Researchers get around bad gap problem with graphene by using negative differential resistance

Aug 22, 2013 by Bob Yirka report
Experimentally observed negative differential resistance characteristics in graphene devices. (a) SEM of top-view SEM of a typical dual-gate graphene device. Gold color is the source/drain, pink color is the top gate and the blue color underneath is graphene flake. The gate and graphene channel is separated by a two-layer of AlOx and HfO2 oxide stack. The scale bar is 1μm. (b) The transfer characteristics of BLG device under different back-gate voltage. The increased resistance at large back-gate voltage indicated band gap opening by perpendicular electric field. The inset shows the Dirac point shift as the back-gate voltage changes. Credit: arXiv:1308.2931 [cond-mat.mes-hall]

(Phys.org) —A team of researchers at the University of California has come up with a way to use graphene in a transistor without sacrificing speed. In a paper they've uploaded to the preprint server arXiv, the team describes how they took advantage of a property of graphene known as negative differential resistance to coax transistor-like properties out of graphene without causing it to behave as a semiconductor.

As most everyone knows, using silicon as the basis for building transistors is reaching its logical conclusion—basic physics dictates that transistors based on it can only be made so small. Thus, efforts have been underway for several years to find a replacement material. One of the leading candidates, of course, is graphene—it has a variety of properties that would make it ideal, the best of which is the incredible speed in which electrons can move through it. Unfortunately, graphene is not a —it has no bad gap. That makes it useless as material for use in a transistor, which by its very nature must have a component that turns on and off. Graphene stays on all the time.

Researchers have spent a lot of time, money and effort trying to force graphene to behave like a , but most efforts have either failed completely, or resulted in a slowdown of the movement of electrons—defeating the whole point of using grahene in the first now. Now, however, it appears the team at UC has found a way to use graphene in a transistor, without forcing it to have a .

The researchers took advantage of a property of graphene known as negative differential —this occurs when a charge is applied under certain conditions to a material and the overall voltage level of the circuit is reduced. Thus, instead of changing the way graphene behaves, the team found a way to use another of its properties. They used the drop in voltage as a logic gate, which of course is one of the basic components of a transistor.

The team hasn't built an actual transistor yet, but express optimism that it can be done. If they succeed, it could mean the creation of that operate in the 400GHz range—orders of magnitude faster than today's based technology, though they wouldn't appear in consumer products for at least ten years due to the need to completely change production processes.

Explore further: Scientists unveil new technology to better understand small clusters of atoms

More information: Graphene-Based Non-Boolean Logic Circuits, arXiv:1308.2931 [cond-mat.mes-hall] arxiv.org/abs/1308.2931

Abstract
Graphene revealed a number of unique properties beneficial for electronics. However, graphene does not have an energy band-gap, which presents a serious hurdle for its applications in digital logic gates. The efforts to induce a band-gap in graphene via quantum confinement or surface functionalization have not resulted in a breakthrough. Here we show that the negative differential resistance experimentally observed in graphene field-effect transistors of "conventional" design allows for construction of viable non-Boolean computational architectures with the gap-less graphene. The negative differential resistance - observed under certain biasing schemes - is an intrinsic property of graphene resulting from its symmetric band structure. Our atomistic modeling shows that the negative differential resistance appears not only in the drift-diffusion regime but also in the ballistic regime at the nanometer-scale - although the physics changes. The obtained results present a conceptual change in graphene research and indicate an alternative route for graphene's applications in information processing.

via Arxiv blog

Related Stories

Researchers devise a way to a create graphene transistor

Jul 18, 2012

(Phys.org) -- Researchers in Germany appear to have found a way to create a monolithic (integrated) graphene transistor, using a lithographic process applied to silicon carbide, a breakthrough that could lead ...

Graphene's high-speed seesaw

Apr 30, 2013

A new transistor capable of revolutionizing technologies for medical imaging and security screening has been developed by graphene researchers from the Universities of Manchester and Nottingham.

IBM introduces new graphene transistor

Apr 11, 2011

(PhysOrg.com) -- In a report published in Nature, Yu-ming Lin and Phaedon Avoris, IBM researchers, have announced the development of a new graphene transistor which is smaller and faster than the one they i ...

Two graphene layers may be better than one

Apr 27, 2011

(PhysOrg.com) -- Researchers at the National Institute of Standards and Technology have shown that the electronic properties of two layers of graphene vary on the nanometer scale. The surprising new results ...

Recommended for you

Relaxing DNA strands by using nano-channels

20 hours ago

A simple and effective way of unravelling the often tangled mass of DNA is to 'thread' the strand into a nano-channel. A study carried out with the participation of the International School for Advanced Studies ...

Сalculations with nanoscale smart particles

Aug 19, 2014

Researchers from the Institute of General Physics of the Russian Academy of Sciences, the Institute of Bioorganic Chemistry of the Russian Academy of Sciences and MIPT have made an important step towards ...

Nanostructure enlightening dendrite-free metal anode

Aug 19, 2014

Graphite anodes have been widely used for lithium ion batteries (LIBs) during the past two decades. The replacement of metallic lithium with graphite enables safe and highly efficient operation of LIBs, however, ...

Bacterial nanowires: Not what we thought they were

Aug 18, 2014

For the past 10 years, scientists have been fascinated by a type of "electric bacteria" that shoots out long tendrils like electric wires, using them to power themselves and transfer electricity to a variety ...

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

EyeNStein
1 / 5 (8) Aug 22, 2013
A useful result: Using an applied electric field (using 60 volts!) to open the band gap. Even better that they have created a bi-stable element for a logic gate.
However the journalism of this article leaves much to be desired:
"logic gate, which of course is one of the basic components of a transistor." this statement is of course totally backwards.
jalmy
1.9 / 5 (9) Aug 22, 2013
The title is wrong, should be "band gap" not bad gap.
beleg
1 / 5 (1) Aug 23, 2013
Hmm. No. Ask Bob. No typo there where you see one.