Chemical design of barium titanate thin films for nanophotonic devices

High-performance electro-optic (EO) materials greatly enhance modulators and switches in various photonic applications. We investigate the evolution of the tolerance factor (t) and EO coefficient (rc) in A-site and B-site doped BaTiO3 (BT) thin films. Our analysis reveals that cation transmutation has a remarkable impact on their dielectric constant, spontaneous polarization, optical band gap, and EO coefficient. Notably, Pb-doped BT samples exhibit an even higher rc value of 336.5 pm/V, representing a nearly 60% increase compared to pure BT and approximately 11 times larger than that of LiNbO3. This substantial improvement in EO performance can be attributed to enhanced local structural heterogeneity resulting from cation dopants. Furthermore, infusing dopants in BT also result in good structural uniformity and reliable EO performances, regardless of temperature and frequency. Our study offers valuable insights into doping engineering for obtaining functional perovskite oxides, enabling the development of power-efficient, ultra-compact integrated nanophotonic devices.