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Publisher: Copenhagen : Munksgaard × WGL Institute: IKZ ×

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    Scanning X-ray nanodiffraction from ferroelectric domains in strained K0.75Na0.25NbO3 epitaxial films grown on (110) TbScO3
    (Copenhagen : Munksgaard, 2017) Schmidbauer, Martin; Hanke, Michael; Kwasniewski, Albert; Braun, Dorothee; von Helden, Leonard; Feldt, Christoph; Leake, Steven John; Schwarzkopf, Jutta
    Scanning X-ray nanodiffraction on a highly periodic ferroelectric domain pattern of a strained K0.75Na0.25NbO3 epitaxial layer has been performed by using a focused X-ray beam of about 100 14;nm probe size. A 90°-rotated domain variant which is aligned along [1 2]TSO has been found in addition to the predominant domain variant where the domains are aligned along the [12]TSO direction of the underlying (110) TbScO3 (TSO) orthorhombic substrate. Owing to the larger elastic strain energy density, the 90°-rotated domains appear with significantly reduced probability. Furthermore, the 90°-rotated variant shows a larger vertical lattice spacing than the 0°-rotated domain variant. Calculations based on linear elasticity theory substantiate that this difference is caused by the elastic anisotropy of the K0.75Na0.25NbO3 epitaxial layer.
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    Dynamical X-ray diffraction imaging of voids in dislocation-free high-purity germanium single crystals
    (Copenhagen : Munksgaard, 2020) Gradwohl, Kevin-P.; Danilewsky, Andreas N.; Roder, Melissa; Schmidbauer, Martin; Janicskó-Csáthy, József; Gybin, Alexander; Abrosimov, Nikolay; Sumathi, R. Radhakrishnan
    White-beam X-ray topography has been performed to provide direct evidence of micro-voids in dislocation-free high-purity germanium single crystals. The voids are visible because of a dynamical diffraction contrast. It is shown that voids occur only in dislocation-free parts of the crystal and do not show up in regions with homogeneous and moderate dislocation density. It is further suggested that the voids originate from clustering of vacancies during the growth process. A general method is proposed to verify the presence of voids for any crystalline material of high structural perfection.