Comparison of reference-free X-ray fluorescence analysis and X-ray reflectometry for thickness determination in the nanometer range

X-ray reflectometry is the method of choice to determine the thickness of nanolayered systems with small uncertainties. In view of known limitations of this method for extremely thin or laterally inhomogeneous layers we compared X-ray reflectometry with fundamental parameter based X-ray fluorescence analysis using synchrotron radiation in the radiometry laboratory of the PTB. The results of both methods for a set of sample systems with transition metal layers of various thicknesses deposited on silicon wafers were compared and showed a good agreement within their respective uncertainties. For the investigation of layered systems both methods are very appropriate and, in addition, can give complementary information about the layers. Thus, the density is determined by X-ray reflectometry, and X-ray fluorescence analysis gives information about trace elements within the layers and the layer homogeneity.