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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Zhou G, Li P, Xiao Y, Chen S, Weng S, Dong R, Lin D, Wu DY, Yang L. Observing π-Au Interaction between Aromatic Molecules and Single Au Nanodimers with a Subnanometer Gap by SERS. Anal Chem 2024; 96:197-203. [PMID: 38016046 DOI: 10.1021/acs.analchem.3c03600] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2023]
Abstract
Interface interaction between aromatic molecules and noble metals plays a prominent role in fundamental science and technological applications. However, probing π-metal interactions under ambient conditions remains challenging, as it requires characterization techniques to have high sensitivity and molecular specificity without any restrictions on the sample. Herein, the interactions between polycyclic aromatic hydrocarbon (PAH) molecules and Au nanodimers with a subnanometer gap are investigated by surface-enhanced Raman spectroscopy (SERS). A cleaner and stronger plasmonic field of subnanometer gap Au nanodimer structures was constructed through solvent extraction. High sensitivity and strong π-Au interaction between PAHs and Au nanodimers are observed. Additionally, the density functional theory calculation confirmed the interactions of PAHs physically absorbed on the Au surface; the binding energy and differential charge further theoretically indicated the correlation between the sensitivity and the number of PAH rings, which is consistent with SERS experimental results. This work provides a new method to understand the interactions between aromatic molecules and noble metal surfaces in an ambient environment, also paving the way for designing the interfaces in the fields of catalysis, sensors, and molecular electronics.
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Affiliation(s)
- Guoliang Zhou
- Institute of Health and Medical Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
- University of Science & Technology of China, Hefei 230026, Anhui China
| | - Pan Li
- Institute of Health and Medical Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
- Department of Pharmacy, Hefei Cancer Hospital, Chinese Academy of Sciences, Hefei 230031, Anhui China
| | - Yuanhui Xiao
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Siyu Chen
- Institute of Health and Medical Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
- University of Science & Technology of China, Hefei 230026, Anhui China
| | - Shirui Weng
- Institute of Health and Medical Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
| | - Ronglu Dong
- Institute of Health and Medical Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
| | - Dongyue Lin
- Institute of Health and Medical Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
- Department of Pharmacy, Hefei Cancer Hospital, Chinese Academy of Sciences, Hefei 230031, Anhui China
| | - De-Yin Wu
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Liangbao Yang
- Institute of Health and Medical Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
- University of Science & Technology of China, Hefei 230026, Anhui China
- Department of Pharmacy, Hefei Cancer Hospital, Chinese Academy of Sciences, Hefei 230031, Anhui China
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3
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Calcinelli F, Jeindl A, Hörmann L, Ghan S, Oberhofer H, Hofmann OT. Interfacial Charge Transfer Influences Thin-Film Polymorphism. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2022; 126:2868-2876. [PMID: 35178141 PMCID: PMC8842301 DOI: 10.1021/acs.jpcc.1c09986] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 01/12/2022] [Indexed: 05/05/2023]
Abstract
The structure and chemical composition are the key parameters influencing the properties of organic thin films deposited on inorganic substrates. Such films often display structures that substantially differ from the bulk, and the substrate has a relevant influence on their polymorphism. In this work, we illuminate the role of the substrate by studying its influence on para-benzoquinone on two different substrates, Ag(111) and graphene. We employ a combination of first-principles calculations and machine learning to identify the energetically most favorable structures on both substrates and study their electronic properties. Our results indicate that for the first layer, similar structures are favorable for both substrates. For the second layer, we find two significantly different structures. Interestingly, graphene favors the one with less, while Ag favors the one with more electronic coupling. We explain this switch in stability as an effect of the different charge transfer on the two substrates.
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Affiliation(s)
- Fabio Calcinelli
- Institute
of Solid State Physics, Graz University
of Technology, 8010 Graz, Austria
| | - Andreas Jeindl
- Institute
of Solid State Physics, Graz University
of Technology, 8010 Graz, Austria
| | - Lukas Hörmann
- Institute
of Solid State Physics, Graz University
of Technology, 8010 Graz, Austria
| | - Simiam Ghan
- Chair
for Theoretical Chemistry and Catalysis Research Center, Technical University Munich, 85748 Garching, Germany
| | - Harald Oberhofer
- Chair
for Theoretical Chemistry and Catalysis Research Center, Technical University Munich, 85748 Garching, Germany
- Chair
for Theoretical Physics VII and Bavarian Center for Battery Technology
(BayBatt), University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
| | - Oliver T. Hofmann
- Institute
of Solid State Physics, Graz University
of Technology, 8010 Graz, Austria
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4
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Werkovits A, Jeindl A, Hörmann L, Cartus JJ, Hofmann OT. Toward Targeted Kinetic Trapping of Organic–Inorganic Interfaces: A Computational Case Study. ACS PHYSICAL CHEMISTRY AU 2022; 2:38-46. [PMID: 35098244 PMCID: PMC8796281 DOI: 10.1021/acsphyschemau.1c00015] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 09/21/2021] [Accepted: 09/23/2021] [Indexed: 11/29/2022]
Abstract
![]()
Properties of inorganic–organic interfaces, such as their
interface dipole, strongly depend on the structural arrangements of
the organic molecules. A prime example is tetracyanoethylene (TCNE)
on Cu(111), which shows two different phases with significantly different
work functions. However, the thermodynamically preferred phase is
not always the one that is best suited for a given application. Rather,
it may be desirable to selectively grow a kinetically trapped structure.
