SU1673933A1 - Method of studying crystals with x-ray interferometry - Google Patents

Abstract

The invention relates to the field of radiographic studies of imperfections of crystals, in particular for the study of deformation fields in crystals caused by the imperfection of their structure. The aim of the invention is to increase the informativity of the spatial orientation studies and the volume distribution of deformation fields in crystals having a fourth-order symmetry axis. The method consists in making the interferometer so that the fourth-order symmetry axis is perpendicular to the input surface of the interferometer. Then, X-ray topographic interference patterns are obtained from two complanar systems of planes parallel to the mentioned axis of the fourth order, and judging from the obtained patterns, the perfection of the crystal is judged. 2 Il.

Description

The invention relates to X-ray diffraction studies of crystal imperfections, in particular, for examining deformation fields in crystals caused by imperfections of their structure.

The aim of the invention is to increase the informativity of the spatial orientation studies and the volume distribution of deformation fields in crystals having a fourth-order symmetry axis.

FIG. Figures 1 and 2 show the diffraction scheme in two-crystal and three-crystal interferometers, in which the fourth-order symmetry axis is perpendicular to the input surface of the crystal. In this case, the rotation of the interferometer, located in

The position of the Bragg diffraction relative to the mentioned axis by 90 ° allows one to obtain two interference patterns from one sample from coplanar systems of (110) and () crystallographically equivalent planes.

The method for producing two interference patterns has the following advantages over conventional interferometry and X-ray topography methods.

First, during projection topography, spatial images of crystal imperfections are projected on a plane (on an x-ray film or plate), and the three-dimensional spatial pattern turns into

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two-dimensional flat picture. Moreover, diffraction images of defects located in different depths of the crystal, but giving an image in the same diffracted beam (in the same direction), are often projected onto each other.

These circumstances, which are caused by the limited capabilities of conventional X-ray diffraction projection topography, significantly reduce the spatial and linear resolution of topograms.

The displacement of scatterers (motive atoms) in reflecting planes does not lead to additional phase differences between the waves scattered by adjacent planes in the direction of the observation point. Diffraction images are in fact pictures of such defects (or parts thereof) that cause displacements in the direction of the normals of the reflecting planes. Thus, the usual diffraction images of the imperfections (defects) contained in the diffracted beams, even before their design, are not complete - they mainly represent pictures of the deformation fields that have arisen in the direction of the normal of the reflecting planes,

In X-ray interferometric studies, in addition to those listed, the recorded diffraction images (moire patterns) strongly depend on the direction of rotations of the reflecting planes caused by imperfections of interferometer crystals, on the nature of the change in the interplanar spacings of the reflecting planes, from both absolute and relative locations. interferometer. If, in the case of a separate crystal, the relative position of the Burgers and diffraction vectors plays the main role in the formation of the diffraction image, there are many such decisive factors in the interferometric formations of the diffraction patterns.

Therefore, in order to more or less completely resolve the issue of stereometric projection interferometry, it is necessary to use several symmetrically equivalent families of reflecting planes that make up relatively large angles between them.

An example implementation of the method.

Two- and three-crystal interferometers were fabricated from a highly advanced silicon single crystal, according to the geometry presented in Figures 1 and 2.

Interference topograms were obtained from both interferometers for the (220) and (220) plane systems.

The topograms showed that the reflection 220 in a two-crystal interferometer detects only the displacement lines, and the reflection 220 detects both the displacement lines and the segregation lines.

Topograms obtained from a three-crystal interferometer showed the presence of a dislocation in the interferometer.

A simple topographic method was used to determine the type and location of dislocations. In order to clarify in which block the dislocations are located, as well as their type, the topograms were obtained after the first, second and third crystals, when the primary wave fell on the first crystal, having previously closed (delayed) it after passing through the first crystal, yupograms were obtained after the first, stout and third crystals, when the primary wave fell on the third crystal, having previously closed it after passing through the third crystal, topograms were obtained after the third, second and first crystals. When the primary wave falls on the first crystal, the image of dislocations is obtained both after the first and after the second and third crystals, and when the primary wave falls on the third crystal, the image of dislocations is obtained only after the first crystal.

Thus, it was shown that dislocations in the interferometer are present only in the first crystal (block).

Claims (1)

The invention X-ray interferometric method for studying crystals, which consists in producing an interferometer from the crystal under study, directing an X-ray characteristic radiation beam at a Bragg angle to reflecting its planes, scanning the interferometer in a direction parallel to the diffraction vector, and registering an interference pattern that differs. in order to increase the informativity of spatial orientation studies and the volume distribution of deformation fields in crystals having a fourth-order symmetry axis, the interferometer is cut out during manufacturing so that the fourth-order symmetry axis of the investigated crystal is perpendicular to the input surface of the interferometer, turning the interferometer about the specified axis on 90 °, an additional interference pattern from a crystallographically equivalent system of planes is recorded and The obtained pictures are judged on the spatial distribution of the deformation fields in the crystal. Fm.1 FIG.