17 research outputs found
Vertical Field Effect Transistor based on Graphene-WS2 Heterostructures for flexible and transparent electronics
The celebrated electronic properties of graphene have opened way for
materials just one-atom-thick to be used in the post-silicon electronic era. An
important milestone was the creation of heterostructures based on graphene and
other two-dimensional (2D) crystals, which can be assembled in 3D stacks with
atomic layer precision. These layered structures have already led to a range of
fascinating physical phenomena, and also have been used in demonstrating a
prototype field effect tunnelling transistor - a candidate for post-CMOS
technology. The range of possible materials which could be incorporated into
such stacks is very large. Indeed, there are many other materials where layers
are linked by weak van der Waals forces, which can be exfoliated and combined
together to create novel highly-tailored heterostructures. Here we describe a
new generation of field effect vertical tunnelling transistors where 2D
tungsten disulphide serves as an atomically thin barrier between two layers of
either mechanically exfoliated or CVD-grown graphene. Our devices have
unprecedented current modulation exceeding one million at room temperature and
can also operate on transparent and flexible substrates
Micrometer-scale ballistic transport in encapsulated graphene at room temperature
Devices made from graphene encapsulated in hexagonal boron-nitride exhibit
pronounced negative bend resistance and an anomalous Hall effect, which are a
direct consequence of room-temperature ballistic transport on a micrometer
scale for a wide range of carrier concentrations. The encapsulation makes
graphene practically insusceptible to the ambient atmosphere and,
simultaneously, allows the use of boron nitride as an ultrathin top gate
dielectric
Probing the Nature of Defects in Graphene by Raman Spectroscopy
Raman Spectroscopy is able to probe disorder in graphene through
defect-activated peaks. It is of great interest to link these features to the
nature of disorder. Here we present a detailed analysis of the Raman spectra of
graphene containing different type of defects. We found that the intensity
ratio of the D and D' peak is maximum (~ 13) for sp3-defects, it decreases for
vacancy-like defects (~ 7) and reaches a minimum for boundaries in graphite
(~3.5).Comment: 14 pages, 4 figure
Electron transfer kinetics on natural crystals of MoS2 and graphite
Here, we evaluate the electrochemical performance of sparsely studied natural crystals of molybdenite and graphite, which have increasingly been used for fabrication of next generation monolayer molybdenum disulphide and graphene energy storage devices. Heterogeneous electron transfer kinetics of several redox mediators, including Fe(CN)63−/4−, Ru(NH3)63+/2+ and IrCl62−/3− are determined using voltammetry in a micro-droplet cell. The kinetics on both materials are studied as a function of surface defectiveness, surface ageing, applied potential and illumination. We find that the basal planes of both natural MoS2 and graphite show significant electroactivity, but a large decrease in electron transfer kinetics is observed on atmosphere-aged surfaces in comparison to in situ freshly cleaved surfaces of both materials. This is attributed to surface oxidation and adsorption of airborne contaminants at the surface exposed to an ambient environment. In contrast to semimetallic graphite, the electrode kinetics on semiconducting MoS2 are strongly dependent on the surface illumination and applied potential. Furthermore, while visibly present defects/cracks do not significantly affect the response of graphite, the kinetics on MoS2 systematically accelerate with small increase in disorder. These findings have direct implications for use of MoS2 and graphene/graphite as electrode materials in electrochemistry-related applications
Graphene-Based Technologies for Tackling COVID-19 and Future Pandemics
10.1002/adfm.202107407ADVANCED FUNCTIONAL MATERIALS315
Probing the Nature of Defects in Graphene by Raman Spectroscopy
Raman spectroscopy is able to probe disorder in graphene
through
defect-activated peaks. It is of great interest to link these features
to the nature of disorder. Here we present a detailed analysis of
the Raman spectra of graphene containing different type of defects.
We found that the intensity ratio of the D and D′ peak is maximum
(∼13) for sp<sup>3</sup>-defects, it decreases for vacancy-like
defects (∼7), and it reaches a minimum for boundaries in graphite
(∼3.5). This makes Raman Spectroscopy a powerful tool to fully
characterize graphene
京都大學新聞 第1906号
春の就職問題特集