  In this work, we investigate the accumulative polarization (P) switching
characteristics of ferroelectric (FE) thin films under the influence of
sequential electric-field pulses. By developing a dynamic phase-field
simulation framework based on time-dependent Landau-Ginzburg model, we analyze
P excitation and relaxation characteristics in FE. In particular, we show that
the domain-wall instability can cause different spontaneous
P-excitation/relaxation behaviors that, in turn, can influence P switching
dynamics for different pulse sequences. By assuming a local and global
distribution of coercive field among the grains of an FE sample, we model the
P-accumulation process in Hf0.4Zr0.6O2 (HZO) and its dependency on applied
electric field and excitation/relaxation time. According to our analysis,
domain-wall motion along with its instability under certain conditions plays a
pivotal role in accumulative P-switching and the corresponding excitation and
relaxation characteristics.
