1
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Bajaj A, Ali ME. Anti-ohmic nanoconductors: myth, reality and promise. Phys Chem Chem Phys 2023; 25:9607-9616. [PMID: 36942699 DOI: 10.1039/d3cp00366c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/06/2023]
Abstract
The recent accomplishment in the design of molecular nanowires characterized by increasing conductance with length has led to the origin of an extraordinary new family of molecular junctions referred to as "anti-ohmic" wires. Herein, this highly desirable, non-classical behavior, has been examined for molecules long-enough to exhibit pronounced diradical character in their ground state within the unrestricted DFT formalism with spin symmetry breaking. We demonstrate that highly conjugated acenes signal higher resistance in an open-shell singlet (OSS) configuration as compared to their closed-shell counterparts. This anomaly has been further proven for experimentally certified cumulene wires, which reveals phenomenal modulation in the transport characteristics such that an increasing conductance is observed in the closed-shell limit, while higher cumulenes in the OSS ground state yield regular decay of conductance.
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Affiliation(s)
- Ashima Bajaj
- Institute of Nano Science and Technology, Sector-81, Mohali, Punjab-140306, India.
| | - Md Ehesan Ali
- Institute of Nano Science and Technology, Sector-81, Mohali, Punjab-140306, India.
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2
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Deffner M, Weise MP, Zhang H, Mücke M, Proppe J, Franco I, Herrmann C. Learning Conductance: Gaussian Process Regression for Molecular Electronics. J Chem Theory Comput 2023; 19:992-1002. [PMID: 36692968 DOI: 10.1021/acs.jctc.2c00648] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Experimental studies of charge transport through single molecules often rely on break junction setups, where molecular junctions are repeatedly formed and broken while measuring the conductance, leading to a statistical distribution of conductance values. Modeling this experimental situation and the resulting conductance histograms is challenging for theoretical methods, as computations need to capture structural changes in experiments, including the statistics of junction formation and rupture. This type of extensive structural sampling implies that even when evaluating conductance from computationally efficient electronic structure methods, which typically are of reduced accuracy, the evaluation of conductance histograms is too expensive to be a routine task. Highly accurate quantum transport computations are only computationally feasible for a few selected conformations and thus necessarily ignore the rich conformational space probed in experiments. To overcome these limitations, we investigate the potential of machine learning for modeling conductance histograms, in particular by Gaussian process regression. We show that by selecting specific structural parameters as features, Gaussian process regression can be used to efficiently predict the zero-bias conductance from molecular structures, reducing the computational cost of simulating conductance histograms by an order of magnitude. This enables the efficient calculation of conductance histograms even on the basis of computationally expensive first-principles approaches by effectively reducing the number of necessary charge transport calculations, paving the way toward their routine evaluation.
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Affiliation(s)
- Michael Deffner
- Institute of Inorganic and Applied Chemistry, University of Hamburg, Hamburg22761, Germany.,The Hamburg Centre for Ultrafast Imaging, Hamburg22761, Germany
| | - Marc Philipp Weise
- Institute of Inorganic and Applied Chemistry, University of Hamburg, Hamburg22761, Germany
| | - Haitao Zhang
- Institute of Inorganic and Applied Chemistry, University of Hamburg, Hamburg22761, Germany
| | - Maike Mücke
- Institute of Physical Chemistry, Georg-August University, Göttingen37077, Germany
| | - Jonny Proppe
- Institute of Physical and Theoretical Chemistry, TU Braunschweig, Braunschweig38106, Germany
| | - Ignacio Franco
- Departments of Chemistry and Physics, University of Rochester, Rochester, New York14627-0216, United States
| | - Carmen Herrmann
- Institute of Inorganic and Applied Chemistry, University of Hamburg, Hamburg22761, Germany.,The Hamburg Centre for Ultrafast Imaging, Hamburg22761, Germany
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3
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Li C, Meng X, Weismann A, von Glasenapp JS, Hamer S, Xiang F, Pignedoli CA, Herges R, Berndt R. Effect of an axial ligand on the self-assembly of molecular platforms. Phys Chem Chem Phys 2022; 24:28864-28869. [DOI: 10.1039/d2cp04760h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Sub-monolayer amounts of trioxatriangulenium (TOTA) molecules functionalized with biphenyl on Ag(111) were investigated with scanning tunnelling microscopy.
