Characterization of AlN Films on Y-128° LiNbO3 by Surface Acoustic Wave Measurement

Abstract

Y-128° LiNbO3 is used extensively for the development of surface acoustic wave (SAW) devices. AlN thin films are an attractive material that have some excellent characteristics, such as high surface acoustic wave (SAW) velocity, piezoelectricity, high-temperature stability, and stable chemical properties. In this research, AlN films were sputtered on Y-128° LiNbO3 to yield a new piezoelectric substrate for SAW devices. The X-ray diffraction (XRD) method and SAW measurement were used to evaluate the material and acoustic properties of this structure. The experimental results exhibited that highly c-axis-oriented AlN films were prepared on Y-128° LiNbO3. AlN films on Y-128° LiNbO3 can effectively enhance the SAW velocity and improve the poor temperature stability, but reduce the electromechanical coupling coefficient (k2) values. As the ratio (film-thickness/acoustic-wavelength) increased, the SAW velocities and the temperature coefficient of frequency (TCF) all increased, but the electromechanical coupling coefficient (k2) values decreased.