Retention in thin ferroelectric films

Abstract

Rentention of polarization in ferroelectric films is defined asiR = [l-ΔPr/Pr(0)], where ΔPr is the decrease of remanent polarization due to depoling and Pr(0) is the remanent polarization at time zero. Results for measurements of retention as a function of time for films of composition Pb.92Bi.o7La.01(Fe.405Nb.325Z.27)03 are presented. When ferroelectric elements are poled with 10-V, 10-ms pulses, depoling disturb pulses of 0.5 V up to a total of 109pulses do not affect the retention. Retention is found to be a function of the heat treatment of the films and the electrodes. It decreases as temperature increases and decreases as the amount of charge initially switched becomes smaller. Also, definite improvement in retention is observed when a high series resistance is placed in the circuit.