Formation of coherent precipitates of platinum in sapphire

The surface region of sapphire was modified by implantation of Pt ions. Single crystalline alpha-Al2O3 samples were implanted at room temperature with 160 keV Pt ions to fluences from 1x10(14) to 5x10(16) Pt+/cm(2). For doses up to 10(15) Pt+/cm(2), 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 10(16) Pt+/cm(2). During vacuum annealing at 1200 degrees C, the substitutional fraction of Pt decreases and most of the damage is recovered. Annealing of 5x10(16) Pt+/cm(2) implanted alpha-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 alpha-Al2O3 structure. (C) 1999 Elsevier Science B.V. All rights reserved.