Preparation of WO3 Films by CVD and their Application in Electrochromic Devices

A study on chemical vapor deposition(CVD) of WO3 and the electrochromic properties of the CVD WO3 films have been carried out. The crystalinity, purity, and growth rate of the films depending on substrate temperatures are investigated. The highest growth rate is 8 mu m/min at the substrate temperatures above 300 degrees C and the estimated activation energy for overall film growth is about 45.9 kJ/mol at the temperatures of 225 similar to 275 degrees C, where the CVD process is controlled by a surface reaction kinetics. The films grown below 275 degrees C are amorphous, while those deposited above 300 degrees C are crystalline. The effects of thickness and deposition temperature of the WO3 films on electrochromic activity are also investigated. The coloration efficiency of the films increases with increase in film thickness and decrease in deposition temperature.