Charge compensation model for the lateral expansion of ferroelectric domains inverted by force-microscope tips

Abstract

The advent of scanning force microscopy (SFM) and the discovery of domain wall (DW) conduction have revolutionized the area of ferroelectric domain reversal and transferred it to the nano-scale with promises for nano-electronic and nano-scale reversible memory devices. Numerous experiments with application of voltage pulses to SFM tips show a fast local forward growth of inverted domains followed by their strong lateral expansion. Most of the explanations of the lateral expansion ignore the charge compensation of arising bound polarization charges; they are physically untenable. We propose a simple self-consistent quantitative model for the lateral expansion accounting for the necessary charge compensation via the DW conduction. This model involves injection of the compensating charge carriers from the tip. It possesses remarkable flexibility, is in good agreement with the experimental data for lithium niobate crystals, and predicts new features of the domain reversal.