Thinned ferroelectric crystals and ceramics

In interpreting the properties of thin film ferroelectrics, it is useful to have baseline electrical property data on thinned single crystals and ceramics over the same thickness range. In this study, the properties of thinned BaTiO₃ have been investigated. To examine the quality of the surfaces produced, spectroscopic ellipsometry (SE) was used. This technique is capable of depth profiling the optical properties of dielectric materials with a resolution in the Angstrom range. It was found that both polishing and chemical etching lead to disturbed regions on the sample surface due to mechanical damage, residual roughness, and chemically inhomogeneous layers. As expected in the case of mechanical polishing, the depth of the damaged layer increased with grit size. For both polishing and etching it is possible to prepare surfaces with less than approx. 200 angstrom of optically - detectable damage. It was shown that for unelectroded c-domain BaTiO₃, irreversible changes in the SE spectra as a function of temperature occur if measurements are made immediately after poling. It was also shown that if a gradient in the polarization exists at the surface of the sample, it appears to be confined to a layer on the order of 100 angstrom thick.