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Nanowires may allow many more transistors to be placed on computer chips in the future

Engineers and researchers predict that in the next five to ten years the dimensions of silicon transistors will have been scaled to their limits and will be unable to get any smaller. Without a new breakthrough in creating smaller transistors, Moore's Law will fall flat.

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.



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By Orac4prez on 11/30/2009 1:37:33 AM , Rating: 2
Silicon is cheap (comparatively) and the complexities of fabricating chips and the mechanisms for controlling manufacture, stopping current leakage, heat dissipation, etc have been developed over time. The level of sophistication and knowledge to produce these high quality chips cannot be underestimated. Many of the solutions are specific for silicon and could not be readily used for other materials. Sadly, it is not possible to manufacture novel chips in an economic manner yet with any other material. There is a lot of research going on on alternative technologies and some of these will undoubtedly be utilised for specialised applications. Intergating these technologies into existing chips and devices will be attended by a range of engineering, chemical and physical problems which need to be solved.

Just because silicon has been around for a long time is no reason to drop development of silicon devices. There will be many more iterations of the current technologies before anything else comes along. There are many people currently actively looking at silicon replacements, but things like quantum dots are still at the scientific curiosity stage.


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