Substrate and morphology effects on photoemission from core-levels in goldclusters

The combination of X-ray photoelectron spectroscopy and spectrophotometry o f supported gold clusters on SiO2 reveals the importance of cluster morphol ogy in determining core-electron binding energies. As-deposited films show a discontinuous dependence of the binding energy on gold content, associate d with a transition from coagulated or partially coalesced clusters to isol ated clusters. In contrast, annealed films exhibit a smooth increase in bin ding energy down to very low gold content. Comparison of the photoemission from annealed clusters deposited on and embedded in the insulating SiO2, as well as clusters deposited on a conducting ITO substrate, was used to high light the contributing factors that determine the core-electron binding ene rgy and line-width, namely: (i) initial-state effects relating to the elect ronic structure, (ii) final-state effects relating to relaxation processes, and (iii) the cluster charge, including the influence of image charge scre ening. (C) 2001 Elsevier Science B.V. All rights reserved.