Condensed Matter Physics Seminar
2 p.m., Thursday, September 9, 2004
Room 1201, Physics Building
Conductance in One Dimension: Nanotubes and Molecules
Michael S. Fuhrer
(Department of Physics and Center for Superconductivity Research, University of
Abstract: Recent advances have allowed the exploration of true
one-dimensional electron transport in two new systems: carbon nanotubes and
conjugated organic molecules. In each case electrons are conducted through
the extended π-orbital network of carbon. I will discuss recent
experiments in my lab to determine the fundamental conduction properties of
semiconducting carbon nanotubes, and recent results from a collaborative effort
to synthesize, measure, and model transport through individual organometallic
molecules. Growth of very long (up to 1 millimeter), very clean
semiconducting carbon nanotubes has allowed determination of the charge carrier
mobility in this material. The mobility may exceed 105 cm2/Vs
at room temperature, higher than any other known semiconductor. Schottky-barrier
electrodes allow simultaneous injection of electrons and holes at high bias,
with recombination in the nanotube. A simple model allows determination of
the saturation velocity of carriers in the nanotube of 2 x 107
cm/s, twice that in silicon. We have studied the conduction through a
ferrocene-based organometallic molecule, and, in excellent agreement with
theoretical results, observe a Lorentzian resonance in the bias-dependent
conduction with a peak differential conductance of up to 70% of Go,
the theoretical maximum. The results are in sharp contrast to those of
our group and other groups on conjugated all-organic oligomers, where a high
conductance resonance is also expected, but not observed experimentally.
We suggest some solutions to this dilemma.
 T. Durkop, S. A. Getty, E.
Cobas, M. S. Fuhrer, “Extraordinary Mobility in Semiconducting Carbon Nanotubes”,
Nano Letters 4, 35-39 (2004).
 Yung-Fu Chen and M. S. Fuhrer, “Saturation Velocity in Semiconducting Carbon
 Stephanie A. Getty, Chaiwat Engtrakul, Lixin Wang, Rui Liu, San-Huang Ke,
Harold U. Baranger, Weitao Yang, Michael. S. Fuhrer, Lawrence R. Sita,
"Designing a high conductance molecular wire," submitted.
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