To build the computer chips of the future, designers will need to understand how an electrical charge behaves when it is confined to metal wires only a few atom-widths in diameter.
Now, a team of physicists at McGill University, in collaboration with researchers at General Motors R&D, have shown that electrical current may be drastically reduced when wires from two dissimilar metals meet. The surprisingly sharp reduction in current reveals a significant challenge that could shape material choices and device design in the emerging field of nanoelectronics.
The size of features in electronic circuits is shrinking every year, thanks to the aggressive miniaturization prescribed by Moore's Law, which postulated that the density of transistors on integrated circuits would double every 18 months or so. This steady progress makes it possible to carry around computers in our pockets, but poses serious challenges. As feature sizes dwindle to the level of atoms, the resistance to current no longer increases at a consistent rate as devices shrink; instead the resistance "jumps around," displaying the counterintuitive effects of quantum mechanics, says McGill Physics professor Peter Grütter.
"You could use the analogy of a water hose," Grütter explains. "If you keep the water pressure constant, less water comes out as you reduce the diameter of the hose. But if you were to shrink the hose to the size of a straw just two or three atoms in diameter, the outflow would no longer decline at a rate proportional to the hose cross-sectional area; it would vary in a quantized ('jumpy') way."
This "quantum weirdness" is exactly what the McGill and General Motors researchers observed, as described in a new paper appearing in Proceedings of the National Academy of Sciences. The researchers investigated an ultra-small contact between gold and tungsten, two metals currently used in combination in computer chips to connect different functional components of a device.
On the experimental side of the research, Prof. Grütter's lab used advanced microscopy techniques to image a tungsten probe and gold surface with atomic precision, and to bring them together mechanically in a precisely-controlled manner. The electrical current through the resulting contact was much lower than expected. Mechanical modeling of the atomic structure of this contact was done in collaboration with Yue Qi, a research scientist with the General Motors R&D Center in Warren, MI.
State-of-the-art electrical modeling by Jesse Maassen in professor Hong Guo's McGill Physics research group confirmed this result, showing that dissimilarities in electronic structure between the two metals leads to a fourfold decrease in current flow, even for a perfect interface. The researchers additionally found that crystal defects –- displacements of the normally perfect arrangement of atoms -- generated by bringing the two materials into mechanical contact was a further reason for the observed reduction of the current.
"The size of that drop is far greater than most experts would expect -– on the order of 10 times greater," notes Prof. Grütter.
The results point to a need for future research into ways to surmount this challenge, possibly through choice of materials or other processing techniques. "The first step toward finding a solution is being aware of the problem," Grütter notes. "This is the first time that it has been demonstrated that this is a major problem" for nanoelectronic systems."
Funding for this research was provided by the Natural Sciences and Engineering Research Council of Canada, le Fonds Québécois de la Recherche sur la Nature et les Technologies, and the Canadian Institute for Advanced Research.
Chris Chipello | EurekAlert!
Prediction: More gas-giants will be found orbiting Sun-like stars
22.02.2017 | Carnegie Institution for Science
NASA's fermi finds possible dark matter ties in andromeda galaxy
22.02.2017 | NASA/Goddard Space Flight Center
In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport
Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...
The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.
The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...
Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...
Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".
Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...
13.02.2017 | Event News
10.02.2017 | Event News
09.02.2017 | Event News
22.02.2017 | Power and Electrical Engineering
22.02.2017 | Life Sciences
22.02.2017 | Physics and Astronomy