Hybrid MBE growth of La-doped BaSnO₃ epitaxial films on atomically smooth SrTiO₃ nanomembranes

Heteroepitaxy enables the integration of lattice-mismatched materials, but it often introduces defects such as dislocations in the film which is a long-standing challenge in epitaxial growth of functional layers on lattice-mismatched substrates. In this work, we investigate the role of substrate thickness on strain relaxation by growing BaSnO₃ films on SrTiO₃ nanomembranes transferred onto host substrates. Single-crystalline, epitaxial BaSnO₃ films with a bulk-like lattice parameter of 4.116 Å were successfully grown using hybrid molecular beam epitaxy. Controlled La doping was employed to achieve shallow n-type doping. By systematically varying both the BaSnO₃ film thickness and SrTiO₃ nanomembrane thickness, we establish a growth-structure-property diagram correlating dislocation density, carrier concentration, and mobility.