  The interface between graphene and the ferroelectric superlattice
$\mathrm{PbTiO_3/SrTiO_3}$ (PTO/STO) is studied. Tuning the transition
temperature through the PTO/STO volume fraction minimizes the adsorbates at the
graphene-ferroelectric interface, allowing robust ferroelectric hysteresis to
be demonstrated. Intrinsic charge traps from the ferroelectric surface defects
can adversely affect the graphene channel hysteresis, and can be controlled by
careful sample processing, enabling systematic study of the charge trapping
mechanism.
