Disentanglement of the electronic properties of metallicity-selected single-walled carbon nanotubes

The inherent structure of single-walled carbon nanotubes (SWCNTs) provides them tremendous value as archetypical one-dimensional (1D) solids, which exhibit van Hove singularities in their local density of states, Tomonaga-Luttinger liquid behavior, ballistic transport properties, and in many other aspects, features of 1D quantum systems, which allow the study of fundamental problems. Therefore, unraveling the signature of their peculiar electronic structure as pristine material is a prerequisite for tracing any modification. Here, we show the disentanglement of the unique 1D features and bonding environments in clean metallicity sorted nanotube films. The photoemission and x-ray absorption responses unambiguously reveal how the fine structure in the C1s edge and photoemission valence band separately discerns the SWCNT metallic and semiconducting nature. This has crucial implications for applications allowing for instance finding the limit of maximum conductivity in transparent electrodes or the uniformity of power transistors, among others.

Figure 1

(Color online) Schematics showing the relative abundance of metallicity sorted nanotubes and the corresponding fraction of the DOS. The histograms illustrate the abundance of metallic (left) and semiconducting (right) SWCNTs within the diameter range given from Raman spectroscopy and optical absorption measurements. The diameter distribution is a Gaussian centered at 1.37 nm and it has a 0.8 nm spread. The lower figures show the respective fraction of the TB DOS of the semiconducting and metallic SWCNTs.

Figure 2

(Color online) (a) C1s photoemission of metallic SWCNT (upper curve) and semiconducting SWCNT (lower curve) as conducted at 400 eV photon energy. The inset shows a PES survey scan up to 1200 eV. (b) The C1s line of the metallic and semiconducting SWCNT on an expanded scale. The solid lines are fits using a line shape analysis with a Doniach-Sunjic (metal) and Voigtian line shapes (semiconductors).

Figure 3

(Color online) (a) Valence band photoemission spectra of metallic (upper curve) and semiconducting (lower curve) conducted at 150 eV photon energy. (b) High-resolution XAS response of metallic (upper curve) and semiconducting (lower blue curve).

Figure 4

(Color online) $\pi$ band response in the valence band PES conducted at 150 eV for the metallic (a) and the semiconducting SWCNTs (b). The inset in a shows the expanded region around $E_F$ on an expanded scale. The black lines in the main panels show the fraction of the TB DOS of the semiconducting and metallic SWCNTs probed. The diameter cumulative TB DOS in Figs. 1b, 1d are broadened by the experimental resolution and the labels $M_{1\cdots 3}$ and $S_{1\cdots 5}$ depict the position of the vHs.

Figure 5

(Color online) Close up of the high-resolution XAS C1s ${\pi }^{\star }$ absorbtion edges (circles) of metallic (a) and semiconducting SWCNT (b) together with the results of a line shape analysis (lines). The lower insets depict the diameter cumulative TB DOS broadened by the experimental resolution. The labels denote the vHs $\left(M_{1\cdots 4}^{\star },S_{1\cdots 5}^{\star }\right)$, and the overall conduction band $\left({\pi }^{\star }\right)$.