A strong electro-optically active lead-free ferroelectric integrated on silicon.

Area of Science:

• Materials Science
• Photonics
• Solid State Physics

Background:

• Silicon photonics lacks linear electro-optical properties essential for integrated devices.
• Ferroelectric oxides offer potential solutions for electro-optical modulation.
• Barium titanate is a promising oxide with large electro-optical coefficients, but its thin films on silicon remain unexplored.

Purpose of the Study:

• To investigate the electro-optical properties of thin barium titanate films epitaxially grown on silicon.
• To demonstrate the potential of barium titanate thin films for silicon photonics applications.
• To characterize the ferroelectric and electro-optical tensor properties of these films.

Main Methods:

• Epitaxial growth of barium titanate thin films on silicon substrates.
• Characterization of electro-optical properties using the Pockels effect measurement.
• Demonstration of ferroelectricity in the grown thin films.

Main Results:

• A large effective Pockels coefficient (r(eff) = 148 pm V(-1)) was extracted, five times larger than lithium niobate.
• The tensor nature of the electro-optical properties was revealed, crucial for device design.
• Unambiguous demonstration of ferroelectricity in barium titanate thin films on silicon.

Conclusions:

• Thin barium titanate films exhibit significant electro-optical properties on silicon substrates.
• This integration paves the way for power-efficient, ultra-compact silicon photonic devices.
• Potential applications include modulators, tuning elements, and bistable switches.