Navigation Links
S-t-r-e-t-c-h-i-n-g electrical conductance to the limit
Date:12/5/2011

Individual molecules have been used to create electrical components like resistors, transistors and diodes, that mimic the properties of familiar semiconductors. But according to Nongjian (NJ) Tao, a researcher at the Biodesign Institute at Arizona State University, unique properties inherent in single molecules may also allow clever designers to produce novel devices whose behavior falls outside the performance observed in conventional electronics.

In research appearing in today's issue of Nature Nanotechnology, Tao describes a method for mechanically controlling the geometry of a single molecule, situated in a junction between a pair of gold electrodes that form a simple circuit. The manipulations produced over tenfold increase in conductivity.

The unusual, often non-intuitive characteristics of single molecules may eventually be introduced into a broad range of microelectronics, suitable for applications including biological and chemical sensing; electronic and mechanical devices.

Delicate molecular manipulations requiring patience and finesse are routine for Tao, whose research at Biodesign's Center for Bioelectronics and Biosensors has included work on molecular diodes, graphene behavior and molecular imaging techniques. Nevertheless, he was surprised at the outcome described in the current paper: "If you have a molecule attached to electrodes, it can stretch like a rubber band," he says. "If it gets longer, most people tend to think that the conductivity will decrease. A longer wire is less conductive than a shorter wire."

Indeed, diminishing conductivity through a molecule is commonly observed when the distance between the electrodes attached to its surface is increased and the molecule becomes elongated. But according to Tao, if you stretch the molecule enough, something unexpected happens: the conductance goes upby a huge amount. "We see at least 10 times greater conductivity, simply by pulling the molecule."

As Tao explains, the intriguing result is a byproduct of the laws of quantum mechanics, which dictate the behavior of matter at the tiniest scales: "The conductivity of a single molecule is not simply inversely proportional to length. It depends on the energy level alignment."

In the metal leads of the electrodes, electrons can move about freely but when they come to an interfacein this case, a molecule that sits in the junction between electrodesthey have to overcome an energy barrier. The height of this energy barrier is critical to how readily electrons can pass through the molecule. By applying a mechanical force to the molecule, the barrier is lowered, improving conductance.

"Theoretically, people have thought of this as a possibility, but this is a demonstration that it really happens," Tao says. "If you stretch the molecule and geometrically increase the length, it energetically lowers the barrier so electrons can easily go through. If you think in optical terms, it becomes more transparent to electrons."

The reason for this has to do with a property known as force-induced resonant tunneling. This occurs when the molecular energy moves closer to the Fermi level of the electrodesthat is, toward the region of optimal conductance. (See figure 1) Thus, as the molecule is stretched, it causes a decrease in the tunneling energy barrier.

For the experiments, Tao's group used 1,4'-Benzenedithiol, the most widely studied entity for molecular electronics. Further experiments demonstrated that the transport of electrons through the molecule underwent a corresponding decrease as the distance between the electrodes was reduced, causing the molecule's geometry to shift from a stretched condition to a relaxed or squeezed state. "We have to do this thousands of times to be sure the effect is robust and reproducible."

In addition to the discovery's practical importance, the new data show close agreement with theoretical models of molecular conductance, which had often been at variance with experimental values, by orders of magnitude.

Tao stresses that single molecules are compelling candidates for a new types of electronic devices, precisely because they can exhibit very different properties from those observed in conventional semiconductors.

Microelectromechanical systems or MEMS are just one domain where the versatile properties of single molecules are likely to make their mark. These diminutive creations represent a $40 billion a year industry and include such innovations as optical switches, gyroscopes for cars, lab-on-chip biomedical applications and microelectronics for mobile devices.

"In the future, when people design devices using molecules, they will have a new toolbox they can use."


'/>"/>
Contact: Joseph Caspermeyer
Joseph.Caspermeyer@asu.edu
Arizona State University
Source:Eurekalert  

Related biology technology :

1. New carbon material shows promise of storing large quantities of renewable electrical energy
2. Paperwork: Buckypapers clarify electrical, optical behavior of nanotubes
3. Gold solution for enhancing nanocrystal electrical conductance
4. Integrated Electrical Services Awarded Contract to Provide Electrical Systems for U.S. Army Medical Research Institute of Infectious Diseases
5. Penn material scientists turn light into electrical current using a golden nanoscale system
6. Measuring the electrical properties of nano-crystals
7. New research shows how light can control electrical properties of graphene
8. 3-D printing method advances electrically small antenna design
9. Enhanced electrical energy storage may result from professors research
10. Piezoelectric nanowires allow electrical signals to be produced from mechanical actions
11. How graphenes electrical properties can be tuned
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
S-t-r-e-t-c-h-i-n-g  electrical conductance to the limit
(Date:12/8/2016)... , ... December 08, 2016 , ... ... in the World Technology Awards. uBiome is one of just six company finalists ... categories. , In addition to uBiome, companies nominated as finalists in this year’s ...
(Date:12/8/2016)... 8, 2016  Soligenix, Inc. (OTCQB: SNGX) (Soligenix ... on developing and commercializing products to treat rare ... announced today the long-term follow-up data from its ... first-in-class Innate Defense Regulator (IDR), in the treatment ... cancer patients undergoing chemoradiation therapy (CRT).  The additional ...
(Date:12/8/2016)...  HedgePath Pharmaceuticals, Inc. (OTCQX: HPPI), a clinical ... to commercialize innovative therapeutics for patients with cancer, ... approved for trading on the OTCQX U.S. market. ... effective today, under the ticker symbol "HPPI." ... must meet high financial standards, follow best practice ...
(Date:12/8/2016)... Korea , Dec. 8, 2016 Eutilex ... $21 billion KRW (US $18.9M) Series A financing. This ... Investment, G.N. Tech Venture and SNU Bio Angel. This ... to 30.5 billion KRW (US $27.7M) since its founding ... Eutilex to bolster the development and commercialization of its ...
Breaking Biology Technology:
(Date:6/22/2016)... American College of Medical Genetics and Genomics was once again ... of the fastest-growing trade shows during the Fastest 50 Awards ... Las Vegas . Winners are ... of the following categories: net square feet of paid exhibit ... 2015 ACMG Annual Meeting was ranked 23 out of 50 ...
(Date:6/21/2016)... , June 21, 2016 NuData ... the new role of principal product architect and ... the director of customer development. Both will report ... technical officer. The moves reflect NuData,s strategic growth ... response to high customer demand and customer focus ...
(Date:6/15/2016)... 2016 Transparency Market Research ... Market by Application Market - Global Industry Analysis Size Share ... the report, the  global gesture recognition market  was ... is estimated to grow at a CAGR of ... Increasing application of gesture recognition technology ...
Breaking Biology News(10 mins):