Nanowires — microscopic fibers that can be “grown” in the lab — are a hot research topic today, with a variety of potential applications including light-emitting diodes (LEDs) and sensors. Now, a team of MIT researchers has found a way of precisely controlling the width and composition of these tiny strands as they grow, making it possible to grow complex structures that are optimally designed for particular applications.

Nanowires fabricated using the new techniques developed by Silvija Gradečak and her team can have varying widths, profiles and composition along their lengths, as illustrated here, where different colors are used to indicate compositional variations. 

Silvija Gradečak, professor of materials science and engineering at the Massachusetts  Insitute of Technology, and her team,  were 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, Gradečak was  able to control the size and composition of the seed particles and, therefore, the nanowires as they grew. “We’re able to control both of these properties simultaneously,” she says.

The results are described in a new paper authored by Silvija Gradečak and her team, published in the journal Nano Letters.
Source: http://web.mit.edu/newsoffice/2012/controlled-nanowire-growth-0222.html