Synthesis of iron suicides by electron-beam evaporation: Effects of substrate prebaking temperature and Fe deposition thickness

The microstructures of iron suicides synthesized by electron-beam evaporation were examined as a function of iron (Fe) deposition thickness on a silicon (Si) substrate. Si(100) substrates were prebaked at 923 K to clean their surface, and then an Fe thin film layer with a thickness of 2-10 nm was deposited. Transmission electron microscopy observations revealed that the atomistic structures of the as-deposited thin film layer depend on the Fe deposition thickness: amorphous layer (2nm) and crystalline Fe layer (4-10 nm). After thermal annealing at 1173 K for 2h, the deposited Fe atoms diffused into the Si substrate and formed iron silicides. It was found that both ε-FeSi and β-FeSi₂ exist at the deposition thickness of 2 nm, and that the amount of β-phase increases with the deposition thickness. Well-isolated iron silicide nanoparticles were obtained at deposition thicknesses less than 4 nm, whereas the deposition thickness of >10 nm was necessary for the formation of a continuous β-FeSi₂ layer on the Si substrate. We also examined the effects of prebaking temperature on the as-deposited thin film layer and annealing-induced iron suicide phases.