1
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Zhang Y, Giménez-Santamarina S, Cardona-Serra S, Gao F, Coronado E, Brandbyge M. Strong Electron-Vibration Signals in Weakly Coupled Molecular Junctions: Activation of Spin-Crossover. NANO LETTERS 2024. [PMID: 39092593 DOI: 10.1021/acs.nanolett.4c01684] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/04/2024]
Abstract
Manipulating individual molecular spin states with electronic current has the potential to revolutionize quantum information devices. However, it is still unclear how a current can cause a spin transition in single-molecule devices. Here, we propose a spin-crossover (SCO) mechanism induced by electron-phonon coupling in an iron(II) phthalocyanine molecule situated on a graphene-decoupled Ir(111) substrate. We performed simulations of both elastic and inelastic electron tunneling spectroscopy (IETS), which reveal current-induced Fe-N vibrations and an underestimation of established electron-vibration signals. Going beyond standard perturbation theory, we examined molecules in various charge and spin states using the Franck-Condon framework. The increased probability of spin switching suggests that notable IETS signals indicate SCO triggered by the inelastic vibrational excitation associated with Fe-N stretching.
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Affiliation(s)
- Yachao Zhang
- Guizhou Provincial Key Laboratory of Computational Nano-Material Science, Guizhou Education University, Guiyang 550018, China
- Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | | | | | - Fei Gao
- Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - Eugenio Coronado
- Instituto de Ciencia Molecular (ICMol), Universidad de Valencia, 46980 Paterna, Spain
| | - Mads Brandbyge
- Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
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2
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Leitherer S, Brandbyge M, Solomon GC. Electromigration Forces on Atoms on Graphene Nanoribbons: The Role of Adsorbate-Surface Bonding. JACS AU 2024; 4:189-196. [PMID: 38274269 PMCID: PMC10806770 DOI: 10.1021/jacsau.3c00622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Revised: 11/16/2023] [Accepted: 11/17/2023] [Indexed: 01/27/2024]
Abstract
The synthesis of the two-dimensional (2D) material graphene and nanostructures derived from graphene has opened up an interdisciplinary field at the intersection of chemistry, physics, and materials science. In this field, it is an open question whether intuition derived from molecular or extended solid-state systems governs the physical properties of these materials. In this work, we study the electromigration force on atoms on 2D armchair graphene nanoribbons in an electric field using ab initio simulation techniques. Our findings show that the forces are related to the induced charges in the adsorbate-surface bonds rather than only to the induced atomic charges, and the left and right effective bond order can be used to predict the force direction. Focusing in particular on 3d transition metal atoms, we show how a simple model of a metal atom on benzene can explain the forces in an inorganic chemistry picture. This study demonstrates that atom migration on 2D surfaces in electric fields is governed by a picture that is different from the commonly used electrostatic description of a charged particle in an electric field as the underlying bonding and molecular orbital structure become relevant for the definition of electromigration forces. Accordingly extended models including the ligand field of the atoms might provide a better understanding of adsorbate diffusion on surfaces under nonequilibrium conditions.
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Affiliation(s)
- Susanne Leitherer
- Nano-Science
Center and Department of Chemistry, University
of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Mads Brandbyge
- Department
of Physics, Technical University of Denmark, DK-2800 Kongens
Lyngby, Denmark
| | - Gemma C. Solomon
- Nano-Science
Center and Department of Chemistry, Copenhagen
University, DK-2100 Copenhagen, Denmark
- NNF
Quantum Computing Programme, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark
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3
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Choi YW, Cohen ML. Resonantly Enhanced Electromigration Forces for Adsorbates on Graphene. PHYSICAL REVIEW LETTERS 2022; 129:206801. [PMID: 36461986 DOI: 10.1103/physrevlett.129.206801] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Accepted: 10/20/2022] [Indexed: 06/17/2023]
Abstract
We investigate the electromigration forces for weakly bonded adsorbates on graphene by using density-functional based calculations. We find that the nature of electromigration forces on an adsorbate critically depends on the energy level alignment between the adsorbate state and the Fermi level of the graphene. For a resonant adsorbate, whose frontier orbitals lie close to the Fermi level, the electromigration force is dominated by the electron wind force that is strongly enhanced along the electron flow direction, irrespective of the sign of the adsorbate charge. For a nonresonant adsorbate, the electromigration force is essentially the direct force that depends on the adsorbate charge. We also show that the magnitude of electromigration forces can be continuously tunable through electrostatic gating for resonant adsorbates. Our results provide new insight for understanding and controlling how nanoscale objects behave in or on host materials.
