Mobility Optimization in High-Pressure-Oxygen-Sputtered Epitaxial Ba_1-xLa_xSnO₃ Thin Films

Due to its high 300 K mobility and wide gap, perovskite BaSnO₃ is of high interest for oxide electronics. Despite rapid progress, many questions remain regarding transport behavior, particularly in films, where defects limit mobility. While many publications investigating epitaxial BaSnO₃ to date have focused on PLD or MBE grown films, here we focus on an industrially relevant, scalable technique: high pressure oxygen sputtering. In this work, single-phase, stoichiometric, smooth, epitaxial films of Ba_0.98La_0.02SnO₃ have been grown, and the impact of thickness, growth rate, deposition temperature, and substrate on mobility systematically studied. 300 K mobilities up to 70 cm²V^-1s^-1 at 2 ×10²⁰ cm^-3 are obtained, even in 380-Å-thick unbuffered films. Important trends include a monotonic increase in mobility with deposition temperature, reduced mobility and carrier freeze-out at low thickness, optimal mobility around 1200 Å thickness, and insensitivity to the substrate mismatch. These are discussed in terms of accompanying structural characterization data, particularly transmission electron microscopy.