The effect of vacancies and the substitution of p-block atoms on single-layer buckled germanium selenide

Single-layer GeSe is a new candidate in the two-dimensional family of materials. In our recent study, we showed that GeSe can form a stable buckled honeycomb structure (b-GeSe) and is a semiconductor with a 2.29 eV band gap. This paper investigates the effect of point defects of both hole (Ge, Se) and substitution doping of p-block elements, in single-layer b-GeSe, based on first principles plane wave calculations within spin-polarized density functional theory. In the case of the substitution process, we present an extensive analysis of the effects of substituting atoms (Al, As, Cl, P, C, N, Ge or Se, Si, B, F, Ga and S) on the electronic and magnetic properties of the b-GeSe phase. Our results show that nonmagnetic and semiconducting b-GeSe can be half-metallized by Ge vacancies, while it remains a semiconductor with Se vacancies with a decreasing band gap value. The results of the substitution process can be categorized by the group number in the periodic table. b-GeSe remains a nonmagnetic semiconductor upon the substitution of defects with group IVA and VIA atoms on either the Ge or Se position of the b-GeSe structure. On the other hand, the results show that the influence of group IIIA and VIIA atoms is obvious, as these atoms raise the net magnetic moments (1 mu(B) to 3 mu(B)) of the new b-GeSe system. In particular, the system shows half-metallicity when the Se atoms are replaced with group IIIA atoms. The system has a net magnetic moment when substituting group VA atoms for Se atoms, whereas it does not when substituting them for Ge atoms (except for N). We believe that these results are useful for the further functionalization of b-GeSe with point defects.