Physics
Optical Properties of Carbon Nanotubes
Since the accidental discovery of a new form of carbon in 1991, carbon nanotubes have attracted wide-spread interest due to their remarkable properties. It is the strongest, stiffest and toughest material known as well as the best possible conductor of heat and electricity. A nanotube can be thought of as a rolled up sheet of graphite, with typical diameters around 1-2 nanometers for single wall carbon nanotubes, and a length-to-diameter aspect ratio of up to 108. The nanotubes can be either metallic or semiconducting, depending on the chirality and diameter of the nanotube, characterized by the roll-up vectors (n,m). The variable and direct bandgap for the semiconducting tubes makes for potentially powerful photonics applications.
In our lab we specialize in optical measurements of individual carbon nanotubes so that we are able to measure properties that are not possible to extract in ensemble measurements. For example, a combination of applied strain and strain measurements using resonant micro Raman showed that previous strain measurements of CNTs in composites overestimated the strain applied to the nanotubes by a factor of 4, indicating problems with adhesion between the composite and the nanotubes.
Due to the strong optical resonances typical for a one dimensional material, we are also able to use resonant Raman to map the optical resonance energies and correlate the energies to the specific tube diameter and chirality and gain understanding of the strong environmental influence on the excitonic binding energies.
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