EXPERIMENTAL AND THEORETICAL-STUDY OF ANOMALOUS IMPLANTATION PROFILES IN SINGLE-CRYSTAL MAGNESIUM-OXIDE

150 keV niobium implantations were performed at RT in magnesium oxide single crystals. Fluences ranged from 10(16) to 10(17) ions cm-2. The RBS and XPS techniques allowed the characterization of the implantation profiles and the chemical states of the implants. A comparison between the experimental profiles and the theoretical predictions obtained with TRIM calculations showed no agreement between the values of projected range R(p) and DELTA-R(p). A spreading in depth of the ion distribution was observed for Nb implantations. XPS measurements showed that the stable oxidation states of Nb were the 5+ and 4+ states. In order to obtain precise information on the mechanisms of such an anomalous diffusion static lattice calculations of defect parameters are performed for the Nb/MgO system. These calculations allow us to obtain precise information on the stable defects associated with the presence of the metallic impurities in MgO single crystals.