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Nazzari D, Genser J, Ritter V, Bethge O, Bertagnolli E, Grasser T, Weber WM, Lugstein A. Epitaxial Growth of Crystalline CaF 2 on Silicene. ACS APPLIED MATERIALS & INTERFACES 2022; 14:32675-32682. [PMID: 35793167 PMCID: PMC9305960 DOI: 10.1021/acsami.2c06293] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Silicene is one of the most promising two-dimensional (2D) materials for the realization of next-generation electronic devices, owing to its high carrier mobility and band gap tunability. To fully control its electronic properties, an external electric field needs to be applied perpendicularly to the 2D lattice, thus requiring the deposition of an insulating layer that directly interfaces silicene, without perturbing its bidimensional nature. A promising material candidate is CaF2, which is known to form a quasi van der Waals interface with 2D materials as well as to maintain its insulating properties even at ultrathin scales. Here we investigate the epitaxial growth of thin CaF2 layers on different silicene phases by means of molecular beam epitaxy. Through electron diffraction images, we clearly show that CaF2 can be grown epitaxially on silicene even at low temperatures, with its domains fully aligned to the lattice of the underlying 2D structure. Moreover, in situ X-ray photoelectron spectroscopy data evidence that, upon CaF2 deposition, no changes in the chemical state of the silicon atoms can be detected, proving that no Si-Ca or Si-F bonds are formed. This clearly shows that the 2D layer is pristinely preserved underneath the insulating layer. Polarized Raman experiments show that silicene undergoes a structural change upon interaction with CaF2; however, it retains its two-dimensional character without transitioning to a sp3-hybridized silicon. For the first time, we have shown that CaF2 and silicene can be successfully interfaced, paving the way for the integration of silicon-based 2D materials in functional devices.
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Affiliation(s)
- Daniele Nazzari
- Institute
of Solid State Electronics, Technische Universität
Wien, Gußhausstraße 25-25a, 1040 Vienna, Austria
- E-mail:
| | - Jakob Genser
- Institute
of Solid State Electronics, Technische Universität
Wien, Gußhausstraße 25-25a, 1040 Vienna, Austria
| | - Viktoria Ritter
- Institute
of Solid State Electronics, Technische Universität
Wien, Gußhausstraße 25-25a, 1040 Vienna, Austria
| | - Ole Bethge
- Infineon
Technologies Austria AG, Siemensstraße 2, 9500 Villach, Austria
| | - Emmerich Bertagnolli
- Institute
of Solid State Electronics, Technische Universität
Wien, Gußhausstraße 25-25a, 1040 Vienna, Austria
| | - Tibor Grasser
- Institute
for Microelectronics, Technische Universität
Wien, Gußhausstraße
27-29, 1040 Vienna, Austria
| | - Walter M. Weber
- Institute
of Solid State Electronics, Technische Universität
Wien, Gußhausstraße 25-25a, 1040 Vienna, Austria
| | - Alois Lugstein
- Institute
of Solid State Electronics, Technische Universität
Wien, Gußhausstraße 25-25a, 1040 Vienna, Austria
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Bergeron H, Lebedev D, Hersam MC. Polymorphism in Post-Dichalcogenide Two-Dimensional Materials. Chem Rev 2021; 121:2713-2775. [PMID: 33555868 DOI: 10.1021/acs.chemrev.0c00933] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Two-dimensional (2D) materials exhibit a wide range of atomic structures, compositions, and associated versatility of properties. Furthermore, for a given composition, a variety of different crystal structures (i.e., polymorphs) can be observed. Polymorphism in 2D materials presents a fertile landscape for designing novel architectures and imparting new functionalities. The objective of this Review is to identify the polymorphs of emerging 2D materials, describe their polymorph-dependent properties, and outline methods used for polymorph control. Since traditional 2D materials (e.g., graphene, hexagonal boron nitride, and transition metal dichalcogenides) have already been studied extensively, the focus here is on polymorphism in post-dichalcogenide 2D materials including group III, IV, and V elemental 2D materials, layered group III, IV, and V metal chalcogenides, and 2D transition metal halides. In addition to providing a comprehensive survey of recent experimental and theoretical literature, this Review identifies the most promising opportunities for future research including how 2D polymorph engineering can provide a pathway to materials by design.
