Porous silicon layers with a porosity of 60% on n-type (111)Si substrates were prepared by anodic etching under white illumination. Silver/porous-silicon/Si and metal Ag/Si structures were fabricated by evaporation of thin metal films onto the porous silicon or Si surface, respectively. The diffusion annealing of structures was carried out in air at 100-250C. Examination of the Ag concentration distribution in porous silicon layers and monocrystalline Si substrates was performed by successive removal of thin layers and measurement of the energy dispersive X-ray fluorescence intensity of  AgKα peaks. The effective diffusion coefficients were described by:

D(cm2/s)=42 exp[-0.72(eV)/kT]

Diffusion coefficients of Ag along porous-silicon surfaces were larger (by a factor of 104 to 105) than those into monocrystalline Si.

T.D.Dzhafarov, S.Aydin, D.Oren: Defect and Diffusion Forum, 2006, 258-260, 107-11