Initial stages of iron silicide formation on the Si(100)2 x 1 surface

The initial stages of iron silicide growth on the Si(100)2 x 1 surface during solid-phase synthesis were investigated by photoelectron spectroscopy using synchrotron radiation. The experiments were made on iron films of 1-50 monolayer (ML) thickness in the temperature range from room temperature to 750 degrees C. Our results support the existence of three stages in the Fe deposition on Si(100) at room temperature, which include formation of the Fe-Si solid solution, Fe3Si silicide and an iron film. The critical Fe dose necessary for the solid solution to be transformed to the silicide is found to be 5 ML. The solid-phase reaction was found to depend on the deposited metal dose. At 5 ML, the reaction begins at 60 degrees C, and the solid-phase synthesis leads to the formation of only metastable silicides (FeSi with the CsCl-type structure, gamma-FeSi2 and alpha-FeSi2). A specific feature of this process is Si segregation on the silicide films. At a thickness of 15 ML and more, we observed only stable phases, namely, Fe3Si, epsilon-FeSi and beta-FeSi2. (C) 2007 Elsevier B.V. All rights reserved.