Effect of oxygen vacancy defects on electronic and optical properties of MgO monolayers: First principles study

Abstract

The optoelectronic properties induced by oxygen vacancy defects in MgO (111) monolayers have been studied using hybrid level of DFT method. HSE calculations show significant reduction in electronic band gap of MgO monolayer as a result of introduction of oxygen vacancies. The pristine monolayer has a wide band gap (4.84 eV, indirect) semiconducting behaviour, which changes to 2.97 eV (indirect) and 2.28 eV (direct) with increment in oxygen vacancy defect concentrations of 6.25 % and 12.5 %, respectively. Consequently, presence of oxygen vacancies leads to energy red shift of the observed optical phenomena with reference to the pristine monolayer. Most importantly, the di-vacancy system with two consecutive vacancy sites displays the strongest optical absorption and also becomes optically responsive over the spectral range from visible to ultraviolet region in the electromagnetic spectrum. Thus creation of oxygen vacancies in MgO monolayers may be a fruitful technique for achieving a suitable solar energy material.