Materials Science › Materials Chemistry

2D Materials and Applications

Works Count: 54181

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Description

This cluster of papers covers a wide range of research on two-dimensional materials, including semiconducting transition metal dichalcogenides like monolayer MoS2 and black phosphorus. It explores topics such as van der Waals heterostructures, excitonic effects, photoluminescence, electronic structure, and the development of optoelectronic devices based on atomically thin semiconductors.

Keywords

Two-Dimensional Materials; Van der Waals Heterostructures; Semiconducting Transition Metal Dichalcogenides; Monolayer MoS2; Black Phosphorus; Excitonic Effects; Photoluminescence; Electronic Structure; Optoelectronic Devices; Atomically Thin Semiconductors

Rediscovering black phosphorus as an anisotropic layered material for optoelectronics and electronics

2014-07-21

Fengnian Xia , Han Wang , Yichen Jia

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Layer-controlled band gap and anisotropic excitons in few-layer black phosphorus

2014-06-26

Vy Tran , Ryan Soklaski , Yufeng Liang +1 more

We report the quasiparticle band gap, excitons, and highly anisotropic optical responses of few-layer black phosphorous (phosphorene). It is shown that these new materials exhibit unique many-electron effects; the electronic … We report the quasiparticle band gap, excitons, and highly anisotropic optical responses of few-layer black phosphorous (phosphorene). It is shown that these new materials exhibit unique many-electron effects; the electronic structures are dispersive essentially along one dimension, leading to particularly enhanced self-energy corrections and excitonic effects. Additionally, within a wide energy range, including infrared light and part of visible light, few-layer black phosphorous absorbs light polarized along the structure's armchair direction and is transparent to light polarized along the zigzag direction, making them viable linear polarizers for applications. Finally, the number of phosphorene layers included in the stack controls the material's band gap, optical absorption spectrum, and anisotropic polarization energy-window across a wide range.

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Ultrasensitive photodetectors based on monolayer MoS2

2013-06-09

Oriol Lopez-Sanchez , Dominik Lembke , Metin Kayci +2 more

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Grains and grain boundaries in highly crystalline monolayer molybdenum disulphide

2013-05-03

Arend M. van der Zande , Pinshane Y. Huang , Daniel Chenet +7 more

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Two-Dimensional Nanosheets Produced by Liquid Exfoliation of Layered Materials

2011-02-03

Jonathan N. Coleman , Mustafa Lotya , Arlene O’Neill +7 more

If they could be easily exfoliated, layered materials would become a diverse source of two-dimensional crystals whose properties would be useful in applications ranging from electronics to energy storage. We … If they could be easily exfoliated, layered materials would become a diverse source of two-dimensional crystals whose properties would be useful in applications ranging from electronics to energy storage. We show that layered compounds such as MoS(2), WS(2), MoSe(2), MoTe(2), TaSe(2), NbSe(2), NiTe(2), BN, and Bi(2)Te(3) can be efficiently dispersed in common solvents and can be deposited as individual flakes or formed into films. Electron microscopy strongly suggests that the material is exfoliated into individual layers. By blending this material with suspensions of other nanomaterials or polymer solutions, we can prepare hybrid dispersions or composites, which can be cast into films. We show that WS(2) and MoS(2) effectively reinforce polymers, whereas WS(2)/carbon nanotube hybrid films have high conductivity, leading to promising thermoelectric properties.

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High Performance Multilayer MoS2 Transistors with Scandium Contacts

2012-12-14

Saptarshi Das , Hong-Yan Chen , Ashish Verma Penumatcha +1 more

While there has been growing interest in two-dimensional (2-D) crystals other than graphene, evaluating their potential usefulness for electronic applications is still in its infancy due to the lack of … While there has been growing interest in two-dimensional (2-D) crystals other than graphene, evaluating their potential usefulness for electronic applications is still in its infancy due to the lack of a complete picture of their performance potential. The focus of this article is on contacts. We demonstrate that through a proper understanding and design of source/drain contacts and the right choice of number of MoS(2) layers the excellent intrinsic properties of this 2-D material can be harvested. Using scandium contacts on 10-nm-thick exfoliated MoS(2) flakes that are covered by a 15 nm Al(2)O(3) film, high effective mobilities of 700 cm(2)/(V s) are achieved at room temperature. This breakthrough is largely attributed to the fact that we succeeded in eliminating contact resistance effects that limited the device performance in the past unrecognized. In fact, the apparent linear dependence of current on drain voltage had mislead researchers to believe that a truly Ohmic contact had already been achieved, a misconception that we also elucidate in the present article.

Vertical and in-plane heterostructures from WS2/MoS2 monolayers

2014-09-26

Yongji Gong , Junhao Lin , Xingli Wang +7 more

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Spin and pseudospins in layered transition metal dichalcogenides

2014-04-30

Xiaodong Xu , Wang Yao , Di Xiao +1 more

Two-dimensional material nanophotonics

2014-11-27

Fengnian Xia , Han Wang , Di Xiao +2 more

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Photoluminescence from Chemically Exfoliated MoS2

2011-10-28

Goki Eda , Hisato Yamaguchi , Damien Voiry +3 more

A two-dimensional crystal of molybdenum disulfide (MoS2) monolayer is a photoluminescent direct gap semiconductor in striking contrast to its bulk counterpart. Exfoliation of bulk MoS2 via Li intercalation is an … A two-dimensional crystal of molybdenum disulfide (MoS2) monolayer is a photoluminescent direct gap semiconductor in striking contrast to its bulk counterpart. Exfoliation of bulk MoS2 via Li intercalation is an attractive route to large-scale synthesis of monolayer crystals. However, this method results in loss of pristine semiconducting properties of MoS2 due to structural changes that occur during Li intercalation. Here, we report structural and electronic properties of chemically exfoliated MoS2. The metastable metallic phase that emerges from Li intercalation was found to dominate the properties of as-exfoliated material, but mild annealing leads to gradual restoration of the semiconducting phase. Above an annealing temperature of 300 °C, chemically exfoliated MoS2 exhibit prominent band gap photoluminescence, similar to mechanically exfoliated monolayers, indicating that their semiconducting properties are largely restored.

The chemistry of two-dimensional layered transition metal dichalcogenide nanosheets

2013-03-20

Manish Chhowalla , Hyeon Suk Shin , Goki Eda +3 more

Exciton Binding Energy and Nonhydrogenic Rydberg Series in Monolayer <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>WS</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

2014-08-13

Alexey Chernikov , Timothy C. Berkelbach , Heather M. Hill +6 more

We have experimentally determined the energies of the ground and first four excited excitonic states of the fundamental optical transition in monolayer WS2, a model system for the growing class … We have experimentally determined the energies of the ground and first four excited excitonic states of the fundamental optical transition in monolayer WS2, a model system for the growing class of atomically thin two-dimensional semiconductor crystals. From the spectra, we establish a large exciton binding energy of 0.32 eV and a pronounced deviation from the usual hydrogenic Rydberg series of energy levels of the excitonic states. We explain both of these results using a microscopic theory in which the non-local nature of the effective dielectric screening modifies the functional form of the Coulomb interaction. These strong but unconventional electron-hole interactions are expected to be ubiquitous in atomically thin materials.

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Atomically Thin<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>MoS</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>: A New Direct-Gap Semiconductor

2010-09-24

Kin Fai Mak , Changgu Lee , James Hone +2 more

The electronic properties of ultrathin crystals of molybdenum disulfide consisting of $N=1,2,\dots{},6$ S-Mo-S monolayers have been investigated by optical spectroscopy. Through characterization by absorption, photoluminescence, and photoconductivity spectroscopy, we trace … The electronic properties of ultrathin crystals of molybdenum disulfide consisting of $N=1,2,\dots{},6$ S-Mo-S monolayers have been investigated by optical spectroscopy. Through characterization by absorption, photoluminescence, and photoconductivity spectroscopy, we trace the effect of quantum confinement on the material's electronic structure. With decreasing thickness, the indirect band gap, which lies below the direct gap in the bulk material, shifts upwards in energy by more than 0.6 eV. This leads to a crossover to a direct-gap material in the limit of the single monolayer. Unlike the bulk material, the ${\mathrm{MoS}}_{2}$ monolayer emits light strongly. The freestanding monolayer exhibits an increase in luminescence quantum efficiency by more than a factor of ${10}^{4}$ compared with the bulk material.

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Progress, Challenges, and Opportunities in Two-Dimensional Materials Beyond Graphene

2013-03-07

Sheneve Butler , Shawna Hollen , Linyou Cao +7 more

Graphene's success has shown that it is possible to create stable, single and few-atom-thick layers of van der Waals materials, and also that these materials can exhibit fascinating and technologically … Graphene's success has shown that it is possible to create stable, single and few-atom-thick layers of van der Waals materials, and also that these materials can exhibit fascinating and technologically useful properties. Here we review the state-of-the-art of 2D materials beyond graphene. Initially, we will outline the different chemical classes of 2D materials and discuss the various strategies to prepare single-layer, few-layer, and multilayer assembly materials in solution, on substrates, and on the wafer scale. Additionally, we present an experimental guide for identifying and characterizing single-layer-thick materials, as well as outlining emerging techniques that yield both local and global information. We describe the differences that occur in the electronic structure between the bulk and the single layer and discuss various methods of tuning their electronic properties by manipulating the surface. Finally, we highlight the properties and advantages of single-, few-, and many-layer 2D materials in field-effect transistors, spin- and valley-tronics, thermoelectrics, and topological insulators, among many other applications.

High-mobility transport anisotropy and linear dichroism in few-layer black phosphorus

2014-07-21

Jingsi Qiao , Xianghua Kong , Zhi-Xin Hu +2 more

Two-dimensional crystals are emerging materials for nanoelectronics. Development of the field requires candidate systems with both a high carrier mobility and, in contrast to graphene, a sufficiently large electronic bandgap. … Two-dimensional crystals are emerging materials for nanoelectronics. Development of the field requires candidate systems with both a high carrier mobility and, in contrast to graphene, a sufficiently large electronic bandgap. Here we present a detailed theoretical investigation of the atomic and electronic structure of few-layer black phosphorus (BP) to predict its electrical and optical properties. This system has a direct bandgap, tunable from 1.51 eV for a monolayer to 0.59 eV for a five-layer sample. We predict that the mobilities are hole-dominated, rather high and highly anisotropic. The monolayer is exceptional in having an extremely high hole mobility (of order 10,000 cm2 V−1 s−1) and anomalous elastic properties which reverse the anisotropy. Light absorption spectra indicate linear dichroism between perpendicular in-plane directions, which allows optical determination of the crystalline orientation and optical activation of the anisotropic transport properties. These results make few-layer BP a promising candidate for future electronics. Two-dimensional (2D) materials with a large electronic bandgap in addition to high carrier mobility are required for future nanoelectronics. Here, the authors present a theoretical investigation of black phosphorous, a new category of 2D semiconductor with high potential for nanoelectronic applications.

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Tightly bound trions in monolayer MoS2

2012-11-30

Kin Fai Mak , Keliang He , Changgu Lee +4 more

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The transition metal dichalcogenides discussion and interpretation of the observed optical, electrical and structural properties

1969-05-01

J. A. Wilson , A. D. Yoffe

Abstract The transition metal dichalcogenides are about 60 in number. Two-thirds of these assume layer structures. Crystals of such materials can be cleaved down to less than 1000 Å and … Abstract The transition metal dichalcogenides are about 60 in number. Two-thirds of these assume layer structures. Crystals of such materials can be cleaved down to less than 1000 Å and are then transparent in the region of direct band-to-band transitions. The transmission spectra of the family have been correlated group by group with the wide range of electrical and structural data available to yield useful working band models that are in accord with a molecular orbital approach. Several special topics have arisen; these include exciton screening, d-band formation, and the metal/insulator transition; also magnetism and superconductivity in such compounds. High pressure work seems to offer the possibility for testing the recent theory of excitonic insulators.

