Assessing tiny building blocks.
First discovered in 1991, carbon nanotubes have become one of the most important building blocks of nanotechnology. Combining the strength of diamonds with the conductivity of graphite, carbon nanotubes can be envisioned as a sheet of graphite (a lattice of carbon atoms arranged in a hexagonal pattern) rolled into an incredibly thin cylinder one 30-thousandth the diameter of a human hair.
Although nanotubes have already been incorporated into new products, among them reinforced plastics, plastics that conduct electricity, high-resolution flat panel displays, novel semiconductor transistors, and sharper tips for atomic force microscopes, some characteristics of this new material remain poorly understood. Anna Swan, an ENG research assistant professor of electrical and computer engineering, is developing new methods to measure the optical and electronic properties of individual nanotubes. The ability to accurately characterize nanotubes will help scientists and engineers develop nano-photonic devices that use nanotubes to their full potential.
Swan proposes to study how light changes the electronic properties of nanotubes as the environment is systematically changed around them. Among the factors that will be varied are the refractive index, which measures the speed at which light moves through a material, the electrical charge of the medium in which the tubes are located, and the effects of stresses such as heat and strain.
Swan’s instrument will measure both the vibrational signature, using an optical technique known as Raman spectroscopy, and the fluorescence spectra emitted by the tubes. A sample patterned by electron beam lithography makes it possible to first locate tubes using atomic force microscopy, then later to reliably find the same tube using the optically visible pattern. A new microscope-compatible chamber will provide the means to control the environment.
Swan will be working closely with other members of the Center for Nanoscience and Nanobiotechnology as well as with collaborators at Harvard and MIT. The work is being supported by a recent SPRInG grant from the Office of the Provost.
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