Silicene: Prediction, Synthesis, Application

285 Pages·2018·16.374 MB·English

by  Patrick Vogt, Guy Le Lay

NanoScience and Technology
Patrick Vogt · Guy Le Lay    Editors
Silicene
Prediction, Synthesis, Application
NanoScience and Technology
Series editors
Phaedon Avouris, IBM Research, Yorktown Heights, USA
Bharat Bhushan, The Ohio State University, Columbus, USA
Dieter Bimberg, Technical University of Berlin, Berlin, Germany
Cun-Zheng Ning, Arizona State University, Tempe, USA
Klaus von Klitzing, Max Planck Institute for Solid State Research, Stuttgart,
Germany
Roland Wiesendanger, University of Hamburg, Hamburg, Germany
Theseries NanoScienceandTechnologyisfocusedonthefascinatingnano-world,
mesoscopic physics, analysis with atomic resolution, nano and quantum-effect
devices, nanomechanics and atomic-scale processes. All the basic aspects and
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More information about this series at http://www.springer.com/series/3705
Patrick Vogt Guy Le Lay
(cid:129)
Editors
Silicene
Prediction, Synthesis, Application
123
Editors
Patrick Vogt GuyLe Lay
Institut für Physik CNRS, PIIMUMR 7345
Technische UniversitätChemnitz Aix-Marseille University
Chemnitz, Germany Marseille, France
ISSN 1434-4904 ISSN 2197-7127 (electronic)
NanoScience andTechnology
ISBN978-3-319-99962-3 ISBN978-3-319-99964-7 (eBook)
https://doi.org/10.1007/978-3-319-99964-7
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Preface
Elemental 2D Materials Beyond Graphene
Nano-structures, objects limited in one or more dimensions to the nanometre scale,
form the basis of nanotechnology, a research field initiated by the famous talk of
Richard Feynman in 1959, entitled “There is plenty of room at the bottom”. In this
talk, Richard Feynman did not only describe the enormous impact that nanotech-
nologywouldhavefortechnologicalapplicationsbutunderlinedalsothenecessityof
microscopic imaging on an atomic scale, meaning the visualisation of single atoms.
Such an enormous resolution was achieved through the invention of the scan-
ning tunnelling microscope by Gerd Binnig and Heinrich Rohrer; they were
awarded the Nobel Prize in Physics in 1986. This microscope allowed for the first
timetoimagesingleatomsofasolidsurface,openingthedoorfortheinvestigation
ofallsortsofcrystallinenano-objects.Asanaturalconsequence,theunderstanding
of solid matter on an atomic scale has enormously evolved and formation, struc-
turing and manipulation of nano-objects came into focus.
These nano-objects can be described as quasi-0D, -1D or -2D allotropes of
chemically the same 3D crystal, where the dimensionality is one of the most
defining material parameters. This means that the identical material exhibits dras-
tically different properties depending on its dimensionality, making the dimen-
sionality a key-parameter for the development of new pioneering concepts for
technological applications. Although quasi-0D and -1D objects had been well
investigated and understood, two-dimensional crystals were experimentally
unknownbeforethediscoveryofgraphenein2004,awardedthe2010NobelPrize
inPhysics.Thisfirstpurely2Dmaterialconsistsofcarbonatomsarrangedina2D
hexagonal honeycomb structure, and was obtained by exfoliating single atomic
layersfroma parentgraphitecrystal using apiece ofstickytape. Theoriginfor its
purely2Datomicarrangementisthepreferentialsp2hybridizationofcarbonatoms,
a fundamental aspect for organic chemistry.
Symmetry and dimensionality make graphene to stand out by its resulting
peculiar physical properties. For instance, the electrons in graphene behave like
v
vi Preface
masslessrelativisticparticles,theso-calledDirac-fermions.Consequently,graphene
hasaveryhighelectronmobility,makingitanidealcandidatefortheapplicationin
electronic devices. The missing electronic band gap in graphene is the only draw-
back and hinders its application in logic devices. In the years after its discovery, a
multitude of technological applications of graphene was envisaged, ranging from
ultrafast transistors tothereplacementsof silicon- based computer technology.
