Level repulsion of GHz phononic surface waves in quartz substrate with finite-depth holes

• Level repulsion of gigahertz SAWs in a quartz phononic structure is demonstrated.
• Bandgaps induced by level repulsions of chamfered cylindrical PCs are analyzed.
• Fabrication details of slanted IDTs and submicrometer PCs are given.
• Measured results of the Rayleigh wave bandgaps agreed with numerical predictions.

This paper presents numerical and experimental results on the level repulsion of gigahertz surface acoustic waves in an air/ST-cut quartz phononic structure with finite-depth holes. The colorful dispersion with the parameter of the in-plane (sagittal plane) ratio of polarization was adopted to determine the Rayleigh wave bandgap induced by the level repulsion. The results of numerical analyses showed that the frequency and width of the bandgap induced by the level repulsion strongly depend on the geometry of the air holes in the phononic structure. In the experiment, a pair of slanted interdigital transducers with frequency in the gigahertz range was designed and fabricated to generate and receive broadband Rayleigh waves, whereas the reactive ion etching process with electron-beam lithography was used to fabricate submicrometer phononic structures. The measured results of the bandgap induced by the level repulsion agreed favorably with the numerical prediction.