Silicide formation at lower temperatures for cobalt and nickel on √3 x √3R30°-Ag/Si(111)

Because of the ease of formation, and good lattice match with Si, metal silicides often result in the formation of high-quality epitaxial layers and have established themselves over the years as important technological materials for use in industrial processes. To pave the way for industry applications of silicides, a concrete understanding of different transition metal/silicon interfaces is crucial. In this report, we propose a molecular-incident reaction effect (MoIRE) model that successfully explains the different chemical reactions for Co/Si and Ni/Si interfaces by the introduction of a $\sqrt 3 \times \sqrt 3 R{30^o} - {\text{Ag}}\,{\text{layer}}$. The interaction transfer of silicon atoms forms a Co silicide for ${\text{Co}}/\sqrt 3 \times \sqrt 3 R{30^o} - {\text{Ag}}/{\text{Si}}(111)$ with a thickness of a few nanometers, thus greatly reducing the temperature needed for the formation of a layered CoSi2 silicide compared to that for typical CoSi2 silicide formation at a Co/Si interface. Based on the MoIRE mechanism, the introduction of the $\sqrt 3 \times \sqrt 3 R{30^o} - {\text{Ag}}\,{\text{layer}}$ as an intermediate layer permits the silicidation temperature needed to produce a NiSi layer to be reduced to 400 K from typically above 600 K. This approach is advantageous for the formation of a silicide at the Ni/Si interface at low temperature and opens a possible way of fabricating Si-based spintronic devices at lower temperatures.