Orthorhombic YMnO3 thin films were epitaxially grown on bare and LaNiO3 buffered (0 0 1)- SrTiO3 substrates by pulsed laser deposition under various oxygen pressures from 5 to 30 Pa. The crystal structure and microstructure of these films have been characterized by both X-ray diffractions and transmission electron microscopy. The leakage current, modeled as the space charge limited current (SCLC) mechanism, decreased significantly with the increase of oxygen content. It is further found that the magnetic property of films is greatly enhanced in YMnO3 films grown under high oxygen pressure, which can be explained decreased oxygen vacancies. In addition, bipolar switching behavior was obtained only in the films grown under 30 Pa oxygen pressure, which is attributed to the decrease of voltage-driven oxygen vacancy migration. (C) 2011 Elsevier B.V. All rights reserved.