Researchers create nanowires that grow on trees

The newly developed technique could produce improved nanomaterials for use in high-performance integrated circuits, biosensors, solar cells, LEDs and lasers.

The evolution of pine-tree-shaped nanotrees that feature tall trunks and tapering branches came as a surprise to developers Song Jin and Matthew Bierman of the University of Wisconsin-Madison.

"At the beginning we saw just a couple of trees, and we said, 'What the heck is going on here?'" said Jin, a Chemistry professor. "They were so curious."

"The long and twisting trunks were telling us we had a new growth mode," he said. "We think these findings will motivate a lot of people to do this purposefully, to design dislocation and try to grow nanowires around it."

Since their inception, nanowires that are just a few millionths of a millimetre thick have been produced in many forms, including belts, coils and flowers.

Most nanowires are created using metal catalysts, which cause the wires to grow in one dimension to form long rods.

The branches of Jin’s nanotrees elongate in the conventional manner. However, the trunks twist as they grow due to a “screw” dislocation, or defect, in their crystal structure.

Twisting trunks were much longer than branches, suggesting that wires created with a screw dislocation grow faster than those grown conventionally.

While dislocations are fundamental to the growth and characteristics of all crystalline materials, this is the first time they have been shown to aid the growth of one-dimensional nanostructures.

Researchers expect engineered dislocations to yield more elaborate nanostructures, as well as open doors to the discovery of more fundamental mechanical, thermal and electronic properties of dislocations in materials.

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