In this work, swift heavy ion irradiation induced effects on the electrical properties of single layer graphene are reported. The modulation in minimum conductivity point in graphene with in-situ electrical measurement during ion irradiation was studied. It is found that the resistance of graphene layer decreases at lower fluences up to 3 × 1011 ions/cm2, which is accompanied by the five-fold increase in electron and hole mobilities. The ion irradiation induced increase in electron and hole mobilities at lower fluence up to 1 × 1011 ions/cm2 is verified by separate Hall measurements on another irradiated graphene sample at the selected fluence. In contrast to the adverse effects of irradiation on the electrical properties of materials, we have found improvement in electrical mobility after irradiation. The increment in mobility is explained by considering the defect annealing in graphene after irradiation at a lower fluence regime. The modification in carrier density after irradiation is also observed. Based on findings of the present work, we suggest ion beam irradiation as a useful tool for tuning of the electrical properties of graphene.
Ion beam irradiation is one of the methods to tune the properties of graphene oxide (GO) by modifying the ratio of sp 2 and sp 3 hybridization. However, the inherent defects present in GO during its synthesis deteriorate its properties (e.g., reduction efficiency) and are difficult to remove. We have earlier demonstrated the annealing of defects in carbon nanostructures (fullerene, carbon nanotube, and graphene) at a lower fluence of swift heavy ion (SHI) irradiation. In the present work, we have studied the irradiation of the GO film with 120 MeV Au ions at fluences ranging from 10 10 to 10 13 ions/cm 2 . In situ X-ray diffraction measurements showed an increase in the crystallinity of the GO film at low fluence. The irradiated samples showed an increase in the intensity of aromatic carbon bonds by Fourier transform infrared spectroscopy which indicates the maximization of graphitic regions for lower fluences up to 3 × 10 11 ions/cm 2 . Higher fluences of ion beam irradiation indicated the loss in crystallinity and presence of carbyne in Raman measurements. Thermal spike simulations were performed to understand the physical processes involved during ion beam irradiation by estimating the radii of core and halo of the tracks formed by SHI.
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