Tuning optical bandgap of crystalline MgO by MeV Co ion beam induced defects

Modifying bandgap by ion implantation based defect-engineering is a widely used technique for electronic and optoelectronic device fabrications. This report studies the influence of defect on bandgap modification in MgO single-crystal by MeV Co ion implantation in the fluence range of 5 x 10(14) to 1 x 10(16) ions/cm(2). The substitutional defects, F and V type color centers have been identified and characterized from optical absorption and photoluminescence spectra. We elucidated a mechanism of the electronic transition from F centers to conduction band via F+ center and subsequent de-excitation. The F center concentration increases with ion fluences while the bandgap obtained from the Tauc plotting gradually decreases. The band structure and density of states of different defects associated with MgO after ion implantation were calculated using density functional theory to explain the experimental bandgap modifications.