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Affiliation(s)
- Chao Li
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Xiangzhi Meng
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Alexander Weismann
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Jan-Simon von Glasenapp
- Otto-Diels-Institut für Organische Chemie, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Sebastian Hamer
- Otto-Diels-Institut für Organische Chemie, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Feifei Xiang
- nanotech@surfaces Laboratory, EMPA, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
| | - Carlo A. Pignedoli
- nanotech@surfaces Laboratory, EMPA, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
| | - Rainer Herges
- Otto-Diels-Institut für Organische Chemie, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Richard Berndt
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
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4
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Frauhammer T, Gerhard L, Edelmann K, Lindner M, Valášek M, Mayor M, Wulfhekel W. Addressing a lattice of rotatable molecular dipoles with the electric field of an STM tip. Phys Chem Chem Phys 2021; 23:4874-4881. [PMID: 33616122 DOI: 10.1039/d0cp06146h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Functional molecular groups mounted on specific foot structures are ideal model systems to study intermolecular interactions, due to the possibility to separate the functionality and the adsorption mechanism. Here, we report on the rotational switching of a thioacetate group mounted on a tripodal tetraphenylmethane (TPM) derivative adsorbed in ordered islands on a Au(111) surface. Using low temperature scanning tunnelling microscopy, individual freestanding molecular groups of the lattice can be switched between two bistable orientations. The functional dependence of this rotational switching on the sample bias and tip-sample distance allows us to model the energy landscape of this molecular group as an electric dipole in the electric field of the tunnelling junction. As expected for the interaction of two dipoles, we found states of neighbouring molecules to be correlated.
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Affiliation(s)
- Timo Frauhammer
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), D-76021 Karlsruhe, Germany. and Physikalisches Institut, Karlsruhe Institute of Technology (KIT), D-76131 Karlsruhe, Germany
| | - Lukas Gerhard
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology (KIT), D-76021 Karlsruhe, Germany
| | - Kevin Edelmann
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), D-76021 Karlsruhe, Germany. and Physikalisches Institut, Karlsruhe Institute of Technology (KIT), D-76131 Karlsruhe, Germany
| | - Marcin Lindner
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), D-76021 Karlsruhe, Germany.
| | - Michal Valášek
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), D-76021 Karlsruhe, Germany.
| | - Marcel Mayor
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), D-76021 Karlsruhe, Germany. and Department of Chemistry, University of Basel, St. Johannsring 19, CH-4056 Basel, Switzerland and Lehn Institute of Functional Materials (LIFM), School of Chemistry, Sun Yat-Sen University (SYSU), 510275 Guangzhou, China.
| | - Wulf Wulfhekel
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), D-76021 Karlsruhe, Germany. and Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology (KIT), D-76021 Karlsruhe, Germany
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5
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Abstract
The transfer of the inherent bistability of spin crossover compounds to surfaces has attracted considerable interest in recent years. The deposition of the complexes on surfaces allows investigating them individually and to further understand the microscopic mechanisms at play. Moreover, it offers the prospect of engineering switchable functional surfaces. We review recent progress in the field with a particular focus on the challenges and limits associated with the dominant experimental techniques used, namely near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and scanning tunneling microscopy (STM). One of the main difficulties in NEXAFS-based experiments is to ascertain that the complexes are in direct contact with the surfaces. We show that molecular coverage determination based on the amplitude of the edge-jump of interest is challenging because the latter quantity depends on the substrate. Furthermore, NEXAFS averages the signals of a large number of molecules, which may be in different states. In particular, we highlight that the signal of fragmented molecules is difficult to distinguish from that of intact and functional ones. In contrast, STM allows investigating individual complexes, but the identification of the spin states is at best done indirectly. As quite some of the limits of the techniques are becoming apparent as the field is gaining maturity, their detailed descriptions will be useful for future investigations and for taking a fresh look at earlier reports.
