Two-dimensional SnSe/GeSe van der Waals heterostructure with strain-tunable electronic and optical properties

Abstract

Two dimensional materials have a bright prospect for some strain-tunable applications due to their ultrathin and flexible characteristics. In this work, SnSe/GeSe van der Waals heterostructure is first constructed based on the GeSe and SnSe monolayers, and then their electrical and optical properties are investigated by first-principles calculations. Furthermore, the effects of strain on the electrical and optical properties of SnSe/GeSe are also studied. SnSe/GeSe is found to be a direct semiconductor with a band gap range from 0.19 eV to 0.83 eV, which can be flexiblely tuned by the in-plane strain. Under the uniaxial strains εa and εb, the tunable ranges of strain and direct bandgap are much smaller than those under the biaxial strain εu. Transformation between direct and indirect bandgap in SnSe/GeSe occurs under some applied strains. Being capable to absorb ultraviolet and far-ultraviolet light, SnSe/GeSe exhibits higher peak of absorption coefficient and the imagery part of dielectric function than those of GeSe and SnSe. Under small in-plane strains range from −0.06 to 0.06, anisotropy of SnSe/GeSe can be found in the optical parameters. The peaks of the absorption coefficient and dielectric function both increase with the decrease of strain. The light absorption capability of SnSe/GeSe becomes stronger with smaller in-plane strains, in which the biaxial strain is the most effective way to tune the optical properties. With these intriguing properties, SnSe/GeSe will be a promising two-dimensional material for applications in nanomechanics and optoelectronics.