Atmospheric pressure chemical vapor deposition of electrochromic tungsten oxide films

Tungsten oxide, WOx, is a coloring layer commonly used in electrochromic wi ndows and displays. Successful commercialization of these devices will requ ire the deposition of WO, layers with extremely uniform thickness and mater ial properties over large areas at high speeds and low cost. We present a n ew atmospheric pressure chemical vapor deposition process that should be ab le to meet these goals. New liquid tungsten precursors have been found to h ave properties suitable for this application: sufficient volatility, reacti vity to oxygen at substrate temperatures of 200-300 degreesC, lack of react ivity to air and water at room temperature, and low viscosity (7 centiPoise at 40 degreesC). The precursors are tungsten pentacarbonyl 1-methylbutylis onitrile and tungsten pentacarbonyl n-pentylisonitrile, C5H11NCW(CO)(5). Th ese liquid precursors can be synthesized readily from commercially availabl e reactants. Data on the composition and structure of the tungsten oxide fi lms are presented, along with spectroscopic characterization of the films i n transparent (oxidized) and colored (reduced) states. (C) 2001 Elsevier Sc ience B.V. All rights reserved.