Artefact formation in scanning photoelectron emission microscopy

The fast developing analytical technique, synchrotron radiation scanning photoemission spectromicroscopy has opened the opportunity for probing surface processes and composition of materials on a submicron spatial scale. Here we describe some artefact and unforeseen phenomena that can occur when a photon flux with high intensity is focused onto a microspot. Using as examples selected data obtained recently with the scanning photoemission microscope built at the ultrabright synchrotron source ELETTRA we illustrate the possible effects of surface morphology and undesired processes, such as photon-assisted carbon deposition, heat dissipation, charging and photon-induced reduction of the sample. All these events can cause severe changes in the chemical maps and photoelectron spectra and provide misleading results. The physical nature of the artefacts are outlined and discussed, as well as the possibilities to reduce their influence or to use them for quantification of some photon-induced phenomena becoming important in spectromicroscopy experiments carried out at the third generation synchrotron sources. (C) 1998 Elsevier Science B.V. All rights reserved.