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Enhanced Raman Scattering from Individual Semiconductor Nanocones and Nanowires

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PIs: L. Cao, B. Nabet & J. E. Spanier (Drexel University)

Control of nanostructure shape can play a significant role in the engineering of its properties. In particular much of the focus on the optical scattering response of nanostructures has been on semiconductor or metallic quantum dots or nanorods. As shown in this work dielectric nanostructures offer interesting opportunities in shape- and size-engineering of optical response due to the unique size- and shape-dependent electromagnetic eigenmodes of nanostructures.

These results required all of the following:

  • Vapor-liquid-solid growth of metal-catalyzed Si nanocones (SiNCs) and Si nanowires (SiNWs)
  • Spatially-resolved Raman scattering spectroscopy of individual SiNCs and SiNWs
  • Development of a mode of electromagnetic scattering from dielectric nanocones and nanowires based on incorporating contribution of enhanced electromagnetic field within the nanostructures

Conclusions:

SiNCs and SiNWs of exhibit a diameter-dependent and wavelength-dependent Raman scattering enhancement (RE), where RE is defined as the Raman scattering efficiency per unit volume normalized to that for bulk single-crystalline Si(100).

Laser excitation wavelength-dependence of scattering intensity does not scale as in Rayleigh scattering, but depends on wavelength-dependent dispersion in nanostructure.

Calculations based on electromagnetic scattering show good agreement with experiment, providing basis for size and shape-control of local enhancement of EM fields for fluorescence and Raman sensing applications.

References: Cao, Nabet and Spanier, submitted to Phys. Rev. Lett. (2005).

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