An activation process for increased sensitivity of a SAW gas microsensor

A procedure for increasing the response of a SAW (surface acoustic wave) H₂S sensor using WO₃ as the sensing film is described. When the devices are heated to high temperatures, the film undergoes a structural phase change which significantly increases the film´s sensitivity to H₂S. This activation effect can be seen by monitoring the sheet conductivity of the film during the activation procedure. Sample results illustrate the increased conductivity changes in the film when exposed to H₂S as well as the effect that this conductivity change has on the attenuation of a SAW sensor. The increased change in sheet conductivity corresponds to an increased change in SAW velocity and attenuation, allowing significantly lower concentrations of H₂S to be detected than with the unactivated film