51
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Ai Y, Lacroix JC. Self-terminated fabrication of electrochemically-gated conducting polymer nanojunctions. Electrochem commun 2020. [DOI: 10.1016/j.elecom.2020.106674] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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52
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Karuppannan S, Neoh EHL, Vilan A, Nijhuis CA. Protective Layers Based on Carbon Paint To Yield High-Quality Large-Area Molecular Junctions with Low Contact Resistance. J Am Chem Soc 2020; 142:3513-3524. [PMID: 31951129 PMCID: PMC7307901 DOI: 10.1021/jacs.9b12424] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Indexed: 12/20/2022]
Abstract
A major obstacle for transforming large-area molecular junctions into a viable technology is the deposition of a top, metallic contact over the self-assembled monolayer (SAM) without chemically damaging the molecules and preventing an interface-limited charge transport. Often a thin conducting layer is softly deposited over the SAM to protect it during the deposition of the metal electrode which requires conditions under which organic molecules are not stable. We report a new protective layer based on carbon paint which is highly conductive and has metallic-like behavior. Junctions made of SAMs of n-alkanethiolates supported by Au were characterized with both dc and ac techniques, revealing that carbon paint protective layers provide a solution to three well-known challenges in molecular junctions: series resistance of the leads, poor interface conductance, and low effective contact area related to the roughness of the interfaces. Transport is constant with coherent tunneling down to 10 K, indicating the carbon paint does not add spurious thermally activated components. The junctions have both high reproducibility and good stability against bias stressing. Finally, normalized differential conductance analysis of the tunneling characteristics of the junctions as a function of molecular length reveals that the scaling voltage changes with molecular length, indicating a significant voltage drop on the molecules rather than on the molecule-electrode interface. There is a clear inverse dependence of the scaling voltage on length, which we deduced has a tunneling barrier height of close to 2 eV. The paper establishes the reliability of carbon paint protective layers and provides a procedure for discriminating genuine molecular effects from interfacial contributions.
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Affiliation(s)
- Senthil
Kumar Karuppannan
- Department
of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Esther Hui Lin Neoh
- Department
of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Ayelet Vilan
- Department
of Chemical and Biological Physics, Weizmann
Institute of Science, Rehovot 76100, Israel
| | - Christian A. Nijhuis
- Department
of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
- Centre
for Advanced 2D Materials, National University
of Singapore, 6 Science Drive 2, Singapore 117546, Singapore
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53
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Herrmann C. Electronic Communication as a Transferable Property of Molecular Bridges? J Phys Chem A 2019; 123:10205-10223. [PMID: 31380640 DOI: 10.1021/acs.jpca.9b05618] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Electronic communication through molecular bridges is important for different types of experiments, such as single-molecule conductance, electron transfer, superexchange spin coupling, and intramolecular singlet fission. In many instances, the chemical structure of the bridge determines how the two parts it is connecting communicate, and does so in ways that are transferable between these different manifestations (for example, high conductance often correlates with strong antiferromagnetic spin coupling, and low conductance due to destructive quantum interference correlates with ferromagnetic coupling). Defining electronic communication as a transferable property of the bridge can help transfer knowledge between these different areas of research. Examples and limits of such transferability are discussed here, along with some possible directions for future research, such as employing spin-coupled and mixed-valence systems as structurally well-controlled proxies for understanding molecular conductance and for validating first-principles theoretical methodologies, building conceptual understanding for the growing experimental work on intramolecular singlet fission, and developing measures for the transferability of electronic communication as a bridge property.
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Affiliation(s)
- Carmen Herrmann
- Department of Chemistry , University of Hamburg , Martin-Luther-King-Platz 6 , Hamburg 20146 , Germany
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54
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Xie Z, Bâldea I, Frisbie CD. Energy Level Alignment in Molecular Tunnel Junctions by Transport and Spectroscopy: Self-Consistency for the Case of Alkyl Thiols and Dithiols on Ag, Au, and Pt Electrodes. J Am Chem Soc 2019; 141:18182-18192. [PMID: 31617711 DOI: 10.1021/jacs.9b08905] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report here an extensive study of transport and electronic structure of molecular junctions based on alkyl thiols (CnT; n = 7, 8, 9, 10, 12) and dithiols (CnDT; n = 8, 9, 10) with various lengths contacted with different metal electrodes (Ag, Au, Pt). The dependence of the low-bias resistance (R) on contact work function indicates that transport is HOMO-assisted (p-type transport). Analysis of the current-voltage (I-V) characteristics for CnT and CnDT tunnel junctions with the analytical single-level model (SLM) provides both the HOMO-Fermi energy offset εhtrans and the average molecule-electrode coupling (Γ) as a function of molecular length (n), electrode work function (Φ), and the number of chemical contacts (one or two). The SLM analysis reveals a strong Fermi level (EF) pinning effect in all the junctions, i.e., εhtrans changes very little with n, Φ, and the number of chemical contacts, but Γ depends strongly on these variables. Significantly, independent measurements of the HOMO-Fermi level offset (εhUPS) by ultraviolet photoelectron spectroscopy (UPS) for CnT and CnDT SAMs agree remarkably well with the transport-estimated εhtrans. This result provides strong evidence for hole transport mediated by localized HOMO states at the Au-thiol interface, and not by the delocalized σ states in the C-C backbones, clarifying a long-standing issue in molecular electronics. Our results also substantiate the application of the single-level model for quantitative, unified understanding of transport in benchmark molecular junctions.
