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We have investigated the change of atomic and electronic structures of fluorinated single-walled carbon nanotubes (SWCNTs) using x-ray photoemission spectroscopy (XPS), electrical resistivity measurements, and transmission electron microscopy (TEM). The fluorine content increases with increasing reaction temperature up to 300 °C. XPS indicated that the fluorinated SWCNT reveals an ionic-bonding character at low concentration and covalent-bonding character at high concentration. The resistivity increases with reaction temperatures, resulting from the band gap enlargement at high fluorine concentration. It is also observed from TEM that the fluorination at reaction temperature above 250 °C leads to the disintegration of the CNT structures and formation of various phases such as multiwall-like and turbostratic morphologies.

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We have investigated the structural transformation of fluorinated singlewalled nanotubes (SWNTs) induced by electron-beam irradiation during the transmission electron microscope observations. Heavily fluorinated SWNT bundles were systematically transformed into multiwall-like nanotubes by releasing fluorine atoms during electron-beam irradiation and even broken into two pieces of the capped graphitic structures. Such structural transformations at relatively low kinetic energy (< or = 300 keV) could be explained by the local strains induced by fluorination, where C-C bonds that were fluorine-attached became 1.53 A, a single bond similar to that of a diamond, from our density functional calculations. We propose a possible concerted pathway for the structural transformation of fluorinated SWNTs induced by electron-beam irradiation based on the experimental observations.