Development of a SnO2/CuO-coated surface acoustic wave-based H2S sensor with switch-like response and recovery

A new surface acoustic wave (SAW) sensor with switch-like response and recovery was developed for H2S gas sensing, in which, as a sensitive interface material toward H2S, a SnO2/CuO composite film was deposited onto a 147 MHz SAW delay line on 36° YXLiTaO3 substrate by the RF magnetron sputtering technique, and annealed at 450 °C for 2.5 h in the dry air. The adsorption of H2S by the sensitive coating modulates the phase velocity of the acoustic wave due to the mass loading and acoustoelectric effect, thus, the target specific H2S gas can be evaluated by recording the frequency shift of the SAW device. The temperature effect on sensor response characteristics was investigated in temperature range of 70-205 °C, and the optimal working temperature of 160 °C was extracted experimentally, at which, fast response time (55 s) and recovery time (45 s), and larger frequency response of 230 kHz were observed from the fabricated SAW sensor toward H2S with concentration of 20 ppm. Moreover, high sensitivity of 16.9 kHz ppm−1, excellent selectivity, and superior repeatability were observed.