SU1133520A1 - Radiographic method of investigating structural perfection of monocrystals - Google Patents

Abstract

1. The X-ray diffraction method for studying the perfection of single crystals, by which a ribbon-like X-ray beam is directed onto a fixed single crystal under study and recorded behind it is a sectional v diffraction pattern, which is aimed at expanding the informativity of the research as a test monocrystals use a stepped mono-: crystal and obtain additional information about the structural perfection of the nc single crystals according to the magnitudes of the shift and the difference in the width of the lines diffracted by GOVERNMENTAL portions of different thickness of the single crystal under study are employed.

Description

Fig. 1 2, An X-ray diffraction method for examining the structural perfection of single crystals, by which a ribbon-like X-ray beam is directed onto a fixed single crystal under study and registering a sectional diffraction pattern behind it, characterized in that, in order to expand the informativity of the study, a ribbon-like 120 beam is simultaneously directed oriented identical to the test monocrystal, the thickness of which is different from the thickness of the investigated single crystal, and additional inform tion of the structural perfection of the investigated single crystals. la is obtained from the values of the shift and the difference in the width of the lines diffracted by the test and control single crystals.

The invention relates to X-ray graphical diagnostics of crystal imperfections and is intended to study the structural perfection (degree of mosaic) of single crystals. A known method for studying the structural perfection of single crystals by X-ray topography, which means that an X-ray beam is directed at the monocrystal under study and a diffraction pattern is recorded behind the monocrystal under investigation, which is judged by its structural pattern during the movement of the single crystal and X-ray film. Using this method, depending on the density of defects, a picture of the distribution of imperfections in the crystal M is obtained. However, this method does not show the total deviation from the ideal structure. The closest technical solution to the invention is the method of studying structural perfection of single crystals, which consists in the fact that a ribbon-like X-ray beam is directed onto a fixed single crystal under investigation and a sectional diffraction pattern is recorded behind it 2. The disadvantage of this method is that it does not allows you to determine when, depending on the degree of perfection of the crystal, the kinetic scattering in it goes into dynamic, when the Borrmann effect arises and how it depends t from: the degree of perfection of the crystal. The purpose of the invention is to expand the information content of the study. The goal is to achieve that, according to the X-ray diffraction method for studying the structural perfection of single crystals, the idea is that a ribbon-like X-ray beam is directed onto a fixed single crystal and a sectional diffraction pattern is recorded on it, a stepped monocrystal is used to obtain a single crystal and receive additional information on the structural perfection of a single crystal by the magnitudes of the shift and the difference in the width of the lines diffracted by with different thicknesses of the monocrystal under study. According to the second variant, the ribbon-like beam is simultaneously directed to the control single crystal oriented identically to the investigated one, the thickness of which is different from the thickness. the monocrystal under study, and additional information on the structural perfection of the monocrystal under investigation is obtained from the shear and difference widths of the lines diffracted by the test and control single crystals. FIG. 1 and 2 show two cases of radiation falling on a stepped single crystal; in fig. 3 and 4 — the course of the rays in the kinematic (mosaic single crystal) and dynamic (perfect single crystal) scatterings; in fig. 5-12 - diffraction of rays in stepped mosaic and perfect single crystals.

For the implementation of the method, a parallelepidoidal stepped single crystal (Fig. 1) can be manufactured.

In order to explain the proposed method, let us consider the X-ray diffraction in mosaic and perfect step crystals. We investigate the diffraction of a ribbon-like nazdanny beam on a stepped crystal in two cases: the primary beam falls from the smooth side of the single crystal (figure 1 the primary beam falls from the step side of the single crystal (figure 2).

In the case of a ribbon-like incident beam, the cross section of the beams diffracted in stepped mosaic and perfected single crystals will have the form shown in FIG. 5-12, where indicated. stepped single crystal 1, primary beam 2, cross section 3 of a diffracted beam, when the primary beam falls from the smooth side, cross section 4 of a diffracted beam, when

; the primary beam falls sidewise.

The cross sections of beams diffracted in mosaic and perfect single crystals are significantly different from each other. In perfect single crystals, parts of the beams diffracted in thin and thick sections of the same perfect single crystal are shifted relative to each other. In addition, the Bormann effect occurs and dynamic dispersion takes place. In mosaic monocrystals, these parts are not shifted relative to each other, but they differ in width: the part diffracted in the thin part of the single crystal is narrower than the part diffracted in the thick part. Meanwhile, in the case of a perfect single crystal, the width of these parts is the same.

