Growth of Low-Temperature Epitaxial Lithium Niobate Thin Films and Guided-Wave Optical Properties

Abstract

LiNbO3 thin films are grown on a c-plane (0001) sapphire wafer at a relatively low substrate temperature by chemical beam vapor deposition (CBVD) in Sybilla equipment. Raman measurements only evidence the LiNbO3 phase, while HR-XRD diffractograms demonstrate a c-axis-oriented growth with only (006) and (0012) planes measured. The rocking curve is symmetric, with a full width at half maximum (FWHM) of 0.04°. The morphology and topography observed by SEM and AFM show very low roughness, with rms equaling 2.0 nm. The optical properties are investigated by a guided-wave technique using prism coupling. The ordinary refractive index (no) and extraordinary refractive index (ne) at different wavelengths totally match with the LiNbO3 bulk, showing the high microstructural quality of the film. The film composition is estimated by Raman and bi-refringence and shows a congruent or near-stoichiometric LiNbO3.

Keywords

• LiNbO₃
• CBE
• thin film
• photonics
• guided wave