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6
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Jasper-Toennies T, Gruber M, Johannsen S, Frederiksen T, Garcia-Lekue A, Jäkel T, Roehricht F, Herges R, Berndt R. Rotation of Ethoxy and Ethyl Moieties on a Molecular Platform on Au(111). ACS NANO 2020; 14:3907-3916. [PMID: 32073820 DOI: 10.1021/acsnano.0c00029] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Molecular rotors have attracted considerable interest for their prospects in nanotechnology. However, their adsorption on supporting substrates, where they may be addressed individually, usually modifies their properties. Here, we investigate the switching of two closely related three-state rotors mounted on platforms on Au(111) using low-temperature scanning tunneling microscopy and density functional theory calculations. Being physisorbed, the platforms retain important gas-phase properties of the rotor. This simplifies a detailed analysis and permits, for instance, the identification of the vibrational modes involved in the rotation process. The symmetry provided by the platform enables active control of the rotation direction through electrostatic interactions with the tip and charged neighboring adsorbates. The present investigation of two model systems may turn out useful for designing platforms that provide directional rotation and for transferring more sophisticated molecular machines from the gas phase to surfaces.
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Affiliation(s)
- Torben Jasper-Toennies
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität, 24098 Kiel, Germany
| | - Manuel Gruber
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität, 24098 Kiel, Germany
| | - Sven Johannsen
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität, 24098 Kiel, Germany
| | - Thomas Frederiksen
- Donostia International Physics Center, DIPC, Paseo Manuel de Lardizabal 4, E-20018 Donostia-San Sebastián, Spain
- IKERBASQUE, Basque Foundation for Science, E-48013 Bilbao, Spain
| | - Aran Garcia-Lekue
- Donostia International Physics Center, DIPC, Paseo Manuel de Lardizabal 4, E-20018 Donostia-San Sebastián, Spain
- IKERBASQUE, Basque Foundation for Science, E-48013 Bilbao, Spain
| | - Torben Jäkel
- Otto-Diels-Institut für Organische Chemie, Christian-Albrechts-Universität, 24098 Kiel, Germany
| | - Fynn Roehricht
- Otto-Diels-Institut für Organische Chemie, Christian-Albrechts-Universität, 24098 Kiel, Germany
| | - Rainer Herges
- Otto-Diels-Institut für Organische Chemie, Christian-Albrechts-Universität, 24098 Kiel, Germany
| | - Richard Berndt
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität, 24098 Kiel, Germany
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7
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Jasper-Tönnies T, Gruber M, Ulrich S, Herges R, Berndt R. Coverage-Controlled Superstructures of C 3 -Symmetric Molecules: Honeycomb versus Hexagonal Tiling. Angew Chem Int Ed Engl 2020; 59:7008-7017. [PMID: 32106353 PMCID: PMC7216838 DOI: 10.1002/anie.202001383] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Indexed: 11/06/2022]
Abstract
The competition between honeycomb and hexagonal tiling of molecular units can lead to large honeycomb superstructures on surfaces. Such superstructures exhibit pores that may be used as 2D templates for functional guest molecules. Honeycomb superstructures of molecules that comprise a C3 symmetric platform on Au(111) and Ag(111) surfaces are presented. The superstructures cover nearly mesoscopic areas with unit cells containing up to 3000 molecules, more than an order of magnitude larger than previously reported. The unit cell size may be controlled by the coverage. A fairly general model was developed to describe the energetics of honeycomb superstructures built from C3 symmetric units. Based on three parameters that characterize two competing bonding arrangements, the model is consistent with the present experimental data and also reproduces various published results. The model identifies the relevant driving force, mostly related to geometric aspects, of the pattern formation.
