AVS 49th International Symposium
    Nanotubes: Science and Applications Topical Conference Tuesday Sessions
       Session NT-TuM

Paper NT-TuM2
Current Measurement with Tapping Mode AFM to Determine the Electrical Properties of Carbon Nanotubes

Tuesday, November 5, 2002, 8:40 am, Room C-209

Session: Nanotubes: Electronics and Field Emission
Presenter: M. Stadermann, University of North Carolina at Chapel Hill
Authors: M. Stadermann, University of North Carolina at Chapel Hill
J.J. Boland, University of North Carolina at Chapel Hill
M.R. Falvo, University of North Carolina at Chapel Hill
R. Superfine, University of North Carolina at Chapel Hill
S. Washburn, University of North Carolina at Chapel Hill
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Measurement of contact resistance and electronic transport properties of carbon nanotubes are typically performed with static contacts. Movable contacts provide many advantages over static contacts but difficulties arise from an inability to position the probe precisely on a nanotube, and to control the exact position of the electrical measurement due to thermal drift and piezoelectric hysteresis. The technique presented here allows characterization of the conductivity of different parts of a surface by applying a small voltage to a conductive AFM-tip and then scanning the surface in tapping mode. The resistance of the surface is determined from the current pulses flowing between tip and sample whenever the tip intermittently makes contact with the surface. The advantage of this technique is that electrical and topographical data are taken simultaneously and are therefore in registry. A further advantage is the high number and density of data points taken at constant contact force during a single scan. This method is applied to map out the contact resistance of carbon nanotubes on graphite and examine the coupling between charge transfer modes along and across the tube. It is found that the contact resistance of the nanotube varies with the contact angle.