Strain-induced energy band gap opening in two-dimensional bilayered silicon film

TL;DR

This theoretical study investigates how in-plane biaxial strain can induce an energy band gap in bilayered silicon films, revealing strain thresholds for band gap opening and structural changes.

Contribution

It demonstrates the strain-induced transition from zero-gap to finite-gap electronic structures in bilayered silicon films using density functional theory.

Findings

Maximum band gap of ~168 meV at 14.3% strain

Strain reduces buckling height and can flatten structures

Band gap opening occurs at strains between 10.7% and 15.4%

Abstract

This work presents a theoretical study of the structural and electronic properties of bilayered silicon films under in-plane biaxial strain/stress using density functional theory. Atomic structures of the two-dimensional silicon films are optimized by using both the local-density approximation and generalized gradient approximation. In the absence of strain/stress, five buckled hexagonal honeycomb structures of the bilayered silicon film have been obtained as local energy minima and their structural stability has been verified. These structures present a Dirac-cone shaped energy band diagram with zero energy band gaps. Applying tensile biaxial strain leads to a reduction of the buckling height. Atomically flat structures with zero bucking height have been observed when the AA-stacking structures are under a critical biaxial strain. Increase of the strain between 10.7% ~ 15.4% results in a band-gap opening with a maximum energy band gap opening of ~168.0 meV obtained when 14.3% strain is applied. Energy band diagram, electron transmission efficiency, and the charge transport property are calculated.