Role of covalent defects on phonon softening in metallic carbon nanotubes.
We have examined how electrical characteristics and charging dependent Raman G-band phonon softening in individual metallic carbon nanotubes are influenced by covalent defects. In addition to decreasing electrical conductance with increasing on/off current ratio eventually leading to semiconducting behavior, adding covalent defects reduces the degree of softening and broadening of longitudinal optical (LO) phonon mode of the G-band near the charge neutrality point where the bands cross. On the other hand, the transverse optical (TO) mode softening is enhanced by defects. Implications on the interpretation of Raman G-band phonon softening and on utilizing Raman spectroscopy to examine covalent functionalization are discussed.
Department of Materials Science and Engineering, University of Illinois, Urbana, Illinois 61801, USA.
Khoi T
KT
Nguyen
Moonsub
M
Shim