Fermi Level Engineering of Single-Walled Carbon Nanotubes by AuCl_3 Doping

摘要

We investigated the modulation of optical properties of single-walled carbon nanotubes (SWCNTs) by AuCI_3 doping. The van Hove singularity transitions (E_(11)~S, E_(22)~S, E_(11)~M) in absorption spectroscopy disappeared gradually with an increasing doping concentration and a new peak appeared at a high doping concentration. The work function was downshifted up to 0.42 eV by a strong charge transfer from the SWCNTs to AuCI_3 by a high level of p-doping. We propose that this large work function shift forces the Fermi level of the SWCNTs to be located deep in the valence band, i.e., highly degenerate, creating empty van Hove singularity states, and hence the work function shift invokes a new asymmetric transition in the absorption spectroscopy from a deeper level to newly generated empty states.