Researchers at MIT have developed a method by which they can control the growth process of nanowires and thereby control the composition, structure, and even their resulting properties.
The MIT research team, led by Silvija Gradečak, assistant professor of materials science and engineering, followed the usual method of growing nanoparticles by using “seed” particles (metal nanoparticles), but in their experiments the researchers closely controlled the amount of gases used in the growth process.
The results, which were published in the journal Nano Letters, demonstrated that by controlling the gases interacting with the seed particles, the researchers were able to control the width and composition of the resulting nanowires.
Gradečak's team used an electron microscope to observe the effects that the gases were having on the growth process, and then the researchers adjusted the amount of gases to get the characteristics they wanted in terms of both structure and composition.
While the research team restricted their seed particles to indium nitride and indium gallium nitride, they say that the process will work with a variety of different materials.
Naturally, the goal of controlling the size and composition of nanowires is to change their properties. If you could fine tune the exact properties you wanted in a nanowire, you could use it in applications for which they are best suited.
The application that seems to be at the top of the list for the nanowires created by the MIT team is LED light bulbs. In this case, the nanowires would be used as a substrate replacing the expensive sapphire or silicon carbide typically used. Not only could the nanowires be a less expensive substrate, but they could also prove to be more efficient, according to Gradečak.
The varying diameters and structures could also make the nanowires useful in thermoelectric devices, in which waste heat can be turned into electricity. By changing the structure and thickness of the nanowires along their length, it’s possible to make them good conductors of electricity but bad conductors of heat, a much-desired property for thermoelectric power systems.