Quantifying Image Charge Effects in Molecular Tunnel Junctions Based on Self-Assembled Monolayers of Substituted Oligophenylene Ethynylene Dithiols

Zuoti Xie; Valentin Diez Cabanes; Quyen Van Nguyen; Sandra Rodriguez-Gonzalez; Lucie Norel; Olivier Galangau; Stéphane Rigaut; Jérôme Cornil; C. Daniel Frisbie

doi:10.1021/acsami.1c16398

Quantifying Image Charge Effects in Molecular Tunnel Junctions Based on Self-Assembled Monolayers of Substituted Oligophenylene Ethynylene Dithiols

Zuoti Xie^*, Valentin Diez Cabanes, Quyen Van Nguyen, Sandra Rodriguez-Gonzalez, Lucie Norel, Olivier Galangau, Stéphane Rigaut, Jérôme Cornil, C. Daniel Frisbie

^*Corresponding author for this work

Materials Science and Engineering

Research output: Contribution to journal › Article › peer-review

6 Scopus citations

Abstract

A number of factors contribute to orbital energy alignment with respect to the Fermi level in molecular tunnel junctions. Here, we report a combined experimental and theoretical effort to quantify the effect of metal image potentials on the highest occupied molecular orbital to Fermi level offset, ϵh, for molecular junctions based on self-assembled monolayers (SAMs) of oligophenylene ethynylene dithiols (OPX) on Au. Our experimental approach involves the use of both transport and photoelectron spectroscopy to extract the offsets, ϵhtrans and ϵhUPS, respectively. We take the difference in these quantities to be the image potential energy eVimage. In the theoretical approach, we use density functional theory (DFT) to calculate directly eVimage between positive charge on an OPX molecule and the negative image charge in the Au. Both approaches yield eVimage ∼-0.1 eV per metal contact, meaning that the total image potential energy is a-0.2 eV for an assembled junction with two Au contacts. Thus, we find that the total image potential energy is 25-30% of the total offset ϵh, which means that image charge effects are significant in OPX junctions. Our methods should be generally applicable to understanding image charge effects as a function of molecular size, for example, in a variety of SAM-based junctions. © 2021 American Chemical Society.

Original language	English
Journal	ACS applied materials & interfaces
DOIs	https://doi.org/10.1021/acsami.1c16398
State	Published - 16 Nov 2021

Keywords

molecular junction
tunneling
charge transport
image charge
Fermi level-HOMO offset
single level model
photoelectron spectroscopy

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10.1021/acsami.1c16398

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@article{512fe64528d74997827475a7abb2ab5c,

title = "Quantifying Image Charge Effects in Molecular Tunnel Junctions Based on Self-Assembled Monolayers of Substituted Oligophenylene Ethynylene Dithiols",

abstract = "A number of factors contribute to orbital energy alignment with respect to the Fermi level in molecular tunnel junctions. Here, we report a combined experimental and theoretical effort to quantify the effect of metal image potentials on the highest occupied molecular orbital to Fermi level offset, ϵh, for molecular junctions based on self-assembled monolayers (SAMs) of oligophenylene ethynylene dithiols (OPX) on Au. Our experimental approach involves the use of both transport and photoelectron spectroscopy to extract the offsets, ϵhtrans and ϵhUPS, respectively. We take the difference in these quantities to be the image potential energy eVimage. In the theoretical approach, we use density functional theory (DFT) to calculate directly eVimage between positive charge on an OPX molecule and the negative image charge in the Au. Both approaches yield eVimage ∼-0.1 eV per metal contact, meaning that the total image potential energy is a-0.2 eV for an assembled junction with two Au contacts. Thus, we find that the total image potential energy is 25-30% of the total offset ϵh, which means that image charge effects are significant in OPX junctions. Our methods should be generally applicable to understanding image charge effects as a function of molecular size, for example, in a variety of SAM-based junctions. {\textcopyright} 2021 American Chemical Society.",

keywords = "molecular junction, tunneling, charge transport, image charge, Fermi level-HOMO offset, single level model, photoelectron spectroscopy",

