Research: Charge dynamics
The understanding of charge dynamics under external stimuli is critical for both fundamental science and practical applications. Using pulsed-laser and fast electronics, we are able to perform spatiotemporal imaging on photo-sensitive materials with sub-100nm spatial resolution and sub-10ns temporal resolution. The extracted carrier lifetime allows us to evaluate the steady-state density and mobility of the sample. The work reveals the intrinsic time and length scales of electrical response to photo-excitation.
Chu et al. PNAS 117, 13908 (2020)
(Left) Schematic of the time-resolved MIM (tr-iMIM) setup, in which the sample is illuminated by a diode laser with its intensity modulated by an EOM. The EOM is driven by a function generator, which also triggers the high-speed oscilloscope that averages the iMIM signals. (Right) Relaxation of tr-iMIM signals at the center (green) and edge (magenta) of the WS2 flake shown on the left. Solid lines are bi-exponential fits to the data with two relaxation time constants.
This research is funded by the NSF MRSEC under Award DMR-1720595.