SU1469401A1 - Method of optronic studies of crystal defects - Google Patents

Description

Thebes. one

This invention relates to physical methods for studying the real structure of crystals by diffraction methods.

The purpose of the invention is to improve the detection of defects and the productivity of research.

Fig. 1 is an optical diagram of a device for forming an electron-optical image; Figures 2-5 show the results of densitometry of microphotographs obtained at different depths of modulation.

The method is carried out as follows.

A beam of 2 accelerated electrons is directed onto test sample 1. Behind sample 1 there is an objective lens 3 and an annular diaphragm 4 mounted along the axis of the beam passing through the sample 1. The electron-optical image is formed in the image plane 5. The dimensions and location of the diaphragm 4, taking into account the focal distance f of the objective lens 3, are chosen so that the diaphragm 4 separates the diffracted beams equidistant from the transmitted beam. The control signal of the objective lens 3 modulates the harmonic oscillation with a frequency of 10-40 Hz, which causes periodic defocusing of the selected diffracted beams and the diffuse background with a modulation depth. The resulting electron-optical image is converted into a video signal, which is subjected to synchronous amplification and detection at the modulation frequency of the control signal of the objective lens 3. The resulting signal is converted in the usual way into an image of the sample structure, which is recorded, for example, on photographic film

Example. The studies were carried out on an electron microscope with an accelerating voltage of 100 keV on a 200-A sample of silicon, when it was illuminated along the crystallographic direction llll. The diaphragm was carried out using an annular diaphragm with an inner diameter of 0.2 Å and an outer diameter of 1.7 где where b is the parameter of the silicon crystal back lattice. At the same time, there were six. Diffracted beams, corresponding to reflexes of type 112.

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Focusing was carried out by modulating the focus control signal using a harmonic (sinusoidal) oscillation generator with a frequency of 30 Hz. The video signal of the image of the sample structure after synchronous detection and amplification at a frequency of 30 Hz was applied to a graphic display on which a contrast image of defects was clearly observed. The total crystal research time was no more than 3 min.

Figure 2-5 shows the results of densitometry micrographs, which are obtained at depths f of

ABOUT

The pulses are from 80 to 200 A and on which the solid lines show the image intensity from the real (defect-free) crystal, and the dotted lines show the ideal (defect-free) crystal. The results show the presence of a noticeable contrast between the images of real and ideal crystals, which allows the image associated with structural defects to be selected.

Claims (1)

Invention Formula The method of electron-optical investigation of crystal defects, which consists in scanning the sample with an accelerated electron beam, diaphragming the transmitted and diffracted beams and the diffuse background, forming the electron-optical image, converting the electron-optical image into a video signal, and forming an image of the sample structure based on the video signal, which differs from the fact that, in order to increase the detection of defects and the productivity of research, the diaphragmization is carried out with the help of Aperture diaphragm with diffracted beams equally spaced from the transmitted beam axis periodically defocuses the diffuse diffuse background beams and diffuse background by frequency modulation of the focus control signal, and prior to imaging the sample structure, the video signal is synchronously amplified and the video signal is detected at the modulation frequency control signal. Thebes. 2 (f 1201 FIG. fy Fi.Z (f no. FIG 5