1
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Werkovits A, Hollweger SB, Niederreiter M, Risse T, Cartus JJ, Sterrer M, Matera S, Hofmann OT. Kinetic Trapping of Charge-Transfer Molecules at Metal Interfaces. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2024; 128:3082-3089. [PMID: 38414835 PMCID: PMC10895664 DOI: 10.1021/acs.jpcc.3c08262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Revised: 01/23/2024] [Accepted: 01/24/2024] [Indexed: 02/29/2024]
Abstract
Despite the common expectation that conjugated organic molecules on metals adsorb in a flat-lying layer, several recent studies have found coverage-dependent transitions to upright-standing phases, which exhibit notably different physical properties. In this work, we argue that from an energetic perspective, thermodynamically stable upright-standing phases may be more common than hitherto thought. However, for kinetic reasons, this phase may often not be observed experimentally. Using first-principles kinetic Monte Carlo simulations, we find that the structure with lower molecular density is (almost) always formed first, reminiscent of Ostwald's rule of stages. The phase transitions to the upright-standing phase are likely to be kinetically hindered under the conditions typically used in surface science. The simulation results are experimentally confirmed for the adsorption of tetracyanoethylene on Cu(111) using infrared and X-ray photoemission spectroscopy. Investigating both the role of the growth conditions and the energetics of the interface, we find that the time for the phase transition is determined mostly by the deposition rate and, thus, is mostly independent of the nature of the molecule.
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Affiliation(s)
- Anna Werkovits
- Institute
of Solid State Physics, Graz University of Technology, Petersgasse 16/II, 8010 Graz, Austria
| | - Simon B. Hollweger
- Institute
of Solid State Physics, Graz University of Technology, Petersgasse 16/II, 8010 Graz, Austria
| | - Max Niederreiter
- Institute
of Physics, University of Graz, Universitätsplatz 5, 8010 Graz, Austria
| | - Thomas Risse
- Institut
für Chemie und Biochemie, Freie Universität Berlin, Arminallee 22, 14195 Berlin, Germany
| | - Johannes J. Cartus
- Institute
of Solid State Physics, Graz University of Technology, Petersgasse 16/II, 8010 Graz, Austria
| | - Martin Sterrer
- Institute
of Physics, University of Graz, Universitätsplatz 5, 8010 Graz, Austria
| | - Sebastian Matera
- Theory
Department, Fritz Haber Institute of the
MPG, Faradayweg 4-6, 14195 Berlin-Dahlem, Germany
| | - Oliver T. Hofmann
- Institute
of Solid State Physics, Graz University of Technology, Petersgasse 16/II, 8010 Graz, Austria
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2
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Ding P, Braim M, Hobson AL, Rochford LA, Ryan PTP, Duncan DA, Lee TL, Hussain H, Costantini G, Yu M, Woodruff DP. Does F 4TCNQ Adsorption on Cu(111) Form a 2D-MOF? THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2023; 127:20903-20910. [PMID: 37908743 PMCID: PMC10614301 DOI: 10.1021/acs.jpcc.3c04927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/22/2023] [Revised: 09/21/2023] [Indexed: 11/02/2023]
Abstract
The results of a quantitative experimental structural investigation of the adsorption phases formed by 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanoquinodimethane (F4TCNQ) on Cu(111) are reported. A particular objective was to establish whether Cu adatoms are incorporated into the molecular overlayer. A combination of normal incidence X-ray standing waves, low-energy electron diffraction, scanning tunneling microscopy, and X-ray photoelectron spectroscopy measurements, complemented by dispersion-inclusive density functional theory calculations, demonstrates that F4TCNQ on Cu(111) does cause Cu adatoms to be incorporated into the overlayer to form a two-dimensional metal-organic framework (2D-MOF). This conclusion is shown to be consistent with the behavior of F4TCNQ adsorption on other coinage metal surfaces, despite an earlier report concluding that the adsorption structure on Cu(111) is consistent with the absence of any substrate reconstruction.
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Affiliation(s)
- Pengcheng Ding
- Department
of Physics, University of Warwick, Coventry CV4 7AL, U.K.
