XPS investigation with factor analysis for the study of Ge clustering in SiO2

The change of the depth profile and chemical bond character of Ge in Ge+ ion-implanted SiO2 layers during annealing in an O2 atmosphere has been studied by x-ray photoelectron spectroscopy (XPS). The Ge depth profiles in as-implanted and annealed samples as measured by XPS are in agreement with profiles measured by Rutherford backscattering spectroscopy (RBS). At interfaces, XPS gives more information about the Ge depth distribution than RBS. Thus, other than RBS, XPS could prove that the fraction of implanted Ge, which moves during annealing to the SiO2/Si interface region, resides on the Si side of this interface. Additionally, the high- and low-contrast nanoclusters in Ge-implanted samples, which have been found recently in cross-section transmission electron microscopy images, could be identified by XPS, in combination with data analysis by factor analysis, to consist mainly of elemental Ge and GeO2, respectively. Copyright © 2000 John Wiley & Sons, Ltd.