A systematic study of the mechanisms which govern the in-depth migration of Ag ions in glasses, in presence of an external field, has been performed, with the aim to create buried waveguides. Ag films, from 60 to 240nm thick, were evaporated on the surface of glasses of different composition. Electric fields ranging from 300 to 1000 V/cm, were applied across the glasses for different times and temperatures. The Ag distribution and glass composition modifications were analyzed using nuclear techniques, as RBS and NRA. Stresses induced by the process were investigated using mechanical microindentation techniques. A comparison between theoretical and experimental profiles has been performed and the importance of the different parameters (electric field, glass temperature, Ag surface layer thickness, process duration) was enlighted.