Effect of biaxial strain on SnO2 bandgap: First-principles calculations

In the present study, the variation of the band gap energy with biaxial strain in SnO
2
in its bulk form is examined using state-of-the-art first-principles calculations. All calculations were based on DFT within the Tran-Blaha modified Becke-Johnson exchange potential approximation (TB-mBJ). Under biaxial compressive and tensile strain, the projected densities of states showed that valence and conduction bands blue- and red-shift respectively. Hybrid oxygen and tin conduction states were shown to provide covalent bonding interaction which directly affects the band gap. In the case of a tensile strain, a decrease of the charge distribution around tin sites is observed which elongates the Sn-O bond and decreases the band gap energy. However, an opposite behavior is demonstrated in the case of compression which clearly demonstrates the ability of strain to modulate the band structure. Finally, our results suggest that the SnO2 structure is very flexible and by mechanical strain we can efficiently modulate its electronic properties and band gap to improve its suitability for optoelectronic and thermoelectric applications.