The ion-beam enhanced diffusion of Au in amorphous samples of undoped or B-doped material was investigated (table 14). It was found that the diffusion coefficients depended linearly upon the ion flux and exhibited an Arrhenius-type temperature dependence, with an activation energy of 0.37eV, at 200 to 350C. The diffusivity was enhanced, by a factor of 5, by B doping to a concentration of 1020/cm3. A similar enhancement of Au thermal diffusion occurred, giving an activation energy of 1.5eV. On the basis of the results, a model for ion-beam enhanced Au diffusion was proposed in which the high density of defects that was present in amorphous material acted as traps for fast-moving interstitial Au atoms. The effectiveness of the trapping process could be changed by the high concentration of mobile defects which was generated by the incident beam and by a change, in the charge state of the traps, which was caused by the presence of B.

Mechanisms of Ion-Beam-Enhanced Diffusion in Amorphous Silicon. S.Coffa, D.C.Jacobson, J.M.Poate, F.Priolo: Applied Physics A, 1992, 54[6], 481-4

Table 14

Thermal and Ion Beam-Induced Diffusivity of Au in B-Doped and Undoped Si