Abnormal switching of ferroelectric domains created by the tip of an atomic force microscope in a congruent LiTaO3 single-crystal thin film

Ferroelectric domains have been created in single-crystal ∼1 μm thick LiTaO3 films using the tip of an atomic force microscope. The presence of a domain with a polarization that is oriented in the opposite direction as compared to the applied field in the center of the domains created by the tip is reported. This paper aims at better understanding this phenomenon. Domains with a polarization oriented toward the bulk do not behave like domains with a polarization oriented toward the surface. The evolution of the size of the abnormal domain as a function of the parameters of the applied voltages and exerted forces is studied using a technique derived from the atomic force microscope (piezoresponse force microscopy), and its kinetics of formation is recorded by means of time resolved piezoresponse force microscopy. The possible causes for its appearance are discussed. The ferroelastic effect does not seem to play a role in the process. A possible artifact from the atomic force microscopy imaging process itself is not relevant. It appears that the most probable mechanism responsible for this phenomenon is the injection of charges during the application of the voltage pulse, which creates a strong electric field when the voltage is removed. The experimental observations are discussed in light of this hypothesis.