Standard thermal diffusion of Er3+ into X-cut congruent LiNbO3 crystals, with a MgO doping level close to the anti-photorefractive threshold concentration of 4.5mol%, was attempted at temperatures close to Curie point of the crystal. Single-crystal X-ray diffraction, photoluminescence spectroscopy and secondary ion mass spectrometry were used to study the crystalline phase with respect to Er3+ ions and the depth profile of the diffused Er3+ ions. The results showed that the thickness of the Er metal film coating should not be thicker than 4.6nm. In this case, the diffusion was complete, the diffused surface was clean, and the Er3+ ions in the diffused layer retained the LiNbO3 phase. On the other hand, the diffusion was incomplete if the initial thickness of the Er metal film was greater than 4.6nm. The residual Er3+ ions formed ErNbO4 grains on the surface of the crystal. Secondary ion mass spectrometry showed that the diffused Er3+ ions had a mono-exponential decay profile. The experimental results also showed that the diffusivity of Er3+ in X-cut congruent Mg (4.5mol%): LiNbO3 was 4.69 x 10-3μm2/h at 1130C.

Er3+ Diffusion in Congruent LiNbO3 Crystal Doped with 4.5mol%MgO. D.L.Zhang, P.R.Hua, E.Y.B.Pun: Journal of Applied Physics, 2007, 101[11], 113513