Direct Imaging of Nanoscale Ferroelectric Domains and Polarization Reversal in Ferroelectric Capacitors

Ferroelectric thin films present a powerful platform for next-generation computing and memory applications. However, domain morphology and dynamics in buried ferroelectric stacks have remained underexplored, despite their importance for real device performance. Here, nanoprobe X-ray diffraction (nano-XRD) is used to image ferroelectric domains inside BiFeO₃-based capacitors, revealing local disorder in domain architecture and partial polarization reorientation caused by the capacitor electrostatic boundary conditions and internal stress. We demonstrate sensitivity to ferroelectric reversal in poled capacitors, highlighting expansive/compressive (001) strain for up-/down-polarization using nano-XRD. We observe significant quantitative and qualitative differences between poling by piezoresponse force microscopy and in devices. Further, electrical poling induces lattice tilt at electrode edges, which may modify performance in downscaled devices. Our results establish nano-XRD as a noninvasive probe of buried ferroelectric domain morphologies and dynamics, opening avenues for operando characterization of energy-efficient nanoscale devices.