Light emission from porous silicon is known since several years. Recently, the ability of silicon nanocrystals (NCs) or nanoclusters embedded in a suitable dielectric (usually silicon oxide - SiO2) matrix to efficiently emit photons in the visible spectral region has been demonstrated; potential applications of these nanostructures are in the field of monolithically integrated Si-based photonic devices. Si NCs have been fabricated by a variety of methods, including co-sputtering, chemical vapour deposition, molecular beam epitaxy, gas evaporation, laser ablation, and ion implantation (at ion energies from 100 keV up to a few MeV) followed by high temperature annealing. The latter methodology has the advantage that a controllable dose of ions can be placed at a given depth and distribution into the dielectric medium. High temperature annealing of implanted samples leads to Si atoms precipitation and NC nucleation. In this work we present preliminary results on the synthesis of Si NCs by low (10-40 keV) energy implantation of Si ions into SiO2 films and their subsequent high temperature annealing.