Electron microscopy and diffraction of twinned structures in evaporated films of gold

Abstract

Transmission electron microscopy and diffraction have been used in a study of single crystal and polycrystalline gold films prepared by evaporation. The specimens include films in (001) orientation containing many {111} microtwins, and films in (111) orientation having a pronounced twin related double positioning structure. The electron diffraction patterns from these films contain some well-known anomalous spots which are not immediately interpreted in terms of the twinning. Dark field electron microscopy reveals that in the (001) film the extra spots arise from the twin boundaries, and that double diffraction is an adequate and likely explanation of their origin. Similarly, the anomalous spots from the (111) films arise from the double positioning boundaries, but double diffraction does not provide an adequate explanation in this case, and the effect of the imperfect nature of the double positioning boundary is considered to be important. Extra rings observed on polycrystalline diffraction patterns can be explained in terms of the effects at twin boundaries, and it is considered that previous interpretations of these extra rings in terms of the presence of hexagonal close-packed metal are not justified.