Nitrogen doping of single-walled carbon nanotube by using mass-separated low-energy ion beams

Mass-separated nitrogen ions with the mass number of 14 were irradiated to the single-walled carbon nanotubes (SWCNTs) under an ultra high-vacuum pressure of 10(-7) Pa for the purpose of achieving nitrogen doping in nanotubes. The incident angle of the ion beam was normal to the target nanotube, and the ion beam energy was 30 eV, which was close to the displacement energy of graphite. The dependence of the structure of SWCNTs on the ion dose was investigated. The ion dose ranged from 2.8 x 10(14) to 2.2 x 10(16) ions/cm(2). The nitrogen ions are incorporated into graphite sheets of SWCNTs after irradiation at 2.8 x 10(14) ions/cm(2). The graphite structure is distorted and many defects are induced in the nanotube by the nitrogen incorporation. The structure is changed to amorphous after irradiation at 2.2 x 10(16) ions/cm(2). The nitrogen ions with the ion energy of 25 eV are irradiated to the field effect transistor device with the nanotube channel. The n-type characteristic appears upon ion irradiation, and the device exhibits ambipolar behavior.