Fig. 1

Graphene plasmons in graphene nanoribbons (a) and graphene with structural defects (b–d). a AFM-IR imaging with two different laser excitation configurations (left) and corresponding AFM-IR images of graphene nanoribbons at each configuration showing the orientation dependent near-field intensity. Schematics of the AFM-IR imaging (left), near-field images (middle) and line profile of the near-field images (right) when the E-field of the excitation was parallel (top) and perpendicular (bottom). The ribbon edge and fringe locations are denoted by the dashed line and red arrows on the line profiles. Laser excitation frequency was 1184 cm^− 1. Reproduced with permission from [30]. Copyright 2017 American Chemical Society. b Near-field images of ordered or quasi-expansion (top) and highly disordered or Anderson localized (bottom) graphene at 901 cm^− 1 excitation comparing the plasmonic confinement between the two graphene edges. The blue dashed lines represent the fringe pattern. Scale bar is 300 nm. Reproduced under the terms of the Creative Commons License from [34]. Copyright 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. c AFM topography (top left) and nano-IR image (bottom left) of graphene nanobubbles at 910 cm^− 1 excitation showing plasmonic confinement at the bubbled regions. The boundaries of the nanobubbles are shown in blue dashed line in the nano-IR image. Scale bar is 200 nm. Right panel shows the theoretical calculation of plasmon wavelength and dispersion diagram of the graphene nanobubble structure. The bubble area is represented by the gap shown the inset schematics. Reproduced with permission from [35]. Copyright 2016 American Chemical Society. d Interaction of plasmon wave with a graphene wrinkle with three different widths (W). Reprinted with permission from [36]. Copyright 2017 American Chemical Society