79 research outputs found
Electrical transport and low-temperature scanning tunneling microscopy of microsoldered graphene
Using the recently developed technique of microsoldering, we perform a
systematic transport study of the influence of PMMA on graphene flakes
revealing a doping effect of up to 3.8x10^12 1/cm^2, but a negligible influence
on mobility and gate voltage induced hysteresis. Moreover, we show that the
microsoldered graphene is free of contamination and exhibits a very similar
intrinsic rippling as has been found for lithographically contacted flakes.
Finally, we demonstrate a current induced closing of the previously found
phonon gap appearing in scanning tunneling spectroscopy experiments, strongly
non-linear features at higher bias probably caused by vibrations of the flake
and a B-field induced double peak attributed to the 0.Landau level of graphene.Comment: 8 pages, 3 figure
High On/Off Ratios in Bilayer Graphene Field Effect Transistors Realized by Surface Dopants
The unique property of bilayer graphene to show a band gap tunable by
external electrical fields enables a variety of different device concepts with
novel functionalities for electronic, optoelectronic and sensor applications.
So far the operation of bilayer graphene based field effect transistors
requires two individual gates to vary the channel's conductance and to create a
band gap. In this paper we report on a method to increase the on/off ratio in
single gated bilayer graphene field effect transistors by adsorbate doping. The
adsorbate dopants on the upper side of the graphene establish a displacement
field perpendicular to the graphene surface breaking the inversion symmetry of
the two graphene layers. Low temperature measurements indicate, that the
increased on/off ratio is caused by the opening of a mobility gap. Beside field
effect transistors the presented approach can also be employed for other
bilayer graphene based devices like photodetectors for THz to infrared
radiation, chemical sensors and in more sophisticated structures such as
antidot- or superlattices where an artificial potential landscape has to be
created.Comment: 4 pages, 4 figure
Non-volatile switching in graphene field effect devices
The absence of a band gap in graphene restricts its straight forward
application as a channel material in field effect transistors. In this letter,
we report on a new approach to engineer a band gap in graphene field effect
devices (FED) by controlled structural modification of the graphene channel
itself. The conductance in the FEDs is switched between a conductive "on-state"
to an insulating "off-state" with more than six orders of magnitude difference
in conductance. Above a critical value of an electric field applied to the FED
gate under certain environmental conditions, a chemical modification takes
place to form insulating graphene derivatives. The effect can be reversed by
electrical fields of opposite polarity or short current pulses to recover the
initial state. These reversible switches could potentially be applied to
non-volatile memories and novel neuromorphic processing concepts.Comment: 14 pages, 4 figures, submitted to IEEE ED
Oxygen Surface Functionalization of Graphene Nanoribbons for Transport Gap Engineering
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