Nov 142010

Ultra-clean gallium-arsenid nanowires grown on a silicon substrate gives hope of developing cheap and very effective solar cells. (Credit: Image courtesy of University of Copenhagen)

New ultra-clean nanowires produced at the Nano-Science Center, University of Copenhagen will have a central role in the development of new high-efficiency solar cells and electronics on a nanometer scale.

PhD student Peter Krogstrup, Niels Bohr Institute, in collaboration with a number of well-known researchers and the company SunFlake A/S, is behind the breakthrough. The new findings have recently been published in the journal Nano Letters.

Nanowires are one-dimensional structures with unique electrical and optical properties — a kind of building blocks, which researchers use to create nanoscale devices. In recent years, there has been a great deal of research into how nanowires can be used as building blocks in the development of solar cells. One of the challenges is controlling the production of nanowires. The new ultra-clean nanowires are part of the solution. Ultra clean means that the electronic structure is perfectly uniform throughout the nanowires, which is a very important part in obtaining nano-electronic devices of high performance. This is achieved by growing the wires without the use of a metal catalysis like gold, and at the same time having a perfect crystal of only one single structural phase which until now have been impossible for these types of nanowires.

“The ultra-clean wires are grown on a silicon substrate with an extremely thin layer of natural oxide. The element Gallium, which is a part of the nanowire material, reacts with the oxide and makes small holes in the oxide layer, and here the gallium collects into small droplets of a few nanometers in thickness. These droplets capture the element Arsenic — the other material in the nanowire and through a self-catalytic effect starts the growth of the nanowires without interference from other substances,” explains Peter Krogstrup. The breakthrough is the result of a year’s work in connection with his PhD.

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