Effect on coupling coefficient of diamond-based surface acoustic wave devices using two layers of piezoelectric materials of different widths

With the advent of 5G massive data, it is critical to improve the frequency and bandwidth of surface acoustic wave devices. In this work, ZnO, AlN and LiNbO3 piezoelectric materials were applied to a three-layer structure based on diamond as the substrate. Unlike conventional structures, widths of two piezoelectric materials are different. The electromechanical coupling coefficient based on the ZnO/ZnO/diamond structure can be remarkably improved to 8.26%, while a high frequency of 2 GHz can also be obtained. The structure based on the AlN/AlN/diamond structure is more inclined to obtain a high frequency of 3.76 GHz and an electromechanical coupling coefficient of 4.64%. Rational selection of piezoelectric materials and film thickness of surface acoustic wave devices can achieve different degrees of enhancement of electromechanical coupling coefficients and frequency. Finally, it was found that the larger electric potential on the surface of diamond will result in a larger electromechanical coupling coefficient when the first layer of piezoelectric material is identical. [Display omitted] •Increase the frequency of SAW, which could reach 3.76GHz.•Improve the SAW and electromechanical coupling coefficient, which could reach 8.26%.•Analyze the effect of different materials on SAW performance, such as electromechanical coupling coefficient and phase velocity.