Chemical effects on the amorphization of sapphire

alpha-Al2O3 single crystals were implanted with similar doses of Pt and Hg ions at room temperature. Although the masses of the implanted species are very close, the observed defect production and annealing behaviour are quite different. In the case of Hg, a fluence of 1 x 10(15) at/cm(2) fully amorphizes the implanted region and the epitaxial regrowth occurs at low temperature (800 degrees C) with a velocity higher than 52 Angstrom/min. In the case of Pt the same fluence only produces a buried damage layer near the end of the range. The amorphous state is reached after the implantation of 1 x 10(16) at/cm(2) and the epitaxial regrowth occurs at high temperatures with a velocity of 3 Angstrom/min at 1100 degrees C. After implantation 70% of the Pt ions are in substitutional lattice sites while only 30% of the Hg occupy regular sites in a displaced octahedral position of the lattice. Hyperfine interaction measurements indicate that Hg can be associated with oxygen forming Hg-O complexes. (C) 1998 Elsevier Science B.V. All rights reserved.