Effects of oxygen pressure on electrical properties of (Na0.5K0.5)NbO3 films grown on Pt/Ti/SiO2/Si substrates

Abstract

(Na0.5K0.5)NbO3 (NKN) films were annealed under various oxygen partial pressures (OPPs), and the effect of the OPP on the electrical properties of the NKN films was investigated. The dielectric and piezoelectric constants of the NKN film were not influenced by the OPP. However, the remnant polarization and coercive field decreased when the OPP exceeded 25.0 torr because of the low breakdown field and high leakage current. The NKN film annealed under air atmosphere exhibited a high leakage current density that decreased with increasing OPP because of the decreased number of oxygen vacancies. The minimum leakage current density of 3.7 x 10(-8) A cm(-2) at 0.3 MV cm(-1) was obtained for the NKN film annealed under an OPP of 25.0 torr. The leakage current increased when the OPP exceeded 25.0 torr because of the formation of oxygen interstitial ions. The leakage current of the Pt/NKN/Pt device was explained by Schottky emission. The obtained Schottky barrier height between the Pt electrode and NKN film was was similar to 1.24 eV. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.