Silicon doped diamond-like carbon (Si-DLC) thin films were synthesized on silicon substrates using a reactive sputtering system. A plasma composed of the decomposition of a CH4 and SiH4 gas mixture and RF magnetron sputtering of a graphite target by Ar gas was used. The Si content in the films was controlled by adjusting the α-ratio (input fraction of SiH4) ranging from 0 to 15 at.%. The Raman spectra revealed that the G peak position shifted to a lower wavenumber and the ID/IG ratio decreased with increasing Si content, indicating that Si incorporation reduced the average size of sp2-bonded clusters and promoted sp3 bond formation. It was found that the hardness increased and residual stress decreased as the Si content was increased. The changes of the structural and mechanical properties might be explained by the existence of 5 nm β-SiC crystallites embedded in an amorphous matrix.

Keywords: Si-DLC, thin films, deposition, reactive sputtering, microstructure.