Reactive sputter deposition of WO₃ films by using two deposition methods

Tungsten-trioxide (WO₃) films were deposited using two types of sputtering systems: a planar magnetron sputtering system and a facing-target sputtering (FTS) system. The structure and gasochromic properties of the resulting films were compared, and film uniformity and gasochromic properties were found to be significantly improved when using FTS because the incidence of high-energy negative oxygen ions on the substrate during sputtering was significantly suppressed. The authors confirmed that the deposition rate of WO₃ films increased by hundreds of times with an increase of the sputtering voltage from 500 to 800 V in the FTS system, and a deposition rate above 100 nm/min was easily achieved. The authors clarified that the deposition rate of the WO₃ film strongly depends on the sputtering voltage under the condition of a constant sputtering current.