Figure 1: Identification of the Au stacking fault tetrahedra.

(a) Scanning tunnelling microscopy topography of two defect-like features with the shape of a truncated triangle (V=+100 mV, I=1 nA), which are interpreted as (truncated) SFTs. At the Au(111) surface, these features exist at the crossroads of three pairs of herringbone ridges exclusively. Image size: 29 × 36 nm². (b,c) Cross-sectional <110> high-resolution transmission electron microscopy micrographs of the Au(111) film revealing the presence of stacking fault tetrahedra (SFTs), which are highlighted by black solid and white dashed lines, respectively. The top left inset in c shows the fast Fourier transform pattern in which the reciprocal lattice vector g= is indicated by a white circle. The inverse fast Fourier transform of g= is presented in the upper right inset. It shows the shift of the {111} planes owing to the presence of the stacking faults in c. The local strain map (g=) of the indicated SFT is presented in the lower right inset, which shows the dislocations as hot spots and corresponding strain gradients due to the SFT. The scale bars in b,c correspond to a length of 5 nm. The colour scale bar in the lower right inset in c represents the relative strain variations. The scale bar for strain mapping is between −12% (black colour) to 12% (white colour).