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Surface Oxidation and Reduction of CuO and Cu 2 O Studied Using XPS and XAES
Author(s) -
Poulston S.,
Parlett P. M.,
Stone P.,
Bowker M.
Publication year - 1996
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/(sici)1096-9918(199611)24:12<811::aid-sia191>3.0.co;2-z
Subject(s) - x ray photoelectron spectroscopy , annealing (glass) , auger electron spectroscopy , hydrogen , analytical chemistry (journal) , monolayer , ultra high vacuum , materials science , chemistry , metallurgy , chemical engineering , nanotechnology , engineering , physics , organic chemistry , chromatography , nuclear physics
Abstract Using XPS and x‐ray‐excited Auger electron spectroscopy (XAES), we have studied the variation in surface composition of CuO and Cu 2 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 Cu 2 O at the surface whilst vacuum annealing of Cu 2 O produces a thin (possibly one monolayer) film of Cu metal. Both bulk Cu 2 O and the thick Cu 2 O film generated from vacuum‐annealed CuO were oxidized to CuO by heating at 800 K in 1×10 ‐4 mbar O 2 , the original surface being regenerated with vacuum annealing at the same temperature. Both CuO and Cu 2 O are reduced to metal at the surface by heating in 1×10 ‐4 mbar hydrogen at 400 K. 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 2 O were both reoxidized on vacuum annealing, demonstrating the diffusion of lattice oxygen to the surface.