We present an original technique for growing large fullerene onions : carbon-ion implantation at high temperature into copper substrates. Used for carbon film growth (diamond or turbostratic carbon), this method is based on the immiscibility of carbon into copper and can produce an important density of giant carbon onions with size up to some micrometres which is the largest size observed up to now. We characterize these giant fullerenes by TEM, HRTEM and for the fi rst time with AFM. On the basis of both experimental and numerical results we propose a mechanism of formation of the carbon onions during the implantation process.