Magnesium zinc oxide (Mg xZn 1-xO) is a new piezoelectric material formed by alloying ZnO and MgO. In this study, the SAW velocity dispersion and electro-mechanical coupling coefficients (K 2) in the Mg xZn 1-xO (x=0-30%)/SiO 2/Si system are analyzed using the transfer matrix method. Si is chosen as the substrate for potential integration of SAW devices with the main stream integrated circuits technology. The use of different Mg content in Mg xZn 1-xO films leads to change in piezoelectric properties. The SAW characteristics of the system can be further tailored by varying the thickness ratio between the Mg xZn 1-xO and SiO 2 layers. The effect of different Mg xZn 1-xO to SiO 2 thickness ratios on SAW propagation in the multilayer structure is investigated. Four possible multilayer SAW device configurations, including IDT/Mg xZn 1-xO/SiO 2/Si, Mg xZn 1-xO/ IDT/ SiO 2/ Si, IDT/ Mg xZn 1-xO/ metal ground plane/ SiO 2/ Si, and metal ground plane/ Mg xZn 1-xO/ IDT/ SiO 2/ Si, are studied. It is found that at the high frequency range, with each 10% increase of the Mg content in the Mg xZn 1-xO, SAW velocity increases by 5-8%, whereas K 2 decreases by around 30%. With same IDT configuration, V SAW decreases as SiO 2 layer thickens. However, as Mg xZn 1-xO thickness-frequency products hf reach high values, the SAW energy for the base wave mode is trapped in the Mg xZn 1-xO layer and the thickness of SiO 2 no longer affects the SAW propagation. The multilayer configurations also play an important role. It is found that the Mg xZn 1-xO/ IDT/ SiO 2/ Si configuration with Mg xZn 1-xO: SiO 2=2:l yields the highest coupling coefficient (x=0) and the highest SAW velocity (x=0.3). The current study indicates that using Mg xZn 1-xO-based multilayer structures will provide flexibility in SAW device design as well as the ability to tailor SAW properties.
ASJC Scopus subject areas
- Acoustics and Ultrasonics