Exploring polarisation switching and imprint in fatigued Pt-PZT-Pt FECAPs by atomic force microscopy

Switching and imprint effects as a function of fatigue in Pt-PZT-Pt ferroelectric capacitors (FeCap) were studied by means of Atomic Force Microscopy (AFM). This approach enable the local characterisation of the ferroelectric properties. It is found that although fatigue appears to occur, as expected, "region by region" and shows a preferential direction for the polarisation, the dead areas can consist of an unequal quantity of very small frozen regions oriented in both directions. This coexistence gives rise to regions with different piezoelectric activity and degree of fatigue. The surviving areas also contain a minority of small frozen regions which manifest itself by shifting the piezoelectric loops along the y-axis. In addition it was shown that although fatigue onset can influence the imprinted state by centring the typical field offset, imprint treatment in opposite directions cannot influence the completed fatigued state (size, shape and preferred orientation of the frozen regions).