Deposition of carbon films onto metal and silicon substrates by filtered cathodic vacuum arc, plasma enhanced CVD and unbalanced magnetron sputtering

Abstract

Comparison is made between films deposited onto metal and silicon substrates with variable thickness via PECVD, hydrogen-free filtered cathodic vacuum arc (FCVA) and unbalanced magnetron sputtering (UBMS). Raman spectroscopy, nanoindentation and Kelvin probe (for work function) were used to analyse the quality, structure, surface morphology and electrical properties of the films. The Raman I d/ I g ratio ranged from 0.1 to 1.6, depending on substrate material, thickness and deposition technique. Relative work functions of FCVA and PECVD films were lower than those of UBMS films. UBMS films have, what appears to be an amorphous sp 2 carbon structure across the thickness range while PECVD and FCVA indicate an initial growth layer, up to 20 nm, that differs in sp 3-content compared to thicker films, due to the influence of the substrate. In the former, this initial layer is characteristic of a polymeric high sp 3 a-C:H film but as the film thickness increases a harder film forms. FCVA films show a small but increasing sp 3-content and growth rate as thickness increases, suggesting a lower subplantation effectiveness into the substrate compared to a-C.