Gold Penetration Correlated with Selective Oxidation of Silicon in Fe-3 mass%Si Single Crystal

Secondary ion mass spectrometry (SIMS) has been used for characterizing penetration of gold, which was deposited on the surface of Fe-3 mass%Si (011) single crystal and subsequently penetrated into its bulk by annealing under the low partial pressure of oxygen. The degree of gold penetration was evaluated using an effective diffusion coefficient of gold in Fe-3 mass%Si, which was apparently estimated from a SIMS depth profile. The effective diffusion coefficients of gold in the surface layer of Fe-3 mass%Si were found to be larger than those in the bulk iron. The gold penetration is likely to be correlated with the distribution of silicon oxides, which is formed by selective oxidation of silicon in the surface layer of Fe-3 mass%Si. This indicates that silicon oxides formed in the surface layer of Fe-3 mass%Si act as a path for the gold penetration, which is presumably the interface between the iron matrix and a network of silicon oxides.