Degradation of carbon nanotubes by electron bombardment in radio-frequency glow discharge afterglows

A capacitively coupled radio-frequency afterglow is used to isolate the role of electron bombardment in the degradation process of muti-walled carbon nanotubes (MWNTs). MWNTs grown on a metal substrate act as a nanostructured anode that accelerate and focus electron bombardment, facilitated by the field enhancement effect. Tip-localized MWNT degradation has been observed in scanning electron microscope images showing the progression of the MWNT degradation process. This finding is confirmed by Raman spectra. GC-MS measurements indicate that the major products of MWNT degradation are short unsaturated hydrocarbons, identified as both propyne and 1,3-butadiyne vapours. This finding is corroborated by time-resolved optical emission spectroscopy during plasma oxidation of the degradation products. Analysis of the kinetics of plasma oxidation confirm that MWNT degradation produces species consistent with thermal evaporation, such as short carbon chains, C3-C4, but not monatomic or diatomic species, C1 and C2.