Treading a Fine Line: One-Dimensional Semiconductor Physics in Carbon Nanotubes – Michael Fuhrer

Date: Mon. March 20th, 2006, 12:30 pm-1:30 pm
Location: Rockefeller 221

The growth of individual, long (> 1 mm), high-quality single- or few-walled carbon nanotubes (CNTs) on substrates by chemical vapor deposition has allowed the careful study of the intrinsic electronic properties of this material. Recently we have made electrical measurements on semiconducting CNTs up to 800 microns in length in a field-effect transistor (FET) geometry, and determined that the charge carrier mobility is greater than 100,000 cm2/Vs at room temperature, exceeding that of the best known semiconductors. Analysis of the FET behavior at higher drain bias indicates that semiconducting CNTs do not experience curren t saturation due to optical phonon emission (as observed in metallic CNTs) but rather show saturation of the carrier velocity at ~2 x 107 cm/s, approximately three times higher than the value for Si FETs. Studies of the anomalous (1/f) noise in semiconducting carbon nanotubes show that the noise power is inversely proportional to the number of carriers, following Hooge’s law with Hooge parameter comparable to conventional FETs, indicating that CNTs are not (as previously expected) unusually noisy due to their high surface-to-volume ratio. Interestingly, the temperature, pressure, and gate-voltage dependence of the noise indicates that (1) adsorbates probably do not play a large role in the noise, and (2) Hooge’s law (traditionally assumed to imply non-interacting charge carriers) is obeyed even in a one-dimensional conductor in the degenerate regime.