Characterization of calcium-modified lead titanate thin films derived from a diol-based sol-gel process

Polycrystalline thin films of Ca-modified lead titanate (PCT) were deposited on Pt/SiO2/Si substrates using a diol-based sol-gel process. Calcium acetylacetonate hydrate was adopted as a starting material instead of the calcium acetate or calcium nitrate tetrahydrate used conventionally. By changing the Ca content (5-35 mol%) and heating temperature (500-800 degrees C), the influences of various processing parameters on the characteristics of thin films were studied. With the increase of the Ca content, the relative dielectric constant (epsilon(r)) of PCT thin film increased from 43 to 70 at the heating temperature of 700 degrees C. It was found that the coercive field (E-c) and the remanent polarization (P-r) decreased, but the pyroelectric coefficient (gamma) increased with an increase of Ca content. The results reveal that PCT thin film with a Ca content of 25 mol% exhibits the largest figures of merit for the voltage responsivity and the specific detectivity at a heating temperature of 700 degrees C.