Characteristics of leaky surface acoustic waves propagating along liquid/layered-substrates and their application to liquid sensor

We propose SiO₂ (fused silica)/(36°rot.Y-X)LiNbO ₃ substrate for a viscosity sensor, in which the shear horizontal (SH) component becomes larger than that of the case without SiO₂. For glycerin/SiO₂ (40 μm)/LiNbO₃ the loss due to the viscosity of glycerin is four times larger than that for glycerin/LiNbO₃ (30 MHz). Moreover, we show that the SiO₂/(128°rot.Y-X)LiNbO₃ structure is available as a liquid sensor, although the LiNbO₃ substrate (128°rot.Y cut) itself has a small SH component. The origin of the large SH component in the layered substrates is discussed on the basis of the boundary conditions at the interface