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Colloquia

ics Colloquium
Friday, December 8, 2000
4:00 PM
Physics Building, Room 204
Note special time.
Prof. A T. Johnson, Jr. [Host: Joseph Poon]
Univ. of Pennsylvania
"Quantum Confinement of Electrons and Phonons in Single Wall Carbon Nanotubes"
ABSTRACT:
Single wall carbon nanotubes are a fascinating set of nanomaterials whose unique physical properties reflect the effect of quantum confinement on the electronic and phonon energy spectrum. Electron waves confined to the cylindrical tube wall obey periodic boundary conditions. Their energy spectrum consists of a set of one-dimentional subbands, making nanotubes metals or semiconductors depending on the precise wrapping of the constituent graphene sheet. I will discuss functional nanotube devices we have made, including field effect transistors, diodes, and highly conducting electrical interconnects. Nanotube sound waves (phonons) also experience quantum size effects. This makes nanotubes incredibly stiff, and may enable mechanical composites or nano-mechanical systems. We recently measured the effect of the quantized phonon spectrum on the specific heat of nanotubes as well as their thermal conductivity. Our results support theoretical predictions that nanotubes have an extremely high thermal conductivity, perhaps the highest of any known material.

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