Shear-horizontal surface acoustic wave characteristics of a (110) ZnO/SiO^sub 2^/Si multilayer structure

Shear-horizontal (SH) surface acoustic wave (SAW) propagation characteristics in IDT/(110)ZnO/SiO2/Si multilayered structure were theoretically investigated using 3-dimensions (3D) finite element analysis (FEA). X-ray diffraction result shows that the prepared ZnO films have preferred (110) orientation with its c-axis parallel to the substrate. 3D FEA results and the out of plane vibration experiment confirmed that SH-SAW was successfully excited in the multilayered structure. The phase velocities Vp, electromechanical coupling coefficients K2, and temperature coefficient of frequency (TCF) dispersion properties of mode 0 were studied considering various thicknesses of ZnO and SiO2 thin films, which were verified by experiments. SiO2 film with a positive TCF not only compensate the negative TCF of the (110) ZnO but also enhance the K2. A large K2 of 3.37 and nearly zero TCF of -0.1 ppm/°C was achieved in SH-SAW device based on IDT/(110)ZnO(2 µm)/SiO2(1 µm)/Si multilayer structure, which is promising for high sensitive and temperature stable bio-sensing application.