On the structure of deposited diamond-like carbon films produced by Rf (13.56MHz) CH₄ plasma

Plasma enhanced chemical vapour deposition technique is used to grow diamond-like carbon films using pure methane gas plasma. It is known that the structure of the deposited films is largely influenced by the self-bias voltage values and thereafter all the film properties are a function of the structure; this concerns hydrogen concentration and sp³/sp² hybridisation ratio in DLC films. Then monitoring DLC film properties requires the control of hydrogen concentration and hybridisation rates. This investigation is focused on the study of the structure changes upon the deposition conditions. The correlation between the structure and the deposition conditions was investigated by using various characterization techniques. Fourier Transform Infra-Red Spectroscopy (FTIR) was used to analyse the absorption of optically active hydrogen in the DLC films. The deconvolution of 2900cm^-1 absorption band allows the analysis of all different hybridisations and configurations forming the structure. The total quantity of hydrogen in the film is evaluated by Elastic Recoil Detection Analysis (ERDA). The quantification of sp² and sp³ concentrations is done from X-ray Photoelectron Spectroscopy (XPS). XPS measurements show that DLC films with high quantity of sp³ hybridisation can be obtained. The discussion and interpretation of these results leads to a better understanding of the relationship between structure and deposition conditions, which, in return, helps us in synthesizing films of desired properties.