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Kopciuszyński M, Stȩpniak-Dybala A, Zdyb R, Krawiec M. Emergent Dirac Fermions in Epitaxial Planar Silicene Heterostructure. NANO LETTERS 2024; 24:2175-2180. [PMID: 38181506 PMCID: PMC10885205 DOI: 10.1021/acs.nanolett.3c04046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2024]
Abstract
Silicene, a single layer of Si atoms, shares many remarkable electronic properties with graphene. So far, silicene has been synthesized in its epitaxial form on a few surfaces of solids. Thus, the problem of silicene-substrate interaction appears, which usually depresses the original electronic behavior but may trigger properties superior to those of bare components. We report the direct observation of robust Dirac-dispersed bands in epitaxial silicene grown on Au(111) films deposited on Si(111). By performing in-depth angle-resolved photoemission spectroscopy measurements, we reveal three pairs of one-dimensional bands with linear dispersion running in three different directions of an otherwise two-dimensional system. By combining these results with first-principles calculations, we explore the nature of these bands and point to strong interaction between subsystems forming a complex Si-Au heterostructure. These findings emphasize the essential role of interfacial coupling and open a unique materials platform for exploring exotic quantum phenomena and applications in future-generation nanoelectronics.
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Affiliation(s)
- Marek Kopciuszyński
- Institute of Physics, M. Curie-Sklodowska University, Pl. M. Curie-Skłodowskiej 1, 20-031 Lublin, Poland
| | - Agnieszka Stȩpniak-Dybala
- Institute of Physics, M. Curie-Sklodowska University, Pl. M. Curie-Skłodowskiej 1, 20-031 Lublin, Poland
| | - Ryszard Zdyb
- Institute of Physics, M. Curie-Sklodowska University, Pl. M. Curie-Skłodowskiej 1, 20-031 Lublin, Poland
| | - Mariusz Krawiec
- Institute of Physics, M. Curie-Sklodowska University, Pl. M. Curie-Skłodowskiej 1, 20-031 Lublin, Poland
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Dhungana DS, Massetti C, Martella C, Grazianetti C, Molle A. All-around encapsulation of silicene. NANOSCALE HORIZONS 2023; 8:1428-1434. [PMID: 37610170 PMCID: PMC10521910 DOI: 10.1039/d3nh00309d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 07/28/2023] [Indexed: 08/24/2023]
Abstract
Silicene or the two-dimensional (2D) graphene-like silicon allotrope has recently emerged as a promising candidate for various applications in nanotechnology. However, concerns on the silicene stability still persist to date and need to be addressed aiming at the fabrication of competing and durable silicene-based devices. Here, we present an all-around encapsulation methodology beyond the current state-of-the-art silicene configuration, namely silicene sandwiched in between a capping layer (e.g., Al2O3) and the supporting substrate (e.g., Ag). In this framework, the insertion of one or two sacrificial 2D Sn layers enables the realization of different atomically thin encapsulation schemes, preserving the pristine properties of silicene while decoupling it from the growth template. On one hand, the epitaxy of a 2D Sn layer before silicene allows for the removal of the Ag substrate with no effect on silicene which in turn can be easily gated, for example, with an oxide layer on its top face. On the other hand, a full 2D encapsulation scheme, where top and bottom faces of silicene are protected by 2D Sn layers, gives rise to an atomically thin and cm2-scaled membrane preventing degradation of silicene for months. Both schemes thus constitute an advancement for the silicene stability and encapsulation in ambient conditions, paving the way to further exploitation in flexible electronics and photonics.
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Affiliation(s)
- Daya S Dhungana
- CNR-IMM, Unit of Agrate Brianza, via C. Olivetti 2, Agrate Brianza, I-20864, Italy.
| | - Chiara Massetti
- CNR-IMM, Unit of Agrate Brianza, via C. Olivetti 2, Agrate Brianza, I-20864, Italy.
- Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, Via Cozzi 53, Milano, I-20125, Italy
| | - Christian Martella
- CNR-IMM, Unit of Agrate Brianza, via C. Olivetti 2, Agrate Brianza, I-20864, Italy.
| | - Carlo Grazianetti
- CNR-IMM, Unit of Agrate Brianza, via C. Olivetti 2, Agrate Brianza, I-20864, Italy.
| | - Alessandro Molle
- CNR-IMM, Unit of Agrate Brianza, via C. Olivetti 2, Agrate Brianza, I-20864, Italy.
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Masson L, Prévot G. Epitaxial growth and structural properties of silicene and other 2D allotropes of Si. NANOSCALE ADVANCES 2023; 5:1574-1599. [PMID: 36926561 PMCID: PMC10012843 DOI: 10.1039/d2na00808d] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 02/13/2023] [Indexed: 06/18/2023]
Abstract
Since the breakthrough of graphene, considerable efforts have been made to search for two-dimensional (2D) materials composed of other group 14 elements, in particular silicon and germanium, due to their valence electronic configuration similar to that of carbon and their widespread use in the semiconductor industry. Silicene, the silicon counterpart of graphene, has been particularly studied, both theoretically and experimentally. Theoretical studies were the first to predict a low-buckled honeycomb structure for free-standing silicene possessing most of the outstanding electronic properties of graphene. From an experimental point of view, as no layered structure analogous to graphite exists for silicon, the synthesis of silicene requires the development of alternative methods to exfoliation. Epitaxial growth of silicon on various substrates has been widely exploited in attempts to form 2D Si honeycomb structures. In this article, we provide a comprehensive state-of-the-art review focusing on the different epitaxial systems reported in the literature, some of which having generated controversy and long debates. In the search for the synthesis of 2D Si honeycomb structures, other 2D allotropes of Si have been discovered and will also be presented in this review. Finally, with a view to applications, we discuss the reactivity and air-stability of silicene as well as the strategy devised to decouple epitaxial silicene from the underlying surface and its transfer to a target substrate.
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Affiliation(s)
| | - Geoffroy Prévot
- Sorbonne Université, CNRS, Institut des NanoSciences de Paris, INSP F-75005 Paris France
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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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Ben Jabra Z, Abel M, Fabbri F, Aqua JN, Koudia M, Michon A, Castrucci P, Ronda A, Vach H, De Crescenzi M, Berbezier I. Van der Waals Heteroepitaxy of Air-Stable Quasi-Free-Standing Silicene Layers on CVD Epitaxial Graphene/6H-SiC. ACS NANO 2022; 16:5920-5931. [PMID: 35294163 DOI: 10.1021/acsnano.1c11122] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Graphene, consisting of an inert, thermally stable material with an atomically flat, dangling-bond-free surface, is by essence an ideal template layer for van der Waals heteroepitaxy of two-dimensional materials such as silicene. However, depending on the synthesis method and growth parameters, graphene (Gr) substrates could exhibit, on a single sample, various surface structures, thicknesses, defects, and step heights. These structures noticeably affect the growth mode of epitaxial layers, e.g., turning the layer-by-layer growth into the Volmer-Weber growth promoted by defect-assisted nucleation. In this work, the growth of silicon on chemical vapor deposited epitaxial Gr (1 ML Gr/1 ML Gr buffer) on a 6H-SiC(0001) substrate is investigated by a combination of atomic force microscopy (AFM), scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Raman spectroscopy measurements. It is shown that the perfect control of full-scale almost defect-free 1 ML Gr with a single surface structure and the ultraclean conditions for molecular beam epitaxy deposition of silicon represent key prerequisites for ensuring the growth of extended silicene sheets on epitaxial graphene. At low coverages, the deposition of Si produces large silicene sheets (some hundreds of nanometers large) attested by both AFM and SEM observations and the onset of a Raman peak at 560 cm-1, very close to the theoretical value of 570 cm-1 calculated for free-standing silicene. This vibrational mode at 560 cm-1 represents the highest ever experimentally measured value and is representative of quasi-free-standing silicene with almost no interaction with inert nonmetal substrates. From a coverage rate of 1 ML, the silicene sheets disappear at the expense of 3D Si dendritic islands whose density, size, and thickness increase with the deposited thickness. From this coverage, the Raman mode assigned to quasi-free-standing silicene totally vanishes, and the 2D flakes of silicene are no longer observed by AFM. The experimental results are in very good agreement with the results of kinetic Monte Carlo simulations that rationalize the initial flake growth in solid-state dewetting conditions, followed by the growth of ridges surrounding and eventually covering the 2D flakes. A full description of the growth mechanism is given. This study, which covers a wide range of growth parameters, challenges recent results stating the impossibility to grow silicene on a carbon inert surface and is very promising for large-scale silicene growth. It shows that silicene growth can be achieved using perfectly controlled and ultraclean deposition conditions and an almost defect-free Gr substrate.
