Synergistic effect of indium and gallium co-doping on the properties of RF sputtered ZnO thin films

ZnO thin films were synthesized using RF magnetron sputtering, with simultaneous incorporation of Indium (In) and Gallium (Ga). The structural, optical, chemical composition and surface morphology of the pure and co-doped (IGZO) thin films were characterized by X-Ray diffraction (XRD), UV-visible spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), and Raman spectroscopy. XRD revealed that these films were oriented along c-axis with hexagonal wurtzite structure. The (002) diffraction peak in the co-doped sample was observed at 33.76° with a slight shift towards lower 2θ values as compared to pure ZnO. The surface morphology of the two thin films was observed to differ. For pure ZnO films, round grains were observed and for IGZO thin films round as well as rod type grains were observed. All thin films synthesized show excellent optical properties with more than 90% transmission in the visible region and band gap of the films is observed to decrease with co-doping. The co doping of In and Ga is therefore expected to provide a broad range optical and physical properties of ZnO thin films for a variety of optoelectronic applications.