Coupled Spin and Valley Physics in Monolayers of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>MoS</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>and Other Group-VI Dichalcogenides

2012-05-07

Di Xiao , Gui‐Bin Liu , Wanxiang Feng +2 more

We show that inversion symmetry breaking together with spin-orbit coupling leads to coupled spin and valley physics in monolayers of ${\mathrm{MoS}}_{2}$ and other group-VI dichalcogenides, making possible controls of spin … We show that inversion symmetry breaking together with spin-orbit coupling leads to coupled spin and valley physics in monolayers of ${\mathrm{MoS}}_{2}$ and other group-VI dichalcogenides, making possible controls of spin and valley in these 2D materials. The spin-valley coupling at the valence-band edges suppresses spin and valley relaxation, as flip of each index alone is forbidden by the valley-contrasting spin splitting. Valley Hall and spin Hall effects coexist in both electron-doped and hole-doped systems. Optical interband transitions have frequency-dependent polarization selection rules which allow selective photoexcitation of carriers with various combination of valley and spin indices. Photoinduced spin Hall and valley Hall effects can generate long lived spin and valley accumulations on sample boundaries. The physics discussed here provides a route towards the integration of valleytronics and spintronics in multivalley materials with strong spin-orbit coupling and inversion symmetry breaking.

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Synthesis of Large‐Area MoS2 Atomic Layers with Chemical Vapor Deposition

2012-03-30

Yi‐Hsien Lee , Xinquan Zhang , Wenjing Zhang +7 more

Large-area MoS(2) atomic layers are synthesized on SiO(2) substrates by chemical vapor deposition using MoO(3) and S powders as the reactants. Optical, microscopic and electrical measurements suggest that the synthetic … Large-area MoS(2) atomic layers are synthesized on SiO(2) substrates by chemical vapor deposition using MoO(3) and S powders as the reactants. Optical, microscopic and electrical measurements suggest that the synthetic process leads to the growth of MoS(2) monolayer. The TEM images verify that the synthesized MoS(2) sheets are highly crystalline.

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Black phosphorus field-effect transistors

2014-03-02

Likai Li , Yijun Yu , Guo Jun Ye +6 more

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From Bulk to Monolayer MoS2: Evolution of Raman Scattering

2012-01-31

Hong Li , Qing Zhang , Chin Chong Yap +4 more

Abstract Molybdenum disulfide (MoS 2 ) is systematically studied using Raman spectroscopy with ultraviolet and visible laser lines. It is shown that only the Raman frequencies of $ E_{2{\rm g}}^1 … Abstract Molybdenum disulfide (MoS 2 ) is systematically studied using Raman spectroscopy with ultraviolet and visible laser lines. It is shown that only the Raman frequencies of $ E_{2{\rm g}}^1 $ and $ A_{{\rm 1g}}^{} $ peaks vary monotonously with the layer number of ultrathin MoS 2 flakes, while intensities or widths of the peaks vary arbitrarily. The coupling between electronic transitions and phonons are found to become weaker when the layer number of MoS 2 decreases, attributed to the increased electronic transition energies or elongated intralayer atomic bonds in ultrathin MoS 2 . The asymmetric Raman peak at 454 cm −1 , which has been regarded as the overtone of longitudinal optical M phonons in bulk MoS 2 , is actually a combinational band involving a longitudinal acoustic mode (LA(M)) and an optical mode ( $ A_{{\rm 2u}}^{} $ ). Our findings suggest a clear evolution of the coupling between electronic transition and phonon when MoS 2 is scaled down from three‐ to two‐dimensional geometry.

Synthesis of MoS2 and MoSe2 Films with Vertically Aligned Layers

2013-02-06

Desheng Kong , Haotian Wang , J. Judy +4 more

Layered materials consist of molecular layers stacked together by weak interlayer interactions. They often crystallize to form atomically smooth thin films, nanotubes, and platelet or fullerene-like nanoparticles due to the … Layered materials consist of molecular layers stacked together by weak interlayer interactions. They often crystallize to form atomically smooth thin films, nanotubes, and platelet or fullerene-like nanoparticles due to the anisotropic bonding. Structures that predominately expose edges of the layers exhibit high surface energy and are often considered unstable. In this communication, we present a synthesis process to grow MoS2 and MoSe2 thin films with vertically aligned layers, thereby maximally exposing the edges on the film surface. Such edge-terminated films are metastable structures of MoS2 and MoSe2, which may find applications in diverse catalytic reactions. We have confirmed their catalytic activity in a hydrogen evolution reaction (HER), in which the exchange current density correlates directly with the density of the exposed edge sites.

Liquid Exfoliation of Layered Materials

2013-06-20

Valeria Nicolosi , Manish Chhowalla , Mercouri G. Kanatzidis +2 more

Background Since at least 400 C.E., when the Mayans first used layered clays to make dyes, people have been harnessing the properties of layered materials. This gradually developed into scientific … Background Since at least 400 C.E., when the Mayans first used layered clays to make dyes, people have been harnessing the properties of layered materials. This gradually developed into scientific research, leading to the elucidation of the laminar structure of layered materials, detailed understanding of their properties, and eventually experiments to exfoliate or delaminate them into individual, atomically thin nanosheets. This culminated in the discovery of graphene, resulting in a new explosion of interest in two-dimensional materials. Layered materials consist of two-dimensional platelets weakly stacked to form three-dimensional structures. The archetypal example is graphite, which consists of stacked graphene monolayers. However, there are many others: from MoS 2 and layered clays to more exotic examples such as MoO 3 , GaTe, and Bi 2 Se 3 . These materials display a wide range of electronic, optical, mechanical, and electrochemical properties. Over the past decade, a number of methods have been developed to exfoliate layered materials in order to produce monolayer nanosheets. Such exfoliation creates extremely high-aspect-ratio nanosheets with enormous surface area, which are ideal for applications that require surface activity. More importantly, however, the two-dimensional confinement of electrons upon exfoliation leads to unprecedented optical and electrical properties. Advances An important advance has been the discovery that layered crystals can be exfoliated in liquids. There are a number of methods to do this that involve oxidation, ion intercalation/exchange, or surface passivation by solvents. However, all result in liquid dispersions containing large quantities of nanosheets. This brings considerable advantages: Liquid exfoliation allows the formation of thin films and composites, is potentially scaleable, and may facilitate processing by using standard technologies such as reel-to-reel manufacturing. Although much work has focused on liquid exfoliation of graphene, such processes have also been demonstrated for a host of other materials, including MoS 2 and related structures, layered oxides, and clays. The resultant liquid dispersions have been formed into films, hybrids, and composites for a range of applications. Outlook There is little doubt that the main advances are in the future. Multifunctional composites based on metal and polymer matrices will be developed that will result in enhanced mechanical, electrical, and barrier properties. Applications in energy generation and storage will abound, with layered materials appearing as electrodes or active elements in devices such as displays, solar cells, and batteries. Particularly important will be the use of MoS 2 for water splitting and metal oxides as hydrogen evolution catalysts. In addition, two-dimensional materials will find important roles in printed electronics as dielectrics, optoelectronic devices, and transistors. To achieve this, much needs to be done. Production rates need to be increased dramatically, the degree of exfoliation improved, and methods to control nanosheet properties developed. The range of layered materials that can be exfoliated must be expanded, even as methods for chemical modification must be developed. Success in these areas will lead to a family of materials that will dominate nanomaterials science in the 21st century.

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Emerging Photoluminescence in Monolayer MoS2

2010-03-15

Andrea Splendiani , L. Sun , Yuanbo Zhang +5 more

Novel physical phenomena can emerge in low-dimensional nanomaterials. Bulk MoS2, a prototypical metal dichalcogenide, is an indirect bandgap semiconductor with negligible photoluminescence. When the MoS2 crystal is thinned to monolayer, … Novel physical phenomena can emerge in low-dimensional nanomaterials. Bulk MoS2, a prototypical metal dichalcogenide, is an indirect bandgap semiconductor with negligible photoluminescence. When the MoS2 crystal is thinned to monolayer, however, a strong photoluminescence emerges, indicating an indirect to direct bandgap transition in this d-electron system. This observation shows that quantum confinement in layered d-electron materials like MoS2 provides new opportunities for engineering the electronic structure of matter at the nanoscale.

Valley polarization in MoS2 monolayers by optical pumping

2012-06-17

Hualing Zeng , Junfeng Dai , Wang Yao +2 more

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One‐Dimensional Nanostructures: Synthesis, Characterization, and Applications

2003-03-04

Yan Xia , Pengfei Yang , Yugang Sun +6 more

Abstract This article provides a comprehensive review of current research activities that concentrate on one‐dimensional (1D) nanostructures—wires, rods, belts, and tubes—whose lateral dimensions fall anywhere in the range of 1 … Abstract This article provides a comprehensive review of current research activities that concentrate on one‐dimensional (1D) nanostructures—wires, rods, belts, and tubes—whose lateral dimensions fall anywhere in the range of 1 to 100 nm. We devote the most attention to 1D nanostructures that have been synthesized in relatively copious quantities using chemical methods. We begin this article with an overview of synthetic strategies that have been exploited to achieve 1D growth. We then elaborate on these approaches in the following four sections: i) anisotropic growth dictated by the crystallographic structure of a solid material; ii) anisotropic growth confined and directed by various templates; iii) anisotropic growth kinetically controlled by supersaturation or through the use of an appropriate capping reagent; and iv) new concepts not yet fully demonstrated, but with long‐term potential in generating 1D nanostructures. Following is a discussion of techniques for generating various types of important heterostructured nanowires. By the end of this article, we highlight a range of unique properties (e.g., thermal, mechanical, electronic, optoelectronic, optical, nonlinear optical, and field emission) associated with different types of 1D nanostructures. We also briefly discuss a number of methods potentially useful for assembling 1D nanostructures into functional devices based on crossbar junctions, and complex architectures such as 2D and 3D periodic lattices. We conclude this review with personal perspectives on the directions towards which future research on this new class of nanostructured materials might be directed.

Van der Waals heterostructures

2013-07-01

A. K. Geim , I. V. Grigorieva

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Strong Light-Matter Interactions in Heterostructures of Atomically Thin Films

2013-05-03

L. Britnell , R. M. Ribeiro , A. Eckmann +7 more

The isolation of various two-dimensional (2D) materials, and the possibility to combine them in vertical stacks, has created a new paradigm in materials science: heterostructures based on 2D crystals. Such … The isolation of various two-dimensional (2D) materials, and the possibility to combine them in vertical stacks, has created a new paradigm in materials science: heterostructures based on 2D crystals. Such a concept has already proven fruitful for a number of electronic applications in the area of ultrathin and flexible devices. Here, we expand the range of such structures to photoactive ones by using semiconducting transition metal dichalcogenides (TMDCs)/graphene stacks. Van Hove singularities in the electronic density of states of TMDC guarantees enhanced light-matter interactions, leading to enhanced photon absorption and electron-hole creation (which are collected in transparent graphene electrodes). This allows development of extremely efficient flexible photovoltaic devices with photoresponsivity above 0.1 ampere per watt (corresponding to an external quantum efficiency of above 30%).

