Physical and electrochemichromic properties of rf sputtered tungsten oxide films

The physical and electrochemical coloration characteristics of tungsten oxide films rf sputtered from a compressed powder WO3 target have been investigated. Oxide films with 3600–9800 A thickness were deposited on substrates maintained at 200 °C at a total pressure of 0.5–8×10−2 Torr in Ar gas or an Ar‐0.5‐50% O2 gas mixture. Physical properties of the oxide films depend on the oxygen concentration and total pressure of the sputtering atmosphere. The films prepared at 4×10−2 Torr in a mixture of Ar‐0.5‐20% O2 gas are transparent and amorphous, and their electrical resistivity ranges from 6.5×108 to 2.4×1011 Ω cm. The films prepared at pressures between 4 and 6×10−2 Torr in an Ar‐50% O2 gas mixture are transparent, and have crystallites with a composition of WO3. The films prepared at 1×10−2 Torr in a mixture of Ar‐0.5 and 5.0% O2 gas are blue colored and transparent, respectively, and these films are crystallites with a composition of WO2.83. Electrochemichromic properties of the rf sputtered tungsten oxi...