| 摘要 |
PURPOSE: To provide a large electromechanical coupling coefficient by forming a specified piezoelectric thin film on a piezoelectric substrate composed of a specified LiNbO3 single crystal. CONSTITUTION: This device is provided with the piezoelectric substrate 17 composed of a Y-cut Z-direction propagation LiNbO3 single crystal, at least one interdigital transducer formed on the positive Y-surface of the piezoelectric substrate 17 and a positive surface piezoelectric thin film 8 formed on the positive Y-surface of the piezoelectric substrate 17 and composed of one kind among ZnO, Ta2 O5 and CdS. Then, in the case of forming the piezoelectric thin film 18 of a positive surface or a negative surface on the positive Y-surface or negative Y-surface of the piezoelectric substrate 17 composed of the Y-cut Z-direction propagation LiNbO3 single crystal, the electromechanical coupling coefficient is effectively improved. Preferably, when the film thickness of the piezoelectric thin film 18 is defined as H and the wavelength of surface waves to be propagated is defined asλ, H/1 is within the range of 0.08-0.3. Thus, efficiency is effectively improved in the case of performing utilization in elastic convolver and sufficient resonance characteristics and filter characteristics are obtained in the other surface wave device as well.
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