- Laboratory
for Space Environment and Physical Sciences, School of Chemistry and
Chemical Engineering, Harbin Institute of
Technology, Harbin 150001, China
| | - Mona Braim
- Department
of Physics, University of Warwick, Coventry CV4 7AL, U.K.
| | - A. L. Hobson
- Department
of Physics, University of Warwick, Coventry CV4 7AL, U.K.
- Diamond
Light Source, Harwell Science and Innovation
Campus, Didcot, Oxford OX11 0DE, U.K.
| | - L. A. Rochford
- Diamond
Light Source, Harwell Science and Innovation
Campus, Didcot, Oxford OX11 0DE, U.K.
| | - P. T. P. Ryan
- Diamond
Light Source, Harwell Science and Innovation
Campus, Didcot, Oxford OX11 0DE, U.K.
- Department
of Materials, Imperial College London, London SW7 2AZ, U.K.
| | - D. A. Duncan
- Diamond
Light Source, Harwell Science and Innovation
Campus, Didcot, Oxford OX11 0DE, U.K.
| | - T.-L. Lee
- Diamond
Light Source, Harwell Science and Innovation
Campus, Didcot, Oxford OX11 0DE, U.K.
| | - H. Hussain
- Diamond
Light Source, Harwell Science and Innovation
Campus, Didcot, Oxford OX11 0DE, U.K.
| | - G. Costantini
- Department
of Chemistry, University of Warwick, Coventry CV4 7AL, U.K.
- School of
Chemistry, University of Birmingham, Birmingham B15 2TT, U.K.
| | - Miao Yu
- Laboratory
for Space Environment and Physical Sciences, School of Chemistry and
Chemical Engineering, Harbin Institute of
Technology, Harbin 150001, China
| | - D. P. Woodruff
- Department
of Physics, University of Warwick, Coventry CV4 7AL, U.K.
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3
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Borca B, Michnowicz T, Aguilar-Galindo F, Pétuya R, Pristl M, Schendel V, Pentegov I, Kraft U, Klauk H, Wahl P, Arnau A, Schlickum U. Chiral and Catalytic Effects of Site-Specific Molecular Adsorption. J Phys Chem Lett 2023; 14:2072-2077. [PMID: 36799542 PMCID: PMC9986952 DOI: 10.1021/acs.jpclett.2c03575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Accepted: 02/13/2023] [Indexed: 06/18/2023]
Abstract
The changes of properties and preferential interactions based on subtle energetic differences are important characteristics of organic molecules, particularly for their functionalities in biological systems. Only slightly energetically favored interactions are important for the molecular adsorption and bonding to surfaces, which define their properties for further technological applications. Here, prochiral tetracenothiophene molecules are adsorbed on the Cu(111) surface. The chiral adsorption configurations are determined by Scanning Tunneling Microscopy studies and confirmed by first-principles calculations. Remarkably, the selection of the adsorption sites by chemically different moieties of the molecules is dictated by the arrangement of the atoms in the first and second surface layers. Furthermore, we have investigated the thermal effects on the direct desulfurization reaction that occurs under the catalytic activity of the Cu substrate. This reaction leads to a product that is covalently bound to the surface in chiral configurations.
