A group of engineers and researchers working together from IBM, Purdue University, and the University of California at Los Angles has learned to create nanowires coated with materials that make for efficient transistors. The nanowires have very sharply defined layers at the atomic level that allow the wires to be efficient transistors.

Eric Stach, associate professor of materials Engineering from Purdue said, "Having sharply defined layers of materials enables you to improve and control the flow of electrons and to switch this flow on and off."

The team of researchers says that electronic devices are often constructed of heterostructures. The term heterostructures means that the structure contains sharply defined layers of different semiconducting materials like silicon and germanium. According to the researchers, the challenge in the past has been the capability of producing nanowires with the requisite defined layers.

The team has detailed its findings in a paper published in the November 27 edition of the journal Science. The transistors that the team have developed are not made on flat pieces of silicon. These nanowires are grown vertically making them have a much smaller footprint, which in turn allows for many more of the nanowires to be placed on the same piece of silicon.

Stach said, "But first we need to learn how to manufacture nanowires to exacting standards before industry can start using them to produce transistors."

The researchers used a transmission electron microscope to view the nanowire formation. The nanowires were formed by heating tiny particles of a gold-aluminum alloy in a vacuum chamber. After the alloy was melted the researchers introduced silicon gas and the alloy bead absorbed the gas becoming supersaturated with silicon. This caused a silicon wire to grow from the alloy bead producing a silicon wire that was topped with a mushroom-like gold-aluminum alloy bead.

At that point, the researchers reduced the temperature of the chamber enough to allow the alloy bead at the top of the wire to solidify, thereby allowing germanium to be deposited on the silicon precisely creating the required heterostructure needed to create a transistor. The heterostructure allows the formation of a germanium gate in each transistor allowing devices to switch on and off.

"The cycle could be repeated, switching the gases from germanium to silicon as desired to make specific types of heterostructures," Stach said.