Formation of coherent precipitates of platinum in sapphire

The surface region of sapphire was modified by implantation of Pt ions. Sin gle 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 si tes in the Al sublattice. The increase in dose makes the implanted region h ighly damaged. The amorphization is observed for doses higher than 10(16) P t+/cm(2). During vacuum annealing at 1200 degrees C, the substitutional fra ction of Pt decreases and most of the damage is recovered. Annealing of 5x1 0(16) Pt+/cm(2) implanted alpha-Al2O3 at the same temperature but in an oxi dizing atmosphere allows the complete recrystallization of the amorphous re gion and induces the formation of Pt precipitates in agreement with glancin g incidence X-ray diffraction (GIXRD) measurements. Detailed angular scans through the main axial and planar directions show that the metallic precipi tates are aligned with the c-axis of the alpha-Al2O3 structure. (C) 1999 El sevier Science B.V. All rights reserved.