How do the electron beam writing and metal deposition affect the properties of graphene during device fabrication?

Electron beam exposure and metallic contact formation are commonly used processes for fabrication of graphene-based devices. We report a detailed Raman study on the influence of medium energy electron irradiation and metal atoms on defectivity and doping on monolayer and bilayer graphene. It is found that the electron beam could induce disorder into graphene layers mainly by three ways: knocking-off carbon atoms, reaction with substrate and deposition of amorphous carbon. We observe that bilayer graphene exhibits higher stability under e-beam irradiation than monolayer graphene. Our study on the formation process of metallic contacts reveals that evaporation of Ti normally cannot induce any defects into graphene while deposition of Au can introduce a large amount of damage. This work could be valuable for further development of processes in the fabrication of graphene-based devices.