First-principles study on the electronic, magnetic and optical properties of the novel squared SN2 monolayer with 3d transition metal doping and point vacancy

The SN2 monolayer with a square lattice (S-SN2) is a non-magnetic semiconductor. The lack of magnetism and the weak light absorption severely limit its further applications in spintronic and optoelectronic devices. Herein, we investigate the effects of 3d transition metal (Fe, Co and Ni) substitution doping and point vacancy engineering on the S-SN2 monolayer using first-principles calculations. The negative binding energies and the AIMD simulations indicate that all doped cases exhibit excellent structural stability. After doping, the diverse properties including ferromagnetic spin semiconducting behavior, non-magnetic semiconducting property, and significant ferromagnetic half-metallic character with 100 % spin polarization can be realized among these doped S-SN2 monolayers. Interestingly, the value of work function for S-SN2 monolayer can be regulated by doping from 6.55 eV for pure S-SN2 monolayer to a range of 5.11-6.89 eV for doped systems. Moreover, the visible light absorption of S-SN2 monolayer can be significantly enhanced by Fe doping, reaching a high value of about 1.2x105 cm-1. Additionally, a non-magnetic metal and a ferromagnetic half-metallic character with a large total magnetic moment of 5.93 mu B can be induced in S-SN2 monolayer with a single N and S vacancy, respectively.