Exploiting the stereoelectronic effects for selective tuning of band edge states of α-SnO: GW quasiparticle calculations

Abstract

Tuning the electronic structure of materials, and thus their electronic, transport, and optical properties, is of fundamental importance for materials design and optimization. Although alloying is a well-established method for engineering the band gap of semiconductors, strain engineering has emerged as a promising approach to selective tuning of band-edge states. Using a combined density functional theory and $GW$ approach, we show that the highly directional intralayer and interlayer couplings, together with the unusual stereoelectronic effects of the Sn $5s$ lone pair in \ensuremath{\alpha}-SnO, may be exploited to tune, in addition to the band gap, the valence and conduction band-edge states selectively using in-plane and/or out-of-plane strains. Whereas the uniaxial strain along the lattice $c$ direction primarily affects the position of the conduction band edge, the valence band edge is very sensitive to the biaxial $ab$ strain. We also establish a strain electronic phase diagram of \ensuremath{\alpha}-SnO, including the insulator--metal phase transition boundary. It is predicted that a compressive biaxial strain of about 3% or an isotropic pressure of 5 GPa can trigger an insulator--metal transition. The quasiparticle band gap can be widely tuned from 0 to more than 2.0 eV with moderate strains.