Atomic Structure of Si(111)-(5×2)-Au from High Resolution Electron Microscopy and Heavy-Atom Holography

The main elements of the atomic structure of the Si(111)- $\left(5\times 2\right)$-Au surface have been found by combining off-zone high resolution electron microscopy with ${\chi }^2$ electron diffraction minimization and direct phasing of the diffraction data using heavy-atom holography. The structure is different from recent models based upon interpreting scanning tunneling microscope and x-ray data in terms of disordered arrangements of gold atoms, and much simpler. It contains two lines of gold atoms decorating a surface dislocation plus an expanded surface arrangement of silicon atoms. This model appears to explain all the available experimental data and is consistent with an expansive surface stress for Si(111).