. A numerical analysis was done with the assumption of a stable flow field (no bias pressure from HVAC systems), and the discharge step was eliminated for a simplified approach. As a result, the retention time of the inert agent was sensitive to species diffusion with temperature. The diffusion flux was used to analyze the influence on the inert agent temperature according to Fick's law and the slope ω according to the interface thickness. The numerical analysis could provide a basis for a new model that takes into account temperature in the future.

A linear microwave plasma source has been prepared for hydrophobic and wear-resistible surface coating of carbon steel. Hydrophobic wear-resistible properties are essential for adhesive film cutting tools. Microwave power was coupled to plasma through TE 10 -TEM mode converter. Compared with RF capacitively couple plasmas which have long been used for hydrophobic surface treatment, microwave plasma can provide wider process windows, independent ion energy controllability and faster processing rate. In this study, Ar/CH 4 /CF 4 and their mixture was used for surface treatment. Stable and uniform 45cm-long plasma could be obtained in a pressure range of 100 ∼ 500 mTorr with microwave power of 500 W. 13.56 MHz RF power was independently applied to substrate electrode for bias voltage control. After Ar plasma treatment for surface cleaning, Ar/CH 4 and Ar/CH 4 /CF 4 plasma enhanced deposition process has been performed. CH 4 was chosen to achieve wear-resistibility and improve tribological properties by forming a-C:H diamond-like carbon layer. Additional CF 4 incorporation allowed us to enhance hydrophobicity of the surface layer. Optimized deposition condition was investigated as a function of microwave power, gas pressure, gas flow rate and bias power. The nominal deposition rate was 124Å/min at Ar:CH 4 = 25:50 sccm, 300 mTorr with microwave power of 300W. After CF 4 plasma incorporation, hydrophobicity was drastically improved. The contact angle was changed from 57 degree to 120 degree.

An atmospheric-pressure plasma jet source based on dielectric barrier discharge (DBD) was prepared for the hydrophilic surface treatment of poly(dimethylsiloxane) (PDMS). Discharge characteristics were investigated from intensified charge coupled device (ICCD) images and by optical emission spectroscopy (OES). Different optical emission profiles were observed in plasmas with argon (Ar) and helium (He) feed gases. For Ar plasma, OH and N2 related emission lines are dominant. On the other hand, relatively strong peaks of N2+ and O excited species were observed in He plasma, suggesting that a metastable He atom plays an important role in the downstream plasma region. Ar plasma was further found to be more effective than He plasma for hydrophilic surface modification. The surface reverted to being hydrophobic about 40 h after plasma irradiation.