ERBIUM INCORPORATION IN LINBO3 BY DIFFUSION-DOPING

The erbium incorporation into LiNbO3 by diffusion doping is investigat ed in detail by means of Secondary Ion Mass Spectrometry, Secondary Ne utral Mass Spectrometry, Rutherford Backscattering, Atomic Force Micro scopy, X-ray Standing Wave technique and optical site-selective spectr oscopy. The diffusion of erbium in LiNbO3 can be described by Fick's l aws of diffusion with a concentration-independent diffusion coefficien t. The diffusion constants and activation energies for Z-cut (X-cut) L iNbO3 are 4.8 x 10(-5) cm(2)/s (12.0 x 10(-5) cm(2)/s) and 2.28 eV (2. 44 eV), respectively. A limited solubility of erbium in LiNbO3 has to be taken into account increasing exponentially with rising temperature . During the first step of diffusion an ErxNby-oxide layer is formed a t the surface of the sample acting as diffusion reservoir. Erbium is i ncorporated into LiNbO3 on vacant Li-sites slightly shifted from the o riginal Li-position along the (-c)-direction. Site-selective spectrosc opy found four distinguishable energetically different erbium centres at this lattice site resulting from locally different symmetries of th e crystal field.