Ultrafast charge transfer in atomically thin MoS2/WS2 heterostructures

2014-08-24

Xiaoping Hong , Jonghwan Kim , Su‐Fei Shi +7 more

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Electronics and optoelectronics of two-dimensional transition metal dichalcogenides

2012-11-01

Qing Hua Wang , Kourosh Kalantar‐zadeh , András Kis +2 more

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Valley-selective circular dichroism of monolayer molybdenum disulphide

2012-06-06

Ting Cao , Gang Wang , Wenpeng Han +7 more

A two-dimensional honeycomb lattice harbors a pair of inequivalent valleys in the k-space electronic structure, in the vicinities of the vertices of a hexagonal Brillouin zone, K}$_{\pm}$. It is particularly … A two-dimensional honeycomb lattice harbors a pair of inequivalent valleys in the k-space electronic structure, in the vicinities of the vertices of a hexagonal Brillouin zone, K}$_{\pm}$. It is particularly appealing to exploit this emergent degree of freedom of charge carriers, in what is termed "valleytronics", if charge carrier imbalance between the valleys can be achieved. The physics of valley polarization will make possible electronic devices such as valley filter and valley valve, and optoelectronic Hall devices, all very promising for next-generation electronic and optoelectronic applications. The key challenge lies with achieving valley imbalance, of which a convincing demonstration in a two-dimensional honeycomb structure remains evasive, while there are only a handful of examples for other materials. We show here, using first principles calculations, that monolayer MoS_2, a novel two-dimensional semiconductor with a 1.8 eV direct band gap, is an ideal material for valleytronics by valley- selective circular dichroism, with ensuing valley polarization and valley Hall effect.

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Recent Advances in Two-Dimensional Materials beyond Graphene

2015-11-06

Ganesh R. Bhimanapati , Zhong Lin , Vincent Meunier +7 more

The isolation of graphene in 2004 from graphite was a defining moment for the "birth" of a field: two-dimensional (2D) materials. In recent years, there has been a rapidly increasing … The isolation of graphene in 2004 from graphite was a defining moment for the "birth" of a field: two-dimensional (2D) materials. In recent years, there has been a rapidly increasing number of papers focusing on non-graphene layered materials, including transition-metal dichalcogenides (TMDs), because of the new properties and applications that emerge upon 2D confinement. Here, we review significant recent advances and important new developments in 2D materials "beyond graphene". We provide insight into the theoretical modeling and understanding of the van der Waals (vdW) forces that hold together the 2D layers in bulk solids, as well as their excitonic properties and growth morphologies. Additionally, we highlight recent breakthroughs in TMD synthesis and characterization and discuss the newest families of 2D materials, including monoelement 2D materials (i.e., silicene, phosphorene, etc.) and transition metal carbide- and carbon nitride-based MXenes. We then discuss the doping and functionalization of 2D materials beyond graphene that enable device applications, followed by advances in electronic, optoelectronic, and magnetic devices and theory. Finally, we provide perspectives on the future of 2D materials beyond graphene.

Control of valley polarization in monolayer MoS2 by optical helicity

2012-06-17

Kin Fai Mak , Keliang He , Jie Shan +1 more

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Charge-density waves and superlattices in the metallic layered transition metal dichalcogenides

1975-03-01

J. A. Wilson , F. J. Di Salvo , Shivam Mahajan

Abstract The d1 layer metals TaS2, TaSe2, NbSe2, in all their various polytypic modifications, acquire, below some appropriate temperature, phase conditions that their electromagnetic properties have previously revealed as ‘anomalous’. … Abstract The d1 layer metals TaS2, TaSe2, NbSe2, in all their various polytypic modifications, acquire, below some appropriate temperature, phase conditions that their electromagnetic properties have previously revealed as ‘anomalous’. Our present electron-microscope studies indicate that this anomalous behaviour usually includes the adoption, at some stage, of a superlattice. The size of superlattice adopted often is forecast in the pattern of satellite spotting and strong diffuse scattering found above the transition. Our conclusions are that charge-density waves and their concomitant periodic structural distortions occur in all these 4d1/5d1 dichalcogenides. We have related the observed periodicities of these CDW states to the theoretical form of the parent Fermi surfaces. Particularly for the 1T octahedrally coordinated polytypes the Fermi surface is very simple and markedly two-dimensional in character, with large near-parallel walls. Such a situation is known theoretically to favour the formation of charge and spin-density waves. When they first appear, the CDW's in the 1T (and 4Hb) polytypes are incommensurate with the lattice. This condition produces a fair amount of gapping in the density of states at the Fermi level. For the simplest case of 1T-TaSe2, the room temperature superlattice is realized when this existing CDW rotates into an orientation for which it then becomes commensurate. At this first-order transition the Fermi surface energy gapping increases beyond that generated by the incommensurate CDW, as is clearly evident in the electromagnetic properties. For the trigonal prismatically coordinated polytypes, CDW formation is withheld to low temperatures, probably because of the more complex band structures. This CDW state (in the cases measured) would seem at once commensurate, even though the transition is, from a wide variety of experiments, apparently second order. A wide range of doped and intercalated materials have been used to substantiate the presence of CDW's in these compounds, and to clarify the effect that their occurrence has on the physical properties. The observations further demonstrate the distinctiveness of the transition metal dichalcogenide layer compounds, and of the group VA metals in particular.

Phosphorene: An Unexplored 2D Semiconductor with a High Hole Mobility

2014-03-17

Han Liu , Adam T. Neal , Zhen Zhu +4 more

Preceding the current interest in layered materials for electronic applications, research in the 1960's found that black phosphorus combines high carrier mobility with a fundamental band gap. We introduce its … Preceding the current interest in layered materials for electronic applications, research in the 1960's found that black phosphorus combines high carrier mobility with a fundamental band gap. We introduce its counterpart, dubbed few-layer phosphorene, as a new 2D p-type material. Same as graphene and MoS2, phosphorene is flexible and can be mechanically exfoliated. We find phosphorene to be stable and, unlike graphene, to have an inherent, direct and appreciable band-gap that depends on the number of layers. Our transport studies indicate a carrier mobility that reflects its structural anisotropy and is superior to MoS2. At room temperature, our phosphorene field-effect transistors with 1.0 um channel length display a high on-current of 194 mA/mm, a high hole field-effect mobility of 286 cm2/Vs, and an on/off ratio up to 1E4. We demonstrate the possibility of phosphorene integration by constructing the first 2D CMOS inverter of phosphorene PMOS and MoS2 NMOS transistors.

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Metal dichalcogenide nanosheets: preparation, properties and applications

2013-01-01

Xiao Huang , Zhiyuan Zeng , Hua Zhang

Two-dimensional (2D) nanomaterials have received much attention in recent years, because of their unusual properties associated with their ultra-thin thickness and 2D morphology. Besides graphene which has aroused tremendous research … Two-dimensional (2D) nanomaterials have received much attention in recent years, because of their unusual properties associated with their ultra-thin thickness and 2D morphology. Besides graphene which has aroused tremendous research interest, other types of 2D nanomaterials such as metal dichalcogenides have also been studied and applied in various applications including electronics, optoelectronics, energy storage devices, and so on. In this tutorial review, we will take MoS2 as a typical example to introduce the latest research development of 2D inorganic nanomaterials with emphasis on their preparation methods, properties and applications.

Catalysis with two-dimensional materials and their heterostructures

2016-03-01

Dehui Deng , Kostya S. Novoselov , Qiang Fu +3 more

Intrinsic Structural Defects in Monolayer Molybdenum Disulfide

2013-05-09

Wu Zhou , Xiaolong Zou , Sina Najmaei +7 more

Monolayer molybdenum disulfide (MoS2) is a two-dimensional direct band gap semiconductor with unique mechanical, electronic, optical, and chemical properties that can be utilized for novel nanoelectronics and optoelectronics devices. The … Monolayer molybdenum disulfide (MoS2) is a two-dimensional direct band gap semiconductor with unique mechanical, electronic, optical, and chemical properties that can be utilized for novel nanoelectronics and optoelectronics devices. The performance of these devices strongly depends on the quality and defect morphology of the MoS2 layers. Here we provide a systematic study of intrinsic structural defects in chemical vapor phase grown monolayer MoS2, including point defects, dislocations, grain boundaries, and edges, via direct atomic resolution imaging, and explore their energy landscape and electronic properties using first-principles calculations. A rich variety of point defects and dislocation cores, distinct from those present in graphene, were observed in MoS2. We discover that one-dimensional metallic wires can be created via two different types of 60° grain boundaries consisting of distinct 4-fold ring chains. A new type of edge reconstruction, representing a transition state during growth, was also identified, providing insights into the material growth mechanism. The atomic scale study of structural defects presented here brings new opportunities to tailor the properties of MoS2 via controlled synthesis and defect engineering.

Photonics and optoelectronics of 2D semiconductor transition metal dichalcogenides

2016-03-31

Kin Fai Mak , Jie Shan

Van der Waals heterostructures and devices

2016-07-12

Yuan Liu , Nathan O. Weiss , Xidong Duan +3 more

2D materials and van der Waals heterostructures

2016-07-28

Kostya S. Novoselov , Artem Mishchenko , Alexandra Carvalho +1 more

The physics of two-dimensional (2D) materials and heterostructures based on such crystals has been developing extremely fast. With new 2D materials, truly 2D physics has started to appear (e.g. absence … The physics of two-dimensional (2D) materials and heterostructures based on such crystals has been developing extremely fast. With new 2D materials, truly 2D physics has started to appear (e.g. absence of long-range order, 2D excitons, commensurate-incommensurate transition, etc). Novel heterostructure devices are also starting to appear - tunneling transistors, resonant tunneling diodes, light emitting diodes, etc. Composed from individual 2D crystals, such devices utilize the properties of those crystals to create functionalities that are not accessible to us in other heterostructures. We review the properties of novel 2D crystals and how their properties are used in new heterostructure devices.

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Valleytronics in 2D materials

2016-08-23

John R. Schaibley , Hongyi Yu , Genevieve Clark +5 more

Recent development of two-dimensional transition metal dichalcogenides and their applications

2017-01-09

Wonbong Choi , Nitin Choudhary , Gang Han +3 more

Recent advances in atomically thin two-dimensional transition metal dichalcogenides (2D TMDs) have led to a variety of promising technologies for nanoelectronics, photonics, sensing, energy storage, and opto-electronics, to name a … Recent advances in atomically thin two-dimensional transition metal dichalcogenides (2D TMDs) have led to a variety of promising technologies for nanoelectronics, photonics, sensing, energy storage, and opto-electronics, to name a few. This article reviews the recent progress in 2D materials beyond graphene and includes mainly transition metal dichalcogenides (TMDs) (e.g. MoS2, WS2, MoSe2, and WSe2). These materials are finding niche applications for next-generation electronics and optoelectronics devices relying on ultimate atomic thicknesses. Albeit several challenges in developing scalable and defect-free TMDs on desired substrates, new growth techniques compatible with traditional and unconventional substrates have been developed to meet the ever-increasing demand of high quality and controllability for practical applications. The fabrication of novel 2D TMDs that exhibit exotic functionalities and fundamentally new chemistry is highlighted. And finally, in parallel with the electronics, the considerable effort devoted to using these materials for energy and sensing applications is discussed in detail.

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Layer-dependent ferromagnetism in a van der Waals crystal down to the monolayer limit

2017-06-06

Bevin Huang , Genevieve Clark , Efrén Navarro‐Moratalla +7 more

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Discovery of intrinsic ferromagnetism in two-dimensional van der Waals crystals

2017-04-25

Cheng Gong , Lin Li , Zhenglu Li +7 more

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Janus monolayers of transition metal dichalcogenides

2017-05-15

Ang‐Yu Lu , Hanyu Zhu , Jun Xiao +7 more

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2D transition metal dichalcogenides

2017-06-13

Sajedeh Manzeli , Dmitry Ovchinnikov , Diego Pasquier +2 more

Gate-tunable room-temperature ferromagnetism in two-dimensional Fe3GeTe2

2018-10-19

Yujun Deng , Yijun Yu , Yichen Song +7 more

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Anomalous Lattice Vibrations of Single- and Few-Layer MoS2

2010-04-14

Changgu Lee , Hugen Yan , Louis E. Brus +3 more

Molybdenum disulfide (MoS2) of single- and few-layer thickness was exfoliated on SiO2/Si substrate and characterized by Raman spectroscopy. The number of S−Mo−S layers of the samples was independently determined by … Molybdenum disulfide (MoS2) of single- and few-layer thickness was exfoliated on SiO2/Si substrate and characterized by Raman spectroscopy. The number of S−Mo−S layers of the samples was independently determined by contact-mode atomic force microscopy. Two Raman modes, E12g and A1g, exhibited sensitive thickness dependence, with the frequency of the former decreasing and that of the latter increasing with thickness. The results provide a convenient and reliable means for determining layer thickness with atomic-level precision. The opposite direction of the frequency shifts, which cannot be explained solely by van der Waals interlayer coupling, is attributed to Coulombic interactions and possible stacking-induced changes of the intralayer bonding. This work exemplifies the evolution of structural parameters in layered materials in changing from the three-dimensional to the two-dimensional regime.