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Affiliation(s)
- Hadallia Bergeron
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Dmitry Lebedev
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Mark C Hersam
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States.,Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States.,Department of Electrical and Computer Engineering, Northwestern University, Evanston, Illinois 60208, United States
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Krawiec M. Functionalization of group-14 two-dimensional materials. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:233003. [PMID: 29708504 DOI: 10.1088/1361-648x/aac149] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The great success of graphene has boosted intensive search for other single-layer thick materials, mainly composed of group-14 atoms arranged in a honeycomb lattice. This new class of two-dimensional (2D) crystals, known as 2D-Xenes, has become an emerging field of intensive research due to their remarkable electronic properties and the promise for a future generation of nanoelectronics. In contrast to graphene, Xenes are not completely planar, and feature a low buckled geometry with two sublattices displaced vertically as a result of the interplay between sp2 and sp3 orbital hybridization. In spite of the buckling, the outstanding electronic properties of graphene governed by Dirac physics are preserved in Xenes too. The buckled structure also has several advantages over graphene. Together with the spin-orbit (SO) interaction it may lead to the emergence of various experimentally accessible topological phases, like the quantum spin Hall effect. This in turn would lead to designing and building new electronic and spintronic devices, like topological field effect transistors. In this regard an important issue concerns the electron energy gap, which for Xenes naturally exists owing to the buckling and SO interaction. The electronic properties, including the magnitude of the energy gap, can further be tuned and controlled by external means. Xenes can easily be functionalized by substrate, chemical adsorption, defects, charge doping, external electric field, periodic potential, in-plane uniaxial and biaxial stress, and out-of-plane long-range structural deformation, to name a few. This topical review explores structural, electronic and magnetic properties of Xenes and addresses the question of their functionalization in various ways, including external factors acting simultaneously. It also points to future directions to be explored in functionalization of Xenes. The results of experimental and theoretical studies obtained so far have many promising features making the 2D-Xene materials important players in the field of future nanoelectronics and spintronics.
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Affiliation(s)
- Mariusz Krawiec
- Institute of Physics, Maria Curie-Sklodowska University, Pl. M. Curie-Skłodowskiej 1, 20-031 Lublin, Poland
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Deposition of topological silicene, germanene and stanene on graphene-covered SiC substrates. Sci Rep 2017; 7:15700. [PMID: 29146916 PMCID: PMC5691050 DOI: 10.1038/s41598-017-15610-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 10/30/2017] [Indexed: 11/09/2022] Open
Abstract
Growth of X-enes, such as silicene, germanene and stanene, requires passivated substrates to ensure the survival of their exotic properties. Using first-principles methods, we study as-grown graphene on polar SiC surfaces as suitable substrates. Trilayer combinations with coincidence lattices with large hexagonal unit cells allow for strain-free group-IV monolayers. In contrast to the Si-terminated SiC surface, van der Waals-bonded honeycomb X-ene/graphene bilayers on top of the C-terminated SiC substrate are stable. Folded band structures show Dirac cones of the overlayers with small gaps of about 0.1 eV in between. The topological invariants of the peeled-off X-ene/graphene bilayers indicate the presence of topological character and the existence of a quantum spin Hall phase.
