Volume 95, Issue 11, 01 June 2004
Index of content:
- DIELECTRICS AND FERROELECTRICITY (PACS 77)
Ferroelectric domain structures in epitaxial thin films: Electron microscopy and phase-field simulations95(2004); http://dx.doi.org/10.1063/1.1707211View Description Hide Description
Ferroelectric domain structures of epitaxialfilms, investigated using both transmission electron microscopy and phase-field simulations, are reported. Experiment and numerical simulation both reveal that the domain structures consist of irregularly shaped domains with curveddomain walls. It is shown that the elastic contribution to domain structures can be neglected in due to its small ferroelastic distortion, less than 0.0018%. Two-beam dark-field imaging using reflections unique to domains of each of the two 90° polarization axes reveal the domain structure. Phase-field simulation is based on the elastic and electrostatic solutions obtained for thin films under different mechanical and electric boundary conditions. The effects of ferroelastic distortion and dielectric constant on ferroelectric domains are systematically analyzed. It is demonstrated that electrostatic interactions which favor straight domain walls are not sufficient to overcome the domain wall energy which favors curved domains in
Dielectric properties of lead lanthanum zirconate stanate titanate antiferroelectric thin films prepared by pulsed laser deposition95(2004); http://dx.doi.org/10.1063/1.1715136View Description Hide Description
Leadlanthanum zirconate stanate titanate (PLZST) thin films of approximately 200 nm in thickness were deposited on Pt-buffered silicon substrates using pulsed laser deposition method. The samples were prepared under different substrate temperatures but with the same oxygen partial pressure of 0.2 mbar and laser fluence of approximately 4 J/cm2. We found that the Pb loss during the deposition process plays an important role in the formation of perovskite phase. Postdeposition annealing under different oxygen pressure, ranging from 0.2 mbar to atmospheric oxygen pressure but for the same annealing duration (15 min), was carried out in order to clarify the effects of the annealing ambient, from the viewpoint of crystallographic structure as well as electrical and dielectric properties. The physical origin is discussed.
95(2004); http://dx.doi.org/10.1063/1.1703830View Description Hide Description
The domain structure of single crystals with composition in the range of the morphotropic phase boundary (MPB) was studied. Based on the analysis of spontaneous strain compatibility and charge of domain walls, we have established the permissible domain arrangements for the ferroelectric phases of different symmetries, which are expected to occur in the range of the MPB. Examination of (001)-oriented unpoled and electrically poled (along the  direction) crystal plates in a polarizing microscope reveals a monophase state with the domain structure compatible with the structure theoretically predicted for the monoclinic phase (space group Pm), which was recently discovered in the compositions close to the MPB by x-ray and neutron diffraction studies. In the unpoled crystal, the 180° walls between the domains whose spontaneous polarization vectors are parallel to the plane of the crystal plate (i.e., a-domains) are observed. The domain structure of the poled crystal is predominantly composed of crystallographically prominent walls parallel to (001) (i.e., the plane of the crystal plate) and inclined S walls parallel to  or direction. In poled and unpoled samples, an optical rotatory polarization effect is found, which is related to the inhomogeneity of the sample resulting from the mixture of domains.