Glancing-incidence x-ray fluorescence of layered materials

X-ray fluorescence spectroscopy normally probes the first few micrometers of a material, but under conditions of glancing incidence the surface sensitivity is enlarged to the nanometer regime. In this paper, a formalism is given for the calculation of x-ray fluorescence intensities that is also valid at glancing incidence and includes absorption and enhancement effects. Calculations based on this theory for the angular dependence of glancing-incidence x-ray fluorescence (GIXF) intensities compare well with experimental data. Standing waves in thin layers are shown to be a sensitive probe for elements at various depths, an effect that can be exploited in GIXF for depth profiling in layered materials.