Effects of defects and thermal treatment on the properties of graphene

•Ion bombardment introduces defects and the defect type depends on ion dose.•Thermal annealing can heal defects (restore vacancy defect or refine edge defect).•Annealing cause doping effect and strain effect in graphene as well.•The strain level is highly dependent on annealing temperature and crystal perfection of graphene.

For graphene films, the change of crystal structure induced by ion bombardment as well as the doping and strain generated in thermal annealing process is addressed in this work. Experimental results show that both the structure and number of defects for graphene depends strongly on the ion dose. Furthermore, it is found that the structure defects caused by ion bombardment in graphene can be healed and the graphene samples are all doped in subsequent thermal annealing. The frequency shift of G and 2D peaks in Raman spectra reveals that compressive strain in graphene results from the thermal annealing treatment and the occurrence of strain is influenced by the thermal annealing and defects in graphene. For graphene, since defects and thermal annealing are unavoidable for the fabrication of graphene-based devices, the systematical investigation on these two aspects in this work is, therefore, of great importance and significance.