AVS 50th International Symposium
    Nanometer Structures Thursday Sessions
       Session NS-ThM

Paper NS-ThM7
Electronic Properties of Individual Defects in Carbon Nanotubes by Scanning Probe Microscopy

Thursday, November 6, 2003, 10:20 am, Room 308

Session: Advances in Scanning Probes
Presenter: V. Meunier, Oak Ridge National Laboratory
Authors: V. Meunier, Oak Ridge National Laboratory
S.V. Kalinin, Oak Ridge National Laboratory
R.J. Harrison, Oak Ridge National Laboratory
A.P. Baddorf, Oak Ridge National Laboratory
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Electronic devices based on carbon nanotubes and semiconductor nanowires require development and understanding of quantitative tools for transport measurements at nanoscale dimensions. Scanning Gate Microscopy (SGM) and Scanning Impedance Microscopy (SIM) are both capable of detecting atomic-scale defects in carbon nanotubes. In SGM individual defects are visualized as a decrease in the current through the dc circuit, since defects are depleted for tip voltages that are related to the local electronic structure of the defect. In SIM the local ac potential amplitude and phase are recorded; the defects are manifest as potential drops (back gate regime) or potential minima (tip gate regime). Here, a method for quantitative characterization of the electronic structure of individual defects from SGM and SIM results is presented. The interaction between a carbon nanotube and a point charge is studied using both atomistic first principles calculations and continuum electrostatic methods. The results are compared and extrapolated to real tip geometries in order to simulate the interaction of the scanning tip with an adjacent nanotube. Comparison with experimental data suggests that the gate voltage dependence of the image contrast is a direct measure of the difference in Fermi energies at these defects. The potential of the present approach for the identification of individual defects is discussed.