AVS 56th International Symposium & Exhibition
    Nanometer-scale Science and Technology Monday Sessions
       Session NS+BI-MoM

Paper NS+BI-MoM9
Fabrication and Characterization of Carbon Nanostructures; Optical, Mechanical and Chemical Properties

Monday, November 9, 2009, 11:00 am, Room L

Session: Nanowires and Nanoparticles I
Presenter: H. Fredriksson, Chalmers University of Technology, Sweden
Authors: H. Fredriksson, Chalmers University of Technology, Sweden
T. Pakizeh, Chalmers University of Technology, Sweden
J. Cardenas, University of Oslo, Norway
M. Käll, Chalmers University of Technology, Sweden
B.H. Kasemo, Chalmers University of Technology, Sweden
D. Chakarov, Chalmers University of Technology, Sweden
Correspondent: Click to Email
Nanosized carbon particles are present in many different context and applications. Examples include, aerosols and interstellar dust, inks, lubricants, composite materials and electronics. Investigations of the physical properties of such nanocarbons are therefore well motivated. We present a systematic investigation of the optical, mechanical and chemical properties of graphite and amorphous carbon nanostructures with different size. Hole-mask colloidal lithography and oxygen reactive ion etching is used to fabricate supported carbon nanostructures with well-defined diameters ranging from ~100 to 350 nm and heights from ~50 to 200 nm. Optical absorption/extinction spectra of these samples, as well as finite difference time domain (FDTD) calculations, reveal resonant absorption of visible light, both for the graphitic and for the amorphous carbon structures. The spectral maxima of the absorption peaks are correlated to the nanostructure diameters and heights. These optically resonant nanostructures are then further investigated using Raman spectroscopy, and compared with measurements from macroscopic graphite crystals. We show that the limited size has little influence on the mechanical properties of the graphite, i.e. the nanostructures have the mechanical properties of crystalline graphite. However, a slight enhancement of the Raman scattering intensity, correlated to the resonant absorption in the nanostructures is observed. Upon increasing the laser power we also observe distinct peak-splits and -shifts as well as increasing anti-Stokes signal intensity, suggesting selective heating of the nanostructures. Furthermore, the correlation between size and optical absorption have been used to follow the oxidation-driven size decrease of amorphous carbon nanostructures, relevant as model systems for investigations of soot oxidation. It is shown that the peak characteristics (spectral position and amplitude) are very sensitive signatures of the nanostructure size and that this can be used to accurately measure very low oxidation rates, using simple optical absorption techniques.