Surface alloying effects in the growth of Au on Pb(1 1 1) thin film

The growth of Au on thin Pb films was studied by scanning tunneling microscopy and low energy electron diffraction. We found that the initial Au deposition resulted in a rough Au-Pb alloy interface on the thin Pb films. With further deposited Au, Moiré patterns in a (3×3)-Au layer was formed on top of a laterally contracted Au-Pb alloy surface. Finally, the Au deposition performed the Stranski-Krastanov type growth mode to form three-dimensional Au crystals. This structure information provided a possible explanation to the observed phase shift π between the density of states near the Fermi energy and the superconducting transition temperature as a function of film thickness as reported recently [Guo et al., Science 306 (2004) 1915 and Zhang et al., Phys. Rev. Lett. 95 (2005) 096802].