A systematic investigation on the influence of the diffusion parameters (time and temperature) and initial titanium film thickness on the spectral characteristics of the LiNbO 3 Raman modes is reported. Raman spectra are measured in the range 50-1000 cm À1 $2 mm below the surface of the crystals. Broadening of the Raman lines and, therefore, crystal lattice disorder induced by the titanium ions are found to depend on the fabrication parameters. The disorder associated with the titanium ions

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... the surface of LiNbO 3 is encoded in the broadening of the A 1 (TO 1 ) Raman line. A linear relation between the A 1 (TO 1 ) mode broadening and the Ti concentration is presented. The diffusion theory is used to explain the experimental data. Raman spectroscopy combined with diffusion theory can be used to estimate the evolution of the titanium surface concentration.