Stability of thiol-based self-assembled monolayer functionalized electrodes in EG-OFET-based applications

Amit Tewari; Kim Björkström; Amir Mohammad Ghafari; Eleonora Macchia; Luisa Torsi; Ronald Österbacka

doi:10.1016/j.flatc.2023.100553

Stability of thiol-based self-assembled monolayer functionalized electrodes in EG-OFET-based applications

Amit Tewari, Kim Björkström, Amir Mohammad Ghafari, Eleonora Macchia, Luisa Torsi, Ronald Österbacka

Electrical Engineering

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

1 Citation (Scopus)

7 Downloads (Pure)

Abstract

The surface passivation of thermally deposited Au using n-alkanethiol self-assembled monolayers (SAMs) as insulating monolayers in electrolyte-gated organic-field effect transistor (EG-OFET) and its impact on EG-OFET operation has been clarified. We used three different n-alkanethiols derivates, namely propanethiol (P-SAM), hexanethiol (H-SAM), and octanethiol (O-SAM), with different chain lengths (C₃, C₆ and C₈). The non-uniform distribution of the used SAMs on the inhomogeneous Au surface significantly affects the net capacitance, i.e., the serial capacitance of the double layer (C_DL) and blocking layer (C_BL) capacitance of the functionalized gate. The SAM-functionalized gates were exposed to cyclic electrical stress (forward and reverse) for 128 cycles with gate voltage (V_G) sweep from 0.1 to −0.4 V at constant drain voltage (V_D = -0.4 V) and compared to a bulk-gold reference gate electrode. The registered transfer curves showed increased drain currents that saturated during prolonged cycling. Two figures of merit, i.e., threshold voltage (V_th) and hysteresis, were extracted from the recorded transfer curves, and their responses were studied separately. We found that both V_th and hysteresis increase with cycling. The change is small but constantly increases for the short-chain P-SAM, while for the longer-chain H- and O-SAM, the initial change is more prominent, reaching saturation after approximately 25 cycles. We have investigated the surface roughness of different gate electrodes through Atomic Force Microscopy (AFM) to confirm the packing density of thiol molecules. We also performed 80 h long-term stability data using cyclic voltammetry measurements for each thiol-functionalized electrode. No signs of desorption could be found, as evidenced by XPS. The results are consistent with previously suggested models for electrical transport across such SAMs, confirming that these monolayers restrict faradic processes at the electrodes by passivating the Au surface.

Original language	English
Article number	100553
Journal	FlatChem
Volume	42
DOIs	https://doi.org/10.1016/j.flatc.2023.100553
Publication status	Published - Nov 2023
Publication type	A1 Journal article-refereed

Funding

The authors acknowledge H2020 – Electronic Smart Systems – SiMBiT: Single-molecule bio-electronic smart system array for clinical testing (Grant agreement ID: 824946), The Academy of Finland through projects #316881 and # 316883, Doctoral Network of Materials Research at Åbo Akademi University, ERC Stg2021: NoOne-A binary sensor with a single-molecule digit to discriminate biofluids enclosing zero or at least one biomarker (GA: 101040383), and Åbo Akademi University CoE “Bioelectronic activation of cell functions” for the financial support. Additionally, the authors would like to thank the Tampere Microscopy Center, Hervanta at Tampere University for accessing the characterization facilities. The authors acknowledge H2020 – Electronic Smart Systems – SiMBiT: Single-molecule bio-electronic smart system array for clinical testing (Grant agreement ID: 824946), The Academy of Finland through projects #316881 and # 316883, Doctoral Network of Materials Research at Åbo Akademi University, ERC Stg2021: NoOne-A binary sensor with a single-molecule digit to discriminate biofluids enclosing zero or at least one biomarker (GA: 101040383), and Åbo Akademi University CoE “Bioelectronic activation of cell functions” for the financial support. Additionally, the authors would like to thank the Tampere Microscopy Center, Hervanta at Tampere University for accessing the characterization facilities.

Keywords

Capacitance
Cyclic Voltammetry
EG-OFET
Functionalization
Self-assembled monolayer
Stabilization

Publication forum classification

Publication forum level 1

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials
Ceramics and Composites
Surfaces, Coatings and Films
Materials Chemistry

