Effects of deposition parameters on RF-sputtered WO₃ thin films

In the absence of additional oxygen, thin films of tungsten (VI) oxide (WO₃) were prepared on indium-doped tin oxide conductive glass substrates by radio-frequency (RF) magnetron sputtering. The effects of sputtering power, working air pressure, substrate bias voltage and substrate temperature on the surface morphology, microstructure, optical properties and electrochromic (EC) performance of the films were systematically investigated. The research shows that a sputtering power of 80–100 W can ensure a moderate deposition rate of ∼10⁻² nm/s and help obtain non-dense films. Similarly, a working air pressure of 1.0 Pa also leads to the deposition of loose films, which is beneficial for the improvement of the optical transmittance and EC performance of tungsten (VI) oxide thin films. The applied substrate bias has little effect on the optical properties, but it will degrade the coloring and/or bleaching efficiency of tungsten (VI) oxide thin films and greatly reduce their optical modulation. When the substrate temperature rises to 600°C, the film begins to crystallize and exhibits a rod-patterned porous structure, which leads to a small increase in the optical modulation.