Frequency- and temperature-dependent dielectric response in hybrid molecular beam epitaxy-grown BaSnO3 films

We report on the dielectric response of epitaxial BaSnO₃ films grown on Nb-doped SrTiO₃ (001) substrates using a hybrid molecular beam epitaxy approach. Metal-insulator-metal capacitors were fabricated to obtain frequency- and temperature-dependent dielectric constant and loss. Irrespective of film thickness and cation stoichiometry, the dielectric constant obtained from Ba_1−xSn_1−yO₃ films remained largely unchanged at 15-17 and was independent of frequency and temperature. A loss tangent of ∼1 × 10⁻³ at 1 kHz < f < 100 kHz was obtained for stoichiometric films, which increased significantly with non-stoichiometry. Using density functional theory calculations, these results are discussed in the context of point defect complexes that can form during film synthesis.