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Single-Layer MoS2Phototransistors

2011-12-13

Zongyou Yin , Hai Li , Hong Li +7 more

A new phototransistor based on the mechanically exfoliated single-layer MoS2 nanosheet is fabricated, and its light-induced electric properties are investigated in detail. Photocurrent generated from the phototransistor is solely determined … A new phototransistor based on the mechanically exfoliated single-layer MoS2 nanosheet is fabricated, and its light-induced electric properties are investigated in detail. Photocurrent generated from the phototransistor is solely determined by the illuminated optical power at a constant drain or gate voltage. The switching behavior of photocurrent generation and annihilation can be completely finished within ca. 50 ms, and it shows good stability. Especially, the single-layer MoS2 phototransistor exhibits a better photoresponsivity as compared with the graphene-based device. The unique characteristics of incident-light control, prompt photoswitching, and good photoresponsivity from the MoS2 phototransistor pave an avenue to develop the single-layer semiconducting materials for multifunctional optoelectronic device applications in the future.

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Energy band alignment in MoS2/HfO2: Transfer-related artifacts and interfacial effects

2025-06-25

I. Shlyakhov , Konstantin Iakoubovskii , Dennis Lin +4 more | Journal of Applied Physics

The knowledge of energy band alignment in heterojunctions with atomically thin transition metal dichalcogenides (TMDs) is critical for their use in advanced electronic and optoelectronic devices. Despite considerable efforts, the … The knowledge of energy band alignment in heterojunctions with atomically thin transition metal dichalcogenides (TMDs) is critical for their use in advanced electronic and optoelectronic devices. Despite considerable efforts, the measurement of energy band offset across heterojunctions has been challenging, especially for van der Waals bonded stacks. Key obstacles are related to the scarce and often inconsistent information regarding the bandgap of the TMD layer and the offset between the conduction and valence bands, which is usually inferred from different measurement techniques and samples. To overcome this obstacle, we report combined internal photoemission (IPE) and photoconductivity measurements from 3-monolayer (ML) MoS2 films, grown by chemical vapor deposition on sapphire and transferred onto HfO2-covered silicon. We compare the spectral threshold of electron IPE in this heterostructure with IPE data from the Si/HfO2 interface, yielding the value of the electrostatic potential variation. To improve band offset predictions, we examine the applicability of the classical electron affinity rule by deriving characteristic energies. Our results show that electronic properties at 2D TMD/insulator interfaces depend on the interface processing prior to the 2D material transfer, allowing for the modification of band offsets by adjusting the interface. Furthermore, the measured photoconductivity spectra of 3ML MoS2 allow us to evaluate the bandgap of the TMD layer, which, combined with the IPE barriers, establishes the interface band diagram of a heterojunction. The presented IPE-based experimental approach can be extended to other two-dimensional TMDs for determining the corresponding band alignment schemes. It evaluates the impact of processing, such as solvent-based MoS2 transfer, which introduces a dipole and alters band alignment.

First-principles study of the photoelectric properties of alkaline earth metal (Be/Mg/Ca/Sr/Ba)-doped monolayers of WSe2

2025-06-25

Jiali Liu , Zhen-Hua Wang , Guangyu Zhang +7 more | Colloid & Polymer Science

Tailoring Light–Matter Interactions in 2D Semiconductors

2025-06-24

Ona Ambrozaite , Reynolds Dziobek-Garrett , Thomas J. Kempa | Accounts of Chemical Research

ConspectusTwo-dimensional (2D) crystals have had a sweeping influence on the condensed matter physics and materials science communities for over two decades. Their thinness and ability to be configured into layered … ConspectusTwo-dimensional (2D) crystals have had a sweeping influence on the condensed matter physics and materials science communities for over two decades. Their thinness and ability to be configured into layered and twisted heterostructures has enabled 2D crystals to become a platform material of choice to uncover many intriguing phenomena, including superconductivity, the fractional quantum anomalous Hall effect, spin textures, strain domain walls, and distinct spin-valley transitions. This versatility is on display in 2D semiconductor monolayers, which exhibit strong light-matter coupling to a rich host of excitonic states and valley selective transitions. The optical physics of 2D semiconductors is tunable through manipulation of their structure, chemical composition, mutual orientation in superlattices, and strain. Together, such adjustments give rise to a plethora of exciting applications in optics, spintronics, and quantum sensing. Our contributions to the 2D materials community have focused on developing chemical strategies for precision nanostructure synthesis, elucidating emergent optical phenomena through detailed spectroscopic analysis, and creating new 2D heterostructures that support the localization and manipulation of quasiparticle states. This Account examines selected aspects of our recent work on tailoring light-matter interactions in 2D semiconductors. We discuss how synthetic manipulation of a 2D crystal's dimensions, edge structure, strain state, and coupling to other molecular species and lattices renders specific properties. Through this article we wish to draw attention to the rich chemistry of 2D crystals and the active role chemistry should play in opening new avenues of research in 2D materials.

Ultrafast All‐Optical Terahertz Switchable Modulation Using Van Der Waals Fe4GeTe2/Bi2Te3 Heterostructures

2025-06-24

Zuanming Jin , Hong He , Yun Sun +7 more | Advanced Optical Materials

Abstract 2D all‐van der Waals Fe n GeTe 2 /topological insulator heterostructures present compelling prospects for the development of advanced opto‐spintronic devices, attributed to the coupling between ferromagnetic and topological … Abstract 2D all‐van der Waals Fe n GeTe 2 /topological insulator heterostructures present compelling prospects for the development of advanced opto‐spintronic devices, attributed to the coupling between ferromagnetic and topological characteristics. The ultrafast laser‐induced terahertz (THz) switchable modulations in Fe 4 GeTe 2 /Bi 2 Te 3 heterostructures are investigated by employing optical pump‐THz probe (OPTP) spectroscopy. By comparing the OPTP results of Fe 4 GeTe 2 /Bi 2 Te 3 with those obtained from single Fe 4 GeTe 2 and Bi 2 Te 3 films, it is found that the optically‐induced THz modulation is attributed to both interface carrier accumulation and thermal effect in Fe 4 GeTe 2 . Furthermore, the thickness‐ and temperature‐dependent measurements enable the establish comprehensive rules governing the switching of photoconductivity from positive to negative. The findings highlight a promising pathway for optically controlled THz modulators, achieved by modulating charge dynamics at temperatures near the topological‐to‐trivial transition in all‐van der Waals ferromagnetic Fe 4 GeTe 2 /topological insulator heterostructures.

Multiferroic Van der Waals Heterostructure <scp>CuInP2S6</scp>/<scp>CuCrP2S6</scp>: Electrically Switchable Electronic Properties and Band Alignment

2025-06-24

Yi Sun , Nini Guo , Yujie Liu +2 more | International Journal of Quantum Chemistry

ABSTRACT Building van der Waals heterostructure is an effective method to design multiferroic materials. Here, by performing first principles calculations, we study the electronic and magnetic properties of CuCrP 2 … ABSTRACT Building van der Waals heterostructure is an effective method to design multiferroic materials. Here, by performing first principles calculations, we study the electronic and magnetic properties of CuCrP 2 S 6 /CuInP 2 S 6 (CCPS/CIPS) heterostructure composed of ferroelectric (FE) CuInP 2 S 6 and multiferroic CuCrP 2 S 6 . It is shown that CCPS‐P↓/CIPS‐P↓ is a ferromagnetic (FM) half metal, with the band alignment of type II in the spin‐down channel, while for CCPS‐P↑/CIPS‐P↑, CCPS‐P↑/CIPS‐P↓, and CCPS‐P↓/CIPS‐P↑, they are all FM semiconductors with type II band alignment. Moreover, the electronic properties of CCPS/CIPS can be changed under biaxial strains; that is, CCPS‐P↓/CIPS‐P↓ can change from FM half metal to FM semiconductor, and CCPS‐P↑/CIPS‐P↑, CCPS‐P↑/CIPS‐P↓, and CCPS‐P↓/CIPS‐P↑ have shrinking band gaps in both spin channels under biaxial strains. Such characteristics suggest CCPS/CIPS heterostructure can be potential nonvolatile memory device materials.

Manipulating Hydrogen Evolution Reaction in Janus MoSSe Monolayer via Defect and Strain Engineering

2025-06-24

Weikun Huang , Youtong Su , Kai Ren +2 more | physica status solidi (b)

Janus transition metal dichalcogenides (TMDs) exhibit exceptional electronic, optical, and catalytic properties due to their unique asymmetric structures. The article systematically investigates the stability of Janus MoSSe with typical vacancy … Janus transition metal dichalcogenides (TMDs) exhibit exceptional electronic, optical, and catalytic properties due to their unique asymmetric structures. The article systematically investigates the stability of Janus MoSSe with typical vacancy defects using first‐principles calculations. The results reveal that the Gibbs free energy for the hydrogen evolution reaction (HER) is significantly reduced to ≈0.5 eV, lower than that of pristine MoSSe and conventional MoS 2 monolayers. Notably, the application of external strain further enhances the HER performance of defect‐engineered Janus MoSSe. This improvement is attributed to the adaptive release of concentrated strain by dangling bonds at the defect region, resulting in distinct tunable patterns. The findings elucidate the underlying mechanism behind the enhanced HER performance of MoSSe through strain engineering, providing theoretical support for the optimal design of efficient HER catalysts based on defective Janus TMDs.

Quasi-bound layer breathing phonons inside perfect dislocations of lattice-relaxed twisted transition metal dichalcogenide bilayers

2025-06-24

NULL AUTHOR_ID | Physical review. B./Physical review. B

A Programmable Nonvolatile Schottky Diode Based on van der Waals Ferroelectric Junction

2025-06-24

Baoyu Wang , Wenyu Chen , Liang Zou +7 more | Nano Letters

Programmable and nonvolatile Schottky junctions are highly desirable for next-generation electronic and neuromorphic systems. However, conventional metal-semiconductor and even van der Waals (vdW) Schottky diodes often suffer from fixed rectifying … Programmable and nonvolatile Schottky junctions are highly desirable for next-generation electronic and neuromorphic systems. However, conventional metal-semiconductor and even van der Waals (vdW) Schottky diodes often suffer from fixed rectifying behaviors or limited tunability. Here, we report a programmable nonvolatile ferroelectric Schottky diode based on a vdW heterojunction between semimetallic 1T'-MoTe2 and ferroelectric α-In2Se3. The diode exhibits near-ideal performance, including a rectification ratio exceeding 104, a leakage current down to 1 pA, and an ideality factor as low as 1.38. By switching ferroelectric polarization, the Schottky barrier can be modulated in a programmable manner, enabling reversible, nonvolatile, and multilevel rectification states. The device demonstrates polarization-dependent photoresponse and transient integrate-and-leak dynamics, closely resembling biological spiking neurons. A spiking neural network is implemented based on this behavior, achieving image recognition accuracy up to 98.4%. This work establishes programmable ferroelectric Schottky diodes as promising candidates for low-power memory, reconfigurable logic, and neuromorphic vision.

