Jun Yoshinobu

The adsorbed states of ethylene on the Si(100)c(4×2), Si(100)(2×1), and the Si(100) 9° vicinal surfaces have been studied using high resolution electron energy loss spectroscopy (EELS) and low-energy electron diffraction (LEED). Ethylene is nondissociatively chemisorbed on the Si(100) surface in the wide temperature range between 77 and ∼600 K, and is rehybridized to have a near sp3 hybridization state. The adsorbed structure is proposed in which ethylene is di-σ bonded to two adjacent Si atoms

Thermal excitation of adsorbed oxygen species is found to initiate the CO oxidation on Pt(111). We have prepared three different coadsorption systems to study the reactivity of different oxygen species; (1) CO on the O2 preadsorbed Pt(111) surface, (2) CO on the nearly perfect Pt(111) p(2×2)-O surface, and (3) CO on the disordered atomic oxygen-preadsorbed Pt(111) surface. Four CO2 desorption peaks (α-CO2 at 125 K, β3-CO2 at ∼225 K, β2-CO2 at ∼260 K, and β1-CO2 at 320 K) are observed. The desorp

The microscopic adsorption state of acetylene (${\mathrm{C}}_{2}$${\mathrm{H}}_{2}$) on Si(111)(7\ifmmode\times\else\texttimes\fi{}7) at room temperature has been studied by using scanning tunneling microscopy. The center adatoms are more reacted than the corner adatoms in a ratio of about 2:1 upon the adsorption of acetylene. It is predominantly the adatoms in the faulted subunit that are reacted by acetylene, rather than those in the unfaulted subunit, indicating that acetylene is initially in

The reaction of carbon dioxide (CO2) on Zn-deposited copper surfaces was systematically investigated by ambient-pressure X-ray photoelectron spectroscopy (AP-XPS). In the presence of 0.8 mbar CO2 and 0.4 mbar H2 gases, hydrogenation products are not observed; only carbonate is formed on Zn-deposited Cu(111) and Cu(997) surfaces. The formation rate of carbonate at 299 K is significantly faster on Zn/Cu(997) than that on Zn/Cu(111), indicating step sites are more reactive for CO2 activation than t

We investigated adsorbed states of CO on Pt(997) at 11 K using infrared reflection absorption spectroscopy. At 11 K, thermal migration is suppressed and thus the initial chemisorption at terrace sites and step sites is controlled by the transient mobility of the adsorbing molecule. The initial occupation ratio between atop CO on the terrace and atop CO at the step is directly determined to be 3.6:1. With a simple isotropic migration model, we estimated the mean lateral displacement from the firs

Adsorbed states of methane on Pt(111) and subsequent processes photoinduced by ArF laser irradiation (193 nm) have been studied by infrared reflection absorption spectroscopy. Adsorption degrades the symmetry of first layer methane from ${T}_{d}$ to ${C}_{3v}$, but the overlayer methane keeps ${T}_{d}$. Only the ${C}_{3v}$ C${\mathrm{H}}_{4}$ in the first layer is photodissociated into C${\mathrm{H}}_{3}$ and H species. These reaction products modify the surface in such a way as to make the rema

Hydrogen-induced structural changes on Pd(110) from 100 to 300 K have been studied by scanning tunneling microscopy. Two kinds of (1\ifmmode\times\else\texttimes\fi{}2) reconstructed surfaces are identified. A pairing-row (1\ifmmode\times\else\texttimes\fi{}2) reconstruction is observed at low temperatures (200 K). During the phase transition from (1\ifmmode\times\else\texttimes\fi{}2) to (2\ifmmode\times\else\texttimes\fi{}1) above 200 K, a significant mass transport of surface Pd atoms is obse

The adsorption of N2 on Ni(111) at 89–115 K under steady-state (quasiequilibrium) conditions has been studied using Fourier-transform infrared reflection absorption spectroscopy (FT-IRAS) and low-energy electron diffraction (LEED). At very low coverage, a single N 3/4 N absorption band is observed at 2218 cm−1 which is assigned to a singleton N2 adspecies. With increasing N2 pressure, two other bands develop at 2212–2208 and 2204–2203 cm−1, and a faint ( 7/8 × 7/8 )R30° LEED pattern is observed.

The site conversion of adsorbed CO between the terminal site and the bridged site on Ni(100) was studied by means of infrared reflection absorption spectroscopy (IRAS). The temperature dependence of the relative occupation for two sites was measured from 80 to 266 K in detail, where the binding-energy difference was determined to be 11 meV. The driving force for the predominant occupation of the terminal site at higher temperature is ascribed to the vibrational entropy of the low-energy degenera

Studies of the elementary chemical-reaction processes of atoms and molecules on Si surfaces, which have been performed mainly by the authors using high-resolution electron energy loss spectroscopy, are reviewed. The adsorbed states, adsorbed sites and adsorbed structures of atoms and molecules, in particular of H, O 2 , NH 3 , N and C 2 H 2 , and thermal decomposition processes of these adsorbates are discussed in detail. Recent studies utilizing scanning tunneling microscope and lasers, and tre