Numerical Analysis of Fundamental Properties in Sub-atmospheric Pressure He/CH₄ Pulsed Plasmas for Hard Coating of Diamond-Like Carbon Thin Films

Diamond-Like Carbon (DLC) films have various properties such as high hardness, low-friction coefficient, and gas barrier properties, and have been used in industrial and medical fields. In recent years, the demand for deposition on materials such as polymer materials has increased, and the technology for deposition in low-temperature environments has strongly been desired. One of the deposition techniques at low-temperatures is the plasma-enhanced chemical vapor deposition (PECVD) method. Conventional PECVD has been used in low-pressure and low-density plasmas, which results in low-deposition rate of DLC films and requires vacuum systems. Thus, a high-rate deposition technique without the use of vacuum systems have been highly required.

In this study, in order to examine the deposition technique of hard coating DLC thin films at sub-atmospheric pressure condition, we newly developed a spatially one-dimensional fluid model of hydrocarbon (He/CH₄) plasmas at sub-atmospheric pressure condition, and then discussed the influence of the applied voltage waveforms (i.e. square- and RF-modulated pulsed voltage waveforms) on the plasma characteristics.