Narrowest conducting wires in silicon ever made show the same current capability as copper

January 5, 2012, University of New South Wales
Image: UNSW Sydney

The narrowest conducting wires in silicon ever made – just four atoms wide and one atom tall – have been shown to have the same electrical current carrying capability of copper, according to a new study published today in the journal Science.

Despite their astonishingly tiny diameter – 10,000 times thinner than a human hair – these wires have exceptionally good electrical properties, raising hopes they will serve to connect atomic-scale components in the quantum computers of tomorrow.

"Interconnecting wiring of this scale will be vital for the development of future atomic-scale electronic circuits," says the lead author of the study, Bent Weber, a PhD student in the ARC Centre of Excellence for Quantum Computation and Communication Technology at the University of New South Wales, in Sydney, Australia.

Video: PhD student Bent Weber has created the tiniest conducting wire ever made, taking us a step closer to the creation of a practical quantum computer.

The wires were made by precisely placing chains of phosphorus atoms within a silicon crystal, according to the study, which includes researchers from the University of Melbourne and Purdue University in the US.

The researchers discovered that the electrical resistivity of their wires – a measure of the ease with which electrical current can flow – does not depend on the wire width. Their behaviour is described by Ohm's law, which is a fundamental law of physics taught to every high school student.

"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," says Weber.

The discovery demonstrates that electrical interconnects in silicon can shrink to atomic dimensions without loss of functionality, says the Centre's Director and leader of the research, Professor Michelle Simmons.

Wires just one atom tall have been created by inserting a string of phosphorus atoms in a silicon crystal by a team of researchers from the University of New South Wales, Melbourne University and Purdue University. This image from a computational simulation run of the wires shows electron density as electrons flow from left to right. The wires are 20 times smaller than the smallest wires now available and measure just four atoms wide by one phosphorus atom tall. Credit: Purdue University /Sunhee Lee, Hoon Ryu and Gerhard Klimeck
"Driven by the semiconductor industry, computer chip components continuously shrink in size allowing ever smaller and more powerful computers," Simmons says.

"Over the past 50 years this paradigm has established the microelectronics industry as one of the key drivers for global economic growth. A major focus of the Centre of Excellence at UNSW is to push this technology to the next level to develop a silicon-based quantum computer, where single atoms serve as the individual units of computation," she says.

"It will come down to the wire. We are on the threshold of making transistors out of individual atoms. But to build a practical quantum computer we have recognised that the interconnecting wiring and circuitry also needs to shrink to the atomic scale."

Creating such tiny components has been made possible using a technique called scanning tunnelling microscopy. "This technique not only allows us to image individual but also to manipulate them and place them in position," says Weber.

Explore further: Quantum leap: World's smallest transistor built with just 7 atoms

More information: "Ohm's Law Survives to the Atomic Scale," by B. Weber, et al. Science (2012).

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1.5 / 5 (10) Jan 05, 2012
Once the technology is perfected, this could mean ultralight spacecraft, computers, vehicles..heck anything that uses copper wiring.
5 / 5 (1) Jan 05, 2012
Once the technology is perfected, this could mean ultralight spacecraft, computers, vehicles..heck anything that uses copper wiring.

No. This only refers to interconnects within a chip. It would not make anything lighter. Also, why would you want an expensive brittle wire where a copper line would do just fine? Furthermore, the weight of wire in everything you mentioned is only a small fraction of the overall weight.

