Influence of annealing times for W films on the structure and electrochromic properties of anodized WO\(_{3}\) films

WO3 films were prepared from annealed W films by anodization and annealing at 450℃ for 1 h. The sputtered W films were annealed before anodization at different times for 0.5 h to 2 h, followed by immediate removal from the furnace (quenching) or slow cooling (cool-down). The WO3 films exhibited a different preferred orientation between the (200) and (222) planes. The morphological structure of the WO3 films depended on the annealing time and cooling features of the W films. The WO3 films for the cool-down condition had smaller grains and more pores than the quenching condition. The WO3 films prepared from annealed W for 1.5 h with cool-down showed maximum transmittance change of 48.20% with the diffusion coefficient of 3.533 x 10-7 cm2∙s‒1. The quenching condition can be improved durability of WO3 films. Therefore, annealing time and cooling conditions can be used to design film properties that are suitable for the electrochromic application.