Tuning of electronic and optical properties of a predicted silicon allotrope: Hexagonal silicon h10 -Si

Abstract

The indirect band gap of the diamondlike silicon does not allow direct travel of electrons between valence band and conduction band edges, which has limited its application and performance in optoelectronic devices. Searching new silicon allotropes with highly tunable or direct band gap becomes more and more urgent with the increasing demand on clean energy. Here, we predict a silicon allotrope, $h10$-Si, which is an indirect-gap semiconductor with a band gap of about 0.96 eV. Furthermore, the electronic and optical properties exhibit a strong dependence on strain. In particular, the indirect band gap of the predicted silicon allotrope can be switched to a direct band gap at a uniaxial tensile strain of about 8% and the light absorption can be tuned continuously in a wide range of photon energy. Besides, the single-layer counterpart of this allotrope is confirmed to be dynamically stable and more stable in energy than silicene, endowing it with potential applications in nanoscale devices.