Thickness dependence of electrical properties in (0 0 1) oriented lead zirconate titanate films by laser ablation

Highly (0 0 1)-oriented Pb(Zr0.52Ti0.48)O3 (PZT) thin films with LaNiO3 (LNO) bottom electrodes have been fabricated on amorphous TiN buffered Si substrates by pulsed laser deposition. The polarization–electric field (P–E) hysteresis of the deposited PZT films with different thickness ranging from 25 to 850 nm was measured. Results showed that the coercive field increases with the film thickness scaling down. No P–E loops could be obtained for the film of thickness of 25 nm. The deterioration of ferroelectric property in the thinnest film was attributed to extrinsic effect other than intrinsic size effect. Current–voltage (I–V) characteristics measurement showed the increase in leakage current of the PZT films with the decrease in the thickness of the films under the same bias voltage. At a high field regime, the leakage current of the PZT films of 25 nm thickness remained unchanged with increasing applied voltage. A totally depleted back-to-back Shottky barrier model was used to explain the effect of electrode interfaces on leakage current in the PZT films. It is believed that ferroelectric/electrode interfaces play an important role in the electrical properties of ferroelectric thin films with thickness at nanometer level.