  Low frequency 1/f noise is investigated in graphene, encapsulated between
hexagonal boron nitride (hBN) substrate in dual gated geometry. The overall
noise magnitude is smaller as compared to graphene on Si/SiO2 substrate. The
noise amplitude in the hole doped region is independent of carrier density
while in the electron doped region, a pronounced peak is observed, at Fermi
energy, EF ~ 90 meV. The physical mechanism of the anomalous noise peak in the
electron doped region is attributed to the impurity states originating from the
Carbon atom replacing the Nitrogen site in hBN crystal. Furthermore, the noise
study near Dirac point shows characteristic "M-shape", which is found to be
strongly correlated with the charge inhomogeneity region near Dirac point.
