Molecule movement could make memory

By Eric Smalley, Technology Research News

Researchers have made tiny transistors by attaching gold electrodes to individual buckyballs, which are soccer ball-shaped carbon molecules.

These single-molecule transistors could be used as memory elements, clocks for electronic circuits or tuners for communications devices like cell phones.

The device allows for a single file flow of electrons from the electrode to the buckyball. As each electron hops onto the buckyball, the molecule moves.

"When single electrons move through these devices they can lead to movement of the structure -- to distortions or in this case a bouncing motion," said Paul L. McEuen, professor of physics at University of California at Berkeley and a principal investigator at Lawrence Berkeley National Laboratories.

Electron transfer is used to move micron-scale parts of microelectromechanical systems (MEMS), said McEuen. The effect "probably will be even more prevalent whether you like it or not at the nanoscale. Invariably these things are going to move," he said.

Despite its name, a buckyball transistor would not be useful as a nanoscale transistor for controlling the flow electrons in circuits, McEuen said. "Its resistance is very high [and] it doesn't have any gain," he said.

However, buckyball transistors could be useful as oscillators to provide clock, or synchronizing functions, for electronic circuits, and as tuners for high frequency radio devices like cell phones, McEuen said

"They're very high-quality oscillators in the sense that they oscillate at a very well-defined frequency and they don't lose much energy per oscillation," he said.

It might also be possible to make a version of the transistor where the molecule moves from one place to another rather than oscillating back and forth, McEuen said. A buckyball transistor with that kind of motion would be an electromechanical switch that could serve as a memory unit for storing a single bit. In theory, such a memory element would be relatively stable, he said.

"We use electrons to store information now, but electrons are flitty little things that always want to... run away. But something like a molecule… has a hard time moving around," McEuen said.

It will likely be 10 to 20 years before molecular electronic devices like the buckyball transistor can be used as components in computers or other systems, McEuen said.

McEuen's work was published in the September 7, 2000 issue of the journal Nature. McEuen's co-authors were Hongkun Park, Jiwoong Park, Andrew K. L. Lim, Erik H. Anderson and A. Paul Alivisatos of UC Berkeley and/or Lawrence Berkeley National Laboratory. The research was funded by the Department of Energy.

Timeline:   10-20 years
Funding:   Government
TRN Categories:   Semiconductors and Materials; Nanotechnology
Story Type:   News
Related Elements:   Technical paper "Nanomechanical oscillations in a single-C60 transistor" in September 7, 2000 Nature


October 18, 2000

Page One

Nanotubes gain larger kin

Quantum computing without weirdness

Pyramid pixels promise sharp pictures

Molecule movement could make memory

Researchers make cheap telecom laser


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