Testing new transistors in space
Northwestern University researchers have developed new transistors which are currently tested on the International Space Station (ISS) to see how they react to cosmic radiation. These transistors, which are using a new kind of gate dielectric material called a self-assembled nanodielectric (SAND), are exposed to radiation outside the ISS since March 22, 2008, and will stay there for one year. According to the researchers, these new transistors could be used 'on long space missions since early experiments on Earth indicate that the transistors hold up well when exposed to radiation.' But read more...
You can see above several pictures of these arrays of printed transistors on plastic. (Credit: Tobin Marks Group, Northwestern University). Here is a link to a larger version of this picture extracted from a McCormick School of Engineering at Northwestern University, "Northwestern Transistors Blast Off Into Space, Hang Out At International Space Station."
This research work has been led by Tobin Marks, Professor of Chemistry in the Weinberg College of Arts and Sciences and Professor of Materials Science and Engineering in the McCormick School of Engineering and Applied Science, and other members of his research group. It's also interesting to note that Marks was one of the five scientists who received the 2008 Prince of Asturias Award for Technical and Scientific Research for creating 'new materials for the benefit of mankind.'
So how are these transistors different from previous ones? "While silicon dioxide has historically been the dominant dielectric material for silicon-based electronics, Marks and his research group have been trying to create next-generation semiconductor and dielectric materials with properties that silicon and silicon dioxide can't provide -- such as transparency, printability and physical flexibility. The dielectric material would need to be thin, be a good insulator and be able to stabilize the charges moving through the semiconductor by having what is called a high dielectric constant, which is the relative ability of the material to store an electric charge for a given applied field strength. What resulted were SANDs, which Marks and his team created through a dipping process that creates self-assembled molecular thin films. Not only do SANDs meet all the requirements for next-generation dielectrics, but they were also found to be resistant to radiation."
Besides being useful for NASA's missions, this new kind of materials could also be useful on Earth for a variety of new technologies, including printable and transparent electronics. "'It's not just that these transistors are only good for outer space -- that's an illustration of just how tough they are,' Marks says. 'There is one technology on Earth, and only one, that will create as many features per unit time as a chip plant, and that's a modern newspaper printing plant, since the paper flies at hundreds of feet per second. Every time Intel wants to make a new chip, it costs billions of dollars and takes years to do. And yet every day they print a new New York Times. So we thought, could you use printing to create electronic circuits?'"
According to Marks, other kinds of applications could emerge. "Such a technology could print large items like solar cells and flat-panel displays, as well as small items, like circuits for cell phones and medical equipment. One of the long-range goals is to print radio frequency ID tags for items for sale in a store, which could provide information on the item's price, where it was manufactured, how it was made and how it was stored. It would also allow a cashier to zap a shopper's entire basket in one go, instead of scanning bar codes one-by-one."
For more information, this research work has been published in the Journal of the American Chemical Society under the title "Vapor Phase Self-Assembly of Molecular Gate Dielectrics for Thin Film Transistors" (Volume 130, Number 24, Pages 7528–7529, June 18, 2008). Here is a link to the abstract. "Organic-inorganic films grown entirely via a vapor-phase deposition process and composed of highly polarizable molecular structures are investigated as gate dielectrics in organic field-effect transistors (OFETs). Molecules 1 and 2 form self-ordered thin films via hydrogen bonding, and these organic-inorganic structures exhibit large capacitances and large pentacene OFET mobilities."
Sources: Northwestern University news release, June 10, 2008; and various websites
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