Layered SAW gas sensor with single-walled carbon nanotube-based nanocomposite coating

A Surface acoustic wave (SAW) sensor using a ZnO guiding layer on 36° Y-cut X-propagation LiTaO3 piezoelectric substrate has been designed and fabricated. Single-walled carbon nanotube (SWCNT)-based nanocomposite coatings have been deposited using the Langmuir–Blodgett technique. The sensor was tested towards H2, NH3, NO2 gases, in the range of 0.030–1%, 30–1000 ppm, 1–10 ppm, respectively. The output signal was the phase of the SAW device, which was monitored using a network analyzer. The developed sensor has a high sensitivity, good repeatability and low detection limit at sub-ppm levels, at room temperature. The experimental results obtained are compared to a theoretical model and the SAW gas sensing mechanisms are discussed with the acoustoelectric effect that appears to be dominant in the SAW response.