Raman Spectroscopy of Carbon Nanotubes under Axial Strain

Resonant Raman spectroscopy of individual carbon§nanotube bundles under axial strains up to 17% are§presented. This strain causes nanotube debundling§which gives insight into the nature of the broad§metallic G- band. For metallic nanotubes, the G- band§upshifts and narrows with strain, making it appear§more semiconductor-like. This metal to semiconductor§transition is irreversible with strain, indicating§that nanotube-nanotube coupling plays a significant§role in the observed G- band of metallic nanotubes.§The vibrational and§electronic properties of these nanotubes under strain§are modeled using tight-binding§calculations.§A systematic study of surface enhanced Raman§spectroscopy (SERS) of carbon nanotubes. Raman§spectra of individual carbon nanotubes are measured§before and after depositing silver nanoparticles.§Regions exhibiting SERS enhancement were located§relative to a grid, allowing subsequent scanning§electron microscopy to be performed. SERS enhancement§factors up to 134,000, a consistent upshift in the G§band Raman frequency and nanoparticle heating in§excess of 600°C are revealed.