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Affiliation(s)
- Zuoti Xie
- Department of Chemical Engineering and Materials Science , University of Minnesota , Minneapolis , Minnesota 55455 , United States
| | - Ioan Bâldea
- Theoretische Chemie , Universität Heidelberg , INF 229 , D-69120 Heidelberg , Germany
| | - C Daniel Frisbie
- Department of Chemical Engineering and Materials Science , University of Minnesota , Minneapolis , Minnesota 55455 , United States
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55
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Wang T, Du W, Tomczak N, Wang L, Nijhuis CA. In Operando Characterization and Control over Intermittent Light Emission from Molecular Tunnel Junctions via Molecular Backbone Rigidity. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2019; 6:1900390. [PMID: 31637155 PMCID: PMC6794720 DOI: 10.1002/advs.201900390] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 07/19/2019] [Indexed: 05/06/2023]
Abstract
In principle, excitation of surface plasmons by molecular tunnel junctions can be controlled at the molecular level. Stable electrical excitation sources of surface plasmons are therefore desirable. Herein, molecular junctions are reported where tunneling charge carriers excite surface plasmons in the gold bottom electrodes via inelastic tunneling and it is shown that the intermittent light emission (blinking) originates from conformational dynamics of the molecules. The blinking rates, in turn, are controlled by changing the rigidity of the molecular backbone. Power spectral density analysis shows that molecular junctions with flexible aliphatic molecules blink, while junctions with rigid aromatic molecules do not.
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Affiliation(s)
- Tao Wang
- Department of ChemistryNational University of Singapore3 Science Drive 3117543SingaporeSingapore
| | - Wei Du
- Department of ChemistryNational University of Singapore3 Science Drive 3117543SingaporeSingapore
| | - Nikodem Tomczak
- Department of ChemistryNational University of Singapore3 Science Drive 3117543SingaporeSingapore
- Institute of Materials Research and EngineeringA*STAR (Agency for Science, Technology and Research)2 Fusionopolis Way, Innovis138634SingaporeSingapore
| | - Lejia Wang
- Department of ChemistryNational University of Singapore3 Science Drive 3117543SingaporeSingapore
| | - Christian A. Nijhuis
- Department of ChemistryNational University of Singapore3 Science Drive 3117543SingaporeSingapore
- Centre for Advanced 2D Materials and Graphene Research CentreNational University of Singapore6 Science Drive 2117546SingaporeSingapore
- NUSNNI NanocoreNational University of Singapore117411SingaporeSingapore
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56
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Chen X, Annadata HV, Kretz B, Zharnikov M, Chi X, Yu X, Egger DA, Nijhuis CA. Interplay of Collective Electrostatic Effects and Level Alignment Dictates the Tunneling Rates across Halogenated Aromatic Monolayer Junctions. J Phys Chem Lett 2019; 10:4142-4147. [PMID: 31260324 DOI: 10.1021/acs.jpclett.9b00387] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Predictions about the electrical conductance across molecular junctions based on self-assembled monolayers (SAMs) are often made from the SAM precursor properties. Collective electrostatic effects, however, in a densely packed SAM can override these predictions. We studied, experimentally and theoretically, molecular tunneling junctions based on thiolate SAMs with an aromatic biphenyl backbone and variable, highly polarizable halogen termini X (S-(C6H5)2X; X = H, F, Cl, Br, or I). We found that the halogen-terminated systems show tunneling rates and dielectric behavior that are independent of X despite the large change in the electronegativity of the terminal atom. Using density functional theory, we show that collective electrostatic effects result in modulations of the electrostatic potential that are strongly confined spatially along the direction of charge transport, thereby rendering the role of the halogen atoms insignificant for SAMs with conjugated backbones.
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Affiliation(s)
- Xiaoping Chen
- Department of Chemistry , National University of Singapore , 3 Science Drive 3 , Singapore 117543 , Singapore
| | - Harshini V Annadata
- Department of Chemistry , National University of Singapore , 3 Science Drive 3 , Singapore 117543 , Singapore
| | - Bernhard Kretz
- Institute of Theoretical Physics , University of Regensburg , Universitätsstraße 31, 93040 Regensburg , Germany
- Department of Physics , Technical University of Munich , 85748 Garching , Germany
| | - Michael Zharnikov
- Angewandte Physikalische Chemie , Universität Heidelberg , Im Neuenheimer Feld 253 , 69120 Heidelberg , Germany
| | - Xiao Chi
- Singapore Synchrotron Light Source , National University of Singapore , 5 Research Link , Singapore 117603 , Singapore
| | - Xiaojiang Yu
- Singapore Synchrotron Light Source , National University of Singapore , 5 Research Link , Singapore 117603 , Singapore
| | - David A Egger
- Institute of Theoretical Physics , University of Regensburg , Universitätsstraße 31, 93040 Regensburg , Germany
- Department of Physics , Technical University of Munich , 85748 Garching , Germany
| | - Christian A Nijhuis
- Department of Chemistry , National University of Singapore , 3 Science Drive 3 , Singapore 117543 , Singapore
- Centre for Advanced 2D Materials and Graphene Research Centre , National University of Singapore , 6 Science Drive 2 , Singapore 117546 , Singapore
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57
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Du W, Han Y, Hu H, Chu HS, Annadata HV, Wang T, Tomczak N, Nijhuis CA. Directional Excitation of Surface Plasmon Polaritons via Molecular Through-Bond Tunneling across Double-Barrier Tunnel Junctions. NANO LETTERS 2019; 19:4634-4640. [PMID: 31184489 DOI: 10.1021/acs.nanolett.9b01665] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Directional excitation of surface plasmon polaritons (SPPs) by electrical means is important for the integration of plasmonics with molecular electronics or steering signals toward other components. We report electrically driven SPP sources based on quantum mechanical tunneling across molecular double-barrier junctions, where the tunneling pathway is defined by the molecules' chemical structure as well as by their tilt angle with respect to the surface normal. Self-assembled monolayers of S(CH2)nBPh (BPh = biphenyl, n = 1-7) on Au, where the alkyl chain and the BPh units define two distinct tunnel barriers in series, were used to demonstrate and control the geometrical effects. The tilt angle of the BPh unit with respect to the surface normal depends on the value of n, and is 45° when n is even and 23° when n is odd. The tilt angle of the alkyl chain is fixed at 30° and independent of n. For values of n = 1-3, SPPs are directionally launched via directional tunneling through the BPh units. For values of n > 3, tunneling along the alkyl chain dominates the SPP excitation. Molecular level control of directionally launching SPPs is achieved without requiring additional on-chip optical elements, such as antennas, or external elements, such as light sources. Using the molecular tunneling junctions, we provide the first direct experimental demonstration of molecular double-barrier tunneling junctions.
