Significant stress reduction of cBN layers upon ion irradiation at elevated temperatures

Superhard cubic boron nitride (cBN) thin films can be synthesized nowadays by a variety of PVD and PECVD techniques. Their applications are however still impeded by extremely high film stresses, typically above 20 GPa, resulting from a severe ion bombardment of the growing surface being obligatory for the formation of the cubic phase. This stress was shown to be partly released by an addition of oxygen during film deposition, with deposited films containing approx. 5 at.% of oxygen embedded into the cubic lattice. In this study, further impacts on the stress of such oxygen-incorporated cBN films (cBN:O) are studied by means of post-deposition high-energy implantation of oxygen-, neon-, and krypton-ions, respectively. It is shown, in particular, that the irradiation by krypton ions at 600 K temperature can produce a significant stress reduction of cBN:O from 10 GPa down to 4 GPa, without inducing observable transformation of existing cubic structure into the hexagonal phase.