Grain size control in ITO targets and its effect on electrical and optical properties of deposited ITO films

摘要

Tin-doped indium oxide (ITO) ceramic targets with three types of grain size (＜10, 10-20 and ＞20 μm) were prepared by controlling sintering process. It is found that all targets show polycrystalline structure and a rapid heating and short holding time contributes to refining grain size. The ITO films were deposited using these ITO targets with three types of grain sizes under dc and rf mode. The effects of grain size on the structural, electrical and optical properties of the as-deposited films were systematically investigated. The results indicate that all ITO films are the (222) preferred orientation, and the surface grain morphologies are round (dc mode) and triangular (rf mode). The sheet resistance, transmittance and uniformity of the ITO films are significantly impacted by the grain size. The small grain size (＜10 μm) contributes to improving the uniformity of electrical and optical properties. The optimal uniformity of sheet resistance under dc and rf mode is about 13 and 10 %, respectively.