Effects of the in-plane uniaxial and biaxial strains on the electronic and optical properties of the graphene/β-Si3N4 heterostructure

Abstract

van der Waals heterostructures can enable adjustment of graphene's electronic properties, which is important for the application of graphene-based electronic devices. The structural, electronic and optical properties of heterostructures composed of graphene and β-Si₃N₄ under different strain conditions are studied in this paper using first-principle calculation. The result shows that the heterojunction constituted with β-Si₃N₄ opens a small bandgap at the Brillouin zone Γ, which is about 0.099 eV, and the bandgap is highly sensitive to the direction and magnitude of strain. Under uniaxial compressive (tensile) strain, the heterojunction bandgap increases linearly, reaching 1.901 eV and 1.614 eV at −11 % and 11 %, respectively; under biaxial strain, the heterojunction bandgap decreases linearly with the compressive strain, decreasing to 0.087 eV at −11 %, and increases linearly with the tensile strain, reaching 0.113 eV at 11 %. And the rate of the bandgap under uniaxial strain is larger than that under biaxial strain, which suggests that the uniaxial strain regulation is more effective. Optical property study shows that uniaxial (biaxial) compressive strain improves the light absorption of the heterojunction in the blue-ultraviolet region band, especially when the uniaxial compressive strain reaches 9 %, the light absorption of the heterojunction increases significantly in the whole spectral interval. These research results will provide a theoretical basis for the practical applications of graphene and β-Si₃N₄ heterostructures in the fields of pressure sensors and optical modulators.