Investigation of the initial stages of defect formation in carbon nanotubes under irradiation with argon ions

The formation of defects in carbon nanotubes under irradiation with argon ions is investigated. The pi plasmons generated in single-walled and multiwalled carbon nanotubes are examined using electron energy-loss spectroscopy. In the course of experiments, the supramolecular structure of nanotubes is stepwise modified by an argon ion beam (the maximum irradiation dose is 360 mu C/cm(2)). The content of argon ions implanted into a nanotube structure is controlled using Auger electron spectroscopy. The effect of ion irradiation on the pi-plasmon energy E-pi and on the half-width at half-maximum delta E of the pi-plasmon spectrum is determined experimentally. An expression relating the above quantities and the concentration of implanted argon is derived. It is shown that the formation of defects under ion irradiation is a discontinuous process occurring in a stepwise manner. A qualitative phenomenological interpretation is proposed for the experimentally revealed decrease in the pi-plasmon energy E-pi and for its attendant broadening of the pi-plasmon spectrum. The assumption is made that the microscopic mechanism of the observed phenomena is associated with the narrowing of the energy pi subbands in the electric field of charged defects generated by ions. (C) 2005 Pleiades Publishing, Inc.