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The surface photo-voltage (SPV) effect and its temporal profile on a Cr/p-GaAs(100) surface were measured by core-level photoelectron spectroscopy with the combination of synchrotron radiation and laser. It was found that the SPV value at the Cr thickness of 0.05 and 0.1 nm is enhanced in comparison with the clean surface, while that at the Cr thickness larger than 0.2 nm is remarkably suppressed. The dependence on the Cr thickness can be interpreted in terms of the change in the band bending and the escape process, which are associated with the electronic structures induced by the Cr deposition. [ABSTRACT FROM AUTHOR]

The valence electronic structures of the dental gold alloys, type 1, type 3, and K14, and their interaction with L-cysteine have been studied by ultraviolet photoelectron spectroscopy with synchrotron radiation. It was found that the electronic structures of the type-1 and type-3 dental alloys are similar to that of polycrystalline Au, while that of the K14 dental alloy is much affected by Cu. The peak shift and the change in shape due to alloying are observed in all the dental alloys. It is suggested that the new peak observed around 2 eV for the L-cysteine thin films on all the dental alloys may be due to the bonding of S 3sp orbitals with the dental alloy surfaces, and the Cu-S bond, as well as the Au-S and Au-O bonds, may cause the change in the electronic structure of the L-cysteine on the alloys. [ABSTRACT FROM AUTHOR]

A unique analytical method is proposed for local structure analysis via extended X-ray absorption fine structure (EXAFS) spectroscopy. The measurement of electron energy distribution curves at various excitation photon energies using an electron energy analyzer is applied to determine a specific elemental Auger spectrum. To demonstrate the method, the N K-edge EXAFS spectra for a silicon nitride film were obtained via simultaneous measurement of the N KLL Auger and background spectra using dual-energy windows. The background spectrum was then used to remove the photoelectrons and secondary electron mixing in the energy distribution curves. The spectrum obtained following this subtraction procedure represents the `true' N K-edge EXAFS spectrum without the other absorptions that are observed in total electron yield N K-edge EXAFS spectra. The first nearest-neighbor distance (N-Si) derived from the extracted N K-edge EXAFS oscillation was in good agreement with the value derived from Si K-edge analysis. This result confirmed that the present method, referred to as differential electron yield (DEY)-EXAFS, is valid for deriving local surface structure information for low- Z elements. [ABSTRACT FROM AUTHOR]

A first-order phase transition in a bulk material is generally considered to arise at extended defects such as grain boundaries or dislocations, where the energetic barrier between the two phases is reduced. Downsizing a crystal to the nanoscale can exclude the number of defects, leading to enhanced kinetic stabilization of the metastable phase. Here, the disappearance of the first-order metal-insulator transition in defect-free V2O3 nanocrystals and the revival of the transition by introducing a certain Cr or Ti impurity content are investigated. The hysteresis width of the transition corresponding to the barrier height decreases with the impurity content. It is proposed that homogeneous impurity doping is a universal method that can control the occurrence of a first-order phase transition in nanoscale materials. [ABSTRACT FROM AUTHOR]

Photoelectric emission from organic and metal thin films is generally observed with irradiation of photon energy larger than 4 eV. In this paper, however, we report photoelectric emission from Ag on a zinc-phthalocyanine (ZnPc) layer at a photon energy of 3.4 eV. The threshold energy for this photoelectric emission is much smaller than the work function of Ag estimated by conventional photoelectron spectroscopy. The photoelectric emission by low-energy photons is significant for Ag thicknesses of less than 1 nm. Photoelectron spectroscopy and morphological study of the Ag/ZnPc suggest that the anomalous photoelectric emission from the Ag surface is caused by a vacuum level shift at the Ag/ZnPc interface and by surface plasmons of the Ag nanoparticles. [ABSTRACT FROM AUTHOR]

We have investigated the defect formation processes of BaF2 single crystals under vacuum ultraviolet radiation with the use of combination spectroscopy of synchrotron radiation (SR) and laser. The defect formation efficiency was measured as a function of excitation photon energy of SR by means of a laser-induced luminescence method. It was found that the efficiency depends significantly on the excitation photon energy. We show that the dependence can be explained in terms of the diffusive motion of hot conduction electrons generated by the photoexcitation. The relationship between the defect formation and the energy relaxation of core excitons is also discussed. [ABSTRACT FROM AUTHOR]

Resonant and constant-initial state photoemission spectroscopies using synchrotron radiation were applied to investigate the valence-band electronic structure of a semi-conducting β-type iron-disilicide (β-FeSi2) thin film. The results clearly indicated that the component elements, iron (Fe) and silicon (Si), contribute differently to the valence band features; the Fe 3d orbitals mainly concentrate in the top region of the valence band while the Si 3s and 3p orbitals spread over the wide region of the valence band. The β-FeSi2thin film showed a typical p-type semi-conducting nature with a work function of 4.78 eV. The β-FeSi2film showed the Fe M1VVAuger lines around the kinetic energy of 88 eV. It would be expected from these observations that there exist strong interactions between iron and silicon atoms in the β-FeSi2film resulting in orbital mixing and band formation. [ABSTRACT FROM AUTHOR]

Highlights the 5th Asian Synchrotron Radiation forum in Saga, held on March 16-17, 2004, at Tosu, Saga, Japan. Attendees; Programs and activities; Sponsors of the event; Keynote speakers; Event description.

