What does TERS do?

Tip-enhanced Raman (TERS) is a novel scanning probe microscopy (SPM) technique that combines chemical/structural characterisation capability of Raman spectroscopy with the spatial resolution of an atomic force microscopy (AFM). It is one of the few techniques that provide chemical and structural information at ambient condition at high spatial resolution. TERS can reach a spatial resolution of less than 30 nm. A wide range of materials/chemicals including organic nanostructures, thin films, inorganic nanostructures and biological materials can be investigated.

How does TERS work?

In Tip Enhanced Raman Spectroscopy, a metallic tip is used to enhance the electric field intensity of the excitation beam. This Raman signal is enhanced by (E/E₀)⁴, where E is the enhanced electric field and E₀ is excitation electric field. Since the electric field is enhanced at the tip end, Raman signal is predominantly generated at the tip end, which can be utilised to from a Raman map. For good enhancement, the tip is placed at a close proximity to the surface (usually with few nanometres).

What is TERS used for?

• In principle, TERS can be used to investigate any Raman-active materials such as carbon nanotubes, organic electronic polymers, phase separated polymers and biological materials;
• TERS is useful particularly for measurements that requires ambient conditions.

See our SPM measurement services page to find out how TERS may help with your specific application.

What are the measurement challenges?

Four main challenges were identified: (a) measurement of enhancement factor of the TERS tip; (b) reproducibility of the tip; (c) reference samples; and (d) in-depth understanding of TERS process, modelling and instrumentation. NPL has been working on these challenges to make the technique more reliable and usable.

See our TERS research page to find out more.