Access to Document

10.1016/j.flatc.2023.100553Licence: CC BY

1-s2.0-S2452262723000855-mainFinal published version, 3.23 MBLicence: CC BY

https://urn.fi/URN:NBN:fi:tuni-202310108716Licence: CC BY

Cite this

@article{b43f9580aead4ab8aec56a3e1f20078d,

title = "Stability of thiol-based self-assembled monolayer functionalized electrodes in EG-OFET-based applications",

abstract = "The surface passivation of thermally deposited Au using n-alkanethiol self-assembled monolayers (SAMs) as insulating monolayers in electrolyte-gated organic-field effect transistor (EG-OFET) and its impact on EG-OFET operation has been clarified. We used three different n-alkanethiols derivates, namely propanethiol (P-SAM), hexanethiol (H-SAM), and octanethiol (O-SAM), with different chain lengths (C3, C6 and C8). The non-uniform distribution of the used SAMs on the inhomogeneous Au surface significantly affects the net capacitance, i.e., the serial capacitance of the double layer (CDL) and blocking layer (CBL) capacitance of the functionalized gate. The SAM-functionalized gates were exposed to cyclic electrical stress (forward and reverse) for 128 cycles with gate voltage (VG) sweep from 0.1 to −0.4 V at constant drain voltage (VD = -0.4 V) and compared to a bulk-gold reference gate electrode. The registered transfer curves showed increased drain currents that saturated during prolonged cycling. Two figures of merit, i.e., threshold voltage (Vth) and hysteresis, were extracted from the recorded transfer curves, and their responses were studied separately. We found that both Vth and hysteresis increase with cycling. The change is small but constantly increases for the short-chain P-SAM, while for the longer-chain H- and O-SAM, the initial change is more prominent, reaching saturation after approximately 25 cycles. We have investigated the surface roughness of different gate electrodes through Atomic Force Microscopy (AFM) to confirm the packing density of thiol molecules. We also performed 80 h long-term stability data using cyclic voltammetry measurements for each thiol-functionalized electrode. No signs of desorption could be found, as evidenced by XPS. The results are consistent with previously suggested models for electrical transport across such SAMs, confirming that these monolayers restrict faradic processes at the electrodes by passivating the Au surface.",

keywords = "Capacitance, Cyclic Voltammetry, EG-OFET, Functionalization, Self-assembled monolayer, Stabilization",

author = "Amit Tewari and Kim Bj{\"o}rkstr{\"o}m and Ghafari, {Amir Mohammad} and Eleonora Macchia and Luisa Torsi and Ronald {\"O}sterbacka",

note = "Funding Information: The authors acknowledge H2020 – Electronic Smart Systems – SiMBiT: Single-molecule bio-electronic smart system array for clinical testing (Grant agreement ID: 824946), The Academy of Finland through projects #316881 and # 316883, Doctoral Network of Materials Research at {\AA}bo Akademi University, ERC Stg2021: NoOne-A binary sensor with a single-molecule digit to discriminate biofluids enclosing zero or at least one biomarker (GA: 101040383), and {\AA}bo Akademi University CoE “Bioelectronic activation of cell functions” for the financial support. Additionally, the authors would like to thank the Tampere Microscopy Center, Hervanta at Tampere University for accessing the characterization facilities. Funding Information: The authors acknowledge H2020 – Electronic Smart Systems – SiMBiT: Single-molecule bio-electronic smart system array for clinical testing (Grant agreement ID: 824946), The Academy of Finland through projects #316881 and # 316883, Doctoral Network of Materials Research at {\AA}bo Akademi University, ERC Stg2021: NoOne-A binary sensor with a single-molecule digit to discriminate biofluids enclosing zero or at least one biomarker (GA: 101040383), and {\AA}bo Akademi University CoE “Bioelectronic activation of cell functions” for the financial support. Additionally, the authors would like to thank the Tampere Microscopy Center, Hervanta at Tampere University for accessing the characterization facilities. Publisher Copyright: {\textcopyright} 2023 The Author(s)",

year = "2023",

month = nov,

doi = "10.1016/j.flatc.2023.100553",

language = "English",

volume = "42",

}

TY - JOUR

T1 - Stability of thiol-based self-assembled monolayer functionalized electrodes in EG-OFET-based applications

AU - Tewari, Amit

AU - Björkström, Kim

AU - Ghafari, Amir Mohammad

AU - Macchia, Eleonora

AU - Torsi, Luisa

AU - Österbacka, Ronald

N1 - Funding Information: The authors acknowledge H2020 – Electronic Smart Systems – SiMBiT: Single-molecule bio-electronic smart system array for clinical testing (Grant agreement ID: 824946), The Academy of Finland through projects #316881 and # 316883, Doctoral Network of Materials Research at Åbo Akademi University, ERC Stg2021: NoOne-A binary sensor with a single-molecule digit to discriminate biofluids enclosing zero or at least one biomarker (GA: 101040383), and Åbo Akademi University CoE “Bioelectronic activation of cell functions” for the financial support. Additionally, the authors would like to thank the Tampere Microscopy Center, Hervanta at Tampere University for accessing the characterization facilities. Funding Information: The authors acknowledge H2020 – Electronic Smart Systems – SiMBiT: Single-molecule bio-electronic smart system array for clinical testing (Grant agreement ID: 824946), The Academy of Finland through projects #316881 and # 316883, Doctoral Network of Materials Research at Åbo Akademi University, ERC Stg2021: NoOne-A binary sensor with a single-molecule digit to discriminate biofluids enclosing zero or at least one biomarker (GA: 101040383), and Åbo Akademi University CoE “Bioelectronic activation of cell functions” for the financial support. Additionally, the authors would like to thank the Tampere Microscopy Center, Hervanta at Tampere University for accessing the characterization facilities. Publisher Copyright: © 2023 The Author(s)