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Affiliation(s)
- Torben Jasper-Tönnies
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität, 24098, Kiel, Germany
| | - Manuel Gruber
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität, 24098, Kiel, Germany
| | - Sandra Ulrich
- Otto-Diels-Institut für Organische Chemie, Christian-Albrechts-Universität, 24098, Kiel, Germany
| | - Rainer Herges
- Otto-Diels-Institut für Organische Chemie, Christian-Albrechts-Universität, 24098, Kiel, Germany
| | - Richard Berndt
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität, 24098, Kiel, Germany
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8
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Jasper‐Tönnies T, Gruber M, Ulrich S, Herges R, Berndt R. Coverage‐Controlled Superstructures of
C
3
‐Symmetric Molecules: Honeycomb versus Hexagonal Tiling. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202001383] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Torben Jasper‐Tönnies
- Institut für Experimentelle und Angewandte Physik Christian-Albrechts-Universität 24098 Kiel Germany
| | - Manuel Gruber
- Institut für Experimentelle und Angewandte Physik Christian-Albrechts-Universität 24098 Kiel Germany
| | - Sandra Ulrich
- Otto-Diels-Institut für Organische Chemie Christian-Albrechts-Universität 24098 Kiel Germany
| | - Rainer Herges
- Otto-Diels-Institut für Organische Chemie Christian-Albrechts-Universität 24098 Kiel Germany
| | - Richard Berndt
- Institut für Experimentelle und Angewandte Physik Christian-Albrechts-Universität 24098 Kiel Germany
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9
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Jasper-Tönnies T, Garcia-Lekue A, Frederiksen T, Ulrich S, Herges R, Berndt R. High-conductance contacts to functionalized molecular platforms physisorbed on Au(1 1 1). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:18LT01. [PMID: 30721893 DOI: 10.1088/1361-648x/ab0489] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The conductances of molecules physisorbed to Au(1 1 1) via an extended [Formula: see text] system are probed with the tip of a low-temperature scanning tunneling microscope to maximize the control of the junction geometry. Inert hydrogen, methyl, and reactive propynyl subunits were attached to the platform and stand upright. Because of their different reactivities, either non-bonding (hydrogen and methyl) or bonding (propynyl) tip-molecule contacts are formed. The conductances exhibit little scatter between different experimental runs on different molecules, display distinct evolutions with the tip-subunit distance, and reach contact values of 0.003-0.05 G 0. For equal tip-platform distances the contact conductance of the inert methyl is close to that of the reactive propynyl. Under further compression, the inert species, hydrogen and methyl, are found to be better conductors. This shows that the current flow is not directly correlated with the chemical interaction. Atomistic calculations for the methyl case reproduce the conductance evolution and reveal the role of the junction geometry, forces and orbital symmetries at the tip-molecule interface. The current flow is controlled by orbital symmetries at the electrode interfaces rather than by the energy alignment of the molecular orbitals and electrode states. Functionalized molecular platforms thus open new ways to control and engineer electron conduction through metal-molecule interfaces at the atomic level.
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Affiliation(s)
- Torben Jasper-Tönnies
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität, 24098 Kiel, Germany
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10
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Zhao W, Zou D, Sun Z, Xu Y, Ji G, Yu Y, Yang C. Spin Logic Gates Operated by Protonation and Magnetism in Molecular Combinational Circuits. ADVANCED THEORY AND SIMULATIONS 2019. [DOI: 10.1002/adts.201900057] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Wenkai Zhao
- School of Physics and Optoelectronics EngineeringLudong University Yantai 264025 Shandong P. R. China
| | - Dongqing Zou
- School of Physics and Optoelectronics EngineeringLudong University Yantai 264025 Shandong P. R. China
| | - Zhaopeng Sun
- School of Physics and Optoelectronics EngineeringLudong University Yantai 264025 Shandong P. R. China
| | - Yuqing Xu
- School of Physics and Optoelectronics EngineeringLudong University Yantai 264025 Shandong P. R. China
| | - Guomin Ji
- Department of Electrical and Computer EngineeringUniversity of Oklahoma Norman OK 73019–0390 USA
| | - Yongjiang Yu
- School of Physics and Optoelectronics EngineeringLudong University Yantai 264025 Shandong P. R. China
