Boron carbide films deposited by a magnetron sputter–ion plating process: film composition and tribological properties

Abstract

Abstract Amorphous boron carbide films were deposited onto silicon substrates by a magnetron sputter–ion plating process in an argon plasma atmosphere (0.25 Pa) using a B4C target. The substrates were polarized with a d.c. bias voltage in the range from 0 to −100 V. The film composition and the presence of contaminants were determined by ion beam analysis (IBA). The nanoscale tribological properties were investigated by atomic force microscopy (AFM). IBA revealed that the boron/carbon atomic ratio is around 4 and that oxygen contamination does not exceed 10 at.%. The hydrogen content is below 2 at.%. The film density is nearly the bulk value for all biases applied to the substrate. AFM measurements show that the surface roughness decreases with increase of bias from 0.85 to 0.15 nm. The friction coefficient obtained by lateral force measurements follows the same trend, decreasing with increasing bias from 0.25 to 0.1. Wear measurements were performed and the wear depth decreased for films with lower friction coefficients. A mechanism based on the removal of a modified B4C surface layer is proposed to explain the wear results.