Appearance of radial breathing modes in Raman spectra of multi-walled carbon nanotubes upon laser illumination

Abstract

The Raman spectra of the multi-walled carbon nanotubes are studied with the laser power of 5–20 mW. We observe the Raman bands at ∼1352, 1581, 1607, and 2700 cm −1 with 5 mW laser power. As the laser power is increased to 10, 15 and 20 mW, the radial breathing modes (RBMs) of the single wall carbon nanotubes (SWNTs) appear in the range 200–610 cm −1. The diameter corresponding to the highest RBM is ∼0.37 nm, the lowest reported so far. The RBMs are attributed to the local synthesis of the SWNTs at the top surface of the samples at higher laser power.