Constitution of thick oxygen-containing cubic boron nitride films

A novel method based on reactive magnetron sputtering and specifically devoted for the deposition of thick, adherent cubic boron nitride (c-BN) coatings on silicon substrates was developed. Through controlled incorporation of a small amount of oxygen into the deposition process, the ultrahigh compressive stress usually appearing in c-BN was effectively reduced down to − 3 GPa, whereas the c-BN content was nearly unaffected. This allowed consequently 2 μm thick c-BN to be grown on top of a coating system initiated with a boron-rich base layer followed by a nucleation layer with gradient chemical composition.The chemical composition of the coatings was analyzed by Auger electron spectroscopy (AES) and depth profiling. An almost stoichiometric composition including about 5 at.% oxygen was observed. By means of Fourier transform infrared spectroscopy (FTIR) and glancing-angle X-ray diffraction (XRD), the binding states, the crystallographic structure as well as lattice parameters of the coatings were confidently identified. The coating structure was shown to be dominated by the sp3-coordinated cubic phase, giving rise to super high hardness of about 60 GPa.