Electronic and opto-electronic devices likely will benefit from a recent discovery that nanostructures can be constructed precisely and in very close proximity to each other. The discovery, made by scientists at Pennsylvania State University, uses organic molecules as 'molecular rulers,' permitting the fabrication of nanowires. The scientists made nanowires 15 to 70 nanometers wide, a few micrometers long, and spaced 10 to 40 nanometers apart.
The molecular ruler construction process requires first-growing 'parent' nanoscale structures in order to produce smaller 'daughter' structures. In one example, the scientists use two parallel gold nanostructures on a silicate substrate, formed by electron-beam lithography, as the starting point. Layers of organic molecules are applied atop the initial structures, temporarily making them bigger and wider. At the same time, the gap between structures is reduced.
Because the researchers know the precise thickness of the layers of films created by the molecules atop the structures, it's possible to calculate the size of the narrow space between the original and new structures to be formed. The organic molecules, which selectively bind to each other and to the substrate materials, provide molecular rulers that precisely determine the size of this resulting space. After deposition of a metal, such as gold, the organic layers are removed leaving behind only the original structures and the new daughter structures, a precise distance away.
Silicate is used as the substrate, gold for the prefabricated initial structures, and mercaptoalkanoic acid as the organic molecule. The organic molecules are used as resists since they resist attack and protect the material underneath them in various lithographic processing steps.
The technology is expected to be useful in miniaturizing devices for circuits, high-density data storage, and sensors. The scientists' work will also serve as a testbed in molecular electronics.
"Commercialization could be quite rapid, as we are able to work from existing processes," Paul S. Weiss, associate professor of chemistry at Penn State, tells Nanotech Alert. Regarding market impact, Weiss says "reaching dramatically smaller scales for semiconductor and related devices would be quite important, if we end up having an impact in this area." The scientists are also looking at connecting molecular devices as a target area for development.
A patent has been filed for the technology. Further information on the work can be found in the Feb. 9 edition of Science.
Details: Paul S. Weiss, Associate Professor, Dept. of Chemistry, Pennsylvania State University, 152 Davey Laboratory, University
Park, PA
16802-6300.
Phone: 814-865-3693. Fax: 814-863-5516. E-mail: stm@psu.edu.
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