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Affiliation(s)
- Wei Du
- Department of Chemistry , National University of Singapore , 3 Science Drive 3 , 117543 Singapore
| | - Yingmei Han
- Department of Chemistry , National University of Singapore , 3 Science Drive 3 , 117543 Singapore
| | - Hongting Hu
- Department of Chemistry , National University of Singapore , 3 Science Drive 3 , 117543 Singapore
| | - Hong-Son Chu
- Department of Electronics and Photonics, Institute of High Performance Computing , A*STAR (Agency for Science, Technology and Research) , 1 Fusionopolis Way, #16-16 Connexis , 138632 Singapore
| | - Harshini V Annadata
- Department of Chemistry , National University of Singapore , 3 Science Drive 3 , 117543 Singapore
| | - Tao Wang
- Department of Chemistry , National University of Singapore , 3 Science Drive 3 , 117543 Singapore
| | - Nikodem Tomczak
- Department of Chemistry , National University of Singapore , 3 Science Drive 3 , 117543 Singapore
- Institute of Materials Research and Engineering , A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis , 138634 Singapore
| | - Christian A Nijhuis
- Department of Chemistry , National University of Singapore , 3 Science Drive 3 , 117543 Singapore
- Centre for Advanced 2D Materials and Graphene Research Centre , National University of Singapore , 6 Science Drive 2 , 117546 Singapore
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58
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Wróbel M, Ossowski J, Krawiec M, Kozieł K, Dąbczyński P, Cyganik P. Oscillation in the stability of consecutive chemical bonds at the molecule-metal interface - the case of ionic bonding. Phys Chem Chem Phys 2019; 21:13411-13414. [PMID: 31210208 DOI: 10.1039/c9cp02061f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ion-induced desorption was successfully applied for the analysis of the stability of chemical bonds at the molecule-metal interface in the case of ionic bonding. The obtained experimental data combined with the results of the DFT calculations reveal the effect of positional oscillations in the stability of consecutive chemical bonds, which has general character in chemistry.
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Affiliation(s)
- Mateusz Wróbel
- Smoluchowski Institute of Physics, Jagiellonian University, Łojasiewicza 11, 30-348 Kraków, Poland.
| | - Jakub Ossowski
- Smoluchowski Institute of Physics, Jagiellonian University, Łojasiewicza 11, 30-348 Kraków, Poland.
| | - Mariusz Krawiec
- Institute of Physics, Maria Curie-Sklodowska University, Pl. M. Curie-Skłodowskiej 1, 20-031 Lublin, Poland
| | - Krzysztof Kozieł
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Kraków, Poland
| | - Paweł Dąbczyński
- Smoluchowski Institute of Physics, Jagiellonian University, Łojasiewicza 11, 30-348 Kraków, Poland.
| | - Piotr Cyganik
- Smoluchowski Institute of Physics, Jagiellonian University, Łojasiewicza 11, 30-348 Kraków, Poland.
