Time-resolved THz-TDS nanoscopy for probing carrier dynamics with femtosecond temporal and nanometer spatial resolution

By combining THz-TDS based scattering near-field optical microscopy (s-SNOM) with ultrafast pump-probe spectroscopy we enable probing of dynamic material properties with femtosecond temporal and 20nm spatial resolution. We demonstrate s-SNOM based ultra-fast pump-probe THz-TDS imaging and spectroscopy as well as time-resolved THz near-field transient measurements of extreme sub-wavelength scale sample structures. As a representative material system, we study the spatial heterogeneity of photoexcited carriers in a silicon based semiconductor device and a micron-sized MoS
2
crystal. For the latter, near-field THz transients reveal layer dependent carrier decay dynamics and lifetimes in the picosecond range.