Full-Field Fluorescence Mode Micro-XANES Imaging Using a Unique Energy Dispersive CCD Detector
2014
Tack, Pieter | Garrevoet, Jan | Bauters, Stephen | Vekemans, Bart | Laforce, Brecht | Van Ranst, Eric | Banerjee, Dipanjan | Longo, Alessandro | Bras, Wim | Vincze, László
X-ray absorption near-edge structure (XANES) spectroscopy is a well-known nondestructive technique that allows for chemical state and local structure determination. Spatially resolved oxidation state imaging is possible performing full-field transmission mode XANES experiments, providing chemical state information on the illuminated sample area, but these experiments are limited to thin, concentrated samples. Here we present the use of a unique energy dispersive (ED) pnCCD detector, the SLcam, for full-field fluorescence mode XANES experiments, thereby significantly relaxing the constraints on sample thickness. Using this new detection methodology, spatially resolved chemical state information on millimeter-sized sample areas can be obtained with microscopic resolution in moderate measuring times (less than 15 h), obtaining a XANES profile for each of nearly 70 000 points in a single measurement without the need of scanning the sample through the beam. Besides a description of the use of this detector for micro-XANES applications, we also present the proof of concept for fluorescence mode micro-XANES using a Fe⁰/Fe₂O₃ model sample and a Nitisol soil sample, which was measured to obtain iron chemical state distribution information.
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