Leaky surface acoustic waves in Z-LiNbO3 substrates with epitaxial AIN overlays

The properties of leaky surface acoustic waves (LSAW) in MBE grown AIN layer on Z-cut LiNbO3 structures have been studied by numerical simulation and experimental measurements and compared with those of Rayleigh waves in the same structure. In the range of AIN layer thicknesses studied (0<kh<0.145) the measured velocity of LSAW propagating along the X axis of LiNbO3 substrate was essentially constant at around 4400m∕s. The measured electromechanical coupling coefficients (K2) for the LSAW are roughly 1/4 of the predicted values, which might be due to the strong attenuation of the leaky wave unaccounted for during the parameter extraction. The thin AIN film slightly improved the measured temperature coefficient of frequency for the LSAW over that attained for the Z-cut, X-propagating LiNbO3 substrate alone.