Scanning Acousto-Optoelectric Spectroscopy on a Transition Metal Dichalcogenide Monolayer.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 39449225.
- Also identified by DOI 10.1002/adma.202402799 and PMC identifier 11619229.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The charge carrier dynamics are investigated by surface acoustic waves (SAWs) inside a WSe<sub>2</sub> monolayer on LiNbO<sub>3</sub> by scanning acousto-optoelectric spectroscopy. A strong enhancement of the PL emission intensity is observed almost over the entire area of the flake. This enhancement increases with increasing amplitude of the wave and is especially strong at or in the vicinity to defects. The latter is attributed to the SAW-driven Poole-Frenkel activation of trapped charge carriers bound to trapping sites at these defects. In addition, the PL intensity exhibit clear periodic modulations at the SAW's frequency f<sub>SAW</sub> and at 2 f<sub>SAW</sub>. These modulations are clear and unambiguous fingerprints of spatio-temporal carrier dynamics driven by the SAW. These occur on sub-nanosecond timescales which are found in good agreement with calculated exciton dissociation times. Mapping and analyzing both effects, this study shows that scanning acousto-electric spectroscopy provides a highly sensitive and local contact-free probe which uncovers distinct local features not resolved by conventional quasi-static photoluminescence techniques. The method is ideally suited to study carrier transport in 2D and other types of nanoscale materials and to reveal dynamic exciton modulation, and carrier localization and activation dynamics in the technologically important megahertz to gigahertz frequency range.