Electronic structure of aligned carbon nanotubes studied by scanning photoelectron microscopy

We have investigated the local electronic structures from tip and sidewall regions of aligned multi-walled carbon nanotubes (MWCNTs) by employing scanning photoelectron microscopy (SPEM) and micro-photoemission spectroscopy. Spatially resolved spectra of C Is, Si 2p and valence band have been measured. In particular, we compared the results from MWCNTs grown on Fe thin film catalyst with those using Ti catalyst, where the quality of alignment is much lower. For Fe catalyst, the SPEM data show that the tips have a larger density of states (DOS) and a higher C 1s binding energy than those of the sidewalls. In the case of Ti catalyst, Si 2p signal is detected within the CNT bundles. Different Si species can be identified. It is suggested that during the plasma-enhanced growth process, Si is transported into the CNT layer.