Light-Speed Nanotech: Controlling the Nature of Graphene

January 22, 2009

Researchers "tune" graphene's properties by growing it on different surfaces

Researchers at Rensselaer Polytechnic Institute have discovered a new method for controlling the nature of graphene, bringing academia and industry potentially one step closer to realizing the mass production of graphene-based nanoelectronics.

Graphene, a one-atom-thick sheet of carbon, was discovered in 2004 and is considered a potential heir to copper and silicon as the fundamental building blocks of nanoelectronics.

With help from an underlying substrate, researchers for the first time have demonstrated the ability to control the nature of graphene. Saroj Nayak, an associate professor in Rensselaer's Department of Physics, Applied Physics, and Astronomy, along with Philip Shemella, a postdoctoral research associate in the same department, have determined that the chemistry of the surface on which graphene is deposited plays a key role in shaping the material's conductive properties. The results are based on large-scale quantum mechanical simulations.

Results show that when deposited on a surface treated with oxygen, graphene exhibits semiconductor properties. When deposited on a material treated with hydrogen, however, graphene exhibits metallic properties.

"Depending on the chemistry of the surface, we can control the nature of the graphene to be metallic or semiconductor," Nayak said. "Essentially, we are 'tuning' the electrical properties of material to suit our needs."

Conventionally, whenever a batch of graphene nanostructures is produced, some of the graphene is metallic, while the rest is semiconductor. It would be nearly impossible to separate the two on a large scale, Nayak said, yet realizing new graphene devices would require that they be comprised solely of metallic or semiconductor graphene. The new method for "tuning" the nature of graphene is a key step to making this possible, he said.

Graphene's excellent conductive properties make it attractive to researchers. Even at room temperature, electrons pass effortlessly, near the speed of light and with little resistance. This means a graphene interconnect would likely stay much cooler than a copper interconnect of the same size. Cooler is better, as heat produced by interconnects can have negative effects on both a computer chip's speed and performance.

Results of the study were published this week in the paper "Electronic structure and band-gap modulation of graphene via substrate surface chemistry" in Applied Physics Letters, and are featured on the cover of the journal's January 19 issue.

Large-scale quantum simulations for the study were run on Rensselaer's supercomputing system, the Computational Center for Nanotechnology Innovations (CCNI).

Researchers received funding for the project from the New York State Interconnect Focus Center at Rensselaer.

