Enhancement of electro-optic response in BaTiO3 films integrated on Si via heating and cooling rate control

作者：Marc Reynaud, Moaz Waqar, Chaojie Du, Agham Posadas, Xiaoqing Pan, Alexander A. Demkov · 发表于：Communications Materials · 年份：2025 · DOI：10.1038/s43246-025-00908-x · 被引用次数：9 · 研究领域：Photonic and Optical Devices、Semiconductor materials and devices、Photorefractive and Nonlinear Optics

Recent advancements in BaTiO3-based Si-integrated photonics devices have shown very large electro-optic responses, allowing for aggressive device scaling in both size and power. However, control of the crystallographic domain structure of high-quality epitaxial BaTiO3 films still remains a challenge. Here, we report on attempts to control the size of crystallographic domains and lattice relaxation profile of 150-nm-thick BaTiO3 films on Si grown by molecular beam epitaxy by varying the heating and cooling rates during the film growth process while maintaining strict epitaxial and stoichiometric control. The film’s crystallographic microstructure is visualized via plan-view transmission electron microscopy to visualize the near surface lattice relaxation and crystallographic domain morphology. By carefully controlling the lattice relaxation evolution, the measured effective electro-optic response reaches values greater than 550 pm/V; it is observed that while the total electro-optic modulation of the films varies with heating/cooling rate, the effective response normalized to a-axis volume fraction does not. Strain relaxation in BaTiO₃ thin films integrated on Si affects electro-optic performance but remains poorly understood, especially in thick films. Here, the heating and cooling rates during molecular beam epitaxy growth are controlled to tune domain structure, achieving <550 pm/V effective Pockels response.