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Atom-tall silicon wires pave way for quantum computers


January 9, 2012

Researchers have created silicon wire four atoms wide and one atom tall capable of carryin...

Researchers have created silicon wire four atoms wide and one atom tall capable of carrying equivalent current to copper wires 20 times as thick (Image: University of New South Wales)

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The world's narrowest silicon wires with a cross section of a mere four atoms by one atom have been created by a team of developers from the University of New South Wales, the University of Melbourne and Purdue University. The wires are fully functioning, with current-carrying capacity equivalent to that of a microprocessor's copper cable, despite being 20 times thinner - and 10,000 times narrower than a human hair.

The team adopted a very different approach to circuit construction in order to develop wires at this scale. "Typically we chip or etch material away, which can be very expensive, difficult and inaccurate," said Gerhard Klimech, a professor of electrical and computer engineering at Purdue University. "But this experimental group built devices by placing atomically thin layers of phosphorus in silicon and found that with densely doped phosphorus wires just four atoms wide it acts like a wire that conducts just as well as metal."

The traditional technique of stripping back metal wires hits a limit once you get down to a width of 20 atoms, Klimech explained. The team's breakthrough came building circuits of phosphorous atoms in silicon crystal an atom at a time. It's an approach that would have been impossible without a technique known as "scanning tunneling microscopy," which allowed the team to both view and manipulate individual atoms.

Silicon wires created by the team are 10,000 times narrower than a human hair (Image: Univ...

As well as real-world experiments, supercomputer simulations were run to establish the current-carrying properties of atomic-scale cables. The team discovered that the resistivity of the wires is not dependent on wire width, and that Ohm's Law (which describes the relationship between current, potential difference and resistance in a conductor) still holds.

"It is extraordinary to show that such a basic law still holds even when constructing a wire from the fundamental building blocks of nature - atoms," said PhD student Bent Weber of the University of New South Wales, and lead author of the study.

The team hopes that their discovery will pave the way for practical silicon-based quantum computing using single-atom transistors, a goal to which atomic-scale wiring has previously been a barrier.

The paper by researchers at the University of New South Wales, the University of Melbourne and Purdue University was published in Science on Friday.

About the Author
James Holloway James lives in East London where he punctuates endless tea drinking with freelance writing and meteorological angst. Unlocking Every Extend Extra Extreme’s “Master of Extreme” achievement was the fourth proudest moment of his life.   All articles by James Holloway
1 Comment

Very confused presentation. The wire is made of heavily doped phosphorus on a silicon crystal matrix? Can't be true if it is only 1 atom wide or high, no room for dopant atom. Usually P is the dopant in Si semiconductors. Would this work on a Saphire or Diamond matrix. Is the much higher conductivity related to the one atom dimension such that the conduction electrons are much more accessable due to some geometric circumstance perhaps even approaching superconductivity?

30th April, 2012 @ 06:35 am PDT
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