IDENTIFICATION OF PASSIVE LAYER IN FERROELECTRIC THIN-FILMS FROM THEIR SWITCHING PARAMETERS

The switching of the sandwich structure ''ferroelectric+thin dielectri c layer'' is theoretically studied. The behavior of the remanent polar ization, P-r, coercive field, E(c), maximal polarization on the loop, P-s, and the slope of the hysteresis loop at E(c) as a function of bot h, the relative thickness of the layer (the thickness of the dielectri c divided by the thickness of the ferroelectric) and the amplitude of the measuring field, is analyzed. It is shown that the effect of the l ayer on P-r and the slope at E(c) is qualitatively different from that on E(c) and P-s. As the result of this analysis the set of characteri stic features of the sandwich with the variable relative thickness of the dielectric layer have been have formulated. These characteristic f eatures can be used for the identification of the presence of such a d ielectric layer using the data on the switching parameters of the syst em. It is shown that the increase of the coercive field with increasin g relative thickness of the dielectric layer, which was considered as an important sign of the presence of the dielectric layer, is not a re al property of the sandwich structure but rather an artifact of the ap proximations which were used in the analysis performed by the previous workers. In fact, E(c) is a decreasing function of the relative thick ness of the dielectric layer. (C) 1995 American Institute of Physics.