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Huang L, Zhang YF, Zhang YY, Xu W, Que Y, Li E, Pan JB, Wang YL, Liu Y, Du SX, Pantelides ST, Gao HJ. Sequence of Silicon Monolayer Structures Grown on a Ru Surface: from a Herringbone Structure to Silicene. NANO LETTERS 2017; 17:1161-1166. [PMID: 28098458 DOI: 10.1021/acs.nanolett.6b04804] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Silicon-based two-dimensional (2D) materials are uniquely suited for integration in Si-based electronics. Silicene, an analogue of graphene, was recently fabricated on several substrates and was used to make a field-effect transistor. Here, we report that when Ru(0001) is used as a substrate, a range of distinct monolayer silicon structures forms, evolving toward silicene with increasing Si coverage. Low Si coverage produces a herringbone structure, a hitherto undiscovered 2D phase of silicon. With increasing Si coverage, herringbone elbows evolve into silicene-like honeycomb stripes under tension, resulting in a herringbone-honeycomb 2D superlattice. At even higher coverage, the honeycomb stripes widen and merge coherently to form silicene in registry with the substrate. Scanning tunneling microscopy (STM) was used to image the structures. The structural stability and electronic properties of the Si 2D structures, the interaction between the Si 2D structures and the Ru substrate, and the evolution of the distinct monolayer Si structures were elucidated by density functional theory (DFT) calculations. This work paves the way for further investigations of monolayer Si structures, the corresponding growth mechanisms, and possible functionalization by impurities.
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Affiliation(s)
- Li Huang
- Institute of Physics, Beijing Key Laboratory for Nanomaterials and Nanodevices, Chinese Academy of Sciences , Beijing 100190, P. R. China
- Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, P. R. China
| | - Yan-Fang Zhang
- Institute of Physics, Beijing Key Laboratory for Nanomaterials and Nanodevices, Chinese Academy of Sciences , Beijing 100190, P. R. China
- Department of Physics and Astronomy and Department of Electrical Engineering and Computer Science, Vanderbilt University , Nashville, Tennessee 37235, United State
| | - Yu-Yang Zhang
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences , Beijing 100049, P. R. China
- Department of Physics and Astronomy and Department of Electrical Engineering and Computer Science, Vanderbilt University , Nashville, Tennessee 37235, United State
| | - Wenyan Xu
- Institute of Physics, Beijing Key Laboratory for Nanomaterials and Nanodevices, Chinese Academy of Sciences , Beijing 100190, P. R. China
| | - Yande Que
- Institute of Physics, Beijing Key Laboratory for Nanomaterials and Nanodevices, Chinese Academy of Sciences , Beijing 100190, P. R. China
| | - En Li
- Institute of Physics, Beijing Key Laboratory for Nanomaterials and Nanodevices, Chinese Academy of Sciences , Beijing 100190, P. R. China
| | - Jin-Bo Pan
- Institute of Physics, Beijing Key Laboratory for Nanomaterials and Nanodevices, Chinese Academy of Sciences , Beijing 100190, P. R. China
| | - Ye-Liang Wang
- Institute of Physics, Beijing Key Laboratory for Nanomaterials and Nanodevices, Chinese Academy of Sciences , Beijing 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences , Beijing 100049, P. R. China
| | - Yunqi Liu
- Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, P. R. China
| | - Shi-Xuan Du
- Institute of Physics, Beijing Key Laboratory for Nanomaterials and Nanodevices, Chinese Academy of Sciences , Beijing 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences , Beijing 100049, P. R. China
| | - Sokrates T Pantelides
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences , Beijing 100049, P. R. China
- Department of Physics and Astronomy and Department of Electrical Engineering and Computer Science, Vanderbilt University , Nashville, Tennessee 37235, United State
| | - Hong-Jun Gao
- Institute of Physics, Beijing Key Laboratory for Nanomaterials and Nanodevices, Chinese Academy of Sciences , Beijing 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences , Beijing 100049, P. R. China
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Choi JH, Cui P, Chen W, Cho JH, Zhang Z. Atomistic mechanisms of van der Waals epitaxy and property optimization of layered materials. WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE 2017. [DOI: 10.1002/wcms.1300] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Jin-Ho Choi
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics; University of Science and Technology of China; Hefei China
- Research Institute of Mechanical Technology; Pusan National University; Pusan Korea
| | - Ping Cui
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics; University of Science and Technology of China; Hefei China
