Depolarization characteristics of ferroelectric Pb(Zr0.4Ti0.6)O-3 and SrBi2Ta2O9 thin films

We evaluated depolarization characteristics of ferroelectric sol-gel and MOD (Metallo-Organic-Decomposition) Pi-layered SrBi2Ta2O9 thin-film capacitors derived by spin-on techniques with Pt electrodes. The evaluations were carried out for the extended experimental conditions, e.g., pulse height, pulse width, temperature, excess lead. Consequently, we found that the depolarization characteristics depended strongly on the capacitance of load capacitor. The newly obtained hysteresis loop during the pulse response indicates that sufficient field with opposite direction was generated on the ferroelectric capacitor at the moment the read pulse becomes zero. We experimentally found that the mechanism of depolarization is based on depoling (or partial switching) by an opposite-direction field arisen from accumulated switching charge on a load capacitor. This mechanism can be easily extended to the internal depolarization field due to the interfacial linear capacitor between the ferroelectric region and electrode.