Radiative transitions in irradiated MgAl2O4 spinel crystal

Radiative transitions in MgAl2O4 spinel single crystal were investigated after irradiation with He+ ions of fluence similar to 10(17) particles/cm(2). Photoluminescence (PL), PL excitation spectra and PL decay curves were measured at cryogenic temperatures of 8 K. It is shown that PL decay kinetics of 5 eV (250 nm) and 3 eV (420 nm) bands are similar because of the common excited state. Furthermore, after irradiation PL band at similar to 5 eV preserved characteristic behaviour of the donor-acceptor pair transitions. The PL channels involve electronic transitions of antisite defects, Mg-Al (shallow acceptor) and Al-Mg (shallow donor), and oxygen vacancy V-O (deep donor), while Al-Mg served an intermediate of the electronic excitation channel. The intense emissions were assigned to V-O(center dot)& lowast; -> V-O(center dot) (3 eV) and V-O(center dot)& lowast; -> Mg-Al(x) (5 eV), which involve respectively energy and energy-electron transfer. Participation of the doubly-ionized oxygen vacancy V-O(center dot center dot) in the energy/electron transfer is suggested. The obtained data enabled a generalised scheme of electronic transitions in MgAl2O4 spinel in presence of intrinsic defects.