Features of propagation of surface acoustic waves in two-dimensional phononic crystals on the surface of a lithium niobate crystal

In this paper, we present the design and fabrication of innovative phononic crystals integrated with two sets of interdigital (IDT) electrodes for frequency band selection of surface acoustic waves (SAW). The potential applications of this device include performance improvement of SAW micro-sensors, front-end components in RF circuitries, and directional receptions of high frequency acoustic waves. Analogous to the band-gap generated by photonic crystals, the phononic crystals, two dimensional repetitive structures composed of two different elastic materials, can prohibit the propagation of elastic waves with either specific incident angles or certain bandwidth. In this paper, the prohibited bandwidth has been verified by fabricating the phononic crystals between a micromachined SAW resonator and a receiver. Both the resonator and receiver are composed of IDT electrodes deposited and patterned on a thin piezoelectric layer. To confine the prohibited bandwidth on the order of hundred MHz, the diameter of the circular pores in phononic crystals is designed to be 6 micron and the aspect ratio of each pore is 3:1. To maximize the power transduction from IDT electrodes to SAW, the spacing between two inter-digits is one-fourth the wavelength of SAW. Specifically, the spacing ranges from 3.4 microns to 9.0 microns, depending on the central frequency. Both surface and bulk micromachining are employed and integrated to fabricate the crystals as well as SAW resonator and receiver altogether. Firstly, a 1.5-micron zinc oxide, which provides well-defined central frequency, is sputtered and patterned onto silicon substrate. Second, the IDT electrodes are evaporated and patterned by lift-off technique. Then the exposed silicon substrate is etched using DRIE to generate two dimensional phononic crystals. To tune the prohibited SAW bandwidth, the crystal pores are filled with copper or nickel by electroless plating. The insertion loss of the fabricated devices is characterized and is found to agree with simulation results.

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Two-dimensional phononic crystals: surface acoustic waves

Physica B Condensed Matter ◽

10.1016/s0921-4526(98)01197-1 ◽

1999 ◽

Vol 263-264 ◽

pp. 77-80 ◽

Cited By ~ 14

Author(s):

Yukihiro Tanaka ◽

Shin-ichiro Tamura

Keyword(s):

Acoustic Waves ◽

Surface Acoustic Waves ◽

Phononic Crystals ◽

Two Dimensional

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Bleustein-Gulyaev-Shimizu surface acoustic waves in two-dimensional piezoelectric phononic crystals

IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control ◽

10.1109/tuffc.2006.1642515 ◽

2006 ◽

Vol 53 (6) ◽

pp. 1169-1176 ◽

Cited By ~ 36

Author(s):

Jin-Chen Hsu ◽

Tsung-Tsong Wu

Keyword(s):

Acoustic Waves ◽

Surface Acoustic Waves ◽

Phononic Crystals ◽

Two Dimensional

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Plane and Surface Acoustic Waves Manipulation by Three-Dimensional Composite Phononic Pillars with 3D Bandgap and Defect Analysis

Acoustics ◽

10.3390/acoustics3010004 ◽

2021 ◽

Vol 3 (1) ◽

pp. 25-41

Author(s):

Muhammad ◽

C.W. Lim ◽

Andrew Y. T. Leung

Keyword(s):

Acoustic Waves ◽

Wave Attenuation ◽

Numerical Technique ◽

Surface Acoustic Waves ◽

Three Dimensional ◽

Phononic Crystals ◽

Defect State ◽

Two Dimensional ◽

Defect Analysis ◽

Acoustic Metamaterials

The current century witnessed an overwhelming research interest in phononic crystals (PnCs) and acoustic metamaterials (AMs) research owing to their fantastic properties in manipulating acoustic and elastic waves that are inconceivable from naturally occurring materials. Extensive research literature about the dynamical and mechanical properties of acoustic metamaterials currently exists, and this maturing research field is now finding possible industrial and infrastructural applications. The present study proposes a novel 3D composite multilayered phononic pillars capable of inducing two-dimensional and three-dimensional complete bandgaps (BGs). A phononic structure that consisted of silicon and tungsten layers was subjected to both plane and surface acoustic waves in three-dimensional and two-dimensional periodic systems, respectively. By frequency response study, the wave attenuation, trapping/localization, transmission, and defect analysis was carried out for both plane and surface acoustic waves. In the bandgap, the localized defect state was studied for both plane and surface acoustic waves separately. At the defect state, the localization of both plane and surface acoustic waves was observed. By varying the defect size, the localized frequency can be made tailorable. The study is based on a numerical technique, and it is validated by comparison with a reported theoretical work. The findings may provide a new perspective and insight for the designs and applications of three-dimensional phononic crystals for surface acoustic wave and plane wave manipulation, particularly for energy harvesting, sensing, focusing and waves isolation/attenuation purposes.

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