Effects of the alkaline solution concentration and deposition temperature on film thickness, crystal structure and ferroelectric properties of epitaxial PbTiO3 films grown by hydrothermal method

Effects of alkaline solution concentration and deposition temperature on the film thickness, crystal structure, and ferroelectric properties were investigated for epitaxial PbTiO3 films grown on (100)cSrRuO3//(100)SrTiO3 substrates by hydrothermal method. The (001)-oriented PbTiO3 films were grown at 150 °C with KOH solution concentrations from 1 to 10 mol/L. Potassium incorporation was not detected for the films deposited at 10 mol/L. c-axis lattice parameters continuously decreased with the increase in the KOH solution concentration. A 250-nm-thick film grown at 8 mol/L showed lattice parameters expected from bulk PbTiO3 and showed good ferroelectric properties; a remanent polarization and an average coercive field (average of plus and minus coercive field, Ec) of about 74 µC/cm2 and about 173 kV/cm, respectively. Film thickness was successfully increased by raising the deposition temperature to 200 °C at 8 mol/L. Lattice parameters were almost unchanged by changing the deposition temperature. The relationship between Ec and the film thickness (t) agreed with the semiempirical scaling law (Ec ∼ t−2/3). These data suggest that the increase in the deposition temperature is one of the effective ways to deposit thick PbTiO3 films.