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59
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Duffin TJ, Nerngchamnong N, Thompson D, Nijhuis CA. Direct measurement of the local field within alkyl-ferrocenyl-alkanethiolate monolayers: Importance of the supramolecular and electronic structure on the voltammetric response and potential profile. Electrochim Acta 2019. [DOI: 10.1016/j.electacta.2019.04.041] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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60
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Chen X, Hu H, Trasobares J, Nijhuis CA. Rectification Ratio and Tunneling Decay Coefficient Depend on the Contact Geometry Revealed by in Situ Imaging of the Formation of EGaIn Junctions. ACS APPLIED MATERIALS & INTERFACES 2019; 11:21018-21029. [PMID: 31117425 DOI: 10.1021/acsami.9b02033] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
This paper describes how the intensive (tunneling decay coefficient β and rectification ratio R) and extensive (current density J) properties of Ag-S(CH2) n-1CH3//GaO x/EGaIn junctions ( n = 10, 14, 18) and molecular diodes of the form of Ag-S(CH2)11Fc//GaO x/EGaIn depend on Ageo, the contact area between the self-assembled monolayer and the cone-shaped EGaIn tip. Large junctions with Ageo ≥ 1000 μm2 are unreliable and defects, such as pinholes, dominate the charge transport characteristics. For S(CH2)11Fc SAMs, R decreases from 130 to unity with increasing Ageo due to an increase in the leakage current (the current flowing across the junction at reverse bias when the diodes block current flow). The value of β decreases from 1.00 ± 0.06 n-1 to 0.70 ± 0.03 n-1 with increasing Ageo which also indicates that large junctions suffer from defects. Small junctions with Ageo ≤ 300 μm2 are not stable due to the high surface tension of the bulk EGaIn resulting in unstable EGaIn tips. In addition, the contact area for such small junctions is dominated by the rough tip apex reducing the effective contact area and reproducibility significantly. The contact area of very large junctions is dominated by the relatively smooth side walls of the tips. Our findings show that there is an optimum range for the value of Ageo between 300-500 μm2 where the electrical properties of the junctions are dominated by molecular effects. In this range of Ageo, the value of J (defined by I/ Ageo where I is the measured current) increases with Ageo until it plateaus for junctions with Ageo > 1000 μm2 in agreement with recently reported findings by the Whitesides group. In this regime reproducible measurements of J can be obtained provided Ageo is kept constant.
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Affiliation(s)
- Xiaoping Chen
- Department of Chemistry , National University of Singapore , 3 Science Drive 3 , Singapore 117543 , Singapore
| | - Hongting Hu
- Department of Chemistry , National University of Singapore , 3 Science Drive 3 , Singapore 117543 , Singapore
| | - Jorge Trasobares
- Department of Chemistry , National University of Singapore , 3 Science Drive 3 , Singapore 117543 , Singapore
| | - Christian A Nijhuis
- Department of Chemistry , National University of Singapore , 3 Science Drive 3 , Singapore 117543 , Singapore
- Centre for Advanced 2D Materials and Graphene Research Centre , National University of Singapore , 6 Science Drive 2 , Singapore 117546 , Singapore
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61
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Lamport ZA, Broadnax AD, Scharmann B, Bradford RW, DelaCourt A, Meyer N, Li H, Geyer SM, Thonhauser T, Welker ME, Jurchescu OD. Molecular Rectifiers on Silicon: High Performance by Enhancing Top-Electrode/Molecule Coupling. ACS APPLIED MATERIALS & INTERFACES 2019; 11:18564-18570. [PMID: 31050879 DOI: 10.1021/acsami.9b02315] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
One of the simplest molecular-scale electronic devices is the molecular rectifier. In spite of considerable efforts aimed at understanding structure-property relationships in these systems, devices with predictable and stable electronic properties are yet to be developed. Here, we demonstrate highly efficient current rectification in a new class of compounds that form self-assembled monolayers on silicon. We achieve this by exploiting the coupling of the molecules with the top electrode which, in turn, controls the position of the relevant molecular orbitals. The molecules consist of a silane anchoring group and a nitrogen-substituted benzene ring, separated by a propyl group and imine linkage, and result from a simple, robust, and high-yield synthetic procedure. We find that when incorporated in molecular diodes, these compounds can rectify current by as much as 3 orders of magnitude, depending on their structure, with a maximum rectification ratio of 2635 being obtained in ( E)-1-(4-cyanophenyl)- N-(3-(triethoxysilyl) propyl)methanimine (average Ravg = 1683 ± 458, at an applied voltage of 2 V). This performance is on par with that of the best molecular rectifiers obtained on metallic electrodes, but it has the advantage of lower cost and more efficient integration with current silicon technologies. The development of molecular rectifiers on silicon may yield hybrid systems that can expand the use of silicon toward novel functionalities governed by the molecular species grafted onto its surface.
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62
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63
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Najarian AM, McCreery RL. Long-Range Activationless Photostimulated Charge Transport in Symmetric Molecular Junctions. ACS NANO 2019; 13:867-877. [PMID: 30604970 DOI: 10.1021/acsnano.8b08662] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Molecular electronic junctions consisting of nitroazobenzene oligomers covalently bonded to a conducting carbon surface using an established "all-carbon" device design were illuminated with UV-vis light through a partially transparent top electrode. Monitoring junction conductance with a DC bias imposed permitted observation of photocurrents while varying the incident wavelength, light intensity, molecular layer thickness, and temperature. The photocurrent spectrum tracked the in situ absorption spectrum of nitroazobenzene, increased linearly with light intensity, and depended exponentially on applied bias. The electronic characteristics of the photocurrent differed dramatically from those of the same device in the dark, with orders of magnitude higher conductance and very weak attenuation with molecular layer thickness (β = 0.14 nm-1 for thickness above 5 nm). The temperature dependence of the photocurrent was opposite that of the dark current, with a 35% decrease in conductance between 80 and 450 K, while the dark current increased by a factor of 4.5 over the same range. The photocurrent was similar to the dark current for thin molecular layers but greatly exceeded the dark current for low bias and thick molecular layers. We conclude that the light and dark mechanisms are additive, with photoexcited carriers transported without thermal activation for a thickness range of 5-10 nm. The inverse temperature dependence is likely due to scattering or recombination events, both of which increase with temperature and in turn decrease the photocurrent. Photostimulated resonant transport potentially widens the breadth of conceivable molecular electronic devices and may have immediate value for wavelength-specific photodetection.
