This paper demonstrates the evaluation and selection of commercially available LiNbOa and LiTaOa single crystals and wafers for surface acoustic wave (SAW) devices using the line-focus-beam ultrasonic material characterization (LFB-UMC) system. This system enables measuring leaky-SAW (LSAW) propagation characteristics precisely and efficiently for a number of specimens. The wafers are prepared from the top, middle, and bottom parts of four 128°YX LiNbOn and seven X-112°Y LiTaOs single crystals. For both series of crystals, the measured LSAW velocities increase from top to bottom in the crystals arid with the increasing crystal growth number. The velocity changes for all wafers are 0.036% for 128°YX LiNbOa and 0,035% for X-112°Y LiTaO3, corresponding to changes of 0.038 mol% and 0.075 mol% in LiO concentration, respectively. Moreover, the inhomogeneity in the first X-112°Y LiTaOs single crystal caused by some undesirable wafer fabrication processes can be detected precisely, although it is difficult for the conventional methods to obtain such information.
|Number of pages
|IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
|Published - 2000 Jul