Piezoelectric PZT thin-film transformers with a ring-dot structure

In this study, we present the design, the modeling, the fabrication, and the characterization of ring-dot type piezoelectric thin-film transformers (PTFTs). The structure of the PTFTs was a simple circular plate of Pb(Zr,Ti)O3 (PZT) thin film on a Si layer with ring-dot top electrodes and it was suspended by four pantograph-shaped bridges. We estimated the performance of the PTFTs by finite-element method simulations. In accordance with the FEM simulation model, PZT thin films were deposited on silicon-on-insulator substrates and microfabricated into PTFTs with ring-dot structures. From the produced devices, an admittance circle measurement was carried out, enabling us to predict performance. The actual output characteristics of the PTFTs were clearly observed at a resonance frequency (f r) of 4.57 MHz. At this point, a voltage gain of 0.22 and a power density of 704 W cm-3 were measured, under a load resistance (R L) of 22 Ω.