Toward van der Waals epitaxy of transferable ferroelectric barium titanate films via a graphene monolayer

Abstract

Future “Internet of Things” requires transferable ferroelectric thin films for functional devices like sensors and actuators. We report here the growth of a typical ferroelectric perovskite compound, BaTiO₃, on a graphene monolayer which remains intact during the oxide growth process at high temperatures and at elevated oxygen pressure. The graphene facilitates the crystallization of BaTiO₃. The growth of BaTiO₃ on the graphene monolayer is found to follow the Volmer–Weber mode with the formation of three dimensional islands at the initial growth stage. Highly (001)-oriented BaTiO₃ crystalline films are fabricated and can be easily exfoliated using a metal stressor layer. The graphene monolayer remains attached to the exfoliated BaTiO₃ film which demonstrates good piezoelectric properties. These results not only demonstrate the possibility to fabricate high quality crystalline ferroelectric films via a graphene monolayer, but also open the pathway to realize van der Waals epitaxy ferroelectric films which can be transferred onto arbitrary substrates, particularly onto flexible substrates for wearable devices applications.