MIT scientists precisely control width and composition of nanowires as they grow

Researchers at MIT have developed technology that can precisely control the width and composition of nanowires – microscopic fibers that can be “grown” in the lab.

Thanks to the development, it possible to grow complex structures that are optimally designed for particular applications. The results are published in the journal Nano Letters.

Nanowires have been of great interest because structures with such tiny dimensions — typically just a few tens of nanometers, or billionths of a meter, in diameter — can have very different properties than the same materials have in their larger form. That’s in part because at such minuscule scales, quantum confinement effects — based on the behavior of electrons and phonons within the material — begin to play a significant role in the material’s behavior, which can affect how it conducts electricity and heat or interacts with light.

The team at MIT was able to control and vary both the size and composition of individual wires as they grew. Nanowires are grown by using “seed” particles, metal nanoparticles that determine the size and composition of the nanowire. By adjusting the amount of gases used in growing the nanowires, researchers were able to control the size and composition of the seed particles and, therefore, the nanowires as they grew.

These nanowires are far too small to see with the naked eye, but the team was able to observe them using electron microscopy, making adjustments to the growth process based on what they learned about the growth patterns. Using a process called electron tomography, they were able to reconstruct the three-dimensional shape of individual nanoscale wires.

Precisely structured nanowires could facilitate a new generation of semiconductor devices, says one of the researchers. Such control of nanowire geometry and composition could enable devices with better functionality than conventional thin-film devices made of the same materials, she adds.