Deposition of piezoelectric AlN thin film on diamond substrate for SHF SAW devices

The preparation of piezoelectric AIN thin films of high quality onto diamond substrates using DC-TFTS method and its application to SHF SAW devices are discussed. FWHM (=3.4deg) of the rocking curve of XRD suggested that the c-axes of AIN films may well align perpendicular to the film surface. Transversal filters based on Sezawa wave were fabricated to verify whether the prepared AIN/diamond structure can be applied to low loss SAW devices in an SHF range. The propagation loss was experimentally estimated to be 0.08 dB/lambda at the centre frequency of 6.12 GHz. Further reduction in the propagation loss was attempted by using small-grain-diamond substrates.