Japanese researchers have developed a way of soldering metal wires together on the nanoscale. The method will open the door to applications in nanocircuitry, they claim.

The demand for ever-smaller electronics has generated a great deal of interest in electrical nanocircuits. The way nanowires are connected is of key importance when making stable nanocircuits, say Takaaki Toriyama and Tsutomu Ishiwatari of Shinshu University, Ueda, Japan - simply laying nanowires across each other is mechanically unstable.

The stable silver nanowire joints could potentially be used in nanoelectronics

The previous method for joining silver nanowires involved chemically reducing chloroauric acid to produce metallic gold particles. When Toriyama and Ishiwatari tried this, they found that the silver wires corroded. By first treating the wires with excess thiol, which protects the surface of the silver, and then with chloroauric acid, they avoided corrosion and created a permanent join between the nanowires.

Next, Toriyama and Ishiwatari converted the chloroauric acid in the join to metallic gold. They found that after chemical reduction some of the acid remained, but by simply heating the join, they achieved complete conversion.

Toriyama and Ishiwatari conclude that the newly developed method is 'superior to chemical reduction' and says that it holds promise as a way of soldering nanowires for electronics.

'Toriyama and Ishiwatari's method is simple and promises to be useful in device fabrication and other nanotechnology applications,' says C N R Rao, an expert in materials chemistry at the Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India.

David Barden

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