ION VERSUS NEUTRAL IRRADIATION OF THIN-FILMS OF AMORPHOUS SIO2 - AN IN-SITU X-RAY PHOTOELECTRON-SPECTROSCOPY STUDY

In this paper we present the results of an X-ray photoelectron spectro scopy study on thin films of amorphous SiO2 bombarded with neutral or ionic (positive) Ar beams at keV energy. All the bombardments have bee n performed inside the preparation chamber of the XPS spectrometer so that the samples have been compared before and after the irradiation w ithout exposing the surface to the air. Moreover, particular care has been taken in measuring the flux of the neutral beam. This measurement has been performed utilising the secondary electrons ejected by the s urface of the metallic support of the sample, so that the comparison b etween the effects induced by neutral and ionic bombardment is made at thr, same fluence, This in situ comparison allowed us to conclude tha t for bombardment of SiO2 with ions or neutrals, the detected XPS modi fications are almost identical, within the experimental error, for bot h kinds of beam, This finding is at variance with recent studies claim ing different behaviour of the SiO2 depending on the charge state of t he bombarding beam, Possible explanations for this discrepancy are dis cussed.