| | - Chuanlu Yang
- School of Physics and Optoelectronics EngineeringLudong University Yantai 264025 Shandong P. R. China
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11
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Electronic transport in planar atomic-scale structures measured by two-probe scanning tunneling spectroscopy. Nat Commun 2019; 10:1573. [PMID: 30952953 PMCID: PMC6450957 DOI: 10.1038/s41467-019-09315-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Accepted: 02/27/2019] [Indexed: 11/09/2022] Open
Abstract
Miniaturization of electronic circuits into the single-atom level requires novel approaches to characterize transport properties. Due to its unrivaled precision, scanning probe microscopy is regarded as the method of choice for local characterization of atoms and single molecules supported on surfaces. Here we investigate electronic transport along the anisotropic germanium (001) surface with the use of two-probe scanning tunneling spectroscopy and first-principles transport calculations. We introduce a method for the determination of the transconductance in our two-probe experimental setup and demonstrate how it captures energy-resolved information about electronic transport through the unoccupied surface states. The sequential opening of two transport channels within the quasi-one-dimensional Ge dimer rows in the surface gives rise to two distinct resonances in the transconductance spectroscopic signal, consistent with phase-coherence lengths of up to 50 nm and anisotropic electron propagation. Our work paves the way for the electronic transport characterization of quantum circuits engineered on surfaces. Measuring electronic transport at the atomic scale requires atom precise contacts. Here, the authors demonstrate quasi-one-dimensional electronic transport along a single dimer row on a germanium surface using a two probe scanning tunneling microscopy protocol.
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12
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Li J, Sanz S, Corso M, Choi DJ, Peña D, Frederiksen T, Pascual JI. Single spin localization and manipulation in graphene open-shell nanostructures. Nat Commun 2019; 10:200. [PMID: 30643120 PMCID: PMC6331630 DOI: 10.1038/s41467-018-08060-6] [Citation(s) in RCA: 92] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 12/11/2018] [Indexed: 11/09/2022] Open
Abstract
Turning graphene magnetic is a promising challenge to make it an active material for spintronics. Predictions state that graphene structures with specific shapes can spontaneously develop magnetism driven by Coulomb repulsion of π-electrons, but its experimental verification is demanding. Here, we report on the observation and manipulation of individual magnetic moments in graphene open-shell nanostructures on a gold surface. Using scanning tunneling spectroscopy, we detect the presence of single electron spins localized around certain zigzag sites of the carbon backbone via the Kondo effect. We find near-by spins coupled into a singlet ground state and quantify their exchange interaction via singlet-triplet inelastic electron excitations. Theoretical simulations picture how electron correlations result in spin-polarized radical states with the experimentally observed spatial distributions. Extra hydrogen atoms bound to radical sites quench their magnetic moment and switch the spin of the nanostructure in half-integer amounts. Our work demonstrates the intrinsic π-paramagnetism of graphene nanostructures.
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Affiliation(s)
- Jingcheng Li
- CIC nanoGUNE, 20018, Donostia-San Sebastián, Spain
| | - Sofia Sanz
- Donostia International Physics Center (DIPC), 20018, Donostia-San Sebastián, Spain
| | - Martina Corso
- Donostia International Physics Center (DIPC), 20018, Donostia-San Sebastián, Spain.,Centro de Física de Materiales CFM/MPC (CSIC-UPV/EHU), 20018, Donostia-San Sebastián, Spain
| | - Deung Jang Choi
- Donostia International Physics Center (DIPC), 20018, Donostia-San Sebastián, Spain.,Centro de Física de Materiales CFM/MPC (CSIC-UPV/EHU), 20018, Donostia-San Sebastián, Spain.,Ikerbasque, Basque Foundation for Science, 48013, Bilbao, Spain
| | - Diego Peña
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS), and Departamento de Química Orgánica, Universidade de Santiago de Compostela, Santiago de Compostela, 15782, Spain
| | - Thomas Frederiksen
- Donostia International Physics Center (DIPC), 20018, Donostia-San Sebastián, Spain.,Ikerbasque, Basque Foundation for Science, 48013, Bilbao, Spain
| | - Jose Ignacio Pascual
- CIC nanoGUNE, 20018, Donostia-San Sebastián, Spain. .,Ikerbasque, Basque Foundation for Science, 48013, Bilbao, Spain.
