2 research outputs found
Asymmetric Effect of Oxygen Adsorption on Electron and Hole Mobilities in Bilayer Graphene: Long- and Short-Range Scattering Mechanisms
We probe electron and hole mobilities in bilayer graphene under exposure to molecular oxygen. We find that the adsorbed oxygen reduces electron mobilities and increases hole mobilities in a reversible and activated process. Our experimental results indicate that hole mobilities increase due to the screening of long-range scatterers by oxygen molecules trapped between the graphene and the substrate. First principle calculations show that oxygen molecules induce resonant states close to the charge neutrality point. Electron coupling with such resonant states reduces the electron mobilities, causing a strong asymmetry between electron and hole transport. Our work demonstrates the importance of short-range scattering due to adsorbed species in the electronic transport in bilayer graphene on SiO<sub>2</sub> substrates
Infrared Fingerprints of Natural 2D Talc and PlasmonâPhonon Coupling in GrapheneâTalc Heterostructures
Two-dimensional (2D) materials occupy
a noteworthy place in nanophotonics
providing for subwavelength light confinement and optical phenomena
dissimilar to those of their bulk counterparts. In the mid-infrared,
graphene-based heterostructures and van der Waals crystals of hexagonal
boron nitride (hBN) overwhelmingly concentrate the attention by exhibiting
real-space nano-optics features from plasmons, phononâpolaritons,
and hybrid plasmon phononâpolaritons. Here we present a prime
study on mid-infrared nanophotonics of talc, a natural atomically
flat layered material, and graphene-talc (G-talc) heterostructures
using broadband synchrotron infrared nanospectroscopy. Wavelength
tuning of the talc vibrational resonances, assigned to in- and out-of-plane
molecular vibrations, are achieved by changing the thickness of the
crystals, which configures a tunable infrared signature for the 2D
talc. In G-talc nanostructures, we unveil a coupling of the graphene
plasmons polaritons with surface phonons polaritons of talc, originating
hybrid surface plasmonâphonon polaritons modes. In analogy
to G-hBN and G-SiO<sub>2</sub> heterostructures, the coupling in G-talc
produces a large increase in the opto-vibrational activity for the
out-of-plane mode as well as it induces a blue-shift for the in-plane
mode. Moreover, the coupling can be modulated by an external gate
voltage to the heterostructure when mounted in a transistor configuration.
Therefore, our results introduce talc and G-talc heterostructures
as appealing materials for nanophotonics, especially for applications
involving long wavelengths and active electric tuning of opto-vibrational
activity