Now, researchers from the UCLA Henry Samueli School of Engineering and Applied Science, Purdue University and IBM have successfully grown silicon-germanium semiconducting nanowires for potential use in next-generation transistors.
These nanowires — which measure from a few tens to a few hundreds of nanometers in diameter and up to several millimeters in length — could help speed the development of smaller, faster and more powerful electronics, according to study co-author Suneel Kodambaka, a UCLA professor of materials science and engineering.
The team's research appears in the Nov. 27 issue of the journal Science.
"We are excited for two reasons," said Frances Ross, manager of IBM's Nanoscale Materials Analysis department and corresponding author of the study. "One is that we have extended our knowledge of the fundamental physics of the process by which nanowires grow. The other is the improved prospect of using nanowires in high-performance electronic devices."
"The nanowires are so small you can place them in virtually anything," Kodambaka said. "Because of their small size, they are capable of having distinctly different properties, compared to their bulk counterparts."
The team showed they could create nanowires with layers of different materials, specifically silicon and germanium, that were defect-free and atomically sharp at the junction — critical requirements for making efficient transistors out of the tiny structures. The "sharper" the interface between the material layers — in this case, just one atom, or close to one atom, thick — the better the electronic properties.
"We think this study is significant because it provides a solution to the problem of growing sharp interfaces in nanowires, thereby addressing an important limitation in the growth of nanowires," Ross said.
According to Kodambaka, silicon-germanium nanostructures also have thermoelectric applications, in which heat is converted into electricity.
"The Jet Propulsion Laboratory uses bulk chunks of silicon-germanium to power their satellites, and now there is a lot of interest in using a similar technology in automobiles. These nanowires have great potential in any area involving electronics," Kodambaka said.
To grow the silicon-germanium nanowires, tiny particles of a gold-aluminum alloy are first heated to temperatures above 370 degrees Celsius and melted inside a vacuum chamber. A silicon-containing gas is then introduced into the chamber, causing silicon to precipitate and form wires under the droplets. A germanium-containing gas is used to form the germanium wires.
"Think of it as ice growing from water vapor or the formation of ice crystals during a snow storm. You can get forests of ice wires under the right conditions instead of getting snow flakes or flat films of sleet," Kodambaka said. "But instead of water vapor, we introduced silicon vapor to get the silicon wire."
"The challenge was to create a really sharp interface between the silicon and germanium in each wire," Kodambaka said. "So we cooled the liquid droplets until they solidified. This allowed us to get rid of excess silicon in the alloy. Then, germanium wire segments could be grown on the silicon with the introduction of germanium vapor, and sharp interfaces formed."
The next step for the team is to grow the same structures over larger areas in a conventional growth reactor rather than in a tiny area under the microscope.
"This will allow my colleagues at IBM to process the wires into devices and measure their electronic properties," Ross said. "Of course, we would hope that the properties are improved, compared to conventional nanowires; and if this works out, we will look into new devices and try out different metal alloys to determine which is best for making devices."
The research was funded by the National Science Foundation through the NSF's Electronic and Photonic Materials Program in the Division of Materials Research, and also in part by the University of California Energy Institute (UCEI).
The UCLA Henry Samueli School of Engineering and Applied Science, established in 1945, offers 28 academic and professional degree programs, including an interdepartmental graduate degree program in biomedical engineering. Ranked among the top 10 engineering schools at public universities nationwide, the school is home to seven multimillion-dollar interdisciplinary research centers in wireless sensor systems, nanotechnology, nanomanufacturing and nanoelectronics, all funded by federal and private agencies.
Wileen Wong Kromhout | EurekAlert!
Touch Displays WAY-AX and WAY-DX by WayCon
27.06.2017 | WayCon Positionsmesstechnik GmbH
Air pollution casts shadow over solar energy production
27.06.2017 | Duke University
An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.
Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...
Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.
Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...
Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.
As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...
Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.
With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...
Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine
Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...
19.06.2017 | Event News
13.06.2017 | Event News
13.06.2017 | Event News
27.06.2017 | Power and Electrical Engineering
27.06.2017 | Information Technology
27.06.2017 | Physics and Astronomy