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Affiliation(s)
- Young Woo Choi
- Department of Physics, University of California, Berkeley, California 94720, USA and Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Marvin L Cohen
- Department of Physics, University of California, Berkeley, California 94720, USA and Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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4
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Huang Y, Altalhi T, Yakobson BI, Penev ES. Nucleobase-Bonded Graphene Nanoribbon Junctions: Electron Transport from First Principles. ACS NANO 2022; 16:16736-16743. [PMID: 36198132 DOI: 10.1021/acsnano.2c06274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Carbon and hydrogen bonding constitute the backbone of life; in the form of graphene, possibly functionalized by DNA nucleobases, these hold promise for the programmable assembly of graphene-based nanoelectronic devices. It is still unknown how hydrogen-bonded junctions inherent in such devices will perform as electron transport media. Here, we design nucleobase-bonded graphene nanoribbons and quantify their quantum transport characteristics using first-principles calculations. Pronounced rectifying behavior and negative differential resistance are found, as well as high conductance of certain structures, with the guanine-cytosine junction in general being superior to the adenine-thymine junction. The identified sensitivity of the conductance to atomic details of the interfaces offers initial hints and guidance for experimental realization. The dependence of current on electrostatic gate doping, with an on/off ratio of ∼102, shows the potential of the junction as a field effect transistor.
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Affiliation(s)
- Yuefei Huang
- Department of Materials Science and NanoEngineering, Rice University, Houston, Texas77005, United States
| | - Tariq Altalhi
- Chemistry Department, Taif University, Taif21974, Saudi Arabia
| | - Boris I Yakobson
- Chemistry Department, Taif University, Taif21974, Saudi Arabia
- Department of Chemistry, Rice University, Houston, Texas77005, United States
| | - Evgeni S Penev
- Department of Materials Science and NanoEngineering, Rice University, Houston, Texas77005, United States
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5
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Gao F, Li D, Barreteau C, Brandbyge M. Proposal for All-Electrical Spin Manipulation and Detection for a Single Molecule on Boron-Substituted Graphene. PHYSICAL REVIEW LETTERS 2022; 129:027201. [PMID: 35867446 DOI: 10.1103/physrevlett.129.027201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 03/08/2022] [Accepted: 06/03/2022] [Indexed: 06/15/2023]
Abstract
All-electrical writing and reading of spin states attract considerable attention for their promising applications in energy-efficient spintronics devices. Here we show, based on rigorous first-principles calculations, that the spin properties can be manipulated and detected in molecular spinterfaces, where an iron tetraphenyl porphyrin (FeTPP) molecule is deposited on boron-substituted graphene (BG). Notably, a reversible spin switching between the S=1 and S=3/2 states is achieved by a gate electrode. We can trace the origin to a strong hybridization between the Fe-d_{z^{2}} and B-p_{z} orbitals. Combining density functional theory with nonequilibrium Green's function formalism, we propose an experimentally feasible three-terminal setup to probe the spin state. Furthermore, we show how the in-plane quantum transport for the BG, which is non-spin polarized, can be modified by FeTPP, yielding a significant transport spin polarization near the Fermi energy (>10% for typical coverage). Our work paves the way to realize all-electrical spintronics devices using molecular spinterfaces.