Suchoptimisticexpectationshavemotivatedthesearchforother,maybesimilar,
2D materials, which exhibit an intrinsic electronic band gap and can be exfoliated
from natural layered crystals, in analogy to graphite and graphene. These layered
materials have strong in-plane bonds and weaker van der Waals coupling between
the atomic layers, allowing their exfoliation. The family of transition metal
dichalcogenide monolayers was the next group of 2D materials and initially
exploredbyalargenumberofresearchers,nicelyillustratedforMoS ,thematerial,
2
which gave birth to the first single-layer transistors in early 2011.
Deviatingfromthisexfoliationapproachofbinarycompounds,aroundthattime
only a few research groups were striving to create novel mono-elemental 2D
materials synthetically. Already in 1994, 10 years before the advent of graphene,
the possible existence of 2D silicon and germanium analogues to graphene had
been suggested theoretically. These 2D materials were later coined silicene and
germanene, though having a slightly buckledatomichoneycombstructure because
ofthedifferentpreferentialhybridizationstateoftheSiandGeatomsincomparison
to C atoms in graphene.
It was only in 2012, that silicene was synthesized, under ultrahigh vacuum
conditions on a silver (111) single crystal by Si molecular beam epitaxy, and, in
parallel, on zirconium diboride thin films grown on Si(111) substrates by Si seg-
regation through the film. This realization has faced many hurdles, and the prop-
erties of the resulting 2D Si layers have been discussed controversially in the
literature.Thisdisputeincludeditsmerepotentialexistence,itspracticalfeasibility
and its notation as silicene. In fact, the layers grown epitaxially on a supporting
substrate material differ compared to the theoretically calculated properties of
so-called freestanding silicene. The latter is only a theoretical concept, as its
existence has not been demonstrated yet. However, it turned out that even though
influencedbythesubstratethe2Dcharacterofepitaxialsiliceneclearlycontributes
to its fundamental properties.
Quickly after its synthesis, the first silicene transistor—with a single-layer
channel—operating at room temperature, with ambipolar character and good
mobilities, was reported in 2015. The synthesis of epitaxial silicene further laun-
ched an intensive search for finding ways to epitaxially synthesize other group-IV
materials based on germanium and tin, named germanene and stanene (from the
latinwordfortin:stannum),respectively.Thesynthesisofgermanenewasreported
in 2014, of stanene in 2015. By this endeavour, a new burgeoning field took the
stage, with the young family of buckled 2D elemental materials. A cornucopia of
unprecedented outstanding properties are predicted for these materials, resulting
from their slightly buckled atomic structure and a significant spin–orbit interaction
in their atomic constituents.
Preface vii
Those expectations range from the tunability of their electronic band gap, the
modification of their electronic properties by functionalization, to their 2D topo-
logical properties. The latter opens the way to a quantum spin Hall effect at
accessible temperatures (if not even, room temperature). The evolution of topo-
logically non-trivial properties will be more robust for the heavier constituting
elements,becauseoftherelatedstrongerspin–orbitinteraction,furtherstrengthened
bythelargerbuckling.Topologicalpropertiesareenvisagedtoenableentirelynew
conceptsinelectronicdevicesandtheirpredictionanddescriptionwasawardedthe
2016 Nobel Prize in physics.
In this book, the theoretical background and predictions, the growth and syn-
thesis of 1D and 2D Si-structures, their properties and application for electronic
devices such as a field effect transistor and the synthesis of other elemental 2D
materials,likegermanenearepresentedanddiscussedbykeyinternationalexperts.
