Optimizing indium tin oxide thin films with bipolar d.c.-pulsed magnetron sputtering for electrochromic device applications

In this paper, indium tin oxide (ITO) films were prepared by bipolar d.c.-pulsed magnetron sputtering in a mixture of argon and oxygen onto unheated glass substrates. A target of ITO with 10 weight percent (wt %) tin was used. The influences of ratios of t−on/t+on (negative pulse-on time/positive pulse-on time) on the optical, electrical, and structural properties of ITO films have been investigated. The correlations between the deposition parameters and the film properties were discussed. An optimal condition based on reactive bipolar d.c.-pulsed sputtering for obtaining high transmittance, low resistivity, and low surface roughness of ITO films with high deposition rate is suggested. Then, ITO films grown at room temperature by bipolar d.c.-pulsed sputtering were used to form electrochromic devices of WO3. Better electrochromic performances were found in comparison to those measured with commercially available ITO films on glass substrates.