Decrease in Terahertz Conductivity of Graphene Under Electron Beam Irradiations
Electron beam (e-beam) irradiations are often involved for characterizing graphene-based terahertz (THz) devices or realizing graphene surface plasmons. Here, based on THz time-domain spectroscopy (TDS) and two-dimensional scanning system, the time dependence and the in situ mapping images of changed THz conductivity of graphene induced by e-beam irradiations are studied. The change in THz signals with irradiation indicates a decrease in the THz conductivity as a result of electron doping in graphene through irradiation. And the spatial imaging maps of the decreased THz conductivity reveal diverse electron doping speeds in graphene during different current e-beam irradiations. Additionally, different theoretical doping models are given for explanations of the imaging maps and the calculated results by doping models are in good accordance with the experimental results. Our findings are of significance for understanding the change in THz conductivity and carrier transport of graphene under e-beam irradiations.