Science Current Events | Science News | Brightsurf.com
 

A Direct Look at Graphene

August 02, 2012
Perhaps no other material is generating as much excitement in the electronics world as graphene, sheets of pure carbon just one atom thick through which electrons can race at nearly the speed of light - 100 times faster than they move through silicon. Superthin, superstrong, superflexible and superfast as an electrical conductor, graphene has been touted as a potential wonder material for a host of electronic applications, starting with ultrafast transistors. For the vast potential of graphene to be fully realized, however, scientists must first learn more about what makes graphene so super. The latest step in this direction has been taken by researchers with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley.

Michael Crommie, a physicist who holds joint appointments with Berkeley Lab's Materials Sciences Division and UC Berkeley's Physics Department, led a study in which the first direct observations at microscopic lengths were recorded of how electrons and holes respond to a charged impurity - a single Coulomb potential - placed on a gated graphene device. The results provide experimental support to the theory that interactions between electrons are critical to graphene's extraordinary properties.

"We've shown that electrons in graphene behave very differently around charged impurities than electrons in other materials," Crommie says. "Some researchers have held that electron-electron interactions are not important to intrinsic graphene properties while others have argued they are. Our first-time-ever pictures of how ultra-relativistic electrons re-arrange themselves in response to a Coulomb potential come down on the side of electron-electron interactions being an important factor."

Crommie is the corresponding author of a paper describing this study published in the journal Nature Physics. The paper is titled "Mapping Dirac quasiparticles near a single Coulomb impurity on graphene." Co-authoring this paper were Yang Wang, Victor Brar, Andrey Shytov, Qiong Wu, William Regan, Hsin-Zon Tsai, Alex Zettl and Leonid Levitov.

Graphene sheets are composed of carbon atoms arranged in a two-dimensional hexagonally patterned lattice, like a honeycomb. Electrons moving through this honeycomb lattice perfectly mimic the behavior expected of highly relativistic charged particles with no mass: think of a ray of light that is electrically charged. Because this is the same behavior displayed by highly relativistic free electrons, charge-carriers in graphene are referred to as "Dirac quasiparticles," after Paul Dirac, the scientist who first described the behavior of relativistic fermions in 1928.

"In graphene, electrons behave as massless Dirac fermions," Crommie says. "As such, the response of these electrons to a Coulomb potential is predicted to differ significantly from how non-relativistic electrons behave in traditional atomic and impurity systems. However, until now, many key theoretical predictions for this ultra-relativistic system had not been tested."

Working with a specially equipped scanning tunneling microscope (STM)in ultra-high vacuum, Crommie and his colleagues probed gated devices consisting of a graphene layer deposited atop boron nitride flakes which were themselves placed on a silicon dioxide substrate, the most common of semiconductor substrates.

"The use of boron-nitride significantly reduced the charge inhomogeneity of graphene, thereby allowing us to probe the intrinsic graphene electronic response to individual charged impurities," Crommie says. In this study, the charged impurities were cobalt trimers constructed on graphene by atomically manipulating cobalt monomers with the tip of an STM."

The STM used to fabricate the cobalt trimers was also used to map (through spatial variation in the electronic structure of the graphene) the response of Dirac quasiparticles - both electron-like and hole-like - to the Coulomb potential created by the trimers. Comparing the observed electron-hole asymmetry to theoretical simulations allowed the research team to not only test theoretical predictions for how Dirac fermions behave near a Coulomb potential, but also to extract graphene's dielectric constant.

"Theorists have predicted that compared with other materials, electrons in graphene are pulled into a positively-charged impurity either too weakly, the subcritical regime; or too strongly, the supercritical regime," Crommie says. "In our study, we verified the predictions for the subcritical regime and found the value for the dielectric to be small enough to indicate that electron-electron interactions contribute significantly to graphene properties. This information is fundamental to our understanding of how electrons move through graphene."

This research was supported by the DOE Office of Science, the Office of Naval Research, and the National Science Foundation.

Lawrence Berkeley National Laboratory


Related Graphene Current Events and Graphene News Articles


Thinnest feasible membrane produced
Researchers have produced a stable porous membrane that is thinner than a nanometre. This is a 100,000 times thinner than the diameter of a human hair.

Scientists observe quantum superconductor-metal transition and superconducting glass
The article "Collapse of superconductivity in a hybrid tin-grapheme Josephson junction array'" presents the results of the first experimental study of the graphene-based quantum phase transition of the "superconductor-to-metal" type, i.e. transformation of the system's ground state from superconducting to metallic, upon changing the electron concentration in graphene sheet.

