Although the conventional epitaxy growth including homoepitaxy and heteroepitaxy has major advantages of mono-crystalline films and large-area growth, there are remaining issues such as lift-off from the substrate and defects generated by lattice mismatch. The conventional heteroepitaxy of lattice-mismatched materials introduces critical defects inside the grown single-crystalline films to
relax the strain energy. As the lattice mismatch increases, the epitaxy films show a higher density of dislocations, resulting in loss of the original properties of materials. In addition, in order to separate the grown single-crystalline materials from the substrate, it is necessary to perform an indispensable process that can damage the substrate and grown film such as chemical etching, mechanical
exfoliation, and laser lift-off.  Here, we introduce the recently demonstrated epitaxy growth through two-dimensional graphene.
The relatively weak van der Waals field from the graphene layer is effectively controlled via a strong ionic field between epi-atoms and the substrate. Although various oxide materials show high ionicity, multi-layer graphene was used to prevent physical and chemical damage for growing singlecrystalline oxide onto graphene. The freestanding complex oxide materials were successfully
demonstrated using a metal stressor layer with a stronger tensile force than the ionic field between the grown film and the substrate. Furthermore, heteroepitaxy growth of III-V compound on a graphene-coated substrate shows the dramatically reduced dislocation density compared to the conventional heteroepitaxy due to interface displacement on the graphene's slippery surface. This spontaneous relaxation could enable the monolithic integration of largely lattice-mismatched systems with minimized dislocation density, which could eventually broaden the material spectrum for advanced electronics and photonics.