Structural and electrical properties of ozone irradiated carbon nanotube yarns and sheets

Poor electrical conductivity of carbon nanotube (CNT) yarn and sheets has been one of the main hurdles in their practical application. Here, we demonstrate that the ozone irradiation can be an effective approach to reduce the resistivity of spun CNTs bundle with oxidization and induced defects. The CNT yarn and sheet are fabricated from a spinnable vertically aligned CNT forest synthesized by a thermal chemical vapor deposition. The electrical resistance of a CNT yarn and sheet reduces with a certain period of ozone irradiation; however for a long duration of ozone irradiation resistance increases with structural deformation of the CNTs. A comparative study on the effect of shapes between the CNT yarn and sheet with morphological change in the CNTs due to the ozone irradiation is performed. It was observed that the desorption energy of ozone molecules was slightly large for the CNT yarn due to the difference of adsorption sites. The fraction of defects induced by the ozone irradiated on the CNT yarn was estimated from the ultimate resistance change with temperature and Raman spectroscopy.