Ferroelectric Switching in Hybrid Molecular-Beam-Epitaxy-Grown BaTiO<sub>3</sub> Films.

Manjeshwar, Anusha Kamath; Yang, Zhifei; Liao, Chin-Hsiang; Wen, Jiaxuan; Koester, Steven J; James, Richard D; Jalan, Bharat · Nano Lett · 2025

basic_science · Level V

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Abstract

Molecular beam epitaxy (MBE) is a promising synthesis technique for both heterostructure growth and epitaxial integration of ferroelectric BaTiO<sub>3</sub>. However, direct measurement of the remnant polarization (<i>P</i><sub>r</sub>) has not been previously reported in MBE-grown BaTiO<sub>3</sub> films. We report the <i>in situ</i> growth of an all-epitaxial SrRuO<sub>3</sub>/BaTiO<sub>3</sub>/SrRuO<sub>3</sub> heterostructure on Nb-doped SrTiO<sub>3</sub> (001) substrates by hybrid MBE using metal-organic precursors. This capacitor structure consisting of 16 nm SrRuO<sub>3</sub>/40 nm BaTiO<sub>3</sub>/16 nm SrRuO<sub>3</sub> shows hysteretic polarization-electric field (<i>P</i>-<i>E</i>) curves with <i>P</i><sub>r</sub> ∼ 15 μC cm<sup>-2</sup> 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 BaTiO<sub>3</sub>-based heterostructures grown by hybrid MBE for future electronic, photonic and spintronic applications.