  Pulse-based studies of ferroelectric capacitor systems have been used by
several groups to experimentally probe the mechanisms of apparent negative
capacitance. In this paper, the behavior of such systems is modeled through
SPICE simulation with a delayed-response Preisach model, and the results are
compared to available data. It is found that a simple ferroelectric domain
delay model can explain much of the observed behavior, capturing the
qualitatively different effects of bipolar and unipolar switching, as well as
the voltage dependence of said switching. The observed behavior and its
modeling suggests that the observed negative capacitance is in fact associated
with ferroelectric switching, and its presence is highly sensitive to the
switching frequency and other details of the ferroelectric system.
