PAC studies of implanted $^{111}\!$Ag in single-crystalline ZnO

The local environment of implanted $^{111}\!$Ag ( t$_{1/2}$=7.45d ) in single-crystalline [0001] ZnO was evaluated by means of the perturbed angular correlation (PAC) technique. Following the 60 keV low dose ($1\!\times\!10^{13}$ cm$^{-2}$) $^{111}\!$Ag implantation, the PAC measurements were performed for the as-implanted state and following 30 min in vacuum annealing steps, at temperatures ranging from 200 ºC to 1050 ºC. The results revealed that 42% of the probes are located at defect-free S$\scriptstyle_\textrm{Zn}$ sites ($\nu\scriptstyle_{Q} \sim$ 32 MHz, $\eta=0$) in the as-implanted state and that this fraction did not significantly change with annealing. Moreover, a progressive lattice recovery in the near vicinity of the probes was observed. Different EFGs assigned to point defects were furthermore measured and a general modification of their parameters occurred after 600 ºC. The 900 ºC annealing induced the loss of 30% of the $^{111}\!$Ag atoms, 7% of which were located in heavily damaged regions.