Study of Propagation of Microwave Lamb Waves in a Piezoelectric Layered Structure

We have implemented a 1D and 2D simulation of excitation and propagation of Lamb waves in Al/AlN/(100)-diamond and Al-IDT/AlN/(100)-diamond piezoelectric layered structures (the last in a SAW resonator configuration), respectively. The distribution of elastic displacements in Lamb waves of different orders has been calculated, the mode types have been identified, and the dispersion dependences of the phase velocities have been studied including the excitation at ultrahigh frequencies. The phase velocity values calculated using the 1D and 2D models are in good agreement with those determined experimentally. We have shown that, above a synchronism frequency of an IDT, resonances which occur in these structures, are determined by excitation of Lamb waves in a substrate. The quality factor of these resonances is extremely higher than that on surface acoustic waves. This is confirmed by the experimental data. The amplitude-frequency responses and frequency dependences of the quality factor calculated using the 2D model are in good agreement with the experiment.