Atomic structure and electronic properties of single-wall carbon nanotubes probed by scanning tunneling microscope at room temperature

TLDR

The study employed room‑temperature STM to perform a detailed 3‑D structural analysis of single‑walled carbon nanotubes in ambient conditions. STM imaging revealed both rope‑bundled and isolated tubes, with ropes exhibiting highly oriented, uniform‑diameter tubes and isolated tubes displaying variable chirality (0°–30°) and diameters (1–3 nm); STS confirmed that chirality governs the transition from metallic to semiconducting behavior, and a rectifying response was observed at a 25° chiral angle, highlighting potential for nanodevice applications.

Abstract

A detailed three-dimensional structural analysis of single-walled carbon nanotubes was carried out using a scanning tunneling microscope (STM) operated at room temperature in ambient conditions. On a microscopic scale, the images show tubes condensed in ropes as well as tubes which are separated from each other. For a single-wall nanotube rope, the outer portion is composed of highly oriented nanotubes with nearly uniform diameter and chirality. On separated nanotubes, atomically resolved images show variable chirality ranges between 0°–30°, and variable diameter (1–3 nm), with no one type dominant. From STM and scanning tunneling spectroscopy measurements we confirmed the correlation between chirality and the electronic properties, namely the tuning from metallic to semiconducting. We also observed a rectifying behavior correlated with the chiral angle of 25°, an important observation for nanodevices application.