Effects of film density on electrochromic tungsten oxide thin films deposited by reactive dc-pulsed magnetron sputtering

The correlation between the electrochromic performance and the film density of the tungsten oxide thin films sputtered by reactive dc-pulsed magnetron sputtering with varying working pressure was investigated. It is found that the optical modulation and coloration efficiency of films are strongly affected by the amount of tungsten oxide present in the film. The coloration kinetic is also found to be sensitive to the film density, with the maximum value of 3.48 x 10(-10) cm(2)/s for the porous film deposited at higher pressure. X-ray diffraction and TEM showed that the films were amorphous. By using spectroscopic ellipsometer to anaylsis the surface roughness and refractive index of the sputtered films, we found that the film at higher working pressure was rough and lower density, which offered fast electrochromic response. (C) 2010 Elsevier B.V. All rights reserved.