Thickness-Dependent Second Harmonic Generation and Anisotropic Exciton Davydov Splitting in AA-Stacked ReS2

2025-06-24

Guohao Liao , Youxuan Wu , Xinkun Zheng +7 more | The Journal of Physical Chemistry C

Hybrid‐Dimensional Polycrystalline van der Waals Heterostructure for High Responsivity and Broadband Detection

2025-06-24

Zexu Wang , Yuchao Wei , Chao Chen +7 more | Laser & Photonics Review

Abstract 2D‐based photothermoelectric (PTE) photodetectors have emerged as promising candidates for high‐performance broadband detection, owing to their outstanding optoelectronic and thermal characteristics. However, the intrinsically poor light absorption and high … Abstract 2D‐based photothermoelectric (PTE) photodetectors have emerged as promising candidates for high‐performance broadband detection, owing to their outstanding optoelectronic and thermal characteristics. However, the intrinsically poor light absorption and high thermal conductivity of 2D materials result in limited responsivity and sensitivity. The 2D/3D hybrid‐dimensional heterostructure, featuring a lattice‐mismatch‐free interface, successfully integrates the superior electrical properties of 2D materials with the high light absorption and excellent sensitivity of 3D materials, providing a novel platform for developing high‐performance optoelectronic devices. In this work, a 2D SnSe 2 /3D PbSe hybrid‐dimensional van der Waals (vdWs) heterojunction is proposed, leveraging its distinct band alignment and efficient thermal management to effectively suppress the potential barrier while achieving enhanced PTE response, ultimately enabling a high‐speed, broadband (500–4100 nm) photodetector. Specifically, the device demonstrates a high responsivity of 2343 V/W, an ultrafast response speed ≈60 µs, and an exceptional detectivity of ≈10 10 Jones under 780 nm illumination. Notably, it maintains a responsivity exceeding 60 V/W and a rapid response time of 54 µs even at 3500 nm. In summary, this study exploits a hybrid‐dimensional polycrystalline vdWs heterostructure to introduce a novel strategy for designing high‐performance, broadband photodetectors.

Spin–phonon coupling and phonon dynamics in van der Waals antiferromagnetic CrSBr

2025-06-23

Xin Wei , Mengdi Li , Xuemin He +4 more | Applied Physics Letters

As a vander Waals antiferromagnetic semiconductor, CrSBr exhibits unique anisotropy and hosts various physical phenomena (e.g., magnons, phonons, excitons, and polarons), showing great application potential. However, extensive investigations of its … As a vander Waals antiferromagnetic semiconductor, CrSBr exhibits unique anisotropy and hosts various physical phenomena (e.g., magnons, phonons, excitons, and polarons), showing great application potential. However, extensive investigations of its spin–phonon coupling and phonon dynamics are still limited. In this study, we employed a combination of group theory analysis and first-principles calculations and carried out comprehensive angle-resolved polarization-dependent and temperature-dependent Raman spectroscopy measurements on CrSBr single crystals. The abnormal shifts in phonon frequency and linewidth were observed below the Néel temperature, and the underlying spin–phonon coupling within CrSBr was unveiled. Additionally, phonon softening with increasing temperature was indicated by Raman spectroscopy, mainly due to phonon anharmonicity. Phonon scattering rates also increased with temperature due to enhanced phonon–phonon interactions, supporting the prediction of low thermal conductivity in CrSBr. The anisotropic structure of CrSBr, combined with spin–phonon coupling effects and phonon anharmonicity, holds significant potential for spintronics and thermoelectric applications.

All‐Heat Control of Magnetization Dynamics on Van der Waals Magnets

2025-06-23

Sumit Haldar , Theodor Griepe , Unai Atxitia +1 more | Advanced Materials

Abstract Heat dissipation in nanomagnetic devices mediated by femtosecond laser excitation constitutes one of the pressing challenges toward energy‐efficient applications yet to be solved. Of particular interest are heterostructures based … Abstract Heat dissipation in nanomagnetic devices mediated by femtosecond laser excitation constitutes one of the pressing challenges toward energy‐efficient applications yet to be solved. Of particular interest are heterostructures based on 2D van der Waals (vdW) magnets, which benefit from superior interfacial controllability, mechanical flexibility for smart storage platforms, and open‐source for large‐scale production. However, how heat affects the ultrafast magnetization dynamics in such systems, and/or how the spin dynamics can provide alternative pathways for effective heat dissipation have so far been elusive. Here it is shown that the missing link between magnetization dynamics and heat transport is mediated by the thermal conductivity mismatch between the underneath substrate and the vdW magnet. By modeling the laser‐induced ultrafast spin dynamics of three popular vdW materials (CrI 3 , CrGeTe 3 , Fe 3 GeTe 2 ) of different electronic characteristics across sixteen substrates of distinct chemical composition, it is found that both the demagnetization and remagnetization timescales are very sensitive to the phonon temperature dynamics through the supporting materials, which defines the heating dissipation efficiency at the interface. The process can be further tuned with the thickness of the vdW magnets, where thin (thick) systems result in faster (slower) magnetization dynamics. It is unveiled that the non‐thermal nature of spin dynamics in vdW heterostructures creates interfacial spin accumulation that generates spin‐polarized currents with dominant frequencies ranging from 0.18 to 1.0 GHz accordingly to the layer thickness and substrate. The findings demonstrate that substrate engineering liaised with the choice of magnetic compounds open venues for efficient spin‐heat control, which ultimately determines the optically excited magnetic characteristics of the vdW layers.

Computational Screening of 2D Transition Metal Halides for Optical Applications: The Role of Excitonic Effects

2025-06-23

Natan M. Regis , Juarez L. F. Da Silva , Matheus P. Lima | ACS Applied Energy Materials

A Simple and Rapid Fluorescent Sensor Based on MoS2 Quantum Dots for Dopamine Detection

2025-06-23

Yunbo Zhao , Fangyuan Yang , Lefa Zhao +1 more | Journal of Fluorescence

Site-Selective Generation of Sub-Band Gap Infrared Light Emission by Local Strain in van der Waals γ-InSe

2025-06-23

Qishuo Tan , Jing Tang , Arka Chatterjee +4 more | ACS Nano

van der Waals layered materials have garnered enormous attention for their unique electronic and optical properties. Among them, γ-indium selenide (γ-InSe) exhibits a thickness-dependent crossover from a direct to an … van der Waals layered materials have garnered enormous attention for their unique electronic and optical properties. Among them, γ-indium selenide (γ-InSe) exhibits a thickness-dependent crossover from a direct to an indirect band gap. Here, we report strain-induced sub-band gap infrared photoluminescence (PL) in γ-InSe by applying local strain via SiO2 nanopillars. The broad sub-band gap emission is confined to the strained sites and vanishes above 200 K. Density functional theory calculations, combined with laser power-dependent PL and time-resolved PL measurements, suggest the defect origin of the emission caused by selenium vacancies. These findings elucidate strain-defect interactions in layered γ-InSe and indicate a pathway to defect-based optoelectronics and quantum-emitter devices.

First-principles study of the electronic structure and photogalvanic effect in a novel 2D β-AsP/ ZrBrCl heterostructures

2025-06-23

Zhonghui Xu , Jie Kang , Bing Luo +2 more | Journal of Physics D Applied Physics

Abstract We present a comprehensive study of vertically stacked β-AsP/ZrBrCl heterostructures using first-principles calculations. Our results demonstrate that the electronic properties of these heterostructures are highly dependent on stacking configuration, … Abstract We present a comprehensive study of vertically stacked β-AsP/ZrBrCl heterostructures using first-principles calculations. Our results demonstrate that the electronic properties of these heterostructures are highly dependent on stacking configuration, with the AA, AB and AC configurations exhibiting type-II indirect semiconductor behavior. The heterostructure display excellent broadband optical absorption across the visible and near-ultraviolet regions, effectively combining the light absorption characteristics of both monolayers.Taking advantage of these unique properties, we have developed a dual-probe photodetector model with significant polarization-sensitive responses. Notably, the AB-armchair configuration achieves an impressive extinction ratioof 1060 at a photon energy of 2.8 eV, outperforming most existing two-dimensional (2D) material-based photodetector. This work positions β-AsP/ZrBrCl heterostructures as promising candidates for high-performance polarization-resolved photodetection applications.&#xD;

Energetics and Electronic Structures of Janus WSSe Nanoscrolls

2025-06-23

Yanlin Gao , Susumu Okada | ACS Applied Electronic Materials

Air‐Stable Lithiation of MoS2 for Direct‐Bandgap Multilayers

2025-06-23

Qi Fu , Yichi Zhang , Jichuang Shen +7 more | Small Science

Due to its sizable direct bandgap and strong light‐matter interactions, the preparation of monolayer MoS 2 has attracted significant attention and intensive research efforts. However, multilayer MoS 2 is largely … Due to its sizable direct bandgap and strong light‐matter interactions, the preparation of monolayer MoS 2 has attracted significant attention and intensive research efforts. However, multilayer MoS 2 is largely overlooked because of its optically inactive indirect bandgap caused by interlayer coupling. It is highly desirable to modulate and decrease the interlayer coupling so that each layer in multilayer MoS 2 can exhibit a monolayer‐like direct‐gap behavior. Herein, the nanoprobe‐controlled fabrication of Li x MoS 2 ‐based multilayers is demonstrated, exhibiting a direct bandgap and strong photoluminescence emission from tightly bound excitons and trions. The fabrication of Li x MoS 2 multilayers is facilitated by the newly developed Li‐ion platform, featuring tip‐induced Li intercalation, doping patterning with a spatial resolution of 517 nm, air stability, and rewritability. Ultralow frequency Raman characterizations reveal that controlled Li intercalation effectively transforms multilayer MoS 2 into the stack of multiple monolayers, leading to a 26‐fold enhancement of photoluminescence compared to a monolayer. The intercalation result is different from existing observations of transforming MoS 2 multilayers into metallic phases. This work not only provides a highly controllable Li‐ionic engineering platform for studying Li‐material interactions and developing novel ionic electronics but also offers an intriguing direct‐bandgap semiconductor for optoelectronic applications.

Characterizing nanoscale spatiotemporal defects of multi-layered MoSe2 in hyper-temporal transient nanoscopy

2025-06-23

Hwi Je Woo , Sung-Gyu Lee , Hansung Kim +3 more | Nanophotonics

Abstract We directly characterize nanoscale spatiotemporal inhomogeneities of multi-layered molybdenum diselenide (MoSe 2 ) in real space and time – the nanometre–femtosecond scale, attributing to local mechanical structures such as … Abstract We directly characterize nanoscale spatiotemporal inhomogeneities of multi-layered molybdenum diselenide (MoSe 2 ) in real space and time – the nanometre–femtosecond scale, attributing to local mechanical structures such as strain and surface/subsurface defects, which are critical in semiconductor and optoelectronic applications. This remarkable precision is achieved through the development of a hyper-temporal transient nanoscopy incorporating a sideband-coupled generalized lock-in amplification technique, allowing for characterization of local spatiotemporal defects at each pixel within a subwavelength mapping region. By utilizing this technique, we characterize the nanoscale strain-induced spatiotemporal defects of multi-layered MoSe 2 , including nano-bubbles that exhibit a noticeable reduction in exciton-exciton annihilation rates, which may attribute to the suppressed probability of bimolecular interaction of excitons due to the strain-induced band distortion. Moreover, we visualize topographically hidden spatiotemporal defects such as lattice mismatches, which induce mid-gap states that traps charge carriers and thereby slow down recombination process. We propose that this hyper-temporal approach to resolving intricate spatiotemporal inhomogeneities in van der Waals materials provides significant insights into their optoelectronic properties and opens new avenues for innovative material design and characterization.

