Experimental study of Nonlinearity using Tungsten bottom electrode on SAW device

The study investigated the effect of the hardness and elastic modulus of the IDT electrode material on the nonlinearity generated by the SAW resonator. Nonlinearity was compared between SAW resonators with Ti/AlCu alloy and Tungsten/AlCu alloy IDT electrodes. The Tungsten/AlCu alloy IDT electrode exhibited a superior nonlinearity than Ti/AlCu alloy IDT electrode. Nanoindentation was conducted to evaluate the hardness and the elastic modules of electrode materials. The results showed that Tungsten had an approximately four times higher hardness than Ti and had a 2 times higher elastic module than Ti. The hardness result indicates Tungsten has a larger linear deformation region than Ti. Additionally, FEM simulations showed that Tungsten/AlCu alloy IDT electrode had smaller strains than the Ti/AlCu alloy IDT electrode. The superior nonlinearity of the SAW resonators can be attributed to the high elastic modulus and hardness of tungsten.