Carbon based nanostructures, including carbon nanotubes, graphenes, and graphene nano-ribbons, have played a central role in nanoscale science and technology in the past decade. Even though many promising devices (electronic, optoelectronic, and sensing) 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. My group recently made two important progresses, each addressing central problems in this field.

First, a powerful characterization method that allows spectral Rayleigh imaging of individual carbon nanotubes (CNTs) has been developed for the first time. Here, 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, most importantly, the energies of van Hove singularities. Using this technique, a scattering spectrum was taken for every pixel of the image with ~1 nm spectral resolution, which can then be used to determine the chirality indices of all the CNTs simultaneously. Our advanced Rayleigh imaging is much faster (by orders of magnitude) and more versatile than other optical (Raman or PL) or scanned probe techniques (STM, AFM) that are currently used for nanotube characterization.

Second, we developed a new method to synthesize a large quantity of graphene nano ribbons (GNRs) with a predetermined width (width variation < 0.5 nm) and edge direction (zigzag). This is achieved by the use of carefully developed chemical procedure. Our UV-VIS-IR (ensemble measurement) and AFM topography & scanned gate microscopy (individual measurements) reveal a number of exciting new properties for our GNRs, including a uniform and reproducible width, a clear & narrow absorption peak (~ 0.4 eV, FWHM < 40 meV) and electrical conductivity.