title: Nanoscale mapping of plasmon and exciton in ZnO tetrapods coupled with Au nanoparticles.
abstract: Metallic nanoparticles can be used to enhance optical absorption or emission in semiconductors, thanks to a strong interaction of collective excitations of free charges (plasmons) with electromagnetic fields. Herein we present direct imaging at the nanoscale of plasmon-exciton coupling in Au/ZnO nanostructures by combining scanning transmission electron energy loss and cathodoluminescence spectroscopy and mapping. The Au nanoparticles (~30 nm in diameter) are grown in-situ on ZnO nanotetrapods by means of a photochemical process without the need of binding agents or capping molecules, resulting in clean interfaces. Interestingly, the Au plasmon resonance is localized at the Au/vacuum interface, rather than presenting an isotropic distribution around the nanoparticle. On the contrary, a localization of the ZnO signal has been observed inside the Au nanoparticle, as also confirmed by numerical simulations.
authors.affiliation: CNR-IMEM, Parco Area delle Scienze 37/A, IT 43124 Parma, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Bertoni
authors.affiliation: CNR-IMEM, Parco Area delle Scienze 37/A, IT 43124 Parma, Italy.
authors.forename: Filippo
authors.initials: F
authors.lastname: Fabbri
authors.affiliation: CNR-IMEM, Parco Area delle Scienze 37/A, IT 43124 Parma, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Villani
authors.affiliation: CNR-IMEM, Parco Area delle Scienze 37/A, IT 43124 Parma, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Lazzarini
authors.affiliation: EMAT, University of Antwerp, Groenenborgerlaan 171, BE 2020 Antwerp, Belgium.
authors.forename: Stuart
authors.initials: S
authors.lastname: Turner
authors.affiliation: EMAT, University of Antwerp, Groenenborgerlaan 171, BE 2020 Antwerp, Belgium.
authors.forename: Gustaaf
authors.initials: G
authors.lastname: Van Tendeloo
authors.affiliation: CNR-IMEM, Parco Area delle Scienze 37/A, IT 43124 Parma, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Calestani
authors.affiliation: Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts (USA).
authors.forename: Silvija
authors.initials: S
authors.lastname: Gradečak
authors.affiliation: CNR-IMEM, Parco Area delle Scienze 37/A, IT 43124 Parma, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Zappettini
authors.affiliation: CNR-IMEM, Parco Area delle Scienze 37/A, IT 43124 Parma, Italy.
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Salviati