Abstract
The surface deformation and atomic-level distortions associated withcrystal structural matching at ferroelectric inversion domain wallsare investigated in periodically poled potassium titanyl phosphate(KTP) crystals. A deformation, of the order of 10−8 min scale and having the periodicity of the domains, is observed at the surfaces byoptical interferometry. It is discussed in terms of the piezoelectric effect. Thematching of the crystal structures at the domain walls is studied by combining thehard x-ray Fresnel phase-imaging technique with Bragg diffraction imagingmethods (‘Bragg–Fresnel imaging’) and using synchrotron radiation. Quantitativeanalysis of the contrast of the Bragg–Fresnel images recorded as a function of thepropagation distance is demonstrated to allow the determination of how thedomains are matched at the atomic (unit cell) level, even though the spatialresolution of the images is on the scale of micrometres. The atom P(1) isdetermined as the linking atom for connecting the inversion domains across thewall in KTP crystals for domain walls forced by electric-field processing to beparallel to (100). In addition to this, it is shown that a shift of 1/2(a + b)between atoms in the original and inverted structures is introduced as a result ofthe domain inversion operation.
Published Version
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