Surface core-level shifts for Ge(100)−(2 × 1)

Using surface-sensitive photoemission techniques, Ge 3d core-level binding energies for surface atoms of Ge(100)?(2 × 1) are found to be smaller than the bulk values by 0.41 eV. The surface atoms with shifted core-level binding energies correspond to one full (100) atomic layer. A surface core-exciton resonance is observed in the partial-yield measurements. The empty surface state involved in this excitonic transition, without binding-energy correction, is located at the valence-band maximum.     

Surface core-level binding energy shifts in alloys

A simple theory for the core-level binding energy shifts at the surfaces of binary alloys A_xB_1?x is presented. Results are given for the surface core-level shifts of Ni in Ni_xCu_1?x alloys and Pd in Pd_xAg_1?x alloys. It has been shown that the surface core-level shifts may depend sensitively on surface segregation.     

Surface energy bands observed in photoemission from a (1 × 1)-N structure on Cr (100)

The surface structure obtained on Cr (100) by diffusion of nitrogen from the bulk is studied by angle resolved photoemission. It is found that nitrogen is bonded in an ordered (1 × 1) configuration with a crystallographic point group C_4v. The data display a strongly dispersive two dimensional Bloch character for the N2p derived resonances. For these bands the symmetry at the $\text{Γ}$ point and the dispersion along the $\text{Δ}$ and $\text{Σ}$ lines of the surface Brillouin zone are determined. The results indicate a strong interaction of the nitrogen atoms with the substrate and favor the intersticial fourfold hollow position.     

Surface core-level shifts for chlorine covered GaAs (1 1 0) surfaces

Photoemission measurements show that upon chlorine adsorption the Ga 3d surface core-level remains essentially unchanged whereas the As 3d level is shifted by 820 meV to higher binding energy changing the sign of the shift with respect to the bulk level. Chlorine is thus bound to As in a single chemisorption state. The shift is due to charge transfer. The adsorption does not change the surface relaxation.     

Plasmon excitation in core-level photoemission

The surface and bulk plasmon satellites in photoemission from a core level are calculated, treating the photoelectron quantum mechanically and including plasmon dispersion. The long wavelength plasmon excitations are suppressed by interference between intrinsic and extrinsic processes, giving featureless satellites at low electron kinetic energy. Structure develops as the electron kinetic energy increases.     

Ordered oxygen overlayers on Cr(100) observed by leed and photoemission

Chemisorbed oxygen atoms on Cr(100) induce strong O(2p) derived surface resonances which are studied by angle resolved photoemission. Well ordered structures are observed after annealing (300°C). In the submonolayer range (θ_O < 1) a study of the symmetry and dispersion of the O(2p) derived features shows the two-dimensional Bloch character associated with either a c(2 × 2)-O surface at low coverages (θ_O?0.25) or a (1 × 1)-O structure at high coverages (θ_O?0.9). When combined with LEED observations and work function data this study indicates that both structures coexist around θ_O = 0.5 and chemisorbed oxygen is probably incorporated into the fourfold hollow sites. At θ_O > 1, the onset of oxidation is clearly shown in the valence band and core level spectra and the data support the existence of a thin spinel-like oxide layer.     

Resonant photoemission from SmS(100)

A strong, sharp resonance enhancement of 4f photoemission has been observed on SmS(100) surfaces for photon energies in the region of the 4d-4f transitions at about 126 eV. The discrete final state reached via the excitation hν+4d¹⁰4f⁶→4d⁹4f⁷ autoionizes primarely via a super Coster-Kronig transition of the type 4d⁹4f⁷→4d¹⁰4f⁵ + unbound electron. Other decay channels, e.g, Sm 5p emission, as well as a surface induced binding energy shift in the Sm³⁺ final state are identified and discussed.