Dynamics of ferroelastic domains in ferroelectric thin films

Dynamics of domain interfaces in a broad range of functional thin-film materials is an area of great current interest. In ferroelectric thin films, a significantly enhanced piezoelectric response should be observed if non-180° domain walls were to switch under electric field excitation. However, in continuous thin films they are clamped by the substrate, and therefore their contribution to the piezoelectric response is limited. In this paper we show that when the ferroelectric layer is patterned into discrete islands using a focused ion beam, the clamping effect is significantly reduced, thereby facilitating the movement of ferroelastic walls. Piezo-response scanning force microscopy images of such islands in PbZr0.2Ti 0.8O3 thin films clearly point out that the 90° domain walls can move. Capacitors 1 μm2 show a doubling of the remanent polarization at voltages higher than ∼15 V, associated with 90° domain switching, coupled with a d33 piezoelectric coefficient of ∼250 pm V-1 at remanence, which is approximately three times the predicted value of 87 pm V-1 for a single domain single crystal.