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Chiral phonons in two-dimensional materials
摘要： There has been growing interest in investigating chiral phonons since they are theoretically found and experimentally verified recently. In a magnetic system with time inversion symmetry breaking, phonon can have nonzero angular momentum, which makes a correction to the gyromagnetic ratio measured in the Einstein-de Haas Effect. Though total phonon angular momentum is zero in a nonmagnetic two-dimensional (2D) hexagonal system with space inversion symmetry breaking, phonons at high symmetry points of the Brillouin zone can have nonzero phonon angular momentum, which means they are chiral phonons. Chiral phonons decide selection rules in the electronic intervalley scattering, which has been experimentally verified in tungsten-diselenide monolayers very recently (Science 359, 579 (2018)). In this review, after a brief introduction of related background and some basic concepts, we mainly report recent progress of phonon angular momentum in magnetic systems and chiral phonon in nonmagnetic systems. We also review known experiments in verifications of the phonon chirality and finally conclude with an outlook of future developments.
关键词： two-dimensional materials,chiral phonons,phonon Hall effect,valleytronics,Einstein-de Haas Effect,phonon angular momentum
更新于2025-09-10 09:29:36
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Dewetting of monolayer water and isopropanol between MoS2 nanosheets
摘要： Understanding dewetting of solvent molecules confined to layered material (LM) interfaces is crucial to the synthesis of two-dimensional materials by liquid-phase exfoliation. Here, we examine dewetting behavior of water and isopropanol/water (IPA/H2O) mixtures between molybdenum disulfide (MoS2) membranes using molecular dynamics (MD) simulations. We find that a monolayer of water spontaneously ruptures into nanodroplets surrounded by dry regions. The average speed of receding dry patches is close to the speed of sound in air. In contrast, monolayer mixtures of IPA/H2O between MoS2 membranes slowly transform into percolating networks of nanoislands and nanochannels in which water molecules diffuse inside and IPA molecules stay at the periphery of islands and channels. These contrasting behaviors may explain why IPA/H2O mixtures are much more effective than H2O alone in weakening interlayer coupling and exfoliating MoS2 into atomically thin sheets.
关键词： molecular dynamics simulations,liquid-phase exfoliation,isopropanol/water mixtures,two-dimensional materials,layered material interfaces,dewetting,solvent molecules,MoS2 membranes
更新于2025-09-10 09:29:36
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Tensile mechanical properties and fracture behavior of monolayer InSe under axial tension
摘要： Based on a newly developed interatomic potential, the mechanical properties and fracture behavior of monolayer InSe are investigated by using the classical molecular dynamics method. We ?nd that monolayer InSe exhibits excellent mechanical properties comparing with other two-dimensional materials. Especially, it can sustain an axial tensile strain of 27% in the zigzag direction at room temperature 300 K. Furthermore, the numerical results indicate that the monolayer InSe has an isotropy in the mechanical behaviors with the Youngs modulus being about 43 N/m both in the armchair and zigzag directions. We also discuss the e?ects of temperature and strain rate on the mechanical properties of monolayer InSe and ?nd the high temperature-sensitivity. It’s found that the mechanical properties signi?cantly decrease as the increasing temperature. In contrast, the mechanical properties has a relatively weak dependence on the strain rate. As the strain rate increases from 0.0002 to 0.0008 ps?1, Young’s modulus nearly keeps a constant. The fracture stress and strain in armchair direction only increase by 3.6% and 8.3%, respectively.
关键词： Tensile strain,Monolayer InSe,Molecular dynamics simulation,Two-dimensional materials,Mechanical property
更新于2025-09-10 09:29:36
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Biological interactions of biocompatible and water-dispersed MoS2 nanosheets with bacteria and human cells
摘要： Two dimensional materials beyond graphene such as MoS2 and WS2 are novel and interesting class of materials whose unique physico-chemical properties can be exploited in applications ranging from leading edge nanoelectronics to the frontiers between biomedicine and biotechnology. To unravel the potential of TMD crystals in biomedicine, control over their production through green and scalable routes in biocompatible solvents is critically important. Furthermore, considering multiple applications of eco-friendly 2D dispersions and their potential impact onto live matter, their toxicity and antimicrobial activity still remain an open issue. Herein, we focus on the current demands of 2D TMDs and produce high-quality, few-layered and defect-free MoS2 nanosheets, exfoliated and dispersed in pure water, stabilized up to three weeks. Hence, we studied the impact of this material on human cells by investigating its interactions with three cell lines: two tumoral, MCF7 (breast cancer) and U937 (leukemia), and one normal, HaCaT (epithelium). We observed novel and intriguing results, exhibiting evident cytotoxic effect induced in the tumor cell lines, absent in the normal cells in the tested conditions. The antibacterial action of MoS2 nanosheets is then investigated against a very dangerous gram negative bacterium, such as two types of Salmonellas: ATCC 14028 and wild-type Salmonella typhimurium. Additionally, concentration and layer-dependent modulation of cytotoxic effect is found both on human cells and Salmonellas.
