Nanotechnology Now

Our NanoNews Digest Sponsors



Heifer International

Wikipedia Affiliate Button


android tablet pc

Home > Press > Penn Scientists Demonstrate Potential of Graphene Films as Next-Generation Transistors

Abstract:
Physicists at the University of Pennsylvania have characterized an aspect of graphene film behavior by measuring the way it conducts electricity on a substrate. This milestone advances the potential application of graphene, the ultra-thin, single-atom thick carbon sheets that conduct electricity faster and more efficiently than silicon, the current material of choice for transistor fabrication.

Penn Scientists Demonstrate Potential of Graphene Films as Next-Generation Transistors

PHILADELPHIA, PA | Posted on July 31st, 2008

The research team, led by A.T. Charlie Johnson, professor in the Department of Physics and Astronomy at Penn, demonstrated that the surface potential above a graphene film varies with the thickness of the film, in quantitative agreement with the predictions of a nonlinear Thomas-Fermi theory of the interlayer screening by relativistic low energy charge carriers. The study appears online in the journal Nanoletters and will appear in print in the August edition.

Johnson's study, "Surface Potentials and Layer Charge Distributions in Few-Layer Graphene Films," clarifies experimentally the electronic interaction between an insulating substrate and few-layer graphene films, or FLGs, the standard model for next-generation transistors.

It is more practical to develop devices from FLGs, rather than single-layer materials. To make use of these films, graphene must be placed on a substrate to be functionalized as a transistor. Placing the film on a substrate causes an electronic interaction between the two materials that transfers carriers to or from, or "dopes," the FLG.

The focus of the Penn study was aimed at understanding how these doped charges distribute themselves among the different layers of graphene. The distribution of these charges determines the behavior of graphene transistors and other circuits, making it a critical component for device engineering. The team measured the surface potential of the material to determine how these doped charges were distributed along the transistor, as well as how the surface potential of the transistor varied with the number of layers of graphene employed.

Using electrostatic force microscopy measurements, the team characterized the surface potential of the graphene film and found it to be dependent on the thickness of the graphene layers. The thicker the carbon strips, the higher the electronic surface potential, with the surface potential approaching its limit for films that were five or more sheets thick. This behavior is unlike that found for conventional metals or semiconductors which would have, respectively, much shorter or longer screening lengths.

The surface potential measurements were in agreement with a theory developed by Penn professor and physicist Eugene Mele. The theory makes an important approximation, by treating electrostatic interactions in the film but neglecting quantum mechanical tunneling between neighboring layers. This allows the model to be solved analytically for the charge distribution and surface potential.

While prior theoretical work considered the effect of a substrate on the electronic structure of FLG, few experiments have directly probed the graphene-substrate interaction. Quantitative understanding of charge exchange at the interface and the spatial distribution of the resulting charge carriers is a critical input to device design.

Graphene-derived nanomaterials are a promising family of structures for application as atomically thin transistors, sensors and other nanoelectronic devices. These honeycomb sheets of sp2 -bonded carbon atoms and graphene sheets rolled into molecular cylinders share a set of electronic properties making them ideal for use in nanoelectronics: tunable carrier type and density, exceptionally high carrier mobility and structural control of their electronic band structures. A significant advantage of graphene is its two-dimensionality, making it compatible with existing planar device architectures. The challenge is realizing the potential of these materials by fabricating and insulating them on substrates.

The study was performed by Sujit S. Datta and Mele of the Department of Physics and Astronomy in the School of Arts and Sciences at Penn as well as Douglas R. Strachan of the Department of Physics and Astronomy and also the Department of Materials Science and Engineering within Penn's School of Engineering and Applied Science.

The study was funded by Penn's Nano/Bio Interface Center through the National Science Foundation, the Army Research Office and the Department of Energy.

####

For more information, please click here

Contacts:
Jordan Reese
215-573-6604

Copyright © University of Pennsylvania

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

Atom-thick CCD could capture images: Rice University scientists develop two-dimensional, light-sensitive material December 20th, 2014

Oregon researchers glimpse pathway of sunlight to electricity: Collaboration with Lund University uses modified UO spectroscopy equipment to study 'maze' of connections in photoactive quantum dots December 19th, 2014

Instant-start computers possible with new breakthrough December 19th, 2014

Aculon Hires New Business Development Director December 19th, 2014

Physics

SUNY Poly NanoCollege Faculty Member Selected as American Physical Society Fellow: SUNY Poly Associate Professor of Nanoscience Dr. Vincent LaBella Recognized for Significant Technological Innovations that Enable Interactive Learning December 17th, 2014

Fraud-proof credit card possible because of quantum physics December 16th, 2014

Nanoscale resistors for quantum devices: The electrical characteristics of new thin-film chromium oxide resistors that can be tuned by controlling the oxygen content detailed in the 'Journal of Applied Physics' December 9th, 2014

Unusual Electronic State Found in New Class of Unconventional Superconductors: Finding gives scientists a new group of materials to explore to unlock secrets of some materials' ability to carry current with no energy loss December 8th, 2014

Govt.-Legislation/Regulation/Funding/Policy

Atom-thick CCD could capture images: Rice University scientists develop two-dimensional, light-sensitive material December 20th, 2014

Oregon researchers glimpse pathway of sunlight to electricity: Collaboration with Lund University uses modified UO spectroscopy equipment to study 'maze' of connections in photoactive quantum dots December 19th, 2014

Switching to spintronics: Berkeley Lab reports on electric field switching of ferromagnetism at room temp December 17th, 2014

ORNL microscopy pencils patterns in polymers at the nanoscale December 17th, 2014

Chip Technology

Instant-start computers possible with new breakthrough December 19th, 2014

Switching to spintronics: Berkeley Lab reports on electric field switching of ferromagnetism at room temp December 17th, 2014

Pb islands in a sea of graphene magnetise the material of the future December 16th, 2014

Stanford team combines logic, memory to build a 'high-rise' chip: Today circuit cards are laid out like single-story towns; Futuristic architecture builds layers of logic and memory into skyscraper chips that would be smaller, faster, cheaper -- and taller December 15th, 2014

Discoveries

Atom-thick CCD could capture images: Rice University scientists develop two-dimensional, light-sensitive material December 20th, 2014

Oregon researchers glimpse pathway of sunlight to electricity: Collaboration with Lund University uses modified UO spectroscopy equipment to study 'maze' of connections in photoactive quantum dots December 19th, 2014

Instant-start computers possible with new breakthrough December 19th, 2014

Iranian Scientists Use Nanotechnology to Increase Power, Energy of Supercapacitors December 18th, 2014

Announcements

Atom-thick CCD could capture images: Rice University scientists develop two-dimensional, light-sensitive material December 20th, 2014

Oregon researchers glimpse pathway of sunlight to electricity: Collaboration with Lund University uses modified UO spectroscopy equipment to study 'maze' of connections in photoactive quantum dots December 19th, 2014

Instant-start computers possible with new breakthrough December 19th, 2014

Aculon Hires New Business Development Director December 19th, 2014

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More










ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







© Copyright 1999-2014 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE