Dissociative scattering of molecular SiF3+ and SiF+ ions from a Cu (100) single crystal surface has been investigated in the incident energy range from 5 eV to 200 eV with a scattering angle of 77°. The ion intensities of dissociatively scattered ions and parent molecular ions were measured as a function of incident ion energy. The observation showed that the onset energies for the dissociation of SiF3+ and SiF+ ions are 30 eV and 40 eV, respectively, within a precision of ±2 eV. The obtained values are consistent with an impulsive collision model where dissociation of incident ion is caused by vibrational excitation during the collision.
The relationship between the electronic structures of ITO thin films and their optical and electric properties has been investigated by using X-ray photoelectron spectroscopy (XPS) and bremsstrahlung Isochromat spectroscopy (BIS). The spectra of the state densities of valence and conduction bands obtained from XPS and BIS are consistent with those calculated by DV-X molecular orbital method. The state density of the conduction band obtained from BIS increased gradually above Ef. This is related to high carrier mobility and high transparency in the short wavelength region of the ITO film. Curve fitting of the O1s XPS spectra revealed a peak at 531.1 eV embedded in the central part of the spectra, We propose that the oxygen atoms having the binding energy of 531.1 eV to the tin ions which produce carrier electrons in the conduction bands.
Reflection high-energy electron diffraction (RHEED) patterns, so far observed, are mixtures of those due to elastically and inelastically scattered electrons from the specimen surface. The background of the RHEED pattern, which consists of the signals attributed to inelastic electrons, sometimes disturbs the observation of detail diffraction features. In order to exclude these inelastic electrons, a retarding field analyzer was used as the energy filter. By using this energy filtered RHEED (EF-RHEED) apparatus, new RHEED patterns and rocking curves were obtained. In the EF-RHEED pattern of Si (001) 2 × 1 surface, a line pattern due to the disordering of the c (4 × 2) surface structure was clearly extracted from the background. In the EF-RHEED pattern of Si (111) 7 × 7 surface, some additional diffuse patterns were observed. Energy filtered rocking curves of diffraction spots are presented, which are different from conventional ones in their relative intensities. Especially, there is a serious difference when a diffraction spot goes through an intense Kikuchi line. Energy loss spectra of diffraction spots can be measured by this apparatus. It was found that the diffraction beams with very grazing take-off angle suffers a great probability of inelastic scattering from surface plasmon excitation.
The electronic structures of the clean and H-adsorbed (111) surfaces for MC (M = Ti, Zr and Nb) are calculated using Discrete-Variational Xα molecular orbital (DV-Xα MO) method. The calculations for M13C13 clean surfaces cluster show that the characteristic density of state just below EF is composed of mainly d-orbital of metal atom in the first layer, and the contribution of other atoms (carbon atoms in the second layer or metal atoms in the third layer) is found to be very little. Therefore, we ascribe the state just below EF to “the surface state”, which is in good agreement with the one studied by our previous angle-resolved photoemission spectroscopy (ARPES). The calculations for the M13C13H3 H-adsorbed cluster surface are more complicated; the characteristic peak of the states originated from hybridization between Hls and the surface metal d-orbitals are formed at around 6 8 eV for all cases of TiC, ZrC and NbC is shown. This result reveals that the electronic structures of these H/TiC, H/ZrC and H/NbC are essentially similar.
A new approach to XANES calculation is proposed and applied to Si and Fe K-edge XANES spectra to study the efficiency of this method. This method based on the partitioning technique includes important multiple scatterings in infinite order, but excludes unimportant multiple scatterings. The result of calculation for Si 35atom cluster shows that even if we include up to 7th multiple scatterings in the partial sum, the computation time is about 5% of that needed for the full multiple scattering calculation, and a good convergence to the full multiple scattering result is found. Similar result is obtained for iron clusters. The present study demonstrates the high efficiency and accuracy of this new method.
The surface structures and growth mode of Ce thin films on Mo (110) surface were investigated by reflection high-energy electron diffraction. Five kinds of two-dimensional superstructures of ( ), ( ), ( ), ( ) and ( ) and one kind of one-dimensional structure were found with Ce submonolayers. All of these structures show a common periodicity of √2 a0Mo along Mo  direction. This periodicity is considered to be very stable and dominant in case of the submonolayer coverage of Ce thin films on the Mo (110) surface. Cerium grows in accordance with the Stranski-Krastanov growth mode in which two Ce monolayers grow initially in the substrate temperature range from 500 to 800°C. The Ce two-dimensional layers are composed of a distorted fcc γ-Ce (111) layer and a fcc γ-Ce (111) layer for the 1st and the 2nd layers, respectively. The first Ce mono-layer is expanded by 7.8% in  direction and 5.6% in  direction compared with the fcc γ-Ce (111) layer.
