Structure assigned optical transitions from single walled carbon nanotube based high absorber composite thin film coatings

Abstract

Single walled carbon nanotubes (SWCNTs) exhibit unique electronic and optical properties owing to their one-dimensional (1D) structures that are described by a set of chiral indices (n, m), diameter (d) and chiral angle (θ). Absorption and optical spectroscopies are powerful techniques to determine the structure and diameter distribution of the SWCNTs through bulk measurements. In this work, we correlate structure assigned absorption features with the corresponding optical transitions observed from the SWCNT based high absorber composite thin film coatings. Various optical signatures demonstrated here are direct manifestation of electronic transitions happening within the sharp van Hove (vH) states of valence band, v2 to conduction band, c2 from SWCNTs of particular chiral indices and diameter. These transitions arising within the vH singularities due to unique 1D structures of SWCNTs, correspond to the energy band E22. The presentwork based on empirical calculations according to tight binding model (TB) approximation, represents unique way of correlating structure assigned absorption features with the optical transitions that can have direct impact in tuning the bandgap of SWCNTs of specific diameter and chirality for nanoelectronics and nanophotonic applications.