  We employed graphene as a patternable template to protect the intrinsic
surface states of thin films of topological insulators (TIs) from environment.
Here we find that the graphene provides high-quality interface so that the
Shubnikov de Haas (SdH) oscillation associated with a topological surface state
could be observed at the interface of a metallic Bi2Se3 film with a carrier
density higher than ~10^19 cm-3. Our in situ X-ray diffraction study shows that
the Bi2Se3 film grows epitaxially in a quintuple layer-by-layer fashion from
the bottom layer without any structural distortion by interfacial strain. The
magnetotransport measurements including SdH oscillations stemming from multiple
conductance channels reveal that the topological surface state, with the
mobility as high as ~0.5 m^2/Vs, remains intact from the graphene underneath
without degradation. Given that the graphene was prepatterned on arbitrary
insulating substrates, the TI-based microelectronic design could be exploited.
Our study thus provides a step forward to observe the topological surface
states at the interface without degradation by tuning the interface between TI
and graphene into a measurable current for device application.
