Influence of stress on the domain formation in barium-titanate films

A scanning force microscope (SFM) is used for both the switching of spontaneous polarization and for imaging of the resulting domain distribution on a sub-micron scale in barium-titanate thin films. During the switching process not only an electric field but also a compressive stress is applied to the sample and its influence on the resulting polarization is studied. Our measurements reveal the expected hysteresis loop only for low stresses. For high applied stresses the direction of polarization after poling is antiparallel to the expected one. We interpret this behaviour in terms of a simple theory based on free energy minimization.