Experimental and theoretical investigation for temperature characteristics and propagation losses of SAWs on SiO2/Al/LiTaO3

Improvement of temperature coefficients of frequency (TCFs) for LiTaO₃ substrate was investigated. SAW resonators formed on SiO₂/Al/36°Y-X LiTaO₃ substrate with various kinds of SiO₂ relative thickness were examined experimentally and theoretically. A zero TCF at fr was obtained for h/λ≅0.31, while that at fa was obtained for h/λ≅0.36 from experiments. Moreover, the experimental propagation losses revealed also different characteristics between fr and fa with regard to h/λ. These results can not be obtained by the conventional simulation procedures assuming the uniform SiO₂ film and uniform Al film on LiTaO₃ substrate. We not only applied the coupled finite-element and analytical-solution method to SiO₂/Al/36°Y-X LiTaO₃ substrate but also assumed same periodic unevenness for the surface of SiO₂ as that determined from the Al electrodes. Very good agreements between experimental and the theoretical results were achieved.