Defect production in ion-implanted yttria-stabilized zirconia investigated by positron depth profiling

The presence and evolution of free-volume defects induced during ion-implantation in solids can be a critical issue in micro- and nano-technology processes. Using a slow positron beam and measuring the energy-line Doppler broadening (DB) of the annihilation radiation, sub-surface investigations were carried out on single crystals of yttria-fully stabilized zirconia (Y-FSZ), following implantation of 210keV oxygen-ions at fluences ranging from 1.0 X 10(13) to 2.5 x 10(16) cm(-2). Depth profiles of the DB-lineshape S reveal a defect peak at 60 % of the oxygen-ion projected range R, i.e., closer to the surface than the vacancy distribution derived from Monte-Carlo calculations. The S-dependence on the fluence exhibits three defect-production stages already identified after implantation with noble gas ions. The intermediate stage (0.1-1 displacements per atom (dpa)) displays a trapping saturation plateau, which rises with increasing ion mass, suggesting a specific critical size for the relevant dominant defect. A slight drop in defect concentration that follows indicates that defects of the last stage (above 2 dpa), are formed at the expense of former ones. No particular effect due to the self-ion is found. (C) 2004 Elsevier B.V. All rights reserved.