Determination of diffusion mechanisms in amorphous silicon

Abstract

We have established experimentally and theoretically that transition metals in amorphous Si undergo direct interstitial diffusion that is retarded by temporary trapping at the defects intrinsic to the amorphous structure. The diffusion of Cu, Zn, Pd, Ag, Pt, and Au has been investigated by means of Rutherford-backscattering spectrometry and that of Au tracer atoms by neutron-activation and sputter-sectioning analysis. The data can be fitted using the foreign-atom interstitial diffusion coefficients in crystalline Si modified due to the presence of traps with concentrations between 0.2 and 1 at.% and trapping enthalpies of about 0.9 eV.