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Silicene

Si

Also called 2D silicon

exists only on a substrate semimetal

A silicon version of graphene. Silicon prefers to buckle rather than lie flat, and it does not exist as a free-standing sheet: it has to be grown on a metal surface in ultra-high vacuum. Its appeal is compatibility with silicon technology; its problem is that it oxidises within minutes in air.

Crystal structure

  • Si
Cell
Hexagonal, a = 3.83 Å
Atoms per cell
2
Si–Si bond
2.25 Å
Height
0.44 Å between the outer atom centres
A honeycomb like graphene, except that the two sublattices sit 0.44 Å apart in height. Silicon forms π bonds less readily than carbon, and the buckling mixes sp2 with sp3 bonding. It also means an electric field across the sheet makes the two sublattices inequivalent, opening a band gap that the field can tune. DFT (LDA) prediction for the free-standing sheet: a = 3.83 Å, buckling 0.44 Å. Silicene made so far exists only on substrates such as Ag(111), where it takes other, reconstructed forms.

Key properties

  • Buckling makes the band gap tunable, in principle, with a perpendicular electric field
  • Predicted spin–orbit gap ~1.5 meV – tens of times larger than graphene’s – making it a quantum spin Hall candidate
  • The only transistor demonstration (2015) reached ~100 cm2/(V·s) and degraded within minutes of air exposure
  • No free-standing silicene has been isolated

How it is made

  • MBE deposition of Si on Ag(111) at ~200–300 °C in ultra-high vacuum – the standard route
  • Growth on Ir(111), ZrB2 and other substrates reported, with debated structures
  • Encapsulated delamination: cap with Al2O3 in situ, flip, and use the remaining Ag as contacts – the route to the first devices

Uses, and how close they are

  • Ultrathin silicon transistors (proof of concept)lab

Readiness runs lab → prototype → pilot → deployed.

Open problems

  1. Is the structure on Ag(111) genuinely silicene or a Si–Ag surface alloy, and does any Dirac character survive on any substrate?
  2. Can a weakly interacting, insulating substrate support silicene growth so its intrinsic electronic structure can be measured?
  3. Can encapsulation make silicene devices last long enough to be useful?

Going deeper

Short notes for specialists. Choose a lens in the header and yours comes first.

For theoreticians · your lens

Buckling mixes sp2 and sp3 character, so low-energy bands respond to perpendicular fields and spin–orbit coupling is appreciable; Kane–Mele-type models predict field-tunable topological and valley-polarised phases. Substrate interactions are decisive: free-standing calculations are a poor guide to what is measured on Ag(111), where hybridisation removes the Dirac cone.

For experimentalists · your lens

Everything happens in ultra-high vacuum: characterise by STM, LEED and ARPES in situ. Treat Raman on capped samples with care – a peak near 516 cm−1 has been attributed to silicene, but bulk-like silicon (520 cm−1) and Ag–Si phases can mimic it.

For engineers · your lens

Attractive on paper for silicon compatibility, but metal-substrate growth, vacuum processing and a lifetime of minutes in air make it impractical. 2D semiconductors with native band gaps and air stability, such as the TMDCs, are the realistic alternative.

In the research tracks

Growth methods

Recent news

The newest items tagged Silicene, from the news feed updated 5 Oct 2026.

Journal Nano Letters

Interfacing Two Topological Insulators, α -Bismuthene and β -Silicene, with a Rare-Earth Magnetic Monolayer

The integration of diverse electronic phenomena, such as magnetism and nontrivial topology, into a single low-dimensional system gives rise to unusual quantum effects. Here we combine two 2D topological insulators, α-bismuthene and β-silicene, with a Ho monolayer. Bismuthene is synthesized within a rarely realized…

TheoryExperimentAntimonene, bismuthenePhosphoreneSilicene
Preprintnot yet peer reviewed arXiv

First principles calculations of electric-field-driven topological phase transitions in silicene, germanene and stanene

The emergence of two-dimensional topological materials, particularly the group-14 monolayers known as silicene, germanene, and stanene has opened promising pathways for next-generation nanoelectronics and spintronics. Their buckled honeycomb structure and strong spin-orbit coupling allow for bandgap engineering via a…

TheoryGermanene, staneneSilicene

All 12 items tagged Silicene in the news feed  ·  RSS feed for Silicene

Key references

  1. Two- and one-dimensional honeycomb structures of silicon and germaniumCahangirov et al. · Physical Review Letters 102, 236804 (2009)cited by 3,383doi:10.1103/PhysRevLett.102.236804
  2. Silicene: compelling experimental evidence for graphenelike two-dimensional siliconVogt et al. · Physical Review Letters 108, 155501 (2012)cited by 3,914doi:10.1103/PhysRevLett.108.155501
  3. Silicene field-effect transistors operating at room temperatureTao et al. · Nature Nanotechnology 10, 227 (2015)cited by 1,668doi:10.1038/nnano.2014.325
Xenes Germanene, stanene Germanene, stanene and plumbene exists only on a substrate
type
depends on form
thickness
One buckled atomic layer
most mature
lab
Quantum spin Hall edge-state devices Carbon Graphene van der Waals crystal
type
semimetal
thickness
~0.335 nm
band gap
none
most mature
deployed
Composites, coatings and conductive inks (as few-layer flakes)