3 research outputs found
Graphene Plasmon Reflection by Corrugations
Graphene
plasmons (GPs) exhibit extreme confinement of the associated
electromagnetic fields. For that reason, they are promising candidates
for controlling light in nanoscale devices. However, despite the ubiquitous
presence of surface corrugations in graphene, very little is known
on how they affect the propagation of GPs. Here we perform a comprehensive
theoretical analysis of GP scattering by both smooth and sharp corrugations.
For smooth corrugations, we demonstrate that scattering of GPs depends
on the dielectric environment, being strongly suppressed when graphene
is placed between two dielectrics with the same refractive indices.
We also show that sharp corrugations can act as effective GP reflectors,
even when their dimensions are small in comparison with the GP wavelength.
Additionally, we provide simple analytical expressions for the reflectance
of GPs valid in an ample parametric range. Finally, we connect these
results with potential experiments based on scattering scanning near-field
optical microscopy (s-SNOM) showing how to extract the GP reflectance
from s-SNOM images
Waveguide and Plasmonic Absorption-Induced Transparency
Absorption-induced
transparency (AIT) is one of the family of induced
transparencies that has emerged in recent decades in the fields of
plasmonics and metamaterials. It is a seemingly paradoxical phenomenon
in which transmission through nanoholes in gold and silver is dramatically
enhanced at wavelengths where a physisorbed dye layer absorbs strongly.
The origin of AIT remains controversial, with both experimental and
theoretical work pointing to either surface (plasmonic) or in-hole
(waveguide) mechanisms. Here, we resolve this controversy by carefully
filling nanoholes in a silver film with dielectric material before
depositing dye on the surface. Our experiments and modeling show that
not only do plasmonic and waveguide contributions to AIT both exist,
but they are spectrally identical, operating in concert when the dye
is both in the holes and on the surface
Stacking Structures of Few-Layer Graphene Revealed by Phase-Sensitive Infrared Nanoscopy
The stacking orders in few-layer graphene (FLG) strongly influences the electronic properties of the material. To explore the stacking-specific properties of FLG in detail, one needs powerful microscopy techniques that visualize stacking domains with sufficient spatial resolution. We demonstrate that infrared (IR) scattering scanning near-field optical microscopy (sSNOM) directly maps out the stacking domains of FLG with a nanometric resolution, based on the stacking-specific IR conductivities of FLG. The intensity and phase contrasts of sSNOM are compared with the sSNOM contrast model, which is based on the dipolar tip–sample coupling and the theoretical conductivity spectra of FLG, allowing a clear assignment of each FLG domain as Bernal, rhombohedral, or intermediate stacks for tri-, tetra-, and pentalayer graphene. The method offers 10–100 times better spatial resolution than the far-field Raman and infrared spectroscopic methods, yet it allows far more experimental flexibility than the scanning tunneling microscopy and electron microscopy