Synthesis and properties of ferroelectric niobate thin films prepared by pulsed laser deposition for optical waveguide application

We report the epitaxial growth of strontium barium niobate (Sr_xBa_1-xNb₂O₆), potassium niobate (KNbO₃), and lithium niobate (LiNbO₃) thin films by pulsed laser deposition. From the characteristics of the deposition rate vs. laser fluence, threshold energy for ablation is around 1.5 J/cm². For the oxygen pressure higher than 10^-2 Torr, the deposition rate decreases exponentially with pressure due to the scattering with background gas. Epitaxial films are grown at 725°C for SBN, 675°C for KNbO₃, and 450°C for LiNbO₃, respectively. The ion channeling in Rutherford backscattering spectroscopy indicates the crystalline perfection of the epitaxial layers in SBN film. SBN has two sets of in-plane orientations while KNbO₃, and LiNbO₃ grow in single crystalline form as verified from x-ray φ scan. All films show optical waveguiding in prism coupling measurements.