Elaboration and characterization of pure ZnO, Ag:ZnO and Ag-Fe:ZnO thin films: Effect of Ag and Ag-Fe doping on ZnO physical properties

Abstract

Pure ZnO, Ag doped ZnO and Ag-Fe co-doped ZnOwere preparedusing thermal evaporation.  XRD analysis confirms that all layers present a hexagonal wurtzite structure; however, there is a small shift in the peaks position due to thedistortion of the film’s lattice. Scanning Electron Microscopy (SEM) analysis reveals the morphological variation of the film’s surfaces due to the doping. Pure ZnO and Ag:ZnO films have a nanostructured surface, however, Ag-Fe:ZnO films showed a smooth surface without any nanoparticles. Raman analysis showed the presence of A1(LO), E2(high) andlocal vibrational modes (LVMs) for all layers. Ultraviolet–visible spectroscopy (UV-VIS) analysis shows that the films have a good transparency and the bandgapdecreases with ZnO doping from 3.80 eVto 3.78 eV and 3.70 eV,for pure ZnO, Ag:ZnO and Ag-Fe:ZnO films, respectively. The electrical properties confirm the semiconductor nature of ZnO films with a resistivity around 1.4 Ω.cm, and with Ag and Ag-Fe doping, the films behave like conductors with 1.4´10-4Ω.cm and 1.4´10-3Ω.cm, respectively. These results make the Ag:ZnO and Ag-Fe ZnO thin films good materials for photovoltaic application.