Copper implantation defects in MgO observed by positron beam analysis, RBSand X-TEM

In this work, effects of copper ion implantation in MgO were studied. (1 0 0) MgO samples were implanted with 50 keV Cu ions and thermally annealed st epwise in air for 30 minutes at 550, 750, 1000, 1250 and 1350 K. After ion implantation and after each annealing step, the samples were analysed with positron beam analysis (PBA). Use was also made of Rutherford backscatterin g spectrometry/channeling (RBS-C) and cross-sectional transmission electron microscopy (X-TEM). The combination of these techniques enabled to monitor the depth resolved evolution of both created defects and the copper atom d epth distribution. PEA results show that copper implantation at a dose of 1 0(15) ions cm(-2) yields a single layer of vacancy type defects after annea ling. However a copper implantation at a dose of 10(16) ions cm(-2) clearly yields two layers of defects in the material after annealing, separated by an intermediate layer. In both layers nanocavities have been identified. R ES experimental results show that the implanted copper atoms diffuse into t he bulk material during annealing. X-TEM and channeling results show that a fter annealing, the lattice of the copper nanoprecipitates is epitaxial to the MgO host lattice. Under some circumstances, copper precipitates and sma ll voids call co-exist. Furthermore, X-TEM measurements show that the nanoc avities have rectangular shapes. (C) 2000 Elsevier Science B.V. All rights reserved.