In our Special Topic on Graphene, the paper "Peculiar
width dependence of the electronic properties of carbon
nanoribbons" (Phys. Rev. B 73[4]: art. no. 045432,
January 2006) by Professor Motohiko Ezawa is a key part of
the Research Front on
Graphene Nanoribbons. According to
Essential Science IndicatorsSMfrom
Thomson
Reuters, this paper has been cited 63 times since its
publication up to October 31, 2008. In the Web of
Science®, this paper shows 80 citations
to date.
Professor Ezawa is an Assistant Professor in the Department
of Applied Physics at the University of Tokyo.
In the interview below, he talks
with ScienceWatch.com about this highly cited
paper.
Would you please describe the significance of
your paper and why it is highly cited?
In my paper I have presented many classes of graphene nanoribbons and
proposed their systematic classification in terms of the edge shape and the
width. Nanoribbons have a wide variety of electronic properties depending
on the edge shape and the width. These electronic properties are amazingly
rich in comparison with those of carbon nanotubes. My paper is highly cited
probably because my work on nanoribbons provides the inspiration that
graphene nanostructure will be a promising candidate of future
nanoelectronic devices as an alternative of silicon devices.
How did you become involved in this research, and
were there any particular successes or obstacles that stand
out?
This is the first paper in my academic career, constituting a part of my
master thesis. When I was an undergraduate student, I was walking around in
the library of the chemistry department. I had an encounter with a bulletin
displaying a series of chemical polymer structures such as polyacene and
polyphenanthrene, which are now called graphene nanoribbons. These polymers
are studied in the context of chemical synthesizing. I was attracted to
these polymers since I thought their electronic properties would be
exceedingly interesting.
After coming back home, I immediately made a systematic analysis of
nanoribbons. I named this class of polymers "carbon nanoribbons" after
carbon nanotubes. I was unaware of experiments on graphene at that time.
Carbon nanoribbons are now known as graphene nanoribbons, as the graphene
physics is expanding dramatically.
The main obstacle is that I had very great difficulties publishing this
paper. It took 10 months for the paper to be published; in contrast, it
took only two months for calculations. Furthermore, my paper was rejected
by the first journal to which I submitted it.
Where do you see your research and the broader
field leading in the future?
Graphene nanoribbon is one of the graphene nanostructure derivatives. It is
a one-dimensional object. We may as well consider a zero-dimensional
derivative, which is graphene nanodisk (Ezawa M, "Metallic graphene
nanodisks: Electronic and magnetic properties", Phys. Rev. B 76:
art. no. 245415, 2007). Nanoribbons will be used as quantum wires, while
nanodisks will be used as quantum dots. Combinations of nanoribbons and
nanodisks will form electronic circuits. In future, nanoelectronic devices
will be made solely of graphene, where nanoribbons and nanodisks are basic
components. Graphene-based circuits will replace silicon-based circuits in
future.
What are the implications of your work for this
field?
First, my work has revealed that the electronic properties are very
sensitive to the edge shape and the width. This leads to a rich variety in
the electronic properties of nanoribbons. Second, the theoretical treatment
is relatively easy. Simple tight-binding calculations have been proven to
be very successful in contrast to the study of the transition metals. This
makes it possible to carry out a systematic analysis of many classes of
nanoribbons rather easily. Third, my work suggests applications of
nanoribbon to future nanoelectronic devices. I have suggested that the
combinations of nanoribbons will lead to further interesting
physics.
Motohiko Ezawa
Department of Applied Physics
University of Tokyo
Tokyo, Japan
Ezawa M, "Peculiar width dependence of the electronic
properties of carbon nanoribbons," Phys. Rev. B
73(4): art. no. 045432, January 2006. Source:
Essential Science Indicators from
Thomson
Reuters.