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Sensing performance of nanocrystalline graphite based humidity sensors

Sensing performance of nanocrystalline graphite based humidity sensors
Sensing performance of nanocrystalline graphite based humidity sensors
Environmental sensors play a crucial role in a wide range of applications. Amongst them, humidity sensors that are stable and operational in harsh environments are incredibly important for process control and monitoring. Nanocrystalline graphite (NCG) is a type of carbon-based thin film material. Previous work has shown that NCG has excellent mechanical properties and is able to withstand high radiation doses. The granular structure of the NCG film makes it a good candidate for humidity sensing as the film consists of conductive graphitic grains with a high density of sp2 bonds and amorphous grain boundaries with high resistivity, adsorption of water molecule onto the film forms conductive pathways between grains through the Grotthuss mechanism which lowers the resistance of the film by a measurable amount. Here we report for the first time, a working humidity sensor with linear response, fabricated using NCG as the sensing material for harsh, real-world environments, which include exposure to weak acids via rainfall, UV radiation, mechanical wear, and high humidity environments. The calculated sensitivity of the best-fabricated sensor is S = 0.0334%, with a maximum resistance change of -4.4 kOhms, over the range of 15% RH to 85% RH. The response time of the sensor is 20ms with the current measurement setup. The baseline resistance value of the sensor at 15% RH is 210 kOhms. The sensor has the potential to be used as a humidity sensor for harsh environments due to the chemical, thermal and mechanical stability of the NCG film.
Nanocrystalline Graphite,, PECVD,, Humidity Sensors, Harsh environment
1530-437X
5421-5428
Ling, Ting Yang
67472eb1-3e63-41c6-8435-d6bc5b0b4f78
Pu, Suan-Hui
8b46b970-56fd-4a4e-8688-28668f648f43
Fishlock, Sam
b35c425e-91f5-40a1-b3a7-d2939463fb19
Reynolds, Jamie Dean
96faa744-02ee-458c-8e48-953ea9e54afe
Chong, Harold
795aa67f-29e5-480f-b1bc-9bd5c0d558e1
Ling, Ting Yang
67472eb1-3e63-41c6-8435-d6bc5b0b4f78
Pu, Suan-Hui
8b46b970-56fd-4a4e-8688-28668f648f43
Fishlock, Sam
b35c425e-91f5-40a1-b3a7-d2939463fb19
Reynolds, Jamie Dean
96faa744-02ee-458c-8e48-953ea9e54afe
Chong, Harold
795aa67f-29e5-480f-b1bc-9bd5c0d558e1

Ling, Ting Yang, Pu, Suan-Hui, Fishlock, Sam, Reynolds, Jamie Dean and Chong, Harold (2019) Sensing performance of nanocrystalline graphite based humidity sensors. IEEE Sensors Journal, 19 (14), 5421-5428. (doi:10.1109/JSEN.2019.2905719).

Record type: Article

Abstract

Environmental sensors play a crucial role in a wide range of applications. Amongst them, humidity sensors that are stable and operational in harsh environments are incredibly important for process control and monitoring. Nanocrystalline graphite (NCG) is a type of carbon-based thin film material. Previous work has shown that NCG has excellent mechanical properties and is able to withstand high radiation doses. The granular structure of the NCG film makes it a good candidate for humidity sensing as the film consists of conductive graphitic grains with a high density of sp2 bonds and amorphous grain boundaries with high resistivity, adsorption of water molecule onto the film forms conductive pathways between grains through the Grotthuss mechanism which lowers the resistance of the film by a measurable amount. Here we report for the first time, a working humidity sensor with linear response, fabricated using NCG as the sensing material for harsh, real-world environments, which include exposure to weak acids via rainfall, UV radiation, mechanical wear, and high humidity environments. The calculated sensitivity of the best-fabricated sensor is S = 0.0334%, with a maximum resistance change of -4.4 kOhms, over the range of 15% RH to 85% RH. The response time of the sensor is 20ms with the current measurement setup. The baseline resistance value of the sensor at 15% RH is 210 kOhms. The sensor has the potential to be used as a humidity sensor for harsh environments due to the chemical, thermal and mechanical stability of the NCG film.

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IEEE_HUMIDITY SENSOR_PRINTREADY - Accepted Manuscript
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More information

Accepted/In Press date: 1 March 2019
e-pub ahead of print date: 18 March 2019
Published date: 15 July 2019
Keywords: Nanocrystalline Graphite,, PECVD,, Humidity Sensors, Harsh environment

Identifiers

Local EPrints ID: 429967
URI: http://eprints.soton.ac.uk/id/eprint/429967
ISSN: 1530-437X
PURE UUID: aeb605e6-8c0c-4c30-bef8-409997b5c966
ORCID for Suan-Hui Pu: ORCID iD orcid.org/0000-0002-3335-8880
ORCID for Jamie Dean Reynolds: ORCID iD orcid.org/0000-0002-0072-0134
ORCID for Harold Chong: ORCID iD orcid.org/0000-0002-7110-5761

Catalogue record

Date deposited: 09 Apr 2019 16:30
Last modified: 03 Sep 2019 00:35

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Contributors

Author: Ting Yang Ling
Author: Suan-Hui Pu ORCID iD
Author: Sam Fishlock
Author: Jamie Dean Reynolds ORCID iD
Author: Harold Chong ORCID iD

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