Theoretical analysis of acoustoelectrical sensitivity in SAW gas sensors with single and bi-layer structures

The theoretical studies on acoustoelectrical (AE) sensitivity in SAW gas sensors with a single and bi-layer structures were presented. The analysis was based on normalized parameter xi= sigma s\v(0)C(s) (Where: sigma(s) - is the film's electical surface conductivity, v(0)-SAW velocity, C-s - sum of the substrate's and environment's electrical permittivities) which determines the value of AE sensitivity and elemental theory of SAW interactions with semiconductor sensor thin film nanostructures. The electical surface conductivities in the bi-layer structure are correlated by the sigma(s1) = x sigma (s2) dependence, where the x parameter determines how much the electrical conductivity of the first film is bigger than the second one. The investigations revealed that for single and bi-layer sensor structures the maximum value of AE sensitivity was obtained for parametr xi(max) = similar to 0.6 For bi-layer structures this sensitivity is lower. However we also found the positions of the maximum values in function of x design parameter dependently on different values of normalized conductivity of the second film. (C) 2016 Elsevier B.V. All right reserved.