2D Materials最新文献

{"title":"Monolayer WS2 electro- and photo-luminescence enhancement by TFSI treatment","authors":"A. Cadore, B. L. T. Rosa, I. Paradisanos, S. Mignuzzi, D. De Fazio, Eugene Alexeev, A. Dagkli, J. Muench, Georgios Kakavelakis, Sachin M. Schinde, D. Yoon, S. Tongay, Kenji Watanabe, T. Taniguchi, E. Lidorikis, I. Goykhman, G. Soavi, A. C. Ferrari","doi":"10.1088/2053-1583/ad1a6a","DOIUrl":"https://doi.org/10.1088/2053-1583/ad1a6a","url":null,"abstract":"\u0000 Layered material heterostructures (LMHs) can be used to fabricate electroluminescent devices operating in the visible spectral region. A major advantage of LMH-light emitting diodes (LEDs) is that electroluminescence (EL) emission can be tuned across that of different exciton complexes (e.g. biexcitons, trions, quintons) by controlling the charge density. However, these devices have an EL quantum efficiency as low as~10−4%. Here, we show that the superacid bis-(triuoromethane)sulfonimide (TFSI) treatment of monolayer WS2-LEDs boosts EL quantum efficiency by over one order of magnitude at room temperature. Non-treated devices emit light mainly from negatively charged excitons, while the emission in treated ones predominantly involves radiative recombination of neutral excitons. This paves the way to tunable and efficient LMH-LEDs.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"55 4","pages":""},"PeriodicalIF":5.5,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139450854","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Pressure-driven superconductivity in layered isostructural germanium phosphides","authors":"Junwei Huang, Caorong Zhang, K. Zhai, Feng Qin, Lingyi Ao, Zeya Li, Ling Zhou, Ming Tang, Xueting Dai, Caiyu Qiu, Yi Zhang, F. Wen, Zhongyuan Liu, Hongtao Yuan","doi":"10.1088/2053-1583/ad1a71","DOIUrl":"https://doi.org/10.1088/2053-1583/ad1a71","url":null,"abstract":"The discovery of superconductivity and its modulation are long-standing cutting-edge research topics in condensed matter physics. As a powerful tool, the high-pressure technique can be used to achieve novel superconductors and tune their physical properties. One typical example is binary germanium phosphides with different stoichiometries, which exhibit abundant physical properties with layered lattice structures similar to blue phosphorus. The detailed phase diagrams of the Ge–P systems are important for understanding the influence of stoichiometry on pressure-driven superconductivity, but it remains unexplored. Here, we measured and compared the detailed superconducting phase diagrams of the Ge–P systems of layered isostructural germanium phosphides GeP3 and GeP5 under pressure. Even though these two binary phosphides exhibit obviously different atomic occupations in the crystal structure due to their distinct stoichiometric ratios, the onset superconducting transition temperatures Tc of GeP3 and GeP5 both show dramatic enhancements from ∼2.5 K at 12.0 GPa to the maximum values of ∼9.0 K at 28.0 GPa, which are higher than those of other binary metal phosphides. Such pressure-enhanced superconductivity therein is accompanied by significant pressure-induced phonon mode softening, which is confirmed via in situ high-pressure Raman measurements. Our observations deepen the physical understanding of pressure-driven superconductivity in phosphorous-rich layered compounds and pave the way for potential applications in microsuperconducting devices.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"38 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139451209","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spatially-indirect and hybrid exciton-exciton interaction in MoS2 homobilayers","authors":"Valeria Maslova, Nina Voronova","doi":"10.1088/2053-1583/ad1a6c","DOIUrl":"https://doi.org/10.1088/2053-1583/ad1a6c","url":null,"abstract":"\u0000 Interlayer excitons in transition-metal dichalcogenide (TMD) bilayers, alongside their interplay with direct excitonic species, are supposed to offer a pathway towards robust nonlinearity, enabling the exploration of many-body quantum effects. We present a theoretical investigation of interaction among various exciton species within these structures where Coulomb attraction and repulsion are subject to reduced screening. For a homobilayer MoS2, we examine both direct, spatially-indirect, and hybridised excitons, considering the effects of direct and exchange interaction of electrons and holes distributed across one or different layers. Similar physics arises in perfectly aligned twisted TMD heterobilayers which support the direct-to-indirect exciton hybridisation. Deriving the exciton-exciton interaction matrix elements, we unveil a distinct non-monotonic dependence of the interaction on transferred momentum, changing sign from repulsive to attractive even for ground-state excitons, and compare our results with existing calculations for monolayers. Our findings demonstrate that for large momenta involved in high-density effects (strongly correlated phases), the interaction is chiefly governed by the prevailing attractive exchange component. At the same time, at small momenta that are more relevant for rarefied systems, we find that the enhancement of the interaction constant for dipolar species compared to intralayer non-dipolar excitons may be hindered by the surrounding medium. We draw comparisons with existing experiments and discuss the implications of our findings on the collective effects in TMD-based systems of excitons and exciton-polaritons.