I can see only one possible application where this would be valid outside of chip manufacturing - an electrical pico motor (using tradition motor design) - and that's only if the micro world doesn't offer better opportunities in chemistry or quantum mechanics for a motor of a different design.
3 / 5 (2) Jan 05, 2012
Actually, what THIS portends is even SMALLER friggin phones, which means it'll be even MORE difficult to type a coherent message when SMSing. Thus, more grammatically incorrect, garbled translations from one person to another. Technology advances, and communication takes ANOTHER step backwards (sigh).
2 / 5 (4) Jan 05, 2012
The resistance in any conductor is inversely proportional to its cross sectional area and its length. Reduce both proportionally and resistance should theoretically remain the same. If in fact this law does extend to the sub-molecular level, where does that leave quantum physicists?
For you spaceship enthusiasts, I thought they used aluminum wiring.
3 / 5 (4) Jan 05, 2012
They'll be able to add features like voice recognition to smart phones, allowing fingerless texting. Imagine ... talking directly into a phone. What will they think of next?
5 / 5 (1) Jan 05, 2012
The resistance in any conductor is inversely proportional to its cross sectional area and its length. Reduce both proportionally and resistance should theoretically remain the same. If in fact this law does extend to the sub-molecular level, where does that leave quantum physicists?
For you spaceship enthusiasts, I thought they used aluminum wiring.

This IEEE ( http://spectrum.i...ic-scale ) article has more information that addresses this question:

"The phosphorus atoms have one more electron than silicon, and these extra electrons allow the nanowire to conduct," Simmons explains. "Within the wires we place the phosphorous atoms less than 1 nm apart so that the wave functions of the electron overlap to form a metallic-like state, and that gives us this low resistivity."
1 / 5 (1) Jan 07, 2012
However, we can often observe that for the silicon-based transisitors this separation cannot be less than 50nm to avoid this cross-talk effect. It's connected to so-called doping distance and such distance can be larger, than the scope of quantum effects. Every embedded phosphorus atom induces stress of silicon lattice and its higher electrochemical potential decreases the binding force of electrons in the wide area around it. After all, this effect just explains, why small number of dopant atoms can influence the conductivity of bulk material in so pronounced way. Therefore, the placing of phosphorus atoms at the one-atom wide path doesn't mean, the current does flow through one atom wide path beneath them and we could achieve higher density of transistor integration so easily. Not to say about practical quantum computer, because this research just demonstrated the absence of quantum effects in conductivity.
not rated yet Jan 08, 2012
Here is the full paper for those interested. http://dl.dropbox...64-7.pdf
1 / 5 (1) Jan 08, 2012
ohms law.

You mean ohms "only applicable at the newtonian mass aggregate (non quantum) RULE of average results", NOT 'ohm's law'.

Screw off with the law stuff, as that is only applicable to social contract and has nothing to do with physics which is about learning new things, not anchoring things in dogma that has no potential for change or new discovery.

don't bring emotionally based social constructs and dogmatic religious constraints to the table of science.

of course, ohm's law, is taught to engineers and technicians..which are not to be discovering to playing games with their core characteristic of be being builders of things, not discoverers of things. engineers and technicians: not trained theoreticians or scientists.

So:when someone says they have some new ideas, if one is an engineer, please leave all prejudice at the door, as recall, you were taught to be dogmatic from the ground up.

Your teaching and entire scholastic directions are at fault, not the new science.
1 / 5 (1) Jan 08, 2012
Plainly said, conductivity is a function of electron orbital polarization agreement, or orientation coupling between the given molecules.

It is therefore...not unimaginable that silicon at the single atom join level, as this is the point of the announcement, that a methodology has been achieved (methodology, a key point-this is not about silicon specifically)..would have similar conductivity to a copper atom at the individual join level.

As we move into a mass aggregate geometrical lattice structure, frozen in place, then conductivity changes again. As we hopefully know, this happens at different points with different atomic signatures, or elements.

For example, under unrealistic or non practical conditions (for human use) we can get hydrogen atoms to do the same.

The article is principally about APPLICATIONAL METHODOLOGY, more than it is about the conductivity of silicon.

It is about the 'mass aggregate'-to-single atom 'changeover' in atomic behavioral analysis and realization.
1 / 5 (1) Jan 10, 2012
I hope we move to optical computing soon, than we can replace our copper wires with optical fibres.
not rated yet Feb 19, 2012
It is Ohms law, because you don't understand English or Science and you were reared badly.

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