Nano-welding creates tiny junctions

A multi-national team of materials scientists have discovered how to weld together single-walled carbon nanotubes, a discovery that could facilitate the controlled fabrication of molecular circuits.

A multi-national team of materials scientists have discovered how to weld together single-walled carbon nanotubes, a discovery that could facilitate the controlled fabrication of molecular circuits and nanotube networks.

Pulickel Ajayan, professor of materials science at Rensselaer Polytechnic, NY, and his colleagues in Germany, Mexico, the UK, and Belgium used irradiation and heat to form the welded junctions.

This is said to be the first time single-walled nanotubes have been welded together, although multi-walled nanotubes with junctions have already been created using growth techniques.

The electrical properties of single-walled nanotubes surpass those of multi-walled tubes, which is why so many researchers have been anxious to try this experiment, said Ajayan.

‘No one knew if junctions could be created,’ said Ajayan. ‘Single-walled carbon nanotubes are perfect cylinders without any defects, but in order to create junctions between them, inter-tube carbon-carbon bonds need to form. The irradiation and heating process we use creates just enough defects for these bonds to form without damaging their electrical properties.’

The results were obtained after several years of ongoing experimentation. The difficulty was finding nanotubes that cross and touch, which are critical for the initiation of inter-tube links. ‘Unfortunately, we can’t control this type of alignment just yet,’ Ajayan noted.

The researchers used an electron microscope that has the capability to irradiate and produce the heat necessary for the experiment. The high-voltage microscope, located in Stuttgart, Germany, is one of only a few worldwide.

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