Impedance Analysis of the Morphology Dependence of the Dielectric Properties of Four Different ZnO Nanomaterials

ZnO nanostructures are an important semiconductor for third-generation photovoltaic (PV) cells as well as other electronic devices. In this study, we report results from impedance spectroscopy measurements on four ZnO morphologies - in order of increasing spherical symmetry and decreasing surface roughness: nanoribbons (NRIs, ~10µm), nanorods (NROs, ~7µm), nanoshuttles (NSs, ~1µm), and nanoparticles (NPs, ~20nm) - to determine the relationship between morphology and dielectric response. The nanostructures are prepared by chemical bath deposition. NRIs, NROs, and NSs are prepared and measured on FTO glass slides, which makes the data from the study ideal for PV applications. Scanning Electron Microscopy and Tunneling Electron Microscopy were used to measure the dimensions of these four morphologies. Impedance spectra in the 100Hz-5.1MHz frequency range suggest that decreasing complexities of surface structures and increasing spherical symmetry leads to an increased dielectric constant of ZnO nanostructures at low frequencies. This increased dielectric constant is also clearly manifested in the phase spectra of each morphology from 100Hz-10kHz.