Getting through the Nature of Silicene: An sp<sup>2</sup>–sp<sup>3</sup> Two-Dimensional Silicon Nanosheet

Cinquanta, Eugenio; Scalise, Emilio; Chiappe, Daniele; Grazianetti, Carlo; Broek, Bas van den; Houssa, Michel; Fanciulli, M.; Molle, Alessandro

doi:10.1021/jp405642g

Cited by 175 publications

(202 citation statements)

References 33 publications

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“…28 They found in their planar form of silicene a Fermi velocity of about 10 5 m/s -about half that found in this study -but that in a buckled form the arrangement predominates. 10 The unit cell parameter of the 4 4 structure 13 was measured to be 11.78 Å and incorporated three hexagonal unit cells of silicene with a unit cell parameter of 3.926 Å; this value being just 1.2% larger than that calculated here suggesting the presence of a small amount of tensile strain. However the interaction with the silver substrate is complicated with substrate induced symmetry breaking resulting in 2/3 of the atoms being closer to the surface due to strong Si (3p) and Ag (5d) hybridisation.…”

Section: Lower Values Of Fermi Velocity Were Found In the Study By Gumentioning

confidence: 64%

Beyond Graphene: Stable Elemental Monolayers of Silicene and Germanene

Roome

Carey

2014

ACS Appl. Mater. Interfaces

273

174

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Two-dimensional materials are one of the most active areas of nanomaterials research. Here we report the structural stability, electronic and vibrational properties of different monolayer configurations of the group IV elemental materials silicene and germanene. The structure of the stable configuration is calculated and for planar and low (<1 Å) atomic buckling configurations, analysis of the electronic band structure reveals linear band dispersion giving rise to massless Dirac fermions with a Fermi velocity about two-thirds that of graphene.Monolayer stability is shown to be directly attributed to the phonons present with the instability being driven by the out-of-plane ZA and ZO phonon modes. Long momentum relaxation lengths and high carrier mobilities are predicted for silicene and germanene based devices as carrier relaxation via phonon scattering is found to be inhibited as the electron -optical phonon coupling matrix elements are calculated to be small, being about a factor of 25 times smaller than in graphene. The consequences for phonon scattering, high energy electrical transport and integration of elemental monolayers into electronic devices are further discussed.

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Section: Lower Values Of Fermi Velocity Were Found In the Study By Gumentioning

confidence: 64%

Beyond Graphene: Stable Elemental Monolayers of Silicene and Germanene

Roome

Carey

2014

ACS Appl. Mater. Interfaces

273

174

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“…The silicene samples analyzed in the present paper are characterized by the simultaneous presence of the 4 × 4 and the √ 13 × √ 13 superstructures (mixed-phase silicene). We also succeed in isolating the 2 √ 3 × 2 √ 3, as previously reported [1,11]. We perform ex situ Raman characterization by using a Renishaw Invia spectrometer equipped with the 2.5 eV/488 nm line of an Ar + laser line focused on the sample by a 50 × 0.75 N.A.…”

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confidence: 83%

“…In particular we show that interface states built up by mixed silicon and silver wave functions have a striking impact on the optical response of the low-dimensional Si/Ag system. The synthesis and the Al 2 O 3 capping of our samples has been extensively described elsewhere [1,[10][11][12] and is briefly described in the Supplemental Material [13]. The silicene samples analyzed in the present paper are characterized by the simultaneous presence of the 4 × 4 and the √ 13 × √ 13 superstructures (mixed-phase silicene).…”

mentioning

confidence: 99%

“…This can be easily understood in terms of the crystalline order of silicene, responsible for the narrow Raman peak, whereas the a-Si bears only short-range order resulting in a broad Raman bump peaked at 480 cm −1 . The perturbation of the D 3d point group symmetry with respect to 1 × 1 free standing silicene (FSS) induced by the Ag substrate triggers the activation of the breathinglike modes that in turn affect the Raman response of differently oriented phases as a function, for instance, of the exciting wavelength [11].…”

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confidence: 99%

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Optical response and ultrafast carrier dynamics of the silicene-silver interface

