Band Gap Engineering of SnO₂ by Epitaxial Strain: Experimental and Theoretical Investigations

The effect of mis-match strain on the structural, electronic, and optical properties in SnO2 epitaxial thin films has been systematically investigated by the experimental and theoretical methods. Our results indicate that the tensile strain exists in the thin film and decreases with the thickness of epitaxial samples. Besides, the optical band gap significantly reduces with increasing the tensile strain in the bc plane. Our hybrid functional calculations present that the narrowing of band gap of SnO2 under tensile strain is due to the weakening of bonding and antibonding split, which results from the disorder of SnO6 octahedra, and the biaxial strain is found to be more efficient than the uniaxial strain for tuning the band gap of SnO2.