Pub Date : 2023-11-13DOI: 10.1088/2053-1583/ad0402
Daniel Vaquero, Olga Arroyo Gascón, Juan Salvador-Sanchez, Pedro Luis L. Alcázar Ruano, Enrique Diez, Ana Perez-Rodriguez, Julián D. Correa, Francisco Dominguez-Adame, Leonor Chico, Jorge Quereda
Abstract The low crystal symmetry of rhenium disulphide (ReS 2 ) leads to the emergence of dichroic optical and optoelectronic response, absent in other layered transition metal dichalcogenides, which could be exploited for device applications requiring polarization resolution. To date, spectroscopy studies on the optical response of ReS 2 have relied almost exclusively in characterization techniques involving optical detection, such as photoluminescence, absorbance, or reflectance spectroscopy. However, to realize the full potential of this material, it is necessary to develop knowledge on its optoelectronic response with spectral resolution. In this work, we study the polarization-dependent photocurrent spectra of few-layer ReS 2 photodetectors, both in room conditions and at cryogenic temperature. Our spectral measurements reveal two main exciton lines at energies matching those reported for optical spectroscopy measurements, as well as their excited states. Moreover, we also observe an additional exciton-like spectral feature with a photoresponse intensity comparable to the two main exciton lines. We attribute this feature, not observed in earlier photoluminescence measurements, to a non-radiative exciton transition. The intensities of the three main exciton features, as well as their excited states, modulate with linear polarization of light, each one acquiring maximal strength at a different polarization angle. We have performed first-principles exciton calculations employing the Bethe-Salpeter formalism, which corroborate our experimental findings. Our results bring new perspectives for the development of ReS 2 -based nanodevices.
{"title":"Polarization-tuneable excitonic spectral features in the optoelectronic response of atomically thin ReS<sub>2</sub>.","authors":"Daniel Vaquero, Olga Arroyo Gascón, Juan Salvador-Sanchez, Pedro Luis L. Alcázar Ruano, Enrique Diez, Ana Perez-Rodriguez, Julián D. Correa, Francisco Dominguez-Adame, Leonor Chico, Jorge Quereda","doi":"10.1088/2053-1583/ad0402","DOIUrl":"https://doi.org/10.1088/2053-1583/ad0402","url":null,"abstract":"Abstract The low crystal symmetry of rhenium disulphide (ReS 2 ) leads to the emergence of dichroic optical and optoelectronic response, absent in other layered transition metal dichalcogenides, which could be exploited for device applications requiring polarization resolution. To date, spectroscopy studies on the optical response of ReS 2 have relied almost exclusively in characterization techniques involving optical detection, such as photoluminescence, absorbance, or reflectance spectroscopy. However, to realize the full potential of this material, it is necessary to develop knowledge on its optoelectronic response with spectral resolution. In this work, we study the polarization-dependent photocurrent spectra of few-layer ReS 2 photodetectors, both in room conditions and at cryogenic temperature. Our spectral measurements reveal two main exciton lines at energies matching those reported for optical spectroscopy measurements, as well as their excited states. Moreover, we also observe an additional exciton-like spectral feature with a photoresponse intensity comparable to the two main exciton lines. We attribute this feature, not observed in earlier photoluminescence measurements, to a non-radiative exciton transition. The intensities of the three main exciton features, as well as their excited states, modulate with linear polarization of light, each one acquiring maximal strength at a different polarization angle. We have performed first-principles exciton calculations employing the Bethe-Salpeter formalism, which corroborate our experimental findings. Our results bring new perspectives for the development of ReS 2 -based nanodevices.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"4 10","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134993761","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}
Pub Date : 2023-11-10DOI: 10.1088/2053-1583/ad0b87
Sreevidya Narayanan, Anoop Kamalasanan, Annu Anns Sunny, Madhu Thalakulam
Abstract The true character of physical phenomena is thought to be reinforced as the system becomes disorder-free. In contrast, the two-dimensional (2D) superconductor is predicted to turn fragile and resistive away from the limit I → 0, B → 0, in the pinning-free regime. It is intriguing to note that the very vortices responsible for achieving superconductivity by pairing, condensation, and, thereby reducing the classical dissipation, render the state resistive driven by quantum fluctuations in the T → 0. While cleaner systems are being explored for technological improvements, the 2D superconductor turning resistive when influenced by weak electric and magnetic fields has profound consequences for quantum technologies. A metallic ground state in 2D is beyond the consensus of both Bosonic and Fermionic systems, and its origin and nature warrant a comprehensive theoretical understanding supplemented by in-depth experiments. A real-time observation of the influence of vortex dynamics on transport properties so far has been elusive. We explore the nature and fate of a low-viscous, clean, 2D superconducting state formed on an ionic-liquid gated few-layered MoS 2 sample. The vortex-core being dissipative, the elastic depinning, intervortex interaction, and the subsequent dynamics of the vortex-lattice leave transient signatures in the transport characteristics. The temperature and magnetic field dependence of the transient nature and the noise characteristics of the magnetoresistance confirm that quantum fluctuations are solely responsible for the Bose metal state and the fragility of the superconducting state.
