Raman microscope for tip-enhanced Raman scattering (TERS)

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In order to perform optical spectroscopy on the nanometer scale, we request a setup for tip-enhanced Raman scattering (TERS). By combination of a scanning-probe microscope with a Raman spectrometer, TERS allows to record optical spectra with a spatial resolution of 10-100 nm. We plan to use this method for investigating the physical properties of low-dimensional materials such as two-dimensional (2D) semiconductors, graphene, and carbon nanotubes. Our aim is to obtain local spectroscopic information about the physical properties and their potential modifications by defects, chemical functionalization, crystallographic orientation and stacking order in few-layer 2D materials. In particular, stacking of atomically thin 2D materials like graphene or transition-metal dichalcogenides can result in a moiré superlattice due to mismatch of lattice constants or twist angle between the layers. This moiré structure modulates the optical and electronic properties with a length scale of approximately 10-20 nm. TERS is ideally suited to investigate the optical and structural properties of moiré-induced effects as well as other local modifications of 2D materials and carbon nanotubes. This advanced method thus offers new insights into the physical properties of low-dimensional materials beyond conventional optical spectroscopy.