Effect of Stoichiometry on The Atomic Microsctructure of Thin Film BaTiO₃

Synthesis and characterization of thin film barium titanate is of great interest due to its promise for use in electro-optic modulators [1]. These devices require a thin film with a high electro-optic coefficient that can operate at low voltages and integrate into photonic circuits, so barium titanate’s strong nonlinearity makes it an attractive candidate material. Barium titanate’s ferroelectricity means that it is also of interest for applications in nonvolatile ferroelectric memories. For use in photonic devices, we must understand how variations in film stoichiometry affect the electro-optic properties, local atomic structure, and ferroelectric structure of thin film barium titanate. We use molecular beam epitaxy (MBE) to grow high quality thin films of barium titanate with a high degree of stoichiometry control. In this talk, we use high-resolution scanning transmission electron microscopy (STEM) to compare the atomic microstructure of barium titanate films of varying stoichiometries grown on strontium titanate. High-resolution electron microscopy imaging allows us to evaluate atomic-level variations in crystal structure, local defects, and electrical polarization in thin films of barium titanate. By understanding the effect of stoichiometry on these variations, we can understand the degree of stoichiometry control needed to grow barium titanate thin films that are of sufficient quality for electro-optic device applications.<br/><br/>* Supported in part by the NSF STC for Integrated Quantum Materials DMR-1231319, and the NSF Nanotechnology Nanotechnology Coordinated Infrastructure ECCS-1541959.<br/><br/>[1] D. Zhu et al., Integrated Photonics on Thin-Film Lithium Niobate, Adv. Opt. Photon. 13, 242 (2021).