{"title":"Transient vortex dynamics and evolution of Bose metal from a 2D superconductor on MoS<sub>2</sub>","authors":"Sreevidya Narayanan, Anoop Kamalasanan, Annu Anns Sunny, Madhu Thalakulam","doi":"10.1088/2053-1583/ad0b87","DOIUrl":"https://doi.org/10.1088/2053-1583/ad0b87","url":null,"abstract":"Abstract The true character of physical phenomena is thought to be reinforced as the system becomes disorder-free. In contrast, the two-dimensional (2D) superconductor is predicted to turn fragile and resistive away from the limit I → 0, B → 0, in the pinning-free regime. It is intriguing to note that the very vortices responsible for achieving superconductivity by pairing, condensation, and, thereby reducing the classical dissipation, render the state resistive driven by quantum fluctuations in the T → 0. While cleaner systems are being explored for technological improvements, the 2D superconductor turning resistive when influenced by weak electric and magnetic fields has profound consequences for quantum technologies. A metallic ground state in 2D is beyond the consensus of both Bosonic and Fermionic systems, and its origin and nature warrant a comprehensive theoretical understanding supplemented by in-depth experiments. A real-time observation of the influence of vortex dynamics on transport properties so far has been elusive. We explore the nature and fate of a low-viscous, clean, 2D superconducting state formed on an ionic-liquid gated few-layered MoS 2 sample. The vortex-core being dissipative, the elastic depinning, intervortex interaction, and the subsequent dynamics of the vortex-lattice leave transient signatures in the transport characteristics. The temperature and magnetic field dependence of the transient nature and the noise characteristics of the magnetoresistance confirm that quantum fluctuations are solely responsible for the Bose metal state and the fragility of the superconducting state.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"86 24","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135092576","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}
Pub Date : 2023-11-10DOI: 10.1088/2053-1583/ad064a
Thomas Michely, Jason Bergelt, Affan Safeer, Alexander Bäder, Tobias Hartl, Jeison Fischer
Abstract The growth of monolayer hexagonal boron nitride (h-BN) on Ir(110) through low-pressure chemical vapor deposition is investigated using low energy electron diffraction and scanning tunneling microscopy. We find that the growth of aligned h-BN on Ir(110) requires a growth temperature of 1500 K, whereas lower growth temperatures result in coexistence of aligned h-BN with twisted h-BN. The presence of the h-BN overlayer suppresses the formation of the nano-faceted ridge pattern known from clean Ir(110). Instead, we observe the formation of a (1×n) reconstruction, with n such that the missing rows are in registry with the h-BN/Ir(110) moiré pattern. Our moiré analysis showcases a precise methodology for determining both the moiré periodicity and the h-BN lattice parameter on an fcc(110) surface. Aligned h-BN on Ir(110) is found to be slightly compressed compared to bulk h-BN, with a monolayer lattice parameter of ah−BN=(0.2489±0.0006) nm. The lattice mismatch with the substrate along 11ˉ0 gives rise to a moiré periodicity of am=2.99±0.08 nm.
