Band-gap engineering and optoelectronic properties of 2D WSi2N4 nanosheets: A first principle calculations

Abstract

The successful growth of centimeter-scale monolayer films of MoSi 2 N 4 and WSi 2 N 4 has attracted great interest (Science 369, 670, 2020). Here, we systematically investigate the effects of biaxial and uniaxial strain on the electronic structures of WSi 2 N 4 nanosheets with different layers of monolayer(ML), bilayer(BL) and trilayer(TL), respectively, by using first-principles calculations. In addition, combined with the non-equilibrium Green’s function methods, the photoelectronic response of WSi 2 N 4 ML is also explored. The results indicate that: 1) The biaxial and uniaxial strain can flexibly increase or decrease the band gap of WSi 2 N 4 nanosheets. Particularly, tensile strain realizes the transition of WSi 2 N 4 nanosheets from semiconductor to metal. 2) The tensile strain effectively improves the optical properties of WSi 2 N 4 nanosheets in the visible light region, and the red/blue shift of the absorption peaks is observed in the optical spectrum by tensile/compressive strain. 3) The pin-junction photodiode of WSi 2 N 4 ML generates sizable photocurrents under illumination, showing a strong photoelectronic response to purple light. Furthermore, the biaxial tensile strain significantly enhances the photoelectric performance of the WSi 2 N 4 photodiode and effectively modulates its detection range in the visible region. Hence, our findings suggest that WSi 2 N 4 nanosheets are a promising multifunctional material for nanoelectronic and optoelectronic applications. • Electronic structure and optoelectronic properties studies of the 2D WSi 2 N 4 nanosheets. • Strain engineering can effectively modulate the band gap and optical properties of WSi 2 N 4 nanosheets. • The pristine WSi 2 N 4 monolayer is predicted to be a good photoelectric sensor, showing a strong photoelectronic response to purple light. • The tensile strain significantly enhance the photoelectric performance of the WSi 2 N 4 photodiode and effectively modulates its detection range in the visible region.