Effect of thermal annealing on the structural, optical and electrical properties of n-ZnO/p-CuO heterojunctions obtained by pulsed spray pyrolysis

Abstract In this work, the study of the effect of thermal annealing on the phase composition, surface morphology, structural and substructural characteristics, optical, photoelectric and electrical properties of multilayer structures based on n-ZnO/p-CuO heterojunctions obtained by the pulsed spray pyrolysis method is carried out. The study of multilayer structures was performed using x-ray diffraction analysis, scanning electron microscopy, Raman and optical spectroscopies, as well as by the measurements of the low-temperature photoluminescence spectra and the I-V characteristics. These studies allowed us to determine the structural and substructural characteristics, such as lattice parameters (a,c) sizes of coherent scattering regions (L), level of microstrain ( ε ) , optical and crystal quality and band gaps (E g ) of both individual layers and the heterostructures as a whole, as well as the dependence of these properties on the annealing temperature (T a ). Analysis of the absorption spectra of the heterostructures indicates the presence of spectral regions corresponding to the absorption of both zinc oxide layers and copper oxide layers, covering the spectral region from 1.1 eV to 3.6 eV. It was found that the rectification coefficient of the heterostructure is the best at an annealing temperature of 350 °C. Energy band diagrams for an ideal n-ZnO/p-CuO heterojunction are constructed. The obtained results indicate the potential of the n-ZnO/p-CuO heterojunctions deposited by chemical methods for use in sensors, solar energy, and optoelectronics.