$sp2$-like hybridization of silicon valence orbitals in silicene nanoribbons

Silicene nanoribbons grown on a silver (110) substrate have been studied by reflection electron energy loss spectroscopy as a function of the electron beam incidence angle $α$⁠. The spectra, taken at the Si K absorption edge (1.840 keV), reveal the presence of two distinct loss structures attributed to transitions $1s→π∗$ and $1s→σ∗$⁠, according to their intensity dependence on $α$⁠. Such behavior, when compared to graphite, attests the $sp2$-like hybridization of the silicon valence orbitals in the silicene nanoribbons as is, indeed, for carbon atomic bonds of graphene.