Scattering-type Scanning Near-field Optical Microscopy (s-SNOM) is a scanning probe approach to optical micros-copy and spectroscopy bypassing the ubiquitous diffraction limit of light to achieve a spatial resolution of about 10 nanometers. s-SNOM employs the strong confinement of light at the apex of a sharp metallic AFM tip to create a nanoscale optical hot-spot. This defines the high resolution that can be achieved independent from the used wave-length from visible, IR, even up to the THz spectral region. Interferometric detection of the scattered light from the hotspot gives access to local optical properties like absorption and reflection, allowing FTIR spectroscopy with IR broadband lasers on the 10 nm length scale for nano- chemical identification and compositional mapping of various organic and inorganic materials. The optical near-field hotspot can also be employed to excite and detect plasmon polaritons which enables the quantification of local free charge-carrier properties in doped semiconductors.

Furthermore, focusing visible light to the tip enables either Tip-Enhanced Raman Spectroscopy (TERS) collecting the inelastically scattered light or nano-PL collecting fluorescence light from the nanoscale hotspot. The conceptu-al design of the microscope allows several methods in one instrument, investigating the same sample location with different principles. Exploiting the fact that this microscope combines optical microscopy and AFM, further meas-urement modes like photothermal expansion (AFM-IR), Kelvin Probe Force Microscopy (KPFM), conductive AFM and many more can be realized subsequently on the same sample location.