Lattice Sites of Li in Si and Ge

Abstract

The lattice sites of ion implanted Li-8 in Si and Ge were studied using the alpha-emission channeling technique. In both materials tetrahedral interstitial sites were found to be the major occupied lattice sites following room temperature implantation (60-80% in Si and 40-60% in Gel. Depending on the doping character of the sample, up to 55% of Li was found on bond-center sites in Si after implantations between 425 K and 475 K and up to 40% in Ge for implantations between 325 K and 400 K at higher temperatures Li occupied increasingly random lattice sites. The lattice site changes from tetrahedral to bond-center sites are attributed to the onset of interstitial Li diffusion and its capture by additional defects, which are likely to be vacancy-type defects from the implantation process. The trapping of Li at these defects inhibits its long-range diffusion.