Microstructure and piezoelectric properties of AlN thin films grown on stainless steel for the application of vibration energy harvesting

By analysing the energy flow in a piezoelectric generator, it was revealed that the mechanical factor, electromechanical coupling coefficient and dielectric loss of the generator have significant influence on its energy conversion efficiency. Based on this analysis, aluminium nitrate (AlN) thin films deposited on stainless steel (SUS) were selected to substitute lead titanate zirconate thin films deposited on single-crystal Si for fabricating miniature devices. These thin films were prepared with an electron cyclotron resonance sputtering system. The influences of the surface modification (polishing or coating a Pt/Ti thin layer) of SUS substrates on c-axis orientation, piezoelectric coefficient and effective coupling coefficient of AlN thin films were investigated.