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 O2 atmophere 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 proof that the fraction of implanted Ge, with 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 (XTEM) images, could be identified by XPS, in combination with data analysis by factor analysis, to consist mainly of elemental Ge and GeO2, respectively.