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Affiliation(s)
- Fei Gao
- Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - Dongzhe Li
- CEMES, Université de Toulouse, CNRS, 29 rue Jeanne Marvig, F-31055 Toulouse, France
| | - Cyrille Barreteau
- Université Paris-Saclay, CEA, CNRS, SPEC, 91191 Gif-sur-Yvette, France
| | - Mads Brandbyge
- Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
- Center for Nanostructured Graphene, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
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6
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Alcón I, Calogero G, Papior N, Antidormi A, Song K, Cummings AW, Brandbyge M, Roche S. Unveiling the Multiradical Character of the Biphenylene Network and Its Anisotropic Charge Transport. J Am Chem Soc 2022; 144:8278-8285. [PMID: 35476458 PMCID: PMC9100647 DOI: 10.1021/jacs.2c02178] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Recent progress in the on-surface synthesis and characterization of nanomaterials is facilitating the realization of new carbon allotropes, such as nanoporous graphenes, graphynes, and 2D π-conjugated polymers. One of the latest examples is the biphenylene network (BPN), which was recently fabricated on gold and characterized with atomic precision. This gapless 2D organic material presents uncommon metallic conduction, which could help develop innovative carbon-based electronics. Here, using first principles calculations and quantum transport simulations, we provide new insights into some fundamental properties of BPN, which are key for its further technological exploitation. We predict that BPN hosts an unprecedented spin-polarized multiradical ground state, which has important implications for the chemical reactivity of the 2D material under practical use conditions. The associated electronic band gap is highly sensitive to perturbations, as seen in finite temperature (300 K) molecular dynamics simulations, but the multiradical character remains stable. Furthermore, BPN is found to host in-plane anisotropic (spin-polarized) electrical transport, rooted in its intrinsic structural features, which suggests potential device functionality of interest for both nanoelectronics and spintronics.
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Affiliation(s)
- Isaac Alcón
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, Barcelona 08193, Spain.,Institut für Chemie und Biochemie, Physikalische und Theoretische Chemie, Freie Universität Berlin, Arnimallee 22, Berlin 14195, Germany
| | - Gaetano Calogero
- CNR Institute for Microelectronics and Microsystems (CNR-IMM), Zona Industriale, Strada VIII, 5, Catania 95121, Italy
| | - Nick Papior
- Computing Center, Technical University of Denmark, Kongens Lyngby DK-2800, Denmark
| | - Aleandro Antidormi
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, Barcelona 08193, Spain
| | - Kenan Song
- Physical Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955, Saudi Arabia
| | - Aron W Cummings
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, Barcelona 08193, Spain
| | - Mads Brandbyge
- Department of Physics, Technical University of Denmark, Kongens Lyngby DK-2800, Denmark.,Center for Nanostructured Graphene (CNG), Kongens Lyngby DK-2800, Denmark
| | - Stephan Roche
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, Barcelona 08193, Spain.,ICREA-Institució Catalana de Recerca i Estudis Avançats, Barcelona 08070, Spain
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7
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Omidian M, Leitherer S, Néel N, Brandbyge M, Kröger J. Electric-Field Control of a Single-Atom Polar Bond. PHYSICAL REVIEW LETTERS 2021; 126:216801. [PMID: 34114869 DOI: 10.1103/physrevlett.126.216801] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Revised: 03/07/2021] [Accepted: 04/12/2021] [Indexed: 06/12/2023]
Abstract
We expose the polar covalent bond between a single Au atom terminating the apex of an atomic force microscope tip and a C atom of graphene on SiC(0001) to an external electric field. For one field orientation, the Au─C bond is strong enough to sustain the mechanical load of partially detached graphene, while for the opposite orientation, the bond breaks easily. Calculations based on density-functional theory and nonequilibrium Green's function methods support the experimental observations by unveiling bond forces that reflect the polar character of the bond. Field-induced charge transfer between the atomic orbitals modifies the polarity of the different electronegative reaction partners and the Au─C bond strength.
