Study of the electronic bonding of Cl-Si(100) by synchrotron radiation photoemission spectroscopy and many-body calculations

The electronic structure of chlorine chemisorbed on a Si(100)-(2 x 1) surface is investigated by means of synchrotron radiation photoemission spectroscopy and many-body calculations of the one-hole density of states in order to study the effect of strong correlations in the adsorbate layer. The experimental spectrum stands in close agreement with previous experimental work. Three adsorption geometries were considered in the density of states (DOS) calculations: (i) adsorption on both ends of symmetric Si dimers; (ii) adsorption on only the upper Si atoms of buckled dimers; and (iii) a combination of both. Although the energy of the DOS maxima was similar in the three cases, and in almost quantitative agreement with the experimental peaks below the ionisation threshold (13 eV), their intensities and widths were strongly different. Only when structures (i) and (ii) are mixed in the ratio 1-2.5, as suggested by electron-stimulated desorption experiments, does the DOS strongly resemble the photoemission spectrum. These structural effects are also evident in the Cl chemisorption on Si vicinal surfaces, and subsequent annealing of the chlorinated surface, which leads to similar electronic states but with different intensities. The evolution of the experimental spectra with temperature suggests that weaker phases are desorbed, more bound species remaining only at the step edges and, after annealing, at the terraces. (C) 1999 Elsevier Science B.V. All rights reserved.