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Affiliation(s)
- Bogdana Borca
- Max
Planck Institute for Solid State Research, 70569 Stuttgart, Germany
- National
Institute of Materials Physics, Atomistilor 405A, 077125 Magurele, Ilfov, Romania
| | - Tomasz Michnowicz
- Max
Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | | | - Rémi Pétuya
- Donostia
International Physics Center, E-20018 Donostia - San Sebastián, Spain
| | - Marcel Pristl
- Max
Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Verena Schendel
- Max
Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Ivan Pentegov
- Max
Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Ulrike Kraft
- Max
Planck Institute for Solid State Research, 70569 Stuttgart, Germany
- Max
Planck Institute for Polymer Research, Mainz 55128, Germany
| | - Hagen Klauk
- Max
Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Peter Wahl
- Max
Planck Institute for Solid State Research, 70569 Stuttgart, Germany
- SUPA,
School of Physics and Astronomy, University
of St Andrews, North Haugh, St Andrews KY16 9SS, United Kingdom
| | - Andrés Arnau
- Donostia
International Physics Center, E-20018 Donostia - San Sebastián, Spain
- Departamento
de Polímeros y Materiales Avanzados: Física,
Química y Tecnología UPV/EHU and Material
Physics Center (MPC), Centro Mixto CSIC-UPV/EHU, E-20018 Donostia
- San Sebastián, Spain
| | - Uta Schlickum
- Max
Planck Institute for Solid State Research, 70569 Stuttgart, Germany
- Institute
of Applied Physics and Laboratory for Emerging Nanometrology, Technische Universität Braunschweig, 38104 Braunschweig, Germany
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4
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Sohail B, Blowey PJ, Rochford LA, Ryan PTP, Duncan DA, Lee TL, Starrs P, Costantini G, Woodruff DP, Maurer RJ. Donor-Acceptor Co-Adsorption Ratio Controls the Structure and Electronic Properties of Two-Dimensional Alkali-Organic Networks on Ag(100). THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2023; 127:2716-2727. [PMID: 36798903 PMCID: PMC9923740 DOI: 10.1021/acs.jpcc.2c08688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 01/12/2023] [Indexed: 06/18/2023]
Abstract
The results are presented of a detailed combined experimental and theoretical investigation of the influence of coadsorbed electron-donating alkali atoms and the prototypical electron acceptor molecule 7,7,8,8-tetracyanoquinodimethane (TCNQ) on the Ag(100) surface. Several coadsorption phases were characterized by scanning tunneling microscopy, low-energy electron diffraction, and soft X-ray photoelectron spectroscopy. Quantitative structural data were obtained using normal-incidence X-ray standing wave (NIXSW) measurements and compared with the results of density functional theory (DFT) calculations using several different methods of dispersion correction. Generally, good agreement between theory and experiment was achieved for the quantitative structures, albeit with the prediction of the alkali atom heights being challenging for some methods. The adsorption structures depend sensitively on the interplay of molecule-metal charge transfer and long-range dispersion forces, which are controlled by the composition ratio between alkali atoms and TCNQ. The large difference in atomic size between K and Cs has negligible effects on stability, whereas increasing the ratio of K/TCNQ from 1:4 to 1:1 leads to a weakening of molecule-metal interaction strength in favor of stronger ionic bonds within the two-dimensional alkali-organic network. A strong dependence of the work function on the alkali donor-TCNQ acceptor coadsorption ratio is predicted.
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Affiliation(s)
- B. Sohail
- Department
of Chemistry, University of Warwick, CoventryCV4 7AL, U.K.
| | - P. J. Blowey
- Department
of Physics, University of Warwick, CoventryCV4 7AL, U.K.
- Diamond
Light Source, Harwell Science and Innovation Campus, DidcotOX11 0DE, U.K.
| | - L. A. Rochford
- School
of Chemistry, University of Birmingham, BirminghamB15 2TT, U.K.
| | - P. T. P. Ryan
- Diamond
Light Source, Harwell Science and Innovation Campus, DidcotOX11 0DE, U.K.
- Department
of Materials, Imperial College, London, LondonSW7 2AZ, U.K.
| | - D. A. Duncan
- Diamond
Light Source, Harwell Science and Innovation Campus, DidcotOX11 0DE, U.K.
| | - T.-L. Lee
- Diamond
Light Source, Harwell Science and Innovation Campus, DidcotOX11 0DE, U.K.
| | - P. Starrs
- Diamond
Light Source, Harwell Science and Innovation Campus, DidcotOX11 0DE, U.K.
- School of
Chemistry, University of St. Andrews, St. AndrewsKY16 9AJ, U.K.
| | - G. Costantini
- Department
of Physics, University of Warwick, CoventryCV4 7AL, U.K.
- School
of Chemistry, University of Birmingham, BirminghamB15 2TT, U.K.
| | - D. P. Woodruff
- Department
of Physics, University of Warwick, CoventryCV4 7AL, U.K.
| | - R. J. Maurer
- Department
of Chemistry, University of Warwick, CoventryCV4 7AL, U.K.
- Department
of Physics, University of Warwick, CoventryCV4 7AL, U.K.
