Anomalous polarization inversion in ferroelectrics via scanning force microscopy

Abstract

Local poling of ferroelectrics by the sharp conducting tip of a scanning force microscope(SFM) is studied experimentally and theoretically. The formation of the inverse domainunder the SFM tip, where the polarization is oriented in the direction opposite to that ofthe poling field, is reported for bulk ferroelectrics (single crystals of solid solutionsPbZn1/3Nb2/3O3–PbTiO3). This finding confirms earlier results on ferroelectric thick films, thus proving theuniversality of the anomalous polarization inversion in ferroelectric media. Itis shown that the inverse domain grows with the increase of the poling voltageand duration and remains stable for a long time after the removal of electricfield. The growth process is described by a dynamic model assuming that theappearance of inverse domains is due to a local internal electric field directedagainst the poling one. This field is attributed to the space charge formed beneaththe SFM tip due to injection of charge carriers and their subsequent drift andtrapping. Poling voltage and poling time dependences of the domain size are correctlydescribed by the model. Implications of the anomalous polarization inversion forthe domain engineering and dense data storage in ferroelectrics are discussed.