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Affiliation(s)
| | - Richard L McCreery
- Department of Chemistry , University of Alberta , Edmonton , Canada T6G 2R3
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64
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Paßens M, Karthäuser S. Rotational switches in the two-dimensional fullerene quasicrystal. Acta Crystallogr A Found Adv 2019; 75:41-49. [PMID: 30575582 PMCID: PMC6302930 DOI: 10.1107/s2053273318015681] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Accepted: 11/05/2018] [Indexed: 11/10/2022] Open
Abstract
One of the essential components of molecular electronic circuits are switching elements that are stable in two different states and can ideally be switched on and off many times. Here, distinct buckminsterfullerenes within a self-assembled monolayer, forming a two-dimensional dodecagonal quasicrystal on a Pt-terminated Pt3Ti(111) surface, are identified to form well separated molecular rotational switching elements. Employing scanning tunneling microscopy, the molecular-orbital appearance of the fullerenes in the quasicrystalline monolayer is resolved. Thus, fullerenes adsorbed on the 36 vertex configuration are identified to exhibit a distinctly increased mobility. In addition, this finding is verified by differential conductance measurements. The rotation of these mobile fullerenes can be triggered frequently by applied voltage pulses, while keeping the neighboring molecules immobile. An extensive analysis reveals that crystallographic and energetic constraints at the molecule/metal interface induce an inequality of the local potentials for the 36 and 32.4.3.4 vertex sites and this accounts for the switching ability of fullerenes on the 36 vertex sites. Consequently, a local area of the 8/3 approximant in the two-dimensional fullerene quasicrystal consists of single rotational switching fullerenes embedded in a matrix of inert molecules. Furthermore, it is deduced that optimization of the intermolecular interactions between neighboring fullerenes hinders the realization of translational periodicity in the fullerene monolayer on the Pt-terminated Pt3Ti(111) surface.
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Affiliation(s)
- M. Paßens
- Peter Grünberg Institut (PGI-7) and JARA-FIT, Forschungszentrum Jülich GmbH, Jülich 52425, Germany
| | - S. Karthäuser
- Peter Grünberg Institut (PGI-7) and JARA-FIT, Forschungszentrum Jülich GmbH, Jülich 52425, Germany
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65
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Carlotti M, Soni S, Kumar S, Ai Y, Sauter E, Zharnikov M, Chiechi RC. Two-Terminal Molecular Memory through Reversible Switching of Quantum Interference Features in Tunneling Junctions. Angew Chem Int Ed Engl 2018; 57:15681-15685. [PMID: 30260083 PMCID: PMC6283355 DOI: 10.1002/anie.201807879] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Indexed: 11/11/2022]
Abstract
Large-area molecular tunneling junctions comprising self-assembled monolayers of redox-active molecules are described that exhibit two-terminal bias switching. The as-prepared monolayers undergo partial charge transfer to the underlying metal substrate (Au, Pt, or Ag), which converts their cores from a quinoid to a hydroquinoid form. The resulting rearomatization converts the bond topology from a cross-conjugated to a linearly conjugated π system. The cross-conjugated form correlates to the appearance of an interference feature in the transmission spectrum that vanishes for the linearly conjugated form. Owing to the presence of electron-withdrawing nitrile groups, the reduction potential and the interference feature lie close to the work function and Fermi level of the metallic substrate. We exploited the relationship between conjugation patterns and quantum interference to create nonvolatile memory in proto-devices using eutectic Ga-In as the top contact.
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Affiliation(s)
- Marco Carlotti
- Stratingh Institute for ChemistryUniversity of GroningenNijenborgh 49747 AGGroningenThe Netherlands
- Zernike Institute for Advanced MaterialsNijenborgh 49747 AGGroningenThe Netherlands
| | - Saurabh Soni
- Stratingh Institute for ChemistryUniversity of GroningenNijenborgh 49747 AGGroningenThe Netherlands
- Zernike Institute for Advanced MaterialsNijenborgh 49747 AGGroningenThe Netherlands
| | - Sumit Kumar
- Stratingh Institute for ChemistryUniversity of GroningenNijenborgh 49747 AGGroningenThe Netherlands
- Zernike Institute for Advanced MaterialsNijenborgh 49747 AGGroningenThe Netherlands
| | - Yong Ai
- Stratingh Institute for ChemistryUniversity of GroningenNijenborgh 49747 AGGroningenThe Netherlands
- Zernike Institute for Advanced MaterialsNijenborgh 49747 AGGroningenThe Netherlands
| | - Eric Sauter
- Applied Physical ChemistryHeidelberg UniversityIm Neuenheimer Feld 253Heidelberg69120Germany
| | - Michael Zharnikov
- Applied Physical ChemistryHeidelberg UniversityIm Neuenheimer Feld 253Heidelberg69120Germany
| | - Ryan C. Chiechi
- Stratingh Institute for ChemistryUniversity of GroningenNijenborgh 49747 AGGroningenThe Netherlands
- Zernike Institute for Advanced MaterialsNijenborgh 49747 AGGroningenThe Netherlands
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66
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Carlotti M, Soni S, Kumar S, Ai Y, Sauter E, Zharnikov M, Chiechi RC. Two-Terminal Molecular Memory through Reversible Switching of Quantum Interference Features in Tunneling Junctions. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201807879] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Marco Carlotti
- Stratingh Institute for Chemistry; University of Groningen; Nijenborgh 4 9747 AG Groningen The Netherlands
- Zernike Institute for Advanced Materials; Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Saurabh Soni
- Stratingh Institute for Chemistry; University of Groningen; Nijenborgh 4 9747 AG Groningen The Netherlands
- Zernike Institute for Advanced Materials; Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Sumit Kumar
- Stratingh Institute for Chemistry; University of Groningen; Nijenborgh 4 9747 AG Groningen The Netherlands
- Zernike Institute for Advanced Materials; Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Yong Ai
- Stratingh Institute for Chemistry; University of Groningen; Nijenborgh 4 9747 AG Groningen The Netherlands
- Zernike Institute for Advanced Materials; Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Eric Sauter