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Affiliation(s)
- M Omidian
- Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
| | - S Leitherer
- Center of Nanostructured Graphene, Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - N Néel
- Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
| | - M Brandbyge
- Center of Nanostructured Graphene, Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - J Kröger
- Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
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8
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Zaminpayma E, Nayebi P, Emami-Razavi M. Rectification, transport properties of doped defective graphene nanoribbon junctions. NANOTECHNOLOGY 2021; 32:205204. [PMID: 33571982 DOI: 10.1088/1361-6528/abe578] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The transport properties and rectification behavior of junctions which contain armchair graphene nanoribbons (AGNRs) with double vacancy defects or nitrogen-doped in three different sizes of 9, 10 and 12 atoms are studied. The non-equilibrium Green function method and density functional based tight-binding approach are used for different computations. The double vacancy (DV) defects are along the direction of current pathways of graphene devices. We calculated transmission probability, density of states, the current-voltage curves, rectification ratio, and electrodes band structures. We found that I-V graph has nonlinear characteristic and displays rectification behavior. Devices which posses the size of 9 atoms show significant sign of rectification in contrast to other cases (10, 12 atoms). But the current value is more important for the device of 12 atoms size. Moreover, it is shown that extra energy bands are created by the DV defects and nitrogen (N) doped atoms. These bands of DV defects and N-doped cause the Fermi level to shift upwards and can change the behavior (n-type semiconductor, or metal-like) of devices of 9, 10 and 12 AGNRs. Also, various orbital distributions of MPSH (molecularly projected self-consistent Hamiltonian) states in the DV-9AGNR device are investigated.
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Affiliation(s)
| | - Payman Nayebi
- Department of Physics, College of Technical and Engineering, Saveh Branch, Islamic Azad University, Saveh, Iran
| | - Mohsen Emami-Razavi
- Department of Physics, Faculty of Sciences, Science and Research Branch, Islamic Azad University, Tehran, Iran
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9
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Huang P, Zhang P, Xu S, Wang H, Zhang X, Zhang H. Recent advances in two-dimensional ferromagnetism: materials synthesis, physical properties and device applications. NANOSCALE 2020; 12:2309-2327. [PMID: 31930261 DOI: 10.1039/c9nr08890c] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Two-dimensional (2D) ferromagnetism is critical for both scientific investigation and technological development owing to its low-dimensionality that brings in quantization of electronic states as well as free axes for device modulation. However, the scarcity of high-temperature 2D ferromagnets has been the obstacle of many research studies, such as the quantum anomalous Hall effect (QAHE) and thin-film spintronics. Indeed, in the case of the isotropic Heisenberg model with finite-range exchange interactions as an example, low-dimensionality is shown to be contraindicated with ferromagnetism. However, the advantages of low-dimensionality for micro-scale patterning could enhance the Curie temperature (TC) of 2D ferromagnets beyond the TC of bulk materials, opening the door for designing high-temperature ferromagnets in the 2D limit. In this paper, we review the recent advances in the field of 2D ferromagnets, including their material systems, physical properties, and potential device applications.
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Affiliation(s)
- Pu Huang
- Shenzhen Key Laboratory of Flexible Memory Materials and Devices, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.
| | - Peng Zhang
- Shenzhen Key Laboratory of Flexible Memory Materials and Devices, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.
| | - Shaogang Xu
- Shenzhen Key Laboratory of Flexible Memory Materials and Devices, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.
| | - Huide Wang
- Collaborative Innovation Centre for Optoelectronic Science & Technology, and Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.
| | - Xiuwen Zhang
- Shenzhen Key Laboratory of Flexible Memory Materials and Devices, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.
| | - Han Zhang
- Collaborative Innovation Centre for Optoelectronic Science & Technology, and Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.
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10
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Yasini P, Afsari S, Peng H, Pikma P, Perdew JP, Borguet E. Potential-Induced High-Conductance Transport Pathways through Single-Molecule Junctions. J Am Chem Soc 2019; 141:10109-10116. [DOI: 10.1021/jacs.9b05448] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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11
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Calogero G, Papior N, Koleini M, Larsen MHL, Brandbyge M. Multi-scale approach to first-principles electron transport beyond 100 nm. NANOSCALE 2019; 11:6153-6164. [PMID: 30874281 DOI: 10.1039/c9nr00866g] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Multi-scale computational approaches are important for studies of novel, low-dimensional electronic devices since they are able to capture the different length-scales involved in the device operation, and at the same time describe critical parts such as surfaces, defects, interfaces, gates, and applied bias, on a atomistic, quantum-chemical level. Here we present a multi-scale method which enables calculations of electronic currents in two-dimensional devices larger than 100 nm2, where multiple perturbed regions described by density functional theory (DFT) are embedded into an extended unperturbed region described by a DFT-parametrized tight-binding model. We explain the details of the method, provide examples, and point out the main challenges regarding its practical implementation. Finally we apply it to study current propagation in pristine, defected and nanoporous graphene devices, injected by chemically accurate contacts simulating scanning tunneling microscopy probes.
