Scientists in Alberta say they have taken a giant leap in the tiny world of molecular electronics, building a transistor out of a single molecule and opening the way for the creation one day of minute computers, thousands of times more powerful than conventional devices.
The breakthrough, details of which will be published Thursday in the scientific journal Nature, promises significantly faster and cheaper microelectronic devices.
Scientists have speculated for two decades that molecules could be used as electrical switches. "Previous indications left much doubt. What we've done is take away that doubt," said Robert Wolkow, principal investigator and a physics professor at the University of Alberta.
Dr. Wolkow and his team of seven researchers at the university and the National Institute for Nanotechnology in Edmonton say they have shown for the first time that an electrical current flowing through a molecule just one-billionth of a metre wide can be switched on and off by changing the charge of a single atom on a silicon surface nearby.
Devices that control electrical current flow are known as transistors. Computers operate with millions of transistors, set onto silicon microchips, that switch current on and off to represent binary digits.
Where today's transistors require about one million electrons to switch a current, Dr. Wolkow and his team say they have managed to switch the current through a molecule using a single electron. That means the flow can be changed much faster and using far less power.
"We have achieved unheard of smallness and unheard of efficiency," Dr. Wolkow said.
A transistor is a three-terminal device, containing an in and out and a control outlet, similar to the common garden hose. Getting those elements to work together at the molecular level has challenged scientists for years. Dr. Wolkow makes the analogy of wedging a poppy seed between two watermelons and then trying to get a third melon to touch the seed at the same time. "You just can't get three things to converge on this tiny scale."
His solution was to put the molecule on a silicon surface that contains special atoms, each with an extra electron, to create an electric field very close to the molecule.
The work is still considered contentious.
Other scientists specializing in nanotechnology challenge the authenticity of the model that doesn't use a traditional three-terminal transistor, Dr. Wolkow said. "What we've done is build a highly impractical prototypical device. But there's no fundamental reason why you couldn't build a computer chip with this kind of transistor."
It will be decades, however, before the first molecular computer is built, he said.
