Shiro Entani

Atomic and electronic structure of an unreconstructed polar MgO(111) thin film on Ag(111)

Atomic and electronic structures of a polar surface of MgO formed on Ag(111) was investigated by using reflection high-energy electron-diffraction, Auger-electron spectroscopy, electron energy-loss spectroscopy (EELS), and ultraviolet photoemission spectroscopy (UPS). A rather flat unreconstructed polar MgO(111)

Growth of nanographite on Pt(111) and its edge state

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Polar surface engineering in ultrathin MgO(111)∕Ag(111) : Possibility of a metal-insulator transition and magnetism

surface could be grown by alternate adsorption of Mg and

One-dimensional ordered structure of α-sexithienyl on Cu(110)

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Metal-induced gap states in epitaxial organic-insulator/metal interfaces

on Ag(111). The stability of the MgO(111) surface was discussed in terms of interaction between Ag and Mg atoms at the interface and charge state of the surface atoms. EELS of this surface did not show a band-gap region, and finite density of states appeared at the Fermi level in UPS. These results suggest that a polar MgO(111) surface was not an insulating surface but a semiconducting or metallic surface.

Interfacial energy calculation of bcc/fcc interface

The nanographite grains, the diameter of which was around 5nm, were formed on Pt(111) by exposing the Pt(111) substrate to benzene gas at room temperature and annealing it up to 850K. The increase of relative number of edge atoms enabled the observation of edge-derived electronic states. The measurement of ultraviolet photoelectron spectroscopy and near edge x-ray absorption fine structure on the nanographite revealed the appearance of the edge state located at the Fermi level.

Atomic and electronic structure of CsBr film grown on LiF and KBr(0 0 1)

A recent report [Kiguchi {it et al.}, Phys. Rev. B {bf 68}, 115402 (2003)] that the (111) surface of 5 MgO layers grown epitaxially on Ag(111) becomes metallic to reduce the electric dipole moment raises a question of what will happen when we have fewer MgO layers. Here we have revealed, first experimentally with electron energy-loss spectroscopy, that MgO(111) remains metallic even when one-layer thick, and theoretically with the density functional theory that the metallization should depend on the nature of the substrate. We further show, with a spin-density functional calculation, that a ferromagnetic instability may be expected for thicker films.

Epitaxial growth of CoO films on semiconductor and metal substrates by constructing a complex heterostructure

We have studied atomic structures of α-sexithienyl (6T) films grown on Cu(110) by near-edge x-ray absorption fine structure (NEXAFS). A one-dimensional (1D) ordered structure of 6T with its molecular long axis parallel to the Cu[001] direction could be fabricated by deposition at 300 K and subsequent annealing at 360 K. Polarization- and azimuth-dependent NEXAFS revealed the formation process of the 1D structure and showed the molecular orientation in the in-plane direction directly. We propose a method to obtain the orientation distribution function of molecules using NEXAFS.

Effect of UV/ozone treatment of the dielectric layer on the device performance of pentacene thin film transistors

We have shown, both experimentally and theoretically, that the metal-induced gap states (MIGS) can exist in epitaxially grown organic insulator/metal interfaces. The experiment is done for alkane/Cu(001) with an element-selective near edge x-ray absorption fine structure (NEXAFS), which exhibits a pre-peak indicative of MIGS. An {it ab initio} electronic structure calculation supports the existence of the MIGS. When the Cu substrate is replaced with Ni, an interface magnetism (spin-polarized organic crystal at the interface) is predicted to be possible with a carrier doping.

In-situ measurement of molecular orientation of the pentacene ultrathin films grown on SiO2 substrates

Abstract In order to explain the atomic arrangement of fcc metals with 1 ML thickness deposited on bcc(1xa01xa00) surface, such as Mo and W, the calculation of the interfacial energy between the fcc(1xa01xa01) monolayer and the bcc(1xa01xa00) surface was carried out using the Morse potential. Interactions of deposited fcc atoms with neighboring fcc atoms on the surface and with Mo atoms of the substrate within a constant distance were considered. First, the interfacial energy of the structure with a rigid fcc(1xa01xa01) monolayer on the substrate was calculated by varying the relative rotation angle and the atomic diameter ratio of bcc to fcc. The calculations showed that the energy minimum appears at Nishiyama–Wassermann and Kurdjumov–Sachs orientations at specific values of the atomic diameter ratio, which can be used to predict epitaxial orientation for various fcc/bcc combinations. Second, the calculations can interpret surface superstructures such as the 10×4 structure appearing in the Pb monolayer deposited on the Mo(1xa01xa00) surface with a coincident site lattice structure deformed slightly from the fcc(1xa01xa01) plane, as observed by RHEED experiment.