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13
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Jasper-Tönnies T, Poltavsky I, Ulrich S, Moje T, Tkatchenko A, Herges R, Berndt R. Stability of functionalized platform molecules on Au(111). J Chem Phys 2018; 149:244705. [PMID: 30599747 DOI: 10.1063/1.5059344] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Trioxatriangulenium (TOTA) platform molecules were functionalized with methyl, ethyl, ethynyl, propynyl, and hydrogen and sublimated onto Au(111) surfaces. Low-temperature scanning tunneling microscopy data reveal that >99% of ethyl-TOTA and methyl-TOTA remain intact, whereas 60% of H-TOTA and >99% of propynyl-TOTA and ethynyl-TOTA decompose. The observed tendency toward fragmentation on Au(111) is opposite to the sequence of gas-phase stabilities of the molecules. Although Au(111) is the noblest of all metal surfaces, the binding energies of the decomposition products to Au(111) destabilize the functionalized platforms by 2 to 3.9 eV (190-370 kJ/mol) and even render some of them unstable as revealed by density functional theory calculations. Van der Waals forces are important, as they drive the adsorption of the platform molecules.
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Affiliation(s)
- Torben Jasper-Tönnies
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Igor Poltavsky
- Physics and Materials Science Research Unit, University of Luxembourg, Luxembourg City L-1511, Luxembourg
| | - Sandra Ulrich
- Otto-Diels-Institut für Organische Chemie, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Tobias Moje
- Otto-Diels-Institut für Organische Chemie, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Alexandre Tkatchenko
- Physics and Materials Science Research Unit, University of Luxembourg, Luxembourg City L-1511, Luxembourg
| | - Rainer Herges
- Otto-Diels-Institut für Organische Chemie, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Richard Berndt
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
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14
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A standing molecule as a single-electron field emitter. Nature 2018; 558:573-576. [PMID: 29950622 DOI: 10.1038/s41586-018-0223-y] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 05/09/2018] [Indexed: 11/09/2022]
Abstract
Scanning probe microscopy makes it possible to image and spectroscopically characterize nanoscale objects, and to manipulate1-3 and excite4-8 them; even time-resolved experiments are now routinely achieved9,10. This combination of capabilities has enabled proof-of-principle demonstrations of nanoscale devices, including logic operations based on molecular cascades 11 , a single-atom transistor 12 , a single-atom magnetic memory cell 13 and a kilobyte atomic memory 14 . However, a key challenge is fabricating device structures that can overcome their attraction to the underlying surface and thus protrude from the two-dimensional flatlands of the surface. Here we demonstrate the fabrication of such a structure: we use the tip of a scanning probe microscope to lift a large planar aromatic molecule (3,4,9,10-perylenetetracarboxylic-dianhydride) into an upright, standing geometry on a pedestal of two metal (silver) adatoms. This atypical and surprisingly stable upright orientation of the single molecule, which under all known circumstances adsorbs flat on metals15,16, enables the system to function as a coherent single-electron field emitter. We anticipate that other metastable adsorbate configurations might also be accessible, thereby opening up the third dimension for the design of functional nanostructures on surfaces.
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15
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van Vreumingen D, Tewari S, Verbeek F, van Ruitenbeek JM. Towards Controlled Single-Molecule Manipulation Using "Real-Time" Molecular Dynamics Simulation: A GPU Implementation. MICROMACHINES 2018; 9:E270. [PMID: 30424203 PMCID: PMC6187332 DOI: 10.3390/mi9060270] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/28/2018] [Revised: 05/24/2018] [Accepted: 05/25/2018] [Indexed: 02/04/2023]
Abstract
Molecular electronics saw its birth with the idea to build electronic circuitry with single molecules as individual components. Even though commercial applications are still modest, it has served an important part in the study of fundamental physics at the scale of single atoms and molecules. It is now a routine procedure in many research groups around the world to connect a single molecule between two metallic leads. What is unknown is the nature of this coupling between the molecule and the leads. We have demonstrated recently (Tewari, 2018, Ph.D. Thesis) our new setup based on a scanning tunneling microscope, which can be used to controllably manipulate single molecules and atomic chains. In this article, we will present the extension of our molecular dynamic simulator attached to this system for the manipulation of single molecules in real time using a graphics processing unit (GPU). This will not only aid in controlled lift-off of single molecules, but will also provide details about changes in the molecular conformations during the manipulation. This information could serve as important input for theoretical models and for bridging the gap between the theory and experiments.
