Stratification of the Fe/Si(001)2 × 1 Interface by Heat Treatment of the Wetting Layer

The study was carried out by LEED, AES, EELS, and AFM methods. Films of Fe/Si(001)2 × 1 were obtained at substrate temperatures of 30°C and source temperatures of 1250°C. Wetting layer (WL) Fe on Si(001)2 × 1 was formed by two-stage annealing at temperatures and thicknesses of 500 and 250°C and 1 monolayer (ML) and 3 ML, respectively. Analysis and interpretation of the data obtained, taking into account possible reaction patterns, showed that after annealing at 1 ML thickness, the Fe composition corresponded to 2 ML Si/Fe. Further, at 2 ML, it changed to Fe/Si/Fe, at 3 ML, it changed to Fe–FeSi, and after annealing, to FeSi. At 4 ML, there was formation of FeSi/FeSi₂ film. And, further, at 7 ML and 10 ML, the composition of the films became Fe₃Si/FeSi₂ and, respectively, Fe/Fe₃Si/FeSi₂. At the same time, the upper Fe₃Si layers were coated with 0.6 ML and the Fe layers with 0.3 ML of segregated Si atoms, which number increased, after annealing at 250°C, to 0.6 ML in the latter case. In the obtained Fe film, the size and average grain height were 10−20 nm and, respectively, ∼0.4 nm.