Impurity screening in graphene-based double-layer structures

We have studied the charged impurity screening in graphene-based double-layer structures. We assumed that at least one of the two layers is graphene, while the second layer could be a graphene, a conventional two-dimensional electron gas, or other two-dimensional structures. We have calculated the static dielectric function of this structure within the random phase approximation. Using the static dielectric function, and considering a charged impurity placed in the first layer, we have investigated how the potential of this impurity becomes screened in the first and second layers.