Initial Stages of Reactions between Monolayer Fe and Si(001) Surfaces

Reactions between 1.5 monolayer(ML) Fe deposited on Si(001)-2 × 1 and -dihydride surfaces were studied in situ by reflection high-energy electron diffraction and time-of-flight ion scattering spectrometry with the use of 25 keV H ions. The reactions between Fe and Si which were successively deposited on Si(001)-dihydride surface were also studied. After the room temperature deposition Fe reacted with Si(001)-2 × 1 substrate resulting in the formation of polycrystalline Fe5Si3. By annealing to 560∼650°C composite heteroepitaxial layer of both type A and type B β -FeSi2 was formed. On the dihydride surface polycrystalline Fe was observed after 1.5ML Fe deposition at room temperature, and reaction between Fe and Si(001)-dihydride surface is not likely at room temperature. We observed 3D rough surface when we deposited only Fe layer on the dihydride surface and annealed above 700°C. The hydrogen termination of Si(001) surface prevents the deposited Fe from diffusing into the substrate below 500°C, however the annealing above 710°C leads to the diffusion. We obtained 2D ordered surface, which showed 3 × 3 RHEED pattern as referenced to the primitive unreconstructed Si(O01) surface net, when we deposited 2.5ML Fe and 5.8ML Si successively onto Si(001)-dihydride surface and annealed to 470°C.