| | - Wei Chen
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics; University of Science and Technology of China; Hefei China
- Department of Physics and School of Engineering and Applied Sciences; Harvard University; Cambridge MA USA
| | - Jun-Hyung Cho
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics; University of Science and Technology of China; Hefei China
- Department of Physics and Research Institute for Natural Sciences; Hanyang University; Seoul Korea
| | - Zhenyu Zhang
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics; University of Science and Technology of China; Hefei China
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De Crescenzi M, Berbezier I, Scarselli M, Castrucci P, Abbarchi M, Ronda A, Jardali F, Park J, Vach H. Formation of Silicene Nanosheets on Graphite. ACS NANO 2016; 10:11163-11171. [PMID: 28024331 DOI: 10.1021/acsnano.6b06198] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The extraordinary properties of graphene have spurred huge interest in the experimental realization of a two-dimensional honeycomb lattice of silicon, namely, silicene. However, its synthesis on supporting substrates remains a challenging issue. Recently, strong doubts against the possibility of synthesizing silicene on metallic substrates have been brought forward because of the non-negligible interaction between silicon and metal atoms. To solve the growth problems, we directly deposited silicon on a chemically inert graphite substrate at room temperature. Based on atomic force microscopy, scanning tunneling microscopy, and ab initio molecular dynamics simulations, we reveal the growth of silicon nanosheets where the substrate-silicon interaction is minimized. Scanning tunneling microscopy measurements clearly display the atomically resolved unit cell and the small buckling of the silicene honeycomb structure. Similar to the carbon atoms in graphene, each of the silicon atoms has three nearest and six second nearest neighbors, thus demonstrating its dominant sp2 configuration. Our scanning tunneling spectroscopy investigations confirm the metallic character of the deposited silicene, in excellent agreement with our band structure calculations that also exhibit the presence of a Dirac cone.
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Affiliation(s)
| | - Isabelle Berbezier
- CNRS, Aix-Marseille Université , IM2NP, UMR 7334, Campus de St. Jérome, 13397 Marseille, France
| | - Manuela Scarselli
- Dipartimento di Fisica, Università di Roma "Tor Vergata" , 00133 Roma, Italy
| | - Paola Castrucci
- Dipartimento di Fisica, Università di Roma "Tor Vergata" , 00133 Roma, Italy
| | - Marco Abbarchi
- CNRS, Aix-Marseille Université , IM2NP, UMR 7334, Campus de St. Jérome, 13397 Marseille, France
| | - Antoine Ronda
- CNRS, Aix-Marseille Université , IM2NP, UMR 7334, Campus de St. Jérome, 13397 Marseille, France
| | - Fatme Jardali
- CNRS-LPICM, Ecole Polytechnique, Université Paris-Saclay , 91128 Palaiseau, France
| | - Jejune Park
- CNRS-LPICM, Ecole Polytechnique, Université Paris-Saclay , 91128 Palaiseau, France
| | - Holger Vach
- CNRS-LPICM, Ecole Polytechnique, Université Paris-Saclay , 91128 Palaiseau, France
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Du Y, Zhuang J, Wang J, Li Z, Liu H, Zhao J, Xu X, Feng H, Chen L, Wu K, Wang X, Dou SX. Quasi-freestanding epitaxial silicene on Ag(111) by oxygen intercalation. SCIENCE ADVANCES 2016; 2:e1600067. [PMID: 27532041 PMCID: PMC4985226 DOI: 10.1126/sciadv.1600067] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Accepted: 06/23/2016] [Indexed: 05/20/2023]
Abstract
Silicene is a monolayer allotrope of silicon atoms arranged in a honeycomb structure with massless Dirac fermion characteristics similar to graphene. It merits development of silicon-based multifunctional nanoelectronic and spintronic devices operated at room temperature because of strong spin-orbit coupling. Nevertheless, until now, silicene could only be epitaxially grown on conductive substrates. The strong silicene-substrate interaction may depress its superior electronic properties. We report a quasi-freestanding silicene layer that has been successfully obtained through oxidization of bilayer silicene on the Ag(111) surface. The oxygen atoms intercalate into the underlayer of silicene, resulting in isolation of the top layer of silicene from the substrate. In consequence, the top layer of silicene exhibits the signature of a 1 × 1 honeycomb lattice and hosts massless Dirac fermions because of much less interaction with the substrate. Furthermore, the oxidized silicon buffer layer is expected to serve as an ideal dielectric layer for electric gating in electronic devices. These findings are relevant for the future design and application of silicene-based nanoelectronic and spintronic devices.