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Affiliation(s)
- Gaetano Calogero
- DTU Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
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12
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Calogero G, Papior NR, Kretz B, Garcia-Lekue A, Frederiksen T, Brandbyge M. Electron Transport in Nanoporous Graphene: Probing the Talbot Effect. NANO LETTERS 2019; 19:576-581. [PMID: 30539639 DOI: 10.1021/acs.nanolett.8b04616] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Electrons in graphene can show diffraction and interference phenomena fully analogous to light thanks to their Dirac-like energy dispersion. However, it is not clear how this optical analogy persists in nanostructured graphene, for example, with pores. Nanoporous graphene (NPG) consisting of linked graphene nanoribbons has recently been fabricated using molecular precursors and bottom-up assembly (Moreno et al. Science 2018, 360, 199). We predict that electrons propagating in NPG exhibit the interference Talbot effect, analogous to photons in coupled waveguides. Our results are obtained by parameter-free atomistic calculations of real-sized NPG samples based on seamlessly integrated density functional theory and tight-binding regions. We link the origins of this interference phenomenon to the band structure of the NPG. Most importantly, we demonstrate how the Talbot effect may be detected experimentally using dual-probe scanning tunneling microscopy. Talbot interference of electron waves in NPG or other related materials may open up new opportunities for future quantum electronics, computing, or sensing.
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Affiliation(s)
- Gaetano Calogero
- Department of Micro- and Nanotechnology, Center for Nanostructured Graphene (CNG) , Technical University of Denmark , DK-2800 Kongens Lyngby , Denmark
| | - Nick R Papior
- Department of Micro- and Nanotechnology, Center for Nanostructured Graphene (CNG) , Technical University of Denmark , DK-2800 Kongens Lyngby , Denmark
| | - Bernhard Kretz
- Institute of Theoretical Physics , University of Regensburg , 93040 Regensburg , Germany
| | - Aran Garcia-Lekue
- Donostia International Physics Center (DIPC) , 20018 San Sebastian , Spain
- Ikerbasque, Basque Foundation for Science , 48013 Bilbao , Spain
| | - Thomas Frederiksen
- Donostia International Physics Center (DIPC) , 20018 San Sebastian , Spain
- Ikerbasque, Basque Foundation for Science , 48013 Bilbao , Spain
| | - Mads Brandbyge
- Department of Micro- and Nanotechnology, Center for Nanostructured Graphene (CNG) , Technical University of Denmark , DK-2800 Kongens Lyngby , Denmark
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13
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Palsgaard M, Gunst T, Markussen T, Thygesen KS, Brandbyge M. Stacked Janus Device Concepts: Abrupt pn-Junctions and Cross-Plane Channels. NANO LETTERS 2018; 18:7275-7281. [PMID: 30339398 DOI: 10.1021/acs.nanolett.8b03474] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Janus transition metal dichalcogenides with a built-in structural cross-plane (cp) asymmetry have recently emerged as a new class of two-dimensional materials with a large cp dipole. Using first-principles calculations, and a tailored transport method, we demonstrate that stacking graphene and MoSSe Janus structures result in record high homogeneous doping of graphene and abrupt, atomically thin, cross-plane pn-junctions. We show how graphene in contrast to metals can act as electrodes to Janus stacks without screening the cp dipole and predict a large photocurrent response dominated by a cp transport channel in a few-layer stacked device. The photocurrent is above that of a corresponding thin-film silicon device illustrating the great potential of Janus stacks, for example, in photovoltaic devices.
