Experimental determination of the local optical conductivity of a semiconducting carbon nanotube and its modification at individual defects

TL;DR

This study measures the local optical conductivity of a single semiconducting carbon nanotube with defects, revealing how defects modify optical properties at the nanoscale using energy loss spectroscopy and absorption techniques.

Contribution

It is the first to determine absolute optical constants of an individual defected nanotube, highlighting defect-specific modifications in exciton dynamics.

Findings

Defects cause characteristic changes near the E11 exciton peak.

Exciton lifetime and electronic states are altered by different defect types.

Optical conductivity variations are linked to defect-induced inhomogeneities.

Abstract

Measurements of optical properties at nanometre-level are of central importance for characterization of optoelectronic device. It was, however, hardly possible for the conventional light-probe measurements to determine the local optical properties from single quantum object with nanometrical inhomogeneity. Here we demonstrate the first successful determination of the absolute optical constants, including the optical conductivity and absorption coefficient, for an individual carbon nanotube with defects by comparing energy loss spectroscopy and optical absorption. The optical conductivity obtained from a certain type of defects indeed presents a characteristic modification near the lowest excitation peak (E11) where excitons and non-radiative transitions as well as phonon-coupled excitations are strongly involved. Detailed line-shape analysis of the E11 peak clearly shows different degree of exciton lifetime shortening and electronic state modification which is variable to the defect type.