Lattice site and diffusion of ion-implanted Li in as-grown and Se-rich ZnSe

The implantation sites and diffusion of Li in as-grown and Se-rich ZnSe has been studied with emission channeling measurements on the alpha-particles emitted in the decay of radioactive Li-8 probes implanted in single-crystal samples. At implantation temperatures below 180 K the Li atoms are immobil e at tetrahedral interstitial sites, but a site change sets in at 200 K, an d above 250 K the Li atoms occupy mainly substitutional sites. In Se-rich Z nSe the interstitial Li fraction (f(T)) shows partial recovery between 260 and 360 K, a phenomenon which may be attributed to Li trapping at interstit ial Se. Implantation dose, however, has a strong influence on the observed channeling and blocking patterns. Maximum f(T) is achieved at T greater tha n or equal to 400 K where the fraction at interstitial sites is an order of magnitude lower. At higher temperatures ( approximate to 550 K) the Li ato ms dissociate from their substitutional sites and diffuse to the surface in the Se-rich sample and to extended defects in the implantation region in t he as-grown sample. (C) 1999 Elsevier Science B.V. All rights reserved.