Effects of oxygen flow on the properties of indium tin oxide films

Indium tin oxide (ITO) films (In2O3–SnO2) were deposited onto glass at different oxygen flow rates by RF magnetron sputtering method. Transmittance in visible light and an energy band gap were measured by ultraviolet spectrophotometer. Sheet resistance was measured by a four-point probe system. The thickness and complex refractive index of films were measured by spectroscopic ellipsometry. The component and the surface electron states of the ITO films were studied by XPS. The results indicated that the deposited ratio and refractive indexes of films were obviously affected by O2 flow rate (fO2fO2). The transmittance in visible light was beyond 80% (including glass substrate) with 60 nm film thickness and 9 sccm fO2fO2. The transmittance and sheet resistance could be improved by heat treatment. XPS investigation showed that the photoelectrolytic properties could be deteriorated by the sub-oxides which could be reduced by fO2fO2.