Strain-induced metal-semiconductor transition in monolayers and bilayers of gray arsenic: A computational study

We study the equilibrium geometry and electronic structure of thin films of layered gray arsenic using ab initio density functional theory. In contrast to bulk gray As that is semimetallic, thin films display a significant band gap that depends sensitively on the number of layers, in-layer strain, layer stacking, and interlayer spacing. We find that metallic character can be introduced by increasing the number of layers beyond two or by subjecting semiconducting monolayers and bilayers to moderate tensile strain. The strain-induced metal-semiconductor transition is triggered by changes in the band ordering near the top of the valence band that causes an abrupt change from sigma to pi character of the frontier states.