The Gold/high Temperature Superconductor Interface; Metallicity of the Near Surface Region and a Search for the Proximity Effect

We have used high resolution photoemission spectroscopy to probe the electronic structure of a wide variety of gold/high temperature superconductor interfaces, the majority of which were formed by low-temperature (20 K) gold evaporations on cleaved high quality single crystals. For c-axis interfaces formed on the 123 family of superconductors, we fine that the gold deposition essentially destroys the metallicity of the superconducting substrate in the near surface region (approximately 5 angstrom), while the near surface region of Bi2Sr2CaCu2O8 remains metallic. We have also used photoemission spectroscopy to search for a proximity-effect induced superconducting gap in gold overlayers on c-axis single crystals and a-axis thin films, though no such effect was found.