- Applied Physical Chemistry; Heidelberg University; Im Neuenheimer Feld 253 Heidelberg 69120 Germany
| | - Michael Zharnikov
- Applied Physical Chemistry; Heidelberg University; Im Neuenheimer Feld 253 Heidelberg 69120 Germany
| | - Ryan C. Chiechi
- Stratingh Institute for Chemistry; University of Groningen; Nijenborgh 4 9747 AG Groningen The Netherlands
- Zernike Institute for Advanced Materials; Nijenborgh 4 9747 AG Groningen The Netherlands
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67
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Souto M, Díez-Cabanes V, Yuan L, Kyvik AR, Ratera I, Nijhuis CA, Cornil J, Veciana J. Influence of the donor unit on the rectification ratio in tunnel junctions based on donor-acceptor SAMs using PTM units as acceptors. Phys Chem Chem Phys 2018; 20:25638-25647. [PMID: 30288535 DOI: 10.1039/c8cp05488f] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Dyads formed by an electron donor unit (D) covalently linked to an electron acceptor (A) by an organic bridge are promising materials as molecular rectifiers. Very recently, we have reported the charge transport measurements across self-assembled monolayers (SAMs) of two D-A systems consisting of the ferrocene (Fc) electron-donor linked to a polychlorotriphenylmethane (PTM) electron-acceptor in its non-radical (SAM 1) and radical (SAM 2) forms. Interestingly, we observed that the non-radical SAM 1 showed rectification behavior of 2 orders of magnitude higher than its radical analogue dyad 2. In order to study the influence of the donor unit on the transport properties, we report herein the synthesis and characterization of two new D-A SAMs in which the electron-donor Fc unit is replaced by a tetrathiafulvalene (TTF) moiety linked to the PTM unit in its non-radical (SAM 3) and radical (SAM 4) forms. The observed decrease in the rectification ratio and increased current density for TTF-PTM based SAMs 3 and 4 in comparison to Fc-PTM based SAMs 1 and 2 are explained, supported by theoretical calculations, by significant changes in the electronic and supramolecular structures.
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Affiliation(s)
- Manuel Souto
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC)/CIBER-BBN, Campus Universitari de UAB, 08193 Cerdanyola del Vallès (Barcelona), Spain.
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68
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Richter S, Mentovich E, Elnathan R. Realization of Molecular-Based Transistors. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1706941. [PMID: 29873854 DOI: 10.1002/adma.201706941] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 02/06/2018] [Indexed: 06/08/2023]
Abstract
Molecular-based devices are widely considered as significant candidates to play a role in the next generation of "post-complementary metal-oxide-semiconductor" devices. In this context, molecular-based transistors: molecular junctions that can be electrically gated-are of particular interest as they allow new modes of operation. The properties of molecular transistors composed of a single- or multimolecule assemblies, focusing on their practicality as real-world devices, concerning industry demands and its roadmap are compared. Also, the capability of the gate electrode to modulate the molecular transistor characteristics efficiently is addressed, showing that electrical gating can be easily facilitated in single molecular transistors and that gating of transistor composed of molecular assemblies is possible if the device is formed vertically. It is concluded that while the single-molecular transistor exhibits better performance on the lab-scale, its realization faces signifacant challenges when compared to those faced by transistors composed of a multimolecule assembly.
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Affiliation(s)
- Shachar Richter
- Department of Materials Science and Engineering, University Center for Nanoscience and Nanotechnology, Faculty of Engineering, Tel-Aviv University, Tel-Aviv, 6997801, Israel
| | - Elad Mentovich
- Process Technologies, Mellanox Technologies Ltd., Hakidma 26 St., Ofer Industrial Park, Yokneam, 2069200, Israel
| | - Roey Elnathan
- Faculty of Pharmacy and Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, VIC, 3052, Australia
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69
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Petrini PA, Silva RML, de Oliveira RF, Merces L, Bof Bufon CC. Hybrid nanomembrane-based capacitors for the determination of the dielectric constant of semiconducting molecular ensembles. NANOTECHNOLOGY 2018; 29:265201. [PMID: 29624186 DOI: 10.1088/1361-6528/aabc44] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Considerable advances in the field of molecular electronics have been achieved over the recent years. One persistent challenge, however, is the exploitation of the electronic properties of molecules fully integrated into devices. Typically, the molecular electronic properties are investigated using sophisticated techniques incompatible with a practical device technology, such as the scanning tunneling microscopy. The incorporation of molecular materials in devices is not a trivial task as the typical dimensions of electrical contacts are much larger than the molecular ones. To tackle this issue, we report on hybrid capacitors using mechanically-compliant nanomembranes to encapsulate ultrathin molecular ensembles for the investigation of molecular dielectric properties. As the prototype material, copper (II) phthalocyanine (CuPc) has been chosen as information on its dielectric constant (k CuPc) at the molecular scale is missing. Here, hybrid nanomembrane-based capacitors containing metallic nanomembranes, insulating Al2O3 layers, and the CuPc molecular ensembles have been fabricated and evaluated. The Al2O3 is used to prevent short circuits through the capacitor plates as the molecular layer is considerably thin (<30 nm). From the electrical measurements of devices with molecular layers of different thicknesses, the CuPc dielectric constant has been reliably determined (k CuPc = 4.5 ± 0.5). These values suggest a mild contribution of the molecular orientation on the CuPc dielectric properties. The reported nanomembrane-based capacitor is a viable strategy for the dielectric characterization of ultrathin molecular ensembles integrated into a practical, real device technology.
