Atmospheric pressure chemical vapor deposition of electrochromic tungsten oxide films

Abstract

Tungsten oxide, WO x , is a coloring layer commonly used in electrochromic windows and displays. Successful commercialization of these devices will require the deposition of WO x layers with extremely uniform thickness and material properties over large areas at high speeds and low cost. We present a new atmospheric pressure chemical vapor deposition process that should be able to meet these goals. New liquid tungsten precursors have been found to have properties suitable for this application: sufficient volatility, reactivity to oxygen at substrate temperatures of 200–300°C, lack of reactivity to air and water at room temperature, and low viscosity (7 centiPoise at 40°C). The precursors are tungsten pentacarbonyl 1-methylbutylisonitrile and tungsten pentacarbonyl n-pentylisonitrile, C 5H 11NCW(CO) 5. These liquid precursors can be synthesized readily from commercially available reactants. Data on the composition and structure of the tungsten oxide films are presented, along with spectroscopic characterization of the films in transparent (oxidized) and colored (reduced) states.