SAW modes on ST-X quartz with an AlN layer

Abstract

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. The Y-rotated, X-propagating (ST-X) cut of quartz is used extensively for the development of SAW devices. Besides the commonly used generalized SAW (GSAW) mode, this crystal cut also supports a pseudo-SAW (PSAW) and a high-velocity pseudo-SAW (HVPSAW) mode. In this paper, thin AlN films were sputtered on ST-X quartz to study the SAW modes. The X-ray diffraction (XRD) pattern exhibited that the AlN films were c-axis-oriented structures. The experimental result shoed that the added AlN layer can effectively raise the GSAW and HPSAW velocities.