Proton exchange in lithium niobate as an ambipolar diffusion process

Proton exchange rate data from the literature are examined with particular emphasis on finding information about the composition dependence of the interdiffusion rate. In general, these data show that the proton exchange process yields a surface layer which is predominantly depleted of lithium and has protons replacing them on a one-for-one basis. Also, the composition profiles are generally very flat near the free surface, but the concentration changes quite abruptly in the interior of the lithium niobate crystal. These data are examined as the basis for understanding the defect motion and coupling effects in the structure.