Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8130531 | Ultrasonics | 2015 | 5 Pages |
Abstract
Thin film acoustic resonators operating in the shear mode are being increasingly used for in-liquid sensing applications. A good design of such sensors requires accurate knowledge of the acoustic properties of the materials composing the whole device, which specifically includes their shear velocities. Here we present a method to assess the shear acoustic velocity of high and low acoustic impedance films commonly used in AlN-based solidly mounted resonators (SMRs), using test devices specifically designed to induce a half-wavelength resonance in the layer under study. Provided that the thickness and mass densities of all the layers are known, fitting the electrical response by Mason's model over a wide frequency range gives accurate values of both longitudinal and shear mode velocities. The assessment of porous and dense SiO2, Mo, W and Ta2O5 sputtered films yields shear velocities of 3150Â m/s, 3950Â m/s, 3450Â m/s, 3350Â m/s and 2900Â m/s, respectively. In addition, the resonances stimulated in the Ir and Au top electrodes enable deriving their shear modes velocities, with values of 3950Â m/s and 2350Â m/s, respectively.
Keywords
Related Topics
Physical Sciences and Engineering
Physics and Astronomy
Acoustics and Ultrasonics
Authors
M. DeMiguel-Ramos, T. Mirea, J. Olivares, M. Clement, J. Sangrador, E. Iborra,