AVS 53rd International Symposium
    Nanometer-scale Science and Technology Thursday Sessions
       Session NS-ThA

Paper NS-ThA2
Properties of Carbon-Based Nanostructures Grown by Low-Pressure Plasma Enhanced Chemical Vapor Deposition

Thursday, November 16, 2006, 2:20 pm, Room 2016

Session: Nanoscale Material Processing
Presenter: J.B.O. Caughman, Oak Ridge National Laboratory
Authors: J.B.O. Caughman, Oak Ridge National Laboratory
L.R. Baylor, Oak Ridge National Laboratory
R.A. Kisner, Oak Ridge National Laboratory
K. Korsah, Oak Ridge National Laboratory
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The role of the plasma in the growth of carbon-based nanostructures is being determined by relating plasma conditions to the physical and electrical properties of carbon nanofibers and nanosheets. Nanofibers have a cylindrical cone-like structure while nanosheets have a planar sheet-like structure. Forests of vertically aligned nanofibers and nanosheets have been grown using an inductively coupled plasma source operated from 30 to 100 mTorr. The plasma is composed of hydrogen and either acetylene or methane as the carbon source. The plasma conditions are determined by using mass spectroscopy and optical emission spectroscopy. Dilute mixtures of carbon containing gases in hydrogen lead to well-formed nanostructures, while excessive carbon in the plasma leads to an increase in amorphous carbon deposition. The presence of a nickel catalyst layer prior to deposition leads to nanofiber growth, while no catalyst leads to nanosheet growth. Substrate bias plays an important role in the formation of nanofibers (by controlling the physical etching component during deposition), while having a detrimental effect on nanosheet growth. Field emission from the material, as measured with a scanning probe, is found to be strongly dependent on the details of the nanostructure. Sparse forests or well defined nanosheet edges give the lowest threshold fields. Details of the effect of plasma properties and substrate conditions (bias and temperature) on the electrical/physical properties of the nanofibers will be presented.* @FootnoteText@ *Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the U.S. Dept. of Energy under contract DE-AC05-00OR22725.