Scanning tunneling microscopy observations on the reconstructed Au(111) surface: Atomic structure, long-range superstructure, rotational domains, and surface defects

Abstract

High-resolution scanning tunneling microscopy data on the reconstructed Au(111) surface are presented that give a comprehensive picture of the atomic structure, the long-range ordering, and the interaction between reconstruction and surface defects in the reconstructed surface. On the basis of the atomically resolved structure, the stacking-fault-domain model involving periodic transitions from fcc to hcp stacking of top-layer atoms is confirmed. The practically uniform contraction in the surface layer along [11\ifmmode\bar\else\textasciimacron\fi{}0] indicates that the previously proposed soliton functionalisms are not correct descriptions for the fcc\ensuremath{\rightarrow}hcp stacking transition. The lateral displacement of \ensuremath{\sim}0.9 \AA{} in the ${(}_{\mathrm{\ensuremath{-}}1}^{22}$ $_{2}^{0}$) unit cell along [112\ifmmode\bar\else\textasciimacron\fi{}] is in good agreement with the transition between fcc and hcp stacking. The vertical displacement in the transition regions (0.20\ifmmode\pm\else\textpm\fi{}0.05 \AA{}) is largely independent of the tunneling parameters, while the atomic corrugation (0.2 \AA{} typically, up to 1 \AA{}) depends strongly on tunneling parameters and tip conditions.The two different stacking regions within the unit cell are directly identified from the domain pattern at step edges; fcc stacking is deduced for the wider areas and thus is energetically more favorable. A new long-range superstructure is reported. It is created by a correlated periodic bending of the parallel corrugation lines by \ifmmode\pm\else\textpm\fi{}120\ifmmode^\circ\else\textdegree\fi{} every 250 \AA{}, i.e., rotational domains are arranged in a zigzag pattern. Interactions on this scale indicate long-range elastic lattice strain. This structure reflects the overall tendency to isotropic contraction, combining the locally favorable uniaxial contraction and an effective isotropic contraction on a larger scale. Boundaries of rotational domains can also be formed by a termination of the reconstruction lines. Individual corrugation lines, separating different stacking regions, cannot disappear. The termination occurs in well-ordered, U-shaped connections of neighbored lines or by a complicated pattern of entangled corrugation lines. Steps and bulk defects do not inhibit the reconstruction, but can affect the local reconstruction pattern. In most cases steps are crossed by the reconstruction lines, and the strict correlation of the reconstruction pattern on the terraces, both in phase and orientation, reflects interaction over the step edge. Sometimes the reconstruction pattern at the steps resembles those found at rotational domain boundaries.