{"title":"Growth of aligned and twisted hexagonal boron nitride on Ir(110)","authors":"Thomas Michely, Jason Bergelt, Affan Safeer, Alexander Bäder, Tobias Hartl, Jeison Fischer","doi":"10.1088/2053-1583/ad064a","DOIUrl":"https://doi.org/10.1088/2053-1583/ad064a","url":null,"abstract":"Abstract The growth of monolayer hexagonal boron nitride (h-BN) on Ir(110) through low-pressure chemical vapor deposition is investigated using low energy electron diffraction and scanning tunneling microscopy. We find that the growth of aligned h-BN on Ir(110) requires a growth temperature of 1500 K, whereas lower growth temperatures result in coexistence of aligned h-BN with twisted h-BN. The presence of the h-BN overlayer suppresses the formation of the nano-faceted ridge pattern known from clean Ir(110). Instead, we observe the formation of a <?CDATA $(1 times n)$?> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:mo stretchy=\"false\">(</mml:mo> <mml:mn>1</mml:mn> <mml:mo>×</mml:mo> <mml:mi>n</mml:mi> <mml:mo stretchy=\"false\">)</mml:mo> </mml:math> reconstruction, with n such that the missing rows are in registry with the h-BN/Ir(110) moiré pattern. Our moiré analysis showcases a precise methodology for determining both the moiré periodicity and the h-BN lattice parameter on an fcc(110) surface. Aligned h-BN on Ir(110) is found to be slightly compressed compared to bulk h-BN, with a monolayer lattice parameter of <?CDATA $a_{mathrm{h-BN}} = (0.2489 pm 0.0006)$?> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:msub> <mml:mi>a</mml:mi> <mml:mrow> <mml:mrow> <mml:mi mathvariant=\"normal\">h</mml:mi> <mml:mo>−</mml:mo> <mml:mi mathvariant=\"normal\">B</mml:mi> <mml:mi mathvariant=\"normal\">N</mml:mi> </mml:mrow> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mo stretchy=\"false\">(</mml:mo> <mml:mn>0.2489</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.0006</mml:mn> <mml:mo stretchy=\"false\">)</mml:mo> </mml:math> nm. The lattice mismatch with the substrate along <?CDATA $left[ 1 bar{1} 0 right]$?> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:mfenced close=\"]\" open=\"[\"> <mml:mrow> <mml:mn>1</mml:mn> <mml:mover> <mml:mn>1</mml:mn> <mml:mo>ˉ</mml:mo> </mml:mover> <mml:mn>0</mml:mn> </mml:mrow> </mml:mfenced> </mml:math> gives rise to a moiré periodicity of <?CDATA $a_{mathrm{m}} = 2.99 pm 0.08$?> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:msub> <mml:mi>a</mml:mi> <mml:mrow> <mml:mrow> <mml:mi mathvariant=\"normal\">m</mml:mi> </mml:mrow> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>2.99</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.08</mml:mn> </mml:math> nm.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"71 24","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135088048","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}
Pub Date : 2023-11-03DOI: 10.1088/2053-1583/ad047e
Martina Corso, Jorge Lobo-Checa, Andrew Weber, Ignacio Piquero-Zulaica, Zakaria Mohammed Abd El-Fattah, Patrick Le Fèvre, J. Enrique Ortega, Eugene Krasovskii
Abstract Photon-energy dependence of photoemission from seven-atoms-wide armchair graphene nanoribbons (GNRs) is studied experimentally and theoretically up to ℏω=95 eV. A strong photon energy dependence of the normal emission from the valence band maximum (VB 1 ) is observed, sharply peaked at ℏω=12 eV. The detailed analysis of the light-polarization dependence of the photoemission from VB 1 unambiguously characterizes the symmetry of the state. The experimental observations are analyzed based on ab initio one-step theory of photoemission. Off-normal emission is studied in detail and its relation to the standing-wave character of the valence band states is discussed. Excellent agreement with the earlier experiment (Senkovskiy et al 2018 2D Mater. 5 035007) is obtained. Rapid variations of the intensity with the ribbon-transverse photoelectron momentum are predicted from the ab initio theory, which are at variance with the prediction of the tight-binding rigid-wall model. These findings can help interpret angle-resolved photoemission measurements of similar systems. Moreover, the strong enhancement of the photoyield could trigger the GNR application as narrow-band photodetectors and contribute to the design of novel photocathodes for vacuum ultraviolet photodetection.