A New Memory Effect in Bulk Crystals of 1T‐TaS2

2025-06-23

Avital Fried , Ouriel Gotesdyner , Irena Feldman +2 more | Advanced Functional Materials

Abstract Strongly correlated systems famously show intriguing (and unexpected) phenomena. The layered 1T‐TaS₂ is no exception, showing different charge density wave configurations, metal insulator transitions (MITs), a fascinating superconducting phase, … Abstract Strongly correlated systems famously show intriguing (and unexpected) phenomena. The layered 1T‐TaS₂ is no exception, showing different charge density wave configurations, metal insulator transitions (MITs), a fascinating superconducting phase, and low‐temperature meta‐stable hidden phases upon light or current pulses. And now – also a non‐volatile memory effect. The memory forms following cooling of the sample to a chosen temperature in the metal‐insulator coexisting phase of the Mott MIT (≈180 K) then ramping back up to the metallic state. It manifests as a resistance decrease in the following R versus T measurement that is largest at the ramp‐reversal temperature. The memory disappears after cooling to lower temperatures and the original R versus T is recovered. Memory properties are shown to coincide with those of the ramp reversal memory (RRM) previously reported in correlated oxides, including non‐volatility and the ability to write more than one memory. However, there are notable differences and a different origin. These findings indicate that RRM extends beyond oxides, highlighting its universality in correlated materials having the necessary ingredients: phase transition with spatial phase coexistence and a mechanism that locally modifies the transition properties. These findings open new opportunities for exploring memory phenomena in correlated materials.

Thinning Effect of Few-Layer Black Phosphorus Exposed to Dry Oxidation

2025-06-23

Qianyi Li , Hang Yang , Xiaofang Zheng +6 more | Nanomaterials

Few-layer black phosphorus (BP) holds significant potential for next-generation electronics due to its tunable bandgap and high carrier mobility. The layer modulation of BP is essential in the applications of … Few-layer black phosphorus (BP) holds significant potential for next-generation electronics due to its tunable bandgap and high carrier mobility. The layer modulation of BP is essential in the applications of electronic devices ascribed to its thickness-dependent electronic properties. However, precisely controlling its thickness still presents a challenge for optimizing performance. In this study, we demonstrate that BP can be precisely thinned when exposed to dry oxygen (40% humidity, low oxygen concentration) in a dark environment, which is different from that exposed to humid oxygen (100% humidity, low oxygen concentration) without light illumination. The thinned BP not only demonstrates enhanced stability but also exhibits significant improvements in its electrical properties. The variation in bandgap from 0.3 to 2 eV, resulting in the ION/IOFF ratio increased from 103 to 106, and the hole mobility improved from 235 cm2 V−1 s−1 to 851 cm2 V−1 s−1, was ascribed to the layer-by-layer thinning and p-type doping effects induced by the formed PxOy. Our finding demonstrates significant potential of BP in future nanoelectronic and optoelectronic applications.

WS2 p-MOSFETs with channels deposited by plasma-enhanced atomic-layer deposition

2025-06-23

Ruixue Li , Rebecca A. Dawley , Shivanshu Mishra +3 more | Applied Physics Letters

We report the demonstration of p-channel WS2 metal oxide field effect transistors (MOSFETs) using channels deposited by plasma-enhanced atomic layer deposition (PE-ALD). Substrate-gated devices using PE-ALD WS2 films deposited at … We report the demonstration of p-channel WS2 metal oxide field effect transistors (MOSFETs) using channels deposited by plasma-enhanced atomic layer deposition (PE-ALD). Substrate-gated devices using PE-ALD WS2 films deposited at 300 °C were fabricated with source-to-drain spacing, LDS, ranging from 0.1 to 1.1 µm. Despite being undoped, both 3.4-nm and 2.1-nm-thick films displayed p-type conduction. Substrate-gated devices with LDS = 0.1 µm had on-state current, Ion, of 0.86 µA/µm (0.40 µA/µm) at a drain voltage of VD = −1 V for a channel thickness of 3.4 nm (2.1 nm). It was found that the thinner films displayed improved on/off current ratio, Ion/Ioff, and MOSFETs with 2.1-nm-thick channels had Ion/Ioff = 16.7 compared to only 6.8 for 3.4-nm-thick channels. Devices with 1.4-nm-thick WS2 channels were also fabricated by incorporating a 1.6-nm capping layer of NbxW1−xSy, where NbxW1−xSy provided a heavily doped layer underneath the metal contact and was oxidized in the region between source and drain contacts using low-temperature O2 annealing. These devices had Ion/Ioff as high as 28 at room temperature, a substantial improvement to the WS2-only devices. Measurement at 77 K showed Ion/Ioff values as high as 260, and extraction of the contact barrier height using temperature-dependent measurements showed that a small energy barrier still exists between the NbxW1−xSy and the WS2.

Adjusting Schottky barrier height and enhancing diode performances in 1T-MoT2/WSeTe (MoSeTe) heterojunctions by interlayer flipping

2025-06-23

Qian Liu , Xudong Huang , J. Chen +5 more | Applied Physics Letters

Two-dimensional (2D) Janus materials have received significant attention due to their unique physical structure and superior electronic and optical properties. Here, we investigate the diode performance of 2D Janus WSeTe … Two-dimensional (2D) Janus materials have received significant attention due to their unique physical structure and superior electronic and optical properties. Here, we investigate the diode performance of 2D Janus WSeTe or MoSeTe vertical contact with 2D 1T-MoTe2 using ab initio quantum transport simulations. When the Te atomic layer of WSeTe or MoSeTe contacts with 1T-MoTe2 (known as type-A heterojunction), the contact interface exhibits significant Fermi level pinning (FLP), resulting in a larger Schottky barrier height (SBH). Through interlayer flipping, the Se atomic layer of WSeTe or MoSeTe comes into contact with 1T-MoTe2 (known as type-B heterojunction), FLP at the contact interface will be significantly suppressed, resulting in obvious reduction of the SBH. Therefore, Schottky diodes based on type-B heterojunction exhibit superior performances with higher rectification ratio and larger photocurrent compared to Schottky diodes based on type-A heterojunction.

Investigating the High Electron Mobilities and Transport Scattering Processes in 2D Non‐Van Der Waals Bi2O2Te Nanosheet Films

2025-06-22

Sasithorn Chomngam , Samuk Pimanpang , Chesta Ruttanapun +2 more | Advanced Theory and Simulations

Abstract Bismuth oxytelluride (Bi 2 O 2 Te) nanosheets, a 2D non‐van der Waals (2D‐nvdW) semiconductor, has exceptionally high carrier mobilities, between 496 and 584 cm 2 V −1 s … Abstract Bismuth oxytelluride (Bi 2 O 2 Te) nanosheets, a 2D non‐van der Waals (2D‐nvdW) semiconductor, has exceptionally high carrier mobilities, between 496 and 584 cm 2 V −1 s −1 at room temperature (RT). Its numerous potential applications in multifunctional electronic devices have sparked much research interest. However, comprehensive explanations of the high RT mobilities and transport scattering processes in the Bi 2 O 2 Te nanosheet films are still sought. Herein, measured mobility data, between 5000 and 54,074 cm 2 V −1 s −1 at 2 K and 125–584 cm 2 V −1 s −1 at 300 K, are examined and modeled considering several scattering sources, including ionized impurities, longitudinal optical (LO) phonon, and electron–electron interactions. The total mobility based on three scattering mechanisms provided good quantitative agreement with the experimental results from thicknesses ranging from 21.0 to 55.0 nm. Ionized impurity scattering limits mobility at temperatures lower than 50 K, but LO phonon and electron–electron scatterings dominate at temperatures between 50 and 300 K. When the thickness decreases to 21.0 nm, electron‐electron scattering strength becomes stronger and the RT mobility drops to 125 cm 2 V −1 s −1 . These findings advance the knowledge of the charge transport mechanisms that underlie the Bi 2 O 2 Te nanosheet and provide more details for other 2D‐nvdW and 2D semiconductors.

Gate-Tunable Band Edge in Few-Layer MoS2

2025-06-22

Michele Masseroni , Isaac Soltero , James G. McHugh +7 more | Nano Letters

Transition metal dichalcogenides (TMDs) have garnered significant research interest due to the variation in band edge locations within the hexagonal Brillouin zone between single-layer and bulk configurations. In monolayers, the … Transition metal dichalcogenides (TMDs) have garnered significant research interest due to the variation in band edge locations within the hexagonal Brillouin zone between single-layer and bulk configurations. In monolayers, the conduction band minima are centered at the K points, whereas in multilayers, they shift to the Q points, midway between the Γ and K points. In this study, we conduct magnetotransport experiments to measure the occupation in the Q and K valleys in four-layer molybdenum disulfide (MoS2). We demonstrate electrostatic tunability of the conduction band edge by combining our experimental results with a hybrid k·p tight-binding model that accounts for interlayer screening effects in a self-consistent manner. Furthermore, we extend our model to bilayer and trilayer MoS2, reconciling prior experimental results and quantifying the tunable range of band edges in atomically thin TMDs.

Black Phosphorus Nanoribbons: From Synthesis to Applications

2025-06-22

Wei Zhang , Jin Wang , Xiaofen Zhong +1 more | Small

Abstract Black phosphorus (BP) has emerged as a promising 2D semiconductor due to its tunable bandgap, strong in‐plane anisotropy, and high carrier mobility. The recent development of black phosphorus nanoribbons … Abstract Black phosphorus (BP) has emerged as a promising 2D semiconductor due to its tunable bandgap, strong in‐plane anisotropy, and high carrier mobility. The recent development of black phosphorus nanoribbons (PNRs), quasi‐1D derivatives of BP, has introduced new opportunities for nano‐electronics, quantum materials, and energy applications. The transition from 2D to 1D nanostructures induces significant modifications in electronic structure, excitonic behavior, and charge transport, making PNRs a versatile platform for both fundamental studies and technological innovations. Advances in synthesis techniques, including electron‐beam lithography, liquid exfoliation, chemical vapor transport, and molecular beam epitaxy, have enabled the fabrication of high‐quality PNRs with precisely controlled dimensions and edge structures. These breakthroughs have facilitated their application in field‐effect transistors, solar cells, catalysis, and energy storage. Despite rapid progress, challenges remain in achieving scalable synthesis, stability enhancement, and precise control over edge states and functionalization. This review provides a comprehensive assessment of PNRs, covering their structural characteristics, fundamental physics properties, synthesis strategies, and emerging applications. Current challenges and future perspectives are discussed, aiming to guide the continued advancement of this rapidly evolving field.

Two‐Dimensional Indium Chalcogenides: From Fundamental Properties to Next‐Generation Optoelectronic Devices

2025-06-21

Waqas Ahmad , Muhammad Zubair Nawaz , Jamal Kazmi +3 more | Advanced Optical Materials

Abstract 2D indium chalcogenides, such as InSe and In 2 Se 3 , represent a significant class of functional materials characterized by tunable band gaps, exceptional carrier mobility, and robust … Abstract 2D indium chalcogenides, such as InSe and In 2 Se 3 , represent a significant class of functional materials characterized by tunable band gaps, exceptional carrier mobility, and robust light–matter interactions. This review thoroughly examines synthesis techniques, including chemical vapor deposition, molecular beam epitaxy, mechanical, and liquid exfoliation methods. It further highlights cutting‐edge characterization methodologies such as atomic force microscopy, scanning electron microscopy, and Raman spectroscopy, providing essential insights into the optoelectronic properties of these materials. The remarkable features of 2D indium chalcogenides facilitate their implementation in diverse optoelectronic applications, notably high‐performance photodetectors, polarization‐sensitive devices, and imaging systems. These materials also offer broadband spectral responsiveness and compatibility with van der Waals heterostructures, enhancing device performance. However, critical challenges such as scalability, environmental stability, and interface quality still hinder their widespread technological adoption. The review addresses these issues by recommending refined fabrication approaches, sophisticated interface engineering, and innovative encapsulation techniques. Finally, it outlines promising future directions, emphasizing scalable synthesis, hybrid device engineering, and the integration of machine learning, thereby paving the way for next‐generation photodetection technologies. This comprehensive review underscores the transformative potential of 2D indium chalcogenides and establishes a clear roadmap for overcoming existing challenges to realize their capabilities thoroughly.

