Cubic boron nitride films prepared by reactive r.f. - and d.c. sputtering from different boron containing targets

Cubic boron nitride (c-BN) films have been deposited by reactive r.f. sputtering in Ar-N2 mixtures using both, insulating hexagonal boron nitride (h-BN) and electrically conducting boron carbide (B4C) targets. The relative nitrogen-flow in the sputter gas was varied between 0 and 100%. The substrate electrode was operated either with a r.f.- or d.c. power supply. As a measure for the c-BN content the ratio of the infrared absorption bands near 1100cm(exp-1) (c-BN) and 1400cm(exp-1) (h-BN) was used. A simple approximation allows to estimate the real content of the cubic phase from these ratios. For the h-BN target, maximum values of the c-BN content occurred in the range between 1 and 10% N2. For the B4C target, more than 10% N2 was needed to obtain c-BN containing films. For both target materials the growth of the cubic phase is correlated to a B/N-ratio near to 1. Many films with high c-BN contents tended to peel off from the substrate. A well adhering film exhibited a very high hardn ess of greater than 60GPa measured with a nanoindentor set-up. First experiments using a d.c. magnetron sputter apparatus with a B4C target revealed, that c-BN can also be prepared by d.c. sputtering.