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Hwang GC, Blom DA, Vogt T, Lee J, Choi HJ, Shao S, Ma Y, Lee Y. Pressure-driven phase transitions and reduction of dimensionality in 2D silicon nanosheets. Nat Commun 2018; 9:5412. [PMID: 30575737 PMCID: PMC6303324 DOI: 10.1038/s41467-018-07832-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Accepted: 11/27/2018] [Indexed: 11/22/2022] Open
Abstract
In-situ high-pressure synchrotron X-ray powder diffraction studies up to 21 GPa of CVD-grown silicon 2D-nanosheets establish that the structural phase transitions depend on size and shape. For sizes between 9.3(7) nm and 15.2(8) nm we observe an irreversible phase transition sequence from I (cubic) → II (tetragonal) → V (hexagonal) during pressure increase and during decompression below 8 GPa the emergence of an X-ray amorphous phase. High-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and atomic force microscopy (AFM) images of this X-ray amorphous phase reveal the formation of significant numbers of 1D nanowires with aspect ratios > 10, which are twinned and grow along the <111> direction. We discovered a reduction of dimensionality under pressure from a 2D morphology to a 1D wire in a material with a diamond structure. MD simulations indicate the reduction of thermal conductivity in such nanowires.
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Affiliation(s)
- Gil Chan Hwang
- Department of Earth System Sciences, Yonsei University, Seoul, 03722, Korea
| | - Douglas A Blom
- NanoCenter & Department of Chemical Engineering, University of South Carolina, Columbia, SC, 29208, USA
| | - Thomas Vogt
- NanoCenter & Department of Chemistry & Biochemistry, University of South Carolina, Columbia, SC, 29208, USA
| | - Jaejun Lee
- Department of Materials Science and Engineering, Yonsei University, Seoul, 03722, Korea
| | - Heon-Jin Choi
- Department of Materials Science and Engineering, Yonsei University, Seoul, 03722, Korea
| | - Sen Shao
- State Key Lab of Superhard Materials & Innovation Center for Computational Physics Methods and softwares, College of Physics, Jilin University, 130012, Changchun, China
| | - Yanming Ma
- State Key Lab of Superhard Materials & Innovation Center for Computational Physics Methods and softwares, College of Physics, Jilin University, 130012, Changchun, China
- International Center of Future Science, Jilin University, 130012, Changchun, China
| | - Yongjae Lee
- Department of Earth System Sciences, Yonsei University, Seoul, 03722, Korea.
- Center for High Pressure Science and Technology Advanced Research, 201203, Shanghai, China.
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Beltukov YM, Fusco C, Parshin DA, Tanguy A. Boson peak and Ioffe-Regel criterion in amorphous siliconlike materials: The effect of bond directionality. Phys Rev E 2016; 93:023006. [PMID: 26986404 DOI: 10.1103/physreve.93.023006] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Indexed: 06/05/2023]
Abstract
The vibrational properties of model amorphous materials are studied by combining complete analysis of the vibration modes, dynamical structure factor, and energy diffusivity with exact diagonalization of the dynamical matrix and the kernel polynomial method, which allows a study of very large system sizes. Different materials are studied that differ only by the bending rigidity of the interactions in a Stillinger-Weber modelization used to describe amorphous silicon. The local bending rigidity can thus be used as a control parameter, to tune the sound velocity together with local bonds directionality. It is shown that for all the systems studied, the upper limit of the Boson peak corresponds to the Ioffe-Regel criterion for transverse waves, as well as to a minimum of the diffusivity. The Boson peak is followed by a diffusivity's increase supported by longitudinal phonons. The Ioffe-Regel criterion for transverse waves corresponds to a common characteristic mean-free path of 5-7 Å (which is slightly bigger for longitudinal phonons), while the fine structure of the vibrational density of states is shown to be sensitive to the local bending rigidity.
