Polarization Dependence of the C 1s X‐ray Absorption Spectra of Individual Multi‐Walled Carbon Nanotubes

Abstract

The polarization dependence (linear dichroism) of the C 1s X-ray absorption spectrum of individual multi-walled carbon nanotubes (MWCNTs) is measured using scanning transmission X-ray microscopy. A very strong dichroic effect is found in the C 1s --> pi* transition, with almost complete disappearance of this transition when the electric-field (E)-vector is aligned parallel to high-quality (low-defect) MWCNTs and maximum intensity when the E-vector is orthogonal to the tube axis. In contrast, there is very little dichroism in the C 1s --> sigma* transitions. The origin of this polarization effect is explained. The magnitude of the polarization dependence is found to differ in MWCNTs synthesized by different methods (arc discharge versus chemical vapor deposition). This is ascribed to differences in densities of sp(2)-type defects. The potential for use of this signal to characterize defects in single-carbon-nanotube devices is discussed.

Ion and electron irradiation-induced effects in nanostructured materials

“…161,162 The polarization dependence ͑linear dichroism͒ of the C 1s x-ray absorption spectrum of individual carbon nanotubes measured using scanning transmission x-ray microscopy 163 can be used to assess the anisotropy of the atomic network of the system and thus the concentration of defects.…”

Revealing the Role of Catalysts in Carbon Nanotubes and Nanofibers by Scanning Transmission X-ray Microscopy

“…Scanning transmission X-ray microscopy (STXM) has been considered to be an effective tool to localize and characterize the electronic structure of carbon nanomaterials891011121314. STXM combines both X-ray absorption near-edge structure (XANES) spectroscopy and microscopy with a spatial resolution of a few tens of nanometers12.…”

“…XANES is an element-specific spectroscopic technique involving the excitation of electrons from a core level to local and partial empty states of a defined character1214. The combination of classical XANES method with a high spatial resolution in STXM provides a unique capability to explore electronic and structural information in carbon nanomaterials891011121314. Here by employing STXM, Fe and Ni residues, the widely used catalyst in the CNT/CNF growth1516, in individual CNT and CNF were imaged with a concurrent identification of their electronic structure.…”

X-ray absorption spectroscopy by full-field X-ray microscopy of a thin graphite flake: Imaging and electronic structure via the carbon K-edge

“…This peak is composed of two distinct features at 291.5 eV and 292.6 eV. The sharp feature at 291.5 eV is an exciton [24], its sharpness reflecting the strong correlation effects of electron–hole pairs within the flake. The broad peak at 292.6 eV is related to the transition from the C 1s level to the relatively nondispersing σ* states at the Γ point of the Brillouin zone (BZ) [25].…”