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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.