AVS 52nd International Symposium
    Nanometer-Scale Science and Technology Monday Sessions
       Session NS1-MoM

Paper NS1-MoM1
Morphological Control of Nanoporous Gold by Surfactants

Monday, October 31, 2005, 8:20 am, Room 204

Session: Nanometer Scale Structures
Presenter: J. Biener, Lawrence Livermore National Laboratory
Authors: J. Biener, Lawrence Livermore National Laboratory
M.M. Biener, Harvard University
T. Nowitzki, Universitaet Bremen, Germany
A.V. Hamza, Lawrence Livermore National Laboratory
C.M. Friend, Harvard University
M. Baeumer, Universitaet Bremen, Germany
Correspondent: Click to Email
Nanoporous Au (np-Au) prepared by electrochemically-driven dealloying of Ag-Au alloys has attracted considerable interest due to potential sensor and actuator applications. The material exhibits an open sponge-like morphology of interconnecting ligaments on the nanometer length scale. Due to the very high surface-to-volume ratio of np-Au, the surface chemistry should play an important role in controlling the pattern formation during dealloying. Ion-bombardment of Au surfaces can be used as a model system to study the mechanisms of pattern formation during dealloying: Both processes generate a supersaturation of Au adatoms and vacancies, which in turn results in the nucleation of Au adatom clusters and vacancy islands. The actual morphology evolving under these conditions strongly depends on the mobility of vacancies and adatoms, and in particular on the stabilization of undercoordinated Au atoms by adsorbate species. Here, we report on oxygen and argon ion sputter experiments on Au(111) surfaces which allow us to study the influence of oxygen adsorption on pattern formation. The resulting surface morphologies were characterized by scanning tunnelling microscopy (STM), and the amount of adsorbed oxygen was measured by X-ray photoemission spectroscopy (XPS). Specifically, our experiments demonstrate that adsorbed oxygen stabilizes a rougher surface morphology by stabilizing undercoordinated Au atoms. Our results thus open a new door to control the morphology of nanoporous metals by means of surfactants. This work was performed under the auspices of the U. S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.