Extrinsic conductivity in ferroelectric PZT film capacitors made by laser ablation deposition

Abstract

Electrical properties of ferroelectric lead–zirconate–titanate (PZT) thin-film devices are affected by the composition and structure of the PZT film itself and also by the electrode material and the interface between the electrode and ceramics. In this paper we consider capacitor structures with platinum thin-film electrodes (Pt/PZT/Pt/substrate) which typically have very high dc resistivity, but suffer from the polarization fatigue due to the high stress and oxygen vacancy build-up in the interface between the electrode and ceramic thin film. Both platinum electrodes and Nd-modified PZT (PNZT) thin films were fabricated by the pulsed laser-ablation deposition and post-annealing heat treatments. The behaviour of the conductivity in the PNZT thin-film capacitors was studied as a function of temperature and electric field. Low-field resistivities of the order of 1012 Ωcm were measured for the films at room temperature. Some differences were found in the current–voltage characteristics between capacitor structures made on MgO(100) and oxidized silicon(100) substrates, respectively. Assuming the Poole–Frenkel emission mechanism for the conduction, the activation energies of conduction were obtained to be between 0.15 and 0.18 eV.