Electron irradiation-induced change of structure and damage mechanisms in multi-walled carbon nanotubes

Owing to their unique structure and excellent electrical property, carbon nanotubes(CNTs) as an ideal candidate for making future electronic components have great application potentiality. In order to meet the requirements for space application in electronic components, it is necessary to study structural changes and damage mechanisms of multi-walled carbon nanotubes(MWCNTs), caused by the irradiations of 70 and 110 ke V electrons. In the paper, the changes of structure and damage mechanisms in the irradiated MWCNTs, induced by the irradiations of 70 and 110 ke V electrons, are investigated.The changes in surface morphology and structure of the irradiated MWCNT film are characterized using scanning electron microscopy(SEM), x-ray photoelectron spectroscopy(XPS), Raman spectroscopy, x-ray diffraction analysis(XRD), and electron paramagnetic resonance(EPR) spectroscopy. It is found that the MWCNTs show different behaviors in structural changes after 70 and 110 ke V electron irradiation due to different damage mechanisms. SEM results reveal that the irradiation of 70 ke V electrons does not change surface morphology of the MWCNT film, while the irradiation of 110 ke V electrons with a high fluence of 5 × 1015cm-2leads to evident morphological changes, such as the formation of a rough surface, the entanglement of nanotubes and the shrinkage of nanotubes. Based on Raman spectroscopy, XPS, and XRD analyses, it is confirmed that the irradiation of 70 ke V electrons increases the interlayer spacing of the MWCNTs and disorders their structure through electronic excitations and ionization effects, while the irradiation of 110 ke V electrons obviously reduces the interlayer spacing of the MWCNTs and improves their graphitic order through knock-on atom displacements. The improvement of the irradiated MWCNTs by 110 ke V electrons is attributed to the restructuring of defect sites induced by knock-on atom displacements. EPR spectroscopic analyses reveal that the MWCNTs exposed to both70 ke V electrons and 110 ke V electrons suffer ionization damage to some extent.