The influence of the conducting film on the characteristics of the lateral electric field excited piezoelectric resonator

The effect of a thin layer with the finite surface conductivity located near the lateral electric field excited resonator on its characteristics is studied theoretically and experimentally. It has been shown that for the fixed distance between the free side of the resonator and conducting layer with increasing the surface conductivity of the layer the resonant frequency of the parallel resonance remains initially practically constant, then sharply decreases in a certain range and then insignificantly changes. For the fixed value of the layer conductivity the parallel resonant frequency increases at the increase in the gap between the resonator and layer and then achieves the saturation. The maximum change in the frequency of the parallel resonance corresponds to a zero gap when the layer conductivity varies over the wide range is equal to ∼1%. The frequency of the series resonance decreases only by ∼0.08% due to the change in the layer conductivity. The obtained results may be useful for the development of the gas sensors based on the lateral electric field excited piezoelectric resonator conjugated to the gas sensitive film, the conductivity of which changes in the presence of the given gas.