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Affiliation(s)
- Paula A Petrini
- Brazilian Nanotechnology National Laboratory (LNNano), Brazilian Center for Research in Energy and Materials (CNPEM), 13083-970 Campinas, São Paulo, Brazil. Postgraduate Program in Materials Science and Technology (POSMAT), São Paulo State University (UNESP), 17033-360 Bauru, São Paulo, Brazil
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70
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Pin C, Ishida S, Takahashi G, Sudo K, Fukaminato T, Sasaki K. Trapping and Deposition of Dye-Molecule Nanoparticles in the Nanogap of a Plasmonic Antenna. ACS OMEGA 2018; 3:4878-4883. [PMID: 31458703 PMCID: PMC6641714 DOI: 10.1021/acsomega.8b00282] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Accepted: 04/26/2018] [Indexed: 05/23/2023]
Abstract
Plasmonic nanostructures, which allow light focusing at the deep subwavelength scale, and colloidal nanoparticles with unique optoelectronic properties are nowadays fabricated with nanometer precision. However, to fully control and exploit nanoscale light-matter interactions in hybrid plasmonic-nanophotonic devices, both materials must be assembled in heterostructures with similar precision. Near-field optical forces have recently attracted much attention, as they can precisely trap and position nanoparticles at plasmonic hotspots. However, long-range attraction and the surface bonding of nanoparticles usually require other specific techniques, such as electrothermal heating and surface chemical treatments. This Letter reports on the optical trapping and deposition of dye-molecule nanoparticles in the nanogap of a gold antenna. The nanoparticles are captured by focusing a near-infrared laser beam on a targeted plasmonic antenna. This single-step deposition process requires only a few seconds under 1.4-1.8 MW·cm-2 continuous-wave illumination and shows a polarization dependence smaller than expected. Fluorescence and electronic microscopy observations suggest that nanoparticle deposition arises from a trade-off between optical and thermal effects.
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Affiliation(s)
- Christophe Pin
- Research
Institute for Electronic Science, Hokkaido
University, Kita 20 Nishi
10, Kita-ku, Sapporo 001-0020, Japan
| | - Shutaro Ishida
- Research
Institute for Electronic Science, Hokkaido
University, Kita 20 Nishi
10, Kita-ku, Sapporo 001-0020, Japan
| | - Genta Takahashi
- Research
Institute for Electronic Science, Hokkaido
University, Kita 20 Nishi
10, Kita-ku, Sapporo 001-0020, Japan
| | - Kota Sudo
- Research
Institute for Electronic Science, Hokkaido
University, Kita 20 Nishi
10, Kita-ku, Sapporo 001-0020, Japan
| | - Tuyoshi Fukaminato
- Department
of Applied Chemistry & Biochemistry, Graduate School of Science
& Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto 860-8555, Japan
| | - Keiji Sasaki
- Research
Institute for Electronic Science, Hokkaido
University, Kita 20 Nishi
10, Kita-ku, Sapporo 001-0020, Japan
- E-mail: . Tel.: +81-11-706-9396. Fax: +81-11-706-9391
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71
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Yuan L, Wang L, Garrigues AR, Jiang L, Annadata HV, Anguera Antonana M, Barco E, Nijhuis CA. Transition from direct to inverted charge transport Marcus regions in molecular junctions via molecular orbital gating. NATURE NANOTECHNOLOGY 2018; 13:322-329. [PMID: 29581549 DOI: 10.1038/s41565-018-0068-4] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Accepted: 01/17/2018] [Indexed: 05/25/2023]
Abstract
Solid-state molecular tunnel junctions are often assumed to operate in the Landauer regime, which describes essentially activationless coherent tunnelling processes. In solution, on the other hand, charge transfer is described by Marcus theory, which accounts for thermally activated processes. In practice, however, thermally activated transport phenomena are frequently observed also in solid-state molecular junctions but remain poorly understood. Here, we show experimentally the transition from the Marcus to the inverted Marcus region in a solid-state molecular tunnel junction by means of intra-molecular orbital gating that can be tuned via the chemical structure of the molecule and applied bias. In the inverted Marcus region, charge transport is incoherent, yet virtually independent of temperature. Our experimental results fit well to a theoretical model that combines Landauer and Marcus theories and may have implications for the interpretation of temperature-dependent charge transport measurements in molecular junctions.
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Affiliation(s)
- Li Yuan
- Department of Chemistry, National University of Singapore, Singapore, Singapore
| | - Lejia Wang
- Department of Chemistry, National University of Singapore, Singapore, Singapore
- School of Materials and Chemical Engineering, Ningbo University of Technology, Ningbo, China
| | - Alvar R Garrigues
- Department of Physics, University of Central Florida, Orlando, Florida, USA
| | - Li Jiang
- Department of Chemistry, National University of Singapore, Singapore, Singapore
| | | | | | - Enrique Barco
- Department of Physics, University of Central Florida, Orlando, Florida, USA.
| | - Christian A Nijhuis
- Department of Chemistry, National University of Singapore, Singapore, Singapore.
