Concentration profiles in (001) monocrystals were measured by means of Rutherford back-scattering spectroscopy. It was found that the diffusion data which were deduced from the profiles could be described by:

Er:      D (cm2/s) = 3.6 x 10-16exp[-6.4(eV)/kT]

Nb:      D (cm2/s) = 1.2 x 10-14exp[-3.8(eV)/kT]

Nd:      D (cm2/s) = 1.3 x 10-11exp[-5.3(eV)/kT]

M.J.Martin, C.Zaldo, M.F.Da Silva, J.C.Soares, F.Diaz, M.Aguilo: Journal of Physics - Condensed Matter, 1997, 9[34], L465-9