Now researchers at the University of Cambridge in the UK in collaboration with IBM have developed a self-assembly process for nanowires that makes it possible to embed quantum dots within them, expanding their range of potential applications.
“The key to building functional nanoscale devices is to control materials and their interfaces at the atomic level,” said Stephan Hofmann of the University of Cambridge and one of the paper’s senior authors, in a press release. “We’ve developed a method of engineering inclusions of different materials so that we can make complex structures in a very precise way.”
The new self-assembly technique, which is described in the journal Nature Materials, is based on the typical process for producing nanowires: vapor-liquid-solid (VLS) synthesis. VLS offers a fast way for producing nanowires based on chemical vapor deposition.
In VLS, chemical vapors disolve into a droplet of liquid catalyst. The chemicals crystalize at the base of the droplet, forming the nanowire, which pushes the catalyst up as it grows. Over the years, VLS has developed into a highly controlled process in which every detail of the nanowires from its size to its crystal structure can be precisely controlled.
The Cambridge researchers were able to build upon the VLS technique by using the catalyst droplet as a “mixing bowl” to add materials that lead to new growth phases. These new phases take the shape of faceted nanocrystals, or quantum dots.
“The technique allows two different materials to be incorporated into the same nanowire, even if the lattice structures of the two crystals don’t perfectly match,” said Hofmann. “It’s a flexible platform that can be used for different technologies.”
The inclusion of quantum dots in the nanowires would seem to indicate potential optoelectronic applications, for which the nanocrystals are well known. For example, the researchers anticipate that these new nanowires could find use in semiconductor lasers and other light emitters.