Structural changes in ultra-high-dose self-implanted crystalline and amorphous silicon

Ultra-high-dose Si ion implantation (1×10¹⁸ cm^-2) into both amorphous and crystalline Si has been studied as a function of implantation temperature from liquid nitrogen to 250°C. The samples were analysed before and after 600°C annealing by Rutherford backscattering and channeling (RBS-C) and cross-sectional transmission electron microscopy (XTEM). The recrystallisation kinetics of the heavily bombarded amorphous Si layers were measured using time re-solved reflectivity. Results indicate that amorphous Si is extremely resistant to continued bombardment and recrystallises epitaxially to near-perfect crystalline Si independent of the implantation temperature. However, the regrowth rate does exhibit a slow down within the high dose implanted region and the temperature dependence of this effect points to some minor defect-mediated structural rearrangements. In contrast, irradiation of crystalline Si at elevated temperature leads to a complex network of defects, their precise nature depending on the dose and implantation temperature.