The characteristics of leaky surface acoustic wave of proton-exchanged lithium tantalite

Proton exchange (PE) is an attractive method for the fabrication of optical and acoustic waveguides in lithium tantalite (LiTaO₃) substrate. Octanoic acid was used for the fabrication of PE LiTaO₃ waveguides. After the PE process, the resultant substrate showed a damage-free surface from observations by scanning electron microscopy (SEM). And X-ray diffraction (XRD) was adopted to identify the crystalline structure of LiTaO₃. From the X-ray diffraction (XRD) results, the reflection peak of (306) was shifted after the PE process. The influences of the exchanging time on properties of leaky surface acoustic wave (LSAW) devices were discussed. The single electrode geometry of interdigital transducers (IDT) was adopted to excite and receive the acoustic wave. The wavelength (λ) of the LSAW is 32 μm. The frequency response of the LSAW is measured using an HP 8720ET network analyzer. The velocity of LSAW was decreased as the increase of PE time; nevertheless, the range of variation was quite small. Measurements of the temperature dependence of LSAW velocity were carried in the temperature range from 0°C to 80°C. The temperature coefficient of frequency (TCF) of LSAW devices was significantly increased by the increase of PE time. The PE process changed the characteristics of material and specific property can be obtained.