Piezoelectric ZnO nanorod carpet as a NEMS vibrational energy harvester

A nanoelectromechanical vibrational energy harvester is reported based on a ZnO nanorod array coupled to a microelectromechanical mass-spring system. A carpet of vertically aligned crystalline zinc oxide nanorods grown using a low temperature process was characterized to determine their piezoelectric response to mechanical excitation. An atomic force microscope was operated in the force spectroscopy mode to probe ZnO nanorods applying a force in the mu N range. In contrast to previously published reports using lateral tip motion (C-AFM), the motion of the AFM tip in our experiment was perpendicular to the plane of the nanorods, which closely mimics the operation of the bulk-micromachined NEMS energy harvester. Voltage pulses with amplitudes ranging from hundreds of mu V to few mV were observed. The novelty of this work lies in the integration of the ZnO NEMS and Si-MEMS structures, the use of nanoimprint lithography to achieve periodic, vertical placement of the ZnO nanorods, and the demonstration of piezoelectric voltage generation through low-temperature processed ZnO nanorod carpet. (C) 2014 Elsevier Ltd. All rights reserved.