  Defects creation and annihilation is a fundamental concept in device
fabrication. This report studies the optical bandgap modification in MgO by MeV
Ni ion irradiation-induced defect states between valance and conduction band.
Ion implantation on MgO single crystal produces substitutional defect states
along with F (anionic vacancy center), $F_2$, other oxygen vacancy center and V
(cationic vacancy center) centers confirmed from absorption and
photoluminescence spectra that can be applied as filament in valance charge
memory based resistive random access memories. The variation of optical bandgap
with Ni ion fluences is ascertained by modifying the electronic band structure.
Density Functional Theory (DFT) calculation assists in understanding the
evolution of electronic band structure for vacancies and substitutional defects
consisting of MgO structures.
