Nonlinear domain wall velocity in ferroelectric Si-doped HfO2 thin film capacitors

We investigate the nonlinear response of the domain wall velocity (v) to an external electric field (Eext) in ferroelectric Si-doped HfO2 thin film capacitors using piezoresponse force microscopy (PFM) and switching current measurements. We verified the reliability of the PFM images of ferroelectric domain switching by comparing the switched volume fraction in the PFM images with the time-dependent normalized switched polarization from the switching current data. Using consecutive time-dependent PFM images, we measured the velocity of the pure lateral domain wall motion at various Eext. The Eext-dependent v values closely follow the nonlinear dynamic response of elastic objects in a disordered medium. The thermally activated creep and flow regimes were observed based on the magnitude of Eext. With a dynamic exponent of μ = 1, our thin film was found to have random-field defects, which is consistent with the Lorentzian distribution of characteristic switching time that was indicated in the switching current data.