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Multi-stack insulator to minimise threshold voltage drift in ZnO FET sensors operating in ionic solutions

Multi-stack insulator to minimise threshold voltage drift in ZnO FET sensors operating in ionic solutions
Multi-stack insulator to minimise threshold voltage drift in ZnO FET sensors operating in ionic solutions
FET biosensors operating in an electrolyte experience a monotonic, temporal and relatively slow change in threshold voltage caused by the hydration of the insulator layer between the electrolyte and the FET's channel. Minimising this temporal change in threshold voltage is critical as, over time, the drain current of n-channel FETs decreases, making it difficult to distinguish between the signal generated in response to analyte - receptor binding events and the background noise generated by the electrolyte and the FET biosensor. While Rapid Thermal Annealing of the insulator layer is known to diminish threshold voltage drift and its negative effects, it is not compatible with a low temperature fabrication process of 200 °C. Our low temperature approach to minimising threshold voltage drift involves depositing a tri-layer insulator stack, consisting of a layer of HfO2 between two Al2O3 layers. Wetting ZnO NWFETs with PBS (10 mM phosphate, 150 mM KCl, pH 7.4) for an hour, showed that ZnO NWFETs with a stack insulator layer experienced a much smaller threshold voltage and drain current drift (100 mV, 0.064 nA) than ZnO NWFETs with a single material insulator layer (≥4300mV, 2.72 nA), Aluminium oxide in this case. Having established the resilience enhancing properties of the stack insulator layer on FETs operating in electrolytes of physiological relevant ionic concentrations; ZnO NWFETs with a stack insulator layer were shown to be capable of detecting the presence of the miDNA-21 strands. This, in effect, paves the way for miRNA sensing experiments in the near future and for exploring the potential of ZnO NWFETs as a diagnostic tool.
0167-9317
Akrofi, Joshua, Daniel
5022b800-8f9b-4737-85cf-1690b9b1bd61
Ebert, Martin
1a8f1756-d724-4b44-8504-c01f8dc7aa50
Reynolds, Jamie Dean
96faa744-02ee-458c-8e48-953ea9e54afe
Sun, Kai
b7c648a3-7be8-4613-9d4d-1bf937fb487b
Hu, Ruoyu
a69beac6-ede8-4fd3-8a4d-858dc531bc46
De Planque, Maurits
a1d33d13-f516-44fb-8d2c-c51d18bc21ba
Chong, Harold
795aa67f-29e5-480f-b1bc-9bd5c0d558e1
Akrofi, Joshua, Daniel
5022b800-8f9b-4737-85cf-1690b9b1bd61
Ebert, Martin
1a8f1756-d724-4b44-8504-c01f8dc7aa50
Reynolds, Jamie Dean
96faa744-02ee-458c-8e48-953ea9e54afe
Sun, Kai
b7c648a3-7be8-4613-9d4d-1bf937fb487b
Hu, Ruoyu
a69beac6-ede8-4fd3-8a4d-858dc531bc46
De Planque, Maurits
a1d33d13-f516-44fb-8d2c-c51d18bc21ba
Chong, Harold
795aa67f-29e5-480f-b1bc-9bd5c0d558e1

Akrofi, Joshua, Daniel, Ebert, Martin, Reynolds, Jamie Dean, Sun, Kai, Hu, Ruoyu, De Planque, Maurits and Chong, Harold (2020) Multi-stack insulator to minimise threshold voltage drift in ZnO FET sensors operating in ionic solutions. Microelectronic Engineering. (doi:10.1016/j.mee.2020.111348).

Record type: Article

Abstract

FET biosensors operating in an electrolyte experience a monotonic, temporal and relatively slow change in threshold voltage caused by the hydration of the insulator layer between the electrolyte and the FET's channel. Minimising this temporal change in threshold voltage is critical as, over time, the drain current of n-channel FETs decreases, making it difficult to distinguish between the signal generated in response to analyte - receptor binding events and the background noise generated by the electrolyte and the FET biosensor. While Rapid Thermal Annealing of the insulator layer is known to diminish threshold voltage drift and its negative effects, it is not compatible with a low temperature fabrication process of 200 °C. Our low temperature approach to minimising threshold voltage drift involves depositing a tri-layer insulator stack, consisting of a layer of HfO2 between two Al2O3 layers. Wetting ZnO NWFETs with PBS (10 mM phosphate, 150 mM KCl, pH 7.4) for an hour, showed that ZnO NWFETs with a stack insulator layer experienced a much smaller threshold voltage and drain current drift (100 mV, 0.064 nA) than ZnO NWFETs with a single material insulator layer (≥4300mV, 2.72 nA), Aluminium oxide in this case. Having established the resilience enhancing properties of the stack insulator layer on FETs operating in electrolytes of physiological relevant ionic concentrations; ZnO NWFETs with a stack insulator layer were shown to be capable of detecting the presence of the miDNA-21 strands. This, in effect, paves the way for miRNA sensing experiments in the near future and for exploring the potential of ZnO NWFETs as a diagnostic tool.

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Multi-stack insulator to minimise threshold voltage drift in ZnO FET sensors operating in ionic solutions - Accepted Manuscript
Restricted to Repository staff only until 18 May 2021.
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Submitted date: 5 May 2020
Accepted/In Press date: 12 May 2020
e-pub ahead of print date: 18 May 2020

Identifiers

Local EPrints ID: 440984
URI: http://eprints.soton.ac.uk/id/eprint/440984
ISSN: 0167-9317
PURE UUID: 4b1fc702-fba0-4764-a38d-34e8a2521274
ORCID for Jamie Dean Reynolds: ORCID iD orcid.org/0000-0002-0072-0134
ORCID for Maurits De Planque: ORCID iD orcid.org/0000-0002-8787-0513
ORCID for Harold Chong: ORCID iD orcid.org/0000-0002-7110-5761

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Date deposited: 26 May 2020 16:32
Last modified: 27 May 2020 00:33

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Contributors

Author: Joshua, Daniel Akrofi
Author: Martin Ebert
Author: Jamie Dean Reynolds ORCID iD
Author: Kai Sun
Author: Ruoyu Hu
Author: Maurits De Planque ORCID iD
Author: Harold Chong ORCID iD

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