The degradation (fatigue) of dielectric properties of ferroelectric Pb(ZrxTi1−x)O3 (PZT) and SrBi2Ta2O9 thin films during cycling was investigated. PZT and SrBi2Ta2O9 thin films were fabricated by metalorganic decomposition and pulsed laser deposition, respectively. Samples with electrodes of platinum (Pt) and ruthenium oxide (RuO2) were studied. The interfacial capacitance (if any) at the Pt/PZT, RuO2/PZT, and Pt/SrBi2Ta2O9 interfaces was determined from the thickness dependence of low‐field dielectric permittivity (er) measurements. It was observed that a low er layer existed at the Pt/PZT interface but not at the RuO2/PZT and Pt/SrBi2Ta2O9 interfaces. In the case of Pt/PZT, the capacitance of this interfacial layer decreases with increasing fatigue while the er of the bulk PZT film remains constant. This indicates that fatigue increases the interfacial layer thickness and/or decreases interfacial layer permittivity, but does not change the bulk properties. For the capacitors with RuO2/PZT/RuO2 and Pt/S...

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Electrode contacts on ferroelectric Pb(ZrxTi1−x)O3 and SrBi2Ta2O9 thin films and their influence on fatigue properties

Ferroelectric films of lead zirconate titanate (PZT) have been fabricated by rf planar magnetron sputtering. Films having a resistivity >106 Ω cm and a dielectric constant >800 at 300 K have been achieved using 100% oxygen as a sputtering medium, 10% excess PbO added to the target, and appropriate post‐deposition annealing. The sputtering rate is in the range 0.2–1.0 μm/h and varies with sputtering pressure and substrate temperature. Post‐deposition annealing affects both crystallinity and grain size, but incipient crystallization formed only in as‐grown films deposited at substrate temperatures >400 °C is essential for this process to be effective. A clear ferroelectric transition is observed at 350 °C, while the activation energy for dc conductivity of around 0.8 eV is consistent with bulk properties of PZT. The spontaneous polarization and coercive field measured from ferroelectric hysteresis loops is 20.75 μC/cm2 and 10 kV/cm, respectively. The optical transmittance of the films is determined by a Pb–Pb charge transfer band near 400 nm and this is a sensitive test of film stoichiometry.

rf planar magnetron sputtering and characterization of ferroelectric Pb(Zr,Ti)O3 films

A Maxwell–Wagner series capacitor model is proposed to explain anomalous dielectric properties of ferroelectric superlattices. The results of the model show that a superlattice consisting of normal ferroelectric layers separated by low-resistivity interfacial regions can account for most experimental results reported to date, namely: dielectric enhancement for certain stacking periodicities, giant permittivities, and temperature migration of dielectric maxima as a function of frequency. The predictions of the model are discussed and compared to our own experimental results from thin film superlattice capacitors made by pulsed-laser deposition.

Relaxor features in ferroelectric superlattices: A Maxwell–Wagner approach

Excimer laser ablative sputtering of sintered pellets of BaTiO3 has been used to epitaxially grow thin ∼1‐μm‐thick films of this material of LiF substrates.

Epitaxial growth of thin films of BaTiO3 using excimer laser ablation

Ferroelectric lead zirconate titanate thin films of morphotropic phase boundary composition were fabricated through the sol‐gel spin‐on technique to study the thickness dependence of electrical characteristics. At saturation, the films exhibited a dielectric constant of 1300, dissipation factor of 0.03, Curie temperature of 366 °C, remanent polarization of 36 μC/cm2, coercivity of around 30 kV/cm, and dielectric breakdown strength of over 1 MV/cm. The temperature dependence of permittivity showed an anomalous behavior with annealing temperature. The high temperature dielectric behavior of the films were distinguished by smeared and stunted dielectric maximum.

Thickness-dependent electrical characteristics of lead zirconate titanate thin films

Flash evaporated, ferroelectric, barium titanate films have been prepared in the thickness range 0.04-2.0 mu m. They consist of oriental tetragonal crystallites having dimensions comparable with film thickness. Thickness dependent permittivity and other dielectric properties are interpreted in terms of Schottky barriers at the film-electrode interface. Switching is observed in films as thin as 0.08 mu m and loops and current transients are surprisingly similar to those from bulk ceramics. Switchable spontaneous polarization values are as high as 20% of the bulk single crystal value.

J R Slack

Papers

Electrical properties of flash evaporated ferroelectric BaTiO3 thin films