Impact of External Electronic Perturbations on Single-Walled Carbon Nanotube Electronic Structure: Scanning Tunneling Spectroscopy and Density Functional Theory

Understanding the local impact of environmental electronic perturbations on the local density of states (LDOS) of single-walled carbon nanotubes (CNTs) is critical for developing CNT-based devices. We present scanning tunneling microscopy and spectroscopy (STM/STS) investigations of CNTs adsorbed on both a metal, Au(111), and a dielectric, monolayer RbI on Au(111), serving as models for stronger and weaker electrostatic interactions, respectively. In both cases, STS revealed modulations in the CNT LDOS corresponding to features in the underlying material. We corroborate our STM/STS results with density functional theory calculations of the electronic structure of semiconducting CNTs in the presence and absence of an external dipole. DFT-calculated CNT LDOS qualitatively matched STM/STS results, providing key insight into the local impact external charges have on CNT electronic structure.