The polarized carbon nanotube thin film LED.

We demonstrate a light emitting p-i-n diode made of a highly aligned film of separated (99%) semiconducting carbon nanotubes, self-assembled from solution. By using a split gate technique, we create p- and n-doped regions in the nanotube film that are separated by a micron-wide gap. We inject p- and n-type charge carriers into the device channel from opposite contacts and investigate the radiative recombination using optical micro-spectroscopy.

Carbon nanotube photo- and electroluminescence in longitudinal electric fields.

The photoluminescence of a partially suspended, semiconducting carbon nanotube that forms the active channel of a field-effect transistor is quenched and red-shifted upon application of a longitudinal electrical (source-drain) field. The quenching can be explained by a loss of oscillator strength and an increased Auger-like nonradiative decay of the E(11) exciton. The spectral shifts are due to drain-field-induced doping that leads to enhanced dielectric screening.

Gate-variable light absorption and emission in a semiconducting carbon nanotube.

We investigate the gate field dependence of light absorption and emission of an individual, suspended semiconducting carbon nanotube using Raman and photoluminescence spectroscopies. We find a strong reduction in the absorption strength and a red shift of the E(33) state of the nanotube with increasing gate field. The photoluminescence from the E(11) state is quenched even stronger.

Phonon populations and electrical power dissipation in carbon nanotube transistors.

Carbon nanotubes and graphene are candidate materials for nanoscale electronic devices. Both materials show weak acoustic phonon scattering and long mean free paths for low-energy charge carriers. However, high-energy carriers couple strongly to optical phonons, which leads to current saturation and the generation of hot phonons.

Thin film nanotube transistors based on self-assembled, aligned, semiconducting carbon nanotube arrays.

Thin film transistors (TFTs) are now poised to revolutionize the display, sensor, and flexible electronics markets. However, there is a limited choice of channel materials compatible with low-temperature processing. This has inhibited the fabrication of high electrical performance TFTs.

Operation of graphene transistors at gigahertz frequencies.

Top-gated graphene transistors operating at high frequencies (gigahertz) have been fabricated and their characteristics analyzed. The measured intrinsic current gain shows an ideal 1/f frequency dependence, indicating a FET-like behavior for graphene transistors. The cutoff frequency f(T) is found to be proportional to the dc transconductance g(m) of the device, consistent with the relation f(T) = g(m)/(2piC(G)).

Covalently bridging gaps in single-walled carbon nanotubes with conducting molecules.

Molecular electronics is often limited by the poorly defined nature of the contact between the molecules and the metal surface. We describe a method to wire molecules into gaps in single-walled carbon nanotubes (SWNTs). Precise oxidative cutting of a SWNT produces carboxylic acid-terminated electrodes separated by gaps of View Article and Find Full Text PDF

Extracting subnanometer single shells from ultralong multiwalled carbon nanotubes.

We report a simple but powerful method for engineering multi-walled carbon nanotubes (MWNTs) by using manipulation by an atomic-force microscope. The successive shell-by-shell extraction process of ultralong MWNTs allows the exposure of the innermost single-walled carbon nanotubes (SWNTs), which have diameters as small as approximately 0.4 nm.

Electric field modulation of galvanomagnetic properties of mesoscopic graphite.

Electric field effect devices based on mesoscopic graphite are fabricated for galvanomagnetic measurements. Strong modulation of magnetoresistance and Hall resistance as a function of the gate voltage is observed as the sample thickness approaches the screening length. Electric field dependent Landau level formation is detected from Shubnikov-de Haas oscillations.

Modulation of thermoelectric power of individual carbon nanotubes.

Thermoelectric power (TEP) of individual single walled carbon nanotubes (SWNTs) has been measured at mesoscopic scales using a microfabricated heater and thermometers. Gate electric field dependent TEP modulation has been observed. The measured TEP of SWNTs is well correlated to the electrical conductance across the SWNT according to the Mott formula.