  The epitaxial growth of functional materials using a substrate with a
graphene layer is a highly desirable method for improving structural quality
and obtaining free-standing epitaxial nano-membranes for scientific study,
applications, and economical reuse of substrates. However, the aggressive
oxidizing conditions typically employed to grow epitaxial perovskite oxides can
damage graphene. Here, we demonstrate a technique based on hybrid molecular
beam epitaxy that does not require an independent oxygen source to achieve
epitaxial growth of complex oxides without damaging the underlying graphene.
The technique produces films with self-regulating cation stoichiometry control
and epitaxial orientation to the oxide substrate. Furthermore, the films can be
exfoliated and transferred to foreign substrates while leaving the graphene on
the original substrate. These results open the door to future studies of
previously unattainable free-standing nano-membranes grown in an
adsorption-controlled manner by hybrid molecular beam epitaxy, and has
potentially important implications for the commercial application of perovskite
oxides in flexible electronics.