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore, Singapore.
- NUSNNI-Nanocore, National University of Singapore, Singapore, Singapore.
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72
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Stragliotto MF, Fernández JL, Dassie SA, Giacomelli CE. An integrated experimental-theoretical approach to understand the electron transfer mechanism of adsorbed ferrocene-terminated alkanethiol monolayers. Electrochim Acta 2018. [DOI: 10.1016/j.electacta.2017.12.091] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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73
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Supur M, Van Dyck C, Bergren AJ, McCreery RL. Bottom-up, Robust Graphene Ribbon Electronics in All-Carbon Molecular Junctions. ACS APPLIED MATERIALS & INTERFACES 2018; 10:6090-6095. [PMID: 29400435 DOI: 10.1021/acsami.7b19305] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Large-area molecular electronic junctions consisting of 5-carbon wide graphene ribbons (GR) with lengths of 2-12 nm between carbon electrodes were fabricated by electrochemical reduction of diazotized 1,8-diaminonaphthalene. Their conductance greatly exceeds that observed for other molecular junctions of similar thicknesses, by a factor of >1 × 104 compared to polyphenylenes and >1 × 107 compared to alkane chains. The remarkable increase of conductance of the GR nanolayer results from (i) uninterrupted planarity of fused-arene structure affording extensive π-electron delocalization and (ii) enhanced electronic coupling of molecular layer with the carbon bottom contact by two-point covalent bonding, in agreement with DFT-based simulations.
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Affiliation(s)
- Mustafa Supur
- Department of Chemistry, University of Alberta , 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada
| | - Colin Van Dyck
- National Institute for Nanotechnology (NINT), National Research Council Canada , 11421 Saskatchewan Drive, Edmonton, Alberta T6G 2M9, Canada
| | - Adam J Bergren
- National Institute for Nanotechnology (NINT), National Research Council Canada , 11421 Saskatchewan Drive, Edmonton, Alberta T6G 2M9, Canada
| | - Richard L McCreery
- Department of Chemistry, University of Alberta , 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada
- National Institute for Nanotechnology (NINT), National Research Council Canada , 11421 Saskatchewan Drive, Edmonton, Alberta T6G 2M9, Canada
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74
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Morteza Najarian A, Bayat A, McCreery RL. Orbital Control of Photocurrents in Large Area All-Carbon Molecular Junctions. J Am Chem Soc 2018; 140:1900-1909. [DOI: 10.1021/jacs.7b12577] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Amin Morteza Najarian
- Department
of Chemistry, University of Alberta, Edmonton, Alberta, Canada, T6G 2R3
- National
Institute for Nanotechnology, National Research Council Canada, Edmonton, Alberta, Canada, T6G 2G2
| | - Akhtar Bayat
- Department
of Chemistry, University of Alberta, Edmonton, Alberta, Canada, T6G 2R3
- National
Institute for Nanotechnology, National Research Council Canada, Edmonton, Alberta, Canada, T6G 2G2
| | - Richard L. McCreery
- Department
of Chemistry, University of Alberta, Edmonton, Alberta, Canada, T6G 2R3
- National
Institute for Nanotechnology, National Research Council Canada, Edmonton, Alberta, Canada, T6G 2G2
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75
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Sangeeth CSS, Jiang L, Nijhuis CA. Bottom-electrode induced defects in self-assembled monolayer (SAM)-based tunnel junctions affect only the SAM resistance, not the contact resistance or SAM capacitance. RSC Adv 2018; 8:19939-19949. [PMID: 35541643 PMCID: PMC9080736 DOI: 10.1039/c8ra01513a] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Accepted: 05/14/2018] [Indexed: 12/22/2022] Open
Abstract
In large area molecular junctions, defects are always present and can be caused by impurities and/or defects in the electrode materials and/or SAMs, but how they affect the electrical characteristics of junctions has rarely been studied. Usually, junctions are characterized by two-terminal current–voltage measurements where only the total current across the junction is measured, but with these methods one cannot distinguish how the individual components of the junctions are altered by the defects. Here we show that the roughness of the bottom-electrode is a crucial factor in determining the electrical properties of self-assembled monolayer (SAM)-based junctions. We used potentiodynamic impedance spectroscopy to reveal which components of the junctions are altered by defective bottom electrodes because this method allows for direct determination of all components that impede charge transport in the equivalent circuit of the junctions. We intentionally introduced defects via the roughness of the bottom electrode and found that these defects lower the SAM resistance but they do not alter the capacitance of the SAM or the contact resistance of the junction. In other words, defective junctions can be seen as “leaky capacitors” resulting in an underestimation of the SAM resistance of two orders of magnitude. These results help to improve the interpretation of data generated by SAM-based junctions and explain in part the observed large spread of reported tunneling rates for the same molecules measured across different platforms. In large area molecular junctions, defects are always present and can be caused by impurities and/or defects in the electrode materials and/or SAMs, but how they affect the electrical characteristics of junctions has rarely been studied.![]()
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Affiliation(s)
| | - Li Jiang
- Department of Chemistry
- National University of Singapore
- Singapore 117543
- Singapore
| | - Christian A. Nijhuis
- Department of Chemistry
- National University of Singapore
- Singapore 117543
- Singapore
- Centre for Advanced 2D Materials and Graphene Research Centre
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