Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New results force scientists to rethink single-molecule wires

30.05.2003


Single-molecule switches have the potential to shrink computing circuits dramatically, but new results from the Arizona State University lab that first described how to wire a single molecule between gold contacts now show that laboratory-standard wired molecules have an unavoidable tendency to "blink" randomly.



In the May 30, 2003, Science, Stuart Lindsay and colleagues identify the cause of this blinking behavior as random, temporary breaks in the chemical bond between the wired molecule and the gold contacts, making this particular wired-molecule arrangement unsuitable for electronic circuits. The National Science Foundation, the federal government agency responsible for supporting all areas of science and engineering, supported the research.

"There is a substantial interest in building single-molecule switches for molecular computing," said Lindsay, a professor of biophysics. "The observation from scanning tunneling microscopes is that these wired molecules ’blink’ on and off. It was assumed that this was due to some property of the molecules, and if that behavior could be controlled, they could be used as molecular switches." The various molecules examined typically blink once every 30 seconds to four minutes.


The research team includes Arizona State postdoctoral researchers Ganesh Ramachandran and Alex Primak, and researchers Theresa Hopson, Adam Rawlett and Larry Nagahara from Motorola Labs’ Physical Sciences Research Laboratories.

In 2001, Lindsay’s research group was the first to perfect a technique that allowed long, thin molecules capped at both ends with sulfur atoms to be wired individually to a gold electrode. Since then, researchers have studied the behavior and properties of various exotic molecules, almost all wired via sulfur atoms to gold electrodes using the Lindsay group’s procedure.

To isolate the cause of the blinking, Lindsay’s team compared the wired behavior of a more complex molecule to that of extremely simple molecules. While various explanations for the blinking had been proposed for complex molecules, none could possibly apply to the simpler molecules. Yet Lindsay’s team saw the blinking in all cases.

"We were left with two possibilities," Lindsay said. "Either the molecule itself or the contact was switching. The conclusion we had to reach was that the lower contact was coming apart."

However, that conclusion runs contrary to some basic chemistry: sulfur-gold bonds simply do not break at room temperature or even at temperatures as high as 60 degrees Celsius (140 degrees Fahrenheit).

Lindsay’s team explains the apparent contradiction with some equally basic chemistry. While the sulfur-gold bonds don’t break permanently, the bonds are unstable and will break temporarily and then re-connect. In fact, a chemical process called "annealing"--commonly used to harden metals and also in the procedure to prepare the gold electrodes to accept wired molecules--relies on the unstable bonds coming apart. The team reports that, as expected, the blinking becomes more frequent when the wired molecules are heated to annealing temperatures.

The blinking, in other words, is not a controllable behavior of the molecules. The on-and-off blinking happens naturally and randomly at the sulfur contact between the molecule and the gold electrodes.

"This doesn’t help anyone build better computing devices, but neither does it mean that single-molecule wires are useless," Lindsay said. "It’s just not as naïve as it first seemed. The gold surface is not the best electrode material, but there are other options."

David Hard | EurekAlert!
Further information:
http://www.nsf.gov/
http://green.la.asu.edu/.

More articles from Physics and Astronomy:

nachricht Basque researchers turn light upside down
23.02.2018 | Elhuyar Fundazioa

nachricht Attoseconds break into atomic interior
23.02.2018 | Max-Planck-Institut für Quantenoptik

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Attoseconds break into atomic interior

A newly developed laser technology has enabled physicists in the Laboratory for Attosecond Physics (jointly run by LMU Munich and the Max Planck Institute of Quantum Optics) to generate attosecond bursts of high-energy photons of unprecedented intensity. This has made it possible to observe the interaction of multiple photons in a single such pulse with electrons in the inner orbital shell of an atom.

In order to observe the ultrafast electron motion in the inner shells of atoms with short light pulses, the pulses must not only be ultrashort, but very...

Im Focus: Good vibrations feel the force

A group of researchers led by Andrea Cavalleri at the Max Planck Institute for Structure and Dynamics of Matter (MPSD) in Hamburg has demonstrated a new method enabling precise measurements of the interatomic forces that hold crystalline solids together. The paper Probing the Interatomic Potential of Solids by Strong-Field Nonlinear Phononics, published online in Nature, explains how a terahertz-frequency laser pulse can drive very large deformations of the crystal.

By measuring the highly unusual atomic trajectories under extreme electromagnetic transients, the MPSD group could reconstruct how rigid the atomic bonds are...

Im Focus: Developing reliable quantum computers

International research team makes important step on the path to solving certification problems

Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Basque researchers turn light upside down

23.02.2018 | Physics and Astronomy

Finnish research group discovers a new immune system regulator

23.02.2018 | Health and Medicine

Attoseconds break into atomic interior

23.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>