Heterostructure and compositional depth profile of low-temperature processed lead titanate-based ferroelectric thin films prepared by photochemical solution deposition

The heterostructure and compositional depth profile of low-temperature processed (Pb0.76Ca0.24)TiO3 (PCT24) ferroelectric thin films have been studied in the present work. The films were Prepared by ultraviolet (UV) sol-gel photoannealing (also called photochemical solution deposition, PCSD) onto platinized silicon substrates and crystallized at 450 degrees C in air and oxygen atmospheres. Despite using such a low temperature, analysis carried out by X-ray photoelectron spectroscopy (XPS) revealed the total lack of organic rests within the bulk film. Complementary information about the heterostructure of the films was also obtained by Rutherford backscattering spectroscopy (RBS). Both analytical techniques detected the presence of a lead gradient in the films, together with small fluctuations on the concentration of this element along the bulk film. The RBS study also showed that the films of this work develop a PtxPb interface between the ferroelectric layer and the Pt bottom electrode. The thickness of this interlayer is much lower than that of the interface formed in PCT24 films prepared at higher temperatures (650 degrees C without UV irradiation (conventional CSD). On the other hand, the low processing temperature here used minimizes the lead loss by volatilization, as deduced from the RBS simulated spectra of the films. Thus, the lead excess incorporated in the precursor solution remains in the films after the crystallization treatment. This result would suppose a significant advance toward the environmentally low-impact processing of lead-containing ferroelectric films with applications in electrical and electronic components (e.g., piezoelectric devices).