Spalled Barium Titanate Single Crystal Thin Films for Functional Device Applications
Creators
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1.
California Institute of Technology
Abstract
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.
Acknowledgement
This work was supported by the Air Force Office of Scientific Research Meta-Imaging MURI Grant No. FA9550-21-1-0312 (P.T., M.T., J.B., H.A.A.) and Caltech Space Solar Power Project (A.W.N., P.R.J.). P.T. acknowledges support from Meta Platforms, Inc., through the Ph.D. fellowship C-834952. J.B. acknowledges the support of the Natural Sciences and Engineering Research Council of Canada (NSERC) through the Postgraduate Scholarship–Doctoral program. We further thank Samuel K. W. Seah and Kyle Hunady for insightful discussions regarding thin film transfer and John Hylak for support with XRD measurements.
Copyright and License
Copyright © 2025 American Chemical Society
Supplemental Material
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.nanolett.5c02279.
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Refractive index and electro-optic coefficient r42 for BTO, XRD scans for bulk substrates and spalled film, reusability of single-crystal BTO substrates through repolishing, nonuniformities in Ni plating thickness, thickness and roughness variability for (100) oriented spalls, surface quality of (100) and (001)-oriented bulk crystals, electro-optic characterization of bulk BTO substrate, measurement procedure for characterization of r42, optical losses in spalled BTO films, and bandwidth of modulation signal (PDF)
Data Availability
The data that support the findings of this study are available from the corresponding author upon reasonable request.
Contributions
P.T. and H.A.A. conceived the original idea for this project. P.T. and A.W.N. performed spalls and thin film characterization, with inputs from P.R.J.. P.T. developed the thin film transfer technique together with J.B.. P.T. prepared samples for electro-optic testing. M.T. built the Teng-Man setup. P.T. and M.T. and performed the corresponding measurements. All authors contributed to writing the manuscript.
Conflict of Interest
The authors declare no competing financial interest.
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Additional details
Identifiers
- PMID
- 40591445
Related works
- Is new version of
- Discussion Paper: arXiv:2505.04045 (arXiv)
Funding
- Meta (United States)
- C-834952
- United States Air Force Office of Scientific Research
- Meta-Imaging MURI Grant FA9550-21-1-0312
- Natural Sciences and Engineering Research Council
- California Institute of Technology
- Space Solar Power Project
Dates
- Accepted
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2025-06-11Accepted
- Available
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2025-07-01Available online