Silicene

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The successful formation of silicene was only reported in April 2012 by a team of researchers in Italy, Germany and France, but it could potentially usurp its carbon-based counterpart graphene as the go-to wonder material for next-generation electronics.

Silicene is the equivalent of graphene for silicon, i.e. a monolayer of silicon in a honeycomb structure.The successful formation of silicene was only reported in April 2012 by a team of researchers in Italy, Germany and France, but it could potentially usurp its carbon-based counterpart graphene as the go-to wonder material for next-generation electronics.

Silicene has potentially useful chemical and physical properties and is predicted to feature Dirac fermions at the Fermi energy just like graphene. Research in silicone is at a very early stage but is gaining more and more attention.

Figure 1: The result of theoretical calculation of  a stable silicene structure on ZrB2(0001) (Image credit: Japan Advanced Institute of Science and Technology (JAIST).

Silicene is created by epitaxial growth of silicon as stripes on Ag(001), ribbons on Ag(110), and sheets on Ag(111) to form a single layer of atoms. One of the downside of using graphene in electronics is that it doesn’t possess a bandgap in its electronic states. There has been progress in inducing a band gap into graphene, but this involves protracted methods such as bringing the graphene sheets into contact with a strongly-interacting substrate, which can sufficiently perturb the electronic properties. Silicene however exhibits a band gap even without modification and it has the advantage of inherent compatibility with the silicon technology infrastructure already used in manufacturing much of today’s digital electronics. The buckled hexagonal silicene lattice allows for electric field control of the band gap, contrary to the case of graphene.

Another advantage is the spin-orbit coupling in silicene is much larger than in graphene, such that a 2D topological insulator state, a quantum spin Hall insulator (QSHI), may be reached at relatively high temperature (10-20 K).  At silicene/superconductor interfaces, the helical edge modes of  the QSHI are expected to host Majorana  fermions, which are highly sought-after in the context of topological quantum  computing.2

Figure 2: STM image of silicene on ZrB2 thin film (Image credit: Japan Advanced Institute of Science and Technology (JAIST).

Potential future applications of silicene range from the aforementioned nanoelectronics applications to ultra-sensitive chemical sensors (electronic noses), biological and cancer markers, solar cell technology, catalysts and hydrogen storage.

Sources:

1. Silicene: Compelling Experimental Evidence for Graphenelike Two-Dimensional Silicon, Phys. Rev. Lett. 108, 155501 (2012).

2. A review on silicene — New candidate for electronics, Surface Science Reports, Volume 67, Issue 1, 1 January 2012.

 

 

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