In this work, we employ density functional theory and transition state
theory to discuss under which conditions such a kinetic trapping might
be possible for the model system of TCNE on Cu. Specifically, we want
to trap the molecules in the first layer in a flat-lying orientation.
This requires temperatures that are sufficiently low to suppress the
reorientation of the molecules, which is thermodynamically more favorable
for high dosages, but still high enough to enable ordered growth through
diffusion of molecules. On the basis of the temperature-dependent
diffusion and reorientation rates, we propose a temperature range
at which the reorientation can be successfully suppressed.
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Affiliation(s)
- Anna Werkovits
- Institute of Solid State Physics, TU Graz, NAWI Graz, Petersgasse 16/II, 8010 Graz, Austria
| | - Andreas Jeindl
- Institute of Solid State Physics, TU Graz, NAWI Graz, Petersgasse 16/II, 8010 Graz, Austria
| | - Lukas Hörmann
- Institute of Solid State Physics, TU Graz, NAWI Graz, Petersgasse 16/II, 8010 Graz, Austria
| | - Johannes J. Cartus
- Institute of Solid State Physics, TU Graz, NAWI Graz, Petersgasse 16/II, 8010 Graz, Austria
| | - Oliver T. Hofmann
- Institute of Solid State Physics, TU Graz, NAWI Graz, Petersgasse 16/II, 8010 Graz, Austria
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5
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Cartus J, Jeindl A, Hofmann OT. Can We Predict Interface Dipoles Based on Molecular Properties? ACS OMEGA 2021; 6:32270-32276. [PMID: 34870047 PMCID: PMC8638305 DOI: 10.1021/acsomega.1c05092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Accepted: 11/02/2021] [Indexed: 05/12/2023]
Abstract
We apply high-throughput density functional theory calculations and symbolic regression to hybrid inorganic/organic interfaces with the intent to extract physically meaningful correlations between the adsorption-induced work function modifications and the properties of the constituents. We separately investigate two cases: (1) hypothetical, free-standing self-assembled monolayers with a large intrinsic dipole moment and (2) metal-organic interfaces with a large charge-transfer-induced dipole. For the former, we find, without notable prior assumptions, the Topping model, as expected from the literature. For the latter, highly accurate correlations are found, which are, however, clearly unphysical.
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6
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Hofmann OT, Zojer E, Hörmann L, Jeindl A, Maurer RJ. First-principles calculations of hybrid inorganic-organic interfaces: from state-of-the-art to best practice. Phys Chem Chem Phys 2021; 23:8132-8180. [PMID: 33875987 PMCID: PMC8237233 DOI: 10.1039/d0cp06605b] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 03/05/2021] [Indexed: 12/18/2022]
Abstract
The computational characterization of inorganic-organic hybrid interfaces is arguably one of the technically most challenging applications of density functional theory. Due to the fundamentally different electronic properties of the inorganic and the organic components of a hybrid interface, the proper choice of the electronic structure method, of the algorithms to solve these methods, and of the parameters that enter these algorithms is highly non-trivial. In fact, computational choices that work well for one of the components often perform poorly for the other. As a consequence, default settings for one materials class are typically inadequate for the hybrid system, which makes calculations employing such settings inefficient and sometimes even prone to erroneous results. To address this issue, we discuss how to choose appropriate atomistic representations for the system under investigation, we highlight the role of the exchange-correlation functional and the van der Waals correction employed in the calculation and we provide tips and tricks how to efficiently converge the self-consistent field cycle and to obtain accurate geometries. We particularly focus on potentially unexpected pitfalls and the errors they incur. As a summary, we provide a list of best practice rules for interface simulations that should especially serve as a useful starting point for less experienced users and newcomers to the field.
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Affiliation(s)
- Oliver T Hofmann
- Institute of Solid State Physics, Graz University of Technology, NAWI Graz, Petersgasse 16/II, 8010 Graz, Austria.
| | - Egbert Zojer
- Institute of Solid State Physics, Graz University of Technology, NAWI Graz, Petersgasse 16/II, 8010 Graz, Austria.
| | - Lukas Hörmann
- Institute of Solid State Physics, Graz University of Technology, NAWI Graz, Petersgasse 16/II, 8010 Graz, Austria.
| | - Andreas Jeindl
- Institute of Solid State Physics, Graz University of Technology, NAWI Graz, Petersgasse 16/II, 8010 Graz, Austria.