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"112 4","pages":""},"PeriodicalIF":5.5,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139387981","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Area-selective chalcogenization of transition metals through graphene mask","authors":"Jaekwang Song, Jong-Hwan Lee, Seoungwoong Park, Yunseok Lee, Chan-Jin Kim, Minchul Ahn, Byung Hee Hong","doi":"10.1088/2053-1583/ad1a6e","DOIUrl":"https://doi.org/10.1088/2053-1583/ad1a6e","url":null,"abstract":"Area-selection reactions have been extensively investigated to control or change physicochemical properties of substances with micro- or nanoscale precision. Several polymeric materials called photoresists have been used to mask and pattern the specific region, which can block chemical reactions or deposition. However, they are not suitable for certain chemical reaction since they are vulnerable to high temperature. Here, we report the graphene mask to achieve area-selective chalcogenization, which is performed at high temperature by chemical vapor deposition method. Due to its physicochemical properties, graphene does not allow chalcogen precursor gases to penetrate into metal films. Several characterizations are performed to prove the successful sulfurization and selenization of molybdenum and tungsten films. As an application, WS2 field-effect transistors with graphene mask are fabricated, and they show the typical characteristics of transistors successfully. Therefore, we expect that graphene-assisted area-selective reaction can be utilized for various fields such as semiconductors, sensors, and etc.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"53 15","pages":""},"PeriodicalIF":5.5,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139451826","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Exploring graphene-substrate interactions: Plasmonic excitation in Sn-intercalated epitaxial graphene","authors":"Zamin Mamiyev, C. Tegenkamp","doi":"10.1088/2053-1583/ad1a70","DOIUrl":"https://doi.org/10.1088/2053-1583/ad1a70","url":null,"abstract":"\u0000 Graphene plasmons, including those in intercalated graphene, are an important research focus, with the promise of enabling light manipulation and providing a unique platform for gaining fundamental insights into many-body electronic interactions. In the present work, we discuss the results of low-energy plasmonic excitations in epitaxial quasi-free monolayer graphene formed by intercalation of Sn beneath the buffer layer on 4H-SiC(0001). The quantitative analysis of the sheet plasmon dispersion revealed that the Sn-induced ($1times1$) interface is metallic and results in formation of charge-neutral graphene. A redshift of the 2D plasmon was found, but only after doping with potassium. The Sn-diluted interface, revealing a ($sqrt{3}timessqrt{3}$) reconstruction and resulting in intrinsically n-type doped graphene, behaves comparably to the buffer layer for epitaxial monolayer graphene. Furthermore, it seems that a dipolar coupling of the longitudinal charge density fluctuations in graphene to the interface layer triggers the formation and the loss energy of a plasmonic multipole component, which therefore makes it suitable for studying proximity effects of excitations in electronically weakly coupled 2D heterosystems.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"4 8","pages":""},"PeriodicalIF":5.5,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139450931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Exfoliation of graphite to turbostratic graphene","authors":"K. V. Kumar, Aminul Islam, P. S. Kiran, Niranjan Pandit, Rahul Kumar, Satish Indupuri, A. Keshri","doi":"10.1088/2053-1583/ad1675","DOIUrl":"https://doi.org/10.1088/2053-1583/ad1675","url":null,"abstract":"\u0000 Here, we exfoliated high-quality turbostratic graphene with a clean interface at a high production rate (10 g/h) directly from graphite using an industrial-friendly technique i.e., plasma spraying, catching note of its growing global interest. The reduction of the (002) X-ray diffraction peak and the transparent scanning electron microscope (SEM) image are used to characterize the exfoliation. The thickness of exfoliated graphene layers is measured using an atomic force microscope (AFM). Turbostratic nature (twist) in graphene is identified based on the appearance of three Raman combination bands (TS1, TS2, and TS3) between 1800 cm-1 and 2300 cm-1. The twist between the layers is precisely measured using selected area electron diffraction (SAED), and the turbostratic nature is confirmed by observing a moiré pattern utilizing a high-resolution transmission electron microscope (HR-TEM). The produced turbostratic graphene exhibited large variability in twist angles (2⁰-30⁰) with a visible moiré pattern. The high crystalline quality and clean interface between single layers of graphene were confirmed by the moiré pattern and SAED. Later, we demonstrated the mechanism underlying the twist in our exfoliated graphene, which could open the way for the production of high-quality turbostratic graphene with clean interfaces.