[en] The 6x6 and √39x√39 phases on Ag/Ge(1 1 1) have been studied by scanning tunneling microscopy (STM). Four types of 6x6 configurations are found which all consist of a √3x√3 layer with six extra Ag adatoms per 6x6 unit cell. These reconstructions show either mirrored or complementary relations. We observe interesting transitions between the different 6x6 reconstructions. The √39x√39 surface appears to have five extra Ag atoms per unit cell. By using various tip biases, we show that the √39x√39 domain orientation can be changed. Surface structure models of the √39x√39 and 6x6 phases are proposed based on the HCT structure of the underlying √3x√3 surface

[en] We have investigated the initial oxidation stage of an Si(111)-(7x7) surface using valence-band photoemission measurements. As the oxygen exposure increases, the intensities of the dangling bond states of adatoms (S₁) and rest atoms (S₂) decrease. Among the four oxygen-induced states, three originate from the orbitals of adsorbed oxygen species, and one originates from the dangling bonds of adatoms with more than one oxygen atom adsorbed into its back-bond. Taking the dosage-dependent intensity of this modified dangling bond state into account, we conclude that the first adsorption site of oxygen is the back-bond of an adatom

[en] Highlights: • XPS and NEXAFS were used to study PTCDA on Sn/Si(1 1 1)-2√(3)×2√(3). • An unusual charge transfer from the substrate to PTCDA molecules was found. • Charge provided by Sn is donated to the carbonyl C instead of the O atoms. • The charge transfer causes a splitting of the HOMO and LUMO levels. - Abstract: The electronic structures of PTCDA on the Sn/Si(1 1 1)-2√(3)×2√(3) surface have been thoroughly studied by high-resolution photoelectron spectroscopy and near-edge X-ray absorption fine structure (NEXAFS). Upon deposition of PTCDA, there is an unusual charge transfer from the Sn/Si(1 1 1)-2√(3)×2√(3) surface to the molecules. This is clearly shown by a new component in the Sn 4d core-level spectra that shifts towards higher binding energy. In contrast to the literature, the charge provided by Sn is donated to the carbonyl C instead of the O atoms. This is revealed by a new component in the C 1s core-level spectra that shifts towards lower binding energy. The charge transfer causes a splitting of the HOMO level in the valence band spectra. As indicated in the NEXAFS spectra, it also induces a splitting of the LUMO level of the molecules. For thick films the NEXAFS results suggest a layer by layer growth mode

[en] We have investigated the geometric structure of the Ca/Si(1 1 1)-(2x1) surface using low-energy electron diffraction (LEED) and high-resolution core-level photoelectron spectroscopy. A clear (2x1) periodicity was observed in LEED after annealing the (7x1) phase formed at room temperature in LEED. In the Si 2p core-level spectra, three surface components were observed. By considering the energy shift and intensity of each surface component and the Ca 3p core-levels of the two phases, we regard the (2x1) phase to be formed by π-bonded Seiwatz Si chains with a Ca coverage of 0.5 ML

[en] High-resolution photoemission provides important information about the electronic and atomic structure of surfaces. To make full use of the high-energy resolution that is available at many synchrotron radiation facilities, it is important to lower the phonon induced broadening by reducing the sample temperature. Another equally important factor is the sample quality. Sample inhomogeneities may have a significant detrimental effect on the line widths of the core-levels masking essential information. The surfaces discussed in this paper include Si(1 1 1)7x7, Si(1 1 1)1x1:As and Si(1 1 1)√3x√3:Ag. The Si(1 1 1)√3x√3:Ag surface is a good example of the importance of the sample preparation and characterization. A tiny amount of additional Ag atoms on top of the √3x√3 layer leads to a significant broadening of the apparent core-level widths

