Ferroelectric Domain Breakdown

A new phenomenon—ferroelectric domain breakdown, or the formation of string-like domains—is observed in various bulk ferroelectric crystals under a high inhomogeneous electric field generated at the tip of a high-voltage atomic force microscope. The domains have a high aspect ratio when their length exceeds their lateral size by two or three orders of magnitude. This chapter reviews some of the recent advances in understanding the nature of this phenomenon. The main driving force for ferroelectric domain breakdown is not the tip's electric field, which is negligibly weak near the apex of the long domain, but rather internal forces generated owing to the minimization of depolarization field energy when the domain elongates. Domain breakdown is considered an extreme manifestation of Coulomb instability, which is caused by repulsion of bound charges near the inverted domain apex. This instability leads to strong pulling of the domain apex into a region where the tip-induced electric field is negligibly small.