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Eli Sutter & Peter W. Sutter
talk with ScienceWatch.com and answer a few questions
about this month's Fast Moving Fronts paper in the
Multidisciplinary field. The authors have also sent along
images of their work.
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Article: Epitaxial graphene on ruthenium
Authors: Sutter, PW;Flege, JI;Sutter,
EA
Journal: NAT MATER, 7 (5): 406-411 MAY 2008
Addresses: Brookhaven Natl Lab, Ctr Funct Nanomat, Upton, NY
11973 USA.
Brookhaven Natl Lab, Ctr Funct Nanomat, Upton, NY 11973 USA.
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Why do you think your paper is highly
cited?
At the time our paper was published,
graphene
had shown extraordinary properties, such as high charge-carrier mobilities,
chemical inertness, and extreme mechanical strength. But a scalable method
for large-scale synthesis, necessary to pursue further research and
possibly translate some of these properties into technological
applications, had been lacking.
The leading contender at the time, epitaxial graphene on silicon carbide,
had produced material with good electronic properties, but was also plagued
by problems: small size of graphene domains; poor thickness uniformity; and
the inability to isolate the graphene from the substrate.
At this critical time, our paper demonstrated that transition metal
substrates can be used to grow high-quality epitaxial graphene with
macroscopic domain sizes and excellent thickness uniformity. Later work by
other groups has demonstrated ways to isolate the graphene from the metal,
making it available for a wide range of applications.
Does it describe a new discovery, methodology, or
synthesis of knowledge? Would you summarize the significance of your
paper in layman’s terms?
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Epitaxy transition
metals - scalable
graphene synthesis for
large-scale
applications.
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SEM image at the early
stages of graphene
growth on
ruthenium—partial
surface coverage by
macroscopic graphene
domains.
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The fact that transition metals catalyze the growth of graphitic carbon
layers has been known since at least the late 1970s, primarily because such
layers suppress chemical reactions on these metals.
The discovery of graphene's interesting properties has provided an entirely
new context for such work. Using real-time microscopy during the growth
process, our work was first to demonstrate the extraordinary control in
graphene epitaxy offered by metal substrates, such as ruthenium.
Graphene domains—the two-dimensional equivalent of grains in a
polycrystalline material—grow to macroscopic size (several hundred
microns), are uniform in thickness, and join together to cover arbitrarily
large surface areas. These characteristics ideally fulfilled the
requirements for a scalable graphene synthesis method.
The large domain size implies extremely long diffusion lengths of carbon
atoms on the metal, but also a special way in which a coherent graphene
sheet accommodates atomic layer high surface steps that are ubiquitous on
metal surfaces and typically spaced less than 100 nm apart. The graphene
flows seamlessly across these steps, akin to a carpet rolled down a flight
of stairs.
How did you become involved in this research and
were any particular problems encountered along the way?
Our group has been working on fundamental mechanisms of epitaxial growth
and nanostructure formation for a long time, and has a long track record of
using in situ microscopy to study growth processes.
Having used transition metal substrates, such as ruthenium and platinum,
for other research, it was a small step to applying our knowledge and
experience towards understanding the growth and properties of epitaxial
graphene.
Where do you see your research leading in the
future?
We have successfully demonstrated the large-scale synthesis of high-quality
graphene on metals, thus paving the way for the production of material for
the "top-down" fabrication of useful structures. The next challenge in the
field is the development of a methodology for the atomically precise
"bottom-up" synthesis of graphene nanostructures.
A wealth of theoretical work has predicted unusual, but potentially very
useful functionalities arising when charge carriers are confined inside
narrow graphene ribbons or other structures with reduced dimensionality.
To harness these properties, however, a ribbon would need to be uniformly
narrow, merely a few of graphene's characteristic honeycomb units wide,
with atomically straight and smooth edges. We believe that graphene
assembly on transition metals can be a key player in realizing this vision.
Do you foresee any social or political
implications for your research?
We have already seen a sharp rise in the research funding for work on
graphene, and specifically to address the need for scalable synthesis
methods. The promise stands that the extreme properties and relative
robustness of graphene, combined with the fact that carbon is among the
most abundant elements on our planet, will enable broad applications in
areas such as energy efficiency and renewable energy conversion.
Peter Sutter
Staff Scientist
Center for Functional Nanomaterials
Brookhaven National Laboratory
Upton, NY, USA
Eli Sutter
Staff Scientist
Center for Functional Nanomaterials
Brookhaven National Laboratory
Upton, NY, USA
KEYWORDS: CARBON NANOTUBES; GRAPHITE; LEED; GAS.