Rensselaer Polytechnic Institute

---

---

	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...
	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: Synthesis and Applications (Nanomaterials and their Applications) by Wonbong Choi (Editor), Jo-won Lee (Editor) Since the late 20th century, graphene—a one-atom-thick planar sheet of sp2-bonded carbon atoms densely packed in a honeycomb crystal lattice—has garnered appreciable attention as a potential next-generation electronic material due to its exceptional properties. These properties include high current density, ballistic transport, chemical inertness, high thermal conductivity, optical transmittance, and super hydrophobicity at nanometer scale. In contrast to research on its excellent electronic and optoelectronic properties, research on the syntheses of a single sheet of graphene for industrial applications is in its nascent stages. Graphene: Synthesis and Applications reviews the advancement and future directions of graphene research in the areas of synthesis and properties, and...
	Graphene and Its Fascinating Attributes by Swapan K. Pati (Editor), Toshiaki Enoki (Editor), C. N. R. Rao (Editor) Graphene, a single sheet of graphite, has an unconventional electronic structure that can be described in terms of massless Dirac Fermions. This interesting electronic feature is not only an important fundamental issue in condensed matter physics but also holds future promise in post-Si electronic/spintronics device applications. Graphene is the most fundamental building block, with which a variety of carbon-based materials such as graphite, fullerene and carbon nanotubes can be created. The diverse chemical, electronic and magnetic properties of nanographene and graphene are mainly due to their geometrical electronic structure. This book presents the frontiers of graphene research ranging from important issues in condensed matter physics and chemistry to advanced device applications.
	Graphene and Graphite Materials by H. E. Chan (Editor) Graphene is a nanomaterial combining very simple atomic structure with intriguingly complex and largely unexplored physics. Since its first isolation about four years ago researchers suggested a large number of applications for this material in anticipation of future technological revolutions. In particular, graphene is considered as a potential candidate for replacing silicon in future electronic devices. Graphene is a perfect example of the wonders of nanotechnology, in which common substances are scaled down to an atomic level to uncover new and exciting possibilities. The mineral graphite is one of the allotropes of carbon. Unlike diamond (another carbon allotrope), graphite is an electrical conductor, a semimetal, and can be used, for instance, in the electrodes of an arc lamp. This...
	Raman Spectroscopy in Graphene Related Systems by Ado Jorio (Author), Mildred S. Dresselhaus (Author), Riichiro Saito (Author), Gene Dresselhaus (Author) Recent work has shown that Raman spectroscopy has potential to become one of the most important tools for nanoscience and nanometrology, i.e. for standardization and industrial quality of goods based on nanoscience. However, Raman spectroscopy is perceived as being too complicated for a non-specialist. This book is aimed to be a pedagogic reference to educate the community on how they can use Raman spectroscopy to study and characterize nanostructured materials. It will drive students, researchers and engineers towards the development of future research and applications of new forms of carbon as well as the use of Raman spectroscopy for nanometrology of carbon nanotubes, nanographite and graphene.
	Graphene Nanoelectronics: Metrology, Synthesis, Properties and Applications (NanoScience and Technology) by Hassan Raza (Editor) Graphene is a perfectly two-dimensional single-atom thin membrane with zero bandgap. It has attracted huge attention due to its linear dispersion around the Dirac point, excellent transport properties, novel magnetic characteristics, and low spin-orbit coupling. Graphene and its nanostructures may have potential applications in spintronics, photonics, plasmonics and electronics. This book brings together a team of experts to provide an overview of the most advanced topics in theory, experiments, spectroscopy and applications of graphene and its nanostructures. It covers the state-of-the-art in tutorial-like and review-like manner to make the book useful not only to experts, but also newcomers and graduate students.
	Quantum Mechanics for Nanostructures by Vladimir V. Mitin (Author), Dmitry I. Sementsov (Author), Nizami Z. Vagidov (Author) The properties of new nanoscale materials, their fabrication and applications, as well as the operational principles of nanodevices and systems, are solely determined by quantum-mechanical laws and principles. This textbook introduces engineers to quantum mechanics and the world of nanostructures, enabling them to apply the theories to numerous nanostructure problems. The textbook covers the fundamentals of quantum mechanics, including uncertainty relations, the Schrödinger equation, perturbation theory, and tunneling. These are then applied to a quantum dot, the smallest artificial atom, and compared to hydrogen, the smallest atom in nature. Nanoscale objects with higher dimensionality, such as quantum wires and quantum wells, are introduced, as well as nanoscale materials and...
	Graphene Nanoelectronics: From Materials to Circuits by Raghu Murali (Editor) Graphene has emerged as a potential candidate to replace traditional CMOS for a number of electronic applications; this book presents the latest advances in graphene nanoelectronics and the potential benefits of using graphene in a wide variety of electronic applications. The book also provides details on  various methods to grow graphene, including epitaxial, CVD, and chemical methods. This book serves as a spring-board for anyone trying to start working on graphene. The book is also suitable to experts who wish to update themselves with the latest findings in the field.
	MECHANICALLY EXFOLIATED SINGLE AND MULTILAYER GRAPHENE SHEETS: GRAPHENE FIELD EFFECT TRANSISTOR by Selin Manukyan (Author) Graphene is a single layer of graphite sheet; one atom thick sp2-bonded carbon atoms organized on a plane. It has extremely interesting electrical properties, which offers various applications in a number of nanometer scale devices, potentially operating at high frequency ranges. Mechanically exfoliated single and multilayer graphene sheets are prepared on (100) oriented silicon wafers with 300 nm thermal oxide. These graphene layers are characterized by optical microscopy, Atomic Force Microscopy (AFM) and Raman Spectroscopy. A graphene feld effect transistor is fabricated on a 35x9 micron graphene sheet by manually applying the drain and source contacts using silver paint and using the silicon substrate as backgate. In this thesis, the production methods, characterization methods and...