author = "Zuoti Xie and {Diez Cabanes}, Valentin and {Van Nguyen}, Quyen and Sandra Rodriguez-Gonzalez and Lucie Norel and Olivier Galangau and St{\'e}phane Rigaut and J{\'e}r{\^o}me Cornil and Frisbie, {C. Daniel}",

year = "2021",

month = nov,

day = "16",

doi = "10.1021/acsami.1c16398",

language = "英语",

journal = "ACS applied materials & interfaces",

issn = "1944-8244",

publisher = "American Chemical Society",

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TY - JOUR

T1 - Quantifying Image Charge Effects in Molecular Tunnel Junctions Based on Self-Assembled Monolayers of Substituted Oligophenylene Ethynylene Dithiols

AU - Xie, Zuoti

AU - Diez Cabanes, Valentin

AU - Van Nguyen, Quyen

AU - Rodriguez-Gonzalez, Sandra

AU - Norel, Lucie

AU - Galangau, Olivier

AU - Rigaut, Stéphane

AU - Cornil, Jérôme

AU - Frisbie, C. Daniel

PY - 2021/11/16

Y1 - 2021/11/16

N2 - A number of factors contribute to orbital energy alignment with respect to the Fermi level in molecular tunnel junctions. Here, we report a combined experimental and theoretical effort to quantify the effect of metal image potentials on the highest occupied molecular orbital to Fermi level offset, ϵh, for molecular junctions based on self-assembled monolayers (SAMs) of oligophenylene ethynylene dithiols (OPX) on Au. Our experimental approach involves the use of both transport and photoelectron spectroscopy to extract the offsets, ϵhtrans and ϵhUPS, respectively. We take the difference in these quantities to be the image potential energy eVimage. In the theoretical approach, we use density functional theory (DFT) to calculate directly eVimage between positive charge on an OPX molecule and the negative image charge in the Au. Both approaches yield eVimage ∼-0.1 eV per metal contact, meaning that the total image potential energy is a-0.2 eV for an assembled junction with two Au contacts. Thus, we find that the total image potential energy is 25-30% of the total offset ϵh, which means that image charge effects are significant in OPX junctions. Our methods should be generally applicable to understanding image charge effects as a function of molecular size, for example, in a variety of SAM-based junctions. © 2021 American Chemical Society.

AB - A number of factors contribute to orbital energy alignment with respect to the Fermi level in molecular tunnel junctions. Here, we report a combined experimental and theoretical effort to quantify the effect of metal image potentials on the highest occupied molecular orbital to Fermi level offset, ϵh, for molecular junctions based on self-assembled monolayers (SAMs) of oligophenylene ethynylene dithiols (OPX) on Au. Our experimental approach involves the use of both transport and photoelectron spectroscopy to extract the offsets, ϵhtrans and ϵhUPS, respectively. We take the difference in these quantities to be the image potential energy eVimage. In the theoretical approach, we use density functional theory (DFT) to calculate directly eVimage between positive charge on an OPX molecule and the negative image charge in the Au. Both approaches yield eVimage ∼-0.1 eV per metal contact, meaning that the total image potential energy is a-0.2 eV for an assembled junction with two Au contacts. Thus, we find that the total image potential energy is 25-30% of the total offset ϵh, which means that image charge effects are significant in OPX junctions. Our methods should be generally applicable to understanding image charge effects as a function of molecular size, for example, in a variety of SAM-based junctions. © 2021 American Chemical Society.

KW - molecular junction

KW - tunneling

KW - charge transport

KW - image charge

KW - Fermi level-HOMO offset

KW - single level model

KW - photoelectron spectroscopy

U2 - 10.1021/acsami.1c16398

DO - 10.1021/acsami.1c16398

M3 - 文章

C2 - 34783518

SN - 1944-8244

JO - ACS applied materials & interfaces

JF - ACS applied materials & interfaces

ER -

Quantifying Image Charge Effects in Molecular Tunnel Junctions Based on Self-Assembled Monolayers of Substituted Oligophenylene Ethynylene Dithiols

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Keywords

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