GIMOXS: A Versatile GI/TXRF Spectrometer for Characterization of Nanomaterials in the Lab from C to U

Abstract

GIXRF in comparison to TXRF increases the incident angle of a monochromatic low-divergence exciting beam from zero up to several times the critical angle, thereby varying the penetration depth and the beam interferences. The obtained measurement data contain information on composition, density, and thickness of layers in the nanometer range, depth distributions of implanted atoms (especially if combined with X-ray reflectometry (XRR)) or the size and composition of nanoparticles. The sensitivity for the elements depends strongly on the excitation energy, thus the Grazing incidence modular X-ray spectrometer (GIMOXS) was designed to use a Cr anode X-ray tube for light elements down to Carbon and a Mo anode for heavier elements. In both cases the beam is monochromatized and parallelized by a suitable 1-dimensional parallel beam multilayer X-ray optics. In order to keep the setup modular and flexible, the optics assembly is housed in a separate vacuum chamber, which is connected by standard KF-flanges to the vacuum chamber containing the sample. Apart from the small X-ray fluorescence cross section of light elements, i.e., elements below Magnesium, which can be mitigated by using a Cr X-ray tube, the analysis of light elements, poses significant other challenges. The high absorption of the produced low-energy X-ray photons in air has to be eliminated by using vacuum conditions also in the sample chamber. The natural limitation of the low X-Ray fluorescence and high Auger-Meitner electron yield has to be accepted. In order to reduce the absorption for low energy X-rays in the detector window, the detector is equipped with an ultra-thin SiN window as well as an optimized electron trap.