Highly piezoelectric BaTiO nanorod bundle arrays using epitaxially grown TiO nanomaterials.

Low-dimensional piezoelectric nanostructures such as nanoparticles, nanotubes, nanowires, nanoribbons and nanosheets have been developed for potential applications as energy harvesters, tunable sensors, functional transducers and low-power actuators. In this study, lead-free BaTiO nanorod bundle arrays (NBA) with highly piezoelectric properties were successfully synthesized on fluorine-doped tin oxide (FTO) substrate via a two-step process consisting of TiO epitaxial growth and BaTiO conversion. Through the TiO epitaxial growth on FTO substrate, (001) oriented TiO nanostructures formed vertically-aligned NBA with a bundle diameter of 80 nm and an aspect ratio of six. In particular, chemical etching of the TiO NBA was conducted to enlarge the surface area for effective Ba ion diffusion during the perovskite conversion process from TiO to BaTiO. The final structure of perovskite BaTiO NBA was found to exhibit a feasible piezoelectric response of 3.56 nm with a clear phase change of 180° from the single BaTiO bundle, by point piezoelectric forced microscopy (PFM) analysis. Consequently, highly piezoelectric NBA could be a promising nanostructure for various nanoscale electronic devices.