Band Gap and Edge Engineering via Ferroic Distortion and Anisotropic Strain: The Case of SrTiO$_{3}$

TL;DR

This study uses advanced computational methods to explore how ferroic distortions and anisotropic strain influence the electronic band structure of SrTiO$_{3}$, revealing pathways for tunable band gap engineering.

Contribution

It demonstrates how ferroic distortions and anisotropic strain can be used to controllably modify the band gap and edges of SrTiO$_{3}$, providing new strategies for material engineering.

Findings

Anisotropic strain reduces the band gap by breaking degeneracies.

Ferroic distortions widen the band gap through orbital mixing.

Specific growth orientations can significantly lower the band gap at room temperature.

Abstract

The effects of ferroic distortion and biaxial strain on the band gap and band edges of SrTiO$_{3}$ (STO) are calculated using density functional theory and many-body perturbation theory. Anisotropic strains are shown to reduce the gap by breaking degeneracies at the band edges. Ferroic distortions are shown to widen the gap by allowing new band edge orbital mixings. Compressive biaxial strains raise band edge energies, while tensile strains lower them. To reduce the STO gap, one must lower the symmetry from cubic while suppressing ferroic distortions. Our calculations indicate that for engineered orientation of the growth direction along [111], the STO gap can be controllably and considerably reduced at room temperature.