Auger electron intensity of Si-LVV from Si(001) 2×1 surface has been measured at room temperature (RT) for while changing the glancing angle of incident electron beam of RHEED. Such beam-rocking Auger electron spectroscopy (BRAES) profile shows intensity anomalies at surface wave resonance (SWR) conditions. Surface structure of Si(001) 2×1 has been analyzed by rocking curves of diffraction spots within the 0-th Laue zone. Because, RHEED intensities limited to the 0-th Laue zone can be determined by the projected potential of the Si atomic rows along the incident azimuth and then the phase of asymmetric dimers with flip-flop motion can be neglected. According to the Si(001) 2×1 surface structure model confirmed by the rocking curve analysis, it has been found that the calculated wave-field intensity profile on Si atoms reveals the similar intensity anomalies to those of experimental BRAES profile.
‘SurfSeg’ is a simulation software that predicts surface segregation behavior of an under-layer element in layered materials, which was developed by the author. After briefly introducing the principle of the prediction, the accuracy is discussed based on the approximation used for the prediction. Then, appropriate conditions for utilizing the simulation is discussed from a viewpoint of comparing simulated results with experimental results.
The growth of single-walled carbon nanotubes (SWCNTs) was examined by hot-filament chemical vapor deposition (CVD) at low temperatures using a double-layer film consisting of nickel and cobalt layers as a catalyst. Ethanol was used as the carbon source. At a growth temperature of 350°C, few SWCNTs were grown when a cobalt film was used as a catalyst, whereas the growth of SWCNTs was confirmed when a double-layer film consisting of nickel and cobalt layers was used as a catalyst. However, at a growth temperature of 450°C, the yield of SWCNTs was higher when the cobalt film was used than when the double-layer film was used. The optimum thicknesses of the nickel and cobalt layers for obtaining SWCNTs were 1.0 and 1.2 nm, respectively. By laminating the nickel and cobalt layers, the catalyst film changed into particles at a growth temperature of 350°C. To obtain such nanoparticles, a nickel layer should be formed on an oxidized cobalt layer.
Using advanced frequency modulation atomic force microscopy, the structure at solid-liquid interfaces was determined on well-controlled surfaces with sub-nanometer resolution. Site-specific structuring of interfacial water was found on the surfaces containing hydrophilic functional groups, dominated by the hydrogen bond interaction. Interfacial structure of liquid alcohols was subject to the competitive two interactions ; hydrogen bond interaction between OH groups and van der Waals interaction between alkyl chains.
Surface is a matter having own chemistry, which provides unique material named “quasi-compounds”. Formation of active materials is essential on some catalysts. Formation of active hybrid layer composed of (-Rh-O-)/Pt on Pt-Rh(100) alloy, Pt/Rh(100), Rh/Pt(100), Rh/Pt(110), Pt/Rh(110) is a typical example, which is responsible material for superior active catalyst for NO reduction. Oxidation of CO is slow at 60oC on a 1 wt. % Pt/TiO2, but is very rapid on a Pt/TiO2 covered with large amount of FeOx in the presence of H2 and/or H2O. In-situ IR spectroscopy proved a new catalytic oxidation (hydro-oxidation) of CO via HCOO and OH. Selective hydrogenation of DOM (CH3OOCH2-COOCH3) on Au/SiO2 influenced by small amount of Ag is a case of adsorption strength of intermediates influenced by additives.
There is often the lack of reproducibility in photocatalysis, the reason for which is partly the fact that the photocatalysis is not simple photo-induced catalysis on the surface, but rather the result of the total performance of the device-like system that involves bulk diffusion of the photo-excited minority carrier and its charge transfer across the interface. Therefore very small amount of unexpected defects and impurities in a photocatalyst, which could hardly be detected by the conventional surface science analysis techniques, would essentially make it difficult to reproduce its semiconductor properties and hence the resultant photocatalysis. In this review, a new approach based on a recent progress in oxide epitaxy to precision structural control of photocatalysts is proposed and the possible effects of surface structures, defects and impurities on the photocatalysis will be discussed from the viewpoints of semiconductor physics as well as surface science, showing some of our experimental demonstrations.
Helical spin texture with the remarkably high spin polarizations of topological surface states have been firstly uncovered by the innovative spin- and angle-resolved photoemission spectroscopy for two promising topological insulator Bi2Te2Se and Bi2Se2Te. Their highly spin-polarized natures are found to be persistent across the Dirac point in both compounds. This novel finding paves a pathway to extending the utilization of topological surface state of these compounds for future spintronic applications.
Graphene is the promising material for the next-generation devices owing to its novel electronic property which is governed by “slow” relativistic quantum theory. The theory tells that pseudospin responds to pseudoelectromagnetic field emerged by strain. In this paper, we have studied the pseudoscalar potential in epitaxial graphene grown on microfabricated SiC substrates (μ-EG). It is clarified by low-energy electron microscopy and Raman spectroscopy that pseudoscalar potential emerges in μ-EG due to interfacial strain, and is controlled by the microfabrication pattern.
Surface X-ray scattering (SXS) technique is ideal to determine the three-dimensional structure at the solid/liquid interfaces with a high spatial resolution. When elements with an atomic number next to each other exist at the interface, however, the interfacial structure cannot be precisely determined from the normal SXS meausrements, because the values of the atomic scattering parameters of each element are too near. Using the anomalous scattering effect, the resonance SXS (RSXS) method was proposed and carried out under ultra high vacuum (UHV). We applied this RSXS method to the solid/liquid interface, i. e., electrochemically deposited Pt layer on Au(111) surface in the electrolyte solution, and demonstrated that the anomalous scattering parameter effect is utilized at the solid/liquid interfaces.