Radio frequency impedance matching for SAW devices on zinc oxide and lithium niobate

Finite element methods were used to obtain the electromechanical coupling factor and impedance of interdigital transducers on ZnO/Si multilayers & singe crystal 128 degree XY rotated X directed LiNbO3. The impedance was shown to be lower than expected using FEM simulations, indicating a possible impedance mismatch of the IDT with the peripheral circuit of the measurement instrument. Possible solutions were investigated, such as reducing the number of IDT finger pairs, providing a better match in the radio frequency regime. Furthermore, electrode loading of the substrate has been identified as a cause of unwanted reflections in surface acoustic wave devices, and possible mitigation strategies are discussed.