| | - Reinhard J Maurer
- Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK
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7
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Taucher T, Hofmann OT, Zojer E. Final-State Simulations of Core-Level Binding Energies at Metal-Organic Hybrid Interfaces: Artifacts Caused by Spurious Collective Electrostatic Effects. ACS OMEGA 2020; 5:25868-25881. [PMID: 33073112 PMCID: PMC7557941 DOI: 10.1021/acsomega.0c03209] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Accepted: 09/14/2020] [Indexed: 05/08/2023]
Abstract
Core-level energies are frequently calculated to explain the X-ray photoelectron spectra of metal-organic hybrid interfaces. The current paper describes how such simulations can be flawed when modeling interfaces between physisorbed organic molecules and metals. The problem occurs when applying periodic boundary conditions to correctly describe extended interfaces and simultaneously considering core hole excitations in the framework of a final-state approach to account for screening effects. Since the core hole is generated in every unit cell, an artificial dipole layer is formed. In this work, we study methane on an Al(100) surface as a deliberately chosen model system for hybrid interfaces to evaluate the impact of this computational artifact. We show that changing the supercell size leads to artificial shifts in the calculated core-level energies that can be well beyond 1 eV for small cells. The same applies to atoms at comparably large distances from the substrate, encountered, for example, in extended, upright-standing adsorbate molecules. We also argue that the calculated work function change due to a core-level excitation can serve as an indication for the occurrence of such an artifact and discuss possible remedies for the problem.
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8
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Niederhausen J, MacQueen RW, Lips K, Aldahhak H, Schmidt WG, Gerstmann U. Tetracene Ultrathin Film Growth on Hydrogen-Passivated Silicon. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:9099-9113. [PMID: 32659091 DOI: 10.1021/acs.langmuir.0c01154] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Inorganic-organic interfaces are important for enhancing the power conversion efficiency of silicon-based solar cells through singlet exciton fission (SF). We elucidated the structure of the first monolayers of tetracene (Tc), an SF molecule, on hydrogen-passivated Si(111) [H-Si(111)] and hydrogenated amorphous Si (a-Si:H) by combining near-edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy (XPS) experiments with density functional theory (DFT) calculations. For samples grown at or below substrate temperatures of 265 K, the resulting ultrathin Tc films are dominated by almost upright-standing molecules. The molecular arrangement is very similar to the Tc bulk phase, with only a slightly higher average angle between the conjugated molecular plane normal and the surface normal (α) around 77°. Judging from carbon K-edge X-ray absorption spectra, the orientation of the Tc molecules are almost identical when grown on H-Si(111) and a-Si:H substrates as well as for (sub)mono- to several-monolayer coverages. Annealing to room temperature, however, changes the film structure toward a smaller α of about 63°. A detailed DFT-assisted analysis suggests that this structural transition is correlated with a lower packing density and requires a well-chosen amount of thermal energy. Therefore, we attribute the resulting structure to a distinct monolayer configuration that features less inclined, but still well-ordered molecules. The larger overlap with the substrate wave functions makes this arrangement attractive for an optimized interfacial electron transfer in SF-assisted silicon solar cells.
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Affiliation(s)
- Jens Niederhausen
- Department ASPIN, Helmholtz-Zentrum Berlin für Materialen und Energie GmbH, Berlin, Germany
| | - Rowan W MacQueen
- Department ASPIN, Helmholtz-Zentrum Berlin für Materialen und Energie GmbH, Berlin, Germany
| | - Klaus Lips
- Department ASPIN, Helmholtz-Zentrum Berlin für Materialen und Energie GmbH, Berlin, Germany
| | - Hazem Aldahhak
- Lehrstuhl für Theoretische Materialphysik, Universität Paderborn, 33095 Paderborn, Germany
| | - Wolf Gero Schmidt
- Lehrstuhl für Theoretische Materialphysik, Universität Paderborn, 33095 Paderborn, Germany
| | - Uwe Gerstmann
- Lehrstuhl für Theoretische Materialphysik, Universität Paderborn, 33095 Paderborn, Germany
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9
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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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10
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Schöttner L, Erker S, Schlesinger R, Koch N, Nefedov A, Hofmann OT, Wöll C. Doping-Induced Electron Transfer at Organic/Oxide Interfaces: Direct Evidence from Infrared Spectroscopy. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2020; 124:4511-4516. [PMID: 32140201 PMCID: PMC7050012 DOI: 10.1021/acs.jpcc.9b08768] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Revised: 01/27/2020] [Indexed: 06/10/2023]
Abstract
Charge transfer at organic/inorganic interfaces critically influences the properties of molecular adlayers. Although for metals such charge transfers are well documented by experimental and theoretical results, in the case of semiconductors, clear and direct evidence for a transfer of electrons or holes from oxides with their typically high ionization energy is missing. Here, we present data from infrared reflection-absorption spectroscopy demonstrating that despite a high ionization energy, electrons are transferred from ZnO into a prototype strong molecular electron acceptor, hexafluoro-tetracyano-naphthoquinodimethane (F6-TCNNQ). Because there are no previous studies of this type, the interpretation of the pronounced vibrational red shifts observed in the experiment was aided by a thorough theoretical analysis using density functional theory. The calculations reveal that two mechanisms govern the pronounced vibrational band shifts of the adsorbed molecules: electron transfer into unoccupied molecular levels of the organic acceptor and also the bonding between the surface Zn atoms and the peripheral cyano groups. These combined experimental data and the theoretical analysis provide the so-far missing evidence of interfacial electron transfer from high ionization energy inorganic semiconductors to molecular acceptors and indicates that n-doping of ZnO plays a crucial role.
