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Based on the first principles of the GGA method, the magnetic and optical properties of intrinsic SnS2, Fe, Cr mono-doped SnS2 and (Fe, Cr) co-doped SnS2 are studied. The results...

Building two-dimensional (2D) vertical van der Waals heterostructures (vdWHs) is one of the effective methods to regulate the properties of single 2D materials. In this paper, we stack the hexagonal boron nitride (h-BN) monolayer (ML) on the SnSe 2 ML to construct the stable h-BN/SnSe 2 vdWH, of which the crystal and electronic structures, together with the optical properties, are also analyzed by the firstprinciples calculations. The results show that the h-BN/SnSe 2 vdWH belongs to a type-I heterostructure with an indirect bandgap of 1.33 eV, in which the valence band maximum and conduction band minimum are both determined by the component SnSe 2 ML. Interestingly, the h-BN/SnSe 2 vdWH under the tensile strain or electric field undergoes the transitions both from type-I to type-II heterostructure and from the indirect to direct bandgap semiconductor. In addition, the carrier mobility of the h-BN/ SnSe 2 heterostructure has a significant enhancement relative to that of the SnSe 2 ML, up to 10 4 cm 2 V −1 s −1 . Meanwhile, the h-BN/SnSe 2 heterostructure presents the superb optical absorption and unique type-II hyperbolic property. Our findings will broaden the potential applications of SnSe 2 ML and provide theoretical guidance for the related experimental studies.

The electronic structures and magnetic properties of diverse transition metal (TM = Fe, Co, and Ni) and nitrogen (N) co-doped monolayer MoS2 are investigated by using density functional theory. The results show that the intrinsic MoS2 does not have magnetism initially, but doped with TM (TM = Fe, Co, and Ni) the MoS2 possesses an obvious magnetism distinctly. The magnetic moment mainly comes from unpaired Mo:4d orbitals and the d orbitals of the dopants, as well as the S:3p states. However, the doping system exhibits certain half-metallic properties, so we select N atoms in the V family as a dopant to adjust its half-metal characteristics. The results show that the (Fe, N) co-doped MoS2 can be a satisfactory material for applications in spintronic devices. On this basis, the most stable geometry of the (2Fe–N) co-doped MoS2 system is determined by considering the different configurations of the positions of the two Fe atoms. It is found that the ferromagnetic mechanism of the (2Fe–N) co-doped MoS2 system is caused by the bond spin polarization mechanism of the Fe–Mo–Fe coupling chain. Our results verify that the (Fe, N) co-doped single-layer MoS2 has the conditions required to become a dilute magnetic semiconductor.