Effects of substrate temperature on the growth orientation and optical properties of ZnO:Fe films synthesized via magnetron sputtering

Fe-doped ZnO (ZnO:Fe) thin films were successfully prepared by radio frequency magnetron sputtering under different substrate temperatures. The properties of ZnO:Fe films were systematically studied via X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), ultraviolet visible spectrophotometer and fluorescence spectrophotometer with the emphasis on orientation, element composition, surface morphology and optical properties. The results indicated that the properties ZnO:Fe films were significantly affected by substrate temperature. XRD demonstrated that highly c-axis preferential orientation of ZnO:Fe film with wurtzite phase was fabricated exceed 300 °C. The optical absorption properties and the shift of the optical band gaps were also investigated. The analysis reveals that the increasing of the band gaps was caused due to the improvement of the quality of film and the decreasing of the band gaps was likely due to the raising the concentration of carriers caused by increasing substrate temperature. Urbach energy decreased with increasing the substrate temperature from RT to 150 °C while increased from 150 °C to 450 °C. The photoluminescence measurements of ZnO:Fe films at room temperature revealed a violet, a blue and a green emission and the origin of these emissions was discussed in detail.