Abstract

Fast electrons scattered from polished metal surfaces do not form diffraction patterns. A strong Debye-Scherrer pattern is produced, however, by electrons scattered from a surface which has been mechanically roughened in such a manner that electrons are able to pass directly through projecting irregularities. Small ridges extending from wires, which have been drawn through an imperfect die, also give rise to a diffraction pattern. These experiments indicate: (1) that there is no considerable layer of amorphous material (Beilby layer) on a polished metal surface, and (2) that Debye-Scherrer diffraction patterns are formed only by transmitted electrons. Fast electrons scattered at a small glancing angle from an etched polycrystalline surface form a diffraction pattern if the surface appears mat or roughened, but no pattern is formed if the surface shows metallic luster. Here again diffraction patterns appear to be produced only by transmission. A probable explanation is given for the fact that diffraction rings are not formed by electrons scattered from smooth polycrystalline surfaces.

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