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Affiliation(s)
- L. Schöttner
- Karlsruhe
Institute of Technology, Institute of Functional
Interfaces, Hermann-von-Helmholtz-Platz
1, 76344 Eggenstein-Leopoldshafen, Germany
| | - S. Erker
- Graz
University of Technology, NAWI Graz, Petersgasse 16, 8010 Graz, Austria
| | - R. Schlesinger
- Humboldt
Universität zu Berlin, Institut für
Physik & IRIS Adlershof, Brook-Taylor-Straße 6, 12489 Berlin, Germany
| | - N. Koch
- Humboldt
Universität zu Berlin, Institut für
Physik & IRIS Adlershof, Brook-Taylor-Straße 6, 12489 Berlin, Germany
| | - A. Nefedov
- Karlsruhe
Institute of Technology, Institute of Functional
Interfaces, Hermann-von-Helmholtz-Platz
1, 76344 Eggenstein-Leopoldshafen, Germany
| | - O. T. Hofmann
- Graz
University of Technology, NAWI Graz, Petersgasse 16, 8010 Graz, Austria
| | - C. Wöll
- Karlsruhe
Institute of Technology, Institute of Functional
Interfaces, Hermann-von-Helmholtz-Platz
1, 76344 Eggenstein-Leopoldshafen, Germany
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11
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Chen MT, Hofmann OT, Gerlach A, Bröker B, Bürker C, Niederhausen J, Hosokai T, Zegenhagen J, Vollmer A, Rieger R, Müllen K, Schreiber F, Salzmann I, Koch N, Zojer E, Duhm S. Energy-level alignment at strongly coupled organic-metal interfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:194002. [PMID: 30673641 DOI: 10.1088/1361-648x/ab0171] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Energy-level alignment at organic-metal interfaces plays a crucial role for the performance of organic electronic devices. However, reliable models to predict energetics at strongly coupled interfaces are still lacking. We elucidate contact formation of 1,2,5,6,9,10-coronenehexone (COHON) to the (1 1 1)-surfaces of coinage metals by means of ultraviolet photoelectron spectroscopy, x-ray photoelectron spectroscopy, the x-ray standing wave technique, and density functional theory calculations. While for low COHON thicknesses, the work-functions of the systems vary considerably, for thicker organic films Fermi-level pinning leads to identical work functions of 5.2 eV for all COHON-covered metals irrespective of the pristine substrate work function and the interfacial interaction strength.
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Affiliation(s)
- Meng-Ting Chen
- Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices and Joint International Research Laboratory of Carbon-Based Functional Materials and Devices, Soochow University, 199 Ren-Ai Road, Suzhou 215123, People's Republic of China
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12
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Schlesinger R, Winkler S, Brandt M, Blumstengel S, Ovsyannikov R, Vollmer A, Koch N. Energy level alignment at organic/inorganic semiconductor heterojunctions: Fermi level pinning at the molecular interlayer with a reduced energy gap. Phys Chem Chem Phys 2019; 21:15072-15079. [DOI: 10.1039/c9cp02763g] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
A lying (L) molecular interlayer between ZnO and standing (S) sexiphenyl molecules leads to “concealed” Fermi level pinning.
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Affiliation(s)
- Raphael Schlesinger
- Humboldt-Universität zu Berlin
- Institut für Physik & IRIS Adlershof
- 12489 Berlin
- Germany
| | - Stefanie Winkler
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH- BESSY II
- 12489 Berlin
- Germany
| | - Matthias Brandt
- Humboldt-Universität zu Berlin
- Institut für Physik & IRIS Adlershof
- 12489 Berlin
- Germany
| | - Sylke Blumstengel
- Humboldt-Universität zu Berlin
- Institut für Physik & IRIS Adlershof
- 12489 Berlin
- Germany
| | - Ruslan Ovsyannikov
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH- BESSY II
- 12489 Berlin
- Germany
| | - Antje Vollmer
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH- BESSY II
- 12489 Berlin
- Germany
| | - Norbert Koch
- Humboldt-Universität zu Berlin
- Institut für Physik & IRIS Adlershof
- 12489 Berlin
- Germany
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH- BESSY II
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13
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Lach S, Altenhof A, Shi S, Fahlman M, Ziegler C. Electronic and magnetic properties of a ferromagnetic cobalt surface by adsorbing ultrathin films of tetracyanoethylene. Phys Chem Chem Phys 2019; 21:15833-15844. [PMID: 31282504 DOI: 10.1039/c9cp02205h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Ultrathin films of tetracyanoethylene (TCNE) on Co(100) were investigated by means of spin-integrated and spin-resolved photoemission spectroscopy ((sp-)UPS), X-ray photoemission spectroscopy (XPS), near edge X-ray absorption fine-structure spectroscopy (NEXAFS), and X-ray magnetic circular dichroism (XMCD). We found a coverage-dependent modulation of the interface dipole and a switching between a metallic and a resistive spin filtering at the interface triggered by two distinct adsorption geometries of TCNE. The strongest hybridization and spin structure modifications are found at low coverage with a face-on adsorption geometry indicating changes in the distance between the surface Co atoms beneath. TCNE has the potential to manipulate the magnetic moments in the Co surface itself, including the possibility of magnetic hardening effects. In summary, the system TCNE/Co offers an experimentally rather easy and controllable way to build up a stable molecular platform stabilizing the reactive ferromagnetic Co surface and customizing the electronic and magnetic properties of the resulting spinterface simultaneously. This makes this system very attractive for spintronic applications as an alternative, less reactive but highly spin polarized foundation beside graphene-based systems.
