| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 92 === Diamond has the highest acoustic propagation property, making it an ideal substrate for surface acoustic wave (SAW) device when coupled with piezoelectric materials. In the work, SAW devices based on ZnO/NCD/silicon layered structure are successfully performed. The device response is analyzed with frequency and time domain methods. The resonant frequencies of the devices agree with the results of numerical simulation for sound propagation in layered media. We conclude that NCD is a highly attractive substrate material for SAW devices, possessing the high sound velocity of diamond but requiring less manufacture processing.
Furthermore, LiNbO3 singe crystal is well-known for its superior electromechanical coupling coefficient (K2) among a wide variety of piezoelectric materials, which promise significant improvement in SAW device performance. However, the studies with regard to the integration of NCD and LiNbO3 substrate have been scarcely reported. In this study, smooth NCD films have successfully been synthesized on LiNbO3 substrates. To avoid the mismatch of thermal expansion, a thin silicon layer of amorphous and poly silicon were deposited on the LiNbO3 substrate serving as a good adhesion layer at the NCD/LiNbO3 interface. It is found that the initial NCD nucleation density and the quality of the NCD films are substantially enhanced by applying a negative bias during NCD film deposition. We believe that the novel NCD/LiNbO3 architecture exhibits significant high K2 properties will be superior to traditional silicon base diamond SAW devices.
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