Crystallographic investigation of aluminium nitride thin films on stainless steel foil for highly efficient piezoelectric vibration energy harvesters

This study reports piezoelectric properties and crystallographic microstructures of aluminium nitride (AlN, wurtzite structure) thin films on 50 μm thick stainless steel foil. The transverse piezoelectric coefficient d_31f and e_31f of 10 pm thick AlN films were estimated as -1.42 ± 0.08 μm/V and -0.48 ± 0.03 C/m² from a tip displacement of the piezoelectric cantilevers. Dielectric constant s₃₃ was measured as 10.5 ± 1.0. An electron beam diffraction pattern by a high-resolution transmission electron microscope and x-ray diffraction pattern showed that abundance ratio of the orientation such as <101>, <102> and <103> of AlN crystal on stainless steel foils increased with increasing thickness.