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The future of electronics may be in nanowires, tiny wires nearly a thousand times slimmer than a human hair. Electronics are getting smaller and smaller, and these wires enable useful amounts of electricity to flow in ever-shrinking devices. At Carnegie Mellon, a team of researchers made the first observation of nanowires that seemed to “crawl” along the surface of graphene films.

“We looked at the results, and they were kind of mind-blowing,” says Tzahi Cohen-Karni, a professor of materials science and engineering and biomedical engineering. “We set forth to understand why the nanowires crawled on the surface.” The team of researchers published their results in the July 2016 issue of Nano Letters.

Cohen-Karni’s excitement comes because the advantage of having nanowires “crawl” along the surface as opposed to growing vertically out of the surface is that they could make photodetectors—devices that convert light to electricity—more sensitive.

“Photodetectors made with nanocrawlers could potentially detect smaller amounts of light than their vertical nanowire counterparts,” he says.


Crawling nanowire along the surface of graphene films

Source: Carnegie Mellon University

The discovery of nanowires on graphene was a happy accident, according to Cohen-Karni.

“We tried a few experiments where we wanted to grow the nanowires up, out of the surface,” Cohen-Karni recalls. “My students told me that it didn’t work, so we looked at the results, and we were very surprised by what we saw.”

The team decided to investigate further what it was that made the nanowires crawl along the surface, so that they could have better control of the process in the future. The team found that adding hydrogen chloride gas at a certain point during the synthesis process made the wires more likely to crawl along the graphene surface than to grow vertically out of the graphene.

“This is why science can be so mind-blowing,” Cohen-Karni says. “You start out with some odd observation, and you think you messed up, but then you can investigate and learn why it happened.”