We investigate the optoelectronic response of a graphene single-bilayer interface junction using photocurrent (PC) microscopy. We measure the polarity and amplitude of the PC while varying the Fermi level by tuning a gate voltage. These measurements show that the generation of PC is by a photothermoelectric effect. The PC displays a factor of ∼10 increase at the cryogenic temperature as compared to room temperature.

We observed highly efficient generation of electron-hole pairs due to impact excitation in single-walled carbon nanotube p-n junction photodiodes. Optical excitation into the second electronic subband E22 leads to striking photocurrent steps in the device I-VSD characteristics that occur at voltage intervals of the band-gap energy EGAP/e. Spatially and spectrally resolved photocurrent combined with temperature-dependent studies suggest that these steps result from efficient generation of multiple electron-hole pairs from a single hot E22 carrier.

We report on a method to produce free-standing graphene sheets from epitaxial graphene on silicon carbide (SiC) substrate. Doubly clamped nanomechanical resonators with lengths up to 20 μm were patterned using this technique and their resonant motion was actuated and detected optically. Resonance frequencies of the order of tens of megahertz were measured for most devices, indicating that the resonators are much stiffer than expected for beams under no tension.

We describe the first terahertz electrical measurements of single-walled carbon nanotube transistors. A picosecond ballistic electron resonance is directly observed in the time-domain. These results demonstrate a powerful new tool for directly probing picosecond electron motion in nanostructures. © 2009 Optical Society of America.

The temperature distributions in current-carrying carbon nanotubes have been measured with a scanning thermal microscope. The obtained temperature profiles reveal diffusive and dissipative electron transport in multiwalled nanotubes and in single-walled nanotubes when the voltage bias was higher than the 0.1-0.2 eV optical phonon energy. Over 90% of the Joule heat in a multiwalled nanotube was found to be conducted along the nanotube to the two metal contacts.

We combine suspended carbon nanotube transistors with optical trapping techniques and scanning photocurrent microscopy to investigate the motion of suspended single-walled carbon nanotubes in solution. We study the movement of nanotubes by monitoring their photocurrent images and measure their thermal fluctuations by imaging microbeads that are tightly attached to nanotubes by single-stranded DNA. By analyzing their thermal fluctuations, we are able to obtain the torsional and bending stiffness of nanotubes and then calculate their diameters.

An overview is presented of an approach for treating cancer that uses nanoparticles to deliver heat to diseased areas after absorbing energy from a laser of the appropriate wavelength. The implications are discussed of the relationship of parameters necessary to raise the temperature to therapeutically beneficial levels. Tight focusing is required for a continuous-wave laser to sufficiently heat individual nanoparticles because of heat loss to the surrounding fluid during the period of exposure.

We report the electrical characteristics of substrate-supported metallic single walled carbon nanotubes at temperatures up to 573 K over a range of bias voltages (Vb) for zero gate voltage in air under atmospheric pressure. Our results show a monotonic increase in resistance with temperature, with an I- Vb characteristic that is linear at high temperature but nonlinear at low temperature.

We have directly grown single-walled carbon nanotubes on epitaxial BaTi O3 thin films, fabricating prototype carbon nanotube-ferroelectric devices. We demonstrate polarization switching using the nanotube as a local electric field source and compare the results to switching with an atomic force microscopy tip. The observed variation of domain growth rates in the two cases agrees with the changes in electric field intensity at the ferroelectric surface. © 2008 American Institute of Physics.

We demonstrate that a monolayer graphene membrane is impermeable to standard gases including helium. By applying a pressure difference across the membrane, we measure both the elastic constants and the mass of a single layer of graphene. This pressurized graphene membrane is the world's thinnest balloon and provides a unique separation barrier between 2 distinct regions that is only one atom thick. © 2008 American Chemical Society.