The sensitivity of a semiconductor sensor using SnO2 to H2S in air could be enormously promoted by loading SnO2 with a small amount of CuO. However, response kinetics began to deteriorate rather sharply as the H2S concentration decreased below a certain limit, which depended on CuO loadings. XPS measurements on a series of CuO-SnO2 samples calcined in air revealed that the binding energies (BEs) for O1s and Sn3d5/2 levels shifted downward from those of pure SnO2, while Cu2p3/2 level showed an upward shift from that of pure CuO. With increasing CuO loading, the shifts in BE increased or decreased linearly for O1s and Sn3d5/2 levels or Cu2p3/2 level, respectively, indicating continuous shifts in Fermi levels of SnO2 and CuO. For a fixed CuO loading, the magnitudes of the BE shifts were dependent on the methods of CuO loading, reflecting differences in the dispersion of CuO particles on SnO2 grains. These phenomena were well consistent with the formation of p-n contacts between the finely dispersed CuO (p) and the underlying SnO2 (n) grains. The sensitivity to H2S was shown to be well correlated with the magnitudes of the BE shifts, indicating that the formation of the p-n contacts in air and the rupture of them upon exposure to H2S are the origin of the high H2S sensitivity.
We investigated the initial stage of the oxidation of H-terminated Si (100) and (111) surfaces in oxidation solution. A specially designed spectrochemical cell in attenuated-total-reflection geometry was used for observing infrared absorption feature attributed to these surfaces in a contact with the solution. After removing surface oxide and making an H-terminated surface by HF solution, we introduced the oxidation solution into the cell and recorded infrared spectra as a function of time, after exchanging the solution to deionized water to pose the oxidation. We used 3% of H2O2 and 2 ppm of ozonized water as the oxidation solutions. We found that the time evolution of the surface hydride structures, which were observed from 2000 to 2300 cm-1, appeared differently, depending on both the surface orientation and the oxidation solution. With either H2O2 solution or ozonized water, we observed one of the oxide structures of -O3SiH but the other oxide structures such as - (O2Si) SiH and - (OSi2) SiH were not observed on Si (100) as oxide intermediates. On the other hand, all the intermediate structures were observed on (111). When we continued the oxidation for 10 min in ozonized water, all hydride structures were disappeared on both (100) and (111), while a part of the hydride structures were still observable in H2O2 solution. We discussed these features on a basis of our in-situ experiment.
In this study, the authors measured the ratio of the peak area of photoelectrons from s-orbitals to that of the p-orbitals for six elements (Al, Si, Cu, Mo, Ag and Au) resulting in eight s : p ratios. We used two angles (90° and 54.7°) between the incident X-ray beam and the photoelectron detector to investigate elastic scattering effects on the distribution of photoemission from the samples. The data obtained were compared to calculated values. When elastic scattering effects are accounted for, the ratio of s- to p-orbitals by XPS should be independent of angle. The experimental results from five of the eight elemental ratios showed this angular independence. We believe that other effects, such as electron diffraction, will be need to be considered in order to get complete agreement.
The terminating structure of 6H-SiC (0001) fabricated by the Acheson method was directly identified by means of Coaxial Impact Collision Ion Scattering Spectroscopy (CAICISS). The CAICISS spectra proved that the topmost surfaces of samples were Si-terminated planes for both the front and the rear faces. Furthermore, according to the azimuthal dependence of Si peak in TOF spectra, it was also proved that the (0001) Si face was composed of the Si-terminated flat terraces and steps whose height is 7.56 Å corresponding to a half unit cell length of the c-axis of 6H-SiC.
In order to prepare hydroxyl-free or Lewis acid surfaces, silica, titania and HZSM-5 zeolite were first dehydrated and then exposed to dry chlorine at high temperatures. The silica chlorinated at 973 K and the titanic at 873 K had no hydroxyl and were Lewis acidic. However, some oxygen atoms of hydroxyls on the silica and titania had remained as bridge oxygens. When adsorbed pyridine was outgassed at moderate temperatures, the bridge oxygen atoms were converted to hydroxyls. On the chlorination of HZSM-5, 3750 cm-1 peak due to external silanol disappeared at 823 K while 3618 cm-1 peak assigned to hydroxyl associated with framework aluminum atom was eliminated at 973 K. The former was restored when the adsorbed pyridine was outgassed at moderate temperatures. All the chlorinated samples showed no activity against the Friedel-Crafts type alkylation of benzene and naphthalene at room temperature which proceeded easily on chlorinated aluminas. However, the hydroxyl-free surfaces seem likely to be available to prepare new functional surfaces.