Oblique incidence ultrasonic reflectometry device based on c-axis tilted ScAlN films for evaluating viscoelastic properties of liquids above 100 MHz

The ultrasonic complex reflectometry is a powerful tool for evaluating the viscoelastic properties of small liquid samples. However, the shear mode reflectometry device has not been used at frequencies above 100 MHz because shear-mode piezoelectric films are difficult to obtain at such frequencies. Here, the oblique incidence reflectometry with 143 MHz quasi-shear waves excited by c-axis tilted ScAlN thin films was proposed to realize high-sensitivity evaluation of the viscoelastic properties of liquids. Using the prism type reflectometry MEMS, the shear elasticity and shear viscosity of glycerin solutions were estimated from their complex reflection coefficients.