Title : Influence of annealing temperature on the structure and dielectric characterization of Indium-doped Tin Oxide (ITO) thin films on a boro-float substrate prepared by radio frequency sputtering
The effect of annealing temperature (Ta= 200, 250, and 300 °C) on the structural properties, ac conductivity, and complex dielectric constants ( , ) of ITO thin films (~90 nm thick)/0.5 mm boro-float substrates (BFS) synthesized by RF sputtering is investigated. The XRD examination demonstrated that indium was successfully substation with tin atoms for forming ITO films and that the crystallite for the cubic phase, as well as particle sizes, are impacted by Ta. The real part of was significantly dropped for all films from 2.7–5.1×104 to 5.3-19 range as frequency (f) increased to 0.25 Hz, while it was constant for further increases in f. The of the as-prepared ITO/BFS has increased as Ta increases to 250 °C, then decrease at Ta=300 °C. A similar finding was detected for the loss factor with no relaxation peaks. The Q-factor has increased for all ITO/BFS as f increases to 100 Hz and then reduced with increasing f up to 20 MHz, while gradually increasing with Ta. The frequency exponent is more than 0.5 for the ITO/BFS, indicating their electronic conduction nature. The density of localized states and hopping frequency of the ITO/BFS were increased by annealing at 200 °C meanwhile decreased for Ta = 300 °C. The binding energy is decreased from 0.647 eV for the as-prepared ITO/BFS to 0.518 eV by annealing at 200 °C, meanwhile increasing to 0.74 and 0.863 eV for Ta equals 250, and 300 °C, respectively. The Cole-Cole plots show a single semi-circular arc for all films, and their corresponding equivalent circuit was analyzed. For example, the equivalent bulk series resistance gradually decreased by annealing to 300 °C, whereas the equivalent capacitance decreased. The resistance of grains and grain boundaries of the as-prepared ITO/BFS film is gradually decreased by increasing Ta to 250 °C, while it is increased at 300 °C. These outcomes recommended the ITO/BFS for high-frequency devices, integrated circuits, and supercapacitors.