Effect of iron doping on structural, optical and electrical properties of sprayed In2O3 thin films

Iron doped indium oxide thin films were grown by chemical spray pyrolysis technique at different concentrations y = [Fe2+]/[In3+] (y = 0, 2, 4 and 6 at.%). Structural, morphological, optical and electrical properties were studied by X-ray diffraction, Raman spectroscopy, atomic force microscopy, spectrophotometer, fluorescence spectrometer and Hall Effect. The XRD analyses show that indium oxide crystallizes into cubic structure with (2 2 2) as a preferred orientation. An enhancement of the crystallinity followed by a change in plan orientation from (2 2 2) to (4 0 0) was observed when iron doping concentrations is increasing. The optimum of In2O3 crystal structure is obtained for iron concentration equals to 6 at.%. Transmission and reflection spectra reveal the presence of interference fringes with oscillatory character indicating the good uniformity and optical homogeneity of deposited films. The obtained band gap energy Eg is in the range of [3.29-3.45] eV. The single oscillator energy E0 and dispersion energy Ed were determined by Wemple model using the envelope method applied for all obtained XRD spectra. We found that E0 = 2 × Eg for iron doped films and E0 = 1.5 × Eg for undoped ones. Measured electrical resistivity decreases from ρ = 6502 × 10−4 to 197.9 × 10−4 Ω cm for respectively undoped and In2O3:Fe(6 at.%) thin films. A heat treatment was carried out at different temperatures (200 °C, 300 °C and 400 °C) under nitrogen atmosphere to try to reduce more electrical resistivity. We found that it decreases to about 26.94 × 10−4 Ω cm for 300 °C annealing temperature.