Effect of aluminium ion implantation on the oxidation resistance of DC magnetron sputter-deposited TiB2 thin films

This paper presents a novel approach to providing high-temperature oxidation protection for titanium diboride thin films via aluminium ion implantation. Through ion beam modification, it was anticipated that metastable phases, not otherwise observed in stoichiometric TiB2, would form, giving rise to a stable oxidation barrier layer upon oxidation. Films, deposited onto single-crystal Si (1 0 0) substrates, were subjected to metal vapour vacuum arc aluminium ion implantation to doses of between 1×1016 and 3×1017 ions/cm2 using extraction voltages of up to 35 kV, vacuum annealed at 1100 °C, then oxidised in air at 650 °C for durations between 1 and 60 min. Analysis was performed using Rutherford backscattering spectroscopy, heavy ion elastic recoil detection analysis, X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy. Aluminium ion implantation resulted in the formation of various Ti–Al and Al–B phases. Upon oxidation, the preferential oxidation of aluminium was observed, giving rise to a protective Al2O3 barrier layer. Aluminium ion implantation was thus observed to reduce the oxidation rate of titanium diboride thin films.