Under Li-poor atmosphere, local Er3+ diffusion into highly MgO-doped LiNbO3 (LN) crystal was investigated. Three Z-cut 5mol% (in growth melt) MgO-doped LN substrates locally coated with 44 to 60nm thick Er-metal films underwent the respective Li-poor vapour transport equilibration (VTE) treatment at 1060, 1100, and 1130C for the same 90h duration. After the VTE, the reductions of Li2O content at the Er-free and Er3+-doped parts of the surface of the three samples, determined from the measured birefringence, have a similar value of 1.0, 2.0 and 2.3mol%, respectively. Secondary ion mass spectrometry was used to study the Er3+ diffusion properties and the VTE effect on the Mg2+ profile. From the measured Er3+ profiles, characteristic diffusion parameters such as 1/e diffusion depth, diffusivity, diffusion constant, activation energy, surface concentration, solubility, solubility constant, and heat of solution were determined. A comparison with the related results previously reported allows to conclude that heavy MgO-doping results in substantial decrease of both the diffusivity and solubility, and under the same diffusion temperature the diffusivity and solubility increase by as much as one order of magnitude and two times, respectively, as the diffusion atmosphere goes from the traditional argon to the Li-poor atmosphere. The Mg2+ profiles reveal that the VTE may induce MgO diffusion and hence an inhomogeneous profile in the Er3+-diffused layer. This undesired effect was strong for the 1130C VTE temperature whereas was relatively much weak for 1060C. It was tentatively explained in terms of the Er3+ diffusion and Li-poor VTE mechanisms.

Er3+ Diffusion into MgO (5 mol%)-Doped LiNbO3 Crystal Under Li-Poor Atmosphere. D.L.Zhang, S.Y.Xu, P.R.Hua, D.Y.Yu, E.Y.B.Pun: Journal of the American Ceramic Society, 2012, 95[4], 1398-405