Synthesis and characterization of nanoporous strontium-doped lanthanum cobaltite thin film using metal organic chemical solution deposition

Abstract

By employing strontium as a dopant of lanthanum cobaltite (LaCoO3), strontium-doped lanthanum cobaltite (La1−xSrxCoO3−δ, LSC) thin film was fabricated using a metal organic chemical solution deposition (MOCSD) method. Lanthanum nitrate hexahydrate [La(NO3)36H2O], strontium acetate [Sr(CH3COO)2], and cobalt acetate tetrahydrate [Co(CH3COO)24H2O] were used as precursors. The coating process was performed through a spin coating method on a substrate, which were then heat treated under various temperature conditions. Electrical properties, microstructures, and crystalline structures with respect to sintering temperature were analyzed. According to these analyses, the change in surface morphology, phase shift, and conductive properties were closely related, which could explain their respective behaviors. Furthermore, sintered strontium-doped lanthanum perovskite oxides showed various conductivities according to the amount of dopant. With the molar ratio of strontium that is stoichiometrically equivalent to lanthanum (La0.5Sr0.5CoO3−δ) thin film showed the best conductivity in the sintering temperature range of 650–700°C, with perovskite phases formed at this temperature condition. As the electrically conductive properties of the thin film are a function of thickness, the films were coated several times to a thickness of approximately 300nm, with the lowest resistivity (approximately 9.06×10−4Ωcm) observed at the optimized sintering temperature and solution composition.