An investigation was made of the effect of the pre-amorphization damage on the structural properties, and dopant diffusion behavior of In and C co-implanted layers in Si. Ion implantation of In and C in Si was used to produce co-implanted specimens. Rutherford Backscattering Spectroscopy and Secondary Ion Mass Spectroscopy were performed on as-implanted and annealed samples to assess in detail the structural properties of the doped layers and the diffusion behavior. The results were compared with data obtained for similar implants performed into crystalline Si to achieve a deeper understanding of the mechanisms driving the diffusion of the In in Si in presence of co-implanted species. In particular a reduction of the In diffusion and a saturation level for the In substitutional retained dose were observed.An investigation was made of the effect of the pre-amorphization damage on the structural properties, and dopant diffusion behavior of In and C co-implanted layers in Si. Ion implantation of In and C in Si was used to produce co-implanted specimens. Rutherford Backscattering Spectroscopy and Secondary Ion Mass Spectroscopy were performed on as-implanted and annealed samples to assess in detail the structural properties of the doped layers and the diffusion behavior. The results were compared with data obtained for similar implants performed into crystalline Si to achieve a deeper understanding of the mechanisms driving the diffusion of the In in Si in presence of co-implanted species. In particular a reduction of the In diffusion and a saturation level for the In substitutional retained dose were observed.