31 research outputs found
Revealing the planar chemistry of two-dimensional heterostructures at the atomic level
Two-dimensional (2D) atomic crystals and their heterostructures are an intense area of study owing to their unique properties that result from structural planar confinement. Intrinsically, the performance of a planar vertical device is linked to the quality of its 2D components and their interfaces, therefore requiring characterization tools that can reveal both its planar chemistry and morphology. Here, we propose a characterization methodology combining (micro-) Raman spectroscopy, atomic force microscopy and time-of-flight secondary ion mass spectrometry to provide structural information, morphology and planar chemical composition at virtually the atomic level, aimed specifically at studying 2D vertical heterostructures. As an example system, a graphene-on-h-BN heterostructure is analysed to reveal, with an unprecedented level of detail, the subtle chemistry and interactions within its layer structure that can be assigned to specific fabrication steps. Such detailed chemical information is of crucial importance for the complete integration of 2D heterostructures into functional devicesopen2
Graphene Photonics and Optoelectronics
The richness of optical and electronic properties of graphene attracts
enormous interest. Graphene has high mobility and optical transparency, in
addition to flexibility, robustness and environmental stability. So far, the
main focus has been on fundamental physics and electronic devices. However, we
believe its true potential to be in photonics and optoelectronics, where the
combination of its unique optical and electronic properties can be fully
exploited, even in the absence of a bandgap, and the linear dispersion of the
Dirac electrons enables ultra-wide-band tunability. The rise of graphene in
photonics and optoelectronics is shown by several recent results, ranging from
solar cells and light emitting devices, to touch screens, photodetectors and
ultrafast lasers. Here we review the state of the art in this emerging field.Comment: Review Nature Photonics, in pres
Dysphagia after antireflux fundoplication: endoscopic, radiological and manometric evaluation
Electrochemically Top Gated Graphene: Monitoring Dopants by Raman Scattering
We demonstrate electrochemical top gating of graphene by using a solid
polymer electrolyte. This allows to reach much higher electron and hole doping
than standard back gating. In-situ Raman measurements monitor the doping. The G
peak stiffens and sharpens for both electron and hole doping, while the 2D peak
shows a different response to holes and electrons. Its position increases for
hole doping, while it softens for high electron doping. The variation of G peak
position is a signature of the non-adiabatic Kohn anomaly at . On the
other hand, for visible excitation, the variation of the 2D peak position is
ruled by charge transfer. The intensity ratio of G and 2D peaks shows a strong
dependence on doping, making it a sensitive parameter to monitor charges.Comment: 7 pages, 8 figure