Fabrication of cerium-doped LaNiO_3 thin films on LaAlO_3 (100) substrate by pulsed laser deposition

摘要

In this study we report the fabrication of La_(1-x)Ce_xNiO_3 (0 ≤ x ≤ 0.4) thin films on a LaAlO_3 (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-x)Ce_xNiO_3 thin films gives clear indications of significant electron-lattice interactions present for compositions close to the transition.