3 research outputs found
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Tuning and Persistent Switching of Graphene Plasmons on a Ferroelectric Substrate
We characterized plasmon propagation
in graphene on thin films of the high-κ dielectric PbZr<sub>0.3</sub>Ti<sub>0.7</sub>O<sub>3</sub> (PZT). Significant modulation
(up to ±75%) of the plasmon wavelength was achieved with application
of ultrasmall voltages (< ±1 V) across PZT. Analysis of the
observed plasmonic fringes at the graphene edge indicates that carriers
in graphene on PZT behave as noninteracting Dirac Fermions approximated
by a semiclassical Drude response, which may be attributed to strong
dielectric screening at the graphene/PZT interface. Additionally,
significant plasmon scattering occurs at the grain boundaries of PZT
from topographic and/or polarization induced graphene conductivity
variation in the interior of graphene, reducing the overall plasmon
propagation length. Lastly, through application of 2 V across PZT,
we demonstrate the capability to persistently modify the plasmonic
response of graphene through transient voltage application
Efficiency of Launching Highly Confined Polaritons by Infrared Light Incident on a Hyperbolic Material
We
investigated phonon–polaritons in hexagonal boron nitridea
naturally hyperbolic van der Waals materialî—¸by means of the
scattering-type scanning near-field optical microscopy. Real-space
nanoimages we have obtained detail how the polaritons are launched
when the light incident on a thin hexagonal boron nitride slab is
scattered by various intrinsic and extrinsic inhomogeneities, including
sample edges, metallic nanodisks deposited on its top surface, random
defects, and surface impurities. The scanned tip of the near-field
microscope is itself a polariton launcher whose efficiency proves
to be superior to all the other types of polariton launchers we studied.
Our work may inform future development of polaritonic nanodevices
as well as fundamental studies of collective modes in van der Waals
materials
Graphene-Based Platform for Infrared Near-Field Nanospectroscopy of Water and Biological Materials in an Aqueous Environment
Scattering scanning near-field optical microscopy (s-SNOM) has emerged as a powerful nanoscale spectroscopic tool capable of characterizing individual biomacromolecules and molecular materials. However, applications of scattering-based near-field techniques in the infrared (IR) to native biosystems still await a solution of how to implement the required aqueous environment. In this work, we demonstrate an IR-compatible liquid cell architecture that enables near-field imaging and nanospectroscopy by taking advantage of the unique properties of graphene. Large-area graphene acts as an impermeable monolayer barrier that allows for nano-IR inspection of underlying molecular materials in liquid. Here, we use s-SNOM to investigate the tobacco mosaic virus (TMV) in water underneath graphene. We resolve individual virus particles and register the amide I and II bands of TMV at <i>ca</i>. 1520 and 1660 cm<sup>–1</sup>, respectively, using nanoscale Fourier transform infrared spectroscopy (nano-FTIR). We verify the presence of water in the graphene liquid cell by identifying a spectral feature associated with water absorption at 1610 cm<sup>–1</sup>