The techniques of x-ray diffraction, x-ray photoelectron spectroscopy (XPS), Auger analysis, and transmission and scanning transmission electron microscopy (TEM) have been applied to the analysis of thin films of Pb(Zr0.30Ti0.70)O3 (PZT30/70) deposited at low temperatures (510 °C) by a sol–gel process onto Pt/Ti electrodes on SiO2/Si 100 substrates. It is found that the platinum film is highly oriented with the [111] axis perpendicular to the substrate plane. The ferroelectric film tends to crystallize epitaxially upon this as columnar crystals. There are indications from the TEM of the existence of a second metallic phase at the interface between the platinum and the PZT30/70 film, which may be associated with its nucleation. The TEM shows the boundaries between the individual sol–gel layers, although the growing crystallites of the PZT30/70 propagate through these boundaries unhindered. The XPS and Auger analyses have shown that Pb penetrates through the Pt layer to the underlying Ti layer, even at the low crystallization temperatures used. There is also clear evidence for diffusion of the Zr and Ti prior to, or during the crystallization process, so that the Zr migrates to the surface of each sol–gel layer. The effects of using different crystallization processes on this compositional separation and the reasons for its occurrence are discussed, as are the possible effects upon macroscopically measured ferroelectric properties.
Thin films of lead scandium tantalate have been prepared by rf magnetron sputtering. The process involves two deposition steps. In the first, scandium tantalate is sputtered onto a heated sapphire substrate using a metal SciTa target. This film is annealed before replacing in the sputtering chamber where a film of lead oxide is sputtered onto the surface. The composite film is annealed, and after diffusion a pale yellow film of lead scandium tantalate Pb(Sc,,,Ta,,,)O, is formed. The films are close to 100% of the ferroelcctric perovskite phase with only 1% to 2% of the pyrochlore phase.Electrical characterisation has been performed to assess the Merit Figures of the films for use in IR detection. Permittivity. dielectric loss and field induced pyroelectricity have been measured against field and temperature. Film annealing conditions have been identified to produce films displaying sharp first order transitions. Under the bias field, very high values of the properties have been found, peak pcrmittivities of 8000, and induced pyroelectric coefficients of 6 X 10 ~' Clm'K. The merit for use in infrared detection indicates a performance equivalent to the conventional pyroelectric wafers prepared by the slicing. lapping and polishing of bulk ceramics.
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