摘要从理论上和实验上研究了7原子宽扶手型石墨烯纳米带(GNRs)的光能依赖关系。从价带最大值(vb1)观察到一个强的光子能量依赖性，在1 ω = 12 eV处达到尖峰。详细分析了VB 1光发射的光偏振依赖性，明确地表征了状态的对称性。基于从头算一步光发射理论对实验结果进行了分析。详细研究了非正常发射，并讨论了非正常发射与价带态驻波特性的关系。与早期实验(Senkovskiy et al . 2018 2D Mater. 5 035007)非常吻合。从从头算理论中预测了光电子强度随光电子横向动量的快速变化，这与紧结合刚壁模型的预测不同。这些发现有助于解释类似系统的角度分辨光发射测量。此外，光产率的显著提高可以触发GNR作为窄带光电探测器的应用，并有助于设计用于真空紫外光探测的新型光电阴极。
{"title":"Enhanced vacuum ultraviolet photoemission from graphene nanoribbons","authors":"Martina Corso, Jorge Lobo-Checa, Andrew Weber, Ignacio Piquero-Zulaica, Zakaria Mohammed Abd El-Fattah, Patrick Le Fèvre, J. Enrique Ortega, Eugene Krasovskii","doi":"10.1088/2053-1583/ad047e","DOIUrl":"https://doi.org/10.1088/2053-1583/ad047e","url":null,"abstract":"Abstract Photon-energy dependence of photoemission from seven-atoms-wide armchair graphene nanoribbons (GNRs) is studied experimentally and theoretically up to <?CDATA $hbaromega = 95$?> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:mi>ℏ</mml:mi> <mml:mi>ω</mml:mi> <mml:mo>=</mml:mo> <mml:mn>95</mml:mn> </mml:math> eV. A strong photon energy dependence of the normal emission from the valence band maximum (VB 1 ) is observed, sharply peaked at <?CDATA $hbaromega = 12$?> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:mi>ℏ</mml:mi> <mml:mi>ω</mml:mi> <mml:mo>=</mml:mo> <mml:mn>12</mml:mn> </mml:math> eV. The detailed analysis of the light-polarization dependence of the photoemission from VB 1 unambiguously characterizes the symmetry of the state. The experimental observations are analyzed based on ab initio one-step theory of photoemission. Off-normal emission is studied in detail and its relation to the standing-wave character of the valence band states is discussed. Excellent agreement with the earlier experiment (Senkovskiy et al 2018 2D Mater. 5 035007) is obtained. Rapid variations of the intensity with the ribbon-transverse photoelectron momentum are predicted from the ab initio theory, which are at variance with the prediction of the tight-binding rigid-wall model. These findings can help interpret angle-resolved photoemission measurements of similar systems. Moreover, the strong enhancement of the photoyield could trigger the GNR application as narrow-band photodetectors and contribute to the design of novel photocathodes for vacuum ultraviolet photodetection.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"173 S395","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135775143","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}
Pub Date : 2023-11-03DOI: 10.1088/2053-1583/ad015f
Jingyi Zou, Sen Lin, Tianyi Huang, Hefei Liu, Yushuang Liu, Yibai Zhong, Yuxuan Cosmi Lin, Han Wang, Sheng Shen, Min Xu, Xu Zhang
Abstract Synaptic devices with tunable weight hold great promise in enabling non-von Neumann architecture for energy efficient computing. However, conventional metal-insulator-metal based two-terminal memristors share the same physical channel for both programming and reading, therefore the programming power consumption is dependent on the synaptic resistance states and can be particularly high when the memristor is in the low resistance states. Three terminal synaptic transistors, on the other hand, allow synchronous programming and reading and have been shown to possess excellent reliability. Here we present a binary oxide based three-terminal MoS 2 synaptic device, in which the channel conductance can be modulated by interfacial charges generated at the oxide interface driven by Maxwell-Wagner instability. The binary oxide stack serves both as an interfacial charge host and gate dielectrics. Both excitatory and inhibitory behaviors are experimentally realized, and the presynaptic potential polarity can be effectively controlled by engineering the oxide stacking sequence, which is a unique feature compared with existing charge-trap based synaptic devices and provides a new tuning knob for controlling synaptic device characteristics. By adopting a three-terminal transistor structure, the programming channel and reading channel are physically separated and the programming power consumption can be kept constantly low (∼50 pW) across a wide dynamic range of 10 5 . This work demonstrates a complementary metal oxide semiconductor compatible approach to build power efficient synaptic devices for artificial intelligence applications.
