Realization of a disturbance ion-suppressed pH sensor for long-term continuous measurement to control ionic species in soil

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K04519
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 21030:Measurement engineering-related
• Research Institution: Shizuoka University
• Principal Investigator: Futagawa Masato 静岡大学, 工学部, 准教授 (90607871)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: ｐＨ / 長期計測 / 土壌直接計測 / ドリフト抑制 / 半導体製造プロセス / ストライプゲート電極

Outline of Final Research Achievements

A new semiconductor type pH sensor with a stripe gate electrode was fabricated. The sensor could prevent interfering ions by apply a voltage. In the first year, a new structure with stripe gate electrodes was fabricated using Poly-Si material. In the second year, the optimal operating conditions for the fabricated sensors were obtained. And, automation of measurements was performed using a microcomputer. In the final year, continuous measurements were performed using the circuits. We confirmed that similar drift suppression could be achieved in acidic, neutral and alkaline solutions. The proposed sensor was able to suppress the amount of drift by a factor of 0.013 and extend the continuous measurement time by a factor of 104.5 compared to the conventional sensor.

Free Research Field

センサ工学

Academic Significance and Societal Importance of the Research Achievements

pHセンサ感応膜のドリフト現象は1970年代より問題点として挙げられており、主に膜質の改善や算術的補正方式がおこなわれてきたが、完全なドリフトの排除には至っていなかった。本研究は、ドリフト現象を電気的に抑制することは世界初の技術であり、Ta2O5やAl2O3などの半導体製造プロセスとしては特殊な材料を使わなくても実施可能な高い独創性と他に類を見ない有意性を要する。本技術は、pHセンサはもとより、有機感応膜を使用する硝酸イオンやカリウムイオンなどにも応用できる技術であり、提案デバイスの活用幅はとても広いといえる。