Phase formation and ferroelectricity of sol-gel derived (Pb, La)TiO3 thin films

Ferroelectric lead lanthanum titanate (PLT) thin films with various lanthanum concentration were fabricated by sol-gel spin-on process onto Pt/Ti/SiO2/Si substrates. We investigated the crystal structure, microstructure, and dielectric and ferroelectric properties of PLT films according to lanthanum doping concentration. The films annealed at 600 °C for 30 min have the single perovskite phase having only tetragonal or pseudocubic structure. The film microstructures were changed according to the doping concentration of La. The PLT films showed the typical polarization-electric field hysteresis loops and capacitance-voltage characteristics representing the ferroelectric switching property. The coercive field and remanent polarization decreased due to the phase transformation from ferroelectric to paraelectric phase with increasing La concentration. The effective dielectric constant and the leakage current density increased according to the increase of La content.