Controlling Rectification in Metal–Molecules–Metal Junctions Based on 11-(Ferrocenyl) Undecanethiol: Effects of the Electronic Coupling Strength

Quyen Van nguyen

doi:10.1021/acs.jpcc.1c10806

Controlling Rectification in Metal–Molecules–Metal Junctions Based on 11-(Ferrocenyl) Undecanethiol: Effects of the Electronic Coupling Strength

Quyen Van nguyen

Materials Research Science & Engineering Center

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10 Scopus citations

Abstract

We report an effect of contact materials (Ag, Au, and Pt) on transport properties of molecular junctions (MJs) based on self-assembled monolayers of 11-(Ferrocenyl) undecanethiol (HSC₁₁Fc). Particularly, we observed that the Fc unit directly contacting the Ag-coated atomic force microscopy (AFM) tip in symmetrical MJs, Ag/SC₁₁Fc/Ag, leads to a large rectification (∼150) with a giant electrical current density (∼4 × 10⁴A·cm^-2) at a relatively small negative voltage, -1.5 V. We also observed that the material of the bottom electrode strongly affects the rectified current density but not the rectification ratio in metal/SC₁₁Fc/Ag. Optimizing the material of the bottom electrode, especially the energy offset barrier ϵ_o, can produce a large rectification (∼170) at 1.5 V with a giant electrical current, 2.4 × 10⁵A·cm^-2, in asymmetrical MJs using the Ag-coated AFM tip. A simplified Landauer allows us to approximately quantify the electronic coupling strength in symmetrical MJs, Γ_Fc-Ag∼5.2 meV, that is 50 times greater than Γ_Ag-Fc. In contrast, the electronic coupling strength at the Fc-Au (or Pt) interface is strong (Γ_Fc-Au∼120 meV), which leads to a small rectification and high conductance. The direction of the small rectification in the strong coupling regime (Γ_Fc-Au/Pt) can be reversed by controlling the work function of the metal contacts. Overall, our results provide a clear picture of the influence of both the electronic coupling strength and the energy offset barrier on the transport properties and further prove that the conductive-probe atomic force microscopy is a useful, versatile tool for determining structure-transport relationships in molecular junctions.

Original language	English (US)
Pages (from-to)	6405-6412
Number of pages	8
Journal	Journal of Physical Chemistry C
Volume	126
Issue number	14
DOIs	https://doi.org/10.1021/acs.jpcc.1c10806
State	Published - Apr 14 2022

Bibliographical note

Funding Information:
The author thanks Professor C. Daniel Frisbie at the University of Minnesota and Professor Zuoti Xie at the Department of Materials Science and Engineering, Guangdong Technion-Israel Institute of Science, for their invaluable discussion. The author acknowledges the financial support of the National Science Foundation (CHE-2003199) and the Vietnam Academy of Science and Technology (THTEXS.03/21-24). Parts of this work were carried out in the Characterization Facility, the University of Minnesota, which receives partial support from the NSF through the MRSEC (award number DMR-2011401) and NNCI programs (award number ECCS-2025124). Parts of this work were carried out in the Department of Advanced Materials Science and Nanotechnology, University of Science and Technology of Hanoi.

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@article{3186250e62e7423189f751c1550a2e20,

title = "Controlling Rectification in Metal–Molecules–Metal Junctions Based on 11-(Ferrocenyl) Undecanethiol: Effects of the Electronic Coupling Strength",

abstract = "We report an effect of contact materials (Ag, Au, and Pt) on transport properties of molecular junctions (MJs) based on self-assembled monolayers of 11-(Ferrocenyl) undecanethiol (HSC11Fc). Particularly, we observed that the Fc unit directly contacting the Ag-coated atomic force microscopy (AFM) tip in symmetrical MJs, Ag/SC11Fc/Ag, leads to a large rectification (∼150) with a giant electrical current density (∼4 × 104A·cm-2) at a relatively small negative voltage, -1.5 V. We also observed that the material of the bottom electrode strongly affects the rectified current density but not the rectification ratio in metal/SC11Fc/Ag. Optimizing the material of the bottom electrode, especially the energy offset barrier ϵo, can produce a large rectification (∼170) at 1.5 V with a giant electrical current, 2.4 × 105A·cm-2, in asymmetrical MJs using the Ag-coated AFM tip. A simplified Landauer allows us to approximately quantify the electronic coupling strength in symmetrical MJs, ΓFc-Ag∼5.2 meV, that is 50 times greater than ΓAg-Fc. In contrast, the electronic coupling strength at the Fc-Au (or Pt) interface is strong (ΓFc-Au∼120 meV), which leads to a small rectification and high conductance. The direction of the small rectification in the strong coupling regime (ΓFc-Au/Pt) can be reversed by controlling the work function of the metal contacts. Overall, our results provide a clear picture of the influence of both the electronic coupling strength and the energy offset barrier on the transport properties and further prove that the conductive-probe atomic force microscopy is a useful, versatile tool for determining structure-transport relationships in molecular junctions.",

