Nanotechnology Now

Our NanoNews Digest Sponsors



Heifer International

Wikipedia Affiliate Button


android tablet pc

Home > Press > Stretching electrical conductance to the limit

Nongjan (NJ) Tao, director of the Center for Bioelectronics and Biosensors, Biodesign Institute.
Photo by: The Biodesign Institute at Arizona State University
Nongjan (NJ) Tao, director of the Center for Bioelectronics and Biosensors, Biodesign Institute.

Photo by: The Biodesign Institute at Arizona State University

Abstract:
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 ASU, unique properties inherent in single molecules also may allow clever designers to produce novel devices whose behavior falls outside the performance observed in conventional electronics.

Stretching electrical conductance to the limit

Tempe, AZ | Posted on December 6th, 2011

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 up - by 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 interface - in this case, a molecule that sits in the junction between electrodes - they 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 electrodes - that 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."

In addition to Tao's position as director of Biodesign's Center for Bioelectronics and Biosensors, he holds a professorship in the Ira A. Fulton Schools of Engineering, School of Electrical, Computer and Energy Engineering.

####

For more information, please click here

Contacts:
Richard Harth

Copyright © Arizona State University

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

MEMS

MEMS Industry Group's 10th Annual Executive Conference Showcases Rapid Innovation in MEMS/Sensors: Emphasizes Spirit of Collaboration, Supporting First Open-Source Algorithm Community, New Standardization Efforts November 10th, 2014

MEMS & Sensors Technology Showcase: Finalists Announced for MEMS Executive Congress US 2014 October 23rd, 2014

IEEE International Electron Devices Meeting To Celebrate 60th Anniversary as The Leading Technical Conference for Advanced Semiconductor Devices September 18th, 2014

Carbyne morphs when stretched: Rice University calculations show carbon-atom chain would go metal to semiconductor July 21st, 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

Sensors

Promising new method for rapidly screening cancer drugs: UMass Amherst researchers invent fast, accurate new nanoparticle-based sensor system December 15th, 2014

Graphene Applied in Production of Recyclable Electrodes December 13th, 2014

Detecting gases wirelessly and cheaply: New sensor can transmit information on hazardous chemicals or food spoilage to a smartphone December 8th, 2014

Nanosensor to Detect Naproxen Drug Produced in Iran December 6th, 2014

Nanoelectronics

Stacking two-dimensional materials may lower cost of semiconductor devices December 11th, 2014

Defects are perfect in laser-induced graphene: Rice University lab discovers simple way to make material for energy storage, electronics December 10th, 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

'Giant' charge density disturbances discovered in nanomaterials: Juelich researchers amplify Friedel oscillations in thin metallic films November 26th, 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

Nanobiotechnology

Scientists trace nanoparticles from plants to caterpillars: Rice University study examines how nanoparticles behave in food chain December 16th, 2014

FEI and Oregon Health & Science University Install a Complete Correlative Microscopy Workflow in Newly Built Collaborative Science Facility December 16th, 2014

UCLA engineers first to detect and measure individual DNA molecules using smartphone microscope December 15th, 2014

Biomimetic dew harvesters: Understanding how a desert beetle harvests water from dew could improve drinking water collection in dew condensers December 8th, 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