Generalized acoustic parameters of non-homogeneous thin films

The transmission line model (TLM), which is based on a one-dimensional electromechanical model of acoustic wave generation and propagation in a multilayer arrangement of piezoelectric and non-piezoelectric layers, is one of the most developed methods for the analysis of the transduction mechanism of acoustic wave sensors. It especially contains the mass sensitivity of quartz crystal resonators known as quartz crystal microbalance (QCM) and the sensitivity of these devices to density and viscosity of a contacting liquid. The acoustic load concept (ALC) applies some approximations to the TLM, which evade the calculation of the admittance spectrum of the coated quartz crystal. Instead, the ALC provides a direct relation between the acoustic load impedance acting at the surface of the quartz crystal and two directly measurable values: the frequency shift and the motional resistance or the Q-factor of the coated resonator. the idea of the generalized acoustic load concept (GALC) is to work with acoustically effective film properties different from the intrinsic material properties or geometric values of the film and to apply these generalized values to the TLM or similar models.