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The nature of 〈111〉 twist boundaries obtained in thin Au bicrystals is discussed and compared with previous results of Tan et al. employing a different method of preparation. Using transmission electron microscopy the present method permits the in‐situ observation of the generation of dislocation networks in boundaries close to a coincidence site lattice orientation, Particular attention is paid to the unexpected contrast of dislocation networks in boundaries deviating slightly from the twin orientation.

The in situ relaxation of near‐concidence boundaries and structures of exact coincidence boundaries in thin gold bicrystals containing [111] twist boundaries are studied. A previously suggested procedure is applied to the analysis of electron diffraction patterns from such bicrystals obtained with the incidence beam parallel to the rotation axis. It is shown that diffraction patterns of unrelaxed near‐coincidence boundaries can be analysed completely in terms of double diffraction. During relaxation extra reflections emerge that can be ascribed to the generation of secondary grain boundary dislocation networks. In diffraction patterns of exact coincidence boundaries with hexagonal symmetry it is found that spots are present at positions of the reciprocal coincidence lattice points that cannot be caused by double diffraction in the zero order Laue zone. These reflections are due to diffraction from the coincidence lattice in the bicrystal.

An apparatus for vacuum evaporation of metals at pressures in the 10−8 Pa range is described, the essential part of which consists of a liquid nitrogen cooled furnace. This device enables evaporation of metals at a residual pressure of 2×10−8 Pa.