{"title":"Power efficient MoS2 synaptic devices based on maxwell-wagner interfacial charging in binary oxides","authors":"Jingyi Zou, Sen Lin, Tianyi Huang, Hefei Liu, Yushuang Liu, Yibai Zhong, Yuxuan Cosmi Lin, Han Wang, Sheng Shen, Min Xu, Xu Zhang","doi":"10.1088/2053-1583/ad015f","DOIUrl":"https://doi.org/10.1088/2053-1583/ad015f","url":null,"abstract":"Abstract Synaptic devices with tunable weight hold great promise in enabling non-von Neumann architecture for energy efficient computing. However, conventional metal-insulator-metal based two-terminal memristors share the same physical channel for both programming and reading, therefore the programming power consumption is dependent on the synaptic resistance states and can be particularly high when the memristor is in the low resistance states. Three terminal synaptic transistors, on the other hand, allow synchronous programming and reading and have been shown to possess excellent reliability. Here we present a binary oxide based three-terminal MoS 2 synaptic device, in which the channel conductance can be modulated by interfacial charges generated at the oxide interface driven by Maxwell-Wagner instability. The binary oxide stack serves both as an interfacial charge host and gate dielectrics. Both excitatory and inhibitory behaviors are experimentally realized, and the presynaptic potential polarity can be effectively controlled by engineering the oxide stacking sequence, which is a unique feature compared with existing charge-trap based synaptic devices and provides a new tuning knob for controlling synaptic device characteristics. By adopting a three-terminal transistor structure, the programming channel and reading channel are physically separated and the programming power consumption can be kept constantly low (∼50 pW) across a wide dynamic range of 10 5 . This work demonstrates a complementary metal oxide semiconductor compatible approach to build power efficient synaptic devices for artificial intelligence applications.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"178 S433","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135775277","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}
Pub Date : 2023-10-27DOI: 10.1088/2053-1583/ad0403
C. Li, Wang Yao
Abstract In stacks of transition metal dichalcogenide monolayers with arbitrary twisting angles, we explore a new class of bright excitons arising from the pronounced Förster coupling, whose dimensionality is tuned by its in-plane momentum. The low energy sector at small momenta is two-dimensional, featuring a Mexican Hat dispersion, while the high energy sector at larger momenta becomes three-dimensional (3D) with sizable group velocity both in-plane and out-of-plane. By choices of the spacer thickness, versatile surface or interface exciton modes localized at designated layers can emerge out of the cross-dimensional bulk dispersion for a topological origin, which can be mapped to the Su–Schrieffer–Heeger soliton. Moreover, step-edges in spacers can be exploited for engineering lateral interfaces to enable interlayer communication of the topological interface exciton. Combined with the polarization selection rule inherited from the monolayer building block, these exotic exciton properties open up new opportunities for multilayer design towards 3D integration of valley exciton optoelectronics.
