Propagation characteristics of longitudinal-type leaky surface acoustic wave on layered structure consisting of ScxAl1−xN film/LiNbO3substrate

In this paper, we present hetero acoustic layer (HAL) structures based on ScAlN thin films with a c-axis tilt angle. The surface acoustic wave (SAW) excitation modes and their propagation characteristics for different Euler angles (0°, θ, ψ) of the ScAlN thin film are analyzed using the finite element method. We find that the acoustic field distribution of HAL structures can be adjusted by rotating their Euler angles and that normal SAWs are suppressed; however, leaky SAWs (LSAWs) with significantly improved electromechanical coupling coefficients (K 2) are excited. A maximum K 2 of 14% can be obtained for shear horizontal (SH)-type LSAWs, which is almost 7 times larger than that of the previously reported normal SAW Sezawa mode. Moreover, the optimized HAL structure consisting of (0°, 90°, 60°) ScAlN thin film/SiO2/AlN/Si simultaneously possesses a larger K 2, a wider bandwidth, and a higher Q value, which is promising for the design and application of wideband SAW devices with high performance.

Section: Introductionmentioning

confidence: 99%

Highly coupled leaky surface acoustic wave on hetero acoustic layer structures based on ScAlN thin films with a c-axis tilt angle

Liu

Zhang

Zhao

et al. 2021

“…To increase the frequency of SAW resonators, the utilization of longitudinal leaky SAWs (LLSAWs) with a phase velocity of 1.5-2 times that of conventional LSAWs has been studied. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] For example, our research group has reported that, by bonding a piezoelectric LiTaO 3 (LT) or LiNbO 3 (LN) thin plate, having a thickness of less than one wavelength (1 λ), to a high-phase velocity support substrate such as quartz (Qz), LLSAWs with a large Q and K 2 of 2-3 times of that of a single LT or LN can be produced owing to a strong concentration of particle displacement in the thin plate. 9,[12][13][14][15] Several research groups, including ours, have reported that bonded structures comprising an LT or LN thin plate and Qz support substrate exhibit high-performance properties with wider FBW, higher Q factor, and better temperature coefficient of frequency than those in the single substrate for LSAWs.…”

Section: Introductionmentioning

confidence: 99%

Analysis of surface acoustic wave resonance properties on piezoelectric substrates with periodic voids

Suzuki

Kakio

2023

Self Cite

The resonance properties of leaky surface acoustic waves (LSAWs) and longitudinal LSAWs (LLSAWs) on bonded structures consisting of a LiNbO3 (LN) thin plate and a support substrate, with periodic voids exhibiting a rectangular cross-section, were simulated using the finite element method. The voids were placed below the electrode at the boundary between the LN thin plate and support substrate and the same pitch and period as the electrode. LN, quartz, glass, or Si were used as support substrates. Simulations revealed that by introducing periodic voids, resonance properties similar to those of the SH0-mode plate and S0-mode Lamb waves can be obtained. The values of the simulated fractional bandwidths of approximately 13 and 18% were found for LSAW and LLSAW, respectively, when the ratio of the width of the void to the pitch of the electrode was 0.7.

“…Previously, we found that attenuation in LLSAWs can be reduced by loading high-velocity AlN or ScAlN polycrystalline films on piezoelectric substrates. [3][4][5][6][7] However, the K 2 in these layered structures was significantly decreased. On the other hand, we reported that LSAW and LLSAW devices with piezoelectric thin plates bonded to high-velocity substrates (quartz and sapphire) have a high K 2 and high Q factor.…”

Section: Introductionmentioning

confidence: 99%

“…Since then, several researchers have studied the characteristics of ScAlN film bulk acoustic wave (BAW) resonators [14][15][16][17][18][19] and ScAlN film SAW resonators. 6,20,21) The electromechanical coupling coefficient of an AlN-based film BAW resonator is dramatically increased by heavily doping the AlN film with Sc. 19) SAW resonators consisting of a ScAlN layer/SiC substrate reported by Ref.…”

Section: Introductionmentioning

confidence: 99%

“…Our group also theoretically demonstrated that the K 2 of LLSAWs propagating on a c-axis parallel Sc 0.4 Al 0.6 N layer/X-cut 36 °Y propagation LiNbO 3 (X36°Y LN) substrate is approximately 1.4 times higher than that of X36°Y LN. 6) From these previous studies on layered structure LLSAW devices and ScAlN film resonators, layered structure LLSAW devices with a high-piezoelectric ScAlN layer/high-velocity sapphire or quartz substrate are expected to have a high phase velocity, high K 2 and high Q factor. We have reported the theoretical analysis of LLSAWs on ScAlN layer/sapphire and quartz.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Analysis of longitudinal leaky surface acoustic wave propagation characteristics on a piezoelectric ScAlN layer/sapphire or quartz substrate

Suzuki

Sawada

Kakio

2019

Longitudinal leaky surface acoustic wave (LLSAW) modes with a high phase velocity are suitable for high-frequency SAW filter applications. However, their attenuation is higher than that of other SAW modes, causing a small Q factor. On the other hand, a low attenuation and high coupling factor K2 in LLSAWs on a piezoelectric thin plate/high-velocity sapphire or quartz substrate have been demonstrated theoretically and experimentally. We expected that LLSAWs propagating on a highly piezoelectric ScAlN layer/sapphire or quartz substrate also have a high phase velocity, high K2 and low attenuation. In this study, the characteristics of LLSAWs on ScAlN layer/sapphire or quartz substrates were theoretically investigated. The cut angle and SAW propagation direction of quartz substrates strongly affect the attenuation of LLSAWs on the layered structure. We found that a LLSAW resonator with (0° 90° 90°) Sc0.4Al0.6N layer/X-cut 30° Y propagation quartz has a high Q factor and high K2, which is adequate for SAW filter applications.