Influence of Stoichiometric Ratio and Mn-Doping on the Surface Morphology and Dielectric Properties of Perovskite (La,Sr)FeO3 Films

Lanthanum strontium ferrite (La_1−x Sr _x FeO₃, x = 0.1, 0.3, 0.5, 0.7) (LSF) films were prepared on platinized/silica/silicon (Pt/SiO₂/Si) substrates by a sol–gel method. The crystallization, surface morphology and dielectric properties of the LSF films have been studied. Among the samples, La_0.5Sr_0.5FeO₃ thin film have the most homogeneous, smooth surface and the best dielectric properties (ε _r  = 2881.58, tanδ = 1.20) at the frequency of 1 kHz. Mn-doping (y) in La_0.5Sr_0.5FeO₃ further improves the dielectric properties (ε _r  = 2922.91, tanδ = 1.11) of the film. Both ε _r and tanδ values of the Mn-doped (y = 0.02) La_0.5Sr_0.5FeO₃ films decreases with increasing the frequency. The biggest ε _r value is 3238.18 at the frequence of 0.02 kHz.