TERS Spectroscopy

It is possible to perform TERS measurements with the hardware and software system developed by Horiba, in which both the LabRam HR Evolution spectrometer and the OmegaScope SPM platform have been specifically designed to be coupled. The software allows the red excitation laser (633 nm, maximum power 17 mW) to be diverted from the Raman apparatus, used for conventional measurements, to the SPM platform for TERS measurements (via a predefined optical path that is pre-aligned during installation).
The beam is then focused on the atoms at the very end of the silver-coated TERS tip (30 nm curvature radius) through a 100× objective, achieving resonance between the tip oscillation and the laser frequency.
The tip approaches the surface and, operating in tapping mode, a conventional SPM image is recorded. Raman spectra are then collected in the same area with the tip in contact mode. Signal enhancement occurs when the Raman intensity increases as the tip contacts the surface; otherwise, the signal is still acquired but without amplification (co-localized Raman).
The TERS system is also equipped with an electron-multiplying CCD (EMCCD) detector, fitted with three different gratings (300, 600, and 1800 lines/mm).
The unique system design allows extremely rapid switching between conventional SPM and Raman spectroscopy modes and TERS operation, without the need for modifications to the experimental setup. This greatly facilitates the use of an advanced technique that would otherwise be particularly demanding and time-consuming in terms of instrument operation.