Characterization of sputter-deposited WO3 and CeO2-x-TiO2 thin films for electrochromic applications

DC magnetron sputter-deposited WO3 and CeO2-x-TiO2 thin films are investigated for electrochromic applications. Emphasis lies both on material characterization and electrochemical measurements. Various surface analytical techniques are used to obtain detailed information on the relation between thin film properties and charge density as the main electrochemical parameter. Parameters in electrochemical testing, such as the applied voltage, the amount of water in the liquid electrolyte and conditions of sample storage, are varied to clarify their influence on experimental results. A comparison of the charge density measured electrochemically and that calculated from wet chemical analysis of etched samples reveals a significant share of proton intercalation, which falsifies the measured values. Furthermore, this paper contributes to discussions of the intercalation mechanism in CeO2-x-TiO2 with regard to material properties, particularly the binding state (XPS) and thin film density (GI-XRS). (C) 2001 Elsevier Science B.V. All rights reserved.