Characterization of Lithium Niobate Thin Films Derived from Aqueous Solution

Abstract

Lithium niobate (LiNbO3, LN) films prepared from aqueous precursor solutions were characterized, in terms of the hydroxyl contents on the surface layers through crystallization and optical properties. Approximately 98% of the hydroxyl residues on the surface layers of crystalline films were polymerized after heat treatment at 350° or 500°C, whereas 50% of the hydroxyl residues remained on the surface layers of amorphous films heat‐treated at 200°C. Highly preferred oriented LN films had a tendency to consist of in‐plane rotation by 60° during nucleation and crystallization. Optical losses (at 632.8 nm) were 2 dB/cm in the TE0 mode and 4 dB/cm in the TM0 mode of the LN films (thickness of 670 nm) on sapphire (001) substrates prepared from a neutralized precursor solution after annealing in oxygen at a temperature of 500°C (where TE and TM are the transverse electric and magnetic modes, respectively).