Reading and writing charge on graphene devices

We use a combination of charge writing and scanning gate microscopy to map and modify the local charge neutrality point of graphene field-effect devices. We give a demonstration of the technique by writing remote charge in a thin dielectric layer over a graphene-metal interface and detecting a shift in the local charge neutrality point. We perform electrostatic simulations to characterize the interaction between a realistic scanning probe tip, the deposited charge, and the graphene and find a good semi-quantitative agreement with the experimental results.