On the Extra Reflections in Electron Diffraction Patterns from Thin Evaporated Films of Some of the Face-centred Cubic Metals

Polycrystalline thin films of a number of face-centred cubic metals have been prepared by evaporation on to rock-salt, followed by annealing. In a number of cases, transmission electron diffraction patterns show, in addition to the normal face-centred cubic rings, some extra rings which fit well with those which would be expected from a hexagonal close-packed form of the metals. No hexagonal close-packed rings are observed with aluminium films, and this is correlated with the absence of stacking faults on transmission electron microscope images of aluminium films.