Impact of Interfacial Configurations on the Growth of Few-Layer NbSe2 on Sapphire

2025-06-21

Shuaishuai Yin , R WANG , Lie Wang +6 more | Nano Letters

Two-dimensional van der Waals (vdW) heterostructures enable versatile material integration for advanced electronic and quantum devices. This study employs coherent Bragg rod analysis (COBRA) to study subangstrom interfacial effects in … Two-dimensional van der Waals (vdW) heterostructures enable versatile material integration for advanced electronic and quantum devices. This study employs coherent Bragg rod analysis (COBRA) to study subangstrom interfacial effects in three types of wafer-scale NbSe2 heterostructures grown on sapphire substrates via a two-step growth method. The sapphire surface Se-O mixing and nonstoichiometry from direct NbSe2 growth, the interface passivation with a graphene insert, and the complex growth mechanism with MoSe2 stacking are identified and quantified. These distinctly different interface chemical activities and structural morphologies lead to different growth behaviors and crystalline quality of the NbSe2 grown on top, which are correlated with the film superconductivity performance. Our findings highlight the importance of interfacial control in vdW heterostructure design, providing atom-level insights to optimize growth strategies for enhanced functionality.

Superconducting Gap and Its Little-Parks-like Oscillations with High-Order Harmonics in Lithium Intercalated 1T-TiSe2

2025-06-21

Jia-Yi Ji , Zongzheng Cao , Yi Hu +7 more | Nano Letters

The superconducting phase of doped 1T-TiSe2 is a fruitful playground for exploring exotic quantum phenomena such as the anomalous metal state and the spontaneously formed superconducting network. Here, we address … The superconducting phase of doped 1T-TiSe2 is a fruitful playground for exploring exotic quantum phenomena such as the anomalous metal state and the spontaneously formed superconducting network. Here, we address these emergent states by studying the superconducting gap of lithium intercalated TiSe2─a fundamental quantity that has remained unexplored so far. We fabricated a device that combines solid-state lateral lithium intercalation, resistance measurements, and tunneling spectroscopy. We successfully probed the superconducting gap of TiSe2 and revealed that the gap closing temperature well exceeds the transition temperature (Tc) expected from the Bardeen-Cooper-Schrieffer theory, indicating pronounced superconducting fluctuations even in a bulk-like system. Moreover, the symmetric gap persists even in the anomalous metal state, demonstrating the particle-hole symmetry of this exotic phase directly from the density of states. Finally, the superconducting gap shows magneto-oscillations with high-order harmonics, attesting to a rather regular structure of the intrinsic superconducting network.

MoS2 based 2D material photodetector array with high pixel density

2025-06-20

Russell L. T. Schwartz , Hao Wang , Chandraman Patil +2 more | Nanophotonics

Abstract Arrays of photodetector-based pixel sensors are ubiquitous in modern devices, such as smart phone cameras, automobiles, drones, laptops etc. Two-dimensional (2D) material-based photodetector arrays are a relevant candidate, especially … Abstract Arrays of photodetector-based pixel sensors are ubiquitous in modern devices, such as smart phone cameras, automobiles, drones, laptops etc. Two-dimensional (2D) material-based photodetector arrays are a relevant candidate, especially for applications demanding planar form factors. However, shortcomings in pixel density and prototyping without cross contamination limit technology adoption and impact. Also, while 2D material detectors offer high absorption, graphene’s closed bandgap results in undesirably high dark currents. Here, we introduce the experimental demonstration of dense planar photodetector arrays. We demonstrate a micrometer-narrow pitched 2D detector pixels and show this approach’s repeatability by verifying performing of a 16-pixel detector array. Such dense and repeatable detector realization is enabled by a novel, selective, contamination-free 2D material transfer system, that we report here in automated operation. The so realized photodetectors responsivity peaks at a high 0.8 A/W. Furthermore, we achieve uniform detector performance via bias voltage tuning calibration to maximize deployment. Lastly, we demonstrate 2D arrayed photodetectors not only on a silicon chip platform but verify array performance on flexible polymer substrates. Densley-arrayed, flat, bendable, and uniform performing photodetector pixels enable emerging technologies in the space where lightweight and reliable performance is required, such as for the smart phone and emerging VR/AR markets, but also for smart gadgets, wearables, and also for size-weight-power-constrained aviation and space platforms.

Charge transport study in MoS2 blended PCPDTBT based organic field effect transistor

2025-06-20

Pankaj Kumar , Sarita Yadav , Chandra Kant Singh +3 more | Applied Physics A

Pure Out-of-Plane Spin Polarization Induced by Rashba-Type Splitting

2025-06-20

Panfeng Cao , Sheng‐Yi Xie , Xianbin Li +1 more | Nano Letters

The generation of out-of-plane polarized spin currents presents a significant challenge in field-free spintronics. Traditional Rashba-type spin splitting typically generates in-plane spin currents, thereby limiting the development of high-density perpendicular … The generation of out-of-plane polarized spin currents presents a significant challenge in field-free spintronics. Traditional Rashba-type spin splitting typically generates in-plane spin currents, thereby limiting the development of high-density perpendicular magnetic memory and logic devices. Using first-principles calculations, we predict the emergence of pure out-of-plane Rashba-type spin splitting in monolayer transition metal dichalcogenides (TMDs). The momentum-dependent effective magnetic field governs both the direction of spin polarization and the form of spin splitting in the TMDs. Due to the presence of nonzero Berry curvature, this system holds promise for generating a purely out-of-plane polarized spin current, a phenomenon that may extend to other materials with broken in-plane symmetry.

High momentum two-dimensional propagation of emitted photoluminescence coupled with surface lattice resonance

2025-06-20

Y. M. Koo , Dong Kyo Oh , Jungho Mun +7 more | Light Science & Applications

Abstract Dramatic fluorescence enhancement in two-dimensional (2D) van der Waals materials (vdWMs) coupled to plasmonic nanostructures has the potential to enable ultrathin, flexible, and high-brightness illumination devices. However, addressing the … Abstract Dramatic fluorescence enhancement in two-dimensional (2D) van der Waals materials (vdWMs) coupled to plasmonic nanostructures has the potential to enable ultrathin, flexible, and high-brightness illumination devices. However, addressing the limitation of locally scattered small plasmon-enhanced areas remains challenging. Here, we present a 2D plasmonic enhancement of photoluminescence (PL) spanning nearly 800 μm 2 , enabled by surface lattice resonance (SLR) in a 2D vdWM-Au slot lattice hybrid. The Au slot lattice is designed and fabricated using Babinet’s principle and Rayleigh’s anomaly to maximize radiative decay rate and induce non-local photo-excitation in a MoSe 2 monolayer. For emitted PL coupled with SLR, enhanced by up to 32-fold, we investigate its in-plane directivity and long-range propagation using angle- and space-resolved spectroscopic PL measurements. Our experiment reveals that a nearly 800 μm 2 2D luminescent sheet can be achieved regardless of the size of the MoSe 2 crystal, even with a sub-μm 2 flake. This work provides a new type of ultrabright, large-area 2D luminescent material, suitable for a range of optical illumination, communication, and sensing devices.

Significant electron-magnon scattering in layered ferromagnet Cr2Te3

2025-06-20

Yujun Wang , Shunzhen Wang , Masashi Kawaguchi +7 more | Communications Physics

2p interlayer exciton revealed by hybridization in bilayer MoS2

2025-06-20

Chun Hung Lui , Soonyoung Cha , Zhaoran Xu +7 more | Research Square (Research Square)

<title>Abstract</title> Interlayer excitons—bound electron–hole pairs residing in separate layers—feature long lifetimes and Stark-tunable energies, making them promising for excitonic devices and dipolar quantum phenomena. While most prior studies have focused … <title>Abstract</title> Interlayer excitons—bound electron–hole pairs residing in separate layers—feature long lifetimes and Stark-tunable energies, making them promising for excitonic devices and dipolar quantum phenomena. While most prior studies have focused on the 1<italic>s</italic> ground state, here we reveal the 2<italic>p</italic> interlayer exciton along with a Rydberg series of interlayer states extending from 1<italic>s</italic> to 4<italic>s</italic> in bilayer MoS2. The 2<italic>p</italic> state, optically dark at zero field, acquires oscillator strength under an applied electric field through hybridization with the intralayer A exciton. Due to its finite angular momentum, it exhibits distinct selection rules and <italic>g</italic>-factors in agreement with theoretical expectations. Strikingly, whereas the intralayer Rydberg series fades beyond the 2<italic>s</italic> state, the interlayer series remains optically visible up to 4<italic>s</italic>. This extended visibility arises from hybridization with the intralayer B exciton, which transfers oscillator strength to higher interlayer states and effectively brightens the entire series. Simulations further uncover a novel coupling mechanism between <italic>s</italic>-like intralayer and <italic>p</italic>-like interlayer excitons—one driven not by conventional electron–hole Coulomb interactions, but by interlayer conduction band mixing. These findings establish bilayer MoS2 as a versatile platform for exploring tunable excitonic phenomena.

Interlayer interaction and Davydov splitting in antiferromagnetic few-layer NiPS3

2025-06-20

Manh Hong Nguyen , Giung Park , Je‐Geun Park +1 more | npj Quantum Materials

Computational insights into graphene/WS2 van der Waals heterostructure as a potential sensor for airborne environmental pollutants via first-principles calculations

2025-06-20

Deepak Arumugam , Sangaraju Shanmugam , Akilesh Muralidharan +1 more | Physica B Condensed Matter

Anisotropic electronic and excitonic properties of monolayer SiP2 from the first-principles GW-BSE calculations

2025-06-20

Zichen Wang , Benshu Fan , Peizhe Tang | Chinese Physics B

Abstract We investigate electronic structures and excitonic properties of monolayer SiP 2 in the framework of the first-principles GW plus Bethe-Salpeter equation (GW-BSE) calculations. Within the G 0 W 0 … Abstract We investigate electronic structures and excitonic properties of monolayer SiP 2 in the framework of the first-principles GW plus Bethe-Salpeter equation (GW-BSE) calculations. Within the G 0 W 0 approximation, monolayer SiP 2 is identified as a direct gap semiconductor with an electronic gap of 3.14 eV, and the excitons exhibit the hybrid-dimensional nature similar to their bulk counterpart. The optical absorption spectra reveal pronounced excitonic effects with strong anisotropy: the first bright exciton shows a binding energy of 840 meV under the x -polarized light versus 450 meV for y polarization. We further analyze the symmetry origins of the polarization-dependent optical selection rules through group theory. The binding energy difference between x - and y -polarizations is attributed to the intrinsic character of excitons: flat-band excitons under the x -polarized light and conventional excitons localized at a single k point under the y -polarized light. Our work enhances the understanding of excitonic behavior in monolayer SiP 2 and highlights its potential for polarization-sensitive and directionally tunable optoelectronic applications.

Intrinsic Magnetism and Field‐Driven Spin Alignment in NiI2 Revealed by X‐ray Magnetic Spectroscopy

2025-06-20

Ethan L. Arnold , Emily Heppell , Rabindra Basnet +7 more | physica status solidi (RRL) - Rapid Research Letters

This study investigates the intrinsic magnetism and field‐driven spin alignment in NiI 2 using X‐ray absorption spectroscopy and X‐ray magnetic circular dichroism (XMCD). NiI 2 , a van der Waals … This study investigates the intrinsic magnetism and field‐driven spin alignment in NiI 2 using X‐ray absorption spectroscopy and X‐ray magnetic circular dichroism (XMCD). NiI 2 , a van der Waals material, exhibits helimagnetic and type‐II multiferroic behavior. This study reveals robust XMCD signals across paramagnetic, antiferromagnetic, and helimagnetic phases under applied out‐of‐plane fields up to 6 T, while no net moment emerges at zero field. Atomic multiplet calculations confirm a covalent Ni 3 d ground state with a significantly reduced spin moment. The results establish the intrinsic nature of NiI 2 's magnetism and clarify its field‐driven spin alignment mechanism. This comprehensive spectroscopic characterization lays the foundation for future applications of NiI 2 in advanced spintronic and multiferroic devices, despite challenges posed by its low transition temperature in the monolayer limit. Future research should focus on enhancing its critical temperature through doping, strain engineering, or heterostructure fabrication.

