Tuning the electronic structure of GeC/WS2 van der Waals heterostructure by electric field and strain: A first principles study

Abstract

Van der Waals (vdW) heterostructures made by stacking two-dimensional (2D) materials, open up a wide landscape of possibilities in bandgap engineering, due to the distinct properties of the building layers and diverse stacking arrangements possible. In this work, ab initio calculations based on density functional theory were performed to systematically investigate the tuning of electronic properties of GeC/WS2 heterostructures by applying either a vertical external electric field or a biaxial strain. GeC/WS2 heterostructures exhibit a direct band gap and a type-II vdW heterostructure. The bandgap of GeC/WS2 heterostructure can be dramatically modulated by applying a vertical external electric field or a biaxial strain, and semiconductor-metal transitions are observed under high electric field and large strain. The change of band gap is due to the shift of band edges of the heterostructure due to the static electric field induced potential energy and strain induced deformation potential. Differences in the pattern of change style can be assigned to changes of the bands assigned to CBM and VBM. It is interesting to note that the shift of band edge by electric field is screened by a factor of 3.54 as compared to the electrostatic calculation. The deformation potential of the CBM consisted of W 5d orbital is −1.58 eV, and that of the VBM consisted of C 2p orbital is −0.01 eV. In addition, the optical properties of the heterostructure exhibit a significant enhancement compared to the constituent layers, which indicates improved light absorption. The above results suggest that GeC/WS2 vdW heterostructures can find applications as opto-electronic devices and efficient solar energy harvesting materials.