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The design and evaluation experiments of a multibeam X-ray tomography optical system that can be used with synchrotron radiation from sources with a narrow energy bandwidth, i.e. undulator sources, are reported. It consists of silicon single crystals that diffract the incident X-rays to 27 beams, which are used to image a sample. The energy of the beams was aligned with an accuracy sufficient for use at typical undulator beamlines. Projection images of a test sample were collected and successfully reconstructed, showing the feasibility of a high-speed X-ray tomography instrument based on the optical system.

We present a combined experimental and theoretical study of the charge transport properties of TiH_{x}(x=1.6–2.0) epitaxial thin films. We found that the Hall coefficient of TiH_{x} strongly depends on hydrogen content and unit-cell volume: Nearly stoichiometric TiH_{x}(x≈2.0) films with large unit-cell volumes showed positive Hall coefficients at 4 K, whereas TiH_{x} samples with x

The recent developments in synchrotron optics, X-ray detectors, and data analysis algorithms have enhanced the capability of the surface X-ray diffraction technique. This technique has been used to clarify the atomic arrangement around surfaces in a non-contact and nondestructive manner. An overview of surface X-ray diffraction, from the historical development to recent topics, is presented. In the early stage of this technique, surface reconstructions of simple semiconductors or metals were studied. Currently, the surface or interface structures of complicated functional materials are examined with sub-Å resolution. As examples, the surface structure determination of organic semiconductors and of a one-dimensional structure on silicon are presented. A new frontier is time-resolved interfacial structure analysis. A recent observation of the structure and dynamics of the electric double layer of ionic liquids, and an investigation of the structural evolution in the wettability transition on a TiO2 surface that utilizes a newly designed time-resolved surface diffractometer, are presented. [ABSTRACT FROM AUTHOR]

The surface structure of the strained Si(001) (thickness of 20 nm) on Si1-xGex (x = 0.1, 0.2, and 0.3) was studied by low-energy electron diffraction (LEED). LEED intensity-energy spectra of the 2 x 1 reconstructed clean surfaces showed a systematic change that indicates the lattice contraction along the [001] direction remains even at the surfaces. The atomic structures were quantitatively determined, and they were compared with the unstrained pristine Si. The differences in the atomic position almost follow the difference in the bulk lattice constant determined by X-ray diffraction measurements. The results indicate that the strain produced at the Si/Si1-xGex interface remains unchanged up to the surface layer. [ABSTRACT FROM AUTHOR]

The surface structure of the strained Si(001) (thickness of 20 nm) on Si1-xGex (x = 0.1, 0.2, and 0.3) was studied by low-energy electron diffraction (LEED). LEED intensity-energy spectra of the 2 x 1 reconstructed clean surfaces showed a systematic change that indicates the lattice contraction along the [001] direction remains even at the surfaces. The atomic structures were quantitatively determined, and they were compared with the unstrained pristine Si. The differences in the atomic position almost follow the difference in the bulk lattice constant determined by X-ray diffraction measurements. The results indicate that the strain produced at the Si/Si1-xGex interface remains unchanged up to the surface layer. [ABSTRACT FROM AUTHOR]

The atomic structure of the Si(111)-(5 × 2)-Au surface, a periodic gold chain on the silicon surface, has been a long-debated issue in surface science. The recent three candidates, the so-called Erwin-Barke-Himpsel (EBH) model [S. C. Erwin, I. Barke, and F. J. Himpsel, Phys. Rev. B 80, 155409 (2009)], the Abukawa- Nishigaya (AN) model [T. Abukawa and Y. Nishigaya, Phys. Rev. Lett. 110, 036102 (2013)], and the Kwon-Kang (KK) model [S. G. Kwon and M. H. Kang, Phys. Rev. Lett. 113, 086101 (2014)] that has one additional Au atom than the EBH model are tested by surface x-ray diffraction data. A two-dimensional Patterson map constructed from the in-plane diffraction intensities rejects the AN model and prefers the KK model over the EBH model. On the basis of the arrangement of Au obtained from the Patterson map, all the reconstructed Si atoms, such as the so-called honeycomb chain structure, are directly imaged out by utilizing a holographic method. The KK model reproduces out-of-plane diffraction data as well. [ABSTRACT FROM AUTHOR]

