Nano Lett. http://doi.org/jj8 (2012)

Like graphene, silicene is a single layer of a material with a honeycomb lattice. Unlike graphene, however, it cannot be obtained by mechanical exfoliation of a three-dimensional stack. The material was first predicted theoretically and then synthesized in the form of sheets and long ribbon structures by evaporating silicon onto silver films. Paola de Padova and colleagues in Italy, Japan and France have now created perfectly aligned multilayer silicene nanoribbons that exhibit properties that may be useful in electronic applications.

The researchers first evaporated silicon onto a Ag(110) surface and then used scanning tunnelling microscopy to reveal high-aspect-ratio zigzag ribbons, perfectly aligned on the surface and separated by areas of single-layer silicon. The ribbons have a triangular cross-section, meaning that rather than lying flat on the substrate they are slightly separated from it. Angle-resolved photo-emission spectroscopy data showed Dirac cones originating from the valence and conduction bands and an electron Fermi velocity comparable to that of free-standing graphene. The Dirac cones are separated by a small gap. Such a gap is also observed in the single layers, but is smaller in the multilayer case, reflecting a weaker effect of the lattice mismatch with the silver substrate.