Pressure dependence of optical transitions in semiconducting single-walled carbon nanotubes

The effects of applied hydrostatic pressure on the optical transitions in semiconducting single-walled carbon nanotubes with different diameters and chiralities have been studied using optical absorption and photoluminescence spectroscopy. The excitonic transitions associated with the band-gap (the first van Hove transition) energies in the carbon nanotubes are found to shift to lower energy at a rate depending on nanotube structure. The excitonic transitions between the first excited confinement states (the second van Hove transitions) are found to be much less sensitive to the applied hydrostatic pressure. All nanotubes show a dependence on their chirality in terms of pressure coefficient of the band-gap energy, with the larger-diameter nanotubes exhibiting a higher sensitivity of the band-gap energy to hydrostatic pressure. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.