Graft-induced midgap states in functionalized carbon nanotubes

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Covalent functionalization of carbon nanotubes (CNTs) introduces defects, impacting their electronic properties.
• Understanding defect-induced electronic states is crucial for tailoring CNT functionality.

Purpose of the Study:

• To unambiguously identify and characterize midgap states induced by covalent functionalization in semiconducting CNTs.
• To investigate the electronic structure modifications and their impact on electrical transport properties.

Main Methods:

• Conductance measurements on individual single- and double-walled CNTs before and after covalent functionalization.
• Numerical simulations, including ab initio calculations, to model the electronic structure of functionalized CNTs.
• Thermodesorption experiments to confirm the reversibility of the observed effects.

Main Results:

• Observation of increased OFF-state conductance in covalently functionalized CNTs due to graft-induced midgap states.
• Demonstration that these midgap states are localized around the covalent addends (4-bromophenyl grafts).
• Simulation results corroborating the presence and localization of midgap states with extended hydrogenoid profiles.

Conclusions:

• Covalent functionalization is a viable method for creating and controlling midgap electronic states in CNTs.
• The observed midgap states facilitate long-range coupling between functional groups along the nanotube axis.
• This approach enables further exploration of interacting one-dimensional localized electronic states.