Self-Stacking Nanogrids

Estimated reading time: 4 minutes

Glass-like wires are not directly useful for electronic applications, but it might be possible to seed them with other types of molecules, which would make them electronically active, or to use them as a template for depositing other materials. The researchers hope that they can reproduce their results with more functional polymers. To that end, they had to theoretically characterize the process that yielded their results. “We use computer simulations to understand the key parameters controlling the polymer orientation,” Gadelrab says.

What they found was that the geometry of the cylinders in the bottom layer limited the possible orientations of the cylinders in the upper layer. If the walls of the lower cylinders are too steep to permit the upper cylinders from fitting in comfortably, the upper cylinders will try to find a different orientation.

It’s also important that the upper and lower layers have only weak chemical interactions. Otherwise, the upper cylinders will try to stack themselves on top of the lower ones like logs on a pile.

Both of these properties — cylinder geometry and chemical interaction — can be predicted from the physics of polymer molecules. So it should be possible to identify other polymers that will exhibit the same behavior.

According to Patrick Theofanis, an engineer at the chip manufacturer Intel, the nanocylinders themselves are less interesting than the spaces between them. “In general, the ability to pattern square holes is very useful for us,” he says.

“If you think of the back end of our chips, we have the back-end wiring, and then you have the interconnect layers between those back-end metal layers, and that’s where you’d like to be able to punch through holes and connect one layer to the next one. It’s an attractive technology because the aspect ratio is very tunable in the way that they’ve done their scheme.”

The research was funded by the National Science Foundation and the Taiwan Semiconductor Manufacturing Corporation.