Core-level photoelectron spectroscopy with the combination of synchrotron radiation (SR) and a laser was used for exploring the surface-photovoltage (SPV) effect and its temporal profiles in a GaAsGaAsP superlattice (SL). It was observed that the SPV value in the SL is suppressed as compared with a bulk GaAs. However, no significant difference was found in the temporal profile between the bulk and the SL. It is suggested that the suppression of the SPV in the SL is dominantly due to the small value of band bending under thermal equilibrium. [ABSTRACT FROM AUTHOR]

We have performed a photoemission study on an organometal spin-crossover complex, [Fe(2-pic)[sub 3]] Cl[sub 2]EtOH, using the combination of synchrotron radiation and laser. The core-level and valence-band photoemission spectra were measured for high-spin, low-spin, and photoinduced phases. The N Is and valence-band spectra showed remarkable changes due to the photoinduced phase transition, indicating that the electron charge was transferred from nitrogen to iron at the photoinduced phase transitions. It was also found that the valence-band structure of the photoinduced phase is very different from that of the high-spin phase caused by the thermally induced phase transition. [ABSTRACT FROM AUTHOR]

The nonradiative decay processes of the Ba-5p core exciton in BaF[sub 2] have been investigated by using photoelectron spectroscopy, since the exciton peak is missing in the excitation spectrum of the Auger-free luminescence. The decay probability of the direct recombination process estimated from the constant-initial state spectrum and the absorption coefficient was found to be smaller than unity, indicating the existence of the other decay processes. It is suggested that the Ba-5p core exciton is relaxed by about 0.9 eV. [ABSTRACT FROM AUTHOR]

Focuses on the energy-selected electron-ion coincidence spectroscopy for the study of surface dynamics combined with synchrotron radiation. Components of the equipment; Excitation of the sample surface; Desorption of ions; Evaluation of the apparatus based on photoelectron-photoion coincidence and Auger electron-photoion coincidence.

We have performed angle-resolved two-photon photoemission (AR-2PPE) measurements of Bi thin film with the thickness of 12 bilayers grown on Si(111) surface. From the excitation photon-energy dependence of AR-2PPE spectra, we have obtained the energy dispersion of unoccupied electronic states in the energy range between 2.0 and 3.0 eV above the EF. The observed electronic states are attributed to the unoccupied quantum-well states due to quantization of the 6 p-derived bulk bands along the Γ-T direction. [ABSTRACT FROM AUTHOR]

The valence electronic structure of p-type β-FeSi2 single crystal has been investigated by high-resolution and resonant photoelectron spectroscopy using synchrotron radiation. In the photoelectron spectrum at hν = 130 eV, the valence band has a prominent peak at the binding energy (EBin) of 0.5 eV and the valence band maximum almost touches the Fermi level, reflecting the p-type nature. Upon the excitation of Fe2p3/2 core level, the valence-band top at EBin = 0.5 eV exhibits an interference-like resonant behavior clearly shown by a constant-initial-state spectrum. These results are the direct experimental evidences that the valence-band top consists mainly of Fe3d orbitals. [ABSTRACT FROM AUTHOR]

The electronic structure of the silver-based dental alloy MC12 and its constituent metals and their interaction with l-cysteine have been investigated by ultraviolet photoelectron spectroscopy (UPS) using synchrotron radiation. The UPS spectra of l-cysteine on polycrystalline Ag, Cu, Pd, and Au substrates have been measured to understand the interaction of l-cysteine with the dental alloy surface. It was found that the electronic states of MC12 originate dominantly from Cu 3d states and Pd 4d states around the top of the valence bands, while the 4-7-eV electronic structure of MC12 originates from the Ag 4 d5/2 and Ag 4 d3/2 states. For l-cysteine, it was found that a new peak at 2 eV is observed for the thin films on Ag, Cu, and Au, while the structure around 2 eV on MC12 is similar to that on Pd. The shift of the 5-eV peak is observed for the thin films on Cu, Pd, and Au, but not on Ag and MC12. These results indicate that the interaction of l-cysteine with MC12 may be dominantly due to the Pd-S, Cu-S, and Ag-O bonds, while the contribution of the Ag-S bond is small. [ABSTRACT FROM AUTHOR]

Two-photon absorption spectra due to the valence excitons in CaF[sub 2] and BaF[sub 2] have been measured using the second harmonic of the output of a XeCl-excimer-laser pumped dye laser as a light source. The band gap energies of CaF[sub 2] and BaF[sub 2] are obtained as 11.8 and 10.6 eV at 298 K, respectively. The two-photon absorption coefficient β in the spectral region below the 2P exciton is expressed by an exponential function of the photon energy in both crystals. The values of β at the 2P exciton peak are about 2×10[sup -9] cm/W for CaF[sub 2] and 3×10[sup -9] cm/W for BaF[sub 2]. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Describes the design concept of a spherical grating monochromator with translational and rotational assembly including a normal incidence mount (SGM-TRAIN) that is under construction at beamline 5A of the UltraViolet Synchrotron Orbital Radiation facility in Japan. Design requirements; Photon energy; Driving modes; Ways to suppress the higher-order light.

Develops a time-gated photon measurement method for two-photon absorption spectroscopy by combinatorial use of synchrotron radiation (SR) and laser. Synchronism between nanosecond laser and subnanosecond SR pulses by a timing circuit; Induction of luminescence signal by two-photon excitation; Ability to obtain high-sensitivity and good signal-to-noise ratio.