Investigation of the optical properties of diamond-like carbon films

Hydrogenated-amorphous carbon films are deposited in a microwave ECR plasma reactor with an rf biased substrate holder using methane-argon and acetylene-argon gas mixtures. The film's optical properties are characterized versus deposition conditions including pressure (1-5 mTorr), rf induced bias (-100 to 20 volts), and argon/hydrocarbon flow ratio. The acetylene-argon discharges show that ion species formed from acetylene are more important than the argon ions, conversely, the methane-argon discharges showed that argon ions are a major ionic species in the deposition. The influence of the thickness of insulating substrates is studied and the feasibility of depositing multilayer a-C:H films with different film properties in each layer is demonstrated.