Plasma-assisted CVD of hydrogenated diamond-like carbon films by low-pressure dielectric barrier discharges

Hydrogenated diamond-like carbon (DLC) films have been deposited on silicon substrates from dielectric barrier discharge (DBD) plasmas of CH4 at room temperature under a pressure of 0.4-4.0 Torr. The effects of discharge gas pressure (P), the applied peak voltage, and the distance of the discharge gas spacing (d) on the film quality have been systematically investigated. The film hardness is mainly dependent on the Pd value and applied peak voltage. The best films of phi-40-70 mm with Knoop hardness up to 20 GPa can be deposited at 30 kV peak voltage with a Pd value of about 2 Torr mm. The deposited films were characterized by SEM, Raman, and FTIR spectroscopy. These analyses show that the deposited films are homogeneous hydrogenated amorphous carbon films with very smooth surfaces containing significant amounts of sp3 C-C bonding. The high-voltage and current waveform measurements of the discharge indicate that the low-pressure DBD consists of uniform (along the whole electrode) glow-like single breakdowns with half-widths of several microseconds. The DBD-induced deposition technique used in this work has many advantages, including the simplicity of the experimental set-up, large area deposition of DLC films, and a lower consumption of feed gas and electric power. (Author)