An experimental electronic bandstructure of molybdenum disulphide has been determined from angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) measurements: polar-angle-dependent ARUPS at a photon energy of 21.2 eV allows the authors to obtain an approximate plot of dispersion parallel to the basal face while photon-energy-dependent ARUPS at normal emission gives a plot of dispersion perpendicular to this face. The experimental bandstructure is compared with three calculations and, while there is a general agreement, specific aspects are better reproduced when there is self-consistency in the calculations. An analysis difficulty reported earlier for polar angle ARUPS for this material can now be understood as arising from incorrect labelling of symmetry directions in the experiment.

Water adsorption on Si(100) and Si(ll1) surfaces at room temperature has been investigated by angle-resolved ultraviolet photo-electron spectroscopy (ARUPS) using synchrotron radiation. Earlier angle-integrated UPS studies have suggested that the adsorption is non-dissociative on (100) and dissociative on (111). The ARUPS data indicate that the adsorptionis dissociative on both surfaces; the adsorbate-related valence features are similar and their binding energies agree closely with a self-consistent calculation of quasi-molecular SiOH. In this common dissociative-adsorption scheme there is no conflict between UPS and other techniques. The calculation provides an assignment of features which may allow the adsorption geometry to be probed by the application of photo-emission selection rules.

The adsorption of Bi and Sb on clean cleaved InP ( 110) surfaces has been studied with soft x-ray photoemission spectroscopy at the BESSY synchrotron radiation source in Berlin. Bi and Sb were deposited onto ultrahigh vacuum cleaved InP (110) surfaces at substrate temperatures of 300 K [room temperature (RT)] and 120 K [low temperature (LT)]. In this paper we focus on the evolution of the overlayer emission intensities as a function of coverage. Spectra of the Bi Sd and Sb 4d core level emission lines were taken from the submonolayer regime up to coverages of approximately 60 and 20 monolayers (ML) of Bi and Sb, respectively. The spectra were then deconvoluted using a core level fitting routine. In all cases, good agreement between the experimental and fitted curves was achieved by introducing two chemically shifted components of the Bi Sd and Sb 4d core level emission which are interpreted in terms of Bi(Sb )-substrate and Bi(Sb)-Bi(Sb) bonds. However, for RT deposition, the evolution of the Bi 5d and Sb4d spectra is significantly different in the coverage range below 2 ML. In the Bi case the adatom-substrate component grows first, and only after about 0.5 ML is the Bi-Bi component observed. The two components have equal intensity at about 2 ML. In contrast, the two components in the Sb 4d spectra grow with equal intensity until 1 ML. The spectra for higher coverages for both systems are dominated by the component assigned to adatom-adatom bonds and the overlayer is found to be semimetallic. The L T spectra do not have the easily resolvable features seen in the RT spectra which may indicate that the growth is much more disordered. However, the overlayers at L Tare more laminar. In addition, we present the band bending versus coverage behavior for the Bilp-InP(1IO) interface, which is compared to that ofSb/p-InP(1IO).

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