YBCO-FET room temperature ammonia sensor

A FET-ammonia sensor operating at room temperature is reported in this paper. The sensor employs a thin film of semiconducting Y:Ba:Cu:O (YBCO) compound, commonly known as 1-2-3 high temperature superconducting cuprate, as its sensing element. We observed that this material is highly and selectively sensitive to ammonia at and below room temperature. The measurements indicate that the non-amplified signal of the sensor is more than 10 mV for 5 ppm of ammonia. A typical rise time of 24 s and fall time of 250 s is measured at room temperature. The measurements on temperature dependence of sensitivity evince that the sensor signal increases if the operating temperature of the sensor is decreased. The sensor is selectively sensitive to ammonia only and exhibits a non-sensor like behaviour to hydrogen and hydrocarbon based gases. Although the exact mechanisms of gas-sensing properties of cuprates are not known, nevertheless, we tried to explain the observed sensor response to ammonia on the basis of physisorption. The demonstrative results reported here suggest that a room temperature FET ammonia sensor can be realized using semiconducting YBCO as a sensing material for the development of silicon-based integrated smart sensors. (C) 2000 Elsevier Science S.A. All rights reserved.