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Colloquium: Dr. Keji Lai
Start Date: 11/8/2019Start Time: 4:00 PM
End Date: 11/8/2019End Time: 5:00 PM
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Event Description:
Join us before the event for Hot drinks and snacks
TITLE: Spatiotemporal Imaging of Carrier Dynamics in Monolayer Semiconductors

ABSTRACT: The optoelectronic properties of atomically thin transition-metal dichalcogenides are strongly correlated with the presence of structural imperfections in the materials, which are not necessarily detrimental for certain applications. Using the laser-illuminated microwave impedance microscopy, we were able to perform simultaneous spatial and temporal photoconductivity imaging in two types of WS2 monolayers with different defect densities. For chemical-vapor deposited (CVD) samples, the diffusion length and carrier lifetime, extracted from the spatial profile and temporal relaxation of microwave signals, respectively, are in good agreement with the diffusion equation and Einstein relation. Time-resolved experiments indicate that the critical process for photo-excited carriers is the escape of holes from trap states. As a result, the photoconductivity is weaker in exfoliated monolayers with lower disorders than the more defective CVD samples. Our work reveals the intrinsic time and length scales of electrical response to photo-excitation in van der Waals materials.
Location Information:
Main Campus - (PHYS) Physics Building  (View Map)
Physics Building
825 W. Dickson St.
Fayetteville, AR 72701
United States
Phone: 479-575-2506
Room: PHYS 133 - Sharrah Lecture Hall
Contact Information:
Name: Laci
Phone: 479-575-2506
Email: lmshuffi@uark.edu
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