SAN FRANCISCO A breakthrough by an international team of scientists affiliated with the University of Wisconsin-Madison's Nanoscale Science and Engineering Center could pave the way for the building of complex, three-dimensional nanostructures using semiconductor photolithography equipment, according to the university.
A Jan. 27 posting on the university's Web site describes the breakthrough, made by UW-Madison chemical and biological engineering professors Paul Nealey and Juan de Pablo and colleagues at Georg-August University in Germany and the Paul Scherrer Institute in Switzerland. The team has discovered that materials known as "block copolymers" will spontaneously assemble into intricate 3-D shapes when deposited onto particular two-dimensional surface patterns created with photolithography, according to the posting.
The result, published in the Jan. 27 issue of Physical Review Letters, demonstrates a strategy for building complex, 3-D nanostructures by using standard semiconductor industry lithography tools, Nealey is quoted as saying.
"What we've done by using self-assembling block copolymers is to extend photolithography to three dimensions," Nealey is quoted as saying. "And the structures we've fabricated are completely different from the same block copolymer materials in the bulk."
According to the posting, the three-dimensional nanoscale structures could have potential applications ranging from catalysis and chemical separation to semiconductor manufacturing. The new 3-D nanostructures are stable, well defined and nearly defect-free over large areas, according to the posting. They also align perfectly with the underlying lithographic pattern, the posting states.
"This research shows that lithography combined with block copolymers is more versatile and powerful than we thought," de Pablo is quoted as saying. "We can now create completely new structures that will no doubt have new properties and new applications. Exactly what those structures will be is anybody's guess; here we demonstrate a complicated one. But the important thing is they open up a new field of exploration, both for these materials and this technology."
According to the posting, the researchers study specific block copolymers consisting of long chains of two different types of molecules, which alternate with each other in blocks. At high temperature, block copolymers are molten and randomly mixed, but when cooled down, the material spontaneously assembles into alternating layers of molecules, the posting states.
The posting says the work was supported by the National Science Foundation Nanoscale Science and Engineering Center at UW and the Semiconductor Research Corp.