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5
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Mousley P, Rochford LA, Ryan PTP, Blowey P, Lawrence J, Duncan DA, Hussain H, Sohail B, Lee TL, Bell GR, Costantini G, Maurer RJ, Nicklin C, Woodruff DP. Direct Experimental Evidence for Substrate Adatom Incorporation into a Molecular Overlayer. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2022; 126:7346-7355. [PMID: 35521631 PMCID: PMC9059187 DOI: 10.1021/acs.jpcc.2c01432] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 04/08/2022] [Indexed: 05/19/2023]
Abstract
While the phenomenon of metal substrate adatom incorporation into molecular overlayers is generally believed to occur in several systems, the experimental evidence for this relies on the interpretation of scanning tunneling microscopy (STM) images, which can be ambiguous and provides no quantitative structural information. We show that surface X-ray diffraction (SXRD) uniquely provides unambiguous identification of these metal adatoms. We present the results of a detailed structural study of the Au(111)-F4TCNQ system, combining surface characterization by STM, low-energy electron diffraction, and soft X-ray photoelectron spectroscopy with quantitative experimental structural information from normal incidence X-ray standing wave (NIXSW) and SXRD, together with dispersion-corrected density functional theory (DFT) calculations. Excellent agreement is found between the NIXSW data and the DFT calculations regarding the height and conformation of the adsorbed molecule, which has a twisted geometry rather than the previously supposed inverted bowl shape. SXRD measurements provide unequivocal evidence for the presence and location of Au adatoms, while the DFT calculations show this reconstruction to be strongly energetically favored.
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Affiliation(s)
- Philip
J. Mousley
- Diamond
Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, U.K.
| | - Luke A. Rochford
- Chemistry
Department, University of Birmingham, University Road, Birmingham B15 2TT, U.K.
| | - Paul T. P. Ryan
- Diamond
Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, U.K.
- Department
of Materials, Imperial College, London SW7 2AZ, U.K.
| | - Philip Blowey
- Diamond
Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, U.K.
- Department
of Physics, University of Warwick, Coventry CV4 7AL, U.K.
| | - James Lawrence
- Department
of Chemistry, University of Warwick, Coventry CV4 7AL, U.K.
| | - David A. Duncan
- Diamond
Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, U.K.
| | - Hadeel Hussain
- Diamond
Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, U.K.
| | - Billal Sohail
- Department
of Chemistry, University of Warwick, Coventry CV4 7AL, U.K.
| | - Tien-Lin Lee
- Diamond
Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, U.K.
| | - Gavin R. Bell
- Department
of Physics, University of Warwick, Coventry CV4 7AL, U.K.
| | | | | | - Christopher Nicklin
- Diamond
Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, U.K.
| | - D. Phil Woodruff
- Department
of Physics, University of Warwick, Coventry CV4 7AL, U.K.
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6
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Ryan P, Blowey PJ, Sohail BS, Rochford LA, Duncan DA, Lee TL, Starrs P, Costantini G, Maurer RJ, Woodruff DP. Thermodynamic Driving Forces for Substrate Atom Extraction by Adsorption of Strong Electron Acceptor Molecules. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2022; 126:6082-6090. [PMID: 35432689 PMCID: PMC9007530 DOI: 10.1021/acs.jpcc.2c00711] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Revised: 03/13/2022] [Indexed: 05/29/2023]
Abstract
A quantitative structural investigation is reported, aimed at resolving the issue of whether substrate adatoms are incorporated into the monolayers formed by strong molecular electron acceptors deposited onto metallic electrodes. A combination of normal-incidence X-ray standing waves, low-energy electron diffraction, scanning tunnelling microscopy, and X-ray photoelectron spectroscopy measurements demonstrate that the systems TCNQ and F4TCNQ on Ag(100) lie at the boundary between these two possibilities and thus represent ideal model systems with which to study this effect. A room-temperature commensurate phase of adsorbed TCNQ is found not to involve Ag adatoms, but to adopt an inverted bowl configuration, long predicted but not previously identified experimentally. By contrast, a similar phase of adsorbed F4TCNQ does lead to Ag adatom incorporation in the overlayer, the cyano end groups of the molecule being twisted relative to the planar quinoid ring. Density functional theory (DFT) calculations show that this behavior is consistent with the adsorption energetics. Annealing of the commensurate TCNQ overlayer phase leads to an incommensurate phase that does appear to incorporate Ag adatoms. Our results indicate that the inclusion (or exclusion) of metal atoms into the organic monolayers is the result of both thermodynamic and kinetic factors.
