Rita, E Alves, E Wahl, Ulrich Correia, JG Neves, AJ Soares, MJ Monteiro, T
Elsevier science bv
Physica b-condensed matter vol:340 pages:235-239
ZnO  single-crystals were implanted at room temperature with 150 keV Tm+ ions at a fluence of 5 x 10(15) cm(-2). Each sample was then subjected to one single 30 min air annealing at 800degreesC, 950degreesC and 1050degreesC. The Tin lattice site location and defect recovery were investigated with Rutherford Backscattering/Channeling Spectroscopy. Detailed angular scans along the  direction show that 94% of the Tm ions occupy substitutional Zn sites (S-Zn) in the as-implanted sample. All the annealing temperatures lead to a reduction of this fraction to 30%. Also, progressive damage recovery and Tm segregation to the surface were observed, being enhanced at 1050degreesC. Photoluminescence (PL) studies with above band gap excitation performed on these samples revealed no luminescence on the as-implanted state. The 800degreesC air annealing promotes the Tm3+ optical activation and a well-defined near-infrared intraionic emission is observed. For higher annealing temperatures, in spite of no change of the Tin fraction at S-Zn sites, a decrease of the Tm intraionic emission was observed. These results suggest that optical activation of Tm ions is related with the defect density in their environment. (C) 2003 Elsevier B.V. All rights reserved.