title: Monitoring morphological changes in 2D monolayer semiconductors using atom-thick plasmonic nanocavities.
abstract: Nanometer-sized gaps between plasmonically coupled adjacent metal nanoparticles enclose extremely localized optical fields, which are strongly enhanced. This enables the dynamic investigation of nanoscopic amounts of material in the gap using optical interrogation. Here we use impinging light to directly tune the optical resonances inside the plasmonic nanocavity formed between single gold nanoparticles and a gold surface, filled with only yoctograms of semiconductor. The gold faces are separated by either monolayers of molybdenum disulfide (MoS2) or two-unit-cell thick cadmium selenide (CdSe) nanoplatelets. This extreme confinement produces modes with 100-fold compressed wavelength, which are exquisitely sensitive to morphology. Infrared scattering spectroscopy reveals how such nanoparticle-on-mirror modes directly trace atomic-scale changes in real time. Instabilities observed in the facets are crucial for applications such as heat-assisted magnetic recording that demand long-lifetime nanoscale plasmonic structures, but the spectral sensitivity also allows directly tracking photochemical reactions in these 2-dimensional solids.
authors.affiliation: NanoPhotonics Centre, Cavendish Laboratory, University of Cambridge , Cambridge, CB3 0HE, United Kingdom.
authors.forename: Daniel O
authors.initials: DO
authors.lastname: Sigle
authors.forename: Jan
authors.initials: J
authors.lastname: Mertens
authors.forename: Lars O
authors.initials: LO
authors.lastname: Herrmann
authors.forename: Richard W
authors.initials: RW
authors.lastname: Bowman
authors.forename: Sandrine
authors.initials: S
authors.lastname: Ithurria
authors.forename: Benoit
authors.initials: B
authors.lastname: Dubertret
authors.forename: Yumeng
authors.initials: Y
authors.lastname: Shi
authors.forename: Hui Ying
authors.initials: HY
authors.lastname: Yang
authors.forename: Christos
authors.initials: C
authors.lastname: Tserkezis
authors.forename: Javier
authors.initials: J
authors.lastname: Aizpurua
authors.forename: Jeremy J
authors.initials: JJ
authors.lastname: Baumberg
keywords: 2D-materials; molybdenum disulfide; nano-optics; nanoparticles; tunable plasmons; waveguides