Regulating the Electronic and Magnetic Properties of a SnSSe Janus Monolayer toward Optoelectronic and Spintronic Applications

In this work, efficient approaches to modify the electronic and magnetic properties of the SnSSe monolayer are proposed. A pristine monolayer is a nonmagnetic two-dimensional (2D) semiconductor material with an energy gap of 0.96(1.64) eV obtained from PBE (HSE06)-based calculations. Different single vacancies, divacancies, and trivacancies make the appearance of middle-gap energy states to tune the SnSSe monolayer electronic structure without producing magnetism. Specifically, the monolayer is metallized by a single chalcogen vacancy. Meanwhile, large band-gap reductions on the order of 88.84%, 38.54%/65.63%, and 43.75% take place upon the creation of single Sn vacancy, Sn+S/Sn+Se divacancy, and Sn+S+Se trivacancy, respectively. Significant magnetization is induced by doping with transition metals. Consequently, total magnetic moments of 1.00, 2.00, 3.00, and 4.00 μ B are obtained by doping with V, Cr, Mn, and Fe atoms, respectively. In these cases, magnetic properties are produced mainly by localized 3d electrons of metal impurities. The V-/Fe- and Cr-/Mn-doped systems exhibit feature-rich half-metallic and diluted magnetic semiconductor structures, respectively. As a representative with the smallest doping energy, the magnetic ordering in the 2Cr-doped system is further investigated. A ferromagnetic spin-gapless semiconductor nature is found in the 2Cr-1 system with two neighboring Cr atoms. Further separating Cr impurities allows the transition to antiferromagnetic semiconductor nature. The results presented herein may propose efficient functionalization methods to make the SnSSe monolayer a prospective optoelectronic and spintronic 2D material.