Wahl, Ulrich × Rita, E Correia, JG Agne, T Alves, E Soares, JC #
Superlattices and Microstructures vol:39 issue:1-4 pages:229-237
The group Ib impurities Cu and Ag oil substitutional Zn sites are among possible candidates for p-type doping of ZnO. In order to explore possible lattice sites Of Cu and Ag in ZnO the radioactive impurities Cu-67 and Ag-111 were implanted at doses of 4 x 10(12) cm(-2) to 1 x 10(14) cm(-2) at 60 keV into ZnO single crystals. The emission channeling effects of beta- particles from the decay were studied by means of position-sensitive electron detectors, giving direct evidence that in the as-implanted state large fractions of Cu and Ag atoms (60%-70% for Cu and 30% for Ag) occupy almost ideal substitutional Zn sites with root mean square (rms) displacements of 0.014-0.017 mu. However, following vacuum annealing at 600 degrees C and above both Cu and Ag were found to be located increasingly on sites that are characterized by large rms displacements (0.03-0.05 run) from Zn sites. We conclude that in high-temperature treated ZnO Cu and Ag are most likely not simply replacing Zn atoms but are incorporated in complexes with other crystal defects or as clusters. (C) 2005 Elsevier Ltd. All rights reserved.