Lower Binding Energy Region Research Articles

Mechanism of Ag sulfurization resistance improvement by alloying solutes in Ag-based alloy films

The Ag sulfurization resistance of the pure Ag film and four Ag-based alloy films was evaluated by the reflectance decay after the Ag sulfurization test. Among all Ag-based alloy films, the In alloying solute in the Ag-In alloy film shows the best resistance to the Ag sulfurization. Using x-ray photoelectron spectroscopy analysis, the chemical state of the alloying solutes in the Ag-based alloy films was examined. It is found that, with being alloyed in the Ag matrix phase, the 3d5/2 core-level peak positions of the alloying solutes (In, Sn, and Pd) shift toward the lower binding energy region, which is defined as a negative chemical shift. The chemical shifts of In, Sn, and Pd alloying solutes are –0.31 eV, –0.23 eV, and –0.2 eV, respectively. The absolute value of the negative chemical shift represents the tendency of Ag atoms losing valence electrons to the alloying solutes. As the Ag atoms lose valence electrons to the alloying solutes, the Ag atoms have a less tendency to provide the valence electrons to form covalent bonding with S atoms, which suppresses the Ag sulfurization reaction (2Ag + S → Ag2S). Therefore, the larger the absolute value of the negative chemical shift, the higher is the reflectance decay (lesser Ag sulfurization resistance).

Resonant photoemission study of epitaxial La0.7Sr0.3MnO3 thin film across Curie temperature

The electronic structure of epitaxial La0.7Sr0.3MnO3 thin film grown on LaAlO3 (001) substrate has been studied by resonant photoemission spectroscopy across Curie temperature (TC). Temperature dependent variations in the valence band structure divulge that beyond TC, Mn-O 2p hybridization is reduced. It is found that nature of the states in the lower binding energy range above TC would be rather due to Mn3+ ions, whereas below TC Mn3+ and Mn4+ contributes equally in the low binding energy region. At higher binding energy values, Mn4+ contribution is larger in the Mn-O hybridization at all temperatures.

Photoemission study on double-decker type bis(phthalocyaninato)tin(IV) and its complexes

Ultraviolet photoelectron spectroscopy (UPS) has been applied to investigate the valence electronic structures of the double-decker type phthalocyanine compound, bis(phthalocyaninato)tin(IV) (SnPc2). The binding energies of spectral features were precisely determined and compared to those of tin(II) and lanthanide compounds. Two peaks were observed at 5.11 and 6.04eV in the lower binding energy region, which corresponded to the molecular orbitals generated by the anti-bonding and bonding interactions between the orbitals of the two phthalocyanine rings, respectively. It is worthy to note that the ionization threshold of SnPc2 is remarkably small as compared to other phthalocyanine compounds, implying ease of oxidation. Actually, oxidized forms of SnPc2 were easily obtained by both chemical and electrochemical reactions, and their electronic structures were discussed in comparison with that of SnPc2 and with the recent results of the density functional theory calculations.

Observation of anomalous peaks in the photoelectron spectra of highly oriented pyrolytic graphite: Folding of the band due to the surface charge density wave transition

The angle-resolved photoelectron spectroscopy with low-photon energy (7--16 eV) is used for the investigation of highly oriented pyrolytic graphite at a low temperature. We observed for the first time peaks in the low binding energy region (from the Fermi level to 0.7 eV) of the surface normal photoelectron spectra at 11K, which disappear above \ensuremath{\sim}30K. Based on the dispersion both along the parallel and normal to the surface, the peaks are ascribed to the emission from the K(H)-point that is backfolded into the \ensuremath{\Gamma}(A)-point as a result of the two-dimensional superperiodicity. The surface charge density wave transition is proposed for the driving mechanism of the superperiodicity based on the temperature dependence of the photoelectron intensity.

UPS study of VUV-photodegradation of polytetrafluoroethylene (PTFE) ultrathin film by using synchrotron radiation

The VUV-photodegradation of polytetrafluoroethylene (PTFE) ultra-thin film was studied by ultraviolet photoelectron spectroscopy and quadrupole mass spectrometry. These results were compared with the previous photodegradation studies of the polyvinylidenefluoride (PVDF) and polyethylene (PE). Generation of new peak, π-band originated from the CC bond, was observed in the low binding energy region of the UPS spectra in both PVDF and PE during the photodegradation. In contrast, no new peak generation was observed in the UPS of the photodegraded PTFE. Mass spectrometry analysis also suggested that the CC bond generation is not a major mechanism in the VUV photodegradation of PTFE.

