  There has been growing interest in perovskite BaSnO3 due to its desirable
properties for oxide electronic devices including high electron mobility at
room temperature and optical transparency. As these electronic and optical
properties originate largely from the electronic structure of the material,
here the basic electronic structure of epitaxially-grown BaSnO3 films is
studied using high-energy-resolution electron energy-loss spectroscopy in a
transmission electron microscope and ab initio calculations. This study
provides a detailed description of the dielectric function of BaSnO3, including
the energies of bulk plasmon excitations and critical interband electronic
transitions, the band structure and partial densities of states, the measured
band gap, and more. To make the study representative of a variety of deposition
methods, results from BaSnO3 films grown by both hybrid molecular beam epitaxy
and high pressure oxygen sputter deposition are reported.
