"The key to building functional nanoscale devices is to control materials and their interfaces at the atomic level," said Dr Stephan Hofmann of the Department of Engineering. "We've developed a method of engineering inclusions of different materials so that we can make complex structures in a very precise way."
The technique developed by Dr Hofmann's team builds on the vapour-liquid-solid (VLS) approach used currently. In VLS, a catalytic droplet seeds and feeds the nanowire, allowing it to assemble by one atomic layer at a time. VLS, says the team, brings a high degree of control over such factors as composition, diameter and structure. With the new approach, the catalytic droplet is not only used to grow the nanowire, but also to form new materials within it.
Using customised electron microscopes at IBM's TJ Watson Research Center and at Brookhaven National Laboratory, the researchers found that using the catalyst as a 'mixing bowl', with the order and amount of each ingredient programmed into a desired recipe, allowed the creation of nanowires with embedded nanoscale crystals – or quantum dots – of controlled size and position.
"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 Dr Hofmann. "It's a flexible platform that can be used for different technologies."
According to the researchers, possible applications for this technique range from atomically perfect buried interconnects to semiconductor lasers. The team also believes the process will allow 3D structures to be engineered.