Quasiparticle energy bands of transition-metal oxides within a model GW scheme

We calculate the quasiparticle band structure of NiO and ${\mathrm{CaCuO}}_{2}$ by using a model self-energy correction which approximates closely the GW method of Hedin. We obtain energy gaps and magnetic moments in agreement with experiment. For NiO, our results agree with integrated and angle-resolved photoemission experiments in the low binding energy region. The spectral distributions of O 2p and Ni 3d states are discussed, in relationship with the available experimental data. Our results demonstrate that the addition of self-energy corrections to local-spin-density band calculations provides a meaningful description of many aspects of the electronic states of transition-metal oxides. As expected, the satellite structures observed in photoemission experiments are not found in our calculations.

Core-to-Rydberg excitations and their Auger decay in the HCl and DCl molecules.

The resonant Auger electron spectra of the HCl and DCl molecules have been measured at the first core-to-Rydberg resonances. The low binding energy region of the spectra has been decomposed into transitions to different bound states and their vibrational progressions. Several transitions have been assigned using the strict spectator model. The total ion yield spectrum of HCl in the energy region of the core-to-Rydberg resonances has been recorded and its assignment refined with the help of the Auger electron and chlorine 2{ital p} photoelectron spectra. {copyright} {ital 1996 The American Physical Society.}

In-situ characterization of doping-effect on electronic structure of epitaxial films of infinite layer SrCuO2

Change of electronic structure of infinite-layer SrCuO2 epitaxial film with both hole-and electron-doping has been studied byin-situ photoemission spectroscopy. In both of the cases, semiconducting gap in the vicinity of the stoichiometric compound has been vanished by “light-doping”. By further introductions of carriers, monotonous shifts of corebinding energies have been observed; the shift toward lower binding-energy region by the hole-doping, and that toward higher side by the electron-doping. Total amount of the shift over the whole range of the doping was much smaller than the semiconducting gap. For the metallic regions, comparison between the energy-shift observed and that expected by a calculation under local-density-approximation is discussed.

X-Ray photoelectron spectra of some bioinorganic complexes of the rare earths with N-acetylalanine

X-Ray photoelectron spectra of some bioinorganic complexes of La, Ce, Pr, Nd, Sm and Eu with N-acetylalanine have been measured and the 3d52 and 3d32 main peaks and their satellites have also been assigned. The spin—orbit splitting between the 3d52 and 3d32 core-level of the rare earth ion in these complexes becomes slightly larger than that of the free rare earth atom due to the effect of the crystal field. The satellite for the 3d main peaks of La in the solid state complex are in higher binding energy region and may be attributable to the L → 4ƒ charge-transfer shake-up process. The satellites for the 3d main peaks of Ce, Pr, Nd, Sm and Eu are in the lower binding energy region and may be attributable to the 4ƒ→L charge-transfer shake-down process.

Intramolecular band mapping of poly(p-phenylene) via UV photoelectron spectroscopy of finite polyphenyls

Abstract Ultraviolet photoelectron spectra were measured of solid sexiphenyl with synchrotron radiation and of gaseous polyphenyls from biphenyl to sexiphenyl with a Hel light source. The similarity of the spectrum of the solid with the XPS spectrum of poly(p-phenylene) (PPP) shows the usefulness of sexiphenyl as a model compound of PPP. Examination of the fine structure observed in the low binding-energy region clearly shows how the electronic structure of the p-phenylenes evolves from that of benzene including the effects of deeper levels and of the non-planarity of the molecular geometry. The experimental E = E(k) energy band-dispersion relation of a PPP chain can be deduced by giving each energy level of the oligomers an appropriate k value. An extrapolation for the total bandwidth and the threshold photoemission energy of solid PPP yields 3.95 and 5.65 eV. respectively.

Photoelectron spectra of substituted benzenes: II. Seven valence electron substituents

The He I photoelectron spectra of the isoelectronic series of substituted benzenes toluene, aniline, phenol, and fluorobenzene have been measured and the ionization bands in the low binding energy region of the spectra have been identified and assigned. The spectrum of pentafluoroaniline has also been obtained in order to use the “perfluoro effect” to identify the lowest energy σ ionization band. The photoelectron bands were assigned by using a “composite molecule” approach in which the known levels of benzene and the various substituents are correlated with those of the molecule, by using information supplied by vibrational analysis of the bands, and by reference to CNDO/2 and INDO MO calculations. The spectra of these composite molecules are consistent with the … 1 a 2u(π), 3 e 2g(σ), 1 e 1g(π) MO configuration of benzene. The e 1g(π) orbital is split into two components in all of these substituted benzenes. Vibrational progressions in the ring CC stretching and the X-sensitive modes have been identified in these π ionization bands. Excitation of these two modes is evidence for delocalization of the π electrons over the composite molecule. The n (nonbonding) orbital of the substituents is shown to occur in the penultimate region along with the 1 a 2u(π) and 3 e 2g(σ) orbitals. The shifts in the n and π orbitals between the composite molecules and their constituent molecules are discussed in terms of resonance and inductive effects.