Effect of finite domain-wall width on the domain structures of epitaxial ferroelectric and ferroelastic thin films

Abstract

A theory of domain (twin) structures, which takes into account the finite width of domain walls, is developed for epitaxial ferroelectric and ferroelastic thin films. The theory is based on the dislocation–disclination modeling of the sources of mechanical stresses in polydomain films. Calculations are performed for an orthorhombic or tetragonal film grown on a dissimilar orthorhombic, tetragonal, or cubic substrate. The case of a laminar 90° domain structure with the walls inclined at 45° to the film/substrate interface (c/a/c/a structure in tetragonal films) is considered. A simple dislocation–disclination model is constructed for the junctions of thick domain walls with the film/substrate interface. Using this model, the stress fields in the film and substrate and the associated elastic energy are evaluated. By minimizing the total energy of the material system at a fixed domain-wall width, the equilibrium geometric parameters of a periodic 90° domain structure are calculated. Then the range of stability of this structure in epitaxial films is determined as a function of the wall width. The mechanical restoring forces, which hinder cooperative translational vibrations of thick 90° walls near their equilibrium positions, are also calculated. On this basis, the domain-wall contributions to the dielectric and piezoelectric responses of prepolarized ferroelectric films are evaluated at different wall widths. Finally, the influence of the film straining by the substrate on the equilibrium domain-wall width is analyzed. An increase of the wall width in an epitaxial thin film relative to that in a bulk crystal is predicted.

Photochemistry on a polarisable semi-conductor: what do we understand today?

“…The formation of both 180 and 90°domain walls can minimise the depolarisation field by compensating for the surface charge in an unpoled ferroelectric ceramics, but only the formation of the 90°domain wall can release the elastic energy stored in the crystal. The motion and interaction of domain walls significantly affects the piezoelectric, mechanical and optical properties of the structure [39]. To be able to predict and control the domain wall kinetics, their physical and electrical properties need to be thoroughly understood and accurately determined.…”

Characterization of domain walls in BaTiO3 using simultaneous atomic force and piezo response force microscopy

“…As the size of the devices reduces to micro-and nano-scale, the motion and interaction of twin ͑domain͒ walls significantly influences the overall piezoelectric, optical, and mechanical response of the device. 6 In order to predict and control the phenomenological behavior of twin wall kinetics, their physical and electrical properties need to be accurately determined.Many of the current experimental techniques, including x-ray diffraction and high-resolution transmission electron microscopy ͑TEM͒ are capable of imaging domain walls, but are often unable to provide information about their polarization. 7,8 Also, since these techniques are based on diffraction principles, they only provide averaged information about the physical twin wall thickness.…”

“…As the size of the devices reduces to micro-and nano-scale, the motion and interaction of twin ͑domain͒ walls significantly influences the overall piezoelectric, optical, and mechanical response of the device. 6 In order to predict and control the phenomenological behavior of twin wall kinetics, their physical and electrical properties need to be accurately determined.…”

Microstructure of Ferroelectric Domains inBaTiO3Observed via X-Ray Microdiffraction

“…These features are not considered in the many papers that calculate domain wall profiles [13,14]. As the lattice is tetragonal, there is a lattice mismatch along the surface normal between neighboring c-axis and a-axis domains (Fig.…”