Electronic band structure and optical phonons of BaSnO3 and Ba0.97La0.03SnO3 single crystals: Theory and experiment

Abstract

Optical properties of insulating BaSnO3 (BSO) and conducting Ba0.97La0.03SnO3 (BLSO) single crystals were studied at room temperature in a wide spectral range between 0.01 and 5.9 eV by means of spectroscopic ellipsometry. The far-infrared spectra of the optical phonons in BSO and BLSO were complemented by polarized Raman scattering measurements in BSO. The electronic band structure and the optical response (dielectric function) were calculated using density functional theory, which allowed for the interpretation of the main spectroscopic features such as optical phonons and electronic interband transitions. To reconcile the observed experimental spectra with the theory, a departure from the ideal perovskite structure on the local scale was proposed for BSO.