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color="#000000"><b>Seminar on</b></font></div>
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<div align="center"><font face="Times New Roman"
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<div align="center"><font face="Arial" color="#000000"><b>Advanced
Rayleigh imaging for accurate carbon nanostructures</b></font></div>
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<div align="center"><font face="Times New Roman"
color="#000000"><b>Jiwoong Park</b>, Cornell University</font></div>
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<div align="center"><font face="Times New Roman"
color="#000000">Tuesday, October 20, 2009</font></div>
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<div align="center"><font face="Times New Roman" color="#000000">12:00
- 1:00 p.m.</font></div>
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<div align="center"><font face="Times New Roman"
color="#000000">Carbon based nanostructures, including carbon
nanotubes, graphenes, and graphene nanoribbons, have played a central
role in nanoscale science and technology in the past decade. Even
though many promising devices have been demonstrated using these
individual carbon nanostructures-most notably with carbon nanotubes,
applying them for larger scale devices has been difficult due to the
enormous challenges that are unique to nanostructures. As the most
notable example, there are no simple characterization methods for
identifying the chirality indices of individual carbon nanotubes with
a high throughput. My group recently developed a powerful
characterization method that allows spectrally resolved Rayleigh
imaging of a large array of individual carbon nanotubes (CNTs) on a
substrate. We successfully took a color scattering image of individual
CNTs using a combination of carefully controlled laser illumination
and refractive index matching. The unique color of each CNT reflects
its electronic structure including the energies of van Hove
singularities. Using this technique, we also studied electronic
interactions between closely located parallel CNTs, which revealed a
strong dipole coupling and enhancement/disappearance of Rayleigh
signal. Our advanced Rayleigh imaging is much faster and more
versatile than any other optical (Raman or PL) or scanned probe
techniques (STM, AFM) that are currently used for nanotube
characterization and will be a general tool for studying scattering
spectra of other nanoscale objects.</font></div>
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<div align="center"><font face="Times New Roman" color="#000000">Grier
Room, MIT Bldg 34-401</font></div>
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color="#000000">Refreshments served after the lecture</font></div>
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