Oxidation of thin chromium nitride films: kinetics and morphology

Abstract

Magnetron-sputtered, 150 - 500 nm thick chromium nitride films of CrN and stoichiometry were exposed to air at 500 - . Oxide scale growth and morphology and the phase transformations during oxidation were investigated by means of Rutherford backscattering spectrometry, resonant nuclear reaction analysis, scanning force microscopy (SFM) and x-ray diffraction. A combined logarithmic and parabolic scale growth was found and interpreted as due to inwards diffusion of oxygen via grain boundaries (logarithmic) and outwards lattice diffusion of Cr (parabolic). Pt-marker experiments confirmed this interpretation. The activation energies of the two processes were determined to be Q = 60(20) and . During oxidation of a transformation into CrN was observed. A linear increase in the surface roughness and surface grain size with the oxide layer thickness was found by SFM.