Total Electron Yield Detector Working at Low Temperature for Linear Dichroïsm Studies on Monocrystalline Samples

Abstract

Electron detection in EXAFS is commonly used at room temperature for thick samples (where transmission measurements are not possible) or nanostructures with high element concentrations (where fluorescence detection is not appropriate). Recently, a Total Electron Yield detector with He gas flow at atmospheric pressure working at liquid nitrogen temperature has been developed and successfully tested on the French CRG/IF beamline at ESRF. At 80 K, the substantial decrease of the dynamic part of the Debye-Waller (DW) factor enables to record EXAFS signals on a larger k range and hence to obtain better signal-to-noise ratio of the corresponding Fourier Transform. A variation of the temperature of the sample from 80 to 300 K can be performed to evaluate the vibrational and the structural part of the DW factors. Moreover, in order to get rid of Bragg peaks in the EXAFS signal in case of monocrystalline samples, a special 360° rotating sample holder has been designed. Finally, polarization studies for anisotropic systems may be realized by simply rotating the sample holder by 90° from the in-plane to the out-of-plane polarization sample geometry.