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- ItemImpact of Electrical Current on Single GaAs Nanowire Structure(Weinheim : Wiley-VCH, 2021) Bahrami, Danial; AlHassan, Ali; Davtyan, Arman; Zhe, Ren; Anjum, Taseer; Herranz, Jesús; Geelhaar, Lutz; Novikov, Dmitri V.; Timm, Rainer; Pietsch, UllrichThe impact of electrical current on the structure of single free-standing Be-doped GaAs nanowires grown on a Si 111 substrate is investigated. Single nanowires have been structurally analyzed by X-ray nanodiffraction using synchrotron radiation before and after the application of an electrical current. The conductivity measurements on single nanowires in their as-grown geometry have been realized via W-probes installed inside a dual-beam focused ion beam/scanning electron microscopy chamber. Comparing reciprocal space maps of the 111 Bragg reflection, extracted perpendicular to the nanowire growth axis before and after the conductivity measurement, the structural impact of the electrical current is evidenced, including deformation of the hexagonal nanowire cross section, tilting, and bending with respect to the substrate normal. For electrical current densities below 30 A mm−2, the induced changes in the reciprocal space maps are negligible. However, for a current density of 347 A mm−2, the diffraction pattern is completely distorted. The mean cross section of the illuminated nanowire volume is reconstructed from the reciprocal space maps before and after the application of electrical current. Interestingly, the elongation of two pairs of opposing side facets accompanied by shrinkage of the third pair of facets is found. The variations in the nanowire diameter, as well as their tilt and bending, are confirmed by scanning electron microscopy. To explain these findings, material melting due to Joule heating during voltage/current application accompanied by anisotropic deformations induced by the W-probe is suggested.
- ItemScanning 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, JuttaScanning 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.
- ItemScanning X-ray nanodiffraction: From the experimental approach towards spatially resolved scattering simulations(London : BioMed Central, 2012) Dubslaff, Martin; Hanke, Michael; Patommel, Jens; Hoppe, Robert; Schroer, Christian G.; Schöder, Sebastian; Burghammer, ManfredAn enhancement on the method of X-ray diffraction simulations for applications using nanofocused hard X-ray beams is presented. We combine finite element method, kinematical scattering calculations, and a spot profile of the X-ray beam to simulate the diffraction of definite parts of semiconductor nanostructures. The spot profile could be acquired experimentally by X-ray ptychography. Simulation results are discussed and compared with corresponding X-ray nanodiffraction experiments on single SiGe dots and dot molecules.