The experimental SAW propagation characteristics of sputtered zirconium titanate on lithium niobate

The SAW propagation properties of sputtered zirconium titanate on lithium niobate have been characterized experimentally. Three thicknesses of amorphous ZrTiO₄ (105, 220 and 420 nm) were magnetron sputtered from a composite target onto Y-cut Z-propagating LiNbO₃. The films were analyzed by RBS to determine density values and element concentrations. The SAW propagation properties were carried out over a frequency range from 34 MHz to above 1.0 GHz with pairs of 100 nm aluminum-film interdigital-transducer electrodes. The SAW velocity dispersion characteristic was unique to each film and did not fit a consistent pattern as a function of film-thickness to acoustic-wavelength ratio. Elastic constants were estimated for each of the three films from the SAW velocity dispersion characteristics. The SAW propagation loss in dB/cm increased as the frequency squared. The loss also increased with increasing film thickness. The application of ZrTiO₄ amorphous films to increase the SAW coupling factor was also investigated