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. 
E. Cinquanta, E. Scalise, D. Chiappe, C. Grazianetti, B. van den   Broek, M. Houssa, M. Fanciulli and A. Molle
cond-mat.mes-hall cond-mat.mtrl-sci