There may be a bit more room at the bottom, after all.

In 1959 physicist Richard Feynman issued a famed address at a meeting of the American Physical Society, a talk entitled "There's Plenty of Room at the Bottom." It was an invitation to push the boundaries of the miniature, a nanotech call to arms that many physicists heeded to great effect. But more than 50 years since his challenge (pdf), researchers have begun to run up against a few hurdles that could slow the progression toward ever-tinier devices. Someday soon those hurdles could threaten Moore's Law, which describes the semiconductor industry's steady, decades-long progression toward smaller, faster, cheaper circuits.

One issue is that as wires shrink to just nanometers in diameter, their resistivity tends to grow, curbing their usefulness as current carriers. Now a team of researchers has shown that it is possible to fabricate low-resistivity nanowires at the smallest scales imaginable by stringing together individual atoms in silicon.

The group, from the University of New South Wales (U.N.S.W.) and the University of Melbourne in Australia, and from Purdue University in Indiana, constructed their wires from chains of phosphorus atoms. The wires, described in the January 6 issue of Science, were as small as four atoms (about 1.5 nanometers) wide and a single atom tall. Each wire was prepared by lithographically writing lines onto a silicon sample with microscopy techniques and then depositing phosphorus along that line. By packing the phosphorus atoms close together and encasing the nanowires in silicon, the researchers were able to scale down without sacrificing conductivity, at least at low temperatures.

"What people typically find is that below about 10 nanometers the resistivity increases exponentially in these [silicon] wires," says Michelle Simmons, a U.N.S.W. physicist and a study co-author. But that appears not to be a problem with the new wires. "As we change the width of the wire, the resistivity remains the same," she says.

Phosphorus is often introduced into silicon because each phosphorus atom donates an electron to the silicon crystal, which promotes electrical conduction or even can serve as bits in quantum computation schemes. But those conduction electrons can easily be pulled away from duty, especially in tiny wires where the wire's exposed surface is large compared with its volume. By encasing the nanowires entirely in silicon, Simmons and her colleagues made the conduction electrons more immune to outside influence. "That moves the wires away from the surfaces and away from other interfaces," Simmons says. "That allows the electron to stay conducting and not get caught up in other interfaces."

Demonstrating electric transport in a wire so small "is quite an accomplishment," says Volker Schmidt, a researcher at the Max Planck Institute of Microstructure Physics in Halle, Germany. "And being able to fabricate metallic wires of such dimensions, by this theoretically microelectronics-compatible approach, could be a potentially interesting route for silicon-based electronics."

The wires, the researchers say, have the carrying capacity of copper, indicating that the technique might help microchips continue their steady shrinkage over time. The new finding might even extend the life of Moore's Law, Arizona State University in Tempe electrical engineer David Ferry wrote in a commentary in Science accompanying the research.

8 Comments

1. 1. Papaspud 06:14 PM 1/5/12

   The ingenuity of people can be amazing, 4 atoms across and 1 high, doesn't get much smaller,at least if moving electrons is your objective. I also noted that it is in " low tempretures", the first person to find a room temp. superconductor will be rich beyond their imagination.

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2. 2. Tony_Who 12:13 PM 1/6/12

   Current production capability is 32 nanometer wire widths.
   
   "Intel Factory Tour - 32 nm Manufacturing Technique"
   http://www.youtube.com/watch?v=SeGqCl3YAaQ
   
   Thanks,
   -Tony

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3. 3. Will_in_BC 12:57 PM 1/6/12

   Nice pun in the headline.
   
   The article says that the wires continue to conduct as their dimensions are shrunk "at least at low temperatures" but doesn't specify what is meant by this. It would be nice to know if these low temperatures are within the normal operating range of most devices as opposed to, say, something near absolute zero. Anyone know?

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4. 4. Russell Seitz 01:18 PM 1/6/12

   The cutest thing is that this far down on the nanoscale, the silicon substrate warps P-P bonds into the conductive, graphene-like , black phosphorus structure

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5. 5. tucanofulano 07:33 PM 1/6/12

   To really save copper vigorously advance Tesla's work on wireless electricity.

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6. 6. scilo 11:47 PM 1/6/12

   I wonder if Moore's law will run out before this tech is available?

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7. 7. Qedlin in reply to Will_in_BC 12:30 AM 1/7/12

   My immediate question as well. To be commercially viable they need to operate to at least 110 C and preferrably 160 C. No supercooling permitted.

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8. 8. swatiramesh in reply to Will_in_BC 11:08 PM 1/7/12

   hi, normally "at least at low temperatures" means atlest at 77K or 4K ( these are two accessible temperature for experimentalists using Liquid Nitrogen and Liquid Helium respectively.) Sure normal operating temperature for any device is 300K ( or 27C or room temerautre), but there are many issues to be solved before these small devices start to operate at room temperature.
   Well to confirm this, i need to read the actual journal article.

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