Lattice location and annealing behaviour of Pt and W implanted sapphire

Sapphire (α-Al2O3) single crystals were implanted with different doses of Pt and W ions in the range of 1 x 1014 at/cm2 to 5 x 1016 at/cm2 at room temperature. Detailed angular scans through the main axial directions show that up to 1015 at/cm2 fluences about 80% of the W and Pt ions are incorporated into substitutional or near substitutional lattice sites. Below the amorphization threshold implantation damage show a double peak structure which anneals out partially at low temperature (800oC). Amorphization of the implanted region starts for doses of the order of 1 x 1016 at/cm2. The amorphous layer regrowths epitaxially in vacuum at 1100oC, with a velocity of 3 Angstrom/min and stops when the crystalline/amorphous interface reaches the region of maximum Pt concentration. When the annealing is done at ambient atmosphere the damage recovers completely at 1100 deg. C even for doses of the order of 5 x 1016 Pt+/cm2 leading to the formation of Pt precipitates