Synchronous Polarization Switching at Sub‐Coercive Fields through Stochastic Resonance in Ferroelectric Thin‐Film Capacitors

Stochastic resonance (SR) is a phenomenon by which the presence of noise in a non-linear system allows for detection of a weak sub-threshold signal, or in a bi-stable system allows for sub-coercive switching between the two states. Simple theory suggests that SR occurs when the Kramers rate (r_k) of the bistable system, which is a function of noise and applied voltage, is twice the drive frequency (f_signal). Here, we demonstrate the synchronous switching of polarization with a sub-coercive voltage waveform in a thin-film ferroelectric lead zirconium titanate (PZT) capacitor through SR. We employ independent figures of merit (FOM) such as cross-covariance, output power, and signal-to-noise ratio to experimentally identify the optimal noise for synchronous switching. We further experimentally measure the Kramers time in the ferroelectric and verify that FOMs indeed peak near the noise predicted by the SR condition T_signal = 2τ_k. We also model the device characteristics using the stochastic Time Dependent Landau-Khalatnikov (TDLK) formulation and capture the experimentally observed polarization switching under application of sub-coercive voltage, assisted by noise. Finally, we show a proof-of-concept implementation of detecting sub-threshold frequency-shift-key signals (FSK) in noisy communication channels using our ferroelectric PZT devices.