Tunable spin-polarized band gap in Si/NiI vdW heterostructure.

Using density functional theory (DFT) calculations we investigate the structural and electronic properties of a heterogeneous van der Waals (vdW) structure consisting of silicene and NiI single layers. We observe an interaction between the two layers with a net charge transfer from the ferromagnetic semiconductor NiI to silicene, breaking the inversion symmetry of the silicene structure. However, the charges flow in opposite directions for the two spin channels, which leads to a vdW heterostructure with a spin-polarized band gap between the π and π* states. The band gap can be tuned by controlling the vertical distance between the layers. The features shown by this vdW heterostructure are new, and we believe that silicene on a NiI layer can be used to construct heterostructures which have appropriate properties to be used in nanodevices where control of the spin-dependent carrier mobility is necessary and can be incorporated into silicon based electronics.