No abstract

No abstract

Ferroelectric lead zirconium titanate [Pb (ZrxTi1−x)O3] (PZT) thin films have been synthesized by using an automated laser ablation deposition technique with a capability for layer-by-layer or simultaneous deposition of elemental film constituents. The technique is suitable for producing multicomponent and/or multilayered thin films with controlled stoichiometry, such as high-temperature superconductor, ferroelectric, and electro-optic thin films. PZT films were synthesized on MgO (100) by either sequential deposition of layers of ZrO2, TiO2, and PbO, produced by laser ablation of ZrO2, TiO2, and PbO targets, or by simultaneous deposition of all species from ablation of stoichiometric or PbO-rich PZT targets. Films were deposited at 200 °C and subsequently annealed at 600 °C for different periods of time. The orientation, microstructure, surface topography, and composition of the films were characterized by x-ray diffraction, transmission electron microscopy, scanning electron microscopy, and Rutherford backscattering spectrometry, respectively. As-deposited layer films consists of highly oriented (001) PbO layers, from which highly oriented (110) PZT films are produced after postdeposition annealing. On the other hand, laser ablation of bulk PZT targets yields amorphous as-deposited films, which evolve into highly oriented (100) PZT films after postdeposition annealing. Preliminary electrical characterization of the PZT films included polarization hysteresis, fatigue, conductivity (ac and dc), and capacitance versus voltage measurements. From the initial electrical measurements, it appears that the remnant polarization of the layered PZT films is similar to that of the films produced by laser ablation of bulk PZT targets.

Electron emission from ferroelectric thin films (≤1 μm thick) is demonstrated. In addition, electron energy distributions have been measured using an Auger electron spectrometer. The electron emission measurements were performed using ferroelectric cathodes based on this Pb(Zr0.53Ti0.47)O3 (PZT) films and 80–110 μm Pb0.93La0.07(Z0.53Ti0.47)O3 (PLZT) layered capacitors with Pt top and bottom electrodes. Current densities in the range of 0.5–1.5 mA/cm2 were measured from the PLZT cathodes excited with 100–400 V pulses, which produced electrons of about 265 eV with a narrow energy distribution (full width at half-maximum of about 30 eV). On the other hand, current densities in the range 0.07–0.15 μA/cm2 were measured for thin film PZT-based cathodes excited with pulses in the range 10–40 V. The initial results suggest that the electron emission current may depend, among other factors, on the thickness of the ferroelectric layer, the applied excitation voltage, and the interval between the polarizing and switching pulses.