Surface state at BaSnO₃ evidenced by angle-resolved photoemission spectroscopy and ab initio calculations

Perovskite alkaline earth stannates, such as BaSnO₃ and SrSnO₃, showing light transparency and high electrical conductivity (when doped), have become promising candidates for novel optoelectrical devices. Such devices are mostly based on hetero-structures and understanding of their electronic structure, which usually deviate from the bulk, is mandatory for exploring a full application potential. Employing angle resolved photoemission spectroscopy and ab initio calculations we reveal the existence of a 2-dimensional metallic state at the SnO₂-terminated surface of a 1% La-doped BaSnO₃ thin film. The observed surface state is characterized by distinct carrier density and a smaller effective mass in comparison with the corresponding bulk values. The small surface
effective mass of about 0.12_me can cause an improvement of the electrical conductivity of BSO based heterostructures.