Charge carrier profiling with MIR and THz s-SNOM

In the past years, it has been shown that s-SNOM (scattering-type scanning near-field optical microscopy) is a powerful technique to probe different light-matter interactions. Among them, charge carriers present different optical responses in the mid-infrared (MIR) and terahertz (THz) regions. Here we show that THz s-SNOM is highly sensitive to small changes in charge carrier concentration in a semiconductor, with spatial resolution at the nanometer scale.