First principles insight of silicene-ZnS-silicene trilayer heterostructure

Abstract

Using Density Functional Theory (DFT), 2D hexagonal silicene-ZnS-silicene trilayer heterostructure was studied with van der Waals correction as implemented in Grimme’s method. Small lattice mismatch of about 0.77% only between silicene and ZnS monolayer suggest ease in formation of sandwiched heterostructure. The negative value of total energy at 298 K from MD simulation confirms its ground state stability. Unlike monolayer silicene, our trilayer heterostructure exhibits a direct band gap of 0.63 eV in its equilibrium state. Calculated elastic moduli predict that Si-ZnS-Si has an enhanced ability to resist tensile and shear deformation than the pristine silicene and ZnS monolayer. Due to strong van der Waal’s interaction between the layers, Si-ZnS-Si has much lower thermal coefficient of linear expansion and therefore is more stable against any thermally induced deformation. When a transverse external electric field is applied, we observe direct-to-indirect band gap transition. On increasing the electric field further, the heterostructure remains indirect band gap semiconductor until it abruptly transforms to metallic nature at 1.0 V/Å. Theoretical prediction of heterostructure property presented in this work may provide valuable data for developing future nanoelectronic devices.