Modeling of anomalous shift and asymmetric hysteresis behavior of ferroelectric thin films

Abstract

An analytical bilayer model has been developed to consider the effect of the existence of a dead layer (e.g., due to polarization degradation) at the film-electrode interface in an otherwise homogeneous ferroelectric thin film. By introducing asymmetric conductivity in the dead layer, the anomalous horizontal (along the field axis) shift behavior of hysteresis loops in ferroelectric thin films is successfully reproduced. Assuming that the ferroelectric P-E hysteresis loops of the layers are parallelogramlike, explicit expressions are derived for calculating the internal fields in the film, as well as the “apparent” D-E loop as measured from a Sawyer-Tower circuit. The general switching sequence for the ferroelectric phases will be considered. Using the ferroelectric-ferroelectric bilayer model, other anomalous phenomena, including vertical shift and deformed loop shape are also modeled.