Nanoscale carrier distribution and trap dynamics in supported and suspended WSe2 layers studied by scanning nonlinear dielectric microscopy

The unique electronic and optical properties of atomically thin transition metal dichalcogenides make them promising candidates for advanced device applications. However, their electrical characteristics are strongly influenced by the interfacial and dielectric environments provided by the substrate. To elucidate these substrate-related properties, microscopy techniques with high spatial resolution are essential. Among these techniques, scanning nonlinear dielectric microscopy (SNDM) has emerged as a powerful tool for visualizing dominant carrier distributions in semiconductor materials. In this study, we employ SNDM to investigate two types of mechanically exfoliated WSe2 samples: one supported on a SiO2 substrate and the other suspended over nanoscale Au wires. Our findings reveal spatial and bias-dependent differences in carrier behavior between the two structures. Specifically, the suspended WSe2 exhibits reduced hysteresis and a more symmetric ambipolar response, consistent with the suppression of charge trapping at interface states. To further probe the fast dynamic responses associated with interface states, we also conduct local deep level transient spectroscopy measurements using time-resolved SNDM.