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Affiliation(s)
- Stefan Lach
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Kaiserslautern, 67663 Kaiserslautern, Germany.
| | - Anna Altenhof
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Kaiserslautern, 67663 Kaiserslautern, Germany.
| | - Shengwei Shi
- Hubei Key Laboratory of Plasma Chemistry and Advanced Materials, School of Materials Science and Engineering, Wuhan Institute of Technology, Wuhan, 430205 Wuhan, China and Department of Physics, Chemistry and Biology, University of Linköping, Linköping, 58183 Linköping, Sweden
| | - Mats Fahlman
- Department of Physics, Chemistry and Biology, University of Linköping, Linköping, 58183 Linköping, Sweden
| | - Christiane Ziegler
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Kaiserslautern, 67663 Kaiserslautern, Germany.
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14
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Hofmann OT, Glowatzki H, Bürker C, Rangger GM, Bröker B, Niederhausen J, Hosokai T, Salzmann I, Blum RP, Rieger R, Vollmer A, Rajput P, Gerlach A, Müllen K, Schreiber F, Zojer E, Koch N, Duhm S. Orientation-Dependent Work-Function Modification Using Substituted Pyrene-Based Acceptors. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2017; 121:24657-24668. [PMID: 29152034 PMCID: PMC5682610 DOI: 10.1021/acs.jpcc.7b08451] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Revised: 10/10/2017] [Indexed: 05/17/2023]
Abstract
The adsorption of molecular acceptors is a viable method for tuning the work function of metal electrodes. This, in turn, enables adjusting charge injection barriers between the electrode and organic semiconductors. Here, we demonstrate the potential of pyrene-tetraone (PyT) and its derivatives dibromopyrene-tetraone (Br-PyT) and dinitropyrene-tetraone (NO2-PyT) for modifying the electronic properties of Au(111) and Ag(111) surfaces. The systems are investigated by complementary theoretical and experimental approaches, including photoelectron spectroscopy, the X-ray standing wave technique, and density functional theory simulations. For some of the investigated interfaces the trends expected for Fermi-level pinning are observed, i.e., an increase of the metal work function along with increasing molecular electron affinity and the same work function for Au and Ag with monolayer acceptor coverage. Substantial deviations are, however, found for Br-PyT/Ag(111) and NO2-PyT/Ag(111), where in the latter case an adsorption-induced work function increase of as much as 1.6 eV is observed. This behavior is explained as arising from a face-on to edge-on reorientation of molecules in the monolayer. Our calculations show that for an edge-on orientation much larger work-function changes can be expected despite the prevalence of Fermi-level pinning. This is primarily ascribed to a change of the electron affinity of the adsorbate layer that results from a change of the molecular orientation. This work provides a comprehensive understanding of how changing the molecular electron affinity as well as the adsorbate structure impacts the electronic properties of electrodes.
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Affiliation(s)
- O. T. Hofmann
- Institute
of Solid State Physics, NAWI Graz, Graz
University of Technology, Petersgasse 16, 8010 Graz, Austria
- E-mail:
| | - H. Glowatzki
- Helmholtz-Zentrum
Berlin für Materialien und Energie GmbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany
| | - C. Bürker
- Institut
für Angewandte Physik, Universität
Tübingen, Auf
der Morgenstelle 10, Tübingen 72076, Germany
| | - G. M. Rangger
- Institute
of Solid State Physics, NAWI Graz, Graz
University of Technology, Petersgasse 16, 8010 Graz, Austria
| | - B. Bröker
- Institut
für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, Newtonstraße 15, 12389 Berlin, Germany
| | - J. Niederhausen
- Helmholtz-Zentrum
Berlin für Materialien und Energie GmbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany
| | - T. Hosokai
- National
Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan
| | - I. Salzmann
- Institut
für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, Newtonstraße 15, 12389 Berlin, Germany
- The
Institute of Solid State Physics, The University
of Tokyo, Kashiwanoha
5-1-5, Kashiwa, Chiba 277-8581, Japan
| | - R.-P. Blum
- Institut
für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, Newtonstraße 15, 12389 Berlin, Germany
| | - R. Rieger
- Max Planck
Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany
| | - A. Vollmer
- Helmholtz-Zentrum
Berlin für Materialien und Energie GmbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany
| | - P. Rajput
- Atomic
& Molecular Physics Division, Bhabha
Atomic Research Centre, Trombay, Mumbai 400085, India
| | - A. Gerlach
- Institut
für Angewandte Physik, Universität
Tübingen, Auf
der Morgenstelle 10, Tübingen 72076, Germany
| | - K. Müllen
- Max Planck
Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany
- Institute
of Physical Chemistry, Johannes Gutenberg
University Mainz, Duesbergweg
10-14, Mainz, Germany
| | - F. Schreiber
- Institut
für Angewandte Physik, Universität
Tübingen, Auf
der Morgenstelle 10, Tübingen 72076, Germany
| | - E. Zojer
- Institute
of Solid State Physics, NAWI Graz, Graz
University of Technology, Petersgasse 16, 8010 Graz, Austria
| | - N. Koch
- Helmholtz-Zentrum
Berlin für Materialien und Energie GmbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany
- Institut
für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, Newtonstraße 15, 12389 Berlin, Germany
- Jiangsu
Key Laboratory for Carbon-Based Functional Materials & Devices
and Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, 199 Ren-Ai Road, Suzhou 215123, P.R. China
| | - S. Duhm
- Jiangsu