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Affiliation(s)
- Yi Du
- Institute for Superconducting and Electronic Materials, Australian Institute for Innovative Materials, University of Wollongong, Wollongong, New South Wales 2525, Australia
| | - Jincheng Zhuang
- Institute for Superconducting and Electronic Materials, Australian Institute for Innovative Materials, University of Wollongong, Wollongong, New South Wales 2525, Australia
| | - Jiaou Wang
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Zhi Li
- Institute for Superconducting and Electronic Materials, Australian Institute for Innovative Materials, University of Wollongong, Wollongong, New South Wales 2525, Australia
| | - Hongsheng Liu
- Key Laboratory of Materials Modification by Laser, Ion, and Electron Beams (Dalian University of Technology), Ministry of Education, Dalian 116024, China
| | - Jijun Zhao
- Key Laboratory of Materials Modification by Laser, Ion, and Electron Beams (Dalian University of Technology), Ministry of Education, Dalian 116024, China
| | - Xun Xu
- Institute for Superconducting and Electronic Materials, Australian Institute for Innovative Materials, University of Wollongong, Wollongong, New South Wales 2525, Australia
| | - Haifeng Feng
- Institute for Superconducting and Electronic Materials, Australian Institute for Innovative Materials, University of Wollongong, Wollongong, New South Wales 2525, Australia
| | - Lan Chen
- Institute of Physics, Chinese Academy of Sciences, Haidian District, Beijing 100080, China
| | - Kehui Wu
- Institute of Physics, Chinese Academy of Sciences, Haidian District, Beijing 100080, China
| | - Xiaolin Wang
- Institute for Superconducting and Electronic Materials, Australian Institute for Innovative Materials, University of Wollongong, Wollongong, New South Wales 2525, Australia
| | - Shi Xue Dou
- Institute for Superconducting and Electronic Materials, Australian Institute for Innovative Materials, University of Wollongong, Wollongong, New South Wales 2525, Australia
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Silicene nanomeshes: bandgap opening by bond symmetry breaking and uniaxial strain. Sci Rep 2016; 6:20971. [PMID: 26860967 PMCID: PMC4748269 DOI: 10.1038/srep20971] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Accepted: 01/14/2016] [Indexed: 11/09/2022] Open
Abstract
Based on the first-principles calculations, we have investigated in detail the bandgap opening of silicene nanomeshes. Different to the mechanism of bandgap opening induced by the sublattice equivalence breaking, the method of degenerate perturbation through breaking the bond symmetry could split the π-like bands in the inversion symmetry preserved silicene nanomeshes, resulting into the πa1 − πa2 and πz1 − πz2 band sets with sizable energy intervals. Besides the bandgap opening in the nanomeshes with Dirac point being folded to Γ point, the split energy intervals are however apart away from Fermi level to leave the semimetal nature unchanged for the other nanomeshes with Dirac points located at opposite sides of Γ point as opposite pseudo spin wave valleys. A mass bandgap could be then opened at the aid of uniaxial strain to transfer the nanomesh to be semiconducting, whose width could be continuously enlarged until reaching its maximum Emax. Moreover, the Emax could also be tuned by controlling the defect density in silicene nanomeshes. These studies could contribute to the understanding of the bandgap engineering of silicene-based nanomaterials to call for further investigations on both theory and experiment.