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"20 4","pages":""},"PeriodicalIF":5.5,"publicationDate":"2023-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138965758","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Delving into the anisotropic interlayer exchange in bilayer CrI3","authors":"Srdjan Stavrić, Paolo Barone, Silvia Picozzi","doi":"10.1088/2053-1583/ad1313","DOIUrl":"https://doi.org/10.1088/2053-1583/ad1313","url":null,"abstract":"Bilayer CrI₃ attracted much attention due to stacking-induced switching between the layered ferromagnetic and antiferromagnetic order. This discovery brought under the spotlight the interlayer Cr–Cr exchange interaction, which despite being much weaker than the intralayer exchange, plays an important role in shaping the magnetic properties of bilayer CrI₃. In this work we delve into the anisotropic part of the interlayer exchange with the aim to separate the contributions from the Dzyaloshinskii–Moriya (DMI) and the Kitaev interactions (KI). We leverage the density functional theory calculations with spin Hamiltonian modeling and develop an energy mapping procedure to assess these anisotropic interactions with <inline-formula>\u0000<tex-math><?CDATA $mumathrm{eV}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mi>μ</mml:mi><mml:mrow><mml:mi mathvariant=\"normal\">e</mml:mi><mml:mi mathvariant=\"normal\">V</mml:mi></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"tdmad1313ieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> accuracy. After inspecting the rhombohedral and monoclinic stacking sequences of bilayer CrI₃, we reveal a considerable DMI and a weak interlayer KI between the sublattices of a monoclinic bilayer. We explain the dependence of DMI and KI on the interlayer distance, stacking sequence, and the spin–orbit coupling strength, and we suggest the dominant superexchange processes at play. In addition, we demonstrate that the single-ion anisotropy in bilayer CrI₃ is highly stacking-dependent, increasing by 50% from monoclinic to rhombohedral bilayer. Remarkably, our findings prove that iodines are highly efficient in mediating the DMI across the van der Waals gap, much owing to spatially extended 5<italic toggle=\"yes\">p</italic> orbitals which feature strong spin–orbit coupling. Our study gives promise that the interlayer chiral control of spin textures, demonstrated in thin metallic films where the DMI is with a much longer range, can be achieved with similar efficiency in semiconducting two-dimensional van der Waals magnets.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"33 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2023-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138686980","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Paramagnetic two-dimensional silicon-oxide from natural silicates","authors":"Preeti Lata Mahapatra, Caique Campos de Oliveira, Gelu Costin, Suman Sarkar, Pedro A S Autreto, Chandra Sekhar Tiwary","doi":"10.1088/2053-1583/ad10b9","DOIUrl":"https://doi.org/10.1088/2053-1583/ad10b9","url":null,"abstract":"Silicon dioxide’s potential for having magnetic properties is fascinating, as combining its electronic capabilities with magnetic response seems promising for spintronics. In this work, the mechanisms that drive the change from diamagnetic behavior in pure silicates like SiO₂ to paramagnetic behavior in transition metal-doped silicates like Rhodonite silicate (CaMn₃Mn(Si₅O₁₅)) are explored. This naturally occurring Rhodonite (R)-silicate was thinned down while retaining its magnetic properties by liquid-phase scalable exfoliation. Exfoliating R-silicate into the two-dimensional (2D) structure by LPE increases magnetic coercivity, and the internal resistance to demagnetization (ΔHc) up to ∼23.95 Oe compared to 7.08 Oe for its bulk phase. DFT spin-polarized calculations corroborate those findings and explain that the origin of the magnetic moment comes mainly from the Mn in the doped 2D silicate due to the asymmetrical components of the Mn d and Si p states in the valence band. This result is further illustrated by the spin component differential charge densities showing that Mn and Si atoms display a residual up spin charge. Rhodonite’s unusual magnetic behavior has considerable potential for spintronics, data storage, and sensing technologies. Understanding the complex relationships between the structural, magnetic, and electronic properties of silicates is essential for developing new materials and composites as well as for driving future research.