Sputtering Deposition Parameters and Their Interactions in Amorphous Tungsten Oxide Thin Film as Electrochromic Electrode

Amorphous tungsten oxide (a-WO3) thin films were deposited as electrochromic electrodes on ITO coated glass substrates via reactive DC magnetron sputtering from metallic tungsten target. A two-level full-factorial design-of-experiment (DoE) was carried out with the following variables: 1) sputter target power density, 2) total pressure, 3) oxygen to argon flow ratio and 4) deposition time. Characterizations via lithium intercalation in potentiostatic mode were conducted in a wet electrochemical cell. Our work shows that parameters interaction should be considered in optimizing WO3 thin film for electrochromic applications. Work based on a factorial design reduces the number of experiments and allows reaching near-optimized region with small amount of effort.