Radiative transitions in irradiated MgAl2O4 spinel crystal

Radiative transitions in MgAl 2 O 4 spinel single crystal were investigated after irradiation with He + ions of fluence ∼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 ∼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 • ∗ → V O • (3 eV) and V O • ∗ → Mg Al × (5 eV), which involve respectively energy and energy-electron transfer. Participation of the doubly-ionized oxygen vacancy V O •• in the energy/electron transfer is suggested. The obtained data enabled a generalised scheme of electronic transitions in MgAl 2 O 4 spinel in presence of intrinsic defects. • Low-temperature photoluminescence (PL) of MgAl 2 O 4 spinel crystal was analyzed. • Single-ionized oxygen vacancy (F + ) is common excited state of PL at 5 and 3 eV. • PL of irradiated MgAl 2 O 4 involves defect clusters containing oxygen vacancies. • Scheme of radiative transitions in MgAl 2 O 4 with intrinsic defects is proposed.