Thus, it can be concluded that when dynamic scattering occurs in a single crystal (co, perfect single crystal), the parts of the beam diffracted in portions of a single crystal of different thickness, i are the same across the width, but shifted relative to each other; when kinematic scattering occurs in a single crystal (a mosaic single crystal), parts of the beams diffracted on the portions of a single crystal of different tolicy are

the widths are different, but not shifted relative to each other.

Consequently, by the magnitude of the shift and the difference in the width of the lines diffracted at different steps of a single crystal, one can judge the degree of its perfection.

Let us denote the width of the lines of reflections diffracted in thin and thick parts of a single crystal under dynamic scattering, through LD and LL, and with kinematic scattering through, and U,. Then, using FIG. 3 and 4 for ideally mosaic and ideally perfect single crystals, we find the following relations:

, 4) 5i "Qi (O

4 (-L (d.0. (2

So far, cases of ideal mosaic and ideally perfect mini crystals have been investigated, but real single crystals differ from both ideally mosaic and ideally perfect single crystals.

For real single crystals, expressions (1) and (2) take the form

2 (ez-c, bi-yiei

(3)

Uq 0. (four)

In expressions (1) - (4), Bj is the thickness of a thin portion of a single crystal; 1 - thickness of the thick mono- section. crystal; 9 - Wolfe Brzgga angle. : In the case of mosaic single crystals with a difference of 2 (2 С «) Sin6- u | j, it is possible to estimate how much a single crystal under study is from an ideal mosaic: an original, and in the case of perfect single crystals with a difference L - UQ, it is possible to estimate how much a single crystal under study is different from ideally perfect.

As a trial, a step system was used (Fig. T), which was made of silicon and quartz monocrystals. 6 thick and 62 thin parts of a single crystal were equal, respectively 4 and 2 mm for quartz and for silicon. Used radiation MD If j.

The tape-like X-ray beam was directed at the Wulff-Bragg angle to the reflecting planes (110) and (1120) for silicon and quartz, respectively. 51. In the obtained diffraction pattern for silicon single crystal, the single crystal under study is imperfect (there is no Borman effect, kinematic scattering occurs). In the diffraction pattern for single crystal AC quartz - Aq, and the shift of diffraction lines was obtained, i.e. the monocrystal under study is perfect (dynamic scattering occurs). The invention makes it possible to study the nature of the interaction of diffracted waves in a crystal depending on the degree of perfection of the crystal and to solve the inverse problem — to estimate the average perfection of the crystal using a diffraction pattern obtained outside the crystal. The magnitude of the displacement of the two parts of the diffraction line relative to each other determines the direction of the fluxes of diffracted waves inside the crystal and, thus, determines the degree of perfection of the crystal. Another option is possible. A stepped single crystal may consist of two completely identical single crystals, differing only in thickness from each other. One of the monocrystals (thin or thick) is taken as the control, and the other as the test. First, the control single crystal is adjusted (brought into the reflection position), and then the monocrystal under investigation is installed on it, which, by rotating the goniometer mounted above, is also brought into the reflection position. That is how a step is formed. The second option is more difficult due to difficulties with the adjustment of the investigated single crystal, but in this case there is no need to make the investigated single crystal stepwise and, moreover, you can use a single crystal with a known degree of perfection as a control. The proposed method in both variants of its implementation makes it possible to increase the information content of the X-ray diffraction study of the structural perfection of single crystals.

Fig.Z

I /

5

Fig.b

FIG. 9

FIG. YU

M

FIG. 71

FIG. 72

Claims (2)

one . X-ray method for studying the perfection of single crystals, in which a ribbon-like beam of x-ray radiation is sent to a stationary subject " tall and register for it a new diffraction pattern, which often means that, expanding the informativeness of the monocissection _ν about the purpose of research2. X-ray engineering. Directory. Book 2. Ed. V.V. Klyueva. M., Engineering, 1980, p. 119 (prototype). As a studied single crystal, a stepped single crystal is used and additional information on the structural perfection of the single crystal is obtained from the shift values and the difference in the line widths diffracted by sections of different thicknesses of the studied single crystal. FIG. one 2. X-ray diffraction method for studying the structural perfection of single crystals, according to which a ribbon-like x-ray beam is directed to a stationary test single crystal and a sectional diffraction pattern is recorded behind it, characterized in that, in order to expand the information content of the study, the ribbon-like beam is simultaneously sent to a control single crystal oriented identically to the studied, the thickness of which is different from the thickness of the investigated single crystal, and additional information about the jet The structural perfection of the monocrystal under study is obtained from the values of the shift and the difference in the line widths diffracted by the studied and control single crystals.