Exploration of new Janus GeBrI monolayer for optoelectronic and spintronic applications

Abstract

Two-dimensional (2D) materials have been explored for diverse applications, where multifunctional candidates with two or more functions are desired. In this work, new Janus GeBrI monolayer with interesting electronic and magnetic properties is investigated. Standard PBE and hybrid HSE06 functionals assert the indirect gap semiconductor behavior of pristine monolayer with band gap of 2.28 and 3.04 eV, respectively. Novel feature-rich properties can be induced in Janus GeBrI monolayer by defect engineering and doping. Specifically, single Ge vacancy (VGe) metalizes the monolayer without magnetism. Similarly, the non-magnetic nature is kept by doping with IIA-group (Be and Mg: BeGe and MgGe) atoms, where the energy gap exhibits a slight increase of the order between 1.32% and 3.51%. In contrast, this 2D material is significantly magnetized by single halogen vacancy (VBr and VI), doping with IIIA-group (Al and Ga: AlGe and GaGe) atoms, and doping with chalcogen (Se and Te: SeBr, SeI, TeBr, and TeI) atoms. In these cases, total magnetic moments between 0.61 and 1.00 μB are obtained, where impurities and those atoms closest to the defect/doping site originate mainly the system magnetism. Moreover, VBr, VI, AlGe, GaGe systems exhibit the diluted magnetic semiconductor nature, while SeBr, SeI, TeBr, and TeI systems are classified as 2D half-metallic structures. Further, Bader charge analysis indicates the charge loser of IIIA- and IIA-group impurities when transferring charge to the host monolayer. Meanwhile, chalcogen dopants are charge gainers attracting charge from the host monolayer. The presented results introduce new stable Janus GeBrI monolayer with relative large intrinsic band gap, further functionalization processes based on the vacancy defects and doping of this 2D material may make prospective 2D spintronic materials.