Research on the Fabrication of X-Cut Near Stoichiometric Lithium Niobate Wafers

Shanghai OMeda Micro provides X, Y, and Z-cut acoustic and optical grade lithium niobate crystals. It also processes lithium niobate wafers into LNOI thin-film lithium niobate wafers for photonic integrated circuits and surface acoustic wave devices.

Research on the Fabrication of X-Cut Near-Stoichiometric Lithium Niobate Wafers.pdf

This study investigates the fabrication of X-cut near-stoichiometric lithium niobate (NSLN) wafers using the diffusion method. The research focuses on eliminating parasitic microdomains, optimizing the lithium diffusion process, and enhancing the electro-optical properties of NSLN wafers.

Key Findings and Contributions:

1. Fabrication Method

• The diffusion method is employed to introduce lithium ions into congruent lithium niobate (CLN) wafers, creating NSLN.

• Various Li-rich polycrystalline materials with different Li/Nb ratios (58/42, 56/44, 54/46) were synthesized to study their effect on diffusion.

• The optimal diffusion temperature was found to be 1180°C, ensuring high-quality wafers without cracks or twins.

2. Material Characterization

• XRD analysis confirmed the presence of (Li₀.₉₄₁Nb₀.₀₅₉)Nb₀.₉₅₂₈O₃ and Li₃NbO₄ phases in the Li-rich polycrystalline material.

• With increasing lithium content, the lattice parameters a and c decreased, indicating a structural change toward stoichiometry.

3. Microdomain Elimination & Electro-Optical Performance

• A liquid electrode polarization method was designed to eliminate microdomains and achieve a single-domain state.

• The piezoelectric coefficient (d₃₃) increased by 12% compared to CLN, demonstrating improved electro-mechanical properties.

• The coercive field of NSLN wafers was significantly lower than that of CLN, facilitating ferroelectric domain engineering.

4. Physical and Optical Properties

• The Curie temperature of NSLN reached 1198°C, higher than CLN, indicating enhanced thermal stability.

• The UV absorption spectrum of NSLN exhibited a blue shift of 10 nm, making it more suitable for ultraviolet applications.

• The refractive index of NSLN was higher and more uniform than that of CLN, benefiting optical device fabrication.

Conclusion and Applications

This research demonstrates that the diffusion method is a viable approach for fabricating high-quality X-cut NSLN wafers with enhanced electro-optical properties. The improved piezoelectric response, lower coercive field, and superior optical uniformity make NSLN wafers ideal for applications in integrated photonics, electro-optic modulators, and nonlinear optical devices.