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We present a high-resolution ultraviolet photoelectron spectroscopy study of the room temperature Cs chain formation on InAs(110), analysing the valence band spectra and core levels in the whole coverage range from the self-assembling of the Cs chains to the cluster uptake at saturation coverage. The valence band data shows an insulating behaviour up to saturation coverage. The adsorption sites have been monitored by means of Cs-4d, In-4d and As-3d core levels. The Cs-4d core-level data shows two distinct components, consistent with the presence of two unequivalent Cs adsorption sites in the Cs nanowire. The In-4d and As-3d levels show Cs-induced extra components due to electronic level re-hybridization to the substrate atoms, and predominant charge transfer from Cs adatoms to In, in agreement with recent theoretical calculations. (C) 2001 Elsevier Science B.V. All rights reserved.

A high resolution fore-level photoemission investigation of 2D ordered Bi layers grown on Si(100)-(2 x 1) is presented. We study the Si 2p and Bi 5d core-levels at room temperature as a function of coverage and in the reconstructed phases. The different Bi structural configurations around the monolayer coverage and in the (2 x n)-reconstructed phase are derived from the core-level lineshape evolution. By following the Fermi level pinning, the presence of Bi-induced occupied electronic states close to the Si mid-gap is suggested. (C) 1999 Elsevier Science B.V. All rights reserved.

Bismuth adsorbed on Si(001) induces successive (2 x n) phases after annealing, with n ranging from 12 to 5. The structure consists of dimer rows, with missing-dimer defects forming and ordering in the perpendicular direction. We investigated by grazing-incidence X-ray diffraction the n = 6.45 surface, which results from missing-dimer line ordering each 6 or 7 units. The structural refinement is based either on a (2 x 6) or a (2 x 7) cell. The Bi dimers are lying at 1.86 Angstrom on top of Si, with a dimer bond length of 3.11 Angstrom. They are displaced along the row towards the missing dimer, while the Si atoms are at bulk positions. A photoemission study of the Bi 5d and Si 2p core levels confirms the model of symmetric Bi dimers, after breaking Si dimers, The diffracted intensity is calculated using the phase-matrix method. The positions and widths of the peaks are analysed in terms of the dimer blocks probability distribution. (C) 1999 Elsevier Science B.V. All rights reserved.