Effects of Si-doped and shear strain on the optoelectronic properties of WSe2: A first principles study.

CONTEXT: Two-dimensional transition-metal dichalcogenides such as WSe2 are promising platforms for tunable optoelectronic devices. Here, first-principles molecular modeling is used to examine how substitutional Si doping combined with shear strain tunes the electronic and optical properties of monolayer WSe2. Si dopants introduce localized states that reduce the band gap from 1.599 to 1.029 eV and enhance low-energy absorption. Shear strain applied along orthogonal in-plane directions (xy and yx) further induces direction-dependent electronic localization and band-gap renormalization, giving rise to anisotropic optical absorption. These results provide mechanistic insight and a simple strategy for tailoring the optoelectronic response of WSe2-based materials.

METHODS

Density functional theory calculations within the generalized-gradient approximation are performed using the Perdew-Burke-Ernzerhof functional and Gaussian-type basis sets as implemented in the Materials Studio package. Substitutional Si doping is modeled in a WSe2 supercell, and shear strain is introduced by distorting the in-plane lattice vectors along the xy and yx directions. For each configuration, fully relaxed geometries are used to evaluate the electronic band structures, charge redistribution, and complex dielectric function. Optical absorption spectra are obtained from the frequency-dependent dielectric tensor within the independent-particle approximation.