IEEE Trans Ultrason Ferroelectr Freq Control. 2020 Sep;67(9):1909-1915. doi: 10.1109/TUFFC.2020.2985744. Epub 2020 Apr 6.
A layered structure combining a thin plate of lithium niobate (LN) with a langasite (LGS) substrate was numerically investigated as an advanced substrate material for surface acoustic wave (SAW) devices with improved characteristics, including capability of operating at high temperatures. The longitudinal leaky SAWs (LLSAWs) propagating with negligible attenuation and high velocities up to 6400 m/s were found in LN/LGS using an optimization technique previously applied to the LN/quartz structure. Compared with quartz, the use of LGS as a substrate imposes less constrains on bonding at elevated temperatures for fabrication of a layered structure. Due to the specific acoustic anisotropy of LGS crystals, low-attenuated high-velocity waves exist in a wide range of LGS orientations, including the commercially available SAW cut, when LGS substrate is combined with an LN plate. In the found optimal structures, the electromechanical coupling increased from 5.5% to 14.5%, with increasing LN thickness, making LN/LGS substrate suitable for application in SAW devices with a widely varying bandwidth. In addition, low shear bulk wave velocities in LGS provide a wide spurious-free frequency range in resonators using LLSAW.
一种由铌酸锂（LN）薄片和拉曼纳斯石（LGS）基底组成的层状结构，作为具有改进特性的表面声波（SAW）器件的先进基底材料进行了数值研究，包括在高温下工作的能力。使用先前应用于 LN/石英结构的优化技术，在 LN/LGS 中发现了具有可忽略衰减和高达 6400 m/s 的高速传播的纵向漏声表面波（LLSAW）。与石英相比，使用 LGS 作为基底在高温下进行键合时施加的约束较小，有利于制造层状结构。由于 LGS 晶体的特殊声学各向异性，当 LGS 基底与 LN 板结合时，在包括商业可用的 SAW 切割在内的广泛 LGS 取向范围内存在低衰减高速波。在所发现的最佳结构中，随着 LN 厚度的增加，机电耦合从 5.5%增加到 14.5%，这使得 LN/LGS 基底适合在带宽变化较大的 SAW 器件中应用。此外，LGS 中的低剪切体波速度为使用 LLSAW 的谐振器提供了较宽的无寄生频率范围。
