AEM Solid Mechanics Seminar: Kalpesh Jaykar

Modeling Mechanical Instabilities in Epitaxial Barium Titanate Thin Films

Ferroelectric BaTiO₃ (BTO) thin films are promising for electronic and photonic applications. Using Hybrid Molecular Beam Epitaxy (Hybrid MBE), high-quality epitaxial BTO films can be grown with unit-cell-level thickness control. Their behavior, however, is strongly influenced by epitaxial strain and mechanical boundary conditions arising from integration with dissimilar substrates.

In this seminar, I will present continuum theories developed to understand two distinct mechanical instabilities in epitaxial BTO thin films. In the first system, BTO films grown on a sacrificial SrO layer spontaneously roll upon release. A model incorporating polarization effects predicts the characteristic rolled-film diameter as a function of thickness and shows good agreement with experimental observations. In the second system, BTO films grown on CaSnO₃/SiO₂ substrates develop wrinkling patterns. Modeling the film as an orthotropic hyperelastic medium yields analytical predictions for wrinkle orientation and slope that are consistent with experimental measurements. Together, these results demonstrate how energy-minimization principles can be used to explain and predict some rolling and wrinkling instabilities in ferroelectric thin films, providing a framework for the design and control of ferroelectric heterostructures.