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)- 5×2-Au surface have been found by combining off-zone high resolution electron microscopy with 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).