Spalled barium titanate single crystal thin films for functional device applications

TL;DR

This paper introduces a scalable spalling method to produce high-quality single-crystal barium titanate thin films with superior electro-optic properties, suitable for advanced photonic devices.

Contribution

The study presents a novel, scalable spalling technique for fabricating high-quality BTO single-crystal thin films with preserved bulk properties and enhanced electro-optic performance.

Findings

Spalled BTO films range from 100 nm to 15 μm in thickness.

Electro-optic coefficients significantly exceed those of commercial thin-film lithium niobate.

Films maintain bulk electro-optic properties and are suitable for photonic applications.

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 um and lateral dimensions up to several millimeters. Electro-optic characterization of the spalled films yields a Pockels coefficient of r33 = 55 pm/V in multi-domain 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.