The incorporation of Er by diffusion doping was investigated by means of secondary ion mass spectrometry, secondary neutral mass spectrometry, Rutherford back-scattering, atomic force microscopy, X-ray standing wave techniques and optical site-selective spectroscopy. It was found that the diffusion of Er could be described by Fick’s law, with a concentration-independent diffusion coefficient. The diffusion constants for Z-cut and X-cut samples were 4.8 x 10-5 and 1.2 x 10-4cm2/s. The corresponding activation energies were 2.28 and 2.44eV. A limited Er solubility, which increased exponentially with increasing temperature, had to be taken into account. During the first stages of diffusion, an (Er,Nb)-oxide layer formed at the sample surface and acted as a diffusion reservoir. It was noted that the Er was incorporated at vacant Li sites which were slightly shifted from the original Li position along the c-direction. The use of site-selective spectroscopy revealed 4 energetically different Er centers, at such lattice sites, which resulted from locally different symmetries of the crystal field.

I.Baumann, R.Brinkmann, M.Dinand, W.Sohler, L.Beckers, C.Buchal, M.Fleuster, H.Holzbrecher, H.Paulus, K.H.Müller, T.Gog, G.Materlik, O.Witte, H.Stolz, W.Von der Osten: Applied Physics A, 1997, 64[1], 33-44