author = "\{Van nguyen\}, Quyen",

note = "Funding Information: The author thanks Professor C. Daniel Frisbie at the University of Minnesota and Professor Zuoti Xie at the Department of Materials Science and Engineering, Guangdong Technion-Israel Institute of Science, for their invaluable discussion. The author acknowledges the financial support of the National Science Foundation (CHE-2003199) and the Vietnam Academy of Science and Technology (THTEXS.03/21-24). Parts of this work were carried out in the Characterization Facility, the University of Minnesota, which receives partial support from the NSF through the MRSEC (award number DMR-2011401) and NNCI programs (award number ECCS-2025124). Parts of this work were carried out in the Department of Advanced Materials Science and Nanotechnology, University of Science and Technology of Hanoi. Publisher Copyright: {\textcopyright} 2022 American Chemical Society. All rights reserved.",

year = "2022",

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doi = "10.1021/acs.jpcc.1c10806",

language = "English (US)",

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T1 - Controlling Rectification in Metal–Molecules–Metal Junctions Based on 11-(Ferrocenyl) Undecanethiol: Effects of the Electronic Coupling Strength

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N1 - Funding Information: The author thanks Professor C. Daniel Frisbie at the University of Minnesota and Professor Zuoti Xie at the Department of Materials Science and Engineering, Guangdong Technion-Israel Institute of Science, for their invaluable discussion. The author acknowledges the financial support of the National Science Foundation (CHE-2003199) and the Vietnam Academy of Science and Technology (THTEXS.03/21-24). Parts of this work were carried out in the Characterization Facility, the University of Minnesota, which receives partial support from the NSF through the MRSEC (award number DMR-2011401) and NNCI programs (award number ECCS-2025124). Parts of this work were carried out in the Department of Advanced Materials Science and Nanotechnology, University of Science and Technology of Hanoi. Publisher Copyright: © 2022 American Chemical Society. All rights reserved.

PY - 2022/4/14

Y1 - 2022/4/14

N2 - We report an effect of contact materials (Ag, Au, and Pt) on transport properties of molecular junctions (MJs) based on self-assembled monolayers of 11-(Ferrocenyl) undecanethiol (HSC11Fc). Particularly, we observed that the Fc unit directly contacting the Ag-coated atomic force microscopy (AFM) tip in symmetrical MJs, Ag/SC11Fc/Ag, leads to a large rectification (∼150) with a giant electrical current density (∼4 × 104A·cm-2) at a relatively small negative voltage, -1.5 V. We also observed that the material of the bottom electrode strongly affects the rectified current density but not the rectification ratio in metal/SC11Fc/Ag. Optimizing the material of the bottom electrode, especially the energy offset barrier ϵo, can produce a large rectification (∼170) at 1.5 V with a giant electrical current, 2.4 × 105A·cm-2, in asymmetrical MJs using the Ag-coated AFM tip. A simplified Landauer allows us to approximately quantify the electronic coupling strength in symmetrical MJs, ΓFc-Ag∼5.2 meV, that is 50 times greater than ΓAg-Fc. In contrast, the electronic coupling strength at the Fc-Au (or Pt) interface is strong (ΓFc-Au∼120 meV), which leads to a small rectification and high conductance. The direction of the small rectification in the strong coupling regime (ΓFc-Au/Pt) can be reversed by controlling the work function of the metal contacts. Overall, our results provide a clear picture of the influence of both the electronic coupling strength and the energy offset barrier on the transport properties and further prove that the conductive-probe atomic force microscopy is a useful, versatile tool for determining structure-transport relationships in molecular junctions.

AB - We report an effect of contact materials (Ag, Au, and Pt) on transport properties of molecular junctions (MJs) based on self-assembled monolayers of 11-(Ferrocenyl) undecanethiol (HSC11Fc). Particularly, we observed that the Fc unit directly contacting the Ag-coated atomic force microscopy (AFM) tip in symmetrical MJs, Ag/SC11Fc/Ag, leads to a large rectification (∼150) with a giant electrical current density (∼4 × 104A·cm-2) at a relatively small negative voltage, -1.5 V. We also observed that the material of the bottom electrode strongly affects the rectified current density but not the rectification ratio in metal/SC11Fc/Ag. Optimizing the material of the bottom electrode, especially the energy offset barrier ϵo, can produce a large rectification (∼170) at 1.5 V with a giant electrical current, 2.4 × 105A·cm-2, in asymmetrical MJs using the Ag-coated AFM tip. A simplified Landauer allows us to approximately quantify the electronic coupling strength in symmetrical MJs, ΓFc-Ag∼5.2 meV, that is 50 times greater than ΓAg-Fc. In contrast, the electronic coupling strength at the Fc-Au (or Pt) interface is strong (ΓFc-Au∼120 meV), which leads to a small rectification and high conductance. The direction of the small rectification in the strong coupling regime (ΓFc-Au/Pt) can be reversed by controlling the work function of the metal contacts. Overall, our results provide a clear picture of the influence of both the electronic coupling strength and the energy offset barrier on the transport properties and further prove that the conductive-probe atomic force microscopy is a useful, versatile tool for determining structure-transport relationships in molecular junctions.

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Controlling Rectification in Metal–Molecules–Metal Junctions Based on 11-(Ferrocenyl) Undecanethiol: Effects of the Electronic Coupling Strength

Abstract

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Controlling Rectification in Metal–Molecules–Metal Junctions Based on 11-(Ferrocenyl) Undecanethiol: Effects of the Electronic Coupling Strength

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Bibliographical note

MRSEC Support

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