Pub Date : 2024-10-02DOI: 10.1038/s41699-024-00502-8
Martin Dahlqvist, Johanna Rosen
MXenes are a diverse family of two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides. They can be synthesized through both top-down approaches, such as selective etching of A-layers from MAX phases using acids or molten salts, and bottom-up approaches, such as direct synthesis using chemical vapor deposition. However, the degree of the surface termination coverage depends on the synthesis route and is one key parameter for controlling its properties. This study focuses on halogen- and chalcogen-terminated MXenes, particularly M2CTx where M = Ti, Zr, V, Nb, Ta, and T = S, Se, Te, Cl, Br, I, and with surface termination coverage ranging from 100% (ideal, x = 2) to 50% (x = 1). The incorporation of oxygen on vacant termination sites was also evaluated. Using density functional theory (DFT) calculations, we investigated the structural, electronic, and mechanical properties of these MXenes. Our findings reveal that non-ideal termination coverage (x < 2) is more favorable for MXenes terminated with a larger size of T, such as Ti2CBrx, Nb2CClx, and Ta2CClx, and leads to mixed termination sites and lower binding energies. A reduced binding energy may facilitate delamination into single sheets, however, too low termination coverage may also cause structural collapse. Electronic properties showed an increased number of states at the Fermi level under non-ideal coverage, potentially enhancing the conductivity. Mechanically, we find the moduli of MXenes to be comparable to other 2D materials, such as transition metal chalcogenides and hexagonal boron nitride, indicating their suitability for applications requiring flexibility and durability. This study underscores the potential of tailoring MXene properties through precise control of termination coverage and composition, paving the way for enhanced application-specific performance.
MXenes 是二维（2D）过渡金属碳化物、氮化物和碳氮化物的一个多样化家族。它们既可以通过自上而下的方法合成，如使用酸或熔盐从 MAX 相中选择性蚀刻 A 层，也可以通过自下而上的方法合成，如使用化学气相沉积直接合成。然而，表面终止覆盖的程度取决于合成途径，也是控制其特性的一个关键参数。本研究的重点是卤素和缩醛基封端 MXenes，特别是 M2CTx，其中 M = Ti、Zr、V、Nb、Ta，T = S、Se、Te、Cl、Br、I，表面封端覆盖率从 100% （理想 x = 2）到 50% （x = 1）不等。此外，还评估了氧在空置终止位点上的结合情况。利用密度泛函理论（DFT）计算，我们研究了这些 MXenes 的结构、电子和机械特性。我们的研究结果表明，非理想终止覆盖（x <2）更有利于以较大尺寸的 T（如 Ti2CBrx、Nb2CClx 和 Ta2CClx）终止的 MXenes，并导致混合终止位点和较低的结合能。结合能的降低可能会促进单片的分层，但过低的终止覆盖率也可能导致结构崩溃。电子特性显示，在非理想覆盖率下，费米级上的状态数量增加，从而有可能提高导电性。在力学方面，我们发现 MXenes 的模量与其他二维材料（如过渡金属瑀和六方氮化硼）相当，这表明它们适用于需要灵活性和耐久性的应用。这项研究强调了通过精确控制终止覆盖和组成来定制 MXene 特性的潜力，为提高特定应用性能铺平了道路。
{"title":"Chalcogen and halogen surface termination coverage in MXenes—structure, stability, and properties","authors":"Martin Dahlqvist, Johanna Rosen","doi":"10.1038/s41699-024-00502-8","DOIUrl":"10.1038/s41699-024-00502-8","url":null,"abstract":"MXenes are a diverse family of two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides. They can be synthesized through both top-down approaches, such as selective etching of A-layers from MAX phases using acids or molten salts, and bottom-up approaches, such as direct synthesis using chemical vapor deposition. However, the degree of the surface termination coverage depends on the synthesis route and is one key parameter for controlling its properties. This study focuses on halogen- and chalcogen-terminated MXenes, particularly M2CTx where M = Ti, Zr, V, Nb, Ta, and T = S, Se, Te, Cl, Br, I, and with surface termination coverage ranging from 100% (ideal, x = 2) to 50% (x = 1). The incorporation of oxygen on vacant termination sites was also evaluated. Using density functional theory (DFT) calculations, we investigated the structural, electronic, and mechanical properties of these MXenes. Our findings reveal that non-ideal termination coverage (x < 2) is more favorable for MXenes terminated with a larger size of T, such as Ti2CBrx, Nb2CClx, and Ta2CClx, and leads to mixed termination sites and lower binding energies. A reduced binding energy may facilitate delamination into single sheets, however, too low termination coverage may also cause structural collapse. Electronic properties showed an increased number of states at the Fermi level under non-ideal coverage, potentially enhancing the conductivity. Mechanically, we find the moduli of MXenes to be comparable to other 2D materials, such as transition metal chalcogenides and hexagonal boron nitride, indicating their suitability for applications requiring flexibility and durability. This study underscores the potential of tailoring MXene properties through precise control of termination coverage and composition, paving the way for enhanced application-specific performance.","PeriodicalId":19227,"journal":{"name":"npj 2D Materials and Applications","volume":" ","pages":"1-13"},"PeriodicalIF":9.1,"publicationDate":"2024-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41699-024-00502-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142377213","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-30DOI: 10.1038/s41699-024-00499-0
