Secondary switching ratio: an electrical probe of polarization switching evolution in HZO/ZrO2 hybrid bilayers

The ferroelectric-to-antiferroelectric (FE–AFE) crossover in HfO 2 -based capacitors produces multi-step switching responses that cannot be fully described by conventional hysteresis parameters. Here, we introduce the secondary switching ratio, R sec , extracted from transient switching currents, to electrically probe the FE–AFE switching character and its evolution in HZO/ZrO 2 hybrid bilayer capacitors, in which a ferroelectric HZO layer and an antiferroelectric ZrO 2 layer are combined with systematically varied composition and thickness ratios. Importantly, R sec is not interpreted as an absolute orthorhombic/tetragonal phase fraction, but as a functional measure of the relative secondary-switching contribution associated with antiferroelectric-like recovery under a defined pulse protocol. Across the hybrid stack series, R sec evolves systematically from the FE-dominant to the AFE-dominant limit, is qualitatively corroborated by GIXRD signatures, and captures hold-time-, temperature-, cycling-, bias-, and bilayer thickness-ratio-dependent changes in the switching response. Hold-time and delay-time measurements from 83 K to 353 K reveal history-dependent secondary-switching relaxation with a finite low-temperature component, supporting a field-driven contribution with additional thermal assistance at higher temperatures. Temperature-dependent measurements and XPS depth profiling indicate that the wake-up evolution is mainly associated with field-driven switching-state reconfiguration, while oxygen-vacancy redistribution acts as a secondary contributor in the present hybrid bilayer system. This framework establishes R sec as a practical electrical probe for tracking FE–AFE switching evolution in hafnia-based hybrid bilayer capacitors.