Stability of the oxygen vacancy induced conductivity in BaSnO3 thin films on SrTiO3

Abstract

BaSnO3 (BSO) has emerged as a major candidate for exploration of a variety of functional device applications. In this letter, we report on the role of the oxygen vacancy concentration in the electronic states, the crystal structure, and the transport properties of BSO thin films grown on SrTiO3 substrates by pulsed laser deposition. We fabricated five BSO films systematically reducing the deposition oxygen pressure from 1 × 10−1 Torr to 5 × 10−3 Torr. The BSO films show gradual transition from an insulating one fabricated at 1 × 10−1 Torr to highly conducting ones with decreasing deposition oxygen pressure. X-ray photoelectron spectroscopy measurements show the increasing oxygen vacancy concentration as a function of the decreased deposition oxygen pressure. Films deposited at 5 × 10−3 Torr displayed the lowest room temperature resistivity (1.73 mΩ cm) and the highest concentration of oxygen vacancies. Temperature-dependent resistivity of the samples deposited at low oxygen pressures suggests the presence of shallow states near the conduction band. With decreasing oxygen pressure, the out-of-plane lattice parameter of BSO increases while the in-plane lattice parameter remains nearly the same. Oxygen deficient conducting BSO films with high oxygen vacancies exhibited excellent structural, electronic, and valence state stabilities when they were post-annealed at temperatures up to 760 °C.