Diffusion characteristics of Zr ⁴⁺ in LiNbO ₃ single-crystal

Diffusion characteristics of Zr⁴⁺ in LiNbO₃ single-crystal were studied. Zr⁴⁺-doped LiNbO₃ crystal plates were prepared by in-diffusion of 100 nm thick ZrO₂ film coated onto Z-cut congruent substrates in wet O₂ at different temperatures. Zr⁴⁺-diffused profile was analyzed by secondary ion mass spectrometry. The results show that the Zr⁴⁺ diffusion follows the traditional diffusion theory. From the measured profiles, important diffusion parameters are obtained, such as diffusivity and its temperature dependence, diffusion constant, activation energy, surface concentration, and solubility. The Zr⁴⁺ has a diffusivity similar to that of Ti⁴⁺, implying that the Zr⁴⁺ doping and the Ti⁴⁺ diffusion can be performed simultaneously to simplify the fabrication process of a photorefractive-damage-resistant Zr⁴⁺-doped Ti-diffused LiNbO ₃ waveguide.