In ferroelectric thin films, the complex interplay between mechanical and electrostatic boundary conditions allows for the formation of a large variety of domain structures with fascinating properties. These domain structures not only change the properties of the ferroelectric itself, but can also be used to change the properties of other materials through electrostatic and structural coupling.

In this work, we study the complex ferroelastic/ferroelectric domain structure in the prototypical ferroelectric PbTiO₃. We investigate epitaxially strained structures grown on (110)_o-oriented DyScO₃ substrates, using a combination of atomic force microscopy, laboratory and synchrotron x-ray diffraction and high resolution scanning transmission electron microscopy. We observe that the anisotropic strain imposed by the orthorhombic substrate creates a large asymmetry in the domain configuration, with domain walls macroscopically aligned along one of the two in-plane directions. We show that the periodicity as a function of film thickness deviates from the Kittel law. As the ferroelectric film thickness increases, we find that the domain configuration evolves from flux-closure to a/c-phase, with a larger scale arrangement of domains into superdomains.

Above a certain critical thickness, the large structural distortions associated with the ferroelastic domains propagate through the top SrRuO₃ layer, creating a modulated structure that extends beyond the ferroelectric layer thickness, leading to nanoscale domain engineering in SrRuO₃ thin films.

Mapping the complex evolution of ferroelastic/ferroelectric domain patterns in epitaxially strained PbTiO₃ heterostructures. Lichtensteiger, Hadjimichael, Zatterin, Su, Gaponenko, Tovaglieri, Paruch, Gloter, & Triscone (2023). APL Materials, 11(061126).

Nanoscale domain engineering in SrRuO₃ thin films. Lichtensteiger, Su, Gaponenko, Hadjimichael, Tovaglieri, Paruch, Gloter, & Triscone (2023). APL Materials, 11(101110).