Crystallinity dependence of resistance switching in La0.7Ca0.3MnO3 films grown by pulsed laser deposition

Abstract

Resistance switching property induced by pulsed electric-field in metal-oxide-metal sandwiches attracted much interest due to its potential application in nonvolatile memory devices. In this paper, the influence of the crystallinity of La0.7Ca0.3MnO3 (LCMO) film on the resistance switching of Ag-LCMO-Pt sandwiches has been investigated. LCMO films were grown on Pt/Ti/SiO2/Si substrates using pulsed laser deposition technique at different substrate temperatures. The crystallinity of LCMO films were characterized by x-ray diffraction, atomic force microscopy, transmission electron microscopy, and x-ray photoelectron microscopy. The results show that the crystallinity of LCMO films changed from the amorphous phase to (200) oriented nanocrystalline grains by varying the deposition temperature from 500 to 700 °C. The amorphous LCMO films were crystallized through rapid thermal annealing process under oxygen atmosphere. The coexistence of crystalline grains and grain boundaries results in the inhomogenous conductivity in LCMO films. Current-voltage characteristics and pulsed bias measurements indicate that nonvolatile resistance switching only takes place in the crystallized LCMO films and the resistance change ratio depends on the grain size of LCMO films. These results were described as the electric field induced oxygen vacancy annihilation/generation combined with the change of electron/hole trap density at the local interface between the Ag electrode and the crystalline grains in the LCMO film.