Key Laboratory for Carbon-Based Functional Materials & Devices
and Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, 199 Ren-Ai Road, Suzhou 215123, P.R. China
- E-mail:
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15
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Ohisa S, Pu YJ, Takahashi S, Chiba T, Kido J. Inhibition of solution-processed 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile crystallization by mixing additives for hole injection layers in organic light-emitting devices. Polym J 2016. [DOI: 10.1038/pj.2016.92] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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16
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Goiri E, Borghetti P, El-Sayed A, Ortega JE, de Oteyza DG. Multi-Component Organic Layers on Metal Substrates. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2016; 28:1340-1368. [PMID: 26662076 DOI: 10.1002/adma.201503570] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Revised: 08/31/2015] [Indexed: 05/28/2023]
Abstract
Increasingly high hopes are being placed on organic semiconductors for a variety of applications. Progress along these lines, however, requires the design and growth of increasingly complex systems with well-defined structural and electronic properties. These issues have been studied and reviewed extensively in single-component layers, but the focus is gradually shifting towards more complex and functional multi-component assemblies such as donor-acceptor networks. These blends show different properties from those of the corresponding single-component layers, and the understanding on how these properties depend on the different supramolecular environment of multi-component assemblies is crucial for the advancement of organic devices. Here, our understanding of two-dimensional multi-component layers on solid substrates is reviewed. Regarding the structure, the driving forces behind the self-assembly of these systems are described. Regarding the electronic properties, recent insights into how these are affected as the molecule's supramolecular environment changes are explained. Key information for the design and controlled growth of complex, functional multicomponent structures by self-assembly is summarized.
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Affiliation(s)
- Elizabeth Goiri
- Donostia International Physics Center, E-20018, Paseo Manuel Lardizabal 4, Donostia-San Sebastián, Spain
- Centro de Fisica de Materiales CSIC/UPV-EHU-Materials Physics Center, E-20018, Donostia-San Sebastián, Spain
| | - Patrizia Borghetti
- Donostia International Physics Center, E-20018, Paseo Manuel Lardizabal 4, Donostia-San Sebastián, Spain
- Centro de Fisica de Materiales CSIC/UPV-EHU-Materials Physics Center, E-20018, Donostia-San Sebastián, Spain
- Institut des NanoSciences de Paris, CNRS, UMR 7588, 4 Place Jussieu, Paris, 75005, France
| | - Afaf El-Sayed
- Centro de Fisica de Materiales CSIC/UPV-EHU-Materials Physics Center, E-20018, Donostia-San Sebastián, Spain
- Physics Dept., Faculty of Science, Al-Azhar University, 11754, Cairo, Egypt
| | - J Enrique Ortega
- Donostia International Physics Center, E-20018, Paseo Manuel Lardizabal 4, Donostia-San Sebastián, Spain
- Centro de Fisica de Materiales CSIC/UPV-EHU-Materials Physics Center, E-20018, Donostia-San Sebastián, Spain
- Universidad del Pais Vasco, Dpto. de Física Aplicada I, E-20018, Donostia-San Sebastián, Spain
| | - Dimas G de Oteyza
- Donostia International Physics Center, E-20018, Paseo Manuel Lardizabal 4, Donostia-San Sebastián, Spain
- Centro de Fisica de Materiales CSIC/UPV-EHU-Materials Physics Center, E-20018, Donostia-San Sebastián, Spain
- Ikerbasque, Basque Foundation for Science, E-48011, Bilbao, Spain
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17
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Liu Y, Zhang ZG, Xia Z, Zhang J, Liu Y, Liang F, Li Y, Song T, Yu X, Lee ST, Sun B. High Performance Nanostructured Silicon-Organic Quasi p-n Junction Solar Cells via Low-Temperature Deposited Hole and Electron Selective Layer. ACS NANO 2016; 10:704-12. [PMID: 26695703 DOI: 10.1021/acsnano.5b05732] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
UNLABELLED Silicon-organic solar cells based on conjugated polymers such as poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) ( PEDOT PSS) on n-type silicon (n-Si) attract wide interest because of their potential for cost-effectiveness and high-efficiency. However, a lower barrier height (Φb) and a shallow built in potential (Vbi) of Schottky junction between n-Si and PEDOT PSS hinders the power conversion efficiency (PCE) in comparison with those of traditional p-n junction. Here, a strong inversion layer was formed on n-Si surface by inserting a layer of 1, 4, 5, 8, 9, 11-hexaazatriphenylene hexacarbonitrile (HAT-CN), resulting in a quasi p-n junction. External quantum efficiency spectra, capacitance-voltage, transient photovoltage decay and minority charge carriers life mapping measurements indicated that a quasi p-n junction was built due to the strong inversion effect, resulting in a high Φb and Vbi. The quasi p-n junction located on the front surface region of silicon substrates improved the short wavelength light conversion into photocurrent. In addition, a derivative perylene diimide (PDIN) layer between rear side of silicon and aluminum cathodes was used to block the holes from flowing to cathodes. As a result, the device with PDIN layer also improved photoresponse at longer wavelength. A champion PCE of 14.14% was achieved for the nanostructured silicon-organic device by combining HAT-CN and PDIN layers. The low temperature and simple device structure with quasi p-n junction promises cost-effective high performance photovoltaic techniques.
