Comparative study of structural, optical and electrical properties variation of pure, (Ag, Mg) doped and co-doped ZnO nanostructured thin films

Abstract

Abstract Nanostructured thin films are one of the most valuable types of industrial semiconductors for a variety of optoelectronics and optical device applications, having recently been used as a transparent conductive oxide in solar cells. In this work, nanostructured thin films of pure ZnO, Ag doped ZnO, Mg doped ZnO and Ag–Mg co-doped ZnO were successfully synthesized on silicon and glass substrates, using rapid thermal evaporation. The impact of the doping elements on the surface morphology, structural, electrical, and optical properties of the deposited films were investigated. It was found that all films have polycrystalline hexagonal wurtzite structure using X-ray diffraction. Images obtained by scanning electron microscopy (SEM) revealed compact and smooth surfaces, with uniform coverage of all substrate regions. SEM images confirm the nanostructured nature of the surfaces with particle size varying as a function of doping. Raman spectroscopy showed A1(LO), E2(high) and LVM modes for all samples. The developed films’ optical transmission ranged from 74 % to 87 %, with an optical bandgap ranging from 3.09 for Mg:ZnO films to 3.8 eV for Ag:ZnO samples. Depending on the doping nature modification, these alterations were associated to structural and morphological changes in the films. All films were electrically conductive, while Ag:ZnO films exhibited the lowest resistivity value reaching 0.56 Ω cm.