Schottky barrier tuning in semiconducting ZnO and BaTiO3 hybrid heterostructures shows dielectric and electrical anisotropy

Abstract

Polygonal nanosize BaTiO₃ and modified BaTiO₃ with carbon are prepared using a modified hydrothermal process and utilized as solutes to set up bimodal hollow zinc oxide (ZnO) heterostructures. Powder X-ray diffraction and Raman spectroscopy confirmed the formation of tetragonal and pseudo-cubic structures for BaTiO₃ and modified BaTiO₃, respectively. Pure ZnO and ZnO heterostructures were well characterized with the aid of various sophisticated techniques. The results suggested the formation of stable heterostructures with structural inhomogeneity and a considerable shift in the band gap compared to that of pure ZnO. The dielectric study of the developed ZnO heterostructures was carried out over a wide range of frequencies (10⁰ to 10⁶ Hz) and temperatures (−100 to 60 °C) and showed a significant improvement in dielectric properties. The frequency dependent maxima in the imaginary part of electric modulus of the ZnO heterostructures followed the Arrhenius law and the activation energy of the heterostructures were found to be ∼0.16 eV. Furthermore, the localized electrical properties of the ZnO heterostructures were investigated using conductive atomic force microscopy (C-AFM) by recording current maps while simultaneously acquiring topographic images. The deliberate analysis of local current–voltage (I–V) characteristics of ZnO heterostructures by C-AFM exposed the formation of Schottky diodes with divergence in the barrier heights between the metal and semiconductor interface.