Electronic and magnetic properties of defective and Fe-doped InS monolayers adjusted by hole doping as a second functionalization step: a first-principles study

Abstract

In this work, hole doping is proposed as a second functionalization step to modify the electronic and magnetic properties of defective and Fe-doped InS monolayers. The pristine monolayer is confirmed to be a two-dimensional (2D) material with an indirect gap of 1.65 eV, whose In–S chemical bonds exhibit both covalent and ionic characters. The creation of a single In vacancy (1Va_In) or a pair of In vacancies (2Va_In) induces half-metallicity in the InS monolayer. In these cases, total magnetic moments of 1.00 and 2.00µ_B, respectively, are obtained, where S atoms closest to defect sites produce primarily the system magnetic moments. Meanwhile a single S vacancy (1Va_S) induces no magnetism, however this defect causes a band gap reduction of the order of 28.48%. Significant magnetism is also obtained by Fe doping (Fe_In) with an overall moment of 5.00µ_B, originating primarily from the transition metal impurity. Moreover, a magnetic semiconductor nature is also developed in the InS monolayer through doping with an Fe atom. The in-plane magnetic anisotropy (IMA) is confirmed for the magnetic 1Va_In@mo, 2Va_In@mo, and Fe_In@mo systems. Further, the pristine InS monolayer is magnetized with a hole concentration of 1.5 holes per supercell. Both the magnetization and IMA of the 1Va_In@mo system can be significantly enhanced by hole doping, while the magnetism in the 2Va_In@mo system disappears upon adding a hole in its lattice. The nonmagnetic 1Va_S@mo system becomes magnetic when it has been hole-doped with total magnetic moment up to 0.89µ_B. It is found that hole doping enhances the IMA of the Fe_In@mo system, despite its magnetic moment reducing. In addition, the electronic structures of the considered InS systems can be effectively controlled by hole doping, where the hole level plays a key role. Our findings pave a solid way to functionalize the InS monolayer towards diverse spintronic and optoelectronic applications.