Lattice Images of Non-Integer Planes in Gold
A common growth habit for gold microcrystals is a thin (111) platelet of hexagonal or trigonal symmetry. It has been shown that such microcrystals contain coherent faults in the ABCABC stacking sequence giving rise to non-zero structure factors for lattice planes of index 1/3(422). Transmission electron diffraction patterns from these crystals such as shown in Figure 2 confirm the existence of this non-zero structure factor by exhibiting reflections whose spacing and orientation correspond to lattice planes of the type 1/3(422). The diffraction pattern in Figure 2 has been superimposed on the polycrystalline ring pattern of gold for reference and the spacings of the inner-most spots is equal to the 2.497Å of the 1/3(422) planes to within the experimental error. Additional confirmation of the indexing of these spots has been obtained by electron diffraction at various angles of tilt.Phase contrast lattice images of the non-integer planes shown in Figure 1 were obtained with axial illumination of the sample by defocusing the objective lens of a Philips EM-300 electron microscope.