Volume 90 Issue 49 | p. 32 | Concentrates
Issue Date: December 3, 2012

New Method Grows Nanowires At Record Pace

Gas-phase aerotaxy technique grows tiny semiconductor wires on the fly
Department: Science & Technology
Keywords: nanowire, epitaxy, aerotaxy, solar cells, batteries, gas-phase synthesis, electronics
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ON THE FLY
Gold nanoparticles (from left) pass through a reactor where they meet gallium and arsenic precursors that form GaAs nanowires.
Credit: Adapted from Nature
Scheme describing new method of growing nanowires in gas phase. Gold nanoparticles get evaporated, size selected, passed through a furnace, and then sent into a reactor tube, where they seed growth of gallium arsenide nanowires. Finally, they are deposited onto a substrate.
 
ON THE FLY
Gold nanoparticles (from left) pass through a reactor where they meet gallium and arsenic precursors that form GaAs nanowires.
Credit: Adapted from Nature
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Scanning electron microscope image of a GaAs nanowire grown from a 120-nm gold seed particle (white sphere at left) with the aerotaxy method.
Credit: Nature
Micrograph of gallium arsenide nanowire grown via a new gas-phase method called aerotaxy. The white area at left is a gold nanoparticle that seeded the growth of the wire in a reactor tube.
 
Scanning electron microscope image of a GaAs nanowire grown from a 120-nm gold seed particle (white sphere at left) with the aerotaxy method.
Credit: Nature

A new gas-phase synthesis technique grows semiconductor nanowires on the fly at a rate of 1 µm per second—20 to 1,000 times faster than traditional methods (Nature, DOI: 10.1038/nature11652). The approach could enable low-cost industrial production of next-generation solar cells and batteries. To achieve the improved growth rate, researchers led by Lars Samuelson of Sweden’s Lund University begin with gold aerosol nanoparticles, which they heat and pass into a gas reactor tube. These gold seed particles combine with gallium from (CH3)3Ga and arsenic from AsH3 to form tiny GaAs wires as they flow through the tube. Changing the size of the gold particles, the tube temperature, and the reaction time affects the quality and dimensions of the nanowires produced by this method, called aerotaxy. The limitation of traditional gas-phase epitaxy methods is that they grow nanowires on substrates in batches, rather than continuously, says Brian A. Korgel, a chemical engineer at the University of Texas, Austin. This new approach, Korgel adds, “is a big step toward future nanowire applications that will require large amounts of material.” The Swedish firms Sol Voltaics and QuNano have both filed patents related to the technique.

 
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