In accurate analyses of XPD spectra, the atomic potential at each site plays an important role. Hermitian potential like Hartree-Fock potential cannot describe the damping of the photoelectron wave, so that it is crucial to go beyond one-electron theory for the XPD analyses. Our optical potential is energy dependent, non-local and self-consistent based on Hedin's GW approximation. Here we apply this optical potential to the N 1s XPD spectra of N2 adsorbed on metals, and compare the results by use of different approximations.
The surface reaction kinetics of Si thermal oxidation was investigated by a real-time monitoring method of Auger electron spectroscopy combined with reflection high-energy electron diffraction. From the time evolution of O KLL Auger electron intensity measured simultaneously with that of RHEED intensity, thermal oxidation on the Si(001) surface under an O2 pressure of 2×10-7 Torr was divided into three temperature regions: (1) Langmuir-type adsorption at T < 630oC, (2) two-dimensional (2D) SiO2 island growth at 630oC < T < 800oC, and (3) etching (active oxidation) at 800oC < T. In the temperature region of 2D SiO2 island growth, an oscillatory behavior of RHEED half-order spot intensity of (1/2, 0) and (0, 1/2) was observed, indicating layer-by-layer etching of the surface between SiO2 islands. The RHEED intensity oscillation was accompanied with an appearance of bulk diffraction spots in RHEED patterns, suggesting a development of protrusions under the SiO2 islands, however no bulk diffraction spots were observed in other two regions. On the basis of the correlation between SiO2 coverage and RHEED intensity of specular, half-order and bulk diffraction spots, the time evolution of surface morphology is discussed for Langmuir-type adsorption and 2D SiO2 island growth.
FeNiN-system materials have a very large magnetic moment that is attractive to be used for high frequencies devices. This investigation focused on magnetic properties of the FeNiN thin films deposited on a substrate at 200oC by magnetron sputtering followed by annealing for 60 min. The energy of exchange coupling for the Fe3NiN thin film deposited at N2 flow ratio FN2 10 % measured was about 1.5 eV from XPS spectrum. The magnetic moment of the Fe3NiN thin film (FN2 = 10 %) was estimated as 7.13 μB based on energy-distribution spectrum shown by XPS measurement. On the other hand, the magnetic moment of the film was evaluated as 7.13 μB based on the lattice constant; a = 0.377 nm that was calculated with a XRD profile, and its magnetization was calculated as IS = 15.5 kG.
In core-level photoemission spectra of simple metals, distinct plasmon loss peaks appear due to excitation of plasma oscillations. This process can be classified into intrinsic and extrinsic ones. Here, plasmon excitation processes by the core-hole potential are called intrinsic and inelastic plasmon losses during photoelectron transport to the surface are called extrinsic. Although there have been many attempts to distinguish these two processes in photoemission spectra, some controversies still remain. Moreover there can be quantum mechanical interference between these two processes. This interference effect has been often neglected in the analyses of experimental data. In this research, we performed angle-resolved Al 2p core-level photoemission experiments and analyzed plasmon loss peak intensity at relatively low photoelectron kinetic energy. Consequently, we found characteristic behavior of plasmon loss peaks as a function of the angle between the polarization vector of incident photons and photoemission direction. We also performed full-quantum-mechanical calculation taking into account the interference, which satisfactorily predicted the experimental results.
ζ-potentials of insulating plates, e.g., quartz and sapphire plates, have been measured by means of the plane interface technique. This technique involves determining the electro-osmotic flow velocity-depth profile of reference (polystyrene latex) particles inside a cell. The electro-osmotic velocity at the lower boundary of the cell, referring to the sample surface-solution interface, permits to calculate the ζ-potential of the sample. However, this method is inapplicable to electrically conductive plates such as metal, because its conductivity results in electrolysis of water and disturbs to establish the electro-osmotic velocity profile. It is proved to be efficient for measuring the ζ-potential of metallic plates by inserting an insulator between the cell and the conductive plate. The size of the spacer is 4 mm inside width and 45 μm thick. The precision and accuracy of this method were proved to be ± 10 mV. This method is applicable to evaluate the adsorption between the aqueous ions and the aluminum alloy plates.
The adsorption of Ag on Ge(001) surface has been studied with first-principle calculations for a coverage range from an isolate Ag adatom up to second Ag atom on the surface. Some stable sites of Ag adatom on Ge(001)-2×1 reconstructed surface were found. The scanning tunneling microscopy (STM) images of each stable or metastable site for the adsorption of a low-coverage of Ag adatom are calculated. Two-dimensional Ag islands observed by STM experiments consist of Ag ad-dimers which lie on the trenches between two Ge dimer rows. The ad-dimers are parallel to the under-lying Ge dimer direction.
A recent experimental result shows that Pt L-edge XANES spectra for Pt small cluster are sensitive to CO adsorption. In the present study we try to extract useful information about geometric and electronic structures of these cluster by applying a full multiple-scattering approach for the XANES analyses. Detailed analyses provide us with information that some extent of change transfer plays an important role for the CO adsorption. We also discuss the plausible adsorption site on the Pt clusters.
For a vicinal Si(001) 2×1 surface, a row of extra spots has been clearly observed along the reciprocal lattice rod in energy-filtered reflection high-energy electron diffraction (ER-RHEED) pattern. The glancing angle dependence of these extra spots along (0 0), (1/2 0) and (1 0) rods was simulated by kinematical analysis based on a monatomic regular step surface. Behavior of these extra spots was reproduced well by the calculations and the mean terrace length along the  direction was estimated. It has been found that this method can evaluate very small vicinal angle near 0.1o, which is superior to low energy electron diffraction (LEED) method in this point.
The influence of translational kinetic energy of incident O2 molecules for the passive oxidation process of partially-oxidized Si(001) surfaces has been studied by photoemission spectroscopy. The translational kinetic energy of O2 molecules was controlled up to 3 eV by a supersonic seed beam technique using a high temperature nozzle. Two translational kinetic energy thresholds (1.0 eV and 2.6 eV) were found out in accordance with the first-principles calculation for the oxidation of clean surfaces. Si-2p photoemission spectra measured in representative translational kinetic energies revealed that the translational kinetic energy dependent oxidation of dimers and the second layer (subsurface) backbonds were caused by the direct dissociative chemisorption of O2 molecules. Moreover, the difference in chemical bonds for oxygen atoms was found out to be as low and high binding energy components in O-1s photoemission spectra. Especially, the low binding energy component increased with increasing the translational kinetic energy that indicates the translational kinetic energy induced oxidation in backbonds.
Adsorption of water on oxidized ZrC(100) surfaces at room temperature has been studied by photoelectron spectroscopy. It is found that the reactivity of the ZrC(100) surface with water in adsorption is much enhanced when the surface is covered with an ordered suboxide (ZrO) like layer.