PREPARATION OF CUBIC BORON-NITRIDE FILMS BY USE OF ELECTRICALLY CONDUCTIVE BORON-CARBIDE TARGETS

This paper deals with the successful preparation of cubic boron nitrid e (c-BN) films by use of an electrically conducting boron carbide (B4C ) target in reactive r.f. sputtering. It describes the influences of t he 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 b e reduced to <5 at.% by varying the Ar-N-2 gas mixture. With respect t o c-BN formation important parameters have been found in the ratio of target to substrate power and the negative substrate bias voltage, Alm ost single-phase c-BN films have been deposited at substrate temperatu res <300 degrees C. The films were characterized by electron probe mic roanalysis, IR spectroscopy, high resolution transmission electron mic roscopy and transmission electron diffraction. The films revealed a na nocrystalline microstructure 10-40 nm in size. Hardness as determined by nanoindentation measurements was as high as 60 GPa.