Paper SE-TuM3
Nanostructure, Bonding, and High Temperature Oxidation of SiZrON Thin Films

Tuesday, October 19, 2010, 8:40 am, Room Cimmaron

SiZrON thin films have potential applications as hard high temperature coatings since they combine the oxidation resistance and hardness of oxides with the toughness of nitrides. In this study, a range of Si_xZr_yO_zN_1-x-y-z thin films with a nominal thickness of 200 nm were deposited onto r-cut sapphire and fused silica substrates at 200°C using reactive RF magnetron co-sputtering of Zr and Si targets in N₂/O₂/Ar gas mixtures. The films were characterized using high resolution scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) in the as-deposited state as well as after annealing treatments up to 1000°C both in air and in vacuum. Grazing incidence XRD indicates that the as-deposited are amorphous for oxygen-rich and Si-rich film stoichiometries, but nanocrystalline ZrN or ZrO₂ phases form within an amorphous matrix for N-rich and Zr-rich films. XPS shows a decrease in the Si, Zr, O, and N Auger parameters as the chemical bonding becomes more ionic with increasing O+Si content. For the different films, the N1s XPS lineshape indicates different states involving Si-N-O, Zr-N-O, and/or O-N bonding. When annealed to 1000°C in vacuum, negligible changes in stoichiometry or nanostructure are observed. However, when the films are heated to 1000°C in air, N depletion and Si enrichment at the film surface is observed, accompanied by the formation of tetragonal phase ZrO₂ nanocrystallites and changes in nanomorphology as observed by SEM. Argon ion depth profiling with XPS was used to investigate the kinetics of the high temperature oxidation process.