{"title":"Cross-dimensional valley excitons from Förster coupling in arbitrarily twisted stacks of monolayer semiconductors","authors":"C. Li, Wang Yao","doi":"10.1088/2053-1583/ad0403","DOIUrl":"https://doi.org/10.1088/2053-1583/ad0403","url":null,"abstract":"Abstract In stacks of transition metal dichalcogenide monolayers with arbitrary twisting angles, we explore a new class of bright excitons arising from the pronounced Förster coupling, whose dimensionality is tuned by its in-plane momentum. The low energy sector at small momenta is two-dimensional, featuring a Mexican Hat dispersion, while the high energy sector at larger momenta becomes three-dimensional (3D) with sizable group velocity both in-plane and out-of-plane. By choices of the spacer thickness, versatile surface or interface exciton modes localized at designated layers can emerge out of the cross-dimensional bulk dispersion for a topological origin, which can be mapped to the Su–Schrieffer–Heeger soliton. Moreover, step-edges in spacers can be exploited for engineering lateral interfaces to enable interlayer communication of the topological interface exciton. Combined with the polarization selection rule inherited from the monolayer building block, these exotic exciton properties open up new opportunities for multilayer design towards 3D integration of valley exciton optoelectronics.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"51 11","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136233551","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}
Pub Date : 2023-10-19DOI: 10.1088/2053-1583/ad00ca
Francis Davies, Kai Mehlich, Carsten Busse, Arkady V. Krasheninnikov
Abstract The development of lateral heterostructures (LHs) based on two-dimensional (2D) materials with similar atomic structure but distinct electronic properties, such as transition metal dichalcogenides (TMDCs), opened a new route towards realisation of optoelectronic devices with unique characteristics. In contrast to van der Waals vertical heterostructures, the covalent bonding at the interface between subsystems in LHs is strong, such that the morphology of the interface, which can be coherent or contain dislocations, strongly affects the properties of the LH. We predict the atomic structure of the interface with account for the mismatch between the primitive cell sizes of the components, and more important, the widths of the joined materials using parameters derived from first-principles calculations. We apply this approach to a variety of TMDCs and set a theoretical limit on when the transition of the interface from coherent to dislocation-type should occur. We validate our theoretical results by comparison with the initial stage of two-dimensional heteropitaxial growth of junctions between MoS 2 and TaS 2 on Au(111).
{"title":"What governs the atomic structure of the interface between 2D transition metal dichalcogenides in lateral heterostructures?","authors":"Francis Davies, Kai Mehlich, Carsten Busse, Arkady V. Krasheninnikov","doi":"10.1088/2053-1583/ad00ca","DOIUrl":"https://doi.org/10.1088/2053-1583/ad00ca","url":null,"abstract":"Abstract The development of lateral heterostructures (LHs) based on two-dimensional (2D) materials with similar atomic structure but distinct electronic properties, such as transition metal dichalcogenides (TMDCs), opened a new route towards realisation of optoelectronic devices with unique characteristics. In contrast to van der Waals vertical heterostructures, the covalent bonding at the interface between subsystems in LHs is strong, such that the morphology of the interface, which can be coherent or contain dislocations, strongly affects the properties of the LH. We predict the atomic structure of the interface with account for the mismatch between the primitive cell sizes of the components, and more important, the widths of the joined materials using parameters derived from first-principles calculations. We apply this approach to a variety of TMDCs and set a theoretical limit on when the transition of the interface from coherent to dislocation-type should occur. We validate our theoretical results by comparison with the initial stage of two-dimensional heteropitaxial growth of junctions between MoS 2 and TaS 2 on Au(111).","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"67 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135667703","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}
Pub Date : 2023-10-18DOI: 10.1088/2053-1583/ad01c8
Linqing Zhang, Minjun Lei, zhiliang jin
Abstract As is well known, how to deeply understand the charge separation and charge transfer capabilities of catalysts, as well as how to optimize these capabilities of catalysts to improve hydrogen production performance, remains a huge challenge. In recent years, a new type of carbon material graphdiyne (GDY) has been proposed. GDY acetylene has a special atomic arrangement that graphene does not have a two-dimensional network of sp 2 and sp conjugated intersections makes it easier to construct active sites and improve photocatalytic ability. In addition, GDY also has the advantage of adjusting the bandgap of other catalysts and inhibiting carrier recombination, making it more prone to hydrogen evolution reactions. In addition to using mechanical ball milling to produce GDY, NiWO 4 without precious metals was also prepared. The sheet-like structure of GDY in the composite catalyst provides a anchoring site and more active sites for the granular NiWO 4 . And the composite catalyst fully enhances the good conductivity of GDY and its unique ability to enhance electron transfer, greatly improving the ability of NiWO 4 as a single substance. Through in-situ x-ray photoelectron spectrometer, it was demonstrated that a p–n heterojunction was constructed between GDY and NiWO 4 in the composite catalyst, further enhancing the synergistic effect between the two, resulting in a hydrogen production rate of 90.92 μ mol for the composite catalyst is 4.56 times higher than that of GDY and 4.97 times higher than that of NiWO 4 , respectively, and the stability of the composite catalyst is significantly higher than that of each single catalyst.
