Strain engineering is an attractive approach for tuning
the local
optoelectronic properties of transition metal dichalcogenides (TMDs).
While strain has been shown to affect the nanosecond carrier recombination
dynamics of TMDs, its influence on the sub-picosecond electronic relaxation
dynamics is still unexplored. Here, we employ a combination of time-resolved
photoemission electron microscopy (TR-PEEM) and nonadiabatic ab initio molecular dynamics (NAMD) to investigate the ultrafast
dynamics of wrinkled multilayer (ML) MoS2 comprising 17
layers. Following 2.41 eV photoexcitation, electronic relaxation at
the Γ valley occurs with a time constant of 97 ± 2 fs for
wrinkled ML-MoS2 and 120 ± 2 fs for flat ML-MoS2. NAMD shows that wrinkling permits larger amplitude motions
of MoS2 layers, relaxes electron–phonon coupling
selection rules, perturbs chemical bonding, and increases the electronic
density of states. As a result, the nonadiabatic coupling grows and
electronic relaxation becomes faster compared to flat ML-MoS2. Our study suggests that the sub-picosecond electronic relaxation
dynamics of TMDs is amenable to strain engineering and that applications
which require long-lived hot carriers, such as hot-electron-driven
light harvesting and photocatalysis, should employ wrinkle-free TMDs.