Surface Oxidation and Reduction of CuO and Cu2O Studied Using XPS and XAES

✍ Scribed by Poulston, S.; Parlett, P. M.; Stone, P.; Bowker, M.

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 1018 KB
• Volume: 24
• Category: Article
• ISSN: 0142-2421
• DOI: 10.1002/(sici)1096-9918(199611)24:12<811::aid-sia191>3.0.co;2-z

✦ Synopsis

Using XPS and x-ray-excited Auger electron spectroscopy (XAES), we have studied the variation in surface composition of CUO and Cu,O with a variety of high-vacuum treatments, including vacuum annealing, oxidation and hydrogen reduction. Prolonged annealing of CuO results in the formation of a thick layer of Cn,O at the surface whilst vacuum annealing of Cu,O produces a thin (possibly one monolayer) film of Cu metal. Both bulk Cu,O and the thick Cu,O film generated from vacuum-annealed CuO were oxidized to CuO by heating at 800 K in 1 x lo-' mbar 0, , the original surface being regenerated with vacuum annealing at the same temperature. Both CuO and Cu,O are reduced to metal at the surface by heating in 1 x mbar hydrogen at 400 I ( . In the case of CuO, the extent of reduction varies with the thermal history of the sample, with prolonged vacuum annealing producing a more reducible surface. Hydrogen-reduced CuO and Cu,O were both reoxidized on vacuum annealing, demonstrating the diffusion of lattice oxygen to the surface.