Preparation of cubic boron nitride films by use of electrically conductive boron carbide targets

Abstract

This paper deals with the successful preparation of cubic boron nitride (c-BN) films by use of an electrically conducting boron carbide (B 4C) target in reactive r.f. sputtering. It describes the influences of the most important sputter parameters. It turned out that the B:N ratio of the sputtered layers was stabilized in the order of 1 by using Ar-N 2 gas mixtures with 6% N 2. The carbon content in the films could be reduced to <5 at.% by varying the Ar-N 2 gas mixture. With respect to c-BN formation important parameters have been found in the ratio of target to substrate power and the negative substrate bias voltage. Almost single-phase c-BN films have been deposited at substrate temperatures <300 °C. The films were characterized by electron probe microanalysis, IR spectroscopy, high resolution transmission electron microscopy and transmission electron diffraction. The films revealed a nanocrystalline microstructure 10–40 nm in size. Hardness as determined by nanoindentation measurements was as high as 60 GPa.