Low temperature emission spectra of individual single-walled carbon nanotubes: Multiplicity of subspecies within single-species nanotube ensembles

Low temperature photoluminescence (PL) studies of individual single walled carbon nanotubes were performed. A continuous-flow, liquid-He cryostat was used to control the sample temperature within the range of 4 to 60 K. The PL was collected by a microscope objective and imaged onto the entrance slit of an imaging spectrometer. Ultranarrow peaks that exhibited blinking and spectral wandering were observed. The analysis of the PL spectral shapes and temperature dependences indicate that one source causing this heterogeneity may be unintentional doping, which can strongly modify the emission spectra of doped tubes through Fermi-edge singularity effect.