Nanocrystalline diamond/AlN structures for high efficient SAW nano-resonators

Over the last decades, surface acoustic wave (SAW) devices have been involved in a variety of applications including communication systems, physical and chemical sensors and lab on chip. However, increasing demand in high volume communication systems and ultrasensitive sensors has called for advanced SAW devices that can operate at higher frequencies (GHz) while maintaining low insertion levels. Owing to its properties such as very high acoustic velocity, nanocrystalline diamond (NCD) has been utilized for the realization of a high frequency SAW nano-resonators. In this work, we report on the development, fabrication and testing of SAW devices based on aluminum nitride (AlN) and NCD architecture. The NCD films were deposited using microwave plasma enhanced chemical vapour deposition (MWPECVD). The NCD synthesis process details are presented and discussed. An optimized electron beam lithography (EBL) process was used for the realization of high frequency fine resolution SAW nano-resonators on AlN/NCD bi-layer. The fabricated device exhibited a resonance frequency of 11.3 GHz yielding an acoustic velocity of 9040 m/s.