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Affiliation(s)
- Paul Ryan
- Diamond Light
Source, Harwell Science and Innovation Campus, Didcot, OX11 0DE, United Kingdom
- Department
of Materials, Imperial College, London SW7 2AZ, United Kingdom
| | - Philip James Blowey
- Diamond Light
Source, Harwell Science and Innovation Campus, Didcot, OX11 0DE, United Kingdom
- Department
of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Billal S. Sohail
- Department
of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Luke A. Rochford
- Diamond Light
Source, Harwell Science and Innovation Campus, Didcot, OX11 0DE, United Kingdom
| | - David A. Duncan
- Diamond Light
Source, Harwell Science and Innovation Campus, Didcot, OX11 0DE, United Kingdom
| | - Tien-Lin Lee
- Diamond Light
Source, Harwell Science and Innovation Campus, Didcot, OX11 0DE, United Kingdom
| | - Peter Starrs
- Diamond Light
Source, Harwell Science and Innovation Campus, Didcot, OX11 0DE, United Kingdom
- School
of Chemistry, University of St. Andrews, St. Andrews, KY16 9AJ, United Kingdom
| | - Giovanni Costantini
- Department
of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Reinhard J. Maurer
- Department
of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
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7
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Blowey PJ, Sohail B, Rochford LA, Lafosse T, Duncan DA, Ryan PTP, Warr DA, Lee TL, Costantini G, Maurer RJ, Woodruff DP. Alkali Doping Leads to Charge-Transfer Salt Formation in a Two-Dimensional Metal-Organic Framework. ACS NANO 2020; 14:7475-7483. [PMID: 32392035 PMCID: PMC7315632 DOI: 10.1021/acsnano.0c03133] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Accepted: 05/11/2020] [Indexed: 05/22/2023]
Abstract
Efficient charge transfer across metal-organic interfaces is a key physical process in modern organic electronics devices, and characterization of the energy level alignment at the interface is crucial to enable a rational device design. We show that the insertion of alkali atoms can significantly change the structure and electronic properties of a metal-organic interface. Coadsorption of tetracyanoquinodimethane (TCNQ) and potassium on a Ag(111) surface leads to the formation of a two-dimensional charge transfer salt, with properties quite different from those of the two-dimensional Ag adatom TCNQ metal-organic framework formed in the absence of K doping. We establish a highly accurate structural model by combination of quantitative X-ray standing wave measurements, scanning tunnelling microscopy, and density-functional theory (DFT) calculations. Full agreement between the experimental data and the computational prediction of the structure is only achieved by inclusion of a charge-transfer-scaled dispersion correction in the DFT, which correctly accounts for the effects of strong charge transfer on the atomic polarizability of potassium. The commensurate surface layer formed by TCNQ and K is dominated by strong charge transfer and ionic bonding and is accompanied by a structural and electronic decoupling from the underlying metal substrate. The consequence is a significant change in energy level alignment and work function compared to TCNQ on Ag(111). Possible implications of charge-transfer salt formation at metal-organic interfaces for organic thin-film devices are discussed.
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Affiliation(s)
- Phil J. Blowey
- Department
of Physics, University of Warwick, Coventry CV4 7AL, U.K.
- Department
of Chemistry, University of Warwick, Coventry CV4 7AL, U.K.
| | - Billal Sohail
- Department
of Chemistry, University of Warwick, Coventry CV4 7AL, U.K.
| | - Luke A. Rochford
- Chemistry
Department, University of Birmingham, University Road, Birmingham B15 2TT, U.K.
| | - Timothy Lafosse
- Department
of Chemistry, University of Warwick, Coventry CV4 7AL, U.K.
| | - David A. Duncan
- Diamond
Light Source, Harwell Science and Innovation
Campus, Didcot OX11 0DE, U.K.
| | - Paul T. P. Ryan
- Diamond
Light Source, Harwell Science and Innovation
Campus, Didcot OX11 0DE, U.K.
- Department
of Materials, Imperial College, London SW7 2AZ, U.K.
| | | | - Tien-Lin Lee
- Diamond
Light Source, Harwell Science and Innovation
Campus, Didcot OX11 0DE, U.K.
| | | | - Reinhard J. Maurer
- Department
of Chemistry, University of Warwick, Coventry CV4 7AL, U.K.
