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The electromagnetic fields and plasma parameters have been studied in an azimuthally symmetric surface wave-excited plasma (SWP) source, by using a two-dimensional numerical analysis based on the finite-difference time-domain (FDTD) approximation to Maxwell's equations self-consistently coupled with a fluid model for plasma evolution. The FDTD/fluid hybrid simulation was performed for different gas pressures in Ar and different microwave powers at 2.45 GHz, showing that the surface waves (SWs) occur along the plasma-dielectric interfaces to sustain overdense plasmas. The numerical results indicated that the electromagnetic SWs consist of two different waves, Wave-1 and Wave-2, having relatively shorter and longer wavelengths. The Wave-1 was seen to fade away with increasing pressure and increasing power, while the Wave-2 remained relatively unchanged over the range of pressure and power investigated. The numerical results revealed that the Wave-1 propagates as backward SWs whose phase velocity and group velocity point in the opposite directions. In contrast, the Wave-2 appeared to form standing waves, being ascribed to a superposition of forward SWs whose phase and group velocities point in the same direction. The fadeaway of the Wave-1 or backward SWs at increased pressures and increased powers was seen with the damping rate increasing in the axial direction, being related to the increased plasma electron densities. A comparison with the conventional FDTD simulation indicated that such fine structure of the electromagnetic fields of SWs is not observed in the FDTD simulation with spatially uniform and time-independent plasma distributions; thus, the FDTD/fluid hybrid model should be employed in simulating the electromagnetic fields and plasma parameters in SWPs with high accuracy.

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In this study, amorphous hydrogenated carbon (a-C:H) and Si-doped diamond-like carbon (Si-DLC) films were prepared using microwave sheath voltage combination plasma (MVP) deposition. The thermal stability of the a-C:H and Si-DLC films were investigated by performing an annealing test (100-700ºC) in ambient air. Furthermore, the in situ high-temperature tribological properties on the films were investigated by performing a sliding test against a Si 3 N 4 ball at high temperatures (100, 200, and 300ºC). Hardness measurements and a tribological test showed that Si-DLC has better thermal stability than a-C:H; however, Si-DLC has a higher friction coefficient and undergoes more wear than does a-C:H in the in situ high-temperature tribological test. Therefore, the failure of Si-DLC is due to adhesive wear, whereas that of a-C:H is due to abrasive wear.