Laboratory Setup for Scanning-Free Grazing Emission X-ray Fluorescence

Grazing incidence and grazing emission X-ray fluorescence spectroscopy (GI/GE-XRF) are techniques that enable non-destructive, quantitative analysis of elemental depth profiles with a resolution in the nanometer regime. A laboratory setup for soft X-ray GEXRF measurements is presented. Reasonable measurement times could be achieved by combining a highly brilliant laser produced plasma (LPP) source with a scanning-free GEXRF setup, providing a large solid angle of detection. The detector, a pnCCD, was operated in a single photon counting mode in order to utilize its energy dispersive properties. GEXRF profiles of the Ni-L-alpha,L-beta line of a nickel-carbon multilayer sample, which displays a lateral (bi)layer thickness gradient, were recorded at several positions. Simulations of theoretical profiles predicted a prominent intensity minimum at grazing emission angles between 5 degrees and 12 degrees, depending strongly on the bilayer thickness of the sample. This information was used to retrieve the bilayer thickness gradient. The results are in good agreement with values obtained by X-ray reflectometry, conventional X-ray fluorescence and transmission electron microscopy measurements and serve as proof-of-principle for the realized GEXRF setup. The presented work demonstrates the potential of nanometer resolved elemental depth profiling in the soft X-ray range with a laboratory source, opening, for example, the possibility of in-line or even in situ process control in semiconductor industry.