Influence of high-energy Si+ ion irradiation on microstructure and mechanical properties of alumina films

Amorphous alumina films, approximately 600 nm in thickness, prepared on Si(100) substrates by RF magnetron sputtering were irradiated with 2.0 MeV Si+ ions at a dose of 1×1017 ions/cm2 and the influence on the composition, microstructure, and mechanical properties was examined by Rutherford backscattering, X-ray diffraction and nano-indentation measurements. It was found that the O/Al ratio in the films was approximately 1.5, and there was no significant alteration in this ratio after ion irradiation. However, a structural change from amorphous to the crystalline γ-alumina was observed. Hardness and elastic modulus of the irradiated film were significantly increased from approximately 11 and 181 GPa up to approximately 25 and 246 GPa, respectively.