AVS 49th International Symposium
    Nanometer Structures Tuesday Sessions
       Session NS+EL-TuA

Paper NS+EL-TuA8
Surface Passivation Effects of Deposited Ge-Nanocrystal Films Probed with Synchrotron Radiation

Tuesday, November 5, 2002, 4:20 pm, Room C-207

Session: Quantum Dots
Presenter: T. van Buuren, Lawrence Livermore National Laboratory
Authors: C. Bostedt, Lawrence Livermore National Laboratory
T. van Buuren, Lawrence Livermore National Laboratory
T.M. Willey, Lawrence Livermore National Laboratory
T. Moller, Hasylab at DESY, Germany
L.J. Terminello, Lawrence Livermore National Laboratory
Correspondent: Click to Email
Clusters and nanocrystals represent a new class of materials that exhibit promising novel properties. The production of these nanostructures in the gas phase gives control over not only the size of the nanoparticles, but also over surface passivation - often not possible in other growth modes. The clusters are condensed out of supersaturated Germanium-vapor which is cooled down in a He-atmosphere and are subsequently deposited on a variety of substrates. Their surfaces can be subsequently passivated with different materials evaporated into the vacuum chamber. This approach allows us to probe in a controlled and dynamic fashion the effect of surface passivation on nanocluster properties. X-ray absorption spectroscopy (XAS) and photoemission (PES) were performed on thin films of Germanium (Ge) clusters. Clean Ge nanocrystal films are found to exhibit much stronger quantum confinement effects at the band edges than similar Si particle films. These findings are compared to recent electronic structure calculations. For passivated nanocluster films we find that the passivating agent strongly alters the electronic structure of the clusters. In general the absorption edge shifts to significantly higher energies compared to cluster films without surface passivation. These results will be discussed in terms of a reduction of the cluster-cluster interactions. @FootnoteText@ C. Bostedt acknowledges a fellowship from the German Academic Exchange Service DAAD in the HSP-III program. The work is supported by the US-DOE, BES Material Sciences under contract W-7405-ENG-48, LLNL.