XPS investigations of thick, oxygen-containing cubic boron nitride coatings

Cubic boron nitride (c-BN) coatings produced by PVD and PECVD techniques usually exhibit very high compressive stresses and poor adhesion due to intense ion bombardments of the growing surface that are mandatory during the formation of the cubic phase Our previous investigations indicate however that a controlled addition of oxygen during film deposition can lead to a drastic reduction of the detrimental stress yet having minor effect on the cubic phase content in the resulting low-stress oxygen-containing c-BN O coatings (as already confirmed by various analytical methods like X-ray diffraction (XRD) high-resolution transmission electron microscopy (HRTEM) and electron diffraction and Fourier transform infra-red spectroscopy (FTIR)) This stress-reduction technique makes possible the deposition of well-adhered superhard c-BN O layer about 2 mu m thick through magnetron sputtering on top of an adhesion-promoting base layer and via a compositional-graded nucleation process In the present paper we report on the atomic bonding structure relating in particular to the incorporated oxygen within such a thick c-BN O coating using X-ray photoelectron spectroscopy (XPS) The c-BN O top layer was found to consist of about 498 at% boron 42 2 at% nitrogen 55 at% oxygen as well as small amounts of carbon (1 4 at%) and argon (11 at%) Because of the low oxygen concentration it was difficult to categorize the bonding state of oxygen according to the XPS spectra of B 1s and N 1s elemental lines However the detailed results in terms of the O is spectrum strongly indicated that the lattice nitrogen of c-BN was partially replaced by the added oxygen (C) 2010 Elsevier Masson SAS All rights reserved