The instability of silicene on Ag(111)

Acun, Adil; Poelsema, Bene; Zandvliet, Henricus J.W.; Gastel, Raoul van

doi:10.1063/1.4860964

Cited by 83 publications

(81 citation statements)

References 27 publications

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“…Silicene and silicene nanoribbons have already been grown on Ag(110), Ag(111), ZrB2(0001) and Ir(111) surfaces [10][11][12][13][14][15][16], but to the best of our knowledge there are only two papers that report the growth of germanene [17,18]. Dávila et al [17] have studied the growth germanene on Au (111) using scanning tunneling microscopy, synchrotron radiation core-level spectroscopy and density functional theory calculations.…”

Section: Abstract: Germanene Platinum Germaniummentioning

confidence: 99%

Germanene termination of Ge₂Pt crystals on Ge(110)

Bampoulis¹,

Zhang²,

Safaei³

et al. 2014

J. Phys.: Condens. Matter

163

183

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We have investigated the growth of Pt on Ge(110) using scanning tunneling microscopy and spectroscopy. The deposition of several monolayers of Pt on Ge(110) followed by annealing at 1100 K results in the formation of three-dimensional metallic Pt-Ge nanocrystals. The outermost layer of these crystals exhibits a honeycomb structure. The honeycomb structure is composed of two hexagonal sub-lattices that are displaced vertically by 0.2 Å with respect to each other. The nearest-neighbor distance of the atoms in the honeycomb lattice is 2.50.1 Å, i.e. very close to the predicted nearest-neighbor distance in germanene (2.4 Å). Scanning tunneling spectroscopy reveals that the atomic layer underneath the honeycomb layer is more metallic than the honeycomb layer itself. These observations are in line with a model recently proposed for metal di-(silicides/)germanides: a hexagonal crystal with metal layers separated by semiconductor layers with a honeycomb lattice. Based on our observations we propose that the outermost layer of the Ge2Pt nanocrystal is a germanene layer. Keywords: germanene, platinum, germaniumIn 2004 Novoselov and Geim [1] ignited a revolution in materials science by preparing graphene, i.e. a single layer of sp 2 hybrizided carbon atoms. The unique electronic structure of this archetype 2D material has led to a large number of exciting physical discoveries [2][3][4]. Shortly after this discovery it has been suggested that two-dimensional sheets of other group IV elements, such as Si [5,6] and Ge [6], might exhibit similar properties as graphene. Already in 1994 Takeda and Shiraishi [7] performed quantum mechanical ab initio calculations on planar silicon and germanium structures that have the graphite structure. They pointed out that the lowest energy configuration was obtained if the two atoms of the honeycomb are slightly displaced with respect to each other in a direction normal to the planar structure. Their calculations also revealed that these buckled Si and Ge structures exhibited semimetallic properties. Unfortunately, they did not pay any attention to the exact k-dependence of the energy dispersion relations in the vicinity of the Fermi level. More than a decade later Guzmán-Verri and Lew Yan Voon [5] showed, using tight binding calculations, that a 2D silicon sheet with the graphite structure has Dirac cones. Hence the electrons in these 2D 2 silicon sheets behave as massless Dirac fermions. The Si and Ge analogues of graphene are referred to as silicene and germanene, respectively. First-principles calculations by Cahangirov et al. [6] revealed that a single sheet of germanium atoms with a honeycomb structure is also stable. The free-standing Ge honeycomb lattice is not fully planar, but buckled. The two hexagonal sub-lattices of the honeycomb lattice are displaced vertically by 0.64 Å, which is slightly larger than the buckling in silicene (0.44 Å). The buckling results into a weaker  bonding and the perpendicular pz orbital hybridizes with the in-plane orbitals.Similar to graphene...

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Section: Abstract: Germanene Platinum Germaniummentioning

confidence: 99%

Germanene termination of Ge₂Pt crystals on Ge(110)

Bampoulis¹,

Zhang²,

Safaei³

et al. 2014

J. Phys.: Condens. Matter

163

183

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“…In this paper we present a comprehensive study of a silicene layer that is known in the literature as (2 √ 3 × 2 √ 3)R30°s ilicene due to its approximate periodicity with respect to the Ag(111) surface lattice, as observed by LEED [10,20]. This structure is formed by silicene layers that are rotated by either +10.9°or −10.9°with respect to Ag(111).…”

Section: Introductionmentioning

confidence: 99%

Experimental and theoretical determination ofσbands on (“23×23”) silicene grown on Ag(111)