Polarization-controlled switching of magnetic anisotropy in CrSe2/Sc2CO2 multiferroic heterostructures

2025-06-20

Zhijian He , Daifeng Zou | Journal of Physics Condensed Matter

Abstract Recent breakthroughs in two-dimensional (2D) magnetic materials have unveiled intriguing phenomena in low-dimensional ferromagnetic (FM) systems. However, their integration into spintronic devices faces challenges due to the predominant in-plane … Abstract Recent breakthroughs in two-dimensional (2D) magnetic materials have unveiled intriguing phenomena in low-dimensional ferromagnetic (FM) systems. However, their integration into spintronic devices faces challenges due to the predominant in-plane (IP) orientation of the easy magnetization axis. Achieving nonvolatile electrical control over magnetic anisotropy in such systems is essential for advancing next-generation spintronic technologies. In this work, we introduce a multiferroic van der Waals (vdW) heterostructure design that enables dynamic manipulation of magnetoelectric coupling in 2D ferromagnets. By investigating the CrSe 2 /Sc 2 CO 2 heterostructure—comprising a FM CrSe 2 monolayer coupled with a ferroelectric Sc 2 CO 2 layer—we demonstrate reversible switching of magnetic anisotropy via polarization engineering. Crucially, the system exhibits a controllable transition of the easy magnetization axis between IP and out-of-plane configurations, driven by ferroelectric polarization reversal. This magnetoelectric coupling mechanism unlocks novel functionalities for nonvolatile memory devices and adaptive logic components. Our findings provide a foundational strategy for voltage-free magnetic anisotropy tuning in vdWs heterostructures while elucidating interfacial magnetoelectric effects in low-dimensional systems.

Dielectric metasurface enhanced performance in multilayer WS2 photodetector

2025-06-20

Huijuan Zhao , Weiqi Wang , Huanlin Ding +7 more | Science China Information Sciences

Tunable magnetic switching and electronic structure in Cr3+/Fe3+ Co-substituted 2D SnS2 nanosheets

2025-06-19

M. Charles Robert , N. Pavithra | Materials Science in Semiconductor Processing

Semiconductor-half metal transition in C6N6 nanoribbons by edge passivation with F and O atoms

2025-06-19

Adeleh Vatankhahan , Tayebeh Movlarooy | Indian Journal of Physics

Excited-State Dynamics in Monolayer Black Phosphorus: Exciton Relaxation Modulated by Defects

2025-06-19

Jingyi Qiao , Zihan Yang , Yan Zheng +3 more | The Journal of Physical Chemistry A

Black phosphorus (BP) is a promising candidate for diverse optoelectronic and solar energy applications. The efficiency of these devices, however, is affected by the intrinsic defects of BP. In this … Black phosphorus (BP) is a promising candidate for diverse optoelectronic and solar energy applications. The efficiency of these devices, however, is affected by the intrinsic defects of BP. In this study, we employ static electronic structure calculations combined with the linear-response time-dependent density functional theory (LR-TDDFT)-based nonadiabatic dynamics simulation method, which explicitly incorporates excitonic effects, to systematically investigate the regulatory effects of six distinct defect types on the excited-state dynamics in monolayer BP. Defect engineering in pristine BP drastically modifies both ground-state (e.g., density of states) and excited-state properties (e.g., absorption spectrum and exciton size). Such changes result in pronounced differences in exciton relaxation dynamics across various defect configurations. Among all defect models, the DV-(5|8|5)-2 configuration manifests unparalleled characteristics: (i) narrowest band gap (1.43 eV), (ii) maximum exciton size variation across excited-states, (iii) two absorption peaks exhibiting a substantial intensity contrast, and (iv) shortest exciton relaxation time scale. This study offers valuable insights into the influence of defects on the electronic and excitonic properties of BP, laying a foundation for the rational design of BP-based optoelectronic materials.

The effects of electric field and strain on the VCl2/WTe2 van der Waals heterojunction

2025-06-19

Lü Yang , Fang Zhu , Lin Zhong +5 more | Journal of Physics D Applied Physics

Abstract two-dimensional (2D) van der Waals (vdW) magnetic materials providean ideal platform for exploring long-range magnetic ordering at the 2D limit andshow promising applications in next-generation spintronics devices. In this … Abstract two-dimensional (2D) van der Waals (vdW) magnetic materials providean ideal platform for exploring long-range magnetic ordering at the 2D limit andshow promising applications in next-generation spintronics devices. In this works,VCl2/WTe2 van der Waals heterostructures are investigated to study the electronicstructure and magnetic anisotropy, as well as their modulation via external electricfield and biaxial strain in the plane based on first-principles calculations. The resultsshow that the VCl2/WTe2 heterostructure is semiconducting with a band gap of 0.82eV, a 0.4 meV valley splitting and a system MAE of 0.033 mJ/m2 after taking intoaccount of spin-orbital coupling (SOC). The application of bi-axial strain and veticalelectric field to the heterostructures changes the electronic structure. A maximummagnetic anisotropy energy (MAE) of -0.5 mJ/m2 and a maximum valley splittingvalue (4.9 meV) are found for the VCl2/WTe2 heterostructures at a strain of -6%.The system MAE reaches 3.2 mJ/m2 at an electric field strength of 0.3 V/Å, andreaches 0.96 mJ/m2 at -0.3 V/Å. It also reaches a maximum valley splitting of 3.53meV. Under the modulation of biaxial strains and positive and negative electric fields,the VCl2/WTe2 heterostructures have significant tunable electronic structure andmagnetic anisotropy, which suggests that the VCl2/WTe2 heterostructure has potentialapplications in spintronic devices.

Strong room-temperature ferromagnetism and magnetocaloric effect in anisotropic two-dimensional layered chromium indium telluride

2025-06-19

Yong Wang , Dingyi Yang , Zixuan Cheng +7 more | Materials Futures

Abstract Two-dimensional (2D) layered ferromagnets offer exciting opportunities for studying magnetic phenomena and developing advanced spintronic devices. In this study, we experimentally present a 2D chromium indium telluride (Cr6In2Te12, CIT) … Abstract Two-dimensional (2D) layered ferromagnets offer exciting opportunities for studying magnetic phenomena and developing advanced spintronic devices. In this study, we experimentally present a 2D chromium indium telluride (Cr6In2Te12, CIT) that exhibits robust room-temperature ferromagnetism and remarkable magnetic properties.CIT demonstrates a high Curie temperature of 320 K, record-high room-temperature saturation magnetization (~52.3 emu/g), and a strong magnetocaloric effect. Notably, with decreasing thickness, it transitions from a metallic ferromagnet to a ferromagnetic semiconductor. Besides, CIT displays complex magnetocrystalline anisotropy with multiple easy axes and signatures of an abnormal phase transition, characterized by anisotropic anomalies in field- and temperature-dependent magnetization curves. Furthermore, CIT shows anisotropic magnetic interactions and critical exponents consistent with a mean-field model. These exceptional properties position CIT as a promising 2D high-TC ferromagnetic semiconductor for multidisciplinary applications, particularly in high-performance spintronic devices.&#xD;

Theoretical Insight into Hydrogen-Assisted Chemical Vapor Deposition of MoTe2

2025-06-19

Haocheng Wang , Xiaolong Zou | ACS Materials Letters

Engineering spin textures in 2D chromium nitride through half halogenation

2025-06-19

H Asserghine , L.B. Drissi , A. Elkhou +3 more | Physica Scripta

Abstract This study explores the magnetic behavior of two-dimensional half-halogenated chromium nitride (CrN) materials, namely F-CrN and Cl-CrN, using density functional theory (DFT) and low-energy models. Halogen doping breaks the … Abstract This study explores the magnetic behavior of two-dimensional half-halogenated chromium nitride (CrN) materials, namely F-CrN and Cl-CrN, using density functional theory (DFT) and low-energy models. Halogen doping breaks the symmetry of CrN, inducing magnetic properties and enhancing the Dzyaloshinskii-Moriya interaction (DMI), a key mechanism for stabilizing complex spin textures. Simulations reveal that Cl-CrN stabilizes Néel-type skyrmions at magnetic fields of 50 T, which is achievable with high-field superconducting or resistive magnets. However, F-CrN requires much higher fields (275 T) to support antiskyrmions, reflecting the stronger DMI induced by fluorine. Accessible using pulsed magnetic field facilities, this makes the skyrmionic phases in halogenated CrN experimentally realizable. Controlling skyrmion phases via halogenation highlights the potential of these materials for spintronic applications, offering pathways for energy-efficient, robust data storage and processing technologies.

Room‐Temperature Remote Optical Probing of Interlayer Exciton Transport in Van Der Waals Heterostructures

2025-06-19

Huilin Zhang , Chunjiao Wang , Yuexing Xia +7 more | Laser & Photonics Review

Abstract Interlayer excitons in transition metal dichalcogenide (TMD) heterostructures feature long lifetime and superior transport properties, yet their room‐temperature optical tracking remains challenging due to weak emission. Here, remote optical … Abstract Interlayer excitons in transition metal dichalcogenide (TMD) heterostructures feature long lifetime and superior transport properties, yet their room‐temperature optical tracking remains challenging due to weak emission. Here, remote optical probing of interlayer exciton transport in a TMD heterostructure at room temperature is demonstrated. Optically generated interlayer excitons diffuse through the heterostructure and dissociate at boundaries, where liberated carriers further migrate into monolayers and recombine with native charges to give bright intralayer emission. With the intralayer emission as a remote optical probe, unique properties of interlayer exciton transport are observed including the characteristic decay length of ≈4.5 µm, the power‐dependent phase transition between exciton gas and electron‐hole plasma, the thermally activated transport enhancement, and the fast diffusivity of ≈2100 cm 2 s −1 . The research offers a new route for the study of interlayer exciton transport with enhanced visibility, which paves the way for room‐temperature exciton transistors and circuits.

Localized Spin Textures Stabilized by Geometry‐Induced Strain in 2D Magnet Fe3GeTe2

2025-06-18

Yuhan Sun , M. T. Birch , Simone Finizio +7 more | Advanced Materials

Abstract Strain engineering promises to enable manipulation and control of the properties of exfoliated flakes of 2D van der Waals (vdW) ferromagnets for spintronic applications. However, while previous studies of … Abstract Strain engineering promises to enable manipulation and control of the properties of exfoliated flakes of 2D van der Waals (vdW) ferromagnets for spintronic applications. However, while previous studies of strain effects have focused on global properties, the impact on local magnetic spin textures remains unexplored. Here, manipulation of magnetism in the 2D ferromagnet Fe 3 GeTe 2 (FGT) is demonstrated using geometry‐induced strain. Employing scanning transmission X‐ray microscopy (STXM), the effects of spatially varying strain profiles on the magnetic order of FGT sheets stamped onto micropillar arrays are directly visualized. It is found that the in‐plane strain components, with magnitudes <0.5%, locally elevate the Curie temperature of FGT by 10 K, stabilizing magnetic domains near the pillar corners. These domains include skyrmions and higher‐order topological spin textures such as skyrmioniums and skyrmion bags. The possibility to locally seed and control topological spin textures via strain opens new avenues for future spin‐based information technologies.