Self formation of Si nanostructured layer at the metal silicide/silicon interface

The experimental confirmation of the concept of the Si nanocrystallites self-formation in nanostructured Co layer (60 nm)/Si interface at the solid-state reaction between Si and Co with CoSi2 formation is presented. The following evidences have been obtained: (i) the nanostructured CoSi2 layer consists of CoSi2 particles with typical lateral size of 24–100.5 nm, separated by pores in Si, having typical depth of 0.4–6.7 nm and this relief determines the roughness of the interface layer with Si nanocrystallites embedded into CoSi2 matrix; (ii) the transverse optical (TO) phonon modes of Si nanocrystallites lattice are at wave numbers of 464 and 478 cm−1 and the vibration mode of SiSi bond is at 608 cm−1 for Si nanocrystallites of 2.5–4 nm size; (iii) the band gap of Si nanocrystallites equals Eg=1.23, 1.73, 2.74 eV in (Pt–Ir) tip-nanostructured CoSi2 layer/c-Si tunnel structures; (iv) the shape of the interface layer with these Si nanocrystallites stipulates the shape of the conductance (G)–voltage (V) curve with minimum at V=−0.6 V, which is typical for the metal-dielectric-semiconductor (MDS) structure (Si nanocrystallites as a dielectric). arguments are further supported by our recent sensor characteristics studies on the nanostructured CoSi2 layer/c-Si structures with W probe.