Atomic Layer Epitaxy of Tungsten Oxide Films Using Oxyfluorides as Metal Precursors

Atomic layer epitaxy (ALE) of from and has been studied. These precursors were found to yield very low deposition rates. This was attributed to a poor adsorption of on the oxide surface. Attempts to increase the adsorption of the metal source by in situ generation of tungsten subfluorides were unsuccessful due to severe etching problems. Our results, however, showed that different compounds are good candidates for ALE of . The oxyfluorides were generated in situ by etching of tungsten oxide lumps with at temperatures up to 600°C. No analysis of the generated precursors was carried out, but thermodynamic calculations suggest that the main etch products should be and . An ALE process based on the in situ generated oxyfluorides and as precursors was found to yield monoclinic films at substrate temperatures as low as 200°C. The deposition rate at this temperature was about 0.8 Å/deposition cycle. The films deposited at 200°C contained small amounts (<2 atom %) of fluorine. © 1999 The Electrochemical Society. All rights reserved.