Spalled Barium Titanate Single Crystal Thin Films for Functional Device Applications

We report a scalable approach for fabricating single-crystal barium titanate (BTO) thin films through spalling from bulk substrates. Conventional thin film growth techniques often face challenges in achieving high-quality single crystal microstructure over large areas, resulting in reduced performance in functional devices. In contrast, spalling, i.e., performing stress-induced exfoliation of bulk single crystals, enables the separation of single crystal thin films with controllable thicknesses ranging from 100 nm to 15 μm and lateral dimensions up to several millimeters. Electro-optic characterization of the spalled films yields a Pockels coefficient of r₃₃ = 55 pm/V in multidomain regions and 160 pm/V in single-domain regions, leading to projections up to 1980 pm/V for r₄₂ under conditions of unclamped excitation. Our results indicate that spalled BTO single-crystal thin films preserve bulk electro-optic properties and exceed the performance of commercially available thin film lithium niobate, making them suitable for integration in advanced photonic and optoelectronic devices.