Bulletin of the American Physical Society
2005 72nd Annual Meeting of the Southeastern Section of the APS
Thursday–Saturday, November 10–12, 2005; Gainesville, FL
Session FA: Nanoscience Invited Session |
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Chair: Andrew Rinzler, Ho Bun Chan, University of Florida Room: Hilton Century A |
Friday, November 11, 2005 8:30AM - 9:06AM |
FA.00001: Time-Resolved Measurements of Carbon Nanotube and Nanohorn Growth Invited Speaker: Mechanisms for carbon nanotube growth have been investigated for both laser vaporization (LV) and chemical vapor deposition (CVD) synthesis techniques through the use of time-resolved, in situ laser-based diagnostics for the measurement of absolute growth rates. Optimization of both the production of loose single-wall carbon nanotubes (SWNTs) by LV and the sustained growth of mm-long, vertically-aligned carbon nanotube arrays (VANTAs) by CVD are described. For SWNT growth by laser co-vaporization of carbon and trace metal catalysts at high (1200\r{ }C) temperatures, nanotubes are found to grow at $\sim $ 1--5 microns/second to lengths of only several microns, as determined by gated-ICCD imaging and laser spectroscopy of the plume of ejected material. Efforts to scale the LV production of SWNTs utilizing an industrial Nd:YAG laser (600 W average power, 1-500 Hz repetition rate, 0.5-10ms pulse width) are described. In addition to vaporizing material at much higher rates, the high-power laser irradiation provides sufficient plasma plume density and temperature to enable the growth of novel single-wall carbon nanohorn (SWNH) structures without the need for metal catalysts in the target. Applications of these SWNH structures as metal catalyst supports will be discussed. Through the application of time-resolved reflectivity and direct imaging, CVD growth of VANTAs from hydrocarbon gases at sustained rates of 0.2 -- 0.5 microns/second have been directly measured over millimeters of length at lower ($\sim $ 700\r{ }C) temperatures. Now, through a new laser-CVD setup at the ALPS (Advanced Laser Processing and Synthesis) facility at ORNL, high-power laser heating is being employed for the fast and position-controlled growth of carbon nanotubes on substrates. In situ fast optical pyrometry is employed to record the rapid thermal processing of metal-catalyst-prepared substrates to investigate the nucleation and early growth behavior of CVD-grown nanotubes. New nanotube growth and tunable Raman spectroscopy facilities at the Center for Nanophase Materials Sciences at ORNL will be outlined. In collaboration with Alex Puretzky, Zuqin Liu, David Styers-Barnett, Christopher M. Rouleau, Hongtao Cui, Ilia Ivanov, Bin Zhao, and Hui Hu, Oak Ridge National Laboratory and the Center for Nanophase Material Sciences. [Preview Abstract] |
Friday, November 11, 2005 9:06AM - 9:42AM |
FA.00002: Quantum Effects in Molecule-Based Nanomagnets Invited Speaker: Research into molecule-based-magnets has made immense strides in recent years, with the discoveries of all organic molecular magnets, room temperature 3D ordered permanent magnets, and single-molecule magnets (SMMs), the latter exhibiting a host of spectacular quantum phenomena; for a review, see ref. [1]. SMMs represent a molecular approach to nanoscale and sub-nanoscale magnetic particles. They offer all of the advantages of molecular chemistry as well as displaying the superparamagnetic properties of mesoscale magnetic particles of much larger dimensions. They also straddle the interface between classical and quantum behavior; for example, they exhibit quantum tunneling of their magnetization. I will give a general introduction to this area of research, followed by an overview of recent results obtained using high-frequency (40-800~GHz) electron paramagnetic resonance techniques developed at the University of Florida. These results include: an elucidation of the role of molecular symmetry in the magnetic quantum tunneling phenomenon [2]; and the observation of quantum entanglement between pairs of nanomagnets within a supramolecular dimer [3]. \\ 1. D. Gatteschi and R. Sessoli, Angew. Chem. \textbf{42}, 268 (2003). \\ 2. E. del Barco et al., J. Low Temp. Phys. \textbf{140}, 119-174 (2005). \\ 3. S. Hill et al., \textit{Science} \textbf{302}, 1015 (2003). [Preview Abstract] |
Friday, November 11, 2005 9:42AM - 10:18AM |
FA.00003: Surface plasmon mediated imaging at the nanoscale using metal lenses Invited Speaker: It has been proposed that a thin metal film can act as a near-field lens with sub-diffraction limit resolution. Near-field focusing with such metal lenses relies on the excitation of localized surface plasmons on a metal-dielectric interface in close proximity to a nanoscale light source. These plasmonic-lenses could have applications in near-field lithography and optical data storage. This presenation will focus on near-field scanning optical microscopy (NSOM) experiments that directly demonstrate frequency-dependent near-field focusing with planar metal films. In these studies the lens structure consists of a free-standing bilayer of 50nm Au and 50nm Si$_{3}$N$_{4}$, while the nanoscale object is formed by the tip of a near-field scanning optical microscope. The corresponding image behind the metal lens is detected via a Pt nanoparticle that acts as a near-field scatterer. We will show that low frequency operation ($\lambda \quad > \quad \sim $600nm) of these lenses results in the excitation of extended surface plasmon waves, whereas operation at the localized plasmon frequency ($\lambda \quad \sim $ 550nm) results in a narrowed field distribution in the image plane, as predicted by theory. [Preview Abstract] |
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