Using grazing-incidence x-ray diffraction, the p(2x2) surface structures of the single crystal NiO(111) and a 5 monolayer thick NiO(111) film on Au(111) were both shown to exhibit locally the theoretically predicted octopolar reconstruction, with some important differences. The single crystal exhibits a single Ni termination with double steps. The thin film exhibits both possible terminations (O and Ni) and single steps. These surfaces were found to be nonreactive with respect to hydroxylation.

The achievement of high growth rates in YBa 2 Cu 3 O 7 epitaxial high-temperature superconducting films has become strategic to enable high-throughput manufacturing of long length coated conductors for energy and large magnet applications. We report on a transient liquid assisted growth process capable of achieving ultrafast growth rates (100 nm s −1) and high critical current densities (5 MA cm −2 at 77 K). This is based on the kinetic preference of Ba-Cu-O to form transient liquids prior to crystalline thermodynamic equilibrium phases, and as such is a non-equilibrium approach. The transient liquid-assisted growth process is combined with chemical solution deposition, proposing a scalable method for superconducting tapes manufacturing. Additionally, using colloidal solutions, the growth process is extended towards fabrication of nanocomposite films for enhanced superconducting properties at high magnetic fields. Fast acquisition in situ synchrotron X-ray diffraction and high resolution scanning transmission electron microscopy (STEM) become crucial measurements in disentangling key aspects of the growth process.

X-ray microdiffraction is used to analyze strain and composition profiles in individual micron-sized SiGe islands grown by liquid phase epitaxy on Si͑001͒ substrates. From the variation of the scattered intensity while scanning the sample through a focused x-ray beam of few m size, an image of the island distribution on the sample is created. Using this image it is possible to identify particular islands and select them for analysis one by one. The Ge and strain distribution within each island is obtained from the intensity distribution in reciprocal space measured for several individual islands. The detailed shape of each measured island is obtained from scanning electron microscopy. Apart from truncated pyramid-shaped islands, we detect and characterize a small number of flat islands and show that they represent an earlier growth stage of the pyramidal shaped ones. This analysis is only possible by combining the local x-ray diffraction with scanning electron microscopy on exactly the same islands.

The perfomance of hematite and Ti-substituted hematite nanorods as photoanodes for solar water splitting was quantitavely evaluated from photoelectrochemical point of view. The nanostructure, morphology and chemical / electronic structure...

Van der Waals layered GeTe/Sb Te superlattices (SLs) have demonstrated outstanding performances for use in resistive memories in so-called interfacial phase-change memory (iPCM) devices. GeTe/Sb Te SLs are made by periodically stacking ultrathin GeTe and Sb Te crystalline layers. The mechanism of the resistance change in iPCM devices is still highly debated. Recent experimental studies on SLs grown by molecular beam epitaxy or pulsed laser deposition indicate that the local structure does not correspond to any of the previously proposed structural models. Here, a new insight is given into the complex structure of prototypical GeTe/Sb Te SLs deposited by magnetron sputtering, which is the used industrial technique for SL growth in iPCM devices. X-ray diffraction analysis shows that the structural quality of the SL depends critically on its stoichiometry. Moreover, high-angle annular dark-field-scanning transmission electron microscopy analysis of the local atomic order in a perfectly stoichiometric SL reveals the absence of GeTe layers, and that Ge atoms intermix with Sb atoms in, for instance, Ge Sb Te blocks. This result shows that an alternative structural model is required to explain the origin of the electrical contrast and the nature of the resistive switching mechanism observed in iPCM devices.

Crystals with cylindrical symmetry, not existing in nature, are mimicked by the roll-up of single-crystalline and highly strained semiconductor bilayers. Exploiting this, the local structure of such individual rolled-up nanotubes is locally probed and quantified nondestructively by x-ray microbeam diffraction. A comparison to simulations, based on the minimization of the elastic energy, allows us to determine layer thicknesses and lattice parameter distributions within the strongly curved bilayers.

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We depict the use of x-ray diffraction as a tool to directly probe the strain status in rolled-up semiconductor tubes. By employing continuum elasticity theory and a simple model, we are able to simulate quantitatively the strain relaxation in perfect crystalline III-V semiconductor bilayers and multilayers as well as in rolled-up layers with dislocations. The reduction in the local elastic energy is evaluated for each case. Limitations of the technique and theoretical model are discussed in detail. ͑1͒where the subscripts x, y, and z indicate directions that are parallel to the main crystallographic axes. The dependence of the elastic constants on the local composition at the position r is explicitly shown in Eq. ͑1͒ for C 11 and C 12 and implicit PHYSICAL REVIEW B 79, 035301 ͑2009͒