Self-healing kinetics in monolayer graphene following very low energy ion irradiation

Monolayer graphene subjected to 13 and 90 eV Ar ion irradiation was probed by in-situ Raman spectroscopy. At 90 eV ion irradiation, a simple damage accumulation is seen. However, at 13 eV, immediately after damage formation, significant graphene self-healing is observed in real time. We argue that energy deposition through very-low-energy ion collisions can create vacancies and carbon adatoms which can diffuse easily on the surface and recombine afterward. The self-healing kinetics exhibit a fast (∼10 s) and a slow regime (∼30 min), which cannot result only from adatom-vacancy recombination. Based on a defect kinetic model, self-healing efficiency is revealed to be limited by dimer formation. Yet, the interplay between Stone-Wales defects and adatoms enables progressive release of the latter, and subsequent graphene self-healing on a longer time scale.