Xin Wan

Ph.D. thesis

Thesis title:

Tailored piezoelectric thin films for energy harvester

[thesis in pdf format]




Prof. dr. ing. A.J.H.M. Rijnders

Date defense:



Piezoelectric materials are excellent materials to transfer mechanical energy into electrical energy, which can be stored and used to power other devices. PiezoMEMS is a good way to combine silicon wafer processing and piezoelectric thin film technology and lead to a variety of miniaturized and premium devices. To understand the material performance in piezoMEMS devices, the knowledge of a couple of characteristic properties, such as the electro-mechanical properties, the dielectric constant and the piezoelectric coefficients, become much more crucial. In this thesis, energy harvesters are made, based on epitaxial PZT thin films with enhanced material properties.

These vibration energy-harvesting devices consists of a bulk mass attached to a cantilever. Before fabricate the device, the material properties are tailored to reach the optimal electrical output. In particular, epitaxial PZT thin films with different compositions and different dopants are studied and a variety of dielectric and piezoelectric properties are discussed. In the end, the epitaxial vibration-harvesting devices are fabricated, which are able to generate energy at microWatt scale with low vibration state. Furthermore, after power normalization, a comparison is made between different vibration harvester.

It is concluded that the epitaxial PZT thin film harvester devices outperform the textured PZT and AlN thin film harvesters.