Cinquanta¹,

Fratesi

Conte

et al. 2015

Phys. Rev. B

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We report a combined experimental and theoretical study of the optical response of epitaxial silicene on silver. The silicene/Ag(111) ultraviolet-visible absorption spectra, which turn out to be strongly nonadditive, are analyzed in the framework of ab initio calculations. Electronic transitions involving silver states are found to provide huge contributions to the optical absorption of silicene, compatible with a strong Si-Ag hybridization. The results are independent of the specific silicene configuration and are also worked out for thin amorphous silicon. This points to a dimensionality-driven peculiar dielectric response of the two-dimensional-silicon/silver interface, which is confirmed by means of transient-reflectance spectroscopy. The latter shows a metalliclike relaxation time, hence demonstrating the effects of the strong hybridization arising in silicene/Ag (111) Recently, the integration of silicene in field-effect transistors (FET) [1] opened new challenges in the comprehension of the chemical and physical properties of this elusive two-dimensional (2D) allotropic form of silicon. Intense efforts have been devoted to the study of the epitaxial silicene/Ag(111) system in order to elucidate the presence of massless Dirac fermion in analogy with graphene [2,3]. Although recent experiments report on the linear dispersive bands [4], strong hybridization effects have been invoked as responsible for the disruption of π and π * bands in silicene superstructures on silver [5][6][7][8][9]. In this framework, the measured ambipolar effect in silicene-based FET characterized by a relatively high mobility when Ag is withdrawn, points to a complex physics at the silicene-silver interface, demanding a deeper comprehension of its details on the atomic scale.The present paper aims at elucidating the role of the Ag(111) metallic support in determining the physical properties of the Si/Ag (2D) interface, by means of optical techniques combined with theoretical calculations. In particular we show that interface states built up by mixed silicon and silver wave functions have a striking impact on the optical response of the low-dimensional Si/Ag system.

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“…For multilayer silicene covered by an aluminum oxide capping layer, only mild surface oxidation is identified after 24 h exposure in air. 46 Ex situ Raman spectra of bilayer silicene as a function of exposure time were examined by Du et al 56 The intensity of the E 2g peak decreases with increasing exposure time, combined with an intensified signal of the SiO x peak. Importantly, the E 2g peak survives in the Raman spectra until the sample has been exposed to ambient air for more than 150 h. Moreover, preservation of the silicene-silver (Ag) interface during transfer and subsequent device fabrication has proved to be an effective method during the encapsulated delamination transfer process, where the Raman signals taken 7 d after transfer remain the same as those for the freshly grown sample.…”

Section: Surface Innovationsmentioning

confidence: 99%

Raman Studies on Silicene and Germanene

LiuYani

Zhuang

HaoWeichang

et al. 2017

Surface Innovations

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Two-dimensional (2D) group IV elemental materials are expected to have similar electronic features to their lightest analogue, graphene. The favorable hybridization state of heavier group IV elements is the sp 3 state, leading to buckled structures instead of a planar one. These buckled structures could modulate the vibrational properties of these 2D materials by introducing a strain effect. In this review, the authors focus on the recent research on the Raman spectra of silicene and germanene from both the theoretical and experimental sides. The abundant superstructures of silicene and germanene are formed due to the different interaction strengths between silicene/germanene and underlying substrate, providing a way to modulate their phonon vibrational properties. Several factors affecting the vibrational modes are discussed, including the strain, doping, coverage and defect effects. Furthermore, the relationship between electron-phonon coupling strength and these factors is established based on the variation of Raman peak position and linewidth. Finally, the authors provide an overview of the general outlook and challenges for this field.

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Getting through the Nature of Silicene: An sp²–sp³ Two-Dimensional Silicon Nanosheet

Cited by 175 publications

References 33 publications

Beyond Graphene: Stable Elemental Monolayers of Silicene and Germanene

Beyond Graphene: Stable Elemental Monolayers of Silicene and Germanene

Optical response and ultrafast carrier dynamics of the silicene-silver interface

Raman Studies on Silicene and Germanene

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Getting through the Nature of Silicene: An sp2–sp3 Two-Dimensional Silicon Nanosheet

Cited by 175 publications

References 33 publications

Beyond Graphene: Stable Elemental Monolayers of Silicene and Germanene

Beyond Graphene: Stable Elemental Monolayers of Silicene and Germanene

Optical response and ultrafast carrier dynamics of the silicene-silver interface

Raman Studies on Silicene and Germanene

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Product

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Getting through the Nature of Silicene: An sp²–sp³ Two-Dimensional Silicon Nanosheet