Superior control for physical properties of sputter deposited ITO thin-films proper for some transparent solar applications

Abstract

Superior control of sputtering deposition of ITO thin-films to enhance the physical properties of the ITO thin-films has been investigated. The effect of different sputter deposition conditions and the thermal post-annealing on the physical properties of the transparent-conductive indium tin oxide (ITO) thin-films deposited on a glass substrate have been studied. The power varied from 20 to 210 W with argon (Ar) gas flowing at a rate from 20 to 80 sccm. Thermal post-annealing of deposited thin-films at 200–450 °C in vacuum and air has been carried out as well. The physical properties were monitored using XRD, STM, four-point probe electrometer, and UV–Vis spectrometer. The change of the Ar flow rates influences the deposited films surface roughness, electrical sheet resistance (Rs), average optical transmittance (Tavg) with no apparent change in the morphology fractal dimension. At the Ar flow rate of 30 sccm and the critical power of 120 W, the deposited thin-films transform from amorphous to semi-crystalline structure mostly up 170 W. Optimal thin-films with fairly the highest Tavg at 97.7% and good Rs with 158.3 Ω/sq could be obtained under a residual Ar gas flow rate of 50 sccm and at 20 W. The critical post-annealing temperature at 350 ℃ (air) and 450 °C (vacuum) could initiate the semi-crystalline structure of the previously amorphous deposited thin-films. For the first time, ITO thin-films with Tavg and Tmax up to 97.7% and 99.9% respectively have been achieved. Besides, the Rs value is controlled from 6 to 3981 Ω/sq with excellent average transparency. These prove viable candidates in transparent solar applications.