THz microscopy on a single WS2 microcrystal

Terahertz time-domain spectroscopy enables the contact-free determination of charge carrier properties in metals and semiconductors. However, the applicability of THz spectroscopy is severely reduced by the low spatial resolution imposed by the diffraction limit. We have developed a time-resolved THz near-field microscope to circumvent this limitation, allowing the determination of the carrier dynamics with a resolution of a few microns. We use this microscope to measure a single exfoliated flake of WS
2
with domains of different thickness. The THz spectra reveal phonon modes in the sheet conductance. We also observe a biexponential carrier recombination associated to surface-assisted Auger scattering.