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10
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Yaokawa R, Ohsuna T, Morishita T, Hayasaka Y, Spencer MJS, Nakano H. Monolayer-to-bilayer transformation of silicenes and their structural analysis. Nat Commun 2016; 7:10657. [PMID: 26847858 PMCID: PMC4748253 DOI: 10.1038/ncomms10657] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 01/06/2016] [Indexed: 11/21/2022] Open
Abstract
Silicene, a two-dimensional honeycomb network of silicon atoms like graphene, holds great potential as a key material in the next generation of electronics; however, its use in more demanding applications is prevented because of its instability under ambient conditions. Here we report three types of bilayer silicenes that form after treating calcium-intercalated monolayer silicene (CaSi2) with a BF4(-) -based ionic liquid. The bilayer silicenes that are obtained are sandwiched between planar crystals of CaF2 and/or CaSi2, with one of the bilayer silicenes being a new allotrope of silicon, containing four-, five- and six-membered sp(3) silicon rings. The number of unsaturated silicon bonds in the structure is reduced compared with monolayer silicene. Additionally, the bandgap opens to 1.08 eV and is indirect; this is in contrast to monolayer silicene which is a zero-gap semiconductor.
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Affiliation(s)
- Ritsuko Yaokawa
- TOYOTA Central R&D Labs, Inc., 41-1, Yokomichi, Nagakute, Aichi 480-1192, Japan
| | - Tetsu Ohsuna
- TOYOTA Central R&D Labs, Inc., 41-1, Yokomichi, Nagakute, Aichi 480-1192, Japan
| | - Tetsuya Morishita
- CD-FMat, National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan
| | - Yuichiro Hayasaka
- The Electron Microscopy Center, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan
| | | | - Hideyuki Nakano
- TOYOTA Central R&D Labs, Inc., 41-1, Yokomichi, Nagakute, Aichi 480-1192, Japan
- JST Presto, Kawaguchi 332-0012, Japan
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Houssa M, Dimoulas A, Molle A. Silicene: a review of recent experimental and theoretical investigations. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:253002. [PMID: 26045468 DOI: 10.1088/0953-8984/27/25/253002] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Silicene is the silicon counterpart of graphene, i.e. it consists in a single layer of Si atoms with a hexagonal arrangement. We present a review of recent theoretical and experimental works on this novel two dimensional material. We discuss first the structural, electronic and vibrational properties of free-standing silicene, as predicted from first-principles calculations. We next review theoretical studies on the interaction of silicene with different substrates. The growth and experimental characterization of silicene on Ag(1 1 1) is next discussed, providing insights into the different phases or atomic arrangements of silicene observed on this metallic surface, as well as on its electronic structure. Recent experimental findings about the likely formation of hexagonal Si nanosheets on MoS2 are also highlighted.
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Affiliation(s)
- M Houssa
- Department of Physics and Astronomy, University of Leuven, B-3001 Leuven, Belgium
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Berland K, Cooper VR, Lee K, Schröder E, Thonhauser T, Hyldgaard P, Lundqvist BI. van der Waals forces in density functional theory: a review of the vdW-DF method. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2015; 78:066501. [PMID: 25978530 DOI: 10.1088/0034-4885/78/6/066501] [Citation(s) in RCA: 304] [Impact Index Per Article: 33.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
A density functional theory (DFT) that accounts for van der Waals (vdW) interactions in condensed matter, materials physics, chemistry, and biology is reviewed. The insights that led to the construction of the Rutgers-Chalmers van der Waals density functional (vdW-DF) are presented with the aim of giving a historical perspective, while also emphasizing more recent efforts which have sought to improve its accuracy. In addition to technical details, we discuss a range of recent applications that illustrate the necessity of including dispersion interactions in DFT. This review highlights the value of the vdW-DF method as a general-purpose method, not only for dispersion bound systems, but also in densely packed systems where these types of interactions are traditionally thought to be negligible.