- E-mail:
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8
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Franco-Cañellas A, Duhm S, Gerlach A, Schreiber F. Binding and electronic level alignment of π-conjugated systems on metals. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2020; 83:066501. [PMID: 32101802 DOI: 10.1088/1361-6633/ab7a42] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
We review the binding and energy level alignment of π-conjugated systems on metals, a field which during the last two decades has seen tremendous progress both in terms of experimental characterization as well as in the depth of theoretical understanding. Precise measurements of vertical adsorption distances and the electronic structure together with ab initio calculations have shown that most of the molecular systems have to be considered as intermediate cases between weak physisorption and strong chemisorption. In this regime, the subtle interplay of different effects such as covalent bonding, charge transfer, electrostatic and van der Waals interactions yields a complex situation with different adsorption mechanisms. In order to establish a better understanding of the binding and the electronic level alignment of π-conjugated molecules on metals, we provide an up-to-date overview of the literature, explain the fundamental concepts as well as the experimental techniques and discuss typical case studies. Thereby, we relate the geometric with the electronic structure in a consistent picture and cover the entire range from weak to strong coupling.
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Affiliation(s)
- Antoni Franco-Cañellas
- Institut für Angewandte Physik, Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
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9
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Otero R, Miranda R, Gallego JM. A Comparative Computational Study of the Adsorption
of TCNQ and F4-TCNQ on the Coinage Metal Surfaces. ACS OMEGA 2019; 4:16906-16915. [PMID: 31646237 PMCID: PMC6796988 DOI: 10.1021/acsomega.9b02154] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Accepted: 09/11/2019] [Indexed: 05/22/2023]
Abstract
![]()
The
adsorption of tetracyanoquinodimethane and of the closely related
derivative tetrafluorotetracyanoquinodimethane on the (111) surfaces
of the coinage metals, namely, copper, silver, and (unreconstructed)
gold, has been studied by dispersion-corrected ab initio density functional
theory calculations. In order to separate the molecule–substrate
interaction from the effects of molecule–molecule interaction,
only the isolated molecules are considered. The results show that,
in this case, the strength of the interaction of both molecules with
the surfaces decreases in the expected order Cu > Ag > Au. The
total
amount of charge transfer, however, behaves in a different way, being
larger for Ag and smaller for Cu and Au. This trend can be explained
by a combination of the differences in the work functions of the three
metals and the amount of backdonation between the molecule and the
metal.
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Affiliation(s)
- Roberto Otero
- Dep.
de Física de la Materia Condensada, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
- Instituto
Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), Cantoblanco, 28049 Madrid, Spain
| | - Rodolfo Miranda
- Dep.
de Física de la Materia Condensada, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
- Instituto
Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), Cantoblanco, 28049 Madrid, Spain
| | - José M. Gallego
- Instituto
de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid, Spain
- E-mail:
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10
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Martín-Jiménez A, Gallego JM, Miranda R, Otero R. Discrete Electronic Subbands due to Bragg Scattering at Molecular Edges. PHYSICAL REVIEW LETTERS 2019; 122:176801. [PMID: 31107081 DOI: 10.1103/physrevlett.122.176801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Indexed: 06/09/2023]
Abstract
The discretization of the electronic structure of nanometer-size solid systems due to quantum confinement and the concomitant modification of their physical properties is one of the cornerstones for the development of nanoscience and nanotechnology. In this Letter we demonstrate that the Bragg scattering of Cu(111) surface-state electrons by the periodic arrangement of tetracyanoquinodimethane molecules at the edges of self-assembled molecular islands, along with the dominant contribution of backscattering processes to the electronic density of states, discretizes the possible values of the electron momentum parallel to the island edge. The electronic structure consists thus of a discrete number of subbands which occur in a nonclosed space, and therefore without quantum confinement.