关键词： antibacterial activity,biocompatibility,MoS2 nanosheets,two-dimensional materials,cytotoxicity
更新于2025-09-10 09:29:36
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High-performance black phosphorus field-effect transistors with long-term air-stability
摘要： Two-dimensional layered materials (2DLMs) are of considerable interest for high-performance electronic devices for their unique electronic properties and atomically thin geometry. However, the atomically thin geometry makes their electronic properties highly susceptible to the environment changes. In particular, some 2DLMs (e.g., black phosphorus (BP) and SnSe2) are unstable and could rapidly degrade over time when exposed to ambient conditions. Therefore, the development of proper passivation schemes that can preserve the intrinsic properties and enhance their lifetime represents a key challenge for these atomically thin electronic materials. Herein we introduce a simple, non-disruptive and scalable van der Waals passivation approach by using organic thin films to simultaneously improve the performance and air stability of BP field-effect transistors (FETs). We show that dioctylbenzothienobenzothiophene (C8-BTBT) thin films can be readily deposited on BP via van der Waals epitaxy approach to protect BP against oxidation in ambient conditions over 20 days. Importantly, the non-covalent van der Waals interface between C8-BTBT and BP effectively preserves the intrinsic properties of BP, allowing us to demonstrate high-performance BP FETs with a record-high current density of 920 μA/um, hole drift velocity over 1 ⅹ 107 cm/s, and on/off ratio of 104~107 at room temperature. This approach is generally applicable to other unstable two-dimensional (2D) materials, defining a unique pathway to modulate their electronic properties and realize high-performance devices through hybrid heterojunctions.
关键词： black phosphorus,saturation velocity,saturation current density,two-dimensional materials,passivation,field effect transistors
更新于2025-09-10 09:29:36
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The Evolution of Two-Dimensional Mo <sub/> 1- <i>x</i> </sub> W <sub/><i>x</i> </sub> S <sub/>2</sub> Alloy-Based Vertical Heterostructures with Various Composition Ranges <i>via</i> Manipulating the Mo/W Precursors
摘要： Two-dimensional (2D) layered transition metal dichalcogenides (TMDCs), for example, MoS2 and WS2, are gaining widespread attention at present due to their distinct physical properties. Developing the deeper potential of 2D TMDCs demands fine spatial modulation of chemical compositions and electrical performance to produce desired heterostructures. In this study, we report a one-step chemical vapor deposition (CVD) synthesis of compositionally tunable WS2-Mo1-xWxS2 vertical heterostructures by adjusting the stacking sequence of Mo/W films as the precursors. Detailed Raman and photoluminescence analyses confirm that as-grown samples present clear structural and optical modulations. The evolution of these heterostructures with different composition ranges is discussed on the basis of the tunable vapor pressure. The present study provides an alternative strategy to facilitate the development of 2D semiconductor heterostructures, which is an essential step towards realizing functional electronics and optoelectronics.
关键词： Heterostructures,Optical properties,Two-dimensional materials,Chemical vapor deposition,Transition metal dichalcogenides
更新于2025-09-10 09:29:36
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Fast identification of crystalline orientation of anisotropic two-dimensional materials using scanning polarization modulation microscopy
摘要： In this work, we have demonstrated that scanning polarization modulation microscopy (SPMM) provides a fast method for the identification of crystalline orientation of anisotropic two-dimensional (2D) materials. Using home-built 532 nm excited transmission SPMM, we identified the crystalline orientation of 2D orthorhombic black phosphorus, monoclinal 1T0-MoTe2, and triclinic ReS2 by measuring signals in only two incident polarization directions. So, it took just a few seconds to identify the crystalline orientation of anisotropic 2D materials. Our studies revealed that the SPMM method could be applied to arbitrary anisotropic 2D materials when selecting a suitable wavelength.
关键词： black phosphorus,1T0-MoTe2,scanning polarization modulation microscopy,anisotropic two-dimensional materials,ReS2,crystalline orientation
更新于2025-09-10 09:29:36
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Revealing the Spectrum of Unknown Layered Materials with Super-Human Predictive Abilities
摘要： We discover the chemical composition of over 1000 materials that are likely to exhibit layered and two-dimensional phases but have yet to be synthesized. This includes two materials our calculations indicate can exist in distinct structures with different band gaps, expanding the short list of two-dimensional phase change materials. While databases of over 1000 layered materials have been reported, we provide the first full database of materials that are likely layered but yet to be synthesized, providing a roadmap for the synthesis community. We accomplish this by combining physics with machine learning on experimentally obtained data and verify a subset of candidates using density functional theory. We find our model performs five times better than practitioners in the field at identifying layered materials and is comparable or better than professional solid-state chemists. Finally, we find that semi-supervised learning can offer benefits for materials design where labels for some of the materials are unknown.
关键词： two-dimensional materials,machine learning,materials discovery,density functional theory,layered materials
更新于2025-09-09 09:28:46
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Two-Dimensional Electronics and Optoelectronics: Present and Future
摘要： Since the successful isolation of graphene a little over a decade ago, a wide variety of two-dimensional (2D) layered materials have been studied. They cover a broad spectrum of electronic properties, including metals, semimetals, semiconductors, and insulators. Many of these 2D materials have demonstrated promising potential for electronic and optoelectronic applications.
关键词： transition metal dichalcogenides,black phosphorus,optoelectronics,electronics,two-dimensional materials,graphene
更新于2025-09-09 09:28:46
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Band structure and giant Stark effect in two-dimensional transition-metal dichalcogenides
摘要： We present a comprehensive study of the electronic structures of 192 configurations of 39 stable, layered, transition-metal dichalcogenides using density-functional theory. We show detailed investigations of their monolayer, bilayer, and trilayer structures’ valence-band maxima, conduction-band minima, and band gap responses to transverse electric fields. We also report the critical fields where semiconductor-to-metal phase transitions occur. Our results show that band gap engineering by applying electric fields can be an effective strategy to modulate the electronic properties of transition-metal dichalcogenides for next-generation device applications.
关键词： two-dimensional materials,band structure,giant-Stark effect,density functional theory,electric field,transition metal dichalcogenides
更新于2025-09-09 09:28:46