FATIGUED STATE OF THE PT-PZT-PT SYSTEM

The fatigued state of Pt-PZT-Pt ferroelectric capacitors (FECAP) was i nvestigated by means of piezoelectric coefficient, polarisation charge and permittivity measurements. The suppression of switching polarisat ion P-r(s) appears to be the result of freezing of ferroelectric domai ns without affecting the lattice dielectric properties. The frozen pol arised domains show a preferential orientation which is related td the electrode interface asymmetry. The fatigue mechanism in thin films is not assisted by a growing passive layer and is characterised by a sub stantial reversible character and adaptation to the used fatiguing fie ld (field self-adjusting). With consideration of the frozen asymmetry and of the newly discovered slow cycling fatiguing effect in thicker s amples, the fatigue mechanism was interpreted as inhibition of the nuc leation at the top electrode interface. Since it is unlikely that the domain wails (DW) cross the grain boundaries, it is suggested that the effective suppression of P-r(s) occurs grain by grain and corresponds to the creation of ''ferroelectrically dead areas''.