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Affiliation(s)
- Mattias Palsgaard
- Synopsys-QuantumWise , Fruebjergvej 3 , Postbox 4, DK-2100 Copenhagen , Denmark
- Department of Micro- and Nanotechnology (DTU Nanotech) , Technical University of Denmark , DK-2800 Kgs. Lyngby , Denmark
- Center for Nanostructured Graphene (CNG) , Technical University of Denmark DK-2800 Kgs. Lyngby , Denmark
| | - Tue Gunst
- Department of Micro- and Nanotechnology (DTU Nanotech) , Technical University of Denmark , DK-2800 Kgs. Lyngby , Denmark
- Center for Nanostructured Graphene (CNG) , Technical University of Denmark DK-2800 Kgs. Lyngby , Denmark
| | - Troels Markussen
- Synopsys-QuantumWise , Fruebjergvej 3 , Postbox 4, DK-2100 Copenhagen , Denmark
| | - Kristian Sommer Thygesen
- Center for Nanostructured Graphene (CNG) , Technical University of Denmark DK-2800 Kgs. Lyngby , Denmark
- Department of Physics, Center for Atomic-scale Materials Design (CAMD) , Technical University of Denmark , DK-2800 Kgs. Lyngby , Denmark
| | - Mads Brandbyge
- Department of Micro- and Nanotechnology (DTU Nanotech) , Technical University of Denmark , DK-2800 Kgs. Lyngby , Denmark
- Center for Nanostructured Graphene (CNG) , Technical University of Denmark DK-2800 Kgs. Lyngby , Denmark
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14
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Calogero G, Papior NR, Bøggild P, Brandbyge M. Large-scale tight-binding simulations of quantum transport in ballistic graphene. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:364001. [PMID: 30061475 DOI: 10.1088/1361-648x/aad6f1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Graphene has proven to host outstanding mesoscopic effects involving massless Dirac quasiparticles travelling ballistically resulting in the current flow exhibiting light-like behaviour. A new branch of 2D electronics inspired by the standard principles of optics is rapidly evolving, calling for a deeper understanding of transport in large-scale devices at a quantum level. Here we perform large-scale quantum transport calculations based on a tight-binding model of graphene and the non-equilibrium Green's function method and include the effects of p-n junctions of different shape, magnetic field, and absorptive regions acting as drains for current. We stress the importance of choosing absorbing boundary conditions in the calculations to correctly capture how current flows in the limit of infinite devices. As a specific application we present a fully quantum-mechanical framework for the '2D Dirac fermion microscope' recently proposed by Bøggild et al (2017 Nat. Commun. 8 10.1038), tackling several key electron-optical effects therein predicted via semiclassical trajectory simulations, such as electron beam collimation, deflection and scattering off Veselago dots. Our results confirm that a semiclassical approach to a large extend is sufficient to capture the main transport features in the mesoscopic limit and the optical regime, but also that a richer electron-optical landscape is to be expected when coherence or other purely quantum effects are accounted for in the simulations.
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Affiliation(s)
- Gaetano Calogero
- Department of Micro- and Nanotechnology, Center for Nanostructured Graphene (CNG), Technical University of Denmark, Ørsteds Plads, Bldg. 345E, DK-2800 Kongens Lyngby, Denmark
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15
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Papior NR, Calogero G, Brandbyge M. Simple and efficient LCAO basis sets for the diffuse states in carbon nanostructures. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:25LT01. [PMID: 29762126 DOI: 10.1088/1361-648x/aac4dd] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We present a simple way to describe the lowest unoccupied diffuse states in carbon nanostructures in density functional theory calculations using a minimal LCAO (linear combination of atomic orbitals) basis set. By comparing plane wave basis calculations, we show how these states can be captured by adding long-range orbitals to the standard LCAO basis sets for the extreme cases of planar sp 2 (graphene) and curved carbon (C60). In particular, using Bessel functions with a long range as additional basis functions retain a minimal basis size. This provides a smaller and simpler atom-centered basis set compared to the standard pseudo-atomic orbitals (PAOs) with multiple polarization orbitals or by adding non-atom-centered states to the basis.
