The effect of Si alloying on the thermal stability of Al_2O_3 films deposited by filtered cathodic arc

摘要

The effect of Si alloying on the phase transformation sequence and phase formation temperatures of Al_2O_3 thin films deposited by filtered cathodic arc was investigated by annealing experiments in air. By addition of Si the transformation of γ- to δ- and θ-Al_2O_3 is restrained by 100 °C. The thermal stability range of the δ- and θ-phase is also increased by ≥200 °C with respect to the unalloyed Al_2O_3 thin film and the formation of α-Al_2O_3 is restrained by 200 °C upon addition of Si. Based on the observed Si addition induced changes in phase formation, crystallite size and bonding it appears reasonable that the presence of SiO_2 at the grain boundaries impedingmass transport governs the Si induced stability enhancement of the metastable γ-/δ- and θ-Al_2O_3 phases and the restrained α-Al_2O_3 formation. The competing proposal assuming a randomsubstitution of Al by Si on the lattice sites is not consistent with the XPS data.