Piezoelectric response enhancement in the proximity of grain boundaries of relaxor-ferroelectric thin films

摘要

The influence of surface morphology on the local piezoelectric response of highly (100)-textured 0.70PbMg_(2/3)Nb_(1/3)O_3-0.30PbTiO_3 thin films is studied using piezoresponse force microscopy in band-excitation mode. The local electromechanical response is mostly suppressed in direct proximity of the grain boundaries. However, within 100-200 nm of the grain boundary, the piezoresponse is substantially enhanced, before decaying again within a region at the center of the grain itself. Nested piezoresponse hysteresis curves confirm the influence of topography descriptors on parameters affecting the hysteresis loop shape. The enhancement of the electromechanical response is rationalized through reduced lateral clamping in the grains with deep trenched boundaries, as well as an expected lower energy for complex domain wall structures, due to curved ferroelectric surfaces. The lower piezoresponse at the center of the grain is assigned to the lateral clamping by the surrounding piezoelectric material.