A Mossbauer study of the superconducting NdFeAsO(0.82)F(0.18) oxypnictide compound

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, Moire patterns in a (root 3 x root 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 pi 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]. (c) 2008 Elsevier B.V. All rights reserved.