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What is Tip-Enhanced Raman Spectroscopy (TERS)?

Tip-Enhanced Raman Spectroscopy (TERS) enables the acquisition of chemical information with a lateral resolution far below the diffraction limit. The TERS measurement technique is a combination of surface-enhanced Raman scattering (SERS) with scanning probe microscopy (SPM) techniques such as Atomic Force Microscopy (AFM). Thus it combines the high spatial resolution of AFM with the chemical sensitivity of Raman scattering.

To obtain the TERS effect a metal coated AFM-tip can be used as a nanostructure. The excitation laser light is focused onto the tip-apex to enhance the Raman signal in close proximity to the tip. The lateral resolution is thereby dependent on the tip-apex size (10 – 20 nm). The TERS effect is assumed to be based on surface plasmons and chemical resonance effects resulting in enhanced electrical fields and increased Raman signal intensities. The TERS tip illumination is usually applied from either above, below or from the side.

Although TERS is drawing more and more attention, its practical fields of application are limited to a few samples and scientific questions. Also the availability of commercial TERS-tips is still not established. Furthermore the cost of the metal-coated tips increases the total expense for the experiments to a significant degree.

TERS application examples can be found in the following publications:

G. Rusciano et al., Nanoscale Chemical Imaging of Bacillus subtilis Spores by Combining Tip-Enhanced Raman Scattering and Advanced Statistical Tools. ACS nano 8, 12300-12309 (2014).

A. Weber-Bargioni et al., Hyperspectral Nanoscale Imaging on Dielectric Substrates with Coaxial Optical Antenna Scan Probes. Nano letters 11, 1201-1207 (2011).