Stability of a RF sputtered ZnO solidly mounted resonator sensor in varying temperature and conductivity environments

It has been demonstrated that thickness shear mode acoustic wave devices have been extremely useful for liquid phase sensing applications, especially as biosensors. The quartz crystal microbalance is likely the strongest demonstration of this application to date. Recently, we reported a ZnO-based TSM device that is easily fabricated and operates at significantly higher frequencies than the QCM. To further validate the usefulness of the ZnO resonator as a strong candidate for biosensor applications, we report the stability of the device over varying temperature and sample conductivity. A modest thermal coefficient of resonant frequency is reported at ~25 ppm/degC. Further, it is demonstrated that the resonator exhibits reasonable stability over a range of sample conductivities (0.0 to 0.9 % wt/vol NaCl in DI H₂O).