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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°.

RF glow discharges are widely used in deposition, etching and surface treatments for semiconductor materials. Especially, roll-to-roll processing is necessary for flexible display or thin film solar cell modules. For a roll-to-roll thin film deposition processing, it is necessary to use cylindrical grounded electrode. The effects of electrode shapes on the plasma properties of capacitively coupled rf argon discharge at 13.56 MHz are investigated using self-consistent two-dimensional fluid simulation. The simulation model includes blocking capacitor and external circuit effects. Comprehensive analysis has been made in terms of time-varying current–voltage characteristic, spatial distributions of plasma density and ion current density on the substrate. The effects of applied voltage ( V f = 200 ∼ 800 [ V ] ) and gas pressure ( p = 0.5 ∼ 2 Torr ) on the plasma properties are also investigated. We found that flat electrode has a little bit higher impedance than that of cylindrical ground electrode. However the difference between the two configurations is less than 5% therefore we may conclude that the shape of grounded electrode does not significantly affect current–voltage characteristics of the discharge system. For roll-to-roll reactor version, displacement current come from dielectric layer between electrodes reaches more than 75% of total displacement current. Large displacement current results in degradation of power factor and matching circuit efficiency. For the cylindrical electrode, increasing electrode gap length along lateral direction makes that the location of peak electron density moves toward center of the reactor. The effect of the cylindrical electrode on the plasma spatial structure is reflected in the ion current density at substrate (dielectric layer) on grounded electrode. At low voltage and low power condition, about 90% of input power is consumed for electron heating. The efficiency decreases with increasing power and decreasing pressure as a consequence of increasing power to drive ion current. Electron heating efficiency decreased with pressure. The increase of pressure mainly reduces the diffusive component of the loss rate for both charged and neutral species.

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.

We have studied the thermal stability of optical film composed of transparent acrylic resin and the diimmonium dye, which is capable of absorbing intense near infrared (NIR) light from Plasma Display Panels (PDPs). After thermal aging, the color of optical film was changed and the efficiency of NIR absorption was decreased due to the deterioration of the dye. These phenomena were found to be sensitive to variations in characteristics of polymers and dyes. First of all, it was determined when the polymer resin possessed hydroxyl or carboxylic functional groups, although dyes's durability was slightly improved for the film with higher Tg polymer. These observations imply that the destructive mechanism of dye molecules is related to the effect of dye mobility and unpredictable chemical reactions between the dye and the reactive group of polymer. Additionally, we investigated the effect of solvent polarity as well as dye's rigidity on the thermal stability of the film in order to support these results.