{"title":"Graphdiyne (CnH2n-2) / NiWO4 self-assembled p-n junction characterized with in situ XPS for efficient photocatalytic hydrogen production","authors":"Linqing Zhang, Minjun Lei, zhiliang jin","doi":"10.1088/2053-1583/ad01c8","DOIUrl":"https://doi.org/10.1088/2053-1583/ad01c8","url":null,"abstract":"Abstract As is well known, how to deeply understand the charge separation and charge transfer capabilities of catalysts, as well as how to optimize these capabilities of catalysts to improve hydrogen production performance, remains a huge challenge. In recent years, a new type of carbon material graphdiyne (GDY) has been proposed. GDY acetylene has a special atomic arrangement that graphene does not have a two-dimensional network of sp 2 and sp conjugated intersections makes it easier to construct active sites and improve photocatalytic ability. In addition, GDY also has the advantage of adjusting the bandgap of other catalysts and inhibiting carrier recombination, making it more prone to hydrogen evolution reactions. In addition to using mechanical ball milling to produce GDY, NiWO 4 without precious metals was also prepared. The sheet-like structure of GDY in the composite catalyst provides a anchoring site and more active sites for the granular NiWO 4 . And the composite catalyst fully enhances the good conductivity of GDY and its unique ability to enhance electron transfer, greatly improving the ability of NiWO 4 as a single substance. Through in-situ x-ray photoelectron spectrometer, it was demonstrated that a p–n heterojunction was constructed between GDY and NiWO 4 in the composite catalyst, further enhancing the synergistic effect between the two, resulting in a hydrogen production rate of 90.92 μ mol for the composite catalyst is 4.56 times higher than that of GDY and 4.97 times higher than that of NiWO 4 , respectively, and the stability of the composite catalyst is significantly higher than that of each single catalyst.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135824327","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}
Pub Date : 2023-10-17DOI: 10.1088/2053-1583/ad0401
mrityunjay pandey, Kenji Watanabe, Takashi Taniguchi, Srinivasan Raghavan, U. Chandni
We explore the non-equilibrium transport regime in graphene using a large dc current in combination with a perpendicular magnetic field. The strong in-plane Hall field generated in the graphene channel results in Landau levels that are tilted spatially. The energy of cyclotron orbits in the bulk varies as a function of the spatial position of the guiding center, enabling us to observe a series of compelling features. While Shubnikov–de Haas oscillations are predictably suppressed in the presence of the Hall field, a set of fresh magneto resistance oscillations emerge near the charge neutrality point as a function of dc current. Two branches of oscillations with linear dispersions are evident as we vary carrier density and dc current, the velocities of which closely resemble the transverse acoustic (TA) and longitudinal acoustic (LA) phonon modes, suggestive of phonon-assisted intra-Landau level transitions between adjacent cyclotron orbits. Our results offer unique possibilities to explore non-equilibrium phenomena in two-dimensional materials and van der Waals heterostructures.
