Finite element analysis and experimental study of surface acoustic wave propagation through two-dimensional pillar-based surface phononic crystal

Highly confined Love modes are demonstrated in a phononic crystal based on a square array of etched holes in SiO 2 deposited on the ST-cut quartz. An optimal choice of the geometrical parameters contributes to a wide stop-band for shear waves' modes. The introduction of a defect by removing lines of holes leads to the nearly flat modes within the band gap and consequently paves the way to implement advanced designs of electroacoustic filters and high-performance cavity resonators. The calculations are based on the finite element method in considering the elastic and piezoelectric properties of the materials. Interdigital transducers are employed to measure the transmission spectra. The geometrical parameters enabling the appearance of confined cavity modes within the band gap and the efficiency of the electric excitation were investigated.

Section: Ned =supporting

confidence: 61%

Highly confined Love waves modes by defect states in a holey SiO2/quartz phononic crystal

Liu

Talbi

Pernod

et al. 2018

“…22,23 The published studies show that the filling factor, the ratio of the slab thickness to the lattice period, and the height of the pillar are the key parameters for the existence of complete bandgaps. 24,25 When the substrate's surface acoustic modes strongly couple to the periodic overlayer, the SAW will evolve into a pseudo-SAW which is partially localized in the nanostructures and radiates mechanical energy into the substrate due to the scattering introduced by the periodic overlayer. 26,27 Basic surface modes can be recognized due to their relatively lower velocity compared to bulk wave's in solids in some situations.…”

Section: Introductionmentioning

confidence: 99%

Finite element analysis of surface modes in phononic crystal waveguides

Guo

Schubert

Dekorsy

2016

The study of surface modes in phononic crystal waveguides in the hypersonic regime is a burgeoning field with a large number of possible applications. By using the finite element method, the band structure and the corresponding transmission spectrum of surface acoustic waves in phononic crystal waveguides generated by line defects in a silicon pillar-substrate system were calculated and investigated. The bandgaps are caused by the hybridization effect of band branches induced by local resonances and propagating modes in the substrate. By changing the sizes of selected pillars in the phononic crystal waveguides, the corresponding bands shift and localized modes emerge due to the local resonance effect induced by the pillars. This effect offers further possibilities for tailoring the propagation and filtering of elastic waves. The presented results have implications for the engineering of phonon dynamics in phononic nanostructures.

“…The existence of band-gaps in electroacoustic devices combined with phononic structures has been demonstrated both theoretically and experimentally. [12][13][14][15][16][17][18][19][20][21][22] The control of propagating waves can be achieved by modifying portions of the phononic structure to induce a line or point defect state. The acoustic energy with frequencies in the band gaps may be localized in the defect and therefore the propagation can be engineered.…”

Section: Introductionmentioning

confidence: 99%

Highly confined radial contour modes in phononic crystal plate based on pillars with cap layers

Moutaouekkil

Talbi

Boudouti³

et al. 2019

Self Cite

We investigate highly confined and isolated surface modes in a phononic crystal plate based on pillars with cap layers. The structure is made of a thin membrane supporting periodic pillars each composed of one cylinder surmounted by a disk shaped cap layer. An optimal choice of the geometrical parameters and material composition allows the structure to support isolated radial contour modes confined in the cap layer. In this study, we consider diamond and gold (Au) as the pillar and cap layers, respectively, and aluminum nitride as a thin membrane owing to the strong contrast in their elastic and density properties and to their compatibility with the integrated circuit technology and microwave electroacoustic devices. The phononic crystal based on diamond pillars allows us to induce a wide stop band frequency, and the addition of the Au disk shaped layer on diamond pillars enables us to introduce flat modes within the bandgap. We demonstrate that one can optimize the flat mode frequencies by varying the geometrical parameters of the Au cap layer. The quality factor (Q) of a cavity resonator composed of one line gold/diamond pillar surrounded by an array of diamond pillars on both sides has been investigated. These results clearly show that, using this design approach, one can (i) reduce the acoustic energy leakage out of the resonator and (ii) optimize the cavity resonator’s Q factor by varying only the geometrical parameters of the gold cap layer. The proposed design provides a promising solution for advanced signal processing and sensing applications.