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"54 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2023-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138687446","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Controllable superconducting to semiconducting phase transition in topological superconductor 2M-WS2","authors":"Sabin Gautam, Joseph McBride, William R Scougale, Piumi I Samarawickrama, Danilo De Camargo Branco, Peilin Yang, ZhuangEn Fu, Wenyong Wang, Jinke Tang, Gary J Cheng, John Ackerman, TeYu Chien, Brian M Leonard, Jifa Tian","doi":"10.1088/2053-1583/ad10bb","DOIUrl":"https://doi.org/10.1088/2053-1583/ad10bb","url":null,"abstract":"The investigation of exotic properties in two-dimensional (2D) topological superconductors has garnered increasing attention in condensed matter physics, particularly for applications in topological qubits. Despite this interest, a reliable way of fabricating topological Josephson junctions (JJs) utilizing topological superconductors has yet to be demonstrated. Controllable structural phase transition presents a unique approach to achieving topological JJs in atomically thin 2D topological superconductors. In this work, we report the pioneering demonstration of a structural phase transition from the superconducting to the semiconducting phase in the 2D topological superconductor 2M-WS₂. We reveal that the metastable 2M phase of WS₂ remains stable in ambient conditions but transitions to the 2H phase when subjected to temperatures above 150 °C. We further locally induced the 2H phase within 2M-WS₂ nanolayers using laser irradiation. Notably, the 2H phase region exhibits a hexagonal shape, and scanning tunneling microscopy uncovers an atomically sharp crystal structural transition between the 2H and 2M phase regions. Moreover, the 2M to 2H phase transition can be induced at the nanometer scale by a 200 kV electron beam. The electrical transport measurements further confirmed the superconductivity of the pristine 2M-WS₂ and the semiconducting behavior of the laser-irradiated 2M-WS₂. Our results establish a novel approach for controllable topological phase change in 2D topological superconductors, significantly impacting the development of atomically scaled planar topological JJs.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"21 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2023-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138686722","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The role of solvent interfacial structural ordering in maintaining stable graphene dispersions","authors":"Urvesh Patil, Nuala M Caffrey","doi":"10.1088/2053-1583/ad10ba","DOIUrl":"https://doi.org/10.1088/2053-1583/ad10ba","url":null,"abstract":"Liquid phase exfoliation is the most promising method for the low-cost, scalable production of two-dimensional nanosheets from their bulk counterparts. Extensive exfoliation occurs in most solvents due to the huge amount of energy introduced by sonication or shear mixing. However, the subsequent dispersion is not always stable, with extensive reaggregation occurring in some solvents. Identifying the optimal solvent for a particular layered material is difficult and requires a fundamental understanding of the mechanism involved in maintaining a stable dispersion. Here, we use molecular dynamics calculations to show that when graphene is immersed in a solvent, distinct solvation layers are formed irrespective of the choice of solvent and their formation is energetically favourable for all considered solvents. However, energetic considerations such as these do not explain the experimental solvent-dependence of the dispersion concentration. Instead, we find that solvents with high diffusion coefficients parallel to the graphene layer result in the lowest experimental concentration of graphene in solution. This can be explained by the enhanced ease of reaggregation in these solvents. Solvents with smaller diffusion coefficients result in higher experimental graphene concentrations as reaggregation is prevented. In the low diffusion limit, however, this relationship breaks down. We suggest that here the concentration of graphene in solution depends primarily on the separation efficiency of the initial exfoliation step. Based on this, we predict that the concentration of exfoliated graphene in solvents such as benzaldehyde and quinoline, which have low diffusion constants, can be increased dramatically by careful tuning of the experimental sonication parameters.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"22 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2023-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138687384","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}