  We evaluate the autocorrelation function of the electrostatic potential in
doped graphene due to nearby charged impurities. The screening of those
impurities is described by a combination of the polarization function for
graphene in random phase approximation with the electrostatic Green's function
of the surrounding dielectrics. Using the hard-disk model for a two-dimensional
distribution of impurities, we show that large correlation lengths between
impurities can give rise to anti-correlation in the electrostatic potential, in
agreement with recent experiments.
