Preparation of WO3 Thin Films for Electrochromic Display by Plasma Process

Tungsten oxide (WOx) thin film, which is well known as an electrochromic display, was deposited on the ITO film coated flexible substrates using the RF magnetron sputtering method. Phenomena of processing plasmas, the film quality and the electrochromic properties of deposited WO3 thin film have been studied as parameters of a gas pressure and gas mixture. Experimental results suggest that deposited WOx thin films at gas pressure of 10 Pa were amorphous structure independent of a gas mixture. XPS analyses suggest that the amorphous type WOx(x=2.43) film can be deposited at the gas flow ratio of O2:Ar=5:5, total gas pressure of 10Pa and RF power of 50W. The color of electrochromic display prepared using the deposited WOx film change from transparent to blue by applying a DC voltage, which means that the deposited film under the condition worked as electrochromic display.