Structural and Optical Properties of Crystal Ion Sliced BaTiO$_3$ Thin Films

TL;DR

This study demonstrates that thermal annealing effectively restores the structural and optical properties of crystal ion sliced BaTiO$_3$ thin films, making them suitable for integrated photonics applications.

Contribution

It introduces a post-slicing thermal annealing process that recovers the crystallinity and nonlinear optical properties of CIS-processed BaTiO$_3$ films, enabling scalable photonic device fabrication.

Findings

Raman spectroscopy confirms crystallinity recovery after annealing.

SHG microscopy shows reorientation of ferroelectric domains and nonlinear susceptibility restoration.

Optical dispersion of annealed films matches bulk BaTiO$_3$, suitable for photonics.

Abstract

Barium titanate (BaTiO$_3$) is a compelling material for integrated photonics due to its strong electro-optic and second-order nonlinear properties. Crystal Ion Slicing (CIS) presents a scalable and CMOS-compatible route for fabricating thin BaTiO$_3$ films; however, ion implantation during CIS introduces lattice damage that can degrade structural and optical performance. In this study, we demonstrate that post-slicing thermal annealing effectively restores the structural integrity and optical quality of CIS-processed BaTiO$_3$ flakes. Raman spectroscopy confirms the recovery of crystallinity, while second-harmonic generation (SHG) microscopy reveals systematic reorientation of ferroelectric domains and restoration of the associated second-order nonlinear susceptibility tensor $X^{(2)}$. Notably, SHG signals persist even in regions with weak Raman signatures, indicating that long-range ferroelectric order can survive despite partial lattice disruption. Optical measurements show that the linear dispersion of annealed CIS flakes closely matches that of bulk BaTiO$_3$, validating their suitability for photonic integration. Together, these results qualify CIS - combined with thermal annealing - as a viable and scalable manufacturing strategy for high-quality BaTiO$_3$-on-insulator (BTOI) platforms, enabling advanced integrated photonic devices for modulation, frequency conversion, and quantum optics.