In the pursuit of ever-shrinking circuitry for nanotechnology electronics, increasingly smaller devices and components are being developed. Now researchers at the University of Konstanz and the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) in Germany claim to have micro-miniaturized the humble electrical switch all the way down to molecule size and proven its operation for the very first time. Unable to flick such a tiny switch mechanically, however, the researchers instead used light to turn it on.
The new three nanometer-wide device is created from a diarylethene compound – a photochromic molecule that reacts chemically when exposed to light. Ring-shaped, a part of the diarylethene molecule ring is open when shielded from light, and then reconnects to the other half on exposure to light. With exceptionally tiny gold nanowires embedded into its structure, this connection then allows an electrical current to flow.
A physicist at the HZDR, Dr Artur Erbe, believes that new components created at a molecular scale will provide opportunities for much smaller and more efficient electronic devices.
“Single molecules are currently the smallest imaginable components capable of being integrated into a processor,” says Dr Erbe.
The researchers claim that the breakthrough capability of being able to switch a molecule on to conduct electrical current has never been fully proven before. This, they say, is because it requires a molecule that ordinarily possesses a strong bond between individual atoms, but is able to dissolve that connection and reform it as required when external energy is applied. Suspended in a fluid in a test tube for the experiments, the molecules were exposed to a beam of UV light to switch them from their open to closed states.
“For the first time ever we could switch on a single contacted molecule and prove that this precise molecule becomes a conductor on which we have used the light beam,” says Dr Erbe. “We have also characterized the molecular switching mechanism in extremely high detail, which is why I believe that we have succeeded in making an important step toward a genuine molecular electronic component.”
As yet, however, switching off the molecules by reversing the connection has become a bit more problematic, but the researchers believe that it is only a matter of time before this is achieved.
“Our colleagues from the HZDR theory group are computing how precisely the molecule must rotate so that the current is interrupted,” says Dr Erbe. “Together with the chemists from Konstanz, we will be able to accordingly implement the design and synthesis for the molecule.”
Given that the electron-beam lithography work on the diarylethene molecule contact and the succeeding measurements alone took three years, however, it may be some time before a fully-functioning, on/off switch is realized.
If the researchers do succeed in producing such a fully-functioning molecular device, it may well lead the way toward other microscopically small electronic components and a future electronics industry born from self-assembling molecules or, at least complement similar nanotechnology devices such as nanobots and nanoelectronics.
“DNA molecules are, for instance, able to arrange themselves into structures without any outside assistance,” says Dr Erbe. “If we succeed in constructing logical switches from self-organizing molecules, then computers of the future will come from test-tubes.”
The results of this research were recently published in the journal Advanced Science.