Silicon nucleation process was investigated in molten NaF-KF (40-60 mol%) on silver electrodes in the 820-950 degrees C temperature range in order to optimize silicon coating operating conditions. Chronoamperometric measurements evidenced that silicon electrodeposition process involved an instantaneous nucleation with diffusion-controlled nuclei growth whatever temperature and Si(IV) ions concentration in the mixture. The overpotential and temperature influence on nucleation sites number was also studied. Silicon deposits were obtained using the same temperature range as nucleation study, for different current densities on substrates: Ni, Ag, C-graphite and C-vitreous. A sensitive influence of the cathodic substrate on the deposit adherence and roughness was observed and discussed. (C) 2011 Elsevier Ltd. All rights reserved.