Formation of coherent precipitates of platinum in sapphire

The surface region of sapphire was modified by implantation of Pt ions. Single crystalline α-Al2O3 samples were implanted at room temperature with 160 keV Pt ions to fluences from 1x1014 to 5x1016 Pt+/cm2. For doses up to 1015 Pt+/cm2, 80% of the implanted ions occupy substitutional sites in the Al sublattice. The increase in dose makes the implanted region highly damaged. The amorphization is observed for doses higher than 1016 Pt+/cm2. During vacuum annealing at 1200 deg. C, the substitutional fraction of Pt decreases and most of the damage is recovered. Annealing of 5x1016 Pt+/cm2 implanted α-Al2O3 at the same temperature but in an oxidizing atmosphere allows the complete recrystallization of the amorphous region and induces the formation of Pt precipitates in agreement with glancing incidence X-ray diffraction (GIXRD) measurements. Detailed angular scans through the main axial and planar directions show that the metallic precipitates are aligned with the c-axis of the α-Al2O3 structure