SOLUBILITY AND DAMAGE ANNEALING OF ER IMPLANTED SINGLE-CRYSTALLINE ALPHA-AL2O3

Er implantation into c-cut sapphire (alpha-Al2O3) was studied using io n beam techniques. Er+ ions were implanted at room temperature (RT) an d liquid nitrogen (LN) temperature with an energy of 800 keV and fluen ces in the range of 10(14)-10(16) Er/cm(2). At LN temperatures doses a bove 3 x 10(14) Er/cm(2) create a continuous amorphous layer throughou t the implanted region. The epitaxial regrowth of this layer at 1500 d egrees C leaves a defect free region and is accompanied by the segrega tion of a great amount of Er to the surface, The retained Er was rando mly incorporated in the alpha-Al2O3 lattice reaching a maximum concent ration of 4 x 10(19) cm(-3). In contrast, the implantation of 2 x 10(1 6) Er/cm(2) at RT only produces a buried amorphous layer near the end of the range. The near surface region, although heavily damaged, remai ns crystalline. The buried amorphous layer shows an epitaxial recrysta llization and some residual defects remain in the region where the Er profile is located. The energy dependence of the dechanneling rate giv es an indication that these defects are dislocations. In this case the recrystallization process causes the narrowing of the Er profile with the diffusion of a small amount to the surface. Detailed angular scan s along the [0 0 0 1] and [0 2 (2) over bar 1] axes show the presence of Er precipitates aligned with the c-axis. (C) 1998 Elsevier Science B.V.