4E-3 Very High Surface Acoustic Wave Velocity on the Layered Structure Formed of Aluminium Nitride on Nanocrystalline Diamond on Silicon

In this work nanocrystalline diamond (NCD) was investigated as high velocity and low propagation loss substrate for SAW devices. The considered layered structure is AIN/NCD/Silicon. First the 16 mum of (110)-oriented NCD films were grown on <100>-oriented silicon substrates of approximately 2.5 cm2 in size. Smooth piezoelectric AIN films with columnar structure and (002) orientation were then deposited on the NCD surface. The AIN film thickness was fixed to 1 mum and the spatial periodicity of IDT to 20 mum. The operating frequency of the realized device was measured at 645 MHz. This shows that surface acoustic waves being propagated at the velocity of 13 km/s were generated in this structure. The obtained velocity value is a quite higher than the value obtained by calculation when elastic constants of polycrystalline are used.