Press releases
Please quote Nature Materials as the source of these items.
May 2004
Nanowires grow like trees
Experts predict that conventional silicon-based electronics will hit fundamental barriers to further progress in speed and performance within the next 5 to 10 years. The development of techniques to grow new semiconducting materials in the form of nanoscale wires (semiconductor nanowires) is expected to play a key role in breaking through these barriers. In the June issue of Nature Materials, Lars Samuelson and co-workers, at Lund University, Sweden, demonstrate a technique for growing a class of tree-like nanowire structures — known as semiconductor nanotrees — which could not only aid the development of nanowire electronics, but also lead to new possibilities for photonics and solar-energy conversion.
The growth process used by the authors is based on established techniques for growing nanowires from gold nanoparticles — the nanoparticles act as catalytic 'seeds' that control the location and diameter of the grown nanowires. The process begins by growing the 'trunks' of the trees from where seeds are deposited on a substrate's surface; the nanowire continually forms underneath the gold seed. Once these trunks are grown to the desired length, a second layer of gold seeds is deposited onto them, which catalyses the subsequent growth of the nanotrees' branches. By controlling the size and density of the seeds used in both steps, the density and diameter of the nanotrees and their branches can be controlled.
The authors say that the next step will be to incorporate many different materials into the branches of their nanotrees. In doing so, the resemblance of the nanotrees to real trees could become more than just superficial. By adding 'leaves' in the form of light-harvesting molecules to the gold-tipped branches, the authors suggest that their nanotrees could act as photovoltaic cells for solar energy conversion. Or conversely, by growing them of both p- and n-type semiconductors, each branch could be made into nanoscale light-emitting diodes, to enable them to light up like Christmas trees.
