Novel scheme to improve SnO2/SAW sensor performance for NO2 gas by detuning the sensor oscillator frequency

A new method has been devised for obtaining fast NO2 gas sensing characteristics by using detuned SnO2/SAW sensor oscillator. The deposited SnO2 thin films were polycrystalline showing XRD reflections corresponding to (1 0 1) and (2 1 1) planes of rutile structure. The frequency of the sensor remained tuned for SnO2 layer of small thickness (< 90 nm), and sensing response was moderate (< 140 kHz) with relatively slow response time and recovery time. However with increase in thickness (≥ 90 nm), the frequency of SAW sensor detuned resulting in enhanced sensing response (≥ 16 MHz) along with fast response time and recovery time. Independent experiments confirmed the change in elasticity of the sensing layer as the dominant sensing mechanism for SnO2/SAW sensor towards NO2 gas.