Porous silicon layers with a porosity of 60% on n-type (111)Si substrates were prepared by anodic etching under white illumination. Gold/porous-silicon/Si and Au/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 to 250C. Examination of the Au concentration distribution in porous silicon layers and monocrystalline Si substrates was performed by successive removal of thin layers from samples and measurement of the energy dispersive X-ray fluorescence intensity of AuLβ1 peaks. The effective diffusion coefficients were described by:

D(cm2/s)=1.2 x 102 exp[-0.81(eV)/kT]

Diffusion coefficients of Au 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