Fermi Level Engineering of Single-Walled Carbon Nanotubes by AuCl₃ Doping

Abstract

We investigated the modulation of optical properties of single-walled carbon nanotubes (SWCNTs) by AuCl 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 AuCl 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.

Strategy for Carrier Control in Carbon Nanotube Transistors

“…Recently, it has been reported that the redox potential difference between CNT and adsorbate is the key parameter in determining the charge-transfer direction. [85,86] The location of the work function of semiconducting and metallic CNTs, as well as the positions of the van Hove singularities of the valence and conduction band, is also strongly diameter dependent, as shown in Figure 10 a. The appropriate parameter in describing molecules is not the work function (F), but rather the redox potential.…”

“…Therefore, the work function values are transformed into the redox potential using the relationship, F/e = V+4.44 V, with the redox potential being expressed with respect to the normal hydrogen electrode (NHE). [85] Using the redox potential plot, it is now possible to choose the type of adsorbates (ads). If V ads > V CNT , the electron is transferred from the CNT to the adsorbate, the CNT changes to a ptype behavior, and, therefore, the adsorbate is a p-dopant.…”

<i>In Situ</i> Observation of Gold Chloride Decomposition in a Confined Nanospace by Transmission Electron Microscopy

“…14) Moreover, the G-band 12) of AuCl x @SWCNTs is significantly blue-shifted by ³20 cm ¹1 relative to that of cap-opened SWCNTs, which is consistent with previous reports; charge transfer from SWCNTs to AuCl 3 causes the blue shift of the G-band. 15,16) Figure 3 shows sequential TEM images of isolated AuCl x @SWCNTs; the images were recorded at 30 s intervals during e-beam irradiation (electron dose rate of ³1.7 © 10 6 electrons/nm 2 ·s) at room temperature. In the TEM images, a strong linear contrast inside SWCNTs, which is significantly different from that of AuCl x , is observed.…”

Adsorptive graphene doping: Effect of a polymer contaminant

“…This could have wider relevance to other fields where adsorptive doping is applied, such as in the doping of carbon nanotubes or other two dimensional materials. [19][20][21] To obtain these results, we fabricate and measure devices using CVD-grown monolayer graphene, as previously described. [22] Au/Cr (60:6 nm) electrodes in four-probe geometry, with inter-electrode distances contamination residues from graphene surface, [15] we employ two regimes: the devices are pre-annealed at < 3 × 10 −6 mbar at either 200 ˚C for 1 h or 300 ˚C for 2 hs.…”