Observation of Strong Polarization Enhancement inFerroelectric Tunnel Junctions
2019
Ferroelectric heterostructures,
with capability of storing data
at ultrahigh densities, could act as the platform for next-generation
memories. The development of new device paradigms has been hampered
by the long-standing notion of inevitable ferroelectricity suppression
under reduced dimensions. Despite recent experimental observation
of stable polarized states in ferroelectric ultrathin films, the out-of-plane
polarization components in these films are strongly attenuated compared
to thicker films, implying a degradation of device performance in
electronic miniaturization processes. Here, in a model system of BiFeO3/La0.7Sr0.3MnO3, we report
observation of a dramatic out-of-plane polarization enhancement that
occurs with decreasing film thickness. Our electron microscopy analysis
coupled with phase-field simulations reveals a polarization-enhancement
mechanism that is dominated by the accumulation of oxygen vacancies
at interfacial layers. The results shed light on the interplay between
polarization and defects in nanoscale ferroelectrics and suggest a
route to enhance functionality in oxide devices.
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