Thickness-Dependent Auger Scattering in a Single WS₂ Microcrystal Probed with Time-Resolved Terahertz Near-Field Microscopy

Time-resolved terahertz (THz) spectroscopy has been shown as a powerful technique to non-invasively determine the charge carrier properties in photo-excited semiconductors. However, the long wavelengths of terahertz radiation reduces the applicability of this technique to large samples. Using THz near-field microscopy, we show THz measurements of the lifetime of 2D-single exfoliated microcrystals of transition metal dichalcogenides (WS₂). The increased spatial resolution of THz near-field microscopy allows spatial mapping of the evolution of the carrier lifetime, revealing Auger assisted surface defect recombination as the dominant recombination channel. THz near-field microscopy allows for the non-invasive and high resolution investigation of material properties of 2D semiconductors relevant for nanoelectronic and optoelectronic applications.