Nanotechnology Now

Our NanoNews Digest Sponsors



Heifer International

Wikipedia Affiliate Button


android tablet pc

Home > Press > Small ... smaller ... smallest? ASU researchers create molecular diode

This is a schematic for molecular diode. The symmetric molecule (top) allows for two-way current. The asymmetrical molecule (bottom) permits current in one direction only and acts as a single-molecule diode.

Credit: Biodesign Institute at Arizona State University
This is a schematic for molecular diode. The symmetric molecule (top) allows for two-way current. The asymmetrical molecule (bottom) permits current in one direction only and acts as a single-molecule diode.

Credit: Biodesign Institute at Arizona State University

Abstract:
Recently, at Arizona State University's Biodesign Institute, N.J. Tao and collaborators have found a way to make a key electrical component on a phenomenally tiny scale. Their single-molecule diode is described in this week's online edition of Nature Chemistry.

Small ... smaller ... smallest? ASU researchers create molecular diode

Tempe, AZ | Posted on October 13th, 2009

In the electronics world, diodes are a versatile and ubiquitous component. Appearing in many shapes and sizes, they are used in an endless array of devices and are essential ingredients for the semiconductor industry. Making components including diodes smaller, cheaper, faster and more efficient has been the holy grail of an exploding electronics field, now probing the nanoscale realm.

Smaller size means cheaper cost and better performance for electronic devices. The first generation computer CPU used a few thousand transistors, Tao says noting the steep advance of silicon technology. "Now even simple, cheap computers use millions of transistors on a single chip."

But lately, the task of miniaturization has gotten much harder, and the famous dictum known as Moore's law—which states that the number of silicon-based transistors on a chip doubles every 18-24 months—will eventually reach its physical limits. "Transistor size is reaching a few tens of nanometers, only about 20 times larger than a molecule," Tao says. "That's one of the reasons people are excited about this idea of molecular electronics."

Diodes are critical components for a broad array of applications, from power conversion equipment, to radios, logic gates, photodetectors and light-emitting devices. In each case, diodes are components that allow current to flow in one direction around an electrical circuit but not the other. For a molecule to perform this feat, Tao explains, it must be physically asymmetric, with one end capable of forming a covalent bond with the negatively charged anode and the other with the positive cathode terminal.

The new study compares a symmetric molecule with an asymmetric one, detailing the performance of each in terms of electron transport. "If you have a symmetric molecule, the current goes both ways, much like an ordinary resistor," Tao observes. This is potentially useful, but the diode is a more important (and difficult) component to replicate (Fig 1).

The idea of surpassing silicon limits with a molecule-based electronic component has been around awhile. "Theoretical chemists Mark Ratner and Ari Aviram proposed the use of molecules for electronics like diodes back in 1974," Tao says, adding "people around world have been trying to accomplish this for over 30 years."

Most efforts to date have involved many molecules, Tao notes, referring to molecular thin films. Only very recently have serious attempts been made to surmount the obstacles to single-molecule designs. One of the challenges is to bridge a single molecule to at least two electrodes supplying current to it. Another challenge involves the proper orientation of the molecule in the device. "We are now able to do this—to build a single molecule device with a well defined orientation," Tao says.

The technique developed by Tao's group relies on a property known as AC modulation. "Basically, we apply a little periodically varying mechanical perturbation to the molecule. If there's a molecule bridged across two electrodes, it responds in one way. If there's no molecule, we can tell."

The interdisciplinary project involved Professor Luping Yu, at the University of Chicago, who supplied the molecules for study, as well as theoretical collaborator, Professor Ivan Oleynik from the University of South Florida. The team used conjugated molecules, in which atoms are stuck together with alternating single and multiple bonds. Such molecules display large electrical conductivity and have asymmetrical ends capable of spontaneously forming covalent bonds with metal electrodes to create a closed circuit.

The project's results raise the prospect of building single molecule diodes - the smallest devices one can ever build. "I think it's exciting because we are able to look at a single molecule and play with it, " Tao says. "We can apply a voltage, a mechanical force, or optical field, measure current and see the response. As quantum physics controls the behaviors of single molecules, this capability allows us to study properties distinct from those of conventional devices."

Chemists, physicists, materials researchers, computational experts and engineers all play a central role in the emerging field of nanoelectronics, where a zoo of available molecules with different functions provide the raw material for innovation. Tao is also examining the mechanical properties of molecules, for example, their ability to oscillate. Binding properties between molecules make them attractive candidates for a new generation of chemical sensors. "Personally, I am interested in molecular electronics not because of their potential to duplicate today's silicon applications, " Tao says. Instead, molecular electronics will benefit from unique electronic, mechanical, optical and molecular binding properties that set them apart from conventional semiconductors. This may lead to applications complementing rather than replacing silicon devices.

####

For more information, please click here

Contacts:
Joe Caspermeyer

480-727-0369

Written by Richard Harth
Biodesign Institute Science Writer

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

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

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

Molecular Machines

Creation of 'Rocker' protein opens way for new smart molecules in medicine, other fields December 18th, 2014

Dartmouth researchers create 'green' process to reduce molecular switching waste December 15th, 2014

'Nanomotor lithography' answers call for affordable, simpler device manufacturing October 31st, 2014

Crystallizing the DNA nanotechnology dream: Scientists have designed the first large DNA crystals with precisely prescribed depths and complex 3D features, which could create revolutionary nanodevices October 20th, 2014

Molecular Nanotechnology

Dartmouth researchers create 'green' process to reduce molecular switching waste December 15th, 2014

New technique allows low-cost creation of 3-D nanostructures December 8th, 2014

Researchers discern the shapes of high-order Brownian motions November 17th, 2014

Manipulating complex molecules by hand: New method in scanning probe microscopy: Jülich researchers create a word using 47 molecules November 6th, 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

Discoveries

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

Creation of 'Rocker' protein opens way for new smart molecules in medicine, other fields December 18th, 2014

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

Announcements

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

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