Thursday, June 6, 2013

Silicene: a honeycombed, atom-thick sheet of silicon named to recall similarly structured graphene

Silicene sheets can be epitaxially grown on a close-packed silver surface, Ag(111), via silicon atomic flux under ultrahigh vacuum conditions [1]. The condensed atoms arrange themselves within a two-dimensional honycomb lattice, geometrically resembling the structure of carbon atoms in graphene sheets. Chemists like to indicate structural and functional similarity of compounds in the ending of their names:  hence, the name silicene, which rhymes with graphene.

Equal or similar topology, however, does not necessarily imply property similarity. So far, many silicene properties have been predicted rather than measured, since the graphen-like form of silicon proves hard to handle [2].  Whereas graphene is very stable, silicene is reacting with other molecules and materials in its neighborhood. Silicene sheets also show a tendency to crinkle. Yet, the interest in silicene, its properties and potential applications is rapidly growing [3-5].

And to continue with the analogy of chemical elements of the carbon group (Group IV or Group 14), germanene—the planar, hexagonal germanium allotrope—could then be the next thin sheet.   

The CurlySMILES notation for silicene is [Si]{alall=silicene}, in which the square bracket code (SQC) for silicon is annotated with al for atomic layer and all for allotrope. The analogous linear notation for graphene and germanene are [C]{alall=graphene} and [Ge]{alall=germanene}, respectively.

Keywords: inorganic chemistry, material science, nanotechnology, epitaxy, spontaneous organization, honeycomb lattice, allotropes.

References and more to explore
[1] B. Lalmi et al.: Epitaxial growth of a silicene sheet. Appl. Phys. Lett. 2010, 97, pp. 223109-223110. doi: 10.1063/1.3524215.
[2] G. Brumfiel: Sticky problems snares wonder material. Nature March 14, 2013, 495, pp. 152-153. doi: 10.1038/495152a.
[3] B. Feng et al.: Evidence of Silicene in Honeycomb Structures of Silicon on Ag(111). Nano Lett. 2012, 12 (3), pp. 3507-3511. doi: 10.1021/nl301047g.
[4] Z. Ni et al.: Tunable Bandgap in Silicene and Germanene. Nano Lett. 2012, 12 (1), pp. 113-118. doi:
[5] Foresight Institute: Silicene: silicon's answer to graphene [].

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