Structural measurements for single-wall carbon nanotubes by Raman scattering technique

The single-wall carbon nanotubes grown by different techniques have been in vestigated by Raman scattering and high resolution transmission electron mi croscopy (HRTEM). The tube diameter values and the tube distribution over d iameter have been estimated from the position and shape of the low-frequenc y band in the Raman spectrum containing the 'breathing" modes. The diameter -dependent enhancement of the Raman signals from the different nanotube fra ctions occurred not only due to optical resonance with the laser excitation energy, but also due to thermo-induced resonances. The low-field electron emission from the single-wail carbon nanotube material has been measured. T he threshold fields were 0.75-2 V/mu m, the emission current reached the va lue 15 mA/cm(2) at fields of 10 V/mu m. (C) 1999 Acta Metallurgical Inc.