Probing ferroelectric switching of BaTiO₃ thin films integrated on Silicon

The integration of ferroelectric materials on Si plays an important role in the design of new photonic devices, such as optical switches and modulators. Ferroelectric materials exhibit nonlinear optical properties and in particular their refractive index can be tuned by the application of an E-field via the Pockels effect. Ferroelectric barium titanate (BTO) thin films can be epitaxially grown on silicon, using molecular beam epitaxy (MBE). Controlling the polarization of thin these films in absence of metallic buffer remains non-trivial. Orienting the polar axis beyond the limitation of epitaxy using voltage induced ferroelastic switching events to generate out-of-plane (c-domains) to in-plane polarization (a-domains) rotation would open up new pathways for fabricating photonic devices. In this study, we use transmission optical second harmonic generation (SHG) to study the ferroelastic switching dynamics in our BTO films grown on Si for varying thicknesses. The orientation of the BTO films polar axis and the a/c-domain ratio before and after the application of an external in plane E-field are mapped.