Tuning electronic properties of silicane layers by tensile strain and external electric field: A first-principles study

The structural and electronic properties of silicane layers and bulk, the effects of a biaxial tensile strain and an external electric field (E-field) on the electronic properties of silicane monolayer and bilayer are investigated using density functional theory computations with the van der Waals (vdW) correction. It is demonstrated that the weak vdW interaction between silicane layers can efficiently tune the electronic properties of silicane multilayers. The silicane multilayers (up to 5) are indirect bandgap semiconductors whose bandgap slightly decreases with the number of layers, whereas bulk silicane is a direct bandgap semiconductor. The bandgaps of both silicane monolayer and bilayer can be flexibly modulated by applying a biaxial tensile strain, and indirect-direct transition occurs when the biaxial tensile strain reaches 4% and 2% respectively. Besides, the bandgaps of the silicane monolayer and bilayer can also be continuously modulated by an external E-field, with an indirect-direct transition observed when its magnitude reaches 0.5 and 0.7 V/Å respectively. A larger E-field can trigger semiconductor-metal transition at approximately 0.8 V/Å for both silicane monolayer and bilayer. Our results provide rather effective and flexible approaches to tuning the electronic properties of silicane layers for application in silicane-based electronic and optoelectronic devices.