Ferroelectric Switching in Hybrid Molecular-Beam-Epitaxy-Grown BaTiO₃ Films

Molecular beam epitaxy (MBE) is a promising synthesis technique for both heterostructure growth and epitaxial integration of ferroelectric BaTiO₃. However, direct measurement of the remnant polarization (P_r) has not been previously reported in MBE-grown BaTiO₃ films. We report the in situ growth of an all-epitaxial SrRuO₃/BaTiO₃/SrRuO₃ heterostructure on Nb-doped SrTiO₃ (001) substrates by hybrid MBE using metal-organic precursors. This capacitor structure consisting of 16 nm SrRuO₃/40 nm BaTiO₃/16 nm SrRuO₃ shows hysteretic polarization-electric field (P-E) curves with P_r ∼ 15 μC cm^-2 at frequencies ranging from 500 Hz to 20 kHz, after isolating the intrinsic ferroelectric response from non-ferroelectric contributions using the Positive-Up-Negative-Down (PUND) method. We hypothesize that the asymmetry in switching behavior and current leakage has origins in structural defects. This work opens the door to defect-engineered ferroelectric BaTiO₃-based heterostructures grown by hybrid MBE for future electronic, photonic and spintronic applications.