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Affiliation(s)
- Yuqiang Liu
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University , Suzhou 215123, China
| | - Zhi-Guo Zhang
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, China
| | - Zhouhui Xia
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University , Suzhou 215123, China
| | - Jie Zhang
- Department of Electronic Engineering, The Chinese University of Hong Kong , New Territories, Hong Kong, China
| | - Yuan Liu
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University , Suzhou 215123, China
| | - Feng Liang
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University , Suzhou 215123, China
| | - Yongfang Li
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, China
| | - Tao Song
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University , Suzhou 215123, China
| | - Xuegong Yu
- State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University , Hangzhou 310027, China
| | - Shuit-Tong Lee
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University , Suzhou 215123, China
| | - Baoquan Sun
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University , Suzhou 215123, China
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18
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Edlbauer H, Zojer E, Hofmann OT. Postadsorption Work Function Tuning via Hydrogen Pressure Control. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2015; 119:27162-27172. [PMID: 26692915 PMCID: PMC4671103 DOI: 10.1021/acs.jpcc.5b08827] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Revised: 11/06/2015] [Indexed: 05/24/2023]
Abstract
The work function of metal substrates can be easily tuned, for instance, by adsorbing layers of molecular electron donors and acceptors. In this work, we discuss the possibility of changing the donor/acceptor mixing ratio reversibly after adsorption by choosing a donor/acceptor pair that is coupled via a redox reaction and that is in equilibrium with a surrounding gas phase. We discuss such a situation for the example of tetrafluoro-1,4-benzenediol (TFBD)/tetrafluoro-1,4-benzoquinone (TFBQ), adsorbed on Cu(111) and Ag(111) surfaces. We use density functional theory and ab initio thermodynamics to show that arbitrary TFBD/TFBQ mixing ratios can be set using hydrogen pressures attainable in low to ultrahigh vacuum. Adjusting the mixing ratio allows modifying the work function over a range of about 1 eV. Finally, we contrast single-species submonolayers with mixed layers to discuss why the resulting inhomogeneities in the electrostatic energy above the surface have different impacts on the interfacial level alignment and the work function.
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19
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Verzijl CJO, Celis Gil JA, Perrin ML, Dulić D, van der Zant HSJ, Thijssen JM. Image effects in transport at metal-molecule interfaces. J Chem Phys 2015; 143:174106. [DOI: 10.1063/1.4934882] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- C. J. O. Verzijl
- Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft, The Netherlands
| | - J. A. Celis Gil
- Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft, The Netherlands
| | - M. L. Perrin
- Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft, The Netherlands
| | - D. Dulić
- Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Santiago de Chile, Chile
| | - H. S. J. van der Zant
- Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft, The Netherlands
| | - J. M. Thijssen
- Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft, The Netherlands
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20
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Winkler A. Initial stages of organic film growth characterized by thermal desorption spectroscopy. SURFACE SCIENCE 2015; 643:124-137. [PMID: 26778860 PMCID: PMC4712358 DOI: 10.1016/j.susc.2015.06.022] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
In the wake of the increasing importance of organic electronics, a more in-depth understanding of the early stages of organic film growth is indispensable. In this review a survey of several rod-like and plate-like organic molecules (p-quaterphenyl, p-sexiphenyl, hexaazatriphenylene-hexacarbonitrile (HATCN), rubicene, indigo) deposited on various application relevant substrates (gold, silver, mica, silicon dioxide) is given. The focus is particularly put on the application of thermal desorption spectroscopy to shed light on the kinetics and energetics of the molecule-substrate interaction. While each adsorption system reveals a manifold of features that are specific for the individual system, one can draw some general statements on the early stages of organic film formation from the available datasets. Among the important issues in this context is the formation of wetting layers and the dewetting as a function of the substrate surface conditions, organic film thickness and temperature.