[en] Highlights: • LuFeO_3 particles exhibit a good sonocatalytic activity toward the RhB degradation. • Various experimental factors on the sonocatalysis efficiency were investigated. • ·OH radicals are produced over the ultrasonic-irradiated LuFeO_3 particles. • Ethanol leads to a quenching of ·OH radicals and a simultaneous decrease in RhB degradation. • ·OH radicals are the primary active species responsible for the dye degradation. - Abstract: LuFeO_3 particles with an average particle size of ∼200 nm were synthesized via a polyacrylamide gel route. The sonocatalytic activity of LuFeO_3 particles was evaluated by the degradation of Rhodamine B (RhB) under ultrasonic irradiation, revealing that they exhibit a good sonocatalytic activity. The effects of various experimental factors including ultrasonic frequency (f), reaction solution temperature (T), catalyst dosage (C_c_a_t_a_l_y_s_t), initial RhB concentration (C_R_h_B), and pH value on the sonocatalysis efficiency were investigated. It is found that the former four factors have an important influence on the sonocatalytic degradation of RhB, where the best degradation conditions are obtained to be f = 60 kHz, T = 40 °C, C_c_a_t_a_l_y_s_t = 4 g L"−"1, and C_R_h_B = 5 mg L"−"1. The pH value has a relatively small effect on the sonocatalytic degradation of RhB compared with other experimental factors. Hydroxyl (·OH) radicals were detected by fluorimetry using terephthalic acid as a probe molecule, revealing that they are produced over the ultrasonic-irradiated LuFeO_3 particles. The addition of ethanol leads to a quenching of ·OH radicals and a simultaneous decrease in the RhB degradation. This indicates that ·OH radicals are the primary active species responsible for the dye degradation

[en] In the Large Helical Device (LHD), the performance of two-dimensional (2-D) extreme ultraviolet (EUV) spectroscopy with wavelength range of 30-650A has been improved by installing a high frame rate CCD and applying a signal intensity normalization method. With upgraded 2-D space-resolved EUV spectrometer, measurement of 2-D impurity emission profiles with high horizontal resolution is possible in high-density NBI discharges. The variation in intensities of EUV emission among a few discharges is significantly reduced by normalizing the signal to the spectral intensity from EUV_—Long spectrometer which works as an impurity monitor with high-time resolution. As a result, high resolution 2-D intensity distribution has been obtained from CIV (384.176A), CV(2x40.27A), CVI(2x33.73A) and HeII(303.78A). (author)

[en] Two-dimensional (2-D) distribution of edge impurity line emissions has been measured for CIV, CVI, FeXV and FeXVIII using a space-resolved extreme ultraviolet (EUV) spectrometer in Large Helical Device (LHD). A strong emission trajectory along the plasma boundary is observed at the top and the bottom edges in the 2-D distribution. The poloidal distribution of impurity emissivity has been evaluated by analyzing the 2-D distribution against magnetic surfaces calculated with a 3-D equilibrium code, VMEC. Inner and outer boundaries of the edge impurity location are estimated by analyzing each vertical emission profile measured at different toroidal positions. The observation chord length passing through an emission contour is calculated based on the radial thickness of the impurity emission location. The poloidal distribution of CIV, CVI, FeXV and FeXVIII with different ionization energies is thus reconstructed from the 2-D distribution. A non-uniform poloidal distribution is clearly observed for all these impurity species located different plasma radii. It is experimentally confirmed that the poloidal distribution becomes gradually uniform as the radial location of impurity ions moves from the ergodic layer to the plasma core. The non-uniform poloidal distribution of CIV emissivity is also confirmed by the simulation with a 3-D edge transport code, EMC3-EIRENE. (author)

[en] Z_e_f_f profile analysis has been carried out in a low-density and high-T_i discharge with carbon pellet injection. The evolution of the Z_e_f_f profile shows a centrally peaked profile just after the pellet injection which then gradually returns to a flat profile. Comparison between the evolution of Z_e_f_f and T_i profiles strongly suggests there is a positive relation between Z_e_f_f and T_i. (author)

[en] The Fe N=3-2 transition array consisting of Fe"1"6"+ through Fe"2"3"+ ions is utilized for impurity transport study in the Large Helical Device (LHD). Since the charge states of Fe"1"6"+ through Fe"2"3"+ are usually distributed all over the whole volume of LHD plasmas, the impurity transport can be studied without any assumption on the radial structure of transport coefficients. A one-dimensional transport code is employed to simulate the emissivity profile of iron line emissions. The transport coefficient is then determined by fitting the experimental profile of n=3-2 Fe transitions in several ionization stages with the impurity transport code. A preliminary result of the iron transport analysis in high and low electron density discharges is reported. (author)