Characterization of (Ti0.65Nb0.35)O2 compound as a source for Ti diffusion during Ti:LiNbO3 optical waveguides fabrication

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Abstract
During Ti:LiNbO3 integrated optical waveguide fabrication the (Ti0.65Nb0.35)O2 forms at temperatures ranging from 700 to 950 °C, after the Ti oxidation which occurs owing to Ti reaction with oxygen atoms of the surrounding atmosphere and/or of LiNbO3 substrates. The (Ti0.65Nb0.35)O2 compound has been characterized using scanning electron microscopy, secondary ion mass spectrometry, Auger electron spectroscopy, Rutherford backscattering in channeling conditions, and x‐ray diffraction. Results show that the (Ti0.65Nb0.35)O2 phase grows epitaxially on both Z‐ and Y‐cut substrates, the quality depending on both annealing atmosphere and film thickness. The film behaves as a real source for Ti diffusion and consequently is consumed at increasing annealing temperatures and/or times. We did not observe Li‐Ti‐O compounds, although a small amount of Li was detected in the surface layer.