Influence of Thermal Treatment and Fe Doping on ZnO Films by Ultrasonic Spray Pyrolysis

Zinc Oxide and Fe-doped ZnO films (1, 2, 3, %) were deposited onto glass substrates by ultrasonic spray pyrolysis. Then, the films were thermally treated at 500°C for 2 hours. Findings revealed that both Fe doping and thermal treatment changed film properties. Films presented hexagonal wurtzite structures without any secondary phases for all films. The preferential orientation (002) changed to dominant growth directions (100) and (002) according to the doping concentration and thermal treatment. The grain size of the ZnO nanogranules decreased after Fe doping and also thermal treatment. The optical transparency was found maximum of 77 % in the visible region. 3 % Fe doping and thermal treatment caused the reduction in the optical band gap values to 3.18 eV. Fourier transform infrared spectroscopy analysis presented the Z-O stretching, C-H vibration, and O-H stretching bonds. Shifting in the peak position indicated the Fe+2 ion substitution. Photoluminescence analyses revealed the reduced emission intensity with the effect of thermal treatment. Photocatalytic performance tests showed improved degradation efficiency after the films were thermally treated. Especially among Fe-doped films, thermally treated 1 % Fe-doped ZnO film showed a significant increment after as-deposited ones. Consequently, it has been uncovered that thermal treatment and Fe doping significantly influence the investigated film properties.