Q-Factor Enhancement of Coupling Bragg and Local Resonance Band Gaps in Single-Phase Phononic Crystals for TPOS MEMS Resonator

Abstract

This paper presents a type of single-phase double “I” hole phononic crystal (DIH-PnC) structure, which is formed by vertically intersecting double “I” holes. By using the finite element method, the complex energy band curve, special point mode shapes, and different delay lines were calculated. Numerical results showed that DIH-PnC yielded ultra-wide band gaps with strong attenuation. The formation mechanism is attributed to the Bragg-coupled local resonance mechanism. The effects of the pore width in DIH-PnC on the band gaps were further explored numerically. Significantly, as the pore width variable, the position of the local resonance natural frequency could be modulated, and this enabled the coupling between the local resonance and the Bragg mechanism. Subsequently, we introduced this DIH-PnC into the thin-film piezoelectric-on-silicon (TPOS) resonator. The results illustrated that the anchor loss quality factor (Qanc) of the DIH-PnC resonator was 20,425.1% higher than that of the conventional resonator and 3762.3% higher than the Qanc of the cross-like holey PnC resonator. In addition, the effect of periodic array numbers on Qanc was researched. When the Qanc reached 1.12 × 106, the number of the period array in DIH-PnC only needed to be 1/6 compared with cross-like holey PnC. Adopting the PnC based on the coupling Bragg and local resonance band gaps had a good effect on improving the Qanc of the resonator.

H-Shaped Radial Phononic Crystal for High-Quality Factor on Lamb Wave Resonators

“…Pandey et al designed a mesa around the resonator to reflect the elastic energy back to the resonator [ 18 ]. Using the band gap characteristics of phononic crystals (PCs) to suppress the anchor loss has attracted the attention of researchers [ 3 , 11 , 15 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ]. For example, Zhu et al used a two-dimensional stomatal PCs unit cell to increase the Q to twice the original [ 11 ].…”

“…Ardito et al used a one-dimensional PCs structure to increase the Q by several times [ 24 ]. Other shapes, such as rings [ 27 ], cross-like holes [ 13 ], fractals [ 14 ], Spider Web-Likes [ 15 ], cross-section connections [ 25 ], double “I” holes [ 26 ], and snowflakes [ 28 ] have also been reported. At present, Yinjie Tong has increased the Q of Pillar-Based PCs by 54% in the UHF range [ 3 ].…”

“…Shi et al designed different two-dimensional radial periodic structures to achieve low-frequency band gaps [ 34 ]. The usual design for one-dimensional PCs is to arrange them on the LWR support tether or in a two-dimensional arrangement on the anchor [ 15 , 16 , 19 , 22 , 25 , 26 , 27 , 35 , 36 , 37 , 38 , 39 ]. In the case of one-dimensional PCs, they are often arranged periodically along the x -axis on the support tether [ 16 , 22 , 35 , 36 , 37 , 38 , 39 ].…”

“…Therefore, one-dimensional PCs can effectively block the propagation of sound waves only by satisfying the directional band gap on the Г-X, but they also require a longer support tether to arrange PCs. Two-dimensional PCs are often arranged periodically on the anchor along the x -axis and y -axis [ 15 , 19 , 22 , 25 , 26 , 27 , 35 , 38 ]. Due to the arrangement of two-dimensional PCs, to effectively block the propagation of acoustic waves it is necessary to have directional band gaps along the Г-X, X-M, and M-Г directions of the irreducible Brillouin zone to achieve omnidirectional band gaps.…”

Multi-Material Radial Phononic Crystals to Improve the Quality Factor of Piezoelectric MEMS Resonators

“…Workie et al studied a prism-shaped PnC and found that the unloaded quality factor (Q u ) of a traditional resonator was increased by 1.7 times (for a butterfly rounded-edge resonant structure), 2.78 times (for a PnC deployed on the tether), and 2.8 times (for a PnC deployed on the anchor), respectively [ 13 ]. In 2022, Li et al investigated a double “I” -hole PnC, and the results showed that the Q anchor of the resonator was 20,425.1% higher than that of a traditional resonator [ 14 ]. In 2023, Awad et al designed a reem-shaped PnC and deployed it on the anchored boundary of a resonator, resulting in an increase of 33.3 times in the Q anchor value and 1.2 times in the Q u value, respectively [ 15 ].…”