Peculiarities of Microwave Lamb Wave Excitation in Composite SAW Resonator Based on Diamond Substrate

We study in detail both experimentally and theoretically Lamb-like wave excitation up to 7.3 GHz in the piezoelectric layered structures “Me-IDT/AlN/(100) diamond” ($\text{Me} =\text{Pt}$, Al) configured as a SAW resonator. Theoretical investigation identifying Lamb wave types by Finite Element Modeling as well as by direct solution of the characteristic equations has been fulfilled. Resonance curves for Lamb-like waves have a higher quality factor $Q$ compared to surface acoustic waves propagating on the same substrates. We observed experimentally an unusual effect of a significant increasing in $Q$-factor of Lamb wave resonance curves with frequency, from a value of 760 at 1.5 GHz to 3,400 at ∼7 GHz. It was shown that the peculiarities of Lamb wave excitation were closely connected with IDT diffraction effects.