The maximum lateral spatial resolution that can be obtained in confocal Raman spectroscopy is ultimately limited by the diffraction of light which is dependent on the wavelength of the laser employed, typically in the order of 0.5 µm. To break this diffraction limit, a new approach has been adapted to bring nanometer resolution to Raman spectroscopy. Tip-enhanced Raman scattering (TERS) is a technique that combines the spatial resolution of atomic force microscopy (AFM) with the chemical information of Raman spectroscopy (see, for example our recent review article: Gibson K.F., Kazarian S.G. Tip-enhanced Raman Spectroscopy (TERS) Encyclopedia of Analytical Chemistry, eds R.A. Meyers, John Wiley & Sons, Ltd (2014) (doi). This technique is based on the surface enhanced Raman scattering (SERS) effect where the electric field is greatly enhanced near the surfaces of a cluster of nano metal particles. However, instead of the cluster of metal nano particles, the precisely controlled AFM tip coated with gold or silver is used as the nano metal particle to generate a very localised (< diameter of the AFM tip)  enhancement of Raman signal.  We have demonstrated the enhanced spatial resolution with this technique by measuring dispersed single wall carbon nanotubes (see image below). Raman image measured without the AFM tip has shown a "blurred" chemical image (base on the Raman band at 1595 cm-1) of the carbon nanotube featuring the diameter of the nanotube of >300 nm wide. When the Raman scan is accompanied with a gold coated AFM tip, fine feature of the carbon nanotube is revealed.

  Carbon nanotube with and without AFM tip

To find out more about this research, explore a couple of research articles by clicking on a link below. 

Tip-enhanced Raman mapping with top-illumination AFM (This article has also recently been featured on nanotechweb.org)

Finding a Needle in a Haystack (This article has also been featured on nanotechweb.org)

 

  • Chan K. L. A., Kazarian S. G. Tip-enhanced Raman mapping with top-illumination AFM, Nanotechnology 22 (2011) 175701
  • Chan K. L. A., Kazarian, S. G.  Finding a needle in a chemical haystack: tip-enhanced Raman scattering for studying carbon nanotubes mixtures, Nanotechnology 21 (2010) 445704.

Collaboration in the field of nanoplasmonics and tip-enhanced Raman scattering:  

  •  Kharintsev S.S., Fishman A.I., Saikin S. K., Kazarian S. G. Near-field Raman dichroism of azo-polymers exposed to nanoscale dc electrical and optical poling  Nanoscale (2016) 8, 19867 - 19875 (doi)
  • Kharintsev S. S., Fishman A. I., Kazarian S. G., M. K. Salakhov “Polarization of near-field light induced with a plasmonic nanoantenna”  Physical Review B (2015) 92, 115113 (doi)

  • Kharintsev, S., Fishman, A., Kazarian, S.G., Gabitov, I., Salakhov, M. Experimental evidence for axial anisotropy beyond the diffraction limit induced with a bias voltage plasmonic nanoantenna and longitudinal optical near-fields in photoreactive polymer thin films                  ACS Photonics (2014) 1(10) 1025-1032 (doi)
  • Kharintsev S. S., Rogov A. M., Kazarian S. G.Nanopatterning and tuning of optical taper antenna apex for tip-enhanced Raman scattering performance,  Rev. Sci. Instrum. (2013) 84, 093106  (doi)
  • Kharintsev S.S., Fishman A.I., Saikin S. K., Kazarian S. G. Near-field Raman dichroism of azo-polymers exposed to nanoscale dc electrical and optical poling,   Nanoscale (2016) in press (doi)