Sammendrag
Piezoelectric thin film ultrasonic transducers were realised and tested for short range distance measurements. Displacements in air and water as a function of frequency were modelled by Comsol Multiphysics finite element modelling (FEM) and transducer configurations with a two electrode layout were manufactured to enable larger displacements than with the conventional design. The transducer was fabricated on a silicon wafer by chemical solution deposition (CSD) with total PZT (Pb(Zr0.53Ti0.47)O3) thickness of 2 µm. Subsequently, a cavity underneath the PZT was wet etched creating a bending membrane with a total thickness of ∼13 µm. The displacements of the transducers as a function of frequency were modelled and measured by fiber-optic laser vibrometer. The effective piezoelectric d33 coefficient of 300 nm/V and 144 nm/V in air and 48 nm/V and 18 nm/V in water was obtained for 260 × 260 µm2 and 390 × 390 µm2 membranes, respectively. The accuracy of the modelled resonance frequencies both in air and water was relatively good, of ∼4-13% and ∼5-20%, respectively.