Optical and structural study of Ga and In co-doped ZnO films

Abstract

Doping with different metals leads to effective modification of structural, morphological, optical, electrical and chemical properties of ZnO films. Ga and In co-doped ZnO thin films have been succesfully obtained by the sol-gel method, using spin coating. FTIR detailed studies of undoped ZnO, In or Ga doped and In-Ga- ZnO films reveal that Ga and In co-doping affects the shapes and the intensity of the absorption bands. No clear traces of Ga–O and In–O bonds are detected. XRD analysis shows that In and Ga co-doped ZnO films posses lower crystalization compared to ZnO and ZnO:Ga. Respectively, the crystallite sizes of co-doped systems are significantly smaller compared to ZnO crystallites and closed to that of ZnO:Ga 3 films. The lattice parameters, texture coefficients are determined from XRD data. Optical characterization shows that the In and Ga co-doped ZnO films are found to be less transparent compared to sol-gel derived ZnO and ZnO:Ga films. The optical band gaps of co-doped films are estimated as a function of the annealing temperatures, ranging from 3.41 up to 3.28eV. It has been observed that the optical band gap values of In-Ga-Zn-O films are strongly dependent on the indium doping concentration.