  Graphene is a promising candidate to succeed silicon based devices and doping
holds the key to graphene electronics. Conventional doping methods through
surface functionalization or lattice modification are effective in tuning
carrier densities. These processes, however, lead to degradation of device
performance because of structural defect creation. A challenge remains to
controllably dope graphene while preserving its superlative properties. Here we
show a novel method for tunable and erasable doping of on-chip graphene,
realized by using a focused electron beam. Our results demonstrate
site-specific control of carrier type and concentration achievable by
modulating the charge distribution in the dielectric substrate. Thereby, the
structural integrity and electrical performance of graphene are preserved, and
the doping states are rewritable. Different logic operations were thus
implemented in a single graphene sheet. By extending this method to other
two-dimensional materials, this work lays out a blueprint for powerful yet
simple means of incorporating two-dimensional materials into prospective
electronic technologies.
