Defect Tuning and Nanoscale Electromechanical Characterisation of ZnO Nanowires

Abstract:
ZnO nanowires (NWs), as one-dimensional piezoelectric semiconductors with high elastic limits and huge surface-to-volume ratios, allow for robust coupling of electrical and mechanical fields such as mechanical energy harvesters. ZnO NWs were grown via hydrothermal chemical bath deposition on texturized seed layers deposited by spin coating, and their morphological and structural characteristics were studied using scanning electron microscopy and X-ray diffraction. Post-growth treatments, such as vacuum annealing, oxygen annealing and oxygen plasma, were used to tune defect chemistry and improve electromechanical performance. Photoluminescence and X-ray photoelectron spectroscopy were employed to study defects, while correlated AFM techniques such as Piezoresponse Force Microscopy (PFM), Kelvin Probe Force Microscopy (KPFM), and Scanning Microwave Impedance Microscopy (SMIM) were used to investigate nanoscale electrical, mechanical, and piezoelectric behaviour. ZnO NWs were also integrated onto different test structures to retrieve complementary information through their mechanical, electrical, or electromechanical characterization by sophisticated instruments such as Synchrotron.