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Affiliation(s)
- Dyon van Vreumingen
- Huygens-Kamerlingh Onnes Laboratorium, Universiteit Leiden, 2333CA Leiden, The Netherlands.
- Leiden Insitute of Advanced Computer Science, Universiteit Leiden, 2333CA Leiden, The Netherlands.
| | - Sumit Tewari
- Huygens-Kamerlingh Onnes Laboratorium, Universiteit Leiden, 2333CA Leiden, The Netherlands.
| | - Fons Verbeek
- Leiden Insitute of Advanced Computer Science, Universiteit Leiden, 2333CA Leiden, The Netherlands.
| | - Jan M van Ruitenbeek
- Huygens-Kamerlingh Onnes Laboratorium, Universiteit Leiden, 2333CA Leiden, The Netherlands.
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16
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Zhang Q, Tao S, Yi R, He C, Zhao C, Su W, Smogunov A, Dappe YJ, Nichols RJ, Yang L. Symmetry Effects on Attenuation Factors in Graphene-Based Molecular Junctions. J Phys Chem Lett 2017; 8:5987-5992. [PMID: 29178793 DOI: 10.1021/acs.jpclett.7b02822] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The unique structural and electronic characteristics of graphene make it an attractive contact for fundamental single-molecule electrical studies. With this in mind, we have probed here the electrical conductance of a molecular junction based on α,ω-diaminoalkane chains sandwiched between a gold and a graphene electrode. Using an STM based I(s) method combined with density functional theory-based transport calculations, we demonstrate that the resulting attenuation factor turns out to be much lower when compared to the standard molecular junction between two gold electrodes. This effect is attributed to asymmetric coupling of the molecule through strong chemisorption at the gold electrode and weaker van der Waals contact at graphene. Moreover, this asymmetric coupling induces higher conductance than that in the same hybrid metal-graphene molecular junction using standard thiol anchoring groups.
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Affiliation(s)
- Qian Zhang
- Department of Chemistry, Xi'an-Jiaotong Liverpool University , 215123 Suzhou, China
- Department of Chemistry, University of Liverpool , Liverpool L69 7ZD, United Kingdom
| | - Shuhui Tao
- Department of Chemistry, Xi'an-Jiaotong Liverpool University , 215123 Suzhou, China
- Department of Chemistry, University of Liverpool , Liverpool L69 7ZD, United Kingdom
| | - Ruowei Yi
- Department of Chemistry, Xi'an-Jiaotong Liverpool University , 215123 Suzhou, China
- Department of Chemistry, University of Liverpool , Liverpool L69 7ZD, United Kingdom
| | - Chunhui He
- Department of Chemistry, Xi'an-Jiaotong Liverpool University , 215123 Suzhou, China
- Department of Chemistry, University of Liverpool , Liverpool L69 7ZD, United Kingdom
| | - Cezhou Zhao
- Department of Electrical and Electronic Engineering, Xi'an-Jiaotong Liverpool University , 215123 Suzhou, China
| | - Weitao Su
- College of Materials and Environmental Engineering, Hangzhou Dianzi University , 310018 Hangzhou, China
| | - Alexander Smogunov
- SPEC, CEA, CNRS, Université Paris-Saclay, CEA Saclay , 91191 Gif-sur-Yvette, Cedex, France
| | - Yannick J Dappe
- SPEC, CEA, CNRS, Université Paris-Saclay, CEA Saclay , 91191 Gif-sur-Yvette, Cedex, France
| | - Richard J Nichols
- Department of Chemistry, University of Liverpool , Liverpool L69 7ZD, United Kingdom
| | - Li Yang
- Department of Chemistry, Xi'an-Jiaotong Liverpool University , 215123 Suzhou, China
- Department of Chemistry, University of Liverpool , Liverpool L69 7ZD, United Kingdom
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