2015

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Silicene, the two-dimensional (2D) allotrope of silicon, has very recently attracted a lot of attention. It has a structure that is similar to graphene and it is theoretically predicted to show the same kind of electronic properties which have put graphene into the focus of large research and development projects worldwide. In particular, a 2D structure made from Si is of high interest because of the application potential in Si-based electronic devices. However, so far there is not much known about the silicene band structure from experimental studies. A comprehensive study is here presented of the atomic and electronic structure of the silicene phase on Ag(111) denoted as (2 √ 3 × 2 √ 3)R30°in the literature. Low energy electron diffraction (LEED) shows an unconventional rotated ("2 √ 3 × 2 √ 3") pattern with a complicated set of split diffraction spots. Scanning tunneling microscopy (STM) results reveal a Ag(111) surface that is homogeneously covered by the ("2 √ 3 × 2 √ 3") silicene which exhibits an additional quasiperiodic long-range ordered superstructure. The complex structure, revealed by STM, has been investigated in detail and we present a consistent picture of the silicene structure based on both STM and LEED. The homogeneous coverage by the ("2 √ 3 × 2 √ 3") silicene facilitated an angle-resolved photoelectron spectroscopy study which reveals a silicene band structure of unprecedented detail. Here we report four silicene bands which are compared to calculated dispersions based on a relaxed (2 √ 3 × 2 √ 3) model. We find good qualitative agreement between the experimentally observed bands and calculated silicene bands of σ character.

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“…9,10,41,42 This is one of the major reasons that TI properties of silicene are not experimentally demonstrated yet. First-principle calculations predict that silicene will become a large-gap semiconductor and lose the topological feature when exposed to the air due to modifications by the gas molecules like NO, O 2 , NH 3 and SO 2 .…”

Section: Robustness Of the Ti Phase Against Environmental Degradationmentioning

confidence: 96%

“…In experiments, silicene is also easily oxidised, leading to the absence of an observed Dirac cone. [41][42] The latest development of silicene encapsulated delamination technique, which has been successfully used to fabricate silicene-based FETs, offers a way to overcome these challenges. 8 The QW structure proposed in the present work can be regarded as an example of the silicene encapsulated technique where the cladding WTe 2 layer not only enhances the SOC effect, leading to the large nontrivial band gap as shown above, but also is able to protect the silicene from environmental degradation effects.…”

Section: Robustness Of the Ti Phase Against Environmental Degradationmentioning

confidence: 99%

Encapsulated Silicene: A Robust Large-Gap Topological Insulator

Kou

Yan

et al. 2015

ACS Appl. Mater. Interfaces

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The quantum spin Hall (QSH) effect predicted in silicene has raised exciting prospects of new device applications compatible with current microelectronic technology. Efforts to explore this novel phenomenon, however, have been impeded by fundamental challenges imposed by silicene's small topologically nontrivial band gap and fragile electronic properties susceptible to environmental degradation effects. Here we propose a strategy to circumvent these challenges by encapsulating silicene between transition-metal dichalcogenides (TMDCs) layers. First-principles calculations show that such encapsulated silicene exhibit a two-orders-of-magnitude enhancement in its nontrivial band gap, which is driven by the strong spin-orbit coupling effect in TMDCs via the proximity effect. Moreover, the cladding TMDCs layers also shield silicene from environmental gases that are detrimental to the QSH state in free-standing silicene. The encapsulated silicene represents a novel two-dimensional topological insulator with a robust nontrivial band gap suitable for room-temperature applications, which has significant implications for innovative QSH device design and fabrication.

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The instability of silicene on Ag(111)

Cited by 83 publications

References 27 publications

Germanene termination of Ge₂Pt crystals on Ge(110)

Germanene termination of Ge₂Pt crystals on Ge(110)

Experimental and theoretical determination ofσbands on (“23×23”) silicene grown on Ag(111)

Encapsulated Silicene: A Robust Large-Gap Topological Insulator

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The instability of silicene on Ag(111)

Cited by 83 publications

References 27 publications

Germanene termination of Ge2Pt crystals on Ge(110)

Germanene termination of Ge2Pt crystals on Ge(110)

Experimental and theoretical determination ofσbands on (“23×23”) silicene grown on Ag(111)

Encapsulated Silicene: A Robust Large-Gap Topological Insulator

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Resources

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Germanene termination of Ge₂Pt crystals on Ge(110)

Germanene termination of Ge₂Pt crystals on Ge(110)