Effect of Oxygen Flow Rate on Electrical and Optical Properties of ATO Thin Films Prepared by RF Magnetron Sputtering

Transparent conducting antimony doped tin oxide (ATO) films were sputtered on quartz glass substrates by RF magnetron sputtering at an oxygen flow rate ranging from 0 to 15 sccm. The films were prepared at room temperature and annealed for 15 min in air atmospheres at a temperature of 450 °C. The effect of oxygen flow rate has been investigated by comparing eletrical and optical properties of ATO films. The results suggest that, oxygen flow rate has a great impact on Sb5+/Sb3+ ratio and lattice structure integrity, which finally affects the transmittance and electrical resistivity. With the increase of oxygen flow rate, the grain size is enlarged, which leads to a higher average optical transmittance. On the other hand, with oxygen flow rate increasing, the Sb5+/Sb3+ ratio first increases and then decreases sharply when the oxygen flow rate exceeds 5 sccm. The increase of Sb5+/Sb3+ ratio results in the increase of carrier concentration and finally contributes to a decrease of electrical resistivity. The optimal resistivity is 8.9×10-2 Ω·cm and the average transmittance is about 95% at an oxygen flow rate of 5 sccm.