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Affiliation(s)
- Kristian Berland
- Centre for Materials Science and Nanotechnology, SMN, University of Oslo, NO-0318 Oslo, Norway. Microtechnology and Nanoscience, MC2, Chalmers University of Technology, SE-412 96 Göteborg, Sweden
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Friedlein R, Yamada-Takamura Y. Electronic properties of epitaxial silicene on diboride thin films. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:203201. [PMID: 25921233 DOI: 10.1088/0953-8984/27/20/203201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The Si counterpart of graphene—silicene—has partially similar but also unique electronic properties that relate to the presence of an extended π electronic system, the flexible crystal structure and the large spin-orbit coupling. Driven by predictions for exceptional electronic properties like the presence of massless charge carriers, the occurrence of the quantum Hall effect and perfect spin-filtering in free-standing, unreconstructed silicene, the recent experimental realization of largely sp(2)-hybridized, Si honeycomb lattices grown on a number of metallic substrates provided the opportunity for the systematic study of the electronic properties of epitaxial silicene phases. Following a discussion of theoretical predictions for free-standing silicene, we review properties of (√3 × √3)-reconstructed, epitaxial silicene phases but with the emphasis on the extensively studied case of silicene on ZrB2(0 0 0 1) thin films. As the experimental results show, the structural and electronic properties are highly interlinked and leave their fingerprint on the chemical states of individual Si atoms as revealed in core-level photoelectron spectra as well as in the valence electronic structure and low-energy interband transitions. With the critical role of substrates and of the chemical stability of epitaxial silicene highlighted, finally, benefits and challenges for any future silicene-based nanoelectronics are being put into perspective.
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Affiliation(s)
- Rainer Friedlein
- School of Materials Science, Japan Advanced Institute of Science and Technology (JAIST), 1-1, Asahidai, Nomi, Ishikawa 923-1292, Japan
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Enhanced thermoelectric efficiency of porous silicene nanoribbons. Sci Rep 2015; 5:9514. [PMID: 25820162 PMCID: PMC4377624 DOI: 10.1038/srep09514] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Accepted: 01/27/2015] [Indexed: 11/08/2022] Open
Abstract
There is a critical need to attain new sustainable materials for direct upgrade of waste heat to electrical energy via the thermoelectric effect. Here we demonstrate that the thermoelectric performance of silicene nanoribbons can be improved dramatically by introducing nanopores and tuning the Fermi energy. We predict that values of electronic thermoelectric figure of merit ZTe up to 160 are achievable, provided the Fermi energy is located approximately 100 meV above the charge neutrality point. Including the effect of phonons yields a value for the full figure of merit of ZT = 3.5. Furthermore the sign of the thermopower S can be varied with achievable values as high as S = +/− 500 μV/K. As a method of tuning the Fermi energy, we analyse the effect of doping the silicene with either a strong electron donor (TTF) or a strong electron acceptor (TCNQ) and demonstrate that adsorbed layers of the former increases ZTe to a value of 3.1, which is insensitive to temperature over the range 100 K – 400 K. This combination of a high, temperature-insensitive ZTe, and the ability to choose the sign of the thermopower identifies nanoporous silicene as an ideal thermoelectric material with the potential for unprecedented performance.
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Baba Y, Shimoyama I, Hirao N, Sekiguchi T. Structures of quasi-freestanding ultra-thin silicon films deposited on chemically inert surfaces. Chem Phys 2014. [DOI: 10.1016/j.chemphys.2014.09.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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