Internal field and self-polarization in sol-gel-derived lead zirconate titanate films

An internal electric field is induced in a sol-gel-derived lead zirconate titanate (PZT) film of thickness 2 μm after the rf-sputtering deposition of the top electrode and this is exhibited as a shift of the P-E loop towards the positive side of the electric field axis. The direction of the internal field is towards the bottom electrode. As the discharge power used for the sputtering decreases, the internal field increases. We suggest that the internal field is induced by the high-energy ion bombardment on the film surface during the rf-sputtering process. Due to the occurrence of the internal field, the as-prepared PZT film becomes self-polarized at a high deposition temperature of 150°C, thus showing a non-zero pyroelectric coefficient at room temperature. As the internal field increases, the observed pyroelectric coefficient increases and has a large value of 230 μC/m2K for an as-prepared PZT film with an internal field of 40 kV/cm.