Synthesis and characterization of Fe-doped ZnO thin films deposited by chemical spray pyrolysis

In the present study, iron doped zinc oxide (ZnO:Fe) thin films were prepared by using a simple chemical spray pyrolysis technique by varying the doping concentration in the range, 0–6 at.% at a constant substrate temperature of 400 °C.The effect of Fe-doping concentration on the physical behavior of ZnO thin films were analyzed and discussed. The X-ray diffraction (XRD) patterns exhibited hexagonal wurtzite crystal structure without any secondary phases for all the films irrespective of the doping concentration. However, the preferential orientation changed from (002) to (101) plane with increase of Fe-doping. The Raman spectroscopy studies showed the peaks at 338 cm-1, 438 cm-1 and 574 cm-1 which are the characteristic vibrational modes of ZnO. The scanning electron microscopic (SEM) images showed irregular shaped grains grown over the substrate surface. The X-ray photoelectron spectroscopy (XPS) studies confirmed the presence of Fe in +3 state in ZnO layers. The Fourier transform infrared (FTIR) spectroscopy data revealed the presence of iron in the doped ZnO films by showing the modes related to iron in addition to ZnO. The optical properties revealed that the films with lower Fe-doping concentration (≤ 2 at.%) showed high transmittance and wide band gap than the pure and highly Fe-doped ZnO films. The evaluated band gap showed a red shift upon doping with the energy band gap decreased from 3.24 eV to 3.01 eV for the investigated doping concentration range. The photoluminescence spectra also showed similar optical behavior with quenching of PL signal intensity of the films. Moreover, all the Fe-doped ZnO films showed ferromagnetic behavior at room temperature