{"title":"Phonon-mediated magneto-resonances in biased graphene layers","authors":"mrityunjay pandey, Kenji Watanabe, Takashi Taniguchi, Srinivasan Raghavan, U. Chandni","doi":"10.1088/2053-1583/ad0401","DOIUrl":"https://doi.org/10.1088/2053-1583/ad0401","url":null,"abstract":"We explore the non-equilibrium transport regime in graphene using a large dc current in combination with a perpendicular magnetic field. The strong in-plane Hall field generated in the graphene channel results in Landau levels that are tilted spatially. The energy of cyclotron orbits in the bulk varies as a function of the spatial position of the guiding center, enabling us to observe a series of compelling features. While Shubnikov–de Haas oscillations are predictably suppressed in the presence of the Hall field, a set of fresh magneto resistance oscillations emerge near the charge neutrality point as a function of dc current. Two branches of oscillations with linear dispersions are evident as we vary carrier density and dc current, the velocities of which closely resemble the transverse acoustic (TA) and longitudinal acoustic (LA) phonon modes, suggestive of phonon-assisted intra-Landau level transitions between adjacent cyclotron orbits. Our results offer unique possibilities to explore non-equilibrium phenomena in two-dimensional materials and van der Waals heterostructures.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135993896","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}
Abstract As one of two-dimensional (2D) semiconductor materials, transition metal dichalcogenides (TMDs) have sparked enormous potential in next-generation optoelectronics due to their unique and excellent physical, electronic and optical properties. Controllable growth of wafer-scale 2D TMDs is essential to realize various high-end applications, while it remains challenging. Herein, 2-inch 2D WS2 films were successfully synthesized by ambient pressure chemical vapor deposition based on substrate engineering and space-confined strategies. WS2 nucleation density can be effectively modulated depending on the annealing conditions of sapphire substrate. 2D WS2 films with controllable thickness can be fabricated by adjusting the space-confined height. Moreover, our strategies are demonstrated to be universal for the growth of other 2D TMD semiconductors. WS2-based photodetectors with different thicknesses were systematically investigated. Monolayer WS2 photodetector displays large responsivity of 0.355 A/W and high specific detectivity of 1.48 × 1011 Jones. Multilayer WS2 device exhibits negative self-powered photoresponse. Our work provides a new route for the synthesis of wafer-scale 2D TMD materials, paving the way for high performance integrated optoelectronic devices.
{"title":"Controllable growth of wafer-scale two-dimensional WS2 with outstanding optoelectronic properties","authors":"Shiwei Zhang, Yulong Hao, Fenglin Gao, Xiongqing Wu, Shijie Hao, Mengchun Qiu, Xiaoming Zheng, Yuehua Wei, Guolin Hao","doi":"10.1088/2053-1583/ad0404","DOIUrl":"https://doi.org/10.1088/2053-1583/ad0404","url":null,"abstract":"Abstract As one of two-dimensional (2D) semiconductor materials, transition metal dichalcogenides (TMDs) have sparked enormous potential in next-generation optoelectronics due to their unique and excellent physical, electronic and optical properties. Controllable growth of wafer-scale 2D TMDs is essential to realize various high-end applications, while it remains challenging. Herein, 2-inch 2D WS2 films were successfully synthesized by ambient pressure chemical vapor deposition based on substrate engineering and space-confined strategies. WS2 nucleation density can be effectively modulated depending on the annealing conditions of sapphire substrate. 2D WS2 films with controllable thickness can be fabricated by adjusting the space-confined height. Moreover, our strategies are demonstrated to be universal for the growth of other 2D TMD semiconductors. WS2-based photodetectors with different thicknesses were systematically investigated. Monolayer WS2 photodetector displays large responsivity of 0.355 A/W and high specific detectivity of 1.48 × 1011 Jones. Multilayer WS2 device exhibits negative self-powered photoresponse. Our work provides a new route for the synthesis of wafer-scale 2D TMD materials, paving the way for high performance integrated optoelectronic devices.&#xD;","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"61 30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135993882","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}
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