Electron Beam Induced Structural Transformations of SWNTs and DWNTs Grown on Si₃N₄/Si Substrates

Electron beam induced structural transformations are investigated in single-wall carbon nanotubes (SWNTs), double-wall carbon nanotubes (DWNTs) and crossed nanotube junctions. The nanotubes studied here are synthesized by the chemical vapor deposition method. The response of the nanotubes to an electron beam is found to be influenced bythe presence of coatings of amorphous carbon, graphene fragments and structural defects on the tube surface. The dependence of structural modifications on electron beam irradiation dose is measured. While nanotubes with amorphous carbon, graphene fragment coverage and/or defects undergo rapid transformation leading to structure disintegration, those without such coverage or defects are more resistant to beam damage. In addition, it is shown that the amorphous carbon coverage on the double-wall nanotubes can be transformed into graphene layers during electron beam irradiation of coated nanotubes. Finally, the relative stabilityof nanotube side-wall and end-walls are investigated through sub-threshold energy and above threshold energy irradiation of a model system, C₆₀-filled nanotubes (Peapods^™). The data indicates that electron beams could be used to join nanotubes end-to-end without damaging the side-walls.