Effect of twisting of the diffraction net planes on the integral intensities at Laue diffraction of X-rays in elastically bent silicon crystals

Abstract

The values of the Laue-diffracted beam integral intensities (LDBII) IR in K.M. SHEXTSOV-KAZMIRCHUK elastically bent crystals with cylindrically bent reflecting planes may be well described by the generalized eikonal theory /l/. In practice, however, the non-cylindrical bending of atomic net planes can often take place for example, at complex bending of epitaxial structures, in unfixed (free) crystals taking into account the elastic anisotropy /2/. It is also known /3/ that even a weak twisting of diffraction planes leads to an essential change of the image contrast of extinction contours in the section topograms obtained from elastically bent crystals /3/. The problem concerning the influence of non-cylindrical bending of the reflecting planes on LDBII has been studied neither theoretically nor experimentally till now. This note presents the results of an experimental study of the influence of twisting of the diffraction planes on the dependence of LDBII IR at elastic strain level E .The values of IR have been measured by means of a double-crystal spectrometer. The plane-parallel samples were prepared from dislocation-free silicon crystals in which diffraction planes {ll 0) were deflected from the n o r q a l to the surface by an angle Y = 2 ' .The sample thickness t was 400 pm. The MoK, and FeKa radiations were used which provided the approximations of thin (pt = 0.58) and thick (pt = 11) crystals, respectively (here )I is the normal coefficient of photoelectric absorption). The four-point loading scheme was used for mechanical bending of crystals /4/. Sample twisting was performed in a special unit by displacement of one of the fixed points of the supporting knives. According to /3/, twisting of the diffraction planes normal to 1) prospekt Nauki 115, 252650 Kiev 28, USSR.