Optical absorption spectroscopy and properties of single walled carbon nanotubes at high temperature

•We show that the transition energy in SWCNT is temperature dependent.•The temperature dependency follows the Varshni-equation.•We demonstrate the existences of excitons in m-SWCNT.•We confirm the calculated transition energy by in literature for room temperature. Here, we present an experimental investigation of the optical spectra of single walled carbon nanotubes (SWCNT) at temperatures up to 1273K. This investigation gives insights into the electronic structure of metallic and semiconducting SWCNT at different temperatures by measuring the shift of the S11-, S22- and M11-band with optical absorption spectroscopy. We observed a decrease of the transition energies in both metallic and semiconducting SWCNT with increasing temperature determined by the shift of the S11-, S22- and M11-absorption bands. The shifts follow the Varshni-equation. Furthermore, calculation of the average exciton binding energy (80–90meV) in metallic SWCNT from the shift of the M11-band was performed. We demonstrate in this paper, that the optical absorption spectroscopy is an effective tool for characterisation of the electrical properties and structure of SWCNT.