Characterization of DLC:Si films by the gas effusion technique

In this work an investigation of hard DLC:Si films by the gas effusion technique is presented. Effusion of hydrogen, methane and higher hydrocarbons was studied for films with silicon contents of up to 40 at%. Three major contributions to the effusion spectra could be identified: (i) a desorption-limited mechanism from the internal surfaces of a network of voids which could be observed even for large hydrocarbon molecules, indicating that low silicon content material possesses a porous structure; (ii) a sharp peak related to the abrupt graphitization of the films which dominates the spectra for hydrogen and methane effusion in the low concentration range and is gradually shifted to high temperatures as the silicon content is increased; and (iii) a diffusion-limited mechanism that appears for high silicon content films, suggesting that the films undergo a transition from porous to a relatively compact structure.