ODMR study of ZnO single crystals containing iron impurity ions

Optically detected magnetic resonance (ODMR) was studied in ZnO single crystals containing iron impurity ions. ODMR spectra of the ground state of isolated Fe3+ on the Zn2+ lattice sites were obtained by monitoring the intensity of the intra-centre Fe3+ luminescence together with the ODMR signals of shallow donors. The latter observation suggests that the Fe3+ luminescence may actually be excited due to energy transfer from the recombining donor-acceptor pairs to the impurity ions. This conclusion is supported by the presence of Fe3+ emission in the afterglow spectra recorded after switching off band-to band excitation light.