Tailoring structure and electrical properties of carbon nanotubes using kilo-electron-volt ions

Abstract

We report the effects of 30 and 50 keV Ga+ ion irradiation on the structure and electrical properties of arc-evaporated multiwalled carbon nanotubes (MWNTs). For 50 keV ions with doses of ∼1013 ions/cm2 the outer shells of the MWNTs remain intact, while the inner layers reorganize into highly ordered pillbox-like ∼5-nm-diam nanocompartments of varying lengths between 2 and 20 nm. Increasing the dose to ∼1014 ions cm−2 results in the gradual disordering of the graphitic shells and destroys the nanocapsules, while at doses of 1015 ions cm−2 the graphitic shells collapse into the hollow, resulting in the formation a homogenous amorphous rod. Irradiating nanotubes with 30 keV ions yields similar results, but at higher doses. Irradiated nanotubes exhibit a decrease in electron activation energy from 194 to 112 meV, while the semiconducting behavior is essentially preserved for ion doses up to 5×1015 ions cm−2. Ion irradiation could be a useful tool to locally modify nanotube structure and tailor properties for device applications.