Strain-Engineered Ferroelastic Structures in PbTiO₃ Films and Their Control by Electric Fields

We study the interplay between epitaxial strain, film thickness, and electric field in the creation, modification, and design of distinct ferroelastic structures in PbTiO₃ thin films. Strain and thickness greatly affect the structures formed, providing a two-variable parameterization of the resulting self-assembly. Under applied electric fields, these strain-engineered ferroelastic structures are highly malleable, especially when a/c and a₁/a₂ superdomains coexist. To reconfigure the ferroelastic structures and achieve self-assembled nanoscale-ordered morphologies, pure ferroelectric switching of individual c-domains within the a/c superdomains is essential. The stability, however, of the electrically written ferroelastic structures is in most cases ephemeral; the speed of the relaxation process depends sensitively on strain and thickness. Only under low tensile strain - as is the case for PbTiO₃ on GdScO₃ - and below a critical thickness do the electrically created a/c superdomain structures become stable for days or longer, making them relevant for reconfigurable nanoscale electronics or nonvolatile electromechanical applications.