“This is a significant conceptual leap in self-assembly,” said Brookhaven Lab physicist Aaron Stein. “In the past, we were limited to a single emergent pattern, but this technique breaks that barrier with relative ease. This is significant for basic research, certainly, but it could also change the way we design and manufacture electronics.”
The work was based on block copolymers, comprising chains of two distinct molecules linked together. To guide self-assembly, the team created substrate templates using electron beam lithography. A set of block copolymers was added to the substrate, which was then spin coated and baked. Thermal energy drives interaction between the block copolymers and the template, creating the final configuration.
The research team had previously discovered that mixing together different block copolymers allowed multiple line and dot nanostructures to form. “We had discovered an exciting phenomenon, but couldn’t select which morphology would emerge,” said Brookhaven physicist Kevin Yager. But the team found that tweaking the substrate changed the structures that emerged. By adjusting the spacing and thickness of the lithographic line patterns, the self assembling blocks could be converted into lines or high-density arrays of nano dots.
“In essence,” said Stein, “we’ve created ‘smart’ templates for nanomaterial self-assembly. How far we can push the technique remains to be seen, but it opens some very promising pathways.”
The scientists now plan to increase the sophistication of the process, using more complex materials in order to move toward more device-like architectures.
“This technique fits quite easily into existing microchip fabrication workflows,” said Yager. “It’s exciting to make a fundamental discovery that could one day find its way into our computers.”