Charge states and lattice sites of dilute implanted Sn in ZnO

The common charge states of Sn are 2+ and 4+. While charge neutrality considerations favour 2+ to be the natural charge state of Sn in ZnO, there are several reports suggesting the 4+ state instead. In order to investigate the charge states, lattice sites, and the effect of the ion implantation process of dilute Sn atoms in ZnO, we have performed Sn-119 emission Mossbauer spectroscopy on ZnO single crystal samples following ion implantation of radioactive In-119 (T-1/2 = 2.4 min) at temperatures between 96 K and 762 K. Complementary perturbed angular correlation measurements on Cd-111m implanted ZnO were also conducted. Our results show that the 2+ state is the natural charge state for Sn in defect free ZnO and that the 4+ charge state is stabilized by acceptor defects created in the implantation process.