Properties of amorphous SiAlON thin films grown by RF magnetron co-sputtering

SiAlON thin films were deposited by RF magnetron co-sputtering of Al and Si targets in Ar/O2/N2 mixtures to a thickness of ~ 200 nm onto both bare and Pt-coated r-cut sapphire substrates. Films deposited at 200 °C are amorphous as determined from X-ray diffraction (XRD) and have < 1 nm RMS roughness as measured by X-ray reflectivity (XRR). In situ X-ray photoelectron spectroscopy (XPS) measurements from films grown over a wide range of SixAlyOzN100 − x − y − z stoichiometries indicate that a homogenous amorphous phase is formed over all compositional regions of the quaternary thin film phase diagram. After annealing at 1000 °C for 10 h in vacuum, the film stoichiometries remained nearly unchanged and the films retained an amorphous structure, as verified by XRD. The films lost nitrogen during air exposure at 1000 °C, leading to the formation of an amorphous aluminum silicate layer at the surface. No crystalline SiAlON phases, which have been reported for bulk SiAlON materials, were observed in films even after heating at 1500 °C for 10 days. Pin-on-disk measurements showed that SiAlON films have negligible wear up to 80 gram loads, while significant wear occurs on the sapphire pin in sliding contact, indicating that the SiAlON films have excellent wear resistance.