Analysis of longitudinal leaky surface acoustic waves on LiNbO₃/amorphous layer/quartz structure

Abstract

Recently, bonded structures comprising a quartz substrate and a LiNbO3 (LN) or LiTaO3 thin-plate have been attracting attention as a means of obtaining enhanced properties for surface acoustic wave (SAW) devices. It was reported that the bonding strength was extremely improved by utilizing an amorphous thin film as a middle layer. In this research, the propagation and resonance characteristics of longitudinal leaky SAWs on an amorphous layer inserted to the boundary between an X-cut 36°Y-propagating LN (X36°Y-LN) and X35°Y-quartz were investigated. For the metallized surface of an X36°Y-LN/Al2O3/X35°Y-quartz structure, an attenuation of 0.0001 dB /λ was obtained at an LT thin-plate thickness of 0.072λ (λ: wavelength), which was better than that of an X36°Y-LN/X35°Y-quartz structure. Utilizing a finite element method, we found that the admittance ratio and Q factor for the X36°Y-LN/Al2O3/X35°Y-quartz model were improved owing to the reduction of the leakage due to the shear-vertical particle displacement.

High-performance surface acoustic wave devices using composite substrate structures

“…As a result, it was found that a large K 2 and a small attenuation can be obtained when an X-cut thin plate of LT or LN is bonded to an X-cut quartz. 23,24) However, the plate thickness showing the minimum attenuation was about onethird of the plate thickness showing the maximum K 2 . Resolving this inconsistency is one of the current tasks of the author's research group.…”

“…1(d), a large K 2 , a small attenuation, and a small TCF can be obtained simultaneously for LSAW and LLSAW. [20][21][22][23][24] Some research groups have also investigated structures bonded to a quartz substrate. [25][26][27][28][29][30][31][32][33] In this section, recent results obtained by our group are presented.…”

“…Therefore, SAW propagation structures in which several materials are combined into a layered structure to obtain the desired properties, for instance, a structure including with a temperature-compensated (TC) thin film, have been proposed. [4][5][6][7][8][9][10][11][12][13][14] Furthermore, in recent years, using the dissimilar-material bonding technology developed in the MEMS field, an SAW propagating on bonded structures comprising a piezoelectric crystal thin plate bonded to a support substrate, [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] and a plate wave propagating or a bulk wave vibrating in a piezoelectric crystal thin plate separated from the support substrate have been actively developed. [34][35][36][37][38][39][40][41] In this paper, first, the SAW propagation mode and a method of analyzing the propagation property are briefly introduced.…”

Analysis of longitudinal leaky surface acoustic waves on quartz thin plate bonded to similar-material substrate

“…Recently, many studies have been reported related to high-performance SAW devices. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] The SAW propagation modes suitable for high-frequency devices include a shear horizontal (SH) leaky SAW (LSAW) and a longitudinal LSAW (LLSAW) with relatively high phase velocity. However, an LSAW has inherent attenuation because it propagates while radiating a shear vertical (SV) bulk wave into the substrate.…”

LiNbO3-based sol-gel composite ultrasonic transducer poled at low temperatures

“…LN is a popular piezoelectric material because of relatively high electromechanical coupling coefficient and high Curie temperature, around 1200 °C. [17][18][19][20][21] LN is used as single crystals and it is rare to use it as ceramics due to poling difficulty. In previous studies, Pb(Zr,Ti)O 3 (PZT) and Bi 4 Ti 3 O 12 (BiT) sol-gel solutions were used to produce LN/PZT 13,22,23) and LN/BiT 22,24) sol-gel composite ultrasonic transducers.…”