Site dependent strategy for B/C/N homo and heteroatom co-doping in governing the optoelectronic behavior of MgO monolayers

Abstract

Density functional theory calculations are carried out to investigate the effects of homo- and hetero-type co-doping of B, C and N on structural and electronic properties of MgO monolayers (MLs). The co-doping sites considered here are the possible equivalent and non-equivalent positions of a hexagon in a pristine MgO ML. The planarity of the monolayers is found to be governed by the site selectivity of the dopant atoms as well as the positions of doping. Planar monolayers have a higher likelihood of formation than the non-planar monolayers. In case of non-equivalent doping, the doping atoms always prefer positions that are closer. Stepwise substitution is more likely to occur than simultaneous substitution in formation of the co-doped monolayers. Most of the co-doping combinations introduce magnetism to the pristine MgO ML. Hetero-type monolayers prefer to be in magnetic states and even exhibit higher magnetic moments than homo-type MLs, with a maximum value of 4 μB for B–N co-doping. Almost all the monolayers are semiconducting with significantly reduced band gaps, while few hetero-type monolayers are metallic in nature. The electronic energy band gaps of the monolayers are compatible with the IR and visible regions of the electromagnetic spectrum. The overall tuning of the electronic properties renders the co-doped MgO monolayers effective for applications in spintronics and optoelectronics.