Plasma enhanced chemical vapor deposition of a-C:H films in CH4–CO2 plasma: Gas composition and substrate biasing effects on the film structure and growth process

Diamond-like quality films have been deposited by low pressure Radio Frequency-Plasma Enhanced Chemical Vapor Deposition using the non-conventional CH4–CO2 mixture as gas precursor, associated with an innovative bipolar pulsed biasing technology. A comprehensive study was performed in search for the best precursors composition and process parameters together with a detailed chemical, structural and mechanical characterization of the films. We gained experimental evidences on the key role performed by a bipolar pulsed bias in creating more energetic conditions in the plasma, allowing obtaining at lower voltages material properties comparable to or even better than those achieved with higher biases but applied in the traditional continuous mode. This is achieved especially when combining such a biasing technology with plasmas containing oxygen bearing species, which provide both positively and negatively charged ions in the gas phase