By KELLY HEARN, UPI Technology Writer
WASHINGTON, Feb. 8 (UPI)
--
Scientists have created a wire that is 20 and 65 nanometers wide, about a dozen times smaller than the period on the end of a sentence.
The wires are some of the smallest nanostructures ever created and are expected to further embolden the rapidly expanding field of molecular electronics.
The current method for making atomic-sized structures, called electron beam lithography, is not capable of operating precisely below 50 nanometers. It is also time-consuming and costly, the researchers will point out Friday in the Washington-based journal Science.
Chemist Paul Weiss of Penn State University and Anat Hatzor, a post-doctoral fellow, will report they have sidestepped the technical deficiencies of the device by using organic molecules as "rulers" that allowed them to build the tiny wires.
More specifically, the Philadelphia team created two relatively large parallel nanostructures of gold on a base of silicon. The structures served as templates or casts for the nanowires.
Next, they applied acids and metal ions atop those structures. As acid and ions grew, they reduced the size of the space between the two original parallel nanostructures. Into that narrow spacing, or cast, the scientist placed atoms of gold. When the metal-organic layers were taken off, the gold nanowires remained, just 20 nanometers in width -- 20 billionths of a meter -- and 1 micron, or a millionth of a meter.
The process of using molecules to squeeze the space between the nanostructures is similar to baking cookies on a cookie sheet. If heated, the cookies will expand and the space between them gets smaller. If icing is then poured over the cookies and allowed to harden, the cookies could be removed -- leaving small "wires" of icing.
Because the scientist knew the size of the original nanostructures and the size of the molecular layers placed atop it, they were able to determine the size of the space between them.
"We have the technology and know-how to make things smaller and smaller," Weiss told United Press International in a telephone interview. "We can also make molecules bigger and bigger. But there is a gap between those two capabilities. This work is a step toward closing that gap."
"This will enable us to prepare structure that we couldn't make before," explained Hatzor, who said she spent a few months designing the casting system. She said the method could be considered revolutionary because it gives researchers precise control over the size and shape of structures below 50 nanometers.
Weiss said the procedure, which was developed at Penn State's National Nanofabrication Users' Network Facility, could be used to make structures of various shapes and sizes not possible by other means.
--
Copyright 2001 by United Press International.
All rights reserved.
--