Abstract
In this study, resonance Raman spectroscopy (RRS) is employed to probe the structural information of CVD-synthesized single-walled carbon nanotubes (SWNTs) in ambient environment at various temperatures ranged from 300 K to 700 K. SWNTs are fabricated crossing as-formed deep trench on SiO2/Si to avoid the interferences from surrounding media such as the substrates. Furthermore, the enhanced RRS from suspended SWNTs (su-SWNTs) also helps to observe the slight changes of principal peaks as the temperature increased. We specially use the well-established Si Raman thermology to monitor and determine the accurate surface temperature of the measured su-SWNTs. The frequency of G+ peak is found downward shifted with the increase of temperatures due to the softening of C-C bonding strengths, where the changes are reversible during different temperature cycles. Temperature coefficients of the characteristics peaks are estimated respectively. The force constant of C-C bond is used to explain why the temperature coefficients of different chiralities are different. The initial force constant, the chiral angle, and the tube diameter all might be the causes of the different temperature coefficients of the individual suspended-SWNTs. However, there are too many phonon modes in various chiralities, so the temperature-dependent Raman feature is affected by other factors. The Raman feature would not be influenced by one factor only.