Fabrication of PZT MEMS energy harvester based on silicon and stainless-steel substrates utilizing an aerosol deposition method

In this paper, a series of the processes for fabricating lead-zirconate-titanate (PZT) micro-electro-mechanical-systems (MEMS) energy harvester based on silicon and stainless-steel substrates is presented. The aerosol deposition method was used to fabricate the high-quality PZT layers on substrates for the PZT MEMS energy harvesters in this study. A special lift-off process for patterning very thick PZT film (5–10 µm) for high-aspect ratio structures with almost vertical sidewalls at room temperature is presented and adopted here to fabricate the MEMS energy harvesters. To achieve excellent ferroelectric properties of the PZT layer, an annealing process was applied. These two devices were both fabricated by using standard MEMS processes with a chip area of 3000 × 1500 µm2. Our experimental results show that the device based on silicon substrate had a maximum output power of 21 µW with 2.2 Vrms output voltage excited at 215 Hz under a 1.5 g vibrating source. The device based on stainless-steel substrate had a maximum output power of 34 µW with 1.8 Vrms output voltage at a vibration frequency of 202 Hz at 1.5 g acceleration. The areal power densities were 4.7 and 7.6 µW mm−2 for the devices based on silicon substrate and the device based on stainless-steel substrate, respectively. The power output, effective volume power density, area power density, normalized power density and the lifetime under high acceleration excitations of the two devices on different substrates are discussed and also compared with the previous published devices. The results shows that the device fabricated on stainless steel has higher power output, area power density and also more reliable to sustain for much longer time under high acceleration excitations.