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Affiliation(s)
| | - Mathieu Abel
- Aix Marseille University, CNRS, IM2NP, Marseille 13397, France
| | - Filippo Fabbri
- NEST, Istituto Nanoscienze-CNR, Scuola Normale Superiore, Piazza San Silvestro 12, 56127 Pisa, Italy
| | - Jean-Noel Aqua
- Institut des Nanosciences de Paris, Sorbonne Université, CNRS, INSP, UMR 7588, 75005 Paris, France
| | - Mathieu Koudia
- Aix Marseille University, CNRS, IM2NP, Marseille 13397, France
| | - Adrien Michon
- Université Côte d'Azur, CNRS, CRHEA, Valbonne 06560, France
| | - Paola Castrucci
- Dipartimento di Fisica, Università di Roma Tor Vergata, Roma 00133, Italy
| | - Antoine Ronda
- Aix Marseille University, CNRS, IM2NP, Marseille 13397, France
| | - Holger Vach
- LPICM, CNRS, Ecole Polytechnique, IP Paris, Palaiseau 91128, France
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Krawiec M, Stępniak-Dybala A, Bobyk A, Zdyb R. Magnetism in Au-Supported Planar Silicene. NANOMATERIALS 2021; 11:nano11102568. [PMID: 34685008 PMCID: PMC8540306 DOI: 10.3390/nano11102568] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 09/19/2021] [Accepted: 09/25/2021] [Indexed: 01/10/2023]
Abstract
The adsorption and substitution of transition metal atoms (Fe and Co) on Au-supported planar silicene have been studied by means of first-principles density functional theory calculations. The structural, energetic and magnetic properties have been analyzed. Both dopants favor the same atomic configurations with rather strong binding energies and noticeable charge transfer. The adsorption of Fe and Co atoms do not alter the magnetic properties of Au-supported planar silicene, unless a full layer of adsorbate is completed. In the case of substituted system only Fe is able to produce magnetic ground state. The Fe-doped Au-supported planar silicene is a ferromagnetic structure with local antiferromagnetic ordering. The present study is the very first and promising attempt towards ferromagnetic epitaxial planar silicene and points to the importance of the substrate in structural and magnetic properties of silicene.
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Affiliation(s)
- Mariusz Krawiec
- Institute of Physics, M. Curie-Sklodowska University, Pl. M. Curie-Skłodowskiej 1, 20-031 Lublin, Poland; (A.S.-D.); (R.Z.)
- Correspondence: ; Tel.: +48-81-537-6146
| | - Agnieszka Stępniak-Dybala
- Institute of Physics, M. Curie-Sklodowska University, Pl. M. Curie-Skłodowskiej 1, 20-031 Lublin, Poland; (A.S.-D.); (R.Z.)
| | - Andrzej Bobyk
- Institute of Computer Science, M. Curie-Sklodowska University, ul. Akademicka 9, 20-031 Lublin, Poland;
| | - Ryszard Zdyb
- Institute of Physics, M. Curie-Sklodowska University, Pl. M. Curie-Skłodowskiej 1, 20-031 Lublin, Poland; (A.S.-D.); (R.Z.)
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