Navigation Links
Penn scientists demonstrate potential of graphene films as next-generation transistors
Date:7/31/2008

PHILADELPHIA - 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.

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 Nano Letters 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.


'/>"/>

Contact: Jordan Reese
jreese@upenn.edu
215-573-6604
University of Pennsylvania
Source:Eurekalert

Related biology technology :

1. Scientists demonstrate highly directional semiconductor lasers
2. Conference to Turn Scientists of Color into PA-Based Entrepreneurs Set for November
3. Project Mind Survey of Israeli Ph.D. Scientists Favors a New Standard of Creativity in Science
4. Virtual world is sign of future for scientists, engineers
5. Scientists fix bugs in our understanding of evolution
6. Ten Latin American Scientists Named 2008 Pew Fellows in the Biomedical Sciences
7. Israeli Scientists Recipients of 2008 International Adult Stem Cell Award
8. Weizmann Institute scientists create new nanotube structures
9. Abbott Scientists Present a New Approach for Treating Attention-Deficit Hyperactivity Disorder
10. Leading Overseas Scientists Establish High-Tech Bio-Pharmaceutical Enterprise in Changzhou
11. Scientists call for more access to biotech crop data
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:11/30/2016)... Nov. 30, 2016  GenomOncology today announced the appointment of ... Medical Affairs.  Dr. Coleman will oversee clinical ... proprietary knowledge-enabled platform. The GenomOncology software suite empowers molecular pathologists ... data and clinical decision support, from quality control through reporting. ... , , ...
(Date:11/30/2016)... VANCOUVER , Nov. 30, 2016 /PRNewswire/ -  Equicare ... coordination solutions, has been recognized as one of the ... 100, an annual international listing that distinguishes the top ... "We,ve pushed a great step forward this year continually ... growing our own customer base and team," says ...
(Date:11/30/2016)... 30, 2016   Merck , a leading science ... into a set of agreements with Evotec AG, whereby ... of genetic reagents such as CRISPR and shRNA libraries. ... offers an accelerated pathway to explore and identify new ... identification of new targets, a process that can be ...
(Date:11/30/2016)... ... 2016 , ... With growth rates averaging more than 30% each year, Random42 ... to continuing their expansion in their new office space. The new office has a ... by the creative industries, so Random42 Scientific Communication will fit right in. , ...
Breaking Biology Technology:
(Date:6/15/2016)... 15, 2016 Transparency Market ... Recognition Market by Application Market - Global Industry Analysis Size ... to the report, the  global gesture recognition market ... and is estimated to grow at a CAGR ... 2024.  Increasing application of gesture recognition ...
(Date:6/7/2016)... 7, 2016  Syngrafii Inc. and San Antonio ... that includes integrating Syngrafii,s patented LongPen™ eSignature "Wet" ... collaboration will result in greater convenience for SACU ... while maintaining existing document workflow and compliance requirements. ... Highlights: ...
(Date:6/2/2016)... 2, 2016   The Weather Company , an IBM ... an industry-first capability in which consumers will be able to ... ask questions via voice or text and receive relevant information ... Marketers have long sought an advertising solution that ... be personal, relevant and valuable; and can scale across millions ...
Breaking Biology News(10 mins):