Rayleigh SAW resonators using gold electrode structure for gas sensor applications in chemically reactive environments

Simple and efficient Rayleigh-SAW two-port resonators on quartz using a corrosion-proof gold-stripe electrode structure are presented. The devices are intended for operation as gas sensors in chemically reactive environments in which the measured gases may attack the electrode structure and destroy the sensor. By carefully selecting the gold film thickness, cavity length and transducer coupling to the load, parasitic bulk wave radiation is minimised and efficient Rayleigh-SAW mode excitation is achieved. Single-mode resonators and two-pole coupled resonator filters in the 400 MHz range demonstrate -7 to -10 dB of unmatched insertion loss and loaded Q values in the 4000-6000 range. Substantial corrosion immunity compared to SAW resonators with aluminium electrodes is demonstrated.