Phononic Crystal Made of Multilayered Ridges on a Substrate for Rayleigh Waves Manipulation

Mourad Oudich,Bernard Bonello,Frédéric Sarry,Bahram Djafari-Rouhani,Yan Pennec

doi:10.3390/cryst7120372

Abstract

We present a phononic crystal to achieve efficient manipulation of surface acoustic waves (SAW). The structure is made of finite phononic micro-ridges arranged periodically in a substrate surface. Each ridge is constructed by staking silicon and tungsten layers so that it behaves as one-dimensional phononic crystal which exhibits band gaps for elastic waves. The band gap allows the existence of resonance modes where the elastic energy is either confined within units in the free end of the ridge or the ones in contact with the substrate. We show that SAW interaction with localized modes in the free surface of the ridge gives rise to sharp attenuation in the SAW transmission, while the modes confined within the ridge/substrate interface cause broad band attenuations of SAW. Furthermore, we demonstrate that the coupling between the two kinds of modes within the band gap gives high SAW transmission amplitude in the form of Fano-like peaks with high quality factor. The structure could provide an interesting solution for accurate SAW control for sensing applications, for instance.

Highlights

There have been numerous works and investigations on phononic crystals (PCs), as they provide the solution for acoustic and elastic wave control and dispersion manipulation
The surface acoustic waves (SAW) interaction with these modes results in a sharp decay of the SAW amplitude in the form of high QF dips. Another family of confined modes can be created inside the band gap where the elastic energy is confined within the first layers of the ridge in contact with the substrate surface
The excitation of these modes by SAW causes a broad decay of the SAW amplitude in a relatively

Summary

Introduction

There have been numerous works and investigations on phononic crystals (PCs), as they provide the solution for acoustic and elastic wave control and dispersion manipulation. Pennec et al [7,27] and Wu et al [28,29] proposed a pillar based plate by which they showed the arising of local resonance BG (LRBG) created by the resonances of the pillars which couple with the Lamb waves in the band structure. Some of theband modes appear the modes orange shaded corresponds to the phononic ridge substrate in the They canregion only becannot confined in specific of the ridge, will band gap or BG1. 2b, where the top layers display mode denoted T, depicted in the SAW band structure of Figure 2b, where the top Si/W layers display flexural vibration.

We can frequencies in the case of isolated as ridges presented

We can theband defect modes

SAW a Phononic

SAW Transmission through a Phononic Ridge

Findings

Conclusions