Diffusion of Au in Amorphous Si During Ion-Beam Irradiation.

We have measured the radiation-enhanced diffusion of Au in amorphous Si in the temperature range 77-700 K. Gold was implanted to depths of 500angstroms at concentrations of an atomic %. The samples were than amorphized to depths of ~2microns using MeV Ar implants at liquid nitrogen temperature. Radiation- enhanced diffusion was induced by a 2.5 MeV Ar beam at doses of 2x10 sup (16) -2x10 sup (17) /cm sup 2 and dose rates of 7x10 sup (12) -7x10 sup (13) /cm sup 2 sec. The diffusion coefficients show three well defined regions. At temperatures 400K diffusion is essentially athermal and due to ballistic mixing. At temperature between 400K and 700K the diffusion, which is considerably enhanced over the usual thermal values, has an Arrhenius behavior with an activation energy of 0.37 eV. At higher temperatures thermal diffusion, with an activation energy of 1.42 eV, dominates.