Variation of Contact Barrier Height in Metal-Semiconducting Carbon Nanotube Junctions using a Localized Gate
E. Gallo, B. Nabet, M. Freitag, A.T. Johnson
Drexel University, US
Keywords: nanotube, schottky
We have previously succeeded in modulating current in a carbon nanotube “FET” device due to the presence of a potential on an AFM tip. Symmetric I-V is observed with no tip, however, the tip has a strong facilitating effect on current flow when the junction in its vicinity is reverse biased, thus giving rise to asymmetric I-V characteristics and demonstrating that the junction is controlling device behavior.
Previous explanations of this behavior have mainly been qualitative and based on changing of the Fermi level due to the presence of the tip. Here, we present a formulation based on the electrostatic potential of the tip and its effect on the Schottky barrier height. We propose that the presence of the CT-AFM creates a position dependent voltage potential that adds to the existing potential within the junction and modifies the maximum height of this barrier. The reduction is of the order of tens of meV at its maximum, which in turn increases thermionic emission 3 to 4 times, consistent with experimental results. The model explains increased conduction in the nanotube without a change in the tube’s Fermi level.
NSTI Nanotech 2003 Conference Technical Program Abstract