Disentangling Vacancy Oxidation on Metallicity-Sorted Carbon Nanotubes
Abstract
Pristine single-walled carbon nanotubes (SWCNTs) are rather inert to O and N, which for low doses chemisorb only on defect sites or vacancies of the SWCNTs at the ppm level. However, very low doping has a major effect on the electronic properties and conductivity of the SWCNTs. Already at low O doses (80 L), the X-ray photoelectron spectroscopy (XPS) O 1s signal becomes saturated, indicating nearly all the SWCNT's vacancies have been oxidized. As a result, probing vacancy oxidation on SWCNTs via XPS yields spectra with rather low signal-to-noise ratios, even for metallicity-sorted SWCNTs. We show that, even under these conditions, the first principles density functional theory calculated Kohn-Sham O 1s binding energies may be used to assign the XPS O 1s spectra for oxidized vacancies on SWCNTs into its individual components. This allows one to determine the specific functional groups or bonding environments measured. We find the XPS O 1s signal is mostly due to three O-containing functional groups on SWCNT vacancies: epoxy (CO), carbonyl (CCO), and ketene (CCO), as ordered by abundance. Upon oxidation of nearly all the SWCNT's vacancies, the central peak's intensity for the metallic SWCNT sample is 60\% greater than for the semiconducting SWCNT sample. This suggests a greater abundance of O-containing defect structures on the metallic SWCNT sample. For both metallic and semiconducting SWCNTs, we find O does not contribute to the measured XPS O~1s spectra.
Keywords
Cite
@article{arxiv.1608.01424,
title = {Disentangling Vacancy Oxidation on Metallicity-Sorted Carbon Nanotubes},
author = {Duncan J. Mowbray and Alejandro Pérez Paz and Georgina Ruiz-Soria and Markus Sauer and Paolo Lacovig and Matteo Dalmiglio and Silvano Lizzit and Kazuhiro Yanagi and Andrea Goldoni and Thomas Pichler and Paola Ayala and Angel Rubio},
journal= {arXiv preprint arXiv:1608.01424},
year = {2016}
}