  Direct integration of ferroelectric Hf0.5Zr0.5O2 (HZO) on the inert surface
of graphene is challenging. Here, using nucleation layers to promote atomic
layer deposition of HZO was investigated. Different metals were deposited as
nucleation layers via dc sputtering. Ta, which oxidizes in air to form a
sub-stoichiometric oxide, was compared to Pt, which offers a more stable
electrode. For thicker interlayers, Ta leads to unstable switching behavior of
the HZO film. Conversely, at smaller thicknesses, a higher Pr can be achieved
with an oxidized Ta interlayer. In both cases, Pt offers higher endurance. The
choice of interlayer may strongly depend on the required application.