Atomic structure and electronic transport properties of Cu-doped topological insulator Bi2Se3 (CuxBi2Se3) films were investigated by surface x-ray diffraction and magnetotransport measurements. We revealed that by depositing Cu on the pristine Bi2Se3 films at room temperature the van der Waals gap between the quintuple layers was expanded to intercalate the Cu atoms. The gap size became maximum in the doping range of 0.12 ⩽ x ⩽ 0.35, in the same manner as the bulk superconducting CuxBi2Se3 crystal. The optimally doped (x = 0.12) film was in n type and the carrier concentration was on the order of 1020 cm-3; that agrees with the superconducting bulk crystals and is one order of magnitude larger than the pristine Bi2Se3 films. The film exhibited the weak antilocalization behavior as observed in the pristine films, indicating that the strong spin-orbit coupling is maintained against the Cu doping. The room-temperature doping did not lead to the possible superconducting transition down to 0.8 K, suggesting that in addition to the electron doping, another feature, that may exist in the inhomogeneous bulk CuxBi2Se3 crystals synthesized at much higher temperatures, is responsible for the superconductivity. [ABSTRACT FROM AUTHOR]

We developed a multi-beam X-ray imaging detector, consisting of four scintillator screens connected by a branched optical fiber bundle with a CMOS camera. By using the detector and a multi-beam imaging optics with silicon single crystalline blades designed for a white synchrotron radiation source, we successfully demonstrated multi-beam X-ray imaging with an exposure time of 1 ms. The long and flexible optical fiber bundle used for the detector enables us to realize high-speed multi-beam X-ray imaging with high flexibility at a relatively low cost. [ABSTRACT FROM AUTHOR]

Sn atomic layers attract considerable interest owing to their spin-related physical properties caused by their strong spin–orbit interactions. We performed Sn intercalation into the graphene/SiC(0001) interface and found a new type of Sn atomic layer. Sn atoms occupy on-top sites of Si-terminated SiC(0001) with in-plane Sn–Sn bondings, resulting in a triangular lattice. Angle-resolved photoemission spectroscopy revealed characteristic dispersions at and points, which agreed well with density functional theory calculations. The Sn triangular lattice atomic layer at the interface showed no oxidation upon exposure to air, which is useful for characterization and device fabrication ex situ. [ABSTRACT FROM AUTHOR]

We investigate the atomic structure of the tungsten ditelluride (WTe2) surface by using low-energy electron diffraction (LEED), scanning tunneling microscopy, and density functional theory (DFT) calculations. From the LEED and DFT analyses, we find small but non-negligible surface relaxation that gradually decays in an oscillatory manner inside the first WTe2 layer. In addition, the DFT calculations reveal that the Fermi surface topology is sensitive to this relaxation. These results are helpful for understanding the exotic properties of WTe2. [ABSTRACT FROM AUTHOR]

The structure of multilayer silicene formed on Ag(111) films was studied by low-energy electron diffraction. It turned out that the experimental data cannot be explained by proposed models that only consider buckling of silicon atoms. We have rather found that multilayer silicene on Ag(111) is actually a thin film of bulklike silicon terminated with the Si(111)√3×√3-Ag surface. The results are compared to previous works and clearly show the importance to properly understand the structure of the system when discussing its electronic properties. [ABSTRACT FROM AUTHOR]

A totally anisotropic peculiar Rashba-Bychkov (RB) splitting of electronic bands was found on the Tl/Si(110)-(1×1) surface with C1h symmetry by angle- and spin-resolved photoelectron spectroscopy and first-principles theoretical calculation. The constant energy contour of the upper branch of the RB split band has a warped elliptical shape centered at a k point located between Γ and the edge of the surface Brillouin zone, i.e., at a point without time-reversal symmetry. The spin-polarization vector of this state is in-plane and points almost the same direction along the whole elliptic contour. This novel nonvortical RB spin structure is confirmed as a general phenomenon originating from the C1h symmetry of the surface. [ABSTRACT FROM AUTHOR]