333 research outputs found
Comeback of epitaxial graphene for electronics: large-area growth of bilayer-free graphene on SiC
We present a new fabrication method for epitaxial graphene on SiC which
enables the growth of ultra-smooth defect- and bilayer-free graphene sheets
with an unprecedented reproducibility, a necessary prerequisite for wafer-scale
fabrication of high quality graphene-based electronic devices. The inherent but
unfavorable formation of high SiC surface terrace steps during high temperature
sublimation growth is suppressed by rapid formation of the graphene buffer
layer which stabilizes the SiC surface. The enhanced nucleation is enforced by
decomposition of polymer adsorbates which act as a carbon source. With most of
the steps well below 0.75 nm pure monolayer graphene without bilayer inclusions
is formed with lateral dimensions only limited by the size of the substrate.
This makes the polymer assisted sublimation growth technique the most promising
method for commercial wafer scale epitaxial graphene fabrication. The
extraordinary electronic quality is evidenced by quantum resistance metrology
at 4.2 K with until now unreached precision and high electron mobilities on mm
scale devices.Comment: 20 pages, 6 Figure
Operation of graphene quantum Hall resistance standard in a cryogen-free table-top system
We demonstrate quantum Hall resistance measurements with metrological
accuracy in a small cryogen-free system operating at a temperature of around
3.8K and magnetic fields below 5T. Operating this system requires little
experimental knowledge or laboratory infrastructure, thereby greatly advancing
the proliferation of primary quantum standards for precision electrical
metrology. This significant advance in technology has come about as a result of
the unique properties of epitaxial graphene on SiC.Comment: 15 pages, 9 figure
Quantum Hall resistance standards from graphene grown by chemical vapor deposition on silicon carbide
Replacing GaAs by graphene to realize more practical quantum Hall resistance
standards (QHRS), accurate to within in relative value, but operating
at lower magnetic fields than 10 T, is an ongoing goal in metrology. To date,
the required accuracy has been reported, only few times, in graphene grown on
SiC by sublimation of Si, under higher magnetic fields. Here, we report on a
device made of graphene grown by chemical vapour deposition on SiC which
demonstrates such accuracies of the Hall resistance from 10 T up to 19 T at 1.4
K. This is explained by a quantum Hall effect with low dissipation, resulting
from strongly localized bulk states at the magnetic length scale, over a wide
magnetic field range. Our results show that graphene-based QHRS can replace
their GaAs counterparts by operating in as-convenient cryomagnetic conditions,
but over an extended magnetic field range. They rely on a promising hybrid and
scalable growth method and a fabrication process achieving low-electron density
devices.Comment: 12 pages, 8 figure
Structured epitaxial graphene: growth and properties
graphene ; nano-structure ; electronic transport ; ballistic transportInternational audienceGraphene is generally considered to be a strong candidate to succeed silicon as an electronic material. However, to date, it actually has not yet demonstrated capabilities that exceed standard semiconducting materials. Currently demonstrated viable graphene devices are essentially limited to micron size ultrahigh frequency analog field effect transistors and quantum Hall effect devices for metrology. Nanoscopically patterned graphene tends to have disordered edges which severely reduce mobilities thereby obviating its advantage over other materials. Here we show that graphene grown on structured silicon carbide surfaces overcomes the edge roughness and promises to provide an inroad into nanoscale patterning of graphene. We show that high quality ribbons and rings can be made using this technique. We also report on progress towards high mobility graphene monolayers on silicon carbide for device applications
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