The electronic and optical properties of silicene/g-ZnS heterobilayers: a theoretical study

摘要

Two-dimensional (2D) nanomaterials have rapidly become the superstars in the fields of nanoelectronics, materials science, and energy storage because of their unusual properties, originating from the quantum size effects. Here we present a systematic theoretical investigation of the electronic and optical properties of silicene/g-ZnS heterobilayers, by means of dispersion-corrected density functional theory (DFT-D) computations. Depending on the stacking, the orbital hybridization or weak interaction defines the conformation of silicene/g-ZnS heterobilayers and contributes to their stability. Unlike silicene, the silicene/g-ZnS heterobilayer in the most stable stacking is a direct band gap semiconductor with a rather low effective mass, which indicates that the heterobilayer has a high carrier mobility. Applying an appropriate external electric field (E-field) or biaxial tensile strain with different strengths, the band gap of the silicene/g-ZnS heterobilayer can be effectively tuned, and correspondingly results in a semiconductor metal transition. Meanwhile, with increase of the E-field strength, the binding strength of the silicene/g-ZnS heterobilayer can be significantly enhanced. Especially, changing the direction and strength of the external E-field can significantly modulate its work function in a wide range. From analysis of the dielectric function and the absorption coefficient, it is evident that the optical properties of silicene are largely preserved in the heterobilayer, meanwhile, the silicene/g-ZnS heterobilayer exhibits some unique optical properties in the visible light irradiation range. Our findings pave the way for experimental research in the development of 2D materials science using heterostructures and indicate the great application potential of silicene/g-ZnS heterobilayers in future nanoelectronics and optoelectronics.