Oxidation of Ni-toughened nc-TiN/a-SiNx nanocomposite thin films

Abstract

Oxidation behavior of Ni-toughened reactively sputtered composite thin films of nanocrystalline TiN and amorphous SiNx [denoted as nc-TiN/a-SiNx(Ni)] was explored to understand the oxidation mechanism. The films were deposited on silicon substrate using a magnetron sputtering technique. Oxidation was carried out from 450 °C up to 1000 °C. The nature of the oxidation was determined using x-ray photoelectron spectroscopy. The microstructure of the oxidized films was studied using grazing incidence x-ray diffraction. The topography was characterized using atomic force microscopy. It was determined that the oxidation of the nc-TiN/a-SiNx(Ni) thin film proceeds primarily through a diffusion process, in which nickel atoms diffuse outward and oxygen ions inward. The oxidation takes place by progressive replacement of nitrogen with diffused oxygen. Five regions were identified in the oxidized layer from surface into the film. For films doped with 2.1 at.% Ni, a threshold temperature of 850 °C was determined, below which, excellent oxidation resistance prevails but above which, oxidation takes place at exponential rate, accompanied by abrupt increase of surface roughness.