Femtosecond Carrier Dynamics in Metal/Quasi-2D MoS2 Nanostructures
Master of Science
Plasmonic nanoparticles and quasi-2D (Q2D) transition metal dichalcogenides (TMDs) have been identified as promising materials for solar-to-fuel energy conversion. Plasmonically active materials are interesting because large absorption cross-sections and non-radiative decay of plasmons that can excite hot electrons for injection into semiconducting materials. Q2D MoS$_2$ is known to be highly catalytically active for driving the hydrogen evolution reaction (HER). Combined together plasmonically active particles and MoS$_2$ can act as a hybrid antenna/catalyst nanostructures with both high absorption and catalytic activity. We performed femtosecond transient absorption spectroscopy measurements of Au/MoS$_2$ hybrid nanostructures finding ultrafast signatures of hot electron generation in the form of "anomalous" sub-100 fs lifetime signals indicative of electron-electron scattering. Coherent generation of acoustic phonon modes was also observed allowing for estimation of the peak electron temperature during excitation. Near field scanning probe microscopy measurements showed the presence of hot spots that may be responsible for hot electron generation observed in Au/MoS$_2$ hybrid nanostructures.