Electrochromic property dependent on oxygen gas flow rate and films thickness of sputtered WO3 films

Abstract

Tungsten oxide films (WO3) were deposited on ITO/glass substrates with tungsten target in UHV by d.c. reactive magnetron sputtering. The WO3 films were deposited at various O2 flow rates from 5 to 20 sccm and various film thicknesses from 50 to 500 nm at 10 mTorr operating pressure as controlled by pressure control gate valve. The influence of O2 flow rate on structural, optical and electrochromic properties of WO3 films were investigated. All the WO3 films were found amorphous which were indicated by X-ray diffraction (XRD). The deposition rate of WO3 films was decreased with increasing oxygen flow rate. The optical constants and transmission spectra of WO3 films were determined by spectroscopic ellipsometry (SE) and UV-Vis spectrophotometry, respectively. The electrochromic property of WO3 films was performed by cyclic voltametry measurement. The transmission change between colored and bleached states of WO3 films for oxygen flow rate of 5 sccm showed excellent electrochromic property which was strongly dependent on the film thickness. © 2010 Published by Elsevier Ltd.