H–Li correlation and stoichiometry of mixed phases in proton-exchanged LiNbO3 waveguides

Elastic recoil detection with a time of flight discrimination method using I127 ions has been applied to the simultaneous determination of the H and Li depth profiles as well as of the stoichiometry of the mixed phases formed by thermal annealing in proton-exchanged LiNbO3 waveguides. For both, as-exchanged and annealed waveguides, a one-to-one local correlation between the H and Li profiles has been obtained so that [H]+[Li]=constant. Moreover, the stoichiometry of the HxLi1−xNbO3 compound, where x is the exchange rate, has been correlated with x-ray diffraction (rocking curves) data in order to identify the generated phases after the exchange and annealing processes. In as-exchanged guides, the value x≃0.85 is mainly associated with a broad β2-phase peak. In annealed guides, a well-defined β2-peak is associated with x≃0.5, a broad κ2-peak is associated with x≃0.40, a broad κ1-peak to x≃0.19 and 0.21, and a α-shoulder to x≃0.09 and 0.12.