The penetration into blind holes of diamond-like carbon films produced by r.f. plasma-assisted CVD

Diamond-like carbon films were deposited, using an r.f. plasma-assisted chemical vapour deposition process, inside tubes of different diameters rolled from stainless steel sheet. The coating thickness and microstructure, determined by scanning electron microscopy, were analysed as a function of tube depth and diameter. Although film penetration into the tubes is, as expected, influenced by the deposition system pressure, the results also suggest that the coating thickness profile depends on the distribution of ions in the depositing species. Thicker films can be grown at greater depths in smaller diameter tubes and we believe that this can be attributed to cathode sheath distortion effects, the sheath appearing to behave as a divergent lens acting on the flow of ions inside the tubes.