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

摘要

Amorphous boron carbide films were depositedonto silicon substrates by a magnetron sputter-ion platingprocess in an argon plasma atmosphere (0.25 Pa) using a B_4Ctarget. The substrates were polarized with a d.c. bias voltage inthe range from 0 to -100 V. The film composition and thepresence of contaminants were determined by ion beam analysis(IBA). The nanoscale tribological properties were investigatedby atomic force microscopy (AFM). IBA revealed that theboron/carbon atomic ratio is around 4 and that oxygencontamination does not exceed 10 at. percent. The hydrogencontent is below 2 at. percent. The film density is nearly thebulk value for all biases applied to the substrate. AFMmeasurements show that the surface roughness decreases withincrease of bias from 0.85 to 0.15 nm. The friction coefficientobtained by lateral force measurements follows the same trend,decreasing with increasing bias from 0.25 to 0.1. Wearmeasurements were performed and the wear depth decreased forfilms with lower friction coefficients. A mechanism based onthe removal of a modified B_4C surface layer is proposed toexplain the wear results.