Finite element analysis of surface elastic waveguide based on pyramidal phononic crystal

In this paper, a pyramidal phononic crystal waveguide, deposited on a thick substrate made of silicon, is studied. The pillars are arranged in a square array on the top surface of the substrate. By using the finite element method, the surface modes are investigated, and the band structures of the surface acoustic waves and the corresponding transmission spectrum are calculated, to study the effect of local resonance of the pyramidal pillars on the band gap. The pyramidal pillars have a rising mass density from the top surface of the pyramid, where the elastic energy can be well confined within. This type of phononic crystals offers further possibilities for filtering and guiding of elastic waves in nanostructures, which can be used in nanoelectromechanical and microelectromechanical engineering systems.