LITHIUM TANTALATE SINGLE-CRYSTAL SUBSTRATE AND JOINED SUBSTRATE THEREOF, METHOD FOR MANUFACTURING SAME, AND ELASTIC SURFACE WAVE DEVICE USING JOINED SUBSTRATE

摘要

[Problem] The purpose of the present invention is to provide a lithium tantalate single-crystal substrate having minimal warping, no cracking or defects, better temperature characteristics than the conventional rotated Y-cut LiTaO3 substrate, a large electromechanical coupling coefficient, and also a high Q value in a device. [Solution] This lithium tantalate single-crystal substrate is a LiTaO3 single-crystal substrate in which Li is diffused toward the inside from the surface of a rotated Y-cut LiTaO3 substrate which is 36°-49° Y-cut with a rotated crystal orientation, and has a concentration profile in which the Li concentration is different in the substrate surface and the substrate inside, and the LiTaO3 single-crystal substrate is characterized by being treated so as to be singly polarized, and by having a substantially uniform Li concentration from the substrate surface to a depth of 5-15 times the wavelength of elastic surface waves or leakage elastic surface waves propagated through the LiTaO3 substrate surface.