Electron differaction patterns with curved Kikuchi lines
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RACTION AND SCATTERING OF IONIZING RADIATIONS
Electron Diffraction Patterns with Curved Kikuchi Lines R. K. Karakhanyan and K. R. Karakhanyan Yerevan State University, ul. Al. Manukyana 1, Yerevan, 0025 Armenia e-mail: [email protected] Received August 30, 2006
Abstract—Curved Kikuchi lines have been observed in electron diffraction patterns obtained for silicon by transmission electron microscopy. It is found that the curvature of Kikuchi lines is related to the shift of point reflections from their normal positions. The formation of curved Kikuchi lines stems from the local structural defects in the crystals under study. PACS numbers: 61.14.-x DOI: 10.1134/S1063774507050021
According to the elementary mechanism of formation of Kikuchi patterns [1], the bright and dark pairs of Kikuchi lines are two branches of hyperbolas; however, owing to the small value of the Wulf–Bragg angle for fast electrons, they manifest themselves as straight lines in electron diffraction patterns. In this study, we obtained for the first time electron diffraction patterns exhibiting curved Kikuchi lines in addition to conventional straight lines. In our experiments, we obtained electron diffraction patterns from thin silicon crystals prepared by chemical etching of bulk single crystals. Transmission electron diffraction patterns were recorded by an EG-100M electron diffractometer with an accelerating voltage of 100 kV. Figures 1 and 2 show the electron diffraction patterns with Kikuchi lines for two different silicon samples, recorded for the case of incidence of the initial electron beam in the direction close to the [112] axis. In the electron diffraction pattern shown in Fig. 1, all Kikuchi lines, in particular, (4 4 0) and (6 6 0) horizontal lines, are straight, whereas in the electron diffraction pattern in Fig. 2 the bright Kikuchi lines with an excess of 4 4 0 and 6 6 0 have a curved shape. At the same time, the corresponding dark Kikuchi lines with a lack of 4 40 and 6 60 remain straight.
patterns for silicon with curved Kikuchi lines corresponding to both a lack and an excess of relevant reflections. The lines were curved either in the same or opposite directions. The analysis of the observed electron diffraction patterns with Kikuchi lines demonstrated that the curvature of the lines is accompanied by a shift of point reflections. In Fig. 2, the shifted point reflections are indicated by arrows. It is easy to see that the shifted point reflections do not lie in the same straight line. The curved Kikuchi lines corresponding, in particular, to the excess of 4 4 0 and 6 6 0 always pass through the areas in electron diffraction patterns where shifting of point reflections occurs. The larger this shift, the larger the curvature of the Kikuchi line. At the same time, straight Kikuchi lines, for example, the ones corresponding to a lack of 4 40 and 6 60 (Fig. 2), always
Note that the electron diffraction patterns with curved lines were also obtained for the other silicon samples, with the electron beam incident in different c
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