Exotic X-ray back-diffraction: a path toward a soft inelastic X-ray scattering spectrometer

• Published in: Journal of applied crystallography 2014-09, Vol.47 (5)
• Main Authors: Hönnicke, Marcelo Goncalves, Conley, Raymond, Cusatis, Cesar, Kakuno, Edson Massayuki, Zhou, Juan, Bouet, Nathalie, Marques, Joao Basso, Vicentin, Flavio Cesar
• Format: Article
• Language: English
• Subjects: INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
• ISSN: 1600-5767; 1600-5767
• DOI: 10.1107/S1600576714018147

In this work, soft X-ray back-diffraction (XBD; X-ray diffraction at angles near and exactly equal to 90°) is explored. The experiment was conducted at the SXS beamline at Laboratorio Nacional de Luz Sincrotron, Brazil, at ~3.2 keV. A high-resolution Si(220) multi-bounce back-diffraction monochromator was designed and constructed for this experiment. An ultra-thin Si(220) crystal (5 µm thick) was used as the sample. This ultra-thin crystal was characterized by profilometry, rocking-curve measurements and X-ray topography prior to the XBD measurements. It is shown that the measured forward-diffracted beam (o-beam) profiles, taken at different temperatures, are in close agreement with profiles predicted by the extended dynamical theory of X-ray diffraction, with the absence of multiple-beam diffraction (MBD). This is an important result for future studies on the basic properties of back-diffracted X-ray beams at energies slightly above the exact XBD condition (extreme condition where XBD is almost extinguished). Also, the results presented here indicate that stressed crystals behave like ideal strain-free crystals when used for low-energy XBD. This is mainly due to the large widths of XBD profiles, which lead to a low strain sensitivity in the detection of defects. This result opens up new possibilities for mounting spherical analyzers without degrading the energy resolution, at least for low energies. This is a path that may be used to construct a soft inelastic X-ray scattering spectrometer where different applications such as element-specific magnetic imaging tools could be explored.