Composition dependent mobility and bandgaps in (La0.05BaxSr0.95−x)SnO3 epitaxial films

Abstract

Perovskite stannates ASnO3 (A = Ba, Sr) as transparent conducting oxides have recently attracted much attention due to their high electron mobility and high optical transparency. Here, we investigated experimentally and theoretically the composition-dependent structural, electrical, and optical properties of (La0.05BaxSr0.95−x)SnO3 (LBSSO, x = 0–0.95) thin films. Detailed x-ray diffraction characterization studies show that the LBSSO films were epitaxially grown on the LaAlO3(001) substrates. The out-of-plane lattice constants of the LBSSO films increase from 4.045 to 4.122 Å with incorporation of the Ba content from 0 up to 0.95 in the films. The electron mobility values of the films increase gradually from 22.2 to 34.4 cm2/V s with the increasing Ba contents. The direct/indirect optical bandgaps decrease monotonously from 4.64/4.04 to 4.05/3.40 eV upon changing the Ba content from 0 to 0.95. Density functional theory calculations indicated that the Ba substitution can reduce the electron effective mass and the bandgaps, leading to a higher carrier mobility.