Getting through the nature of silicene: sp2-sp3 two-dimensional silicon nanosheet

By combining experimental techniques with ab-initio density functional theory calculations, we describe the Si/Ag(111) two-dimensional system in terms of a sp2-sp3 crystalline form of silicon characterized by a vertically distorted honeycomb lattice. We show that 2D sp2-sp3 Si NSs are qualified by a prevailing Raman peak which can be assigned to a graphene-like E2g vibrational mode and that highly distorted superstructures are semiconductive whereas low distorted ones behave as semimetals.