Tailoring of structural and electron emission properties of CNT walls and graphene layers using high-energy irradiation

Structural and electron emission properties of carbon nanotubes (CNTs) and multilayer graphene (MLG) are tailored using high-energy irradiation by controlling the wall thickness and number of layers. Ion irradiation by 100 MeV Ag+ ions at different fluences is used as an effective tool for optimizing defect formation in CNTs and MLGs, as analysed by micro-Raman spectroscopy. It is found that the cross section for defect formation (η) is 3.5 × 10−11 for thin-walled CNTs, 2.8 × 10−11 for thick-walled CNTs and 3.1 × 10−11 for MLGs. High-resolution transmission electron microscopy results also show that thin-walled CNTs and MLGs are more defective in comparison with thick-walled CNTs. Carbon atoms rearrange at a fluence of 1 × 1012 ions cm−2 in thick-walled CNTs to heal up the damage, which aggravates at higher fluences. The observed electron emission parameters of the modified thin-walled CNTs and MLGs are confirmed with the changes in the structures and are optimized at a fluence of 1 × 1011 ions cm−2. However, the electron emission properties of thick-walled CNTs are modified at a fluence of 1 × 1012 ions cm−2. The enhancement in the electron emission properties is due to the rearrangement of bonds and hence modified tips due to irradiation.