The diffraction focusing of X-rays upon backscattering from a bent crystal covered with epitaxial film: Sensitivity with respect to the interplanar spacing mismatch between film and substrate

Abstract

The diffraction focusing of an X-ray wave reflected from a thick bent crystal covered with an epitaxial film is theoretically studied in the case when the Bragg angle θB is close to π/2. It is shown that the X-ray wave focusing upon backscattering from this system is sensitive with respect to the relative interplanar spacing mismatch Δd/d between the epitaxial film and the thick crystal substrate. It is suggested that this effect can be employed for evaluating Δd/d with an accuracy on the order of 10−10.