2020 Fiscal Year Research-status Report
Development of gas sensors using nanogap electrodes
| Project/Area Number |
20K05263
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
PHAN Trong・Tue 東京工業大学, 科学技術創成研究院, 助教 (40869385)
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| Co-Investigator(Kenkyū-buntansha) |
真島 豊 東京工業大学, 科学技術創成研究院, 教授 (40293071)
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| Project Period (FY) |
2020-04-01 – 2022-03-31
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| Keywords | Gas Sensor / Nanogap Electrodes / Cerium Oxide / Oxygen sensor / Solution-processed |
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| Outline of Annual Research Achievements |
Pt-based nanogap electrodes with a gap separation of below 100 nm were prepared by electron-beam lithography. These electrodes were employed to fabricate nanogap gas sensors by combining solution-processed cerium oxide (CeO2) as the sensing material.
Oxygen gas responses were investigated as functions of the gap separation, ceria film thicknesses, and operating temperatures. The small gap separation below 35 nm enables a fast response time of 10 s at 573 K, which is approximately three orders of magnitude shorter than that exhibited by a microgap sensor under the same measurement conditions.The improved sensor performance is attributed to the extremely small gap separation of the nanogap electrodes; the reduced gap separation facilitates electron hopping conduction in the ceria film.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
For the first year, we have succeeded in fabricating Pt-based nanogap electrodes with various gap separations using electron beam lithography technique. By optimizing fabrication conditions such as resist thickness, dose time, and Pt deposition, the smallest gap separation of around 10 nm has been achieved.
We have also established fabrication process for solgel-derived CeO2 thin-film by a simple spin-coating technique and investigated its structural properties. Then, by combining the solution-processed CeO2 thin-film with the nanogap electrodes platform, we have built an oxygen gas sensor device.
We have tested the response of nanogap gas sensor to oxygen for different gap separations, different CeO2 thickness, and working temperature (up to 573 K). The obtained results match well with the research proposal.
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| Strategy for Future Research Activity |
1) The sensor response is strongly dependent on the working temperature, that is the higher the temperature the better the response. Integration of on-chip microheater for controlling temperature of the nanogap gas sensor (up to 873 K) will be carried out.
2) The fast response might be related to large electrical field available at the ultra-narrow gap, which facilitates electron hopping conduction in CeO2. Thus, effects of bias electric field and the width of electrode on the sensor response will be investigated to find out the optimal condition.
3) Other sensing materials such as (Y,Zr) doped-CeO2 will be also studied for better performance (temperature independence, selectivity)
4) For practical application, operation of the nanogap gas sensor will be test under 1 atm N2
5) Study on nanogap array structure for better stability and reproducibility.
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