New technique of “sewing” crystals together to herald new electronics

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WASHINGTON, March 8 (Xinhua) — American scientists have found a new technique to “sew” two patches of crystals seamlessly together at the atomic level to create atomically-thin fabrics.

The study, published on Thursday in the journal Science, has opened up new possibilities for flexible LEDs or atom-thick two dimensional circuits that work both horizontally and laterally.

In electronics, joining different materials produces “heterojunctions,” the most fundamental components in solar cells, LEDs or computer chips.

The smoother the seam between two materials, the more easily electrons flow across it, which is essential for how well the electronic devices function, according to the researchers.

However, the two materials, made up of crystals-rigid lattices of atoms, may have very different spacing, so they don’t take kindly to being mashed together.

Park Jiwoong, professor of chemistry from University of Chicago, and Xie Saien from University of Cornell, tried to stitch different fabric-like, three-atom-thick crystals, simultaneously.

“Usually these are grown in stages under very different conditions; grow one material first, stop the growth, change the condition, and start it again to grow another material,” said Park, a lead author on the study.

He said they have developed a new process to find the perfect window that would work for both materials in a constant environment, so they could grow the entire crystal in a single session.

It has shown that at the points where the two lattices meet, one lattice stretches or grows to meet the other, instead of leaving holes or other defects.

Xie Saien, the first author on the paper, told Xinhua that “both LED and solar cells are based on heterojunctions, and the quality of sewing interface is directly linked to the efficiency of those applications. It also affects the speed and heating of computer chips.”

“It was exciting to see these three-atom-thick LEDs glowing. We saw excellent performance – the best known for these types of materials,” Xie said.

Park added that the stretching and compressing change the optical properties or the color of the crystals due to the quantum mechanical effects, so it has suggested a potential for light sensors and LEDs that could be tuned to different colors or strain-sensing fabrics that change color as they’re stretched.


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