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Affiliation(s)
- Adolf Winkler
- Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
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21
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Huang YL, Wruss E, Egger DA, Kera S, Ueno N, Saidi WA, Bucko T, Wee ATS, Zojer E. Understanding the adsorption of CuPc and ZnPc on noble metal surfaces by combining quantum-mechanical modelling and photoelectron spectroscopy. Molecules 2014; 19:2969-92. [PMID: 24609018 PMCID: PMC6271497 DOI: 10.3390/molecules19032969] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Revised: 02/24/2014] [Accepted: 02/26/2014] [Indexed: 11/16/2022] Open
Abstract
Phthalocyanines are an important class of organic semiconductors and, thus, their interfaces with metals are both of fundamental and practical relevance. In the present contribution we provide a combined theoretical and experimental study, in which we show that state-of-the-art quantum-mechanical simulations are nowadays capable of treating most properties of such interfaces in a quantitatively reliable manner. This is shown for Cu-phthalocyanine (CuPc) and Zn-phthalocyanine (ZnPc) on Au(111) and Ag(111) surfaces. Using a recently developed approach for efficiently treating van der Waals (vdW) interactions at metal/organic interfaces, we calculate adsorption geometries in excellent agreement with experiments. With these geometries available, we are then able to accurately describe the interfacial electronic structure arising from molecular adsorption. We find that bonding is dominated by vdW forces for all studied interfaces. Concomitantly, charge rearrangements on Au(111) are exclusively due to Pauli pushback. On Ag(111), we additionally observe charge transfer from the metal to one of the spin-channels associated with the lowest unoccupied π-states of the molecules. Comparing the interfacial density of states with our ultraviolet photoelectron spectroscopy (UPS) experiments, we find that the use of a hybrid functionals is necessary to obtain the correct order of the electronic states.
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Affiliation(s)
- Yu Li Huang
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117542, Singapore.
| | - Elisabeth Wruss
- Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria.
| | - David A Egger
- Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria.
| | - Satoshi Kera
- Graduate School of Advanced Integration Science, Chiba University, 1- 33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
| | - Nobuo Ueno
- Graduate School of Advanced Integration Science, Chiba University, 1- 33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
| | - Wissam A Saidi
- Department of Chemical and Petroleum Engineering, University of Pittsburgh, 1249 Benedum Hall, Pittsburgh, PA 15261, USA.
| | - Tomas Bucko
- Department of Physical and Theoretical Chemistry, Faculty of Natural Sciences, Comenius University, Mlynska Dolina, SK-84215 Bratislava, Slovakia.
| | - Andrew T S Wee
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117542, Singapore.
| | - Egbert Zojer
- Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria.
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22
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Perrin ML, Verzijl CJO, Martin CA, Shaikh AJ, Eelkema R, van Esch JH, van Ruitenbeek JM, Thijssen JM, van der Zant HSJ, Dulić D. Large tunable image-charge effects in single-molecule junctions. NATURE NANOTECHNOLOGY 2013; 8:282-7. [PMID: 23503093 DOI: 10.1038/nnano.2013.26] [Citation(s) in RCA: 152] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Accepted: 02/01/2013] [Indexed: 05/04/2023]
Abstract
Metal/organic interfaces critically determine the characteristics of molecular electronic devices, because they influence the arrangement of the orbital levels that participate in charge transport. Studies on self-assembled monolayers show molecule-dependent energy-level shifts as well as transport-gap renormalization, two effects that suggest that electric-field polarization in the metal substrate induced by the formation of image charges plays a key role in the alignment of the molecular energy levels with respect to the metal's Fermi energy. Here, we provide direct experimental evidence for an electrode-induced gap renormalization in single-molecule junctions. We study charge transport through single porphyrin-type molecules using electrically gateable break junctions. In this set-up, the position of the occupied and unoccupied molecular energy levels can be followed in situ under simultaneous mechanical control. When increasing the electrode separation by just a few ångströms, we observe a substantial increase in the transport gap and level shifts as high as several hundreds of meV. Analysis of this large and tunable gap renormalization based on atomic charges obtained from density functional theory confirms and clarifies the dominant role of image-charge effects in single-molecule junctions.
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Affiliation(s)
- Mickael L Perrin
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
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23
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Sun LD, Gall J, Weidlinger G, Liu CY, Denk M, Zeppenfeld P. Azimuthal reorientation of pentacene upon 2D condensation. PHYSICAL REVIEW LETTERS 2013; 110:106101. [PMID: 23521273 DOI: 10.1103/physrevlett.110.106101] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2012] [Revised: 12/20/2012] [Indexed: 05/24/2023]
Abstract
We report a novel two-dimensional gas-solid phase transition of pentacene molecules on the Cu(110)-(2 × 1)O surface where the 2D condensation is accompanied by a reversible azimuthal rotation of the pentacene molecules. The change of the optical anisotropy associated with this reorientation allows us to explore the 2D condensation as a function of coverage and temperature by reflectance difference spectroscopy. As a result, the 2D heat of condensation of pentacene on Cu(110)-(2 × 1)O is determined to be 84 meV, which is more than one order of magnitude smaller than the respective value for 3D crystallization.
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Affiliation(s)
- L D Sun
- Institute of Experimental Physics, Johannes Kepler University Linz, Altenbergerstrasse 69, A-4040 Linz, Austria.
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24
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Gengler RYN, Gournis D, Aimon AH, Toma LM, Rudolf P. The Molecularly Controlled Synthesis of Ordered Bi-dimensional C60Arrays. Chemistry 2012; 18:7594-600. [DOI: 10.1002/chem.201103528] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Revised: 02/10/2012] [Indexed: 11/08/2022]
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