Recently variable sample exit-angle x-ray fluorescence spectrometry (VEA-XRF) has been shorn to be a useful analytical tool for monitoring the oxidation of the surfaces of bulk Cu, Ni as well as that of Fe. In these studies advantage was taken of the well known phenomenon that for each transition metal oxide (MO) Lβ/Lα intensity ratio value is higher than for the transition metal (M), itself. Within the limits of the photon-escape depth de, which for these photons are generally below 5000 Å, varying the sample exit-angle θ offers an opportunity for seeing whether or not the oxidation of the surfaces of bulk M belongs to one of the following two classes: (I) uniform oxidation throughout the entire observable sample-depth, (II) preferential oxidation of the top surface layer, i.e. depth dependent oxidation.
Grazing Incidence X-ray Fluorescence Spectrometry and Reflectrometry with Synchrotron Radiation. A New Tool for Characterization of Thin Films.