Nanowires might enable engineers to solve a problem threatening to derail the electronics industry. New technologies will be needed for industry to maintain Moore's law, an unofficial rule stating that the number of transistors on a computer chip doubles about every 18 months, resulting in rapid progress in computers and telecommunications. Doubling the number of devices that can fit on a computer chip translates into a similar increase in performance. However, it is becoming increasingly difficult to continue shrinking electronic devices made of conventional silicon-based semiconductors.
"In something like five to, at most, 10 years, silicon transistor dimensions will have been scaled to their limit," Stach said.
Transistors made of nanowires represent one potential way to continue the tradition of Moore's law.
The researchers used an instrument called a transmission electron microscope to observe the nanowire formation. Tiny particles of a gold-aluminum alloy were first heated and melted inside a vacuum chamber, and then silicon gas was introduced into the chamber. As the melted gold-aluminum bead absorbed the silicon, it became "supersaturated" with silicon, causing the silicon to precipitate and form wires. Each growing wire was topped with a liquid bead of gold-aluminum so that the structure resembled a mushroom.
Then, the researchers reduced the temperature inside the chamber enough to cause the gold-aluminum cap to solidify, allowing germanium to be deposited onto the silicon precisely and making it possible to create a heterostructure of silicon and germanium.
The cycle could be repeated, switching the gases from germanium to silicon as desired to make specific types of heterostructures, Stach said.
Having a heterostructure makes it possible to create
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