Chemnitz, Germany Patrick Vogt
Marseille, France Guy Le Lay
Contents
1 A Vision on Organosilicon Chemistry and Silicene. . . . . . . . . . . . . 1
Deepthi Jose, Chandra Chowdhury and Ayan Datta
1.1 Aromatic Molecules and Silicon Substituted Cyclic Rings . . . . 1
1.2 Chemical Bonding: Unsaturated Carbon Systems Versus
Silicon Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3 Effect of Buckling Distortions in Si Rings: The Psuedo
6
Jahn-Teller (PJT) Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.4 Chemical Functionalization on Silicon Rings to Make
Them Planar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.5 Electron and Hole Transport in Silicene . . . . . . . . . . . . . . . . . 11
1.6 Reactivity of Silicene Towards Hydrogen and Band
Gap Tuning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
1.7 Tip Enhanced Raman Spectroscopy (TERS) as a Probe
for the Buckling Distortion in Silicene . . . . . . . . . . . . . . . . . . 16
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2 Density-Functional and Tight-Binding Theory of Silicene
and Silicane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
V. Zólyomi, N. D. Drummond, J. R. Wallbank and V. I. Fal’ko
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.2 First-Principles Theory of Silicene and Silicane . . . . . . . . . . . . 25
2.2.1 Structure, Stability, and Electronic Band Structure
of Silicene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.2.2 Structure, Stability, and Electronic Band Structure
of Silicane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.3 Tight-Binding Description of Silicene and Silicane . . . . . . . . . 30
2.3.1 All-Valence Tight-Binding Model of Silicene . . . . . . . 30
2.3.2 All-Valence Tight-Binding Model of Silicane . . . . . . . 31
2.4 Silicene in a Transverse External Electric Field . . . . . . . . . . . . 34
ix
x Contents
2.5 SO Coupling and Topological Phase Transition
in Silicene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
2.5.1 SO Induced Band Gap in Silicene . . . . . . . . . . . . . . . 37
2.5.2 Transition from Topological Insulator to Band
Insulator State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
2.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3 Electronic and Topological Properties of Silicene, Germanene
and Stanene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Motohiko Ezawa
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
3.2 Graphene and Silicene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
3.2.1 Graphene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
3.2.2 Silicene and Tunable Band Gap . . . . . . . . . . . . . . . . . 46
3.2.3 Generalized Dirac Mass Terms . . . . . . . . . . . . . . . . . 49
3.3 Berry Curvature and Chern Number . . . . . . . . . . . . . . . . . . . . 49
3.3.1 TKNN Formula . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
3.3.2 Berry Curvature in Centrosymmetric System . . . . . . . 51
3.3.3 Pontryagin Number . . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.3.4 Classification of Topological Insulators . . . . . . . . . . . 54
3.4 Topological Edges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
3.4.1 Bulk-Edge Correspondence . . . . . . . . . . . . . . . . . . . . 55
3.4.2 Herical Edges and Chiral Edges . . . . . . . . . . . . . . . . . 56
3.4.3 Inner Edges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.4.4 Topological Kirchhoff Law . . . . . . . . . . . . . . . . . . . . 58
3.5 Topological Quantum Field-Effect Transistor . . . . . . . . . . . . . . 59
3.6 Impurity Effects to Topological Quantum Field-Effect
Transistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
3.6.1 QSH Phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
3.6.2 QVH Phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
3.7 Phosphorene and Anisotropic Honeycomb Lattice . . . . . . . . . . 65
3.7.1 Band Structure of Anisotropic Honeycomb
Nanoribbons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
3.7.2 Topological Origin of Flat Bands . . . . . . . . . . . . . . . . 68
3.7.3 Wave Function and Energy Spectrum
of Edge States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
4 Optical Properties of Silicene and Related Materials
from First Principles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Friedhelm Bechstedt, Lars Matthes, Paola Gori and Olivia Pulci
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
4.2 Theoretical and Numerical Methods . . . . . . . . . . . . . . . . . . . . 74