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Affiliation(s)
- A Martín-Jiménez
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-NANO), 28049 Madrid, Spain
| | - J M Gallego
- Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC), 28049 Madrid, Spain
| | - R Miranda
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-NANO), 28049 Madrid, Spain
- Departamento de Física de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - R Otero
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-NANO), 28049 Madrid, Spain
- Departamento de Física de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, 28049 Madrid, Spain
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11
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Blowey PJ, Rochford LA, Duncan DA, Warr DA, Lee TL, Woodruff DP, Costantini G. Probing the interplay between geometric and electronic structure in a two-dimensional K-TCNQ charge transfer network. Faraday Discuss 2019; 204:97-110. [PMID: 28792036 DOI: 10.1039/c7fd00093f] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Scanning tunnelling microscopy (STM), low energy electron diffraction (LEED), ultraviolet and soft X-ray photoelectron spectroscopy (UPS and SXPS) have been used to characterise the formation of a coadsorption phase of TCNQ and K on Ag(111), while the normal incident X-ray standing waves (NIXSW) technique has been used to obtain quantitative structural information. STM and LEED show that an ordered incommensurate phase is formed in which the K atoms are surrounded by four TCNQ molecules in a 'windmill' motif, characteristic of other metal/TCNQ phases, in which the nominal TCNQ : K stoichiometry is 1 : 1. UPS and SXPS data indicate the TCNQ is in a negatively-charged state. NIXSW results show that the carbon core of the TCNQ is essentially planar at a height above the Ag(111) surface closely similar to that found without coadsorbed K. In the presence of TCNQ the height of the K ions above the surface is significantly larger than on clean Ag(111), and the ions occupy sites above 'holes' in the TCNQ network. NIXSW data also show that the N atoms in the molecules must occupy sites with at least two different heights above the surface, which can be reconciled by a tilt or twist of the TCNQ molecules, broadly similar to the geometry that occurs in bulk TCNQ/K crystals.
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Affiliation(s)
- P J Blowey
- Department of Physics, University of Warwick, Coventry, CV4 7AL, UK.
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12
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Blowey PJ, Velari S, Rochford LA, Duncan DA, Warr DA, Lee TL, De Vita A, Costantini G, Woodruff DP. Re-evaluating how charge transfer modifies the conformation of adsorbed molecules. NANOSCALE 2018; 10:14984-14992. [PMID: 30051899 PMCID: PMC6088372 DOI: 10.1039/c8nr02237b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2018] [Accepted: 06/13/2018] [Indexed: 05/17/2023]
Abstract
The archetypal electron acceptor molecule, TCNQ, is generally believed to become bent into an inverted bowl shape upon adsorption on the coinage metal surfaces on which it becomes negatively charged. New quantitative experimental structural measurements show that this is not the case for TCNQ on Ag(111). DFT calculations show that the inclusion of dispersion force corrections reduces not only the molecule-substrate layer spacing but also the degree of predicted molecular bonding. However, complete agreement between experimentally-determined and theoretically-predicted structural parameters is only achieved with the inclusion of Ag adatoms into the molecular layer, which is also the energetically favoured configuration. The results highlight the need for both experimental and theoretical quantitative structural methods to reliably understand similar metal-organic interfaces and highlight the need to re-evaluate some previously-investigated systems.
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Affiliation(s)
- P. J. Blowey
- Physics Department
, University of Warwick
,
Coventry CV4 7AL
, UK
.
- Diamond Light Source
,
Didcot
, OX11 0DE
, UK
| | - S. Velari
- Dipartimento di Ingegneria e Architettura
, Università degli Studi di Trieste
,
V. Valerio 10
, Trieste
, Italy
| | - L. A. Rochford
- Department of Chemistry
, University of Warwick
,
Coventry CV4 7AL
, UK
.
- School of Chemistry
, University of Birmingham
,
Edgbaston
, Birmingham
, B15 2TT
, UK
| | | | - D. A. Warr
- Department of Chemistry
, University of Warwick
,
Coventry CV4 7AL
, UK
.
| | - T.-L. Lee
- Diamond Light Source
,
Didcot
, OX11 0DE
, UK
| | - A. De Vita
- Dipartimento di Ingegneria e Architettura
, Università degli Studi di Trieste
,
V. Valerio 10
, Trieste
, Italy
- Department of Physics
, King's College London
,
Strand
, London
, WC2R 2LS
, UK
| | - G. Costantini
- Department of Chemistry
, University of Warwick
,
Coventry CV4 7AL
, UK
.
| | - D. P. Woodruff
- Physics Department
, University of Warwick
,
Coventry CV4 7AL
, UK
.
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