Sample design in resonant ultrasound spectroscopy for measuring material constants of ScAlN piezoelectric film

Soon after Akiyama et al. demonstrates that Sc-doped aluminum nitride (ScAlN) thin film exhibits extraordinary strong piezoelectricity, the investigation on the full set of material constants of ScAlN film have drawn much attention. The classical measurements of the resonating frequency or the plane-wave velocities require a series of measurements on samples with different geometries, which possibly results in non-self-consistent material constants. The resonant ultrasound spectroscopy (RUS) method can determine full material constants of bulk materials using only one sample. But for the film sputtered on a certain substrate, some elastic constants like C33 and C44 are not sensitive to any resonant frequencies. In this paper, a new method for sample preparation is proposed to construct some new resonant modes related to C33 and C44.