Abstract Thin films obtained with glasses of the B 2S 3Li 2S and B 2S 3Li 2SLiI systems, using a vacuum evaporation technique have been investigated. In each system, amorphous thin films and starting glasses have the same composition and similar conductivities, about 10 −4 and 10 −3Ω −1cm −1 respectively at 25°C. The deposition rate was in both cases 140 Å s −1. However, a thermal treatment at 90°C of the thin films containing lithium iodide enhances the conductivity by a factor of 10 and leads to lower activation energy (0.18 eV). This behavior has been identified as a Phipps effect and can be attributed to a quick ion diffusion along thin film - substrate interface. This interfacial region was found to show unique conduction properties including a very low Li + migration enthalpy.