Validity of the method for quantitative XPS of surface nano-structures: application to Cu/Au/Cu

Abstract

The validity of the software packet QUASESTM, developed by Tougaard et al., for quantitative analysis by XPS of nano-scale surface structures is considered. We study the ability of the software to consistently determine the same amount of Au atoms within the surface region of a series of solids where the depth distribution of a fixed number of Au atoms is varied. The sets of samples were produced by first evaporating a few monolayers of gold onto the surface of a polycrystalline copper sample and then evaporating varying amounts of copper on top. A synchrotron radiation source is used to produce the photons. For two series of samples where the measured Au 4d peak intensities vary by a factor of 10, the quantitative amount of gold determined by this formalism is found to be constant to within an RMS deviation of 7% and 15%. When the spectra from the same set of samples using photons of 950 and 750 eV energy are analyzed, the RMS deviation in the total number of gold atoms is ∼ 20%.