PY - 2023/11

Y1 - 2023/11

N2 - The surface passivation of thermally deposited Au using n-alkanethiol self-assembled monolayers (SAMs) as insulating monolayers in electrolyte-gated organic-field effect transistor (EG-OFET) and its impact on EG-OFET operation has been clarified. We used three different n-alkanethiols derivates, namely propanethiol (P-SAM), hexanethiol (H-SAM), and octanethiol (O-SAM), with different chain lengths (C3, C6 and C8). The non-uniform distribution of the used SAMs on the inhomogeneous Au surface significantly affects the net capacitance, i.e., the serial capacitance of the double layer (CDL) and blocking layer (CBL) capacitance of the functionalized gate. The SAM-functionalized gates were exposed to cyclic electrical stress (forward and reverse) for 128 cycles with gate voltage (VG) sweep from 0.1 to −0.4 V at constant drain voltage (VD = -0.4 V) and compared to a bulk-gold reference gate electrode. The registered transfer curves showed increased drain currents that saturated during prolonged cycling. Two figures of merit, i.e., threshold voltage (Vth) and hysteresis, were extracted from the recorded transfer curves, and their responses were studied separately. We found that both Vth and hysteresis increase with cycling. The change is small but constantly increases for the short-chain P-SAM, while for the longer-chain H- and O-SAM, the initial change is more prominent, reaching saturation after approximately 25 cycles. We have investigated the surface roughness of different gate electrodes through Atomic Force Microscopy (AFM) to confirm the packing density of thiol molecules. We also performed 80 h long-term stability data using cyclic voltammetry measurements for each thiol-functionalized electrode. No signs of desorption could be found, as evidenced by XPS. The results are consistent with previously suggested models for electrical transport across such SAMs, confirming that these monolayers restrict faradic processes at the electrodes by passivating the Au surface.

AB - The surface passivation of thermally deposited Au using n-alkanethiol self-assembled monolayers (SAMs) as insulating monolayers in electrolyte-gated organic-field effect transistor (EG-OFET) and its impact on EG-OFET operation has been clarified. We used three different n-alkanethiols derivates, namely propanethiol (P-SAM), hexanethiol (H-SAM), and octanethiol (O-SAM), with different chain lengths (C3, C6 and C8). The non-uniform distribution of the used SAMs on the inhomogeneous Au surface significantly affects the net capacitance, i.e., the serial capacitance of the double layer (CDL) and blocking layer (CBL) capacitance of the functionalized gate. The SAM-functionalized gates were exposed to cyclic electrical stress (forward and reverse) for 128 cycles with gate voltage (VG) sweep from 0.1 to −0.4 V at constant drain voltage (VD = -0.4 V) and compared to a bulk-gold reference gate electrode. The registered transfer curves showed increased drain currents that saturated during prolonged cycling. Two figures of merit, i.e., threshold voltage (Vth) and hysteresis, were extracted from the recorded transfer curves, and their responses were studied separately. We found that both Vth and hysteresis increase with cycling. The change is small but constantly increases for the short-chain P-SAM, while for the longer-chain H- and O-SAM, the initial change is more prominent, reaching saturation after approximately 25 cycles. We have investigated the surface roughness of different gate electrodes through Atomic Force Microscopy (AFM) to confirm the packing density of thiol molecules. We also performed 80 h long-term stability data using cyclic voltammetry measurements for each thiol-functionalized electrode. No signs of desorption could be found, as evidenced by XPS. The results are consistent with previously suggested models for electrical transport across such SAMs, confirming that these monolayers restrict faradic processes at the electrodes by passivating the Au surface.

KW - Capacitance

KW - Cyclic Voltammetry

KW - EG-OFET

KW - Functionalization

KW - Self-assembled monolayer

KW - Stabilization

U2 - 10.1016/j.flatc.2023.100553

DO - 10.1016/j.flatc.2023.100553

M3 - Article

AN - SCOPUS:85171390127

SN - 2452-2627

VL - 42

JO - FlatChem

JF - FlatChem

M1 - 100553

ER -

Stability of thiol-based self-assembled monolayer functionalized electrodes in EG-OFET-based applications

Abstract

Funding

Keywords

Publication forum classification

ASJC Scopus subject areas

Access to Document

Fingerprint

Cite this