Engineering of a charged incoherent BiFeO3/SrTiO3 interface

Atomic-level control of complex oxide heterostructure interfaces has resulted in unprecedented properties and functionalities. The majority of oxide heterointerfaces being intensively investigated maintain lattice coherence and exhibit a flawless epitaxial alignment between the films and the substrates. Here, we report the engineering of a charged incoherent BiFeO3/SrTiO3 interface using a tailored deposition sequence in reactive oxide molecular beam epitaxy. By introducing an additional iron oxide layer to disrupt the lattice coherence at the interface, the overlying BiFeO3 is stabilized in a tetragonal phase with its enhanced ferroelectric polarization pointing toward the SrTiO3 substrate, which drives free electrons to accumulate at the incoherent interface. Our findings reveal how controlling lattice coherence at oxide heterointerfaces can open new avenues for fabricating artificial oxide heterostructures with unique properties through precise interface engineering.