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Affiliation(s)
- Nick R Papior
- Department of Micro- and Nanotechnology, Technical University of Denmark, Center for Nanostructured Graphene (CNG), Ørsteds Plads, Bldg. 345E, DK-2800 Kongens Lyngby, Denmark
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Stradi D, Papior NR, Hansen O, Brandbyge M. Field Effect in Graphene-Based van der Waals Heterostructures: Stacking Sequence Matters. NANO LETTERS 2017; 17:2660-2666. [PMID: 28263606 DOI: 10.1021/acs.nanolett.7b00473] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Stacked van der Waals (vdW) heterostructures where semiconducting two-dimensional (2D) materials are contacted by overlaid graphene electrodes enable atomically thin, flexible electronics. We use first-principles quantum transport simulations of graphene-contacted MoS2 devices to show how the transistor effect critically depends on the stacking configuration relative to the gate electrode. We can trace this behavior to the stacking-dependent response of the contact region to the capacitive electric field induced by the gate. The contact resistance is a central parameter and our observation establishes an important design rule for ultrathin devices based on 2D atomic crystals.
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Affiliation(s)
- Daniele Stradi
- Center for Nanostructured Graphene (CNG), Department of Micro- and Nanotechnology (DTU Nanotech), Technical University of Denmark , DK-2800, Kgs. Lyngby, Denmark
- QuantumWise A/S, Fruebjergvej 3, Postbox 4, DK-2100 Copenhagen, Denmark
| | - Nick R Papior
- Center for Nanostructured Graphene (CNG), Department of Micro- and Nanotechnology (DTU Nanotech), Technical University of Denmark , DK-2800, Kgs. Lyngby, Denmark
- ICN2 - Institut Català de Nanociència i Nanotecnologia , Campus UAB, 08193 Bellaterra, Spain
| | - Ole Hansen
- Department of Micro- and Nanotechnology (DTU Nanotech), Technical University of Denmark , DK-2800, Kgs. Lyngby, Denmark
| | - Mads Brandbyge
- Center for Nanostructured Graphene (CNG), Department of Micro- and Nanotechnology (DTU Nanotech), Technical University of Denmark , DK-2800, Kgs. Lyngby, Denmark
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17
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Zhang X, Cong Y, Zhang B. Reduced graphene oxide/liquid crystalline oligomer composites based on reversible covalent chemistry. Phys Chem Chem Phys 2017; 19:6082-6089. [PMID: 28191559 DOI: 10.1039/c6cp07622j] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Xiaodong Zhang
- Center for Molecular Science and Engineering, Northeastern University, 3 Wenhua Road, Shenyang 110819, P. R. China.
| | - Yuehua Cong
- Center for Molecular Science and Engineering, Northeastern University, 3 Wenhua Road, Shenyang 110819, P. R. China.
| | - Baoyan Zhang
- Center for Molecular Science and Engineering, Northeastern University, 3 Wenhua Road, Shenyang 110819, P. R. China.
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18
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Ren H, Zhang G, Lin N, Deng L, Luo Y, Huang F. Strong Fermi level pinning induces a high rectification ratio and negative differential resistance in hydrogen bonding bridged single cytidine pair junctions. Phys Chem Chem Phys 2016; 18:26586-26594. [DOI: 10.1039/c6cp03141b] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Strong Fermi level pinning induces a high rectification ratio and negative differential resistance in hydrogen bonding bridged single cytidine pair junctions.
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Affiliation(s)
- Hao Ren
- State Key Laboratory of Heavy Oil Processing
- Center for Bioengineering & Biotechnology
- China University of Petroleum (East China)
- Qingdao 266580
- P. R. China
| | - Guangping Zhang
- School of Physics and Electronics
- Shandong Normal University
- Jinan
- P. R. China
| | - Na Lin
- State Key Laboratory of Crystal Materials
- Shandong University
- 250100 Jinan
- P. R. China
| | - Li Deng
- State Key Laboratory of Heavy Oil Processing
- Center for Bioengineering & Biotechnology
- China University of Petroleum (East China)
- Qingdao 266580
- P. R. China
| | - Yi Luo
- Hefei National Laboratory for Physical Science at the Microscale and Synergetic Innovation Center of Quantum Information & Quantum Physics
- University of Science and Technology of China
- Hefei
- P. R. China
- Department of Theoretical Chemistry and Biology
| | - Fang Huang
- State Key Laboratory of Heavy Oil Processing
- Center for Bioengineering & Biotechnology
- China University of Petroleum (East China)
- Qingdao 266580
- P. R. China
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