DC-VOLTAGE AND CYCLING INDUCED RECOVERY OF SWITCHED POLARIZATION IN FATIGUED FERROELECTRIC THIN-FILMS

We report results on electric DC-field induced and self induced recove ry of the switched remanent polarisation (P-r(s)) in fatigued ferroele ctric thin films. The field induced recovery is characterised by a str ong asymmetry and depends on the ratio between the fatiguing and DC-fi eld magnitudes. It is also dependent on the period of application of t he DC-field. The self recovery effect occurs on further cycling beyond the fatigued state. It is dependent on the fatiguing field magnitude and also, if the cycling is performed with a square wave function, on the switching frequency. For both effects we propose a tentative expla nation based on the pinning of ferroelectric domain walls by negativel y charged defects close to the top electrode and on the annihilation o f those defects by positively charged defects, the nature of which rem ains to be disclosed.