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 nondestructive, 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_α,β 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° and 12°, 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.