30 research outputs found
Transconductance fluctuations as a probe for interaction induced quantum Hall states in graphene
Transport measurements normally provide a macroscopic, averaged view of the
sample, so that disorder prevents the observation of fragile interaction
induced states. Here, we demonstrate that transconductance fluctuations in a
graphene field effect transistor reflect charge localization phenomena on the
nanometer scale due to the formation of a dot network which forms near
incompressible quantum states. These fluctuations give access to fragile
broken-symmetry and fractional quantum Hall states even though these states
remain hidden in conventional magnetotransport quantities.Comment: 6 pages, 3 figure
Correlation between resistance fluctuations and temperature dependence of conductivity in graphene
The weak temperature dependence of the resistance R(T) of monolayer
graphene1-3 indicates an extraordinarily high intrinsic mobility of the charge
carriers. Important complications are the presence of mobile scattering centres
that strongly modify charge transport, and the presence of strong mesoscopic
conductance fluctuations that, in graphene, persist to relatively high
temperatures4,5. In this Letter, we investigate the surprisingly varied changes
in resistance that we find in graphene flakes as temperature is lowered below
70 K. We propose that these changes in R(T) arise from the temperature
dependence of the scattered electron wave interference that causes the
resistance fluctuations. Using the field effect transistor configuration, we
verify this explanation in detail from measurements of R(T) by tuning to
different gate voltages corresponding to particular features of the resistance
fluctuations. We propose simple expressions that model R(T) at both low and
high charge carrier densities
Enhanced Tunnelling in a Hybrid of Single-Walled Carbon Nanotubes and Graphene
Transparent and conductive films (TCFs) are of great technological
importance. The high transmittance, electrical conductivity and mechanical
strength make single-walled carbon nanotubes (SWCNTs) a good candidate for
their raw material. Despite the ballistic transport in individual SWCNTs,
however, the electrical conductivity of their networks is limited by low
efficiency of charge tunneling between the tube elements. Here, we demonstrate
that the nanotube network sheet resistance at high optical transmittance is
decreased by more than 50% when fabricated on graphene and thus provides a
comparable improvement as widely adopted gold chloride ()
doping. However, while Raman spectroscopy reveals substantial changes in
spectral features of doped nanotubes, no similar effect is observed in presence
of graphene. Instead, temperature dependent transport measurements indicate
that graphene substrate reduces the tunneling barrier heights while its
parallel conductivity contribution is almost negligible. Finally, we show that
combining the graphene substrate and doping, the SWCNT thin
films can exhibit sheet resistance as low as 36 /sq. at 90%
transmittance.Comment: 21 pages, 6 figure
Defects in bilayer silica and graphene: common trends in diverse hexagonal two-dimensional systems
Peer reviewe