A novel thick-layer electrochemical cell for in situ X-ray diffraction.

Abstract

In this article we describe an electrochemical cell allowing x-ray diffraction from the working electrode in situ. The key feature of our novel design is a hemispherical fused silica dome serving as the x-ray window. The electrode is covered with a thick layer of electrolyte during the x-ray measurement, avoiding mass transport limitations inherent to common setups, where the thickness of the electrolyte layer is strongly reduced for the diffraction experiment. This allows in particular the monitoring of electrode processes which are associated with the consumption of species from solution and/or generation of a significant amount of reaction products. All solid angles in the hemisphere above the sample surface are accessible for the incoming and outgoing x-ray beam at a constant path length in the electrolyte. Thus, our cell is perfectly suitable for in situ surface x-ray diffraction, truncation rod scattering, and specular reflectivity measurements. We demonstrate the performance of the new cell by monitoring the electrochemical stripping of a 50 nm thick amorphous As layer on GaAs(001) in 0.5 M H22SO44 in situ with x rays