Fabrication of cerium-doped LaNiO₃ thin films on LaAlO₃ (100) substrate by pulsed laser deposition

Abstract

In this study we report the fabrication of La_1−xCe_xNiO₃ (0≤x≤0.4) thin films on a LaAlO₃ (100) substrate by pulsed laser deposition where the cerium ions are believed to be in the Ce (IV) oxidation state. At low Ce concentrations, the films grow in the (100) direction with a pseudocubic structure and above x~0.3, they exhibit a change in the crystal symmetry. Core-level photoelectron spectroscopic studies of the thin films deposited have shown that the cerium exists in the +4 oxidation state. Correspondingly, the nickel exhibits mixed valency in these thin films. Conductivity of this highly metallic system progressively decreases as more and more Ce is doped. In the range 0.3 < x < 0.4, the system undergoes a transition from metallic to semiconducting behavior. The electrical nature of La_1−xCe_xNiO₃ thin films gives clear indications of significant electron-lattice interactions present for compositions close to the transition.