Temperature effect on the characteristics of surface acoustic wave on SiO/sub 2/ thin films

The surface acoustic wave (SAW) propagation characteristics of a layered structure consisting of a SiO/sub 2/ thin film on z-cut LiNbO/sub 3/ substrate in company with temperature dependence of frequency of this structure has been studied experimentally. The temperature coefficient of frequency (TCF) of SAW devices was obtained by a network analyzer. A SAW device on the lithium niobate (LiNbO/sub 3/) exhibits a large negative TCF. It revealed that the SiO/sub 2/ thin film was introduced as compensation layer for improving the temperature stability. The TCF of the SiO/sub 2//LiNbO/sub 3/ based structure was significantly decreased due to the SiO/sub 2/ thin film deposition. The TCF of SAW on the SiO/sub 2//LiNbO/sub 3/ device was measured to be about -51 ppm//spl deg/C at h//spl lambda/=0.12, where h was the thickness of SiO/sub 2/ film and /spl lambda/ was the wavelength of SAW. It indicated that the SiO/sub 2/ thin film deposited on LiNbO/sub 3/ substrate could improve the temperature stability, as compared with the TCF of SAW on bare LiNbO/sub 3/. Furthermore, the phase velocity (V/sub p/) of SAW on SiO/sub 2//LiNbO/sub 3/ substrate was not altered by the increase of SiO/sub 2/ thickness (h//spl lambda/).