54 research outputs found
Strong Spin-Orbit Interaction Induced in Graphene by Monolayer WS
We demonstrate strong anisotropic spin-orbit interaction (SOI) in graphene
induced by monolayer WS. Direct comparison between graphene/monolayer
WS and graphene/bulk WS system in magnetotransport measurements reveals
that monolayer transition metal dichalcogenide (TMD) can induce much stronger
SOI than bulk. Detailed theoretical analysis of the weak-antilocalization
curves gives an estimated spin-orbit energy () higher than 10 meV.
The symmetry of the induced SOI is also discussed, and the dominant
symmetric SOI can only explain the experimental results.
Spin relaxation by the Elliot-Yafet (EY) mechanism and anomalous resistance
increase with temperature close to the Dirac point indicates Kane-Mele (KM) SOI
induced in graphene.Comment: 5 pages, 4 figure
A facile way to produce epoxy nanocomposites having excellent thermal conductivity with low contents of reduced graphene oxide
A well-dispersed phase of exfoliated graphene oxide (GO) nanosheets was
initially prepared in water. This was concentrated by centrifugation and was
mixed with a liquid epoxy resin. The remaining water was removed by evaporation,
leaving a GO dispersion in epoxy resin. A stoichiometric amount of an
anhydride curing agent was added to this epoxy-resin mixture containing the
GO nanosheets, which was then cured at 90 C for 1 h followed by 160 C for
2 h. A second thermal treatment step of 200 C for 30 min was then undertaken
to reduce further the GO in situ in the epoxy nanocomposite. An examination of
the morphology of such nanocomposites containing reduced graphene oxide
(rGO) revealed that a very good dispersion of rGO was achieved throughout the
epoxy polymer. Various thermal and mechanical properties of the epoxy
nanocomposites were measured, and the most noteworthy finding was a
remarkable increase in the thermal conductivity when relatively very low contents
of rGO were present. For example, a value of 0.25 W/mK was measured at
30 C for the nanocomposite with merely 0.06 weight percentage (wt%) of rGO
present, which represents an increase of *40% compared with that of the
unmodified epoxy polymer. This value represents one of the largest increases in
the thermal conductivity per wt% of added rGO yet reported. These observations
have been attributed to the excellent dispersion of rGO achieved in these
nanocomposites made via this facile production method. The present results
show that it is now possible to tune the properties of an epoxy polymer with a
simple and viable method of GO addition.
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High-Mobility and High-Optical Quality Atomically Thin WS 2
The rise of atomically thin materials has the potential to enable a paradigm shift in modern technologies by introducing multi-functional materials in the semiconductor industry. To date the growth of high quality atomically thin semiconductors (e.g. WS2) is one of the most pressing challenges to unleash the potential of these materials and the growth of mono- or bi-layers with high crystal quality is yet to see its full realization. Here, we show that the novel use of molecular precursors in the controlled synthesis of mono- and bi-layer WS2 leads to superior material quality compared to the widely used direct sulfidization of WO3-based precursors. Record high room temperature charge carrier mobility up to 52 cm2/Vs and ultra-sharp photoluminescence linewidth of just 36 meV over submillimeter areas demonstrate that the quality of this material supersedes also that of naturally occurring materials. By exploiting surface diffusion kinetics of W and S species adsorbed onto a substrate, a deterministic layer thickness control has also been achieved promoting the design of scalable synthesis routes
Platinum deposition on functionalised graphene for corrosion resistant oxygen reduction electrodes
Graphene-related materials are promising supports for electrocatalysts due to their stability and high surface area. Their innate surface chemistries can be controlled and tuned via functionalisation to improve the stability of both the carbon support and the metal catalyst. Functionalised graphenes were prepared using either aryl diazonium functionalisation or non-destructive chemical reduction, to provide groups adapted for platinum deposition. XPS and TGA-MS measurements confirmed the presence of polyethyleneglycol and sulfur-containing functional groups, and provided consistent values for the extent of the reactions. The deposited platinum nanoparticles obtained were consistently around 2 nm via reductive chemistry and around 4 nm via the diazonium route. Although these graphene-supported electrocatalysts provided a lower electrochemical surface area (ECSA), functionalised samples showed enhanced specific activity compared to a commercial platinum/carbon black system. Accelerated stress testing (AST) showed improved durability for the functionalised graphenes compared to the non-functionalised materials, attributed to edge passivation and catalyst particle anchoring
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