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Affiliation(s)
- Y M Beltukov
- Ioffe Physical Technical Institute, 194021 St Petersburg, Russian Federation and Université Montpellier II, CNRS, Montpellier 34095, France
| | - C Fusco
- Université de Lyon, MATEIS, INSA-Lyon, CNRS UMR5510, F-69621, France and Institut Lumière Matière, UMR 5306 Université Lyon 1-CNRS, F-69622 Villeurbanne Cedex, France
| | - D A Parshin
- Saint Petersburg State Polytechnical University, 195251 Saint Petersburg, Russian Federation
| | - A Tanguy
- Université de Lyon, LaMCoS, INSA-Lyon, CNRS UMR5259, F-69621, France and Institut Lumière Matière, UMR 5306 Université Lyon 1-CNRS, F-69622 Villeurbanne Cedex, France
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Vasisht VV, Sastry S. Liquid-Liquid Phase Transition in Supercooled Silicon. LIQUID POLYMORPHISM 2013. [DOI: 10.1002/9781118540350.ch18] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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McMillan PF, Greaves GN, Wilson M, Wilding MC, Daisenberger D. Polyamorphism and Liquid-Liquid Phase Transitions in Amorphous Silicon and Supercooled Al 2O 3-Y 2O 3Liquids. LIQUID POLYMORPHISM 2013. [DOI: 10.1002/9781118540350.ch12] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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Garcez KMS, Antonelli A. Pressure effects on the transitions between disordered phases in supercooled liquid silicon. J Chem Phys 2011; 135:204508. [DOI: 10.1063/1.3663387] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Beye M, Sorgenfrei F, Schlotter WF, Wurth W, Föhlisch A. The liquid-liquid phase transition in silicon revealed by snapshots of valence electrons. Proc Natl Acad Sci U S A 2010; 107:16772-6. [PMID: 20805512 PMCID: PMC2947918 DOI: 10.1073/pnas.1006499107] [Citation(s) in RCA: 139] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The basis for the anomalies of water is still mysterious. Quite generally tetrahedrally coordinated systems, also silicon, show similar thermodynamic behavior but lack--like water--a thorough explanation. Proposed models--controversially discussed--explain the anomalies as a remainder of a first-order phase transition between high and low density liquid phases, buried deeply in the "no man's land"--a part of the supercooled liquid region where rapid crystallization prohibits any experimental access. Other explanations doubt the existence of the phase transition and its first-order nature. Here, we provide experimental evidence for the first-order-phase transition in silicon. With ultrashort optical pulses of femtosecond duration we instantaneously heat the electronic system of silicon while the atomic structure as defined by the much heavier nuclear system remains initially unchanged. Only on a picosecond time scale the energy is transferred into the atomic lattice providing the energy to drive the phase transitions. With femtosecond X-ray pulses from FLASH, the free-electron laser at Hamburg, we follow the evolution of the valence electronic structure during this process. As the relevant phases are easily distinguishable in their electronic structure, we track how silicon melts into the low-density-liquid phase while a second phase transition into the high-density-liquid phase only occurs after the latent heat for the first-order phase transition has been transferred to the atomic structure. Proving the existence of the liquid-liquid phase transition in silicon, the hypothesized liquid-liquid scenario for water is strongly supported.
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Affiliation(s)
- Martin Beye
- Institut für Experimentalphysik, Universität Hamburg and Centre for Free-Electron Laser Science, Luruper Chaussee 149, 22761 Hamburg, Germany.
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McMillan PF, Wilson M, Daisenberger D, Machon D. A density-driven phase transition between semiconducting and metallic polyamorphs of silicon. NATURE MATERIALS 2005; 4:680-4. [PMID: 16113681 DOI: 10.1038/nmat1458] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2005] [Accepted: 06/29/2005] [Indexed: 05/04/2023]
Abstract
Amorphous and crystalline forms of silicon are well-known, tetrahedrally coordinated semiconductors. High-pressure studies have revealed extensive polymorphism among various metallic crystal structures containing atoms in six-, eight- and 12-fold coordination. Melting silicon at ambient or high pressure results in a conducting liquid, in which the average coordination is greater than four (ref. 3). This liquid cannot normally be quenched to a glass, because of rapid crystallization to the diamond-structured semiconductor. Solid amorphous silicon is obtained by synthesis routes such as chemical or physical vapour deposition that result in a tetrahedrally bonded semiconducting state. It has long been speculated that the amorphous solid and the liquid could represent two polymorphic forms of the amorphous state that are linked by density- or entropy-driven transformations. Such polyamorphic transitions are recognized to occur among several different types of liquid and glassy systems. Here we present experimental evidence for the occurrence of a density-driven polyamorphic transition between semiconducting and metallic forms of solid amorphous silicon. The experiments are combined with molecular dynamics simulations that map the behaviour of the amorphous solid on to that of the liquid state.
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Affiliation(s)
- Paul F McMillan
- Department of Chemistry and Materials Chemistry Centre, Christopher Ingold Laboratories, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
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Morishita T. Anomalous diffusivity in supercooled liquid silicon under pressure. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2005; 72:021201. [PMID: 16196547 DOI: 10.1103/physreve.72.021201] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2005] [Indexed: 05/04/2023]
Abstract
We perform isothermal-isobaric first-principles molecular-dynamics simulations to investigate the dynamics of liquid silicon (l-Si) under pressure. We find that the self-diffusion coefficient increases with increasing pressure in the deeply supercooled state. This anomalous diffusivity is attributed to the formation of locally tetrahedral configurations which on average reduces the diffusivity at low pressures. Densification hinders the formation of the tetrahedral configurations, thus the diffusivity increases with increasing pressure. The tetrahedral configurations frequently formed at low pressures may be viewed as fragments of the low-density form of l-Si . It is therefore conceivable that transformations between two distinct liquids, low- and high-density liquids, locally occur in deeply supercooled l-Si . The present findings indicate the profound generality of the dynamics in liquids with a tetrahedral network such as water.
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Affiliation(s)
- Tetsuya Morishita
- Research Institute for Computational Sciences (RICS), National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan.
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