Journal
NANO LETTERS
Volume 15, Issue 10, Pages 6889-6895Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.5b02805
Keywords
2D materials; ultrafast; MoS2; structural dynamics; electron diffraction
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Funding
- Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division
- DOE BES Scientific User Facilities Division
- SLAC UED/UEM program development fund
- German National Academy of Sciences Leopoldina [LPDS 2013-13]
- NSF [DGE-114747]
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Two-dimensional materials are subject to intrinsic and dynamic rippling that modulates their optoelectronic and electromechanical properties. Here, we directly visualize the dynamics of these processes within monolayer transition metal dichalcogenide MoS2 using femtosecond electron scattering techniques as a real-time probe with atomic-scale resolution. We show that optical excitation induces large-amplitude in-plane displacements and ultrafast wrinkling of the monolayer on nanometer length-scales, developing on picosecond time-scales. These deformations are associated with several percent peak strains that are fully reversible over tens of millions of cycles. Direct measurements of electron-phonon coupling times and the subsequent interfacial thermal heat flow between the monolayer and substrate are also obtained. These measurements, coupled with first-principles modeling, provide a new understanding of the dynamic structural processes that underlie the functionality of two-dimensional materials and open up new opportunities for ultrafast strain engineering using all-optical methods.
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