This study examined the effects of the O2 flow rate and the substrate temperature on the structural, electrical, and optical characteristics of the IZO thin films intended for use as anode materials in OLEDs (organic light emitting diodes). These IZO thin films were deposited by RF magnetron sputtering at room temperature and 300 oC at various O2 flow rates. To examine the effects of O2, the O2 flow rate in the argon mixing gas was changed from 0.1 sccm to 0.5 sccm. IZO thin films deposited at room temperature showed an amorphous structure, whereas IZO thin films deposited at 300 oC showed a crystalline structure with an (222) preferential orientation regardless of the O2 flow rate. The electrical resistivity of the IZO thin films increased with increasing O2 flow rate under Ar + O2. The change in the electrical resistivity with increasing O2 flow rate was interpreted mainly in terms of the charge carrier concentration rather than the charge carrier mobility. The electrical resistivity of the amorphous-IZO films deposited at R.T. was lower than that of the crystalline-IZO thin films deposited at 300 oC. All the films showed an average transmittance of more than 83% in the visible range. The optical band gap of the IZO films increased with decreasing O2 flow rate. The current density and luminance of the OLED devices with IZO thin films deposited at room temperature in 0.1 sccm O2 ambient gas were the highest among the films examined. These properties were attributed to the improved optical band gap, which plays a major role in the OLED device performance.

Keywords: IZO thin film, RF magnetron sputtering, Flow rate of oxygen gases, Substrate temperature, Optical band gap, OLED device.