Canadian nanotechology team designs tiny switch to greatly increase speeds of computers

The spectacular advance, reported in Nature magazine, also offers the prospect of computerized sensors navigating bloodstreams to diagnose health problems and anti-terrorism devices capable of detecting as little as a single molecule of a toxic substance.

Avik Ghosh, a computing expert, predicted such sensor applications would hit the marketplace within a decade, while demand for molecular computers would take longer to develop.

"This is a tour de force in terms of chemistry," said Ghosh, a computing researcher at Indiana's Purdue University.

A research team from the National Institute for Nanotechnology and the University of Alberta in Edmonton used a single molecule of styrene, the stuff in disposable cups, to drastically shrink the on-off transistor switch — the basic building block of computer processors.

The styrene molecule replaced the much larger conducting paths currently etched into silicon wafers.

Lead nanotechnologist Robert Wolkow said the process initially would allow switches to be "100 to 1,000 times smaller.

"So that means the switches can be placed much closer together and will work a lot faster because the current doesn't have as far to travel. At least 100 times faster to start with," said Wolkow.

The prototype "nanoswitch" is less than one nanometre thick, meaning that 10,000 would fit in the width of a human hair.

The styrene molecule "switch" is like a drawbridge, carrying electrical current between an atom in a silicon wafer and a microscopic metal tip. The current flow is switched off and on by an electrical field radiating from another silicon atom next door to the first.

Gosh said the Edmonton nanoswitch is closer to practical application than previous experiments. "It works at room temperature. It's built on a silicon foundation, rather than metal, and they control the current flowing through the molecular switch just like in a conventional transistor."

The breakthrough is a major feat for the new $120-million nanotechnology institute, which got going only three years ago and won't move into its custom-built labs until the end of this year. It is run jointly by the National Research Council, a federal agency, and the University of Alberta, which beat out the University of Toronto to be the institute's home.

Many experts predict that advances like the institute's nanoswitch could lead within two decades to supercomputing power so inexpensive that it will be incorporated into every man-made device, plus spawn a whole new world of electronic gizmos.

Nanotechnology and nanoscience take their names from the nanometre — the size you get by slicing one metre into a billion equal parts. Three nanometres span a single water molecule.

Wolkow and others caution that many engineering problems lie ahead.

"We've successfully tackled half the problem but we still have to come up with ways of making an integrated circuit, connecting the switches into useful devices," Wolkow said.

The Edmonton team is pursuing the Holy Grail of molecular electronics, a process called self-assembly. Molecules with selected physical characteristics would be tweaked so they lined themselves up as the switches and other components of an integrated circuit.

Right now that task is done with the incredibly minute tip of a complex piece of lab equipment called a scanning tunnelling microscope.

"It's like trying to pick up a poppy seed with your elbows," said Wolkow.

Molecular electronics is intensely competitive. It has been plagued by controversy and dominated by U.S. industrial giants like Bell Labs and Hewlett-Packard and universities such as Harvard and Cornell.

Four years ago, Bell researcher J. Hendrik Schoen vaulted into headlines with a claim that he had made transistors with single molecules acting as switches. Bell fired Schoen after an investigation found he had fabricated and manipulated his results.

In an email from a meeting in Beijing, McGill University physicist Hong Guo, who specializes in molecular electronics, called the Edmonton research "very important."

Purdue's Gosh said the Canadian research was much more soundly based than earlier experiments because the institute team was able to say exactly where everything was located and what was happening.

Other claims have been made but Wolkow feels the Canadian team has created the first robust molecular switch. Thanks to the scanning tunnelling microscope, "We know all the fiddly little details. We know where all the molecules are bonded at an atomic level and we can calculate the operation of this proto-device. It's not just a guess."