Interference fringes in multiple Bragg-Laue mode and mirage fringes from bent crystals

Interference fringes are measured in the diffraction from the surface as well as from the lateral surface of an Si single-crystal strip which is deformed in cantilever bending as a function of the tip displacement. The interference fringes are observed only when the bending strain is applied. Both interference fringes change conspicuously by increasing the bending strain. The number of the interference fringes changes, and the positions and heights of the peaks in the fringes change. These variations can be explained by the change of the interference between the beams in multiple Bragg-Laue modes and those of mirage diffraction based on the dynamical theory of diffraction.