New features of X-ray Bragg diffraction topography with coherent illumination

New features of the X-ray Bragg diffraction topography with coherent beam a nd third generation synchrotron radiation sources are described. An experim ental set-up for coherent topography is proposed and used to record images from practically perfect substrates, namely a thin SiO2 film on an InP subs trate, and the scratches on the surface of a Si crystal. It is shown that v ery weak localized deformations can produce contrast up to 70%. Some theore tical estimations to reveal the performance of the proposed technique are m ade.