  The electrical transport properties of graphene are greatly influenced by its
environment. Owing to its high dielectric constant, strontium titanate (STO) is
expected to suppress the long-range charged impurity scattering and
consequently to enhance the mobility. However, the absence of such enhancement
has caused some controversies regarding the scattering mechanism. In graphene
devices transferred from SiO2 to STO using a newly developed technique, we
observe a moderate mobility enhancement near the Dirac point, which is the
point of charge neutrality achieved by adjusting the Fermi level. While bulk
STO is not known as a ferroelectric material, its surface was previously
reported to exhibit an outward displacement of oxygen atoms and
ferroelectric-like dipole moment. When placed on STO, graphene shows strong and
asymmetric hysteresis in resistivity, which is consistent with the dipole
picture associated with the oxygen displacement. The hysteretic response of the
surface dipole moment diminishes the polarizability, therefore weakens the
ability of STO to screen the Coulomb potential of the impurities.
