Tailoring the intrinsic metallic states of double-walled nanotube films by self-soldered laser welding

The metallic state and resistivity of interconnected double-walled carbon nanotube bundles have been tuned by modifying two major components, including (1) structure of the bundles and (2) contacts at the heterojunctions between the bundles. Infrared laser illumination at controlled intensity on the nanotubes produces an amorphous carbon coating that subsequently serves as the solder material to weld the bundles at their heterojunction sites. The results show that without selective etching of metallic or semiconductor species, the crossover temperature at which metallic behavior changes to semiconducting can be tuned within a wide range (25-150 K). (c) 2007 American Institute of Physics.