Syntheses, structural evolution, electrical and optoelectronic characterization of ZnO/CuO composite films doped with transition metal Mn2+ ions

Abstract

This study was done aiming to evaluate the influence of manganese (Mn) as a transition metal on the morphological, structural, optical, electrical, and optoelectronic characteristics of nanostructured ZnO/CuO films. Different Mn concentrations (1 and 2 M%) were used to analyze these properties. In the present research, we have described the synthesis of nanocomposite pristine ZnO/CuO and Mn-doped ZnO/CuO (Mn: ZnO/CuO) oxide films by using simple successive ionic layer adsorption and reaction (SILAR) procedure. Scanning electron microscopy (SEM) and atomic force microscope (AFM) pictures reveal that the surface structure of ZnO/CuO nanocomposites was effectively altered by Mn2+ ion substitution. Energy-dispersive X-ray analysis (EDX) confirms the presence of Zn, Cu, O, and Mn elements in the synthesized nanofilms. The film thickness had decreased from 1.65 to 1.23 μm as a function of increasing Mn2+ concentration. The X-ray diffraction (XRD) pattern revealed that the synthesized ZnO/CuO nanocomposite was polycrystalline and the crystallite size decreases from 40.16 to 34.14 nm with increasing Mn2+ ion concentrations. The optical bandgap energy was found using Tauc's graph and it varied from 2.37 to 2.56 eV. A maximum average transmittance (30%) was obtained for 2 M% Mn2+ concentration. Electrical measurement of the ZnO/CuO composite films shows sheet resistance (Rs) change between 1.01 and 0.41 (x108Ω/sq.) depending on temperature from 300 K to 400 K. The biggest figure of merit observed in this work was 4.69 × 10−8 Ω−1. The results have shown that Mn-doping has an important effect on the physical attributes of SILAR-deposited ZnO/CuO films.