Electrical, optical and material properties of ZnO-doped indium-tin oxide films prepared using radio frequency magnetron cosputtering system at room temperature

The relationship between the electrical, optical and material properties of transparent and conductive oxide films prepared by rf cosputtering indium-fin oxide (ITO) and zinc oxide (ZnO) targets has been investigated. The evolution from polycrystalline structure of an undoped ITO film to an amorphous-like ZnkIn2O3+k Structure obtained from ZnO-doped ITO films is found to be responsible for the marked improvement in the electrical properties. A low surface roughness is also achieved from this amorphous structure. However, both electrical property and surface uniformity begin to degrade with increasing rf cosputtering power on the ZnO target that corresponds to a high atomic ratio of Zn/(Zn+In). The degradation mechanism is attributed to the appearance of a microcrystalline ZnO structure that is detrimental to the film resistivity. Furthermore, optical band gap calculated from the absorption edge of such cosputtered films also decreases with increasing ZnO impurities.