New Features of X-Ray Bragg Diffraction Topography with Coherent Illumination

Abstract

New features of the X‐ray Bragg diffraction topography with coherent beam and third generation synchrotron radiation sources are described. An experimental set‐up for coherent topography is proposed and used to record images from practically perfect substrates, namely a thin SiO2 film on an InP substrate, and the scratches on the surface of a Si crystal. It is shown that very weak localized deformations can produce contrast up to 70%. Some theoretical estimations to reveal the performance of the proposed technique are made.

Fourier crystal diffractometry based on refractive optics

“…As was shown previously (Kuznetsov et al, 1999), the profiling of the perfect crystal surface results in the binary phase modulation of the wave diffracted by the perfect crystal, and this phase modulation depth depends linearly on the profile depth:…”

“…An estimation of the minimum oxide strip thickness that can be resolved by this Fourier-transform technique can be made in the same way as proposed by Kuznetsov et al (1999). In our experimental arrangement, the diffraction planes are parallel to the oxide ridges, and then the function '(x) describes the phase distribution on the surface across the direction of periodicity:…”

“…A variety of modern imaging techniques such as phase contrast imaging, diffraction microtomography and diffraction topography allow investigations of practically transparent objects in the high-energy X-ray domain (Snigirev et al, 1995;Raven et al, 1996;Hartman et al, 1997;Hu et al, 1998;Drakopoulos et al, 1999;Kuznetsov et al, 1999). Refraction contrast, which is caused by Fresnel diffraction of the transmitted wave, becomes possible while we are using highintensity, well collimated, low-divergence and high-level monochromatic beams.…”

Phase Sensitive X-Ray Diffraction Imaging of Defects in Biological Macromolecular Crystals

“…where w͑r 0 ͒ is the perturbation potential in the effective size of the defect, c is a constant, and k g and k g 0 denote the wave vectors of the unperturbed and perturbed diffracted waves, respectively. The individual defect imaging pattern resembles a Fresnel hologram in general [27]. If the camera is placed in the far field of the defect (but not necessarily in the far field of the whole sample), the intensity distribution may follow…”

Open-faced z-shaped channel-cut x-ray monochromator

“…One possible explanation for this diffraction intensity contrast resembling the texture of the orange-peel surface might be because inhomogeneous etching of the surface leaves small microscopic residual strains that are imaged here. Alternate explanation for the observed diffraction contrast might be that the diffracted x-rays from adjacent regions of the orange-peel, having gone through different path lengths, coherently interfere giving rise to the diffraction contrast resembling the orange-peel morphology [8]. While the exact cause for the observed diffraction contrast is to be yet investigated further, the wet etched monochromator introduce much more significant intensity variation, which is not acceptable for imaging application.…”