R. Roemer, D. H. D. Lee, S. Smit, X. Zhang, S. Godin, V. Hamza, T. Jian, J. Larkin, H. Shin, C. Liu, M. Michiardi, G. Levy, Z. Zhang, R. J. Green, C. Kim, D. Muller, A. Damascelli, M. J. Han, K. Zou
Two-dimensional (2D) van der Waals (vdW) magnets have sparked widespread attention due to their potential in spintronic applications as well as in fundamental physics. Ferromagnetic vdW compound Fe3GeTe2 (FGT) and its Ga variants have garnered significant interest due to their itinerant magnetism, correlated states, and high magnetic transition temperature. Experimental studies have demonstrated the tunability of FGT’s Curie temperature, TC, through adjustments in quintuple layer numbers (QL) and carrier concentrations, n. However, the underlying mechanism remains elusive. In this study, we employ molecular beam epitaxy (MBE) to synthesize 2D FGT films down to 1 QL with precise layer control, facilitating an exploration of the band structure and the evolution of itinerant carrier density. Angle-resolved photoemission spectroscopy (ARPES) reveals significant band structure changes at the ultra-thin limit, while first-principles calculations elucidate the band evolution from 1 QL to bulk, largely governed by interlayer coupling. Additionally, we find that n is intrinsically linked to the number of QL and temperature, with a critical value triggering the magnetic phase transition. Our findings underscore the pivotal role of band structure and itinerant electrons in governing magnetic phase transitions in such 2D vdW magnetic materials.
{"title":"Unraveling the electronic structure and magnetic transition evolution across monolayer, bilayer, and multilayer ferromagnetic Fe3GeTe2","authors":"R. Roemer, D. H. D. Lee, S. Smit, X. Zhang, S. Godin, V. Hamza, T. Jian, J. Larkin, H. Shin, C. Liu, M. Michiardi, G. Levy, Z. Zhang, R. J. Green, C. Kim, D. Muller, A. Damascelli, M. J. Han, K. Zou","doi":"10.1038/s41699-024-00499-0","DOIUrl":"10.1038/s41699-024-00499-0","url":null,"abstract":"Two-dimensional (2D) van der Waals (vdW) magnets have sparked widespread attention due to their potential in spintronic applications as well as in fundamental physics. Ferromagnetic vdW compound Fe3GeTe2 (FGT) and its Ga variants have garnered significant interest due to their itinerant magnetism, correlated states, and high magnetic transition temperature. Experimental studies have demonstrated the tunability of FGT’s Curie temperature, TC, through adjustments in quintuple layer numbers (QL) and carrier concentrations, n. However, the underlying mechanism remains elusive. In this study, we employ molecular beam epitaxy (MBE) to synthesize 2D FGT films down to 1 QL with precise layer control, facilitating an exploration of the band structure and the evolution of itinerant carrier density. Angle-resolved photoemission spectroscopy (ARPES) reveals significant band structure changes at the ultra-thin limit, while first-principles calculations elucidate the band evolution from 1 QL to bulk, largely governed by interlayer coupling. Additionally, we find that n is intrinsically linked to the number of QL and temperature, with a critical value triggering the magnetic phase transition. Our findings underscore the pivotal role of band structure and itinerant electrons in governing magnetic phase transitions in such 2D vdW magnetic materials.","PeriodicalId":19227,"journal":{"name":"npj 2D Materials and Applications","volume":" ","pages":"1-8"},"PeriodicalIF":9.1,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41699-024-00499-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142377215","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Titanium diselenide (TiSe2) is a layered material that under a critical temperature of Tc ≈ 200 K features a periodic modulation of the electron density, known as charge density wave (CDW), which finds applications in quantum information and emerging electronic devices. Here, we present first-principles calculations showing the suppression of the CDW via photoexcitation and consequent stabilization of the undistorted high-temperature phase, in agreement with experimental observations. Interestingly, the unfolded CDW melting is accompanied by a sizable reduction in the thermal conductivity, κ, of up to 25% and a large entropy increase of ~10 J K−1 kg−1. The significant κ variation is almost entirely originated from photoinduced changes in the phonon–phonon scattering processes involving a high-symmetry soft phonon mode. Our results open new possibilities in the design of devices for thermal management and phonon-based logic, and suggest original applications in the of context solid-state cooling.
{"title":"Phonon transport manipulation in TiSe2 via reversible charge density wave melting","authors":"Martí Raya-Moreno, Claudio Cazorla, Enric Canadell, Riccardo Rurali","doi":"10.1038/s41699-024-00501-9","DOIUrl":"10.1038/s41699-024-00501-9","url":null,"abstract":"Titanium diselenide (TiSe2) is a layered material that under a critical temperature of Tc ≈ 200 K features a periodic modulation of the electron density, known as charge density wave (CDW), which finds applications in quantum information and emerging electronic devices. Here, we present first-principles calculations showing the suppression of the CDW via photoexcitation and consequent stabilization of the undistorted high-temperature phase, in agreement with experimental observations. Interestingly, the unfolded CDW melting is accompanied by a sizable reduction in the thermal conductivity, κ, of up to 25% and a large entropy increase of ~10 J K−1 kg−1. The significant κ variation is almost entirely originated from photoinduced changes in the phonon–phonon scattering processes involving a high-symmetry soft phonon mode. Our results open new possibilities in the design of devices for thermal management and phonon-based logic, and suggest original applications in the of context solid-state cooling.","PeriodicalId":19227,"journal":{"name":"npj 2D Materials and Applications","volume":" ","pages":"1-9"},"PeriodicalIF":9.1,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41699-024-00501-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142377214","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-16DOI: 10.1038/s41699-024-00498-1
Yuanyuan Cui, Tingjun Wang, Deng Hu, Zhiwei Wang, Jiawang Hong, Xueyun Wang
2-dimensional (2D) piezoelectric materials have gained significant attention due to their potential applications in flexible energy harvesting and storage devices. Recently, niobium oxide dihalides NbOI2 stands out as a multifunctional anisotropic semiconductor family with an exceptionally high lateral piezoelectric constant (~21.8 pm/V), making it a promising candidate for energy conversion applications. Here we report the experimental observation of anisotropic in-plane piezoelectricity in multilayer NbOI2. Current-voltage relationships reveal a significant piezotronic effect in two typical crystalline orientations. Additionally, cyclic tensile and release experiments demonstrate an intrinsic current output of up to 140 pA when subjected to a tensile strain of 0.51%. A flexible piezoelectric nanogenerator prototype is demonstrated on the human finger and wrist, which opens up new avenues for the development of wearable electronic devices and provides valuable insights for further exploration in this field.
{"title":"Piezoelectricity in NbOI2 for piezotronics and nanogenerators","authors":"Yuanyuan Cui, Tingjun Wang, Deng Hu, Zhiwei Wang, Jiawang Hong, Xueyun Wang","doi":"10.1038/s41699-024-00498-1","DOIUrl":"10.1038/s41699-024-00498-1","url":null,"abstract":"2-dimensional (2D) piezoelectric materials have gained significant attention due to their potential applications in flexible energy harvesting and storage devices. Recently, niobium oxide dihalides NbOI2 stands out as a multifunctional anisotropic semiconductor family with an exceptionally high lateral piezoelectric constant (~21.8 pm/V), making it a promising candidate for energy conversion applications. Here we report the experimental observation of anisotropic in-plane piezoelectricity in multilayer NbOI2. Current-voltage relationships reveal a significant piezotronic effect in two typical crystalline orientations. Additionally, cyclic tensile and release experiments demonstrate an intrinsic current output of up to 140 pA when subjected to a tensile strain of 0.51%. A flexible piezoelectric nanogenerator prototype is demonstrated on the human finger and wrist, which opens up new avenues for the development of wearable electronic devices and provides valuable insights for further exploration in this field.","PeriodicalId":19227,"journal":{"name":"npj 2D Materials and Applications","volume":" ","pages":"1-6"},"PeriodicalIF":9.1,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41699-024-00498-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142236065","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-12DOI: 10.1038/s41699-024-00488-3
Borna Pielić, Matko Mužević, Dino Novko, Jiaqi Cai, Alice Bremerich, Robin Ohmann, Marko Kralj, Iva Šrut Rakić, Carsten Busse
Controlling many-body interactions in two-dimensional systems remains a formidable task from the perspective of both fundamental physics and application. Here, we explore remarkable electronic structure alterations of MoS2 monolayer islands on graphene on Ir(111) induced by non-invasive self-intercalation. This introduces significant differences in morphology and strain of MoS2 as a result of the modified interaction with the substrate. Consequently, considerable changes of the band gap and non-rigid electronic shifts of valleys are detected, which are a combined effect of the screening of the many-body interactions and strain in MoS2. Furthermore, theory shows that each substrate leaves a unique stamp on the electronic structure of two-dimensional material in terms of those two parameters, restricted by their correlation.
{"title":"Probing the interplay of interactions, screening and strain in monolayer MoS2 via self-intercalation","authors":"Borna Pielić, Matko Mužević, Dino Novko, Jiaqi Cai, Alice Bremerich, Robin Ohmann, Marko Kralj, Iva Šrut Rakić, Carsten Busse","doi":"10.1038/s41699-024-00488-3","DOIUrl":"10.1038/s41699-024-00488-3","url":null,"abstract":"Controlling many-body interactions in two-dimensional systems remains a formidable task from the perspective of both fundamental physics and application. Here, we explore remarkable electronic structure alterations of MoS2 monolayer islands on graphene on Ir(111) induced by non-invasive self-intercalation. This introduces significant differences in morphology and strain of MoS2 as a result of the modified interaction with the substrate. Consequently, considerable changes of the band gap and non-rigid electronic shifts of valleys are detected, which are a combined effect of the screening of the many-body interactions and strain in MoS2. Furthermore, theory shows that each substrate leaves a unique stamp on the electronic structure of two-dimensional material in terms of those two parameters, restricted by their correlation.","PeriodicalId":19227,"journal":{"name":"npj 2D Materials and Applications","volume":" ","pages":"1-7"},"PeriodicalIF":9.1,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41699-024-00488-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142174404","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-11DOI: 10.1038/s41699-024-00497-2
Athanasios Paralikis, Claudia Piccinini, Abdulmalik A. Madigawa, Pietro Metuh, Luca Vannucci, Niels Gregersen, Battulga Munkhbat
Quantum emitters in transition metal dichalcogenides (TMDs) have recently emerged as a promising platform for generating single photons for optical quantum information processing. In this work, we present an approach for deterministically controlling the polarization of fabricated quantum emitters in a tungsten diselenide (WSe2) monolayer. We employ novel nanopillar geometries with long and sharp tips to induce a controlled directional strain in the monolayer, and we report on fabricated WSe2 emitters producing single photons with a high degree of polarization (99 ± 4%) and high purity (g(2)(0) = 0.030 ± 0.025). Our work paves the way for the deterministic integration of TMD-based quantum emitters for future photonic quantum technologies.
{"title":"Tailoring polarization in WSe2 quantum emitters through deterministic strain engineering","authors":"Athanasios Paralikis, Claudia Piccinini, Abdulmalik A. Madigawa, Pietro Metuh, Luca Vannucci, Niels Gregersen, Battulga Munkhbat","doi":"10.1038/s41699-024-00497-2","DOIUrl":"10.1038/s41699-024-00497-2","url":null,"abstract":"Quantum emitters in transition metal dichalcogenides (TMDs) have recently emerged as a promising platform for generating single photons for optical quantum information processing. In this work, we present an approach for deterministically controlling the polarization of fabricated quantum emitters in a tungsten diselenide (WSe2) monolayer. We employ novel nanopillar geometries with long and sharp tips to induce a controlled directional strain in the monolayer, and we report on fabricated WSe2 emitters producing single photons with a high degree of polarization (99 ± 4%) and high purity (g(2)(0) = 0.030 ± 0.025). Our work paves the way for the deterministic integration of TMD-based quantum emitters for future photonic quantum technologies.","PeriodicalId":19227,"journal":{"name":"npj 2D Materials and Applications","volume":" ","pages":"1-8"},"PeriodicalIF":9.1,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41699-024-00497-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142174379","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-11DOI: 10.1038/s41699-024-00495-4
Nan Wu, Xiangchen Hu, Yinliang Tang, Congcong Wu, Yu Chen, Yiyuan Ren, Zhuo Zhang, Yi Yu, Hung-Ta Wang
Layered bismuth (Bi) has been focused on two Peierls distortion derivatives, i.e., bulk stable β-phase (A7 phase), black phosphorus-like α-phase (A17 phase), and their mutated structures. Metastable structures beyond Peierls distortion system are yet rarely accessible. Here, Bi in square symmetry ( $${C}_{4v}$$ ), called s-Bi, was grown via physical vapor deposition. The co-existence of three 120°-associated s-Bi crystal grains was analyzed using transmission electron microscopy. 120°-oriented one-dimensional (1D) nuclei indicate s-Bi heteroepitaxy on six-fold symmetric ( $${C}_{6v}$$ ) mica (001). A subsequent nanorod-like nuclei coalescing could promote a morphology evolution, resulting in triangular or hexagonal nanosheets with the unique triple s-Bi structure suitable for later β-Bi growth. Lattice misfit and strain calculations suggest a supercell match between $$4times 7$$ s-Bi and $$3times 3$$ mica (001). This work demonstrates the metastable s-Bi structure via anisotropic heteroepitaxy of $${C}_{4v}$$ s-Bi on $${C}_{6v}$$ mica.
{"title":"Metastable square Bismuth allotrope oriented by six-fold symmetric mica","authors":"Nan Wu, Xiangchen Hu, Yinliang Tang, Congcong Wu, Yu Chen, Yiyuan Ren, Zhuo Zhang, Yi Yu, Hung-Ta Wang","doi":"10.1038/s41699-024-00495-4","DOIUrl":"10.1038/s41699-024-00495-4","url":null,"abstract":"Layered bismuth (Bi) has been focused on two Peierls distortion derivatives, i.e., bulk stable β-phase (A7 phase), black phosphorus-like α-phase (A17 phase), and their mutated structures. Metastable structures beyond Peierls distortion system are yet rarely accessible. Here, Bi in square symmetry ( $${C}_{4v}$$ ), called s-Bi, was grown via physical vapor deposition. The co-existence of three 120°-associated s-Bi crystal grains was analyzed using transmission electron microscopy. 120°-oriented one-dimensional (1D) nuclei indicate s-Bi heteroepitaxy on six-fold symmetric ( $${C}_{6v}$$ ) mica (001). A subsequent nanorod-like nuclei coalescing could promote a morphology evolution, resulting in triangular or hexagonal nanosheets with the unique triple s-Bi structure suitable for later β-Bi growth. Lattice misfit and strain calculations suggest a supercell match between $$4times 7$$ s-Bi and $$3times 3$$ mica (001). This work demonstrates the metastable s-Bi structure via anisotropic heteroepitaxy of $${C}_{4v}$$ s-Bi on $${C}_{6v}$$ mica.","PeriodicalId":19227,"journal":{"name":"npj 2D Materials and Applications","volume":" ","pages":"1-9"},"PeriodicalIF":9.1,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41699-024-00495-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142174416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-04DOI: 10.1038/s41699-024-00496-3
Elena-Antonella Bittner, Konrad Merkel, Frank Ortmann
The electrostatic potential within porous materials critically influences applications like gas storage, catalysis, sensors and semiconductor technology. Precise control of this potential in covalent organic frameworks (COFs) is essential for optimizing these applications. We propose a straightforward method to achieve this by employing electric quadrupolar building blocks. Our comprehensive models accurately reproduce the electrostatic potential in 2D-COFs, requiring only a few parameters that depend solely on local electrostatic properties, independent of the COF’s lattice structure and topology. This approach has been validated across various systems, including conjugated and non-conjugated building blocks with different symmetries. We explore single-layer, few-layer, and bulk systems, achieving changes in the potential which exceed one electronvolt. Stacking configurations such as eclipsed AA, serrated AA’, and inclined stacking all exhibit the tuning effect with minor variations. Finally, we discuss the impact of these potential manipulations on applications like ion and gas uptake.
{"title":"Engineering the electrostatic potential in a COF''s pore by selecting quadrupolar building blocks and linkages","authors":"Elena-Antonella Bittner, Konrad Merkel, Frank Ortmann","doi":"10.1038/s41699-024-00496-3","DOIUrl":"10.1038/s41699-024-00496-3","url":null,"abstract":"The electrostatic potential within porous materials critically influences applications like gas storage, catalysis, sensors and semiconductor technology. Precise control of this potential in covalent organic frameworks (COFs) is essential for optimizing these applications. We propose a straightforward method to achieve this by employing electric quadrupolar building blocks. Our comprehensive models accurately reproduce the electrostatic potential in 2D-COFs, requiring only a few parameters that depend solely on local electrostatic properties, independent of the COF’s lattice structure and topology. This approach has been validated across various systems, including conjugated and non-conjugated building blocks with different symmetries. We explore single-layer, few-layer, and bulk systems, achieving changes in the potential which exceed one electronvolt. Stacking configurations such as eclipsed AA, serrated AA’, and inclined stacking all exhibit the tuning effect with minor variations. Finally, we discuss the impact of these potential manipulations on applications like ion and gas uptake.","PeriodicalId":19227,"journal":{"name":"npj 2D Materials and Applications","volume":" ","pages":"1-9"},"PeriodicalIF":9.1,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41699-024-00496-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142174403","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The discovery of van der Waals intrinsic magnets has expanded the possibilities of realizing spintronics devices. We investigate the transmission, tunneling magnetoresistance ratio, and spin injection efficiency of bilayer LaI2 using a combination of first-principles calculations and the non-equilibrium Green’s function method. Multilayer graphene electrodes are employed to build a magnetic tunnel junction with bilayer LaI2 as ferromagnetic barrier. The magnetic tunnel junction turns out to be a perfect spin filter device with an outstanding tunneling magnetoresistance ratio of 653% under a bias of 0.1 V and a still excellent performance in a wide bias range. In combination with the obtained high spin injection efficiency this opens up great potential from the application point of view.
范德华本征磁体的发现拓展了实现自旋电子器件的可能性。我们结合第一原理计算和非平衡格林函数法，研究了双层 LaI2 的传输、隧道磁阻比和自旋注入效率。利用多层石墨烯电极构建了以双层 LaI2 为铁磁屏障的磁隧道结。该磁隧道结被证明是一个完美的自旋过滤器件，在 0.1 V 的偏压下具有 653% 的出色隧道磁阻比，并且在宽偏压范围内仍具有出色的性能。结合所获得的高自旋注入效率，从应用角度来看，它具有巨大的潜力。
{"title":"Magnetic tunnel junction based on bilayer LaI2 as perfect spin filter device","authors":"Shubham Tyagi, Avijeet Ray, Nirpendra Singh, Udo Schwingenschlögl","doi":"10.1038/s41699-024-00493-6","DOIUrl":"10.1038/s41699-024-00493-6","url":null,"abstract":"The discovery of van der Waals intrinsic magnets has expanded the possibilities of realizing spintronics devices. We investigate the transmission, tunneling magnetoresistance ratio, and spin injection efficiency of bilayer LaI2 using a combination of first-principles calculations and the non-equilibrium Green’s function method. Multilayer graphene electrodes are employed to build a magnetic tunnel junction with bilayer LaI2 as ferromagnetic barrier. The magnetic tunnel junction turns out to be a perfect spin filter device with an outstanding tunneling magnetoresistance ratio of 653% under a bias of 0.1 V and a still excellent performance in a wide bias range. In combination with the obtained high spin injection efficiency this opens up great potential from the application point of view.","PeriodicalId":19227,"journal":{"name":"npj 2D Materials and Applications","volume":" ","pages":"1-7"},"PeriodicalIF":9.1,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41699-024-00493-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142117969","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-30DOI: 10.1038/s41699-024-00494-5
Ravi Yadav, Lei Xu, Michele Pizzochero, Jeroen van den Brink, Mikhail I. Katsnelson, Oleg V. Yazyev
Although chromium trihalides are widely regarded as a promising class of two-dimensional magnets for next-generation devices, an accurate description of their electronic structure and magnetic interactions has proven challenging to achieve. Here, we quantify electronic excitations and spin interactions in CrX3 (X = Cl, Br, I) using embedded many-body wavefunction calculations and fully generalized spin Hamiltonians. We find that the three trihalides feature comparable d-shell excitations, consisting of a high-spin 4A2 $$({t}_{2g}^{3}{e}_{g}^{0})$$ ground state lying 1.5–1.7 eV below the first excited state 4T2 ( $${t}_{2g}^{2}{e}_{g}^{1}$$ ). CrCl3 exhibits a single-ion anisotropy Asia = − 0.02 meV, while the Cr spin-3/2 moments are ferromagnetically coupled through bilinear and biquadratic exchange interactions of J1 = − 0.97 meV and J2 = − 0.05 meV, respectively. The corresponding values for CrBr3 and CrI3 increase to Asia = −0.08 meV and Asia= − 0.12 meV for the single-ion anisotropy, J1 = −1.21 meV, J2 = −0.05 meV and J1 = −1.38 meV, J2 = −0.06 meV for the exchange couplings, respectively. We find that the overall magnetic anisotropy is defined by the interplay between Asia and Adip due to magnetic dipole–dipole interaction that favors in-plane orientation of magnetic moments in ferromagnetic monolayers and bulk layered magnets. The competition between the two contributions sets CrCl3 and CrI3 as the easy-plane (Asia + Adip >0) and easy-axis (Asia + Adip <0) ferromagnets, respectively. The differences between the magnets trace back to the atomic radii of the halogen ligands and the magnitude of spin–orbit coupling. Our findings are in excellent agreement with recent experiments, thus providing reference values for the fundamental interactions in chromium trihalides.
{"title":"Electronic excitations and spin interactions in chromium trihalides from embedded many-body wavefunctions","authors":"Ravi Yadav, Lei Xu, Michele Pizzochero, Jeroen van den Brink, Mikhail I. Katsnelson, Oleg V. Yazyev","doi":"10.1038/s41699-024-00494-5","DOIUrl":"10.1038/s41699-024-00494-5","url":null,"abstract":"Although chromium trihalides are widely regarded as a promising class of two-dimensional magnets for next-generation devices, an accurate description of their electronic structure and magnetic interactions has proven challenging to achieve. Here, we quantify electronic excitations and spin interactions in CrX3 (X = Cl, Br, I) using embedded many-body wavefunction calculations and fully generalized spin Hamiltonians. We find that the three trihalides feature comparable d-shell excitations, consisting of a high-spin 4A2 $$({t}_{2g}^{3}{e}_{g}^{0})$$ ground state lying 1.5–1.7 eV below the first excited state 4T2 ( $${t}_{2g}^{2}{e}_{g}^{1}$$ ). CrCl3 exhibits a single-ion anisotropy Asia = − 0.02 meV, while the Cr spin-3/2 moments are ferromagnetically coupled through bilinear and biquadratic exchange interactions of J1 = − 0.97 meV and J2 = − 0.05 meV, respectively. The corresponding values for CrBr3 and CrI3 increase to Asia = −0.08 meV and Asia= − 0.12 meV for the single-ion anisotropy, J1 = −1.21 meV, J2 = −0.05 meV and J1 = −1.38 meV, J2 = −0.06 meV for the exchange couplings, respectively. We find that the overall magnetic anisotropy is defined by the interplay between Asia and Adip due to magnetic dipole–dipole interaction that favors in-plane orientation of magnetic moments in ferromagnetic monolayers and bulk layered magnets. The competition between the two contributions sets CrCl3 and CrI3 as the easy-plane (Asia + Adip >0) and easy-axis (Asia + Adip <0) ferromagnets, respectively. The differences between the magnets trace back to the atomic radii of the halogen ligands and the magnitude of spin–orbit coupling. Our findings are in excellent agreement with recent experiments, thus providing reference values for the fundamental interactions in chromium trihalides.","PeriodicalId":19227,"journal":{"name":"npj 2D Materials and Applications","volume":" ","pages":"1-8"},"PeriodicalIF":9.1,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41699-024-00494-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142091215","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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