title: Graphene/h-BN plasmon-phonon coupling and plasmon delocalization observed by infrared nano-spectroscopy.
abstract: We observed the coupling of graphene Dirac plasmons with different surfaces using scattering-type scanning near-field optical microscopy integrated into a mid-infrared synchrotron-based beamline. A systematic investigation of a graphene/hexagonal boron nitride (h-BN) heterostructure is carried out and compared with the well-known graphene/SiO2 heterostructure. Broadband infrared scanning near-field optical microscopy imaging is able to distinguish between the graphene/h-BN and the graphene/SiO2 heterostructure as well as differentiate between graphene stacks with different numbers of layers. Based on synchrotron infrared nanospectroscopy experiments, we observe a coupling of surface plasmons of graphene and phonon polaritons of h-BN (SPPP). An enhancement of the optical band at 817 cm(-1) is observed at graphene/h-BN heterostructures as a result of hybridization between graphene plasmons and longitudinal optical phonons of h-BN. Furthermore, longitudinal optical h-BN modes are preserved on suspended graphene regions (bubbles) where the graphene sheet is tens of nanometers away from the surface while the amplitude of transverse optical h-BN modes decrease.
authors.affiliation: Departamento de Física, Universidade Federal de Minas Gerais, 30123-970 - Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Ingrid D
authors.initials: ID
authors.lastname: Barcelos
authors.forename: Alisson R
authors.initials: AR
authors.lastname: Cadore
authors.forename: Leonardo C
authors.initials: LC
authors.lastname: Campos
authors.forename: Angelo
authors.initials: A
authors.lastname: Malachias
authors.forename: K
authors.initials: K
authors.lastname: Watanabe
authors.forename: T
authors.initials: T
authors.lastname: Taniguchi
authors.forename: Francisco C B
authors.initials: FC
authors.lastname: Maia
authors.forename: Raul
authors.initials: R
authors.lastname: Freitas
authors.forename: Christoph
authors.initials: C
authors.lastname: Deneke