Piezoelectric Thin Films of ZnO-Nanorods/Nanowalls Grown by Chemical Bath Deposition

This study presents a comparison of the piezoelectric properties of nanostructured thin films made of arrays of vertically oriented ZnO-nanorods (ZnO-NRs) over ITO-glass substrate and of ZnO-nanowalls (ZnO-NWs) over aluminium substrate. Both nanostructures were synthesized on a large area through chemical bath deposition. The morphological, structural, and chemical characteristics of the produced nanostructures were investigated in order to assess the crystal quality and purity. To this purpose, we used different techniques, such as field-emission scanning electron microscopy, atomic force microscopy, energy dispersive x-ray analysis, powder x-ray diffraction, x-ray photoelectron spectroscopy, and photoluminescence spectroscopy. Moreover, the piezoelectric response of the nanostructured films was assessed through piezoresponse force microscopy. This technique was employed to obtain a quantitative evaluation of the piezoelectric coefficient (d
₃₃
) of the film. We obtained d
₃₃
values as high as (7.01 ± 0.33) pm/V for ZnO-NRs and (2.63 ± 0.49) pm/V for ZnO-NWs films.