Changes of structure and electrical conductivity of multi-walled carbon nanotubes film caused by 3 MeV proton irradiation

The effects of 3 MeV proton irradiation for fluences of 3.5 × 10 ¹⁰ cm ^-2 to 3.1 × 1012 cm ^-2 on structure andelectrical conductivity of multi-walled carbon nanotubes (MWCNTs) film were investigated. The pristineand the irradiated MWCNTs films were characterized using scanning electron microscopy (SEM), Ramanspectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR),elemental analysis (EA) and electron paramagnetic resonance (EPR) spectroscopy in order to investigatethe effects of irradiation on their structure. Electrical conductivity of the MWCNTs films was characterizedbefore and after irradiation. SEM analysis reveals that the proton irradiation for the high fluence (morethan 3.6 × 10 ¹¹ cm ^-2 ) leads to evident changes in morphology of the MWCNTs film, such as forminguneven film surface, curve, shrinkage and fragmentation of nanotubes. Based on Raman, XPS, FTIR andEA analyses, it is confirmed that the 3 MeV protons with high fluence (more than 3.6 × 10 ¹¹ cm ^-2 ) candamage the structure of the MWCNTs, including increase of the disorder and the formation of functionalgroups. EPR spectroscopy shows that the electrons delocalized over carbon nanotubes increase withincreasing irradiation fluence, implying that the MWCNTs film might be sensitive to ionizing radiationto some extent. With increasing the irradiation fluence, the electrical conductivity of the MWCNTs filmdecreases due to the structural and morphological damage.