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Acid-Site Characterization of Water-Oxidized Alumina Films by Near-Edge X-Ray Absorption and Soft X-Ray Photoemission

Published online by Cambridge University Press:  15 February 2011

P. J. O'hagan ,
R. P. Merrill ,
T. N. Rhodin ,
S. C. Woronick ,
N. D. Shinn ,
G. L. Woolery  and
A. W. Chester
P. J. O'hagan
Affiliation:
Cornell University, Ithaca, NY, 14850
R. P. Merrill
Affiliation:
Cornell University, Ithaca, NY, 14850
T. N. Rhodin
Affiliation:
Cornell University, Ithaca, NY, 14850
S. C. Woronick
Affiliation:
Cornell University, Ithaca, NY, 14850
N. D. Shinn
Affiliation:
Sandia National Laboratories, Albuquerque, NM, 87185
G. L. Woolery
Affiliation:
Mobil Research and Development Corporation, Paulsboro, NJ, 08066
A. W. Chester
Affiliation:
Mobil Research and Development Corporation, Paulsboro, NJ, 08066
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Abstract

Hydroxylated alumina films have been synthesized by water oxidation of single crystal Al(110) surfaces. Thermal dehydroxylation results in anion vacancies which produce an Al(3s) defect state 3.5 eV below the conduction band edge. The defect-DOS exhibits a maximum for oxides heated to 648±25 K, which is just where the materials exhibit maximum Lewis acidity with respect to C2H4 Adsorbed C2H4 produces thermally reactive C2 species which interact covalently with the defect-DOS and nonbonding O(2p) states from the top of the valence band. C(1s) binding energies suggest significant charge transfer which is consistent with a carbenium ion. Ni deposits behave similarly but transfer charge directly to Al species and do not interact with O atoms at the defect site. The defect-DOS is regenerated when the C2 species decomposes or when Ni migrates thermally through the oxide layer.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 375: Symposia AA – Applications of Synchrotron Radiation Techniques to Materials Science , 1994 , 229
Copyright
Copyright © Materials Research Society 1995

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