  We utilize an organic polymer buffer layer between graphene and conventional
gate dielectrics in top-gated graphene transistors. Unlike other insulators,
this dielectric stack does not significantly degrade carrier mobility, allowing
for high field-effect mobilities to be retained in top-gate operation. This is
demonstrated in both two-point and four-point analysis, and in the
high-frequency operation of a graphene transistor. Temperature dependence of
the carrier mobility suggests that phonons are the dominant scatterers in these
devices.
