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

Paper NS1-MoM6
Chemical Vapor Deposition onto Size-Selected, Aerosolized Silicon Nanoparticles

Monday, October 31, 2005, 10:00 am, Room 204

Session: Nanometer Scale Structures
Presenter: J.T. Roberts, University of Minnesota
Authors: J.T. Roberts, University of Minnesota
J. Holm, University of Minnesota
Y.-C. Liao, University of Minnesota
A. Nienow, University of Minnesota
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We describe a method for depositing metal oxide layers onto the surfaces of aerosolized nanoparticles. Chemical vapor deposition was used to deposit group IV metal oxides, including zirconium dioxide, onto silicon. The film precursors were anhydrous metal nitrates. Layers were deposited on silicon particles of initial diameter between 10 and 20 nm. The results are important because they describe a new approach for manipulating interfacial properties of nanoparticles that have materials applications. More fundamentally, the results are among the first kinetic and mechanistic studies of surface reactivity in aerosolized nanoparticles. Deposition was investigated using tandem differential mobility analysis (T-DMA) and transmission electron microscopy (TEM). Aerosolized, crystalline silicon nanoparticles were extracted from a plasma synthesis chamber into an atmospheric pressure flow tube reactor. The particle streams were sent through a furnace for thermal activation, through a bipolar diffusion charger to establish a known charge distribution on the particles, and then through a differential mobility analyzer (DMA-1). DMA-1 was used to create a stream of monodisperse particles; selected diameters were in the 10-20 nm range The monodisperse particle streams were swept into a reaction zone, which was a heated copper tube with a valve for the precursor introduction. The reaction zone was designed for maximal flexibility, with variable temperature (25-200 ºC), particle residence time (1-10 s), and gas-phase composition. Particles that exited the reaction zone were analyzed in two ways: (1) for size changes, with a second DMA capable of measuring diameter changes as small as 1%, and (2) for morphological changes that are induced by deposition, using TEM.