A Raman Study on Free Standing Carbon Nanotubes

Thin bundles of single wall carbon nanotubes were suspended between metal blocks deposited on a silicon substrate. SEM images confirm that the parts of bundles between the blocks are free standing and those outside the contacts are lying on the silicon substrate. Since the tubes are usually a few micrometers long Raman spectra for nanotubes with and without the contact could be taken. Raman spectra show differences in the position and shape of the RBM and G lines depending on the site of the measurement. The RBM mode is usually very weak as compared to the G line. The results showed that the geometry of the experiment should be taken into account for interpretation of single tube or thin bundle Raman experiments.