  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 the graphene-metal interface and detecting the resulting
shift in local charge neutrality point. We perform electrostatic simulations to
characterize the gating effect of a realistic scanning probe tip on a graphene
bilayer and find a good agreement with the experimental results.