Better solar cells, better LED light and vast optical possibilities
Changes at the atom level in nanowires offer vast possibilities for improvement of solar cells and LED light. NTNU-researchers have discovered that by tuning a small strain on single nanowires they can become more effective in LEDs and solar cells.

Scalable CVD process for making 2-D molybdenum diselenide
Nanoengineering researchers at Rice University and Nanyang Technological University in Singapore have unveiled a potentially scalable method for making one-atom-thick layers of molybdenum diselenide - a highly sought semiconductor that is similar to graphene but has better properties for making certain electronic devices like switchable transistors and light-emitting diodes.

Rebar technique strengthens case for graphene
Carbon nanotubes are reinforcing bars that make two-dimensional graphene much easier to handle in a new hybrid material grown by researchers at Rice University.

Graphene nanoribbons as electronic switches
One of graphene's most sought-after properties is its high conductivity. Argentinian and Brazilian physicists have now successfully calculated the conditions of the transport, or conductance mechanisms, in graphene nanoribbons.

Researchers probe the next generation of 2-D materials
As the properties and applications of graphene continue to be explored in laboratories all over the world, a growing number of researchers are looking beyond the one-atom-thick layer of carbon for alternative materials that exhibit similarly captivating properties.

Tiny power generator runs on spit
Saliva-powered micro-sized microbial fuel cells can produce minute amounts of energy sufficient to run on-chip applications, according to an international team of engineers.

How electrodes charge and discharge
The electrochemical reactions inside the porous electrodes of batteries and fuel cells have been described by theorists, but never measured directly. Now, a team at MIT has figured out a way to measure the fundamental charge transfer rate - finding some significant surprises.

USC Viterbi researchers developing cheap, better-performing lithium-ion batteries
Researchers at the USC Viterbi School of Engineering have improved the performance and capacity of lithium batteries by developing better-performing, cheaper materials for use in anodes and cathodes (negative and positive electrodes, respectively).
More Graphene Current Events and Graphene News Articles

How To Make Your Fortune In The Graphene Revolution.

How To Make Your Fortune In The Graphene Revolution.


Investing in graphene is perhaps the most talked about prospect in the world of investment. With fantastic year-on-year growth projected, no other investment offers the small investor the chance to join an epoch changing industry that is expected to transform the commercial world over the next twenty years.

Whether you are looking for a penny stock to invest in or prefer to place your money in the safer hands of larger companies, you'll find some of the best share investments of the century inside. Graphene is almost guaranteed to be a world changing material, so why not let it change your financial situation too.

Having researched and followed the industry for several years and with a website dedicated to the subject you can be sure you'll be guided by one of...

Graphene: A New Paradigm in Condensed Matter and Device Physics

Graphene: A New Paradigm in Condensed Matter and Device Physics
by E. L. Wolf (Author)


The book is an introduction to the science and possible applications of Graphene, the first one-atom-thick crystalline form of matter. Discovered in 2004 by now Nobelists Geim and Novoselov, the single layer of graphite, a hexagonal network of carbon atoms, has astonishing electrical and mechanical properties. It supports the highest electrical current density of any material, far exceeding metals copper and silver. Its absolute minimum thickness, 0.34 nanometers, provides an inherent advantage in possible forms of digital electronics past the era of Moore's Law.

The book describes the unusual physics of the material, that it offers linear rather than parabolic energy bands. The Dirac-like electron energy bands lead to high constant carrier speed, similar to light photons. The...

Graphene: Synthesis, Properties, and Phenomena

Graphene: Synthesis, Properties, and Phenomena
by C. N. R. Rao (Editor), Ajay K. Sood (Editor)


Since its discovery in 2004, graphene has been a great sensation due to its unique structure and unusual properties, and it has only taken
6 years for a Noble Prize to be awarded for the field of graphene research. This monograph gives a well-balanced overview on all areas of
scientific interest surrounding this fascinating nanocarbon. In one handy volume it offers comprehensive coverage of the topic, including
chemical, materials science, nanoscience, physics, engineering, life science, and potential applications. Other graphene-like, inorganic layered materials are also discussed.

Edited by two highly honored scientists, this is an invaluable companion for inorganic, organic, and physical chemists, materials scientists,
and physicists.

From the...

Graphene: Fundamentals and emergent applications

Graphene: Fundamentals and emergent applications
by Jamie H. Warner (Author), Franziska Schaffel (Author), Mark Rummeli (Author), Alicja Bachmatiuk (Author)


Providing fundamental knowledge necessary to understand graphene's atomic structure, band-structure, unique properties and an overview of groundbreaking current and emergent applications, this new handbook is essential reading for materials scientists, chemists and physicists. Since the 2010 physics Nobel Prize awarded to Geim and Novosolev for their groundbreaking work isolating graphene from bulk graphite, there has been a huge surge in interest in the area. This has led to a large number of news books on graphene. However, for such a vast inflow of new entrants, the current literature is surprisingly slight, focusing exclusively on current research or books on previous "hot topic" allotropes of carbon. This book covers fundamental groundwork of the structure, property,...

Carbon Nanotube and Graphene Device Physics

Carbon Nanotube and Graphene Device Physics
by H.-S. Philip Wong (Author), Deji Akinwande (Author)


Explaining the properties and performance of practical nanotube devices and related applications, this is the first introductory textbook on the subject. All the fundamental concepts are introduced, so that readers without an advanced scientific background can follow all the major ideas and results. Additional topics covered include nanotube transistors and interconnects, and the basic physics of graphene. Problem sets at the end of every chapter allow readers to test their knowledge of the material covered and gain a greater understanding of the analytical skill sets developed in the text. This is an ideal textbook for senior undergraduate and graduate students taking courses in semiconductor device physics and nanoelectronics. It is also a perfect self-study guide for professional...

Graphene: Carbon in Two Dimensions

Graphene: Carbon in Two Dimensions
by Mikhail I. Katsnelson (Author)


Graphene is the thinnest known material, a sheet of carbon atoms arranged in hexagonal cells a single atom thick, and yet stronger than diamond. It has potentially significant applications in nanotechnology, 'beyond-silicon' electronics, solid-state realization of high-energy phenomena and as a prototype membrane which could revolutionise soft matter and 2D physics. In this book, leading graphene research theorist Mikhail Katsnelson presents the basic concepts of graphene physics. Topics covered include Berry phase, topologically protected zero modes, Klein tunneling, vacuum reconstruction near supercritical charges, and deformation-induced gauge fields. The book also introduces the theory of flexible membranes relevant to graphene physics and discusses electronic transport, optical...

Introduction to Graphene-Based Nanomaterials: From Electronic Structure to Quantum Transport

Introduction to Graphene-Based Nanomaterials: From Electronic Structure to Quantum Transport
by Luis E. F. Foa Torres (Author), Stephan Roche (Author), Jean-Christophe Charlier (Author)


Beginning with an introduction to carbon-based nanomaterials, their electronic properties, and general concepts in quantum transport, this detailed primer describes the most effective theoretical and computational methods and tools for simulating the electronic structure and transport properties of graphene-based systems. Transport concepts are clearly presented through simple models, enabling comparison with analytical treatments, and multiscale quantum transport methodologies are introduced and developed in a straightforward way, demonstrating a range of methods for tackling the modelling of defects and impurities in more complex graphene-based materials. The authors also discuss the practical applications of this revolutionary nanomaterial, contemporary challenges in theory and...

The Millionaire Investor Better than gold, diamonds or real-estate: Graphene: How a new disruptive technology is changing the world, and we can become rich with it

The Millionaire Investor Better than gold, diamonds or real-estate: Graphene: How a new disruptive technology is changing the world, and we can become rich with it
by Dr. Elmar P. Selbach (Author)


NEW AND UPDATED CONTENT! New chapters, new companies added. Many pictures and up-to date content! Buy NOW! Who hasn’t heard about people who restlessly scan the market for stocks that perform extraordinarily? One of the companies that has skyrocketed in the past years is Microsoft. Whatever you’d invested in the 1980s – you became rich within 15 years. In this book, I want to show that a similar scenario is possible. One can become rich by investing in the right stocks. But, not by tricks, cheats or any other miraculous recipe. No. Just by observing the dramatic changes in an area of technology that is so far only known to insiders. We will see the dawn of a fascinating new era. The consequences of the changes ahead of us will change our world much more than any event before....

The Graphene Handbook

The Graphene Handbook
by Ron Mertens (Author)


The Graphene Handbook is a comprehensive guide to graphene technology, industry and market - brought to you by Graphene-Info.

Graphene Nanomaterials

Graphene Nanomaterials
by Kal R. Sharma (Author)


Since the discovery of graphene as a distinct allotrope of carbon, with its potential to further increase the speed of microprocessors beyond 30 peta hertz, there has been a void in resources for students and practitioners-until now. This book provides information on the synthesis, characterization, application development, scaleup, stability analysis and structure property relations of graphene nanomaterials. Different methods of fabrication of graphenes are included, and the author discusses cost of production starting from capital costs, operating costs, and total optimal costs. These different processes to make graphene include: Roll to Roll Transfer Process, Low Pressure Chemical Vapor Deposition